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Prt~res.~ io .'~uclear Energy. Vol. 23. No. I. pp 35-8(). lqqO. 014q-tt~70~) Stb ~N) + 511
Printed in Great Brltatn. All rights rcscr',ed. © I~) Pcrgam~n Pro,.', pie
A REVIEW OF THE APPLICATION OF CHEMICAL
DECONTAMINATION TECHNOLOGY IN THE UNITED STATES
C. J. WOOD
Electric Power Research Institute, 3412 Hillview Avenue, Palo Alto, CA 94304, U.S.A.
(Received 2 January 1990)
Abstract - This review provides information on the chemical
decontamination of nuclear power plants. An overview of the current
status of the technology is given, including a brief description of
commerclally-available processes. BWR recirculatlon piping and
steam generator decontaminations are described, with a comparison of the
two types of operation. Corrosion data, methods of reducing
recontamination rates, and waste issues are discussed. Future
developments, including full-system decontaminations, are reviewed.
I. INTRODUCTION
The commercial application of chemical decontamination technology has expanded
significantly in recent years at U.S. nuclear power plants. From initial applications to
components and small subsystems in the early eighties, to the current examination of full
system decontamination, the entire technology has become much more sophisticated. During
this period, dilute chemical decontamination has been responsible for avoiding a
substantial radiation exposure to personnel. Most of these benefits have occurred as s
result of decontaminations prior to in-situ inspection, maintenance or repair of systems
and components, primarily the reactor water recirculation system (RNR) and reactor water
clean-up systems (RWCU) in a BWR and the steam generator channel heads of a PWR.
Of the decontamination campaigns to date, 75% were performed in BNR systems such as
recirculstion piping and reactor water clean up components. The remaining 25% involve PWR
parts, mainly pumps and steam generator channel heads. There are sound financial reasons
for this disparity - the cost benefit studies described in Section 7 show that generally
the cost involved in avoiding each man-rem is less for BNR situations - but in many cases
PNR decontamination can be highly cost effective. However, the penetration of the
technology has been uneven. Some utilities regard decontamination as a routine activity to
be performed at almost every refueling outage at their BNR plants. Other utilities - the
majority - find it necessary to carry out major evaluations before attempting a
decontamination.
This review utilizes information presented at recent international conferences,
particularly the 1984 American Nuclear Society Executive Conference on Decontamination (1),
the 1986 British Nuclear Energy Society Water Chemistry Conference (2), and the 1988 Japan
Atomic Industrial Forum Conference (3), and five seminars (two on P~s, three on BNRs)
covering utility experience with decontamination (4-8).
Decontamination campaigns on the primary systems of commercial LNRs using dilute
chemicals began in the early '80's. These early projects (through 1984) involved the use
of CAN-DECON solutions (origlnally developed for CANDU reactors in Canada), which are
mixtures of organic acids, oxalic Included, and EDTA. Decontamination factors (DFs)* were
satisfactory, and CAN-DECON along with CITROX, a mixture of oxalic and citric acids, was
used successfully at several plants. In late 1984, laboratory evidence emerged to indicate
*The decontamination factor is the ratio of radiation field before the decontamination to
the field after decontamination.
35

5h C.J. ~V()()O
that solutions containing oxalic acid under some conditions induce fntergranular attack on
sensitized type 304 stainless steel. A cautious period followed, when sufficient corrosion
evaluation was conducted to understand and avoid conditions which could potentially cause a
problem. The LOHI process, which does not contain oxalic acid, was first used on a BWR in
1984, and was selected by most BWR utilities carrying out decontaminations from 1985 on,
Including Monticello and Quad Cities BWRs in 1989. Aside from the encouraging corrosion
data, LOHI offered at least comparable DFs and required short application times. CITROX
has continued to be used at the Brunswick BWR. Meanwhile a new process, CANDEREH, which
does not contain oxalic acid, was developed from CAN-DECON, and is now available and was
recently used on a heat exchanger at Indian Point 2 PWR and on the steam generator channel
heads at Beaver Valley I PWR. CANDEREM and LOMI are given equal prominence at this time in
the development of corrosion data necessary for full system decontamination in PWRs.
2. TECHNICAL BACKGROUND
2.1 Concentrated reagents
The 1984 de contamlnatlon of the complete primary system (with the fuel removed) of the
Dresden-I BWR, using the NS-I process, was the only recent U.S. application of concentrated
chemical reagents. This decontamination was unusual in several respects. Dresden-l, an
early BWR, was shutdown in 1978 and Is unlikely to operate again. The decontamination was
originally scheduled for 1980, but environmental impact and safety issues were mainly
responsible for a delay of four years.
Decontamination factors exceeded 11.3, and over 750 curies of activity was removed. The
total activity removed was extremely close to the 1979 calculation of total activity in the
system, when decay was taken Into account. The use of an organic inhibitor to control
corrosion in concentrated reagents tended to slow down the cleanup process, and the return
of the total organic carbon to reactor water speclffcatlon took considerable tlme.
The detailed report of this project (9) reveals both the strengths and the problems of
concentrated (or "hard") decontamlnatlon--processes. High removal of activity was achieved,
but waste disposal was a major difficulty, and concern about corrosion effects necessitated
a large and expensive materials qualification program. Recently-developed dilute
decontamination reagents ("soft" processes) achieve as much activity removal, with greatly
reduced concerns about corrosion damage and waste disposal. With the current Industry
emphasls on avoiding corrosion and reducing radwaste volumes, it seems unlikely that
concentrated processes will be used on operating plants again, although localized
applications on components such as pumps will continue. This review focuses on system and
subsystem decontamination dilute chemical processes.
2.2 Dilut e reasents - BWR
There are two types of dilute chemical reagents. In the early '80's, the organic acld
reagents based on citric and oxalic acids (e.g., CITROX), using a chelating agent such as
EDTA to retain dissolved corrosion products In solution (e.g., CAN-DECON), were used for
the majority of plant applications. Since 1985, however, the low oxldatlon-state metal ion
(LOMI) process has been the most widely used process In the United States. Table 2-I lists
primary coolant system decontamlnatlons (IO).
The organic acid reagents dissolve oxides by simple acidic dissolution
8H + + Fe304 ~ Fe 2+ + 2Fe 3+ + 4H20 (I)
acid oxide metal ions
in solution
and reductlve dissolution:
8H + + 2e- + Fe304 ÷ 3Fe 2+ + 4H20 (Most likely the major
pathway for oxide
acld reducing oxide metal ions destabillzatlon)
agent in solution
The radioactive Impurities, such as Co-60, Co-58, Fe-59, Mn-54, are released at the same
time. A corrosion inhfbltor may be necessary for some applications, depending on the
materials In the system, the process temperature, duration, and reagent strength. Because
3+
Fe solubility is small, a chelating agent needs to be present at the site of dissolution
in order to retain the iron in solution.
(2)

Chemical decontamination technology
Table I. Decontamination factors at recent BNR applications
DECONTAMINATION FACTORS AT
RECENT BWR APPLICATIONS*
Plant & System Solvent i DF Curies
Oyster Creek:
RRS LOMI/NP/LOMI 10.5 55.3
Quad Cities 2:
RRS
RWCU
Dresden 2:
RRS
RWCU
Brunswick 1 :
RRS-Loop A
RRS-Loop B
Peach Bottom 3:
RRS "B" Pump
RWCU
RRS
J. A. FitzPatrick:
RHR X-Ties
RRS
LOMI/NP/LOMI
(LOMI on Suction)
LOMI/LOMI
LOMI/LOMI
(LOMI on Suction)
LOMI/LOMI
Citrox/AP/Citrox-
Citrox/AP/Citrox
LOMI/NP/LOMI
LOMI/NP/LOMI
LOMI/NP/LOMI
LOMI/NP/LOMI
LOMI/NP/LOMI
*Douglas M. Vandergriff in Reference #7
4.4
2.5
9.8
2.5
3.6
8.4
5.2
6.7
15.2
3.9
42.4
97
13.0
56.3
13.0
23
Total
The LOMI decontamination reagents ere more strongly reducing end do not require a
corrosion inhibitor. The LOMI reagent currently used is vanadous plcolinate/formate in
which the complexed (plcolinate) vanadous ions (V z+) reduce the oxidation state of the iron
in the oxide, enabllng it to be rapidly dissolved in plcolinic acid, which is also a
complexlug agent.
7.6
13.1
36.8
0.2
61.4
Fe III (oxide) + V II (pic) 3- ÷ Fe II + VIIIplc)3 (3)
Both types of chemical decontamination systems may require an oxidizing pretreatment for
situations where high-chromium oxides are present. Alkaline and/or acid potassium
permanganate is used for this purpose, dissolving chromium oxides by oxidizing them to
soluble chromate:
Cr203 +
chromium
30x + +
oxidizing
Cr 6+ +
soluble
3e- + residuals (4)
oxide agent chromate
3"7

38 C.J. Wo~l~
Good decontamination factors are generally obtained for BNR rectrculation systems wlth
either a single or double LOMI application. In low flow areas, a second LOMI step is
sometimes required to deal with excessive oxide burden, because catalytic decomposition of
reagent occurs before it contacts surface oxides. Thus the need for a second step can be
minimized by improving reagent circulation (e.g., by use of spray devices for low flow
areas). In most cases, the addition of an oxidizing step, typically nitric acld/potasslum
permanganate (NP) has given only a small further reduction in residual fields. However,
for some components, such as the reclrculation pumps, use of NP has proved beneficial.
When a permanganate step is used, oxalic acid Is added stolchlometrlcally to dissolve
manganese dioxide (MnO2). Adding insufficient oxalic acid will cause some of the
subsequent vanadous reagent to be used up in dissolving MnO 2. Adding excessive oxalic acid
will lead to the presence of oxalic acid briefly in the system. To avoid possible
corrosion, this should be minimized by terminating the addition when samples taken of the
decontamination solution are clear.
The chemical reagents can be added in the solid form (as with CAN-DECON) or as liquids
(LOMI Is a mixture of dilute solutions of vanadous formate and plcollnlc acid). Depending
on the type of circuit to be decontaminated, feed-and-bleed or fill-and-draln methods are
used. In most cases, the radioactive waste Is removed on Ion-exchange resin.
Two different flow paths have been used in recent reclrculatlon piping
decontaminations. Use of the annulus between the shroud surrounding the core internals and
the pressure vessel provides a convenient flow path (Fig. I), allowing effective reagent
circulation. However, concern about corrosion damage to in-core materials has resulted In
restricting the reagents to out-of-core regions for a number of plant applications. In one
case, the piping was cut and capped before decontamination, which can be costly in both
time and radiation exposure. In other plants, fluid levels were kept below the pressure
vessel inlet level, wlth raising and lowering of the liquid used to provide reagent
replenishment. This approach is operationally more complicated and less satisfactory than
permitting fluid flow through the annulus. Flow paths are discussed further in Section 3.
A general conclusion drawn from recent experience Is that differences in decontaminating
power of different solvents is less significant than the differences between the oxide
films in the various plants. Almost any decontamination factor can be achieved with any of
the processes, but longer application times may be required in some cases. LOHI proved to
be the quickest process currently in use. Decontamination factors (DF) or residual
radiation fields in designated areas are often specified in the decontamination contract.
A utility chooses between a lower DF with minimum waste and shorter downtime, or multl-step
applications giving higher DFs at higher cost. The choice depends on the magnitude of
special maintenance work to be done.
2.3 PWR applications
There have been fewer P~/R decontaminations, because of higher cost and because the
maximum incidence of repair work associated with secondary side corrosion problems
(denting, wastage, pitting and intergranular attack) had passed before sufficient
confidence was generated in dilute processes for PWR applications. The decontamination
reagents used for PWR applications are slmilar to those described above. In all cases, one
or more permanganate steps have been used to remove chromium from oxide films.*
In contrast to BWRs~ an oxidizing step is essential for PNR decontamination. Alkaline
oxidation yields higher DFs when applied in the presence of high NI alloyed materials,
whereas acidic oxidation is preferred (higher DFs) in the presence of stainless steel
surfaces. The recent CAN-DECON and LOMI applications have each used alkaline permanganate
(AP) followed by nitric acld/permanganate (NP) to achieve maximum chromium removal from
oxide films initially present on both Inconel and stainless steel. This pH switching
technique was developed by CEGB (11) to optimize DFs in channel heads.
Table 2 compares the DFs obtained on different materials with NP and AP preoxldatlon.
One important factor observed in all PWR decontaminations, and in the BWR applications
using permanganate, is the need to remove a loosely-adherent radioactive residue
particularly with the organic acid reagents. In some applications, high pressure
hydrolazlng has been used, whereas In other cases, repeated flushing proved adequate. If
*For a detailed discussion of surface oxide character in P~R and BWR environments see
Reference 11.

,4. O~¢I~NTAMiNATION Oi I
Mfql SYSTEM ~LY
Chemical decontamination technology 39
~*OTII: MilT¢l'llO ~IIA |l'lOWl AMIA Wll"flO 8Y IIQI,,IJTION
Fig. I. Flow paths for BWR decontamination
l. mlCCINTAIINATION TNI'~0~IGH
JIT M ANO SMNOIJOI
*RI~IUN| VlISM L A~e4ULUI
Table 2. Decontamination Factors for Reactor Specimens
In Different Reagent Combinations*
Process Stainless Steel Inconel 600
DF DF
NP/LOMI I0 - 20 1.5 - 3
AP/LOMI 2 - I0 2 - 4
NP/ClTROX (POD) 5 - i0 1.5 - 3
AP/CITROX 2 - 5 2 - 4
AP/NP/LOMI - 4 - 8
* Taken from Reference #11.

40 C, J. WOOD
not removed, these residues seem to contribute to rapid recontamlnatlon on return to
service. Several alternatives to permanganate are under development, including ozone,
parmanganlc acid, as in the KWU CORD process, potassium ferrate, and chromous LOMI
reagents. None of these reagents have been plant tested in the USA as yet, but some appear
to offer significant potential advantages compared to permanganate.
3. LWR DECONTAMINATION APPLICATION TECHNIQUES
3.1 BWR reactor water recelculation system (RWR) applications
The majority of RWR systems In U.S. BWRs consist of two piping loops, each containing a
high flow centrifugal pump complete wlth suction and discharge isolation valves and
interconnecting piping. The piping on the suction side of the pump runs vertically from
the reactor vessel near the bottom of the annulus. On the discharge slde, the piping
connects to a header above the pump from which five discharge risers extend vertically
upward to where they penetrate the reactor vessel and rise approximately another ten
feet. Once inside the vessel their designation changes and they are called Jet pump risers
and are considered part of the Jet pump assembly rather than the RWR system. Despite the
designation change, each riser is a continuous pipe which is used to contain
decontamination fluid during the application.
Some RWR systems contain a cross-tie line which interconnects the two loops at the
discharge headers. This llne normally contains two isolation valves.
Two different techniques have been employed to decontaminate this system--one and two
phase applications. Due to the design of the RWR system it is not possible for the reagent
to wet all of its various parts in a single step and maintain circulation (as opposed to
fill, soak, drain techniques), unless some form of modification is performed. Thus, single
phase applications are normally performed at plants that are planning a piping replacement
and are prepared to modify the system in order to improve reagent access. Two phase
applications are normally performed on an unmodified RWR system. These techniques are
described in more detail in Sections 3.1.1 and 3.1.2.
The decontamination equipment is common to both types of applications. In each case,
the temporary equipment used has performed all of the process functions required to
complete the decontamination. This consists of circulating and heating up the fluid,
injecting chemicals, reversing flow directions, sampling, monitoring process parameters,
controlling fluid levels and removing the dissolved activity and chemicals on Ion exchange
resins. Only minor variations In the equipment have been required to accommodate the
differences from one chemical decontamination process to another.
Flexible, high pressure, reinforced rubber hoses are used to connect the equipment to
the system or component to be decontaminated. Occasionally the entire system has been
hard-plped, but experience with the rubber hoses has been excellent, and this is now the
preferred option. Hoses typically in the range of 2" to 4" diameter are typically used.
3.1.1 Two Phase RWR Decontaminations. This is the most common approach to RWR
decontamination. It is most effective when extensive inspection or maintenance work,
rather than modifications, are scheduled for the system. The decontamination is performed
In two phases, a discharge side phase and a suction side phase. It can be used whether or
not the RWR system contains a cross-tle llne connecting the discharge headers of each loop,
and whether or not the lower portion of the annulus is to be included in the flowpath.
As shown in Fig. 2, the temporary decontamination equipment is connected to the RWR
system at the suction of each RWR pump. Flanged connections are available for Just such
work on virtually all U.S. BWRs. The equipment is normally located Just outside the
drywell in the vicinity of the equipment access hatch. It is placed and shielded to
minimize radiation exposure to both contractor and plant staff during the application.
To commence the discharge side decontamination, the pump isolation valves on the suction
side are closed, those on the discharge side and on the cross-tie header are opened, and
the discharge piping is filled to a predetermined level of fluid (Just about half way up
each of the ten discharge risers). Flow is established through the discharge half of the
system from the temporary equipment into one loop via the decon flange, through the RWR
pump bowl, and up the discharge piping into the header. The fluid passes into the second
loop via the cross-tie llne and back down the discharge piping, through the pump and back
to the temporary equipment. By adjusting the valve lineup on the decon equipment the
direction of flow can be reversed through the discharge loops.

Chemical de¢ontaminamm technology J,l
.%
Fig. 2. BWR reactor water recirculation system single
phase decontamination fIowpath
In order to expose the ten risers to the solvent, one of the two isolation valves in the
cross-tle llne Is throttled. This provides enough pressure drop across the cross-tle llne
so that the level of fluid in the five upstream risers Is raised to a predetermined
elevation above their penetration Into the vessel (usually two to three feet). This will
improve the decontamination factors at the riser safe ends. on the down stream side, fluid
levels will drop to the elevation of the header completely emptying the risers. Changing
the flow direction will reverse the fluid elevations in each loop. It is important to
initiate regular reversals (every half hour or so) as early as possible in the operating
sequence in order to ensure that the temperature in the upper portions of the risers is as
high as can be reasonably achieved.
Once operating temperature has been reached, reagent is injected through the temporary
equipment into the system. Circulation in alternate directions is continued throughout the
decontamination. Once it has been determined that the application is complete, the heaters
are shut off and cooldowu commences. The reagent and dissolved activity are removed by
relying in the ton exchange columns contained In the temporary equipment. During this
period, it is again very important to ensure that fluid levels are maintained in the
risers. In fact, slightly higher levels should be maintained to ensure that all exposed
riser piping is flushed with reagent-free fluid near the end of the cleanup sequence.
If there ts no cross-tie line in the system and an alternative path cannot be utilized
to interconnect the discharge loops, a "sloshing" technique can be used. This can be
achieved by filling the discharge loops to slightly more than one half of the total
discharge side volume. "Circulation" is achieved by filling ohe loop from the other,
holding fluid elevation in the "full" loop for a short period of time, and then reversing
the operation. Most other aspects of the application are identical, except perhaps, for
the concentration of reagent and radioactivity in solution. For non-regenerative
processes, the working technique results in higher levels of both due to the smaller fluid
inventory. It is important to ensure that during the preparative stages, adequate
attention is paid to ~hese items in order to avoid problems with chemical precipitation and
higher than normal personnel exposure.
On completion of the discharge slde, the suction piping can be decontaminated merely by
switching over the position of the RWI~ pump isolation valves and filling the system to the
predetermined fluid levels. To minimize the impact on critical path, the majority of the
warm fluid from the discharge side can be transferred during the valve position
changeover. To maximize the decontamination factors, the fluid should be Just slightly
above the top of the suction connection to the reactor vessel, including the bottom few
feet of the annulus in the flowpath.

42 C.J. WOOD
With the suction piping filled, circulation and heatup proceed in the same manner as for
the discharge side. For this phase, flow enters the system in the same location but
travels up the suction piping of the first loop, into and around the annulus and back down
the suction llne of the second loop. Unlike the discharge side, all parts of this
circulating loop are exposed to full system flow. Chemical injection, process monitoring,
and subsequent cleanup are all controlled in the same manner as the discharge side. Flow
reversals, although not as important, are still performed at regular intervals.
If the annulus cannot be included in the flow path, the approach for performing the
suction decontamination is almost identical to that described for the discharge side
without a cross-tle llne. A "sloshing" technique is used to move fluid from one loop to
the other and hold it at the maximum elevation for a short period of time. One additional
problem with the suction side is the accuracy of the level control. If the fluid cannot
enter the annulus it is important that the equipment be able to control the maximum fluid
levels very accurately. Otherwise, much of the benefit of the application can be lost
(from levels which are too low) or problems "can be encountered with fluid ~n the annulus
(from levels which are too high).
3.1.2 Single Phase RWR Decontaminations For decontaminations that are coincident with
major modifications or complete piping replacements, a single phase application may be more
appropriate. In order to accomplish this, however, additional connection points must be
made available. A number of potential connection points is possible depending upon the
specific needs and concerns of the individual utility. Usually twelve additional
connections are necessary. One is located on each of the ten discharge risers as close to
the penetration into the vessel as possible. The remaining two are located at the suction
nozzles. With these additional connections both the suction and discharge sides can be
decontaminated simultaneously and fresh reagent supplied to virtually all portions of the
system. A typical flowpath is shown in Fig. 3.
The major advantages of this approach are the potential for critical path savings since
only one heatup, injection, circulation, and cleanup step is required and the improved DFs
achieved in the risers from direct injection of fresh reagents. This must, however, be
balanced against the additional effort, time, expense and radiation exposure required to
prepare for this approach.
3.2 PWR steam generator channel head applications
Decontaminations are performed in the channel heads of PWRs to reduce the amount of
radiation exposure necessary to complete major maintenance activities at the tubesheet on
the primary side (e.g. sleeving, plugging etc.). To maximize the benefit, two to three
feet of the tubes above the bottom of the tubesheet need to be exposed to the reagent.
Fig. 3. BWR reactor water recirculatlon system two
phase decontamination flowpath

Chemical decontamination technology 43
This achieves maximum dose reductions while minimizing the amount of radwaste generated.
To isolate the generator from the remainder of the reactor coolant system (RCS), dam
assemblies must be installed in each nozzle. These ere large diameter inflatable sealing
devices which can withstand the maximum differential pressures involved and are compatible
with the reagents used.
Access to the channel heads is through the manway openings on each of the hot and cold
legs. Temporary covers are used which enable the decontamination equipment to be connected
to the generator via fittings on the covers. The temporary equipment required to perform
this application is similar to that used for RWR applications. Different size components
may be required by the specifics of one application or another, but the same fundamental
functions are necessary (circulation, heetup, chemical injection, sampling, reagent removal
etc.).
Under normal circumstances both channel heads of one generator are decontaminated
simultaneously. This approach minimizes the critical path time required. It is possible
to decontaminate two steam generators simultaneously, resulting in a further reduction in
critical path time.
Once the channel heads are isolated from the remainder of the RCS and the temporary
manway covers have been installed, the operating sequence begins. The generator is filled
to the approximate elevation of the bottom of the tube sheet and circulation and heatup
start. The flow paths used to circulate the reagents through the channel heads of a single
generator can vary somewhat depending upon the approach taken. The channel heads can be
connected either in series or parallel. If a second generator is added to the flow path it
is normally placed in parallel with the first one.
In the series approach (Fig. 4), the discharge flow from the decontamination equipment
enters the first channel head through the manway cover. It circulates inside the channel
head and leaves through a second connection on the same manway cover. From there it enters
the second channel head, where it again circulates inside and exits to the decontamination
equipment. The pressure drop in the llne interconnecting the two channel heads results in
a slightly higher level in the upstream channel head. By reversing flow direction, the
fluid levels can be raised and lowered enough to expose the lower two to three feet of
tubing to replenished reagent in a manner similar to that for the discharge side of the RWR
system.
m.lm~u[
l
UU
Fig. 4. PWR channel head decontamination series flowpath

In the parallel approach (Fig. 5), the flow exits the decontamination equipment to a
header which feeds each of the channel heads being decontaminated through a manway cover
fitting. Once the fluid has circulated inside each one, it returns to a second header and
then back to the decontamination equipment. Level adjustment is achieved by adding and
removing system fluid at regular intervals from a supplementary tank which rides on the
system.
When Inventories have been correctly adjusted and operating temperatures reached, the
decontamination can proceed. Operations for steam generators are identical to those for
the RWR system except that oxidizing steps must be included in order to achieve
satisfactory decontamination factors.
3.3 Comparison of RWR and channel head decontaminations
The following subsections compare the similarities and differences between BWR RWR
system and PWR channel head decontaminations from an operational perspective.
3.3.1 Similarities
(a) Predecontamlnatlon Preparations. To prepare for any decontamination a certain
number of preliminary tasks must be performed. These include the preparation of
drawings and procedures to make them site specific, the procurement of chemicals,
resins and other consumables, and the maintenance and shipment of the equipment to
site. They differ somewhat In detail (as would two RWR system decontaminations) but
are fundamentally the same irrespective of whether or not the work is being performed
for a BWR or a PWR utility.
(b) Equipment Setup on Site. In order to perform the decontamination, temporary
equipment must be set up on site in the general vicinity of the component or system
being decontaminated. Even though the final location of individual pieces of equipment
varies from station to station (even from one BWR to another), the need to interconnect
essentially the same equipment remains. About the same number of personnel are
required, the basic tasks which they perform during setup are similar, and the amount
of time required to perform this task is about the same. The differences in equipment
locations between BWRs and PWRs have a relatively small effect on the total effort
involved in this task.
mJutm~
+ 0
((
l÷i
Fig. 5. PWR channel head decontamination parallel flowpath

Chemical decontamination technology .1,3
(c) Decontamination Operations. In both cases decontamination equipment has been
connected to a plant system or component that has been isolated from the rest of the
plant. The decontamination equipment and connections are tested for their integrity
prior to start-up. System inventories and process parameters (flows, temperatures and
pressures) are established, monitored, and controlled in exactly the same manner. When
the decontamination commences, the same chemicals are injected using identical
equipment and procedures. Process monitoring techniques and termination criteria for
individual steps are handled in the same fundamental way. Periodic flow reversal and
accurate level control are necessary for both cases. Reagent and activity removal is
performed for both by lon exchange vessels which are valved in, monitored, and
controlled in exactly the same manner.
In addition, the overall approach to the two types of applications is the same. Both
require that the crltlcal path time used for the appllcatlon be kept as short as
possible. Hence, both applications are performed on an around the clock basis using
multiple shifts.
(d) Equipment Dismantlin~ and Removal. As described for (b) above, equipment handling
is virtually identical for both types of applications. The same concerns over surface
decontamination of hardware, dismantling and crating schedules, and shipping exist at
both BNRs and PNRs. The time and effort involved do not differ substantially.
3.3.2 Differences
(a) The Number of Chemical Steps. One of the key differences between performing an
R~R decontamination and a channel head application is the number of individual chemical
steps which must be applied to obtain satisfactory decontamination factors. Often, a
single step will remove sufficient radioactivity in an RNR system so that no further
action needs to be considered. In the case of the channel heads, a minimum of two, and
more likely four steps will be required. This requires additional application time.
It also results in more chemicals being used and more waste being generated.
(b) System Isolation. In order to isolate the R~ system for the application, no
significant or unusual steps must be undertaken to contain the decontamination
solution. For a channel head application however, nozzle dams must be installed to
isolate the steam generator from the remainder of the reactor coolant system. This is
an extra step in the on site work which requires additional time and radiation
exposure. Current designs for these dams are such that installation times are
relatively short, thus minimizing the overall schedule and exposure impact.
(c) Equipment Connection. Generally decontamination connections per se do not exist
in P~Rs as they do in BWRs. Speclally modified manway covers are used for this
purpose. They contain inlet and outlet connections for each side of the bowl,
connections for level instrumentation, and a connection for venting or pressurizing.
High pressure rubber hoses are used to connect the decontamination equipment to the
channel heads.
3.4 Improved alternatives for PWR decontamination
A new approach which can improve the cost effectiveness for P~s is to decontaminate the
reactor coolant system rather than Just the steam generator channel heads. Using a closed
loop circulation path, the steam generator channel heads, wetted portions of the reactor
coolant pump and all of the interconnecting piping of at least one RCS loop could be
decontaminated simultaneously. This is achieved by the installation of a "Jumper" between
the loop inlet and outlet connections at the reactor vessel after the core barrel has been
removed. A proposed schematic flow diagram is shown in Fig. 6. This Jumper would be
capable of providing a seal at the internal surfaces of both RCS loop piping connections at
the vessel while, at the same time, allowing sufficient flow to pass through an
interconnecting line.
The necessary decontamination equipment would be connected to temporary manway covers on
the channel heads of the steam generator in the loop (similar to the current approach to
channel head decontaminations). The fluid level in the decontamination system would be
raised to approximately that of the tube sheet and circulated using the pump on the
temporary decontamination equipment. Flow direction would be reversed to achieve oxide
film removal to a predetermined level up into the tubes of the steam generator. By
maintaining fluid levels at these elevations in the steam generator, the system volume and

46 C.J. Wood
surface area are in the same ballpark as equivalent decontaminations for BWR reclrculatlon
systems. It is very likely, therefore, that decontamination equipment currently used in
the industry could also be utilized for this work. Further investigations of thls approach
are planned.
3.5 Discussion
Many routine decontaminations have been performed in both BWR reactor water
reclrculatlon systems and PWR steam generator channel heads. All major decontamination
vendors have portable equipment that is capable of being used for either application. It
is also capable of being used with either the LOMI process or dilute organic acid
processes. Oxidizing treatments, which are mandatory for PNR applications and optional for
BWR applications, are also handled routinely.
In order to achieve the required circulation of the decontamination reagent, RWR system
decontaminations are usually performed in two phases--dlscharge piping followed by the
suction piping. If the piping is to be replaced, temporary connections can be made at the
top of each riser and in the suction nozzles to ensure flow in all parts of the system.
This enables the decontamination to be performed in a single application wlth a net saving
in critical path time.
PWR channel head decontaminations require the installation of nozzle dams to isolate the
generators from the piping. Specially modified manway covers are used to connect the
decontamination equipment to the channel heads. Reagent level is usually controlled at 2-3
feet up the tubes. This gives maximum dose reduction in the bowl while minimizing waste
volumes. Apart from these fundamental differences, operational and chemical techniques
associated with channel head decontaminations are very similar to those employed in RWR
system decontaminations.
Later sections will address techniques to reduce recontamlnetion.
~ LEVEL
FttMO
DE(X~N r, ~mWAL FLOW :
sou: : ms~c.oN : E(~,P
: ! LEVEL
! I I
lo fq~)M
E~.~. ,'2" :~,P.
L_ ols~c.o..__j
NOTE~
,. S~,CE CCX~ SHOVM r-c~ cu~nY. ~CT~UEb.X~C~
BE OECONTAMINATED SIM~TANEOUELY.
2. SYSTEM FILLED TO APPI:IOXIMATE BLEVATION OF STEAM
~d~IERATOR 1UBE SHEE'I'. FLOW FEVERSN.S .~OOOla~JSH
DECONTAMNAllON OF BOTTOtl ENDS OF ~SES ON BOTH
HOT AND COLID LEGS AS SHOWN IN DETAIL "A'.
& JU~ ASSEMBLY I~STALLEO V~ REAGiOH ~.~ @ ll=M
REkW~VAL OF FUEL ANO CORE 8NqflEL
QF'IIIeE
,#~
DETAIL 'A' ~~__/TIGN
Fig. 6. ~ partial reactor coolant system
decontamination flowpath

Chemical decontamination technology -t7
4. CORROSION
4.1 Introduction
Corrosion has always been recognized as an area of potential concern to decontamination
users. Corrosion is generally minimized by using dilute concentrations of relatively
noncorrosive organic acids, and by including corrosion lnhibitors in the formulation.
These measures have been successful in avoiding significant corrosion damage during the
decontamination. A second issue concerns the need to demonstrate that the decontamination
will not increase susceptibility to intergranular stress corrosion cracking (IGSCC) after
return to power. It is against this more severe criterion that decontamination solvents
have been evaluated.
As part of a comprehensive program to qualify currently-available decontamination
processes, extensive testing has been carried out in recent years. These tests include
general corrosion measurements, constant extension rate tensile (CERT) tests, pipe crack
tests and crack growth rate measurements. Although carried out under BWR conditions in
almost every case, these tests results are generally applicable to PWR channel head
decontaminations. For PWR full system decontamination, however, further data on the
effects of reagents in the presence of boric acid are desirable.
Results from the corrosion programs have been published and/or discussed extensively in
EPRI seminars (4-8,12).
In this section, corrosion consequences are reviewed and the available test results are
summarized and discussed.
4.2 BNR decotamlnatlon flowpath and wetted materials
An earlier section discussed the two basic approaches to applying decontamination
solution to a BWR recirculation system, which are illustrated in Fig. 1. As noted in this
figure, the two choices consist of applying the decontamination solution only to the piping
system (A) or to the piping system plus the annulus between the reactor pressure vessel and
the core shroud (B).
Gordon (13) has provided a detailed review of BNR corrosion issues, which is summarized
here. If the decontamination process is limited to the piping system, then the piping,
pumps, and valves will be wetted by the solution. The reclrculation piping, pumps, and
valves in most operating BWRs are primarily fabricated from welded Type 304 stainless
steel. Experience has demonstrated that the pipe weld heat-affected-zones (HAZs) are
susceptible to intergranuler stress corrosion cracking (IGSCC) as will be discussed in
detail later. Partial mitigation against IGSCC has been obtained in some Type 304
stainless steel piping by the application of various stress reduction techniques, such as
induction heating stress improvement (IHSI) and last pass heat sink welding (LPHSN), that
place the wetted surface of the weld HAZ in compression. Newer BWRs have more extensive
application of these and other IGSCC remedies, including the use of Type 316 Nuclear Grade
stainless steel which is highly resistant to IGSCC. Since there exists an extensive body
of laboratory and field data that any lntergranular attack (IGA) produced by a
decontamination or passivation treatment increases the probability of IGSCC during
subsequent service, this type of localized attack must be avoided.
The pumps and valves which are also wetted in this decontamination option contain wear
resistant surfaces, low alloy steel wedges, other small parts, and valve packing
material. Accelerated general, crevice and galvanic corrosion of these parts must be
prevented to avoid premature replacement or repair of these components, which are
fabricated from a wide variety of materials.
Consider the case of allowing the decontamination solution into the annulus between the
reactor pressure vessel and the core shroud, Figure 2-1 (B). Not only is there the same
concern for the components discussed above, but with this option, a number of reactor
internals will also be wetted by the decontamination solution. The range of material
concerns will thus increase. For example, Alloy 182 weld metal stainless steel safe ends
and nozzles, as well as the crevices between the recirculation system thermal sleeves and
safe ends, are regions where only limited field cracking incidents have been observed.
Decontamination-solution produced IC~ could significantly increase the predisposition of
these components to IGSCC. Jet pump parts fabricated from welded stainless steel and
Alloy-X-750, the welded stainless steel core shroud, and the heavy section weld between the
shroud support and the shroud all have had good service experience. The good performance

J~ C J Wool)
of these components is attributed to the low stress under which they operate.
Intergranular attack in these components could lead to premature IGSCC ss was the case for
piping. Repairs oE these internal components would be extremely costly and difficult.
Therefore, it is advisable for the utillty/process vendor to thoroughly review and list
all materials (metals and non-metals) that will be wetted by the decontamination solution
and that will remain in service. This list should be used to make a preliminary
engineering Judgment of the effect of the decontamination solution on corrosion, both
during the decontamination operation and in subsequent service, for different commercially
available decontamination processes.
There are seven families of materials that should be characterized by relevant corrosion
data for decontamination evaluation. These are:
I. Austenftic Stainless Steels (Type 304, 316, 347, etc.)
2. Nickel Base Alloys (Alloy 600, 690, X-750, etc.)
3. Chromium Iron Alloys (Type 410, 420, 422, etc.)
4. Low Alloy Steels (all except SAS08-B)
5. SA508-B Low Alloy Steel)
6. Carbon Steels (SA333-B, SAI06-B, etc.)
7. Non-Metallic Materials
4.3 Fabrication history
The primary motivation for the materials review described in Section 4.2 is to minimize
the potential for intergranular stress corrosion cracking (IGSCC). Depending on the flow
path selected, it is possible for the decontamination solution to contact stainless steel
welds within the reactor pressure vessel, especially in the shroud-to-vessel annulus
region.
In general, the long term IGSCC performance of welded stainless steel internal
components has been excellent, principally because of the low sustained applied loads.
This contrasts with the situation in piping, where high stresses are present. Since the
total tensile stress must be over the yield stress to inlt~ate IGSCC in weld sensitized
Type 304 and 316 stainless steel, it is highly likely that the low stress internal weld
HAZs will not experience crack initiation over the plant lifetime. If a decontamination
solution was sufficiently aggressive to initiate intergranular attack (IGA), it might be
possible for subsequent intergranular crack propagation to occur during service. Thus, the
identification of weld locations in the decontamination flow path is critical. These are
the areas most susceptible to cracking due to the presence of a sensitized microstructure
in the weld heat-affected-zone (localized chromium depletion as evidenced by the presence
of chromium carbides at the austenitlc grain boundaries) and high tensile stress including
the weld residual stress.
Another material condition which should be carefully identified is the presence of cold
work. Cold work is the result of any mechanical process (such as cutting, sawing,
grinding, machining, shearing, drilling, boring, broaching, honing, tube expansion,
turning, hammering and bending), which results in plastic deformation at a temperature and
time interval such that the strain hardening is not relieved. Cold working not only
increases the gross chemical reactivity of a metal end thus leads to a general decrease in
the corrosion resistance of the metal, but also increases the susceptlbility of annealed
and sensitized stainless steel to stress corrosion cracking. Cold work also results in
stress corrosion cracking at applied tensile stress levels below the cold worked material's
yield stress.
4.4 Stress considerations
There are primarily four sources of stress: fabrication stresses, primary, secondary
and cyclic stresses. Fabrication stresses consist of stresses introduced during fit-up and
assembly in the shop or in the field, those introduced by machining or forming operations,
such as surface grinding or cold straightening, and by other operations such as welding.
For example, grinding can Introduce surface tensile stresses near to the yield point.

Chemical decontamination technology 4.9
Welding residual stresses near the yield point can also be present in pipes. Primary
stresses from the operational forces on the equipment may be as high as the local yield
stress. Secondary stresses, for instance from thermal expansion, may also locally reach
the yield point. Finally, cyclic stresses from vibrations or from changes in operating
mode can also add to the sum. Such varying stresses may be of great importance in
initiating cracks, or in restarting stopped cracks, for they provide continuing plastic
strain.
4.5 Crevices
Crevices are geometric configurations in which the cathodic reactant such as oxygen in
the BNR can readily galn access by convection (natural and forced) and diffusion to the
metal surface outside the crevice, whereas access to the layer of the stagnant solution
within the crevice is far more difficult and can be achieved only by diffusion through the
narrow mouth of the crevice. This results In the cathodic reaction occurring outside of
the crevice while the anodlc (corrosion) reaction occurs inside the crevice. The pH
decreases in the crevice and the charge imbalance between the exterior and interior
surfaces of the crevice results in the transport of anions into the crevice solution. Some
anions such as chloride in combination with acidity, cause permanent breakdown of the
passive protective film on the metal surface and initiation of rapid autocatalytlc crevice
corrosion. This local corrosive environment can also result in premature SCC.
Therefore, the first concern for decontamination solutions relative to crevice
geometries is that the aggressive species in the decontamination solutions will become
trapped in crevices. During the decontamination process itself, these species can initiate
crevice corrosion, and during subsequent operation they may initiate premature cracking.
However, during reactor start up, organic acids break down to carbon dioxide relatively
rapidly, and so will not remain in the crevice for long periods, as may be the situation
with chloride (1...4_4).
4.6 Galvanic couples
Any two metals with different electrode potentials can form a galvanic couple. The more
active metal will suffer accelerated corrosion while the more noble metal's corrosion rate
will decrease. Since the rate of corrosion attack is a function of the amount of current
per unit area (current density, amps/cm ~) being drawn out of the anodlc area, the relative
area ratios between the cathode and anode are extremely important. In the operating BNR,
the various structural materials, such as stainless steel, nickel base alloys, low alloy
steel, carbon steel, and weld metals, do not suffer from galvanic attack because of the
poor conductivity of high purity water. However, when exposed to strong electrolyte
decontamination solutions severe galvanic corrosion can occur.
4.7 Non-metalllc materials
Decontamination solutions can have detrimental effects on non-metallic materials such as
valve packings and pump seals. For example, asbestos valve packings with metallic fillers
can experience accelerated dissolution and leaching during decontamination. Some
decontamination solutions will have no effect on good pump seals and valve packings but may
severely degrade marginal materials.
4.8 Types of corrosion testin~ (Table 3)
As noted above, chemical decontamination of reactor components and circuits requires a
rigorous understanding of corrosion effects, both during the decontamination campaign and
when the components are returned to service. Introduction of dilute chemicals was in part
the result of corrosion concerns caused by strong or concentrated chemicals used in the
past.
The common dilute chemical processes have been extensively tested and the results have
been documented regarding their corrosion effects upon reactor structural materials.
Although the majority of alloys tests are the 300 series stainless austentics, there are
sufficient data for nickel-base alloys and some carbon end low alloy steels. Initial
testing was limited to materials loss (weight loss), but sophisticated conditions have been
applied to include crack growth under cyclic loads, constant extension rate tensile tests
(CERT) and electropotential measurements. Standard geometry (dog bone, bent beam, U-bend,
and pressurized tube width opening) test specimens were used extensively, and large
diameter pipe (with welds) was selectively tested to determine crack initiation and crack
propagation under cyclic loads.

50 C.J. VV'OOD
4.9 Materials tested (Table 4)
Emphasis on austenltlc alloys is due to the fact that about 95% of BNR and about 15% of
PNR metal surface is constructed of 300 series stainless steel. Inconel 600 is predominant
in PNR steam generators where decontamination has been exclusively applled to date.
Nickel-based alloys ere used in other critical applications, such as internal support welds
(Inconel 82/182), Jet pump end fuel spacer components (Inconel X-750) in BNRs and spllt
pins in PNRs. Vessel nozzles and shell in BNRs as well as vessel shell in PWRs are made of
A533, and carbon-low alloy piping is prevalent in BNR reclrculatlon systems. A
comprehensive llst of materlals comprising BNR components was compiled in reference (13)
which must be considered when e full system chemical decontamination is contemplated.
4.10 Corrosion testln~
Gordon (34) has summarized the results of GE testing as follows. A fuller account is
given by Walker (16).
To date, indications of good performance have been observed in the test programs with
LOMI end in post-decontaminatlon service. The test data indicate that general corrosion
rates during decontamination processing are low for both eustenltic end ferritlc materials
(less than 0. I ~m/h and less than I ~m/h, respectively) (29). No IGA or IGSCC has been
observed to occur during decontamination. Constant extension rate tensile test (CERT),
crack growth and pipe tests conducted in a BWR environment using decontaminated specimens
generally indicate no acceleration in crack growth rates or predisposition towards
accelerated crack initiation as a result of LOMI exposure. For this particular test
program, the only statistically significant deleterious effect of LOMI occurred on the
crack growth rate of Alloy 182 (30). However, this crack growth rate is still typical for
non-decontamlnated Alloy 182 in nominal BNR environments.
To date, indications of good performance have been observed for stainless steels with
NP/LOMI but test results for some materials that may be contained in the reactor vessel
annulus (low alloy steels) have not been as positive. Addltlonelly, other materlels which
are in pump and valve components (e.g., brass end Cu-Ni alloys) may be adversely
affected. General corrosion rates during decontamination processing are low for both
eustenltlc end ferrltlc alloys. The data available for stress corrosion performance of
Type 304 stainless steel are essentially good, although early isolated instances of shallow
IGA in sensitized U-bends of Alloy 600 end shallow IGSCC in one U-bend of welded Type
316L/321SS (one out of nine specimens) are noted. More recently, an NP/LOMI treated crack
growth specimen of A508 Low Alloy Steel exhibited accelerated crack growth in a simulated
BNR environment test, relative to growth rates for reference (untreated) specimens.
Exposure of NP/LOMI to A508 low alloy steel (e.g., feedweter nozzles) should be avoided.
Since feedwater nozzles ere located high up in the reactor vessel, avoiding exposure of
these components is practical.
Various types of general/locallzed corrosion tests have been performed in AP/LOMI
decontamination solutlons (31). Some (0.25 pm) general corrosion has been noted on Type
410 stainless steel after 24 hours of testing. Corroslmeter data on Alloy 600, Type 304
stainless steel and carbon steel revealed no corrosion during a Surry steam generator
decontamination. Some isolated shallow pitting (4 pm) but no IGA were noted on both
furnace sensitized end solution heated Type 304 stalnless steel exposed to LOMI and
AP/LOMI. Studies at Battelle Pacific Northwest Laboratories (15), on various U-bend end
tensile specimens of Type 304 stalnless steel and Alloy 600 revealed no increased
propensities for IGA or IGSCC. Recently studies on AP/LOMI decontaminated highly-
irradiated mill annealed Type 304 stainless steel revealed no corrosion attack in the
presence or absence of crevices or any adverse effect on IGSCC resistance (32).
Crack growth tests on Type 304 stainless steel compact tension specimens indicated no
statistically significant deleterious effect of oxalic acld/cltric ecld/EDTA reagents with
ferric ion control.* However, accelerated crack growth was observed with Alloy 600, Alloy
182 and AI06 carbon steel specimens exposed to these reagents end subsequently tested in e
simulated BNR environment. Also, exposure of an A508 low alloy steel specimen, albeit
early in the ferric ion control development process end possibly under conditions of
galvanic coupling, also resulted in such severe general corrosion that the specimen could
not be tested. No acceleration of crack growth behavior was noted on Type 304 stainless
steel specimens exposed the same reagents wlthan AP preoxldatlon step (30). No corrosion
*Discussion of ferric ion control is given in Reference 14.

1.000E-06
1.000E-O7
1.000E-08
Chemical decontamination technology
Crack Growth Rate (mm/s)
LOMI NP/LOMI CAN- AP/CAN- W MOD
DECON Fe.,.*÷ DECON DCD NS-1
STATISTICALLY SIGNIFICANT THRESHOLD
Fig. 7. Crack growth rates of type 304 SS
attack was noted on irradiated Type 304 stainless steel specimens in the absence of a
crevice. However, shallow pitting occurred on specimens with a crevice. No acceleration
in IGSCC was noted on the irradiated Type 304 stainless steel.
General corrosion rates for carbon and low alloy steel were generally less than 1 ~/h
for citric acid/oxallc acid reagents. Early tests did not indicate IGA or IGSCC during
decontamination of sensitized austenltic materials. However, IGA has been observed in more
recent studies of sensitized Type 304 stainless steel and sensitized Alloy 600.
4.10.1 Discussion of Summarized Corrosion Results. The above results indicate that for
some BNR structural materials care must be used in the application of many commercial
decontamination solutions relative to the material integrity of the BNR. For Type 304
stainless steel (and similar stainless steel alloys), none of the major decontamtnatiou
solutions produced a statistically accelerated crack growth rate, Fig. 7.* As discussed
elsewhere (30), this result was supported by full-size pipe testing, where no dramatic
differences were noted iu IGSCC behavior for pre-filmed only, Fig. 8, or pre-filmed and
pre-cracked Type 304 stainless steel piping. However, for some alloys such as A508 low
alloy steel, significant crack growth acceleration was identified in all solutions tested,
except LOMI. Also, Alloy 182 indicated a statistically significant increase in crack
growth rate in all three solutions tested. However, the range of measured crack growth
rates falls among those obtained without decontamination solutions. Overall, some
processes are clearly less detrimental than others end it is these processes which warrant
further development and future consideration.
*Designations in Fig. 7 not mentioned previously are: W-DCD is a Westlnghouse-developed
decontamination group of chemicals, whereas MOD NS-I are solutions developed by Dow
Chemical Company.
51

Ratio-Treated/Ref.
2"0 I
1.5
1.0
0.5
0.0 ~
CAN- AP/CAN-
DECON Fe÷÷d3ECON
LOMI NP/ MOD NEW CAN- PNS W
LOMI NS-1 DECON ClTROX DCD
STATISTICALLY SIGNIFICANT THRESHOLD
Fig. 8. Type 304 SS pipe, prefllmed, time to failure ratio
4.11 Recent corrosion data from third BWR decontamination seminar
Five papers were presented at the Third BWR Decontamination Seminar (7), each with a
special emphasis on issues likely to be encountered when full system decontamination is
considered. A methodology was used to evaluate corrosion of all wetted surfaces prior to a
plant specific decontamination campaign (33). This approach was endorsed by GE as a
precondition to full system decontamination, provided LONI is applied in accordance with
approved procedures. The use of crack arrest verification system (CAVS) was recommended to
verify normal IGSCC crack growth when the plant is returned to service (34).
Extensive data were presented describing corrosion of carbon steel during LOMI solvents
application (35). The data were generated under flowing conditions, in anticipation of a
decontamination campaign of the N-Reactor at Hanford. Corrosion rates of carbon and low
alloy steels were measured at less than 0.67 microns per hour, 400 series steels exhibited
metal losses of 0.7 microns per hour and weld overlay specimens were unaffected by the LOMI
reagents. Welded carbon steels showed no evidence of corrosion attack on either heat
affected zones or weld metal itself. No effects were observed from the residues of LOMI
reagents left in contact with carbon steel for an extended period.
A comprehensive review of decontamination experience in Canadian reactors showed that
application of CAN-DECON solutions was successful in 13 CANDU reactor heat transport
systems (36). The procedures have been used routinely in full systems which include cores
and fuel in place. Although the CANDU reactor system geometries differ from the U.S. water
reactor circuits, the materials involved are similar. Testing to qualify the CAN-DECON
reagents was described and the resulting data are evaluated as to their applicability to
U.S. reactor systems.
4.12 Corrosion data needs to permit full system decontamination
Full system decontamination (FSD) is the ultimate goal in the effort to minimize
recontamination of out of the core components. A significant step toward FSD was achieved
recently, when discharged fuel bundles from Quad Cities BWR were decontaminated using LOMI
and CAN-DECON reagents (37). Work is in progress to resolve technical issues that will
permit FSD in both BUs and P~'Rs.

Types of corrosion testing of decontaminated materials
Table 3.
Crack Pipe Test CERT Electropotential
CERT Growth (BWR) (Irrad.) Measurements
Bend
General "U"
Process Corros ion
18,20,22 18 18,19,21 20 14,25
26
23,29
CAN-DECON 20,14,22
CAN-DECON (Fe) 28,29
or EDTA and
Improvements
r~
17 18,19 19,21,26 17
25
14,28
AP/CAN-DECON
c.
C
20,23, 18 18,21 20 14
24,27
24,25,
29
20,14,23,24
27,29
CITROX and
AP/CITROX
3
15 16,18,19 16,19,21,25 15,25
20,21,26
12,15,25,
12,15,25,29
29
LOMI
f-.
15,2 16,5 17 15
12,15
12,15,29
AP/LOMI
15 16,5,8 16,19,21,26 15
29
12,15
12,15,29
NP/LOMI
Numbers shown denote references.
+Jl
r~,P

Table 4. Corrosion Testing of reactor materials in decontamination chemicals
Austenitic
Stainless Nickel Low Carbon Non
Steel Base Alloy Steels Steels Metallic Welds*
Process
CAN-DECON
CAN-DECON (Fe) 18,19,20 18,19,20 18,20,21 18,19,21 28 19,20
or EDTA and 21,14,22,25, 21,22,28 22,28 22,28 28 25
Improvements 26,28
AP/CAN-DECON 17,18,19 19 28 19
21,14,26
20,27 25 24 19
CITROX and 19,20,21, 16,20,
AP/CITROX 14,23,24, 23,24,27
25,27
15,19,25,
26
LOMI 12,15,18,19, 1,11,18,19, 18,19 18,19,21,26 24
10,21,24,25, 20,21,24,26 20,21,26
26
AP/LOMI 12,15,17 12,23 15
15,19
NP/LOMI 12,15,18,16, 12,15 18,8 12
21
Numbers shown denote references.
*Mostly type 304, 316 stainless and Inconel 182

Chemical decontamination technology 55
Corrosion issues require data dealing on all materials to be wetted by the
decontamination chemicals. In particular, avoidance of IGSCC must be established with a
high degree of reliability.
4.13 Discussion
Substantial progress has been made in recent years on documenting corrosion effects of
decontamination solvents on B~ plant materials and on understanding the observed
effects. LOHI continues to appear innocuous and is fully qualified for BWR piping system
applications. Some adverse effects (IGA, pitting, rapid general attack) have been observed
with dilute organic acid reagents. These effects can be minimized by tight control of
reagent chemistry, including ferric ion content, but creviced configurations remain of
concern, because chemistry control is difficult in crevices. Laboratory studies suggest
that the presence of oxalic acid is necessary for IGA to occur.
Additional tests on low alloy steels are in progress. Recent data indicate minor
cracking of low alloy steel exposed to the nitric permauaganate (NP) preoxidatton
process. There was no cracking on identical specimens exposed to the alkaline permanganate
(AP) or LOMI processes. Here again, utilities have the choice of using a preoxidizing step
before LOMI to get the best possible decontamination factor, or using IX)HI alone, which is
quicker and cheaper with no corrosion concerns, but which will not be so effective on high
chromium oxides.
A major step forward has been the generic approval given to the LOMI process by GE
Nuclear Energy for full system decontamination. This resulted from an in-depth review of
corrosion data; the stated provisos, including a plant specific review, should not delay
the implementation of the technology. GE did not endorse the NP or AP preoxidatlon steps,
but these should not be required for BWR full system decontamination in view of the
improved efficiency that results from the use of the reactor coolant pumps.
In summary, process restrictions to minimize corrosion have been defined and there is
ample data available now for utilities to select a process for their particular
application.
5. RECONTAHINATION
5.1 Introduction
Recontaminatlon occurs when the freshly-decontamlnated surface picks up activity, as the
surface reestablishes its protective corrosion film. Inltlally, corrosion is rapid, but it
slows down as adherent passive oxides cover exposed surfaces. When part-system
decontamination has taken place, the reactor coolant will contain high concentrations of
radioactive species, which were not present during the original plant commissioning time
period when corrosion films were inltially developed on these surfaces. Consequently the
new, rapldly-developlng corrosion film will incorporate significantly higher concentrations
of radioisotopes and cause a rapldly-lncreaslng radiation fleld in the vicinity.
Early part-clrcuit decontaminations of B~/Rs that used concentrated reagents resulted in
extremely rapid recontamlnatlou rates. In one case, a reactor pilot loop reached radiation
levels higher than before the decontamination in 500 hours. Fortunately, the
recontamlnatlon problem, although still slguiflcant, is less severe when dilute chemical
processes are used. The most likely explanation of the high recontamlnatlon rates observed
after use of concentrated reagents is that these reagents were actually corrosive, removing
the entire protective film and roughening the underlying surface. A similar phenomenon was
observed on steam generator channel heads decontaminated using a dry grit-blastlng process,
which exhibit increased buildup of radioactive materials after return to power(38). In
several cases, radiation fields in the decontaminated channel heads became slgnlflcantly
higher within a few years than equivalent channel heads that had not been decontaminated.
Recontamlnatlon rates in channel heads following dilute chemical decontamination are
generally not so great.
5.2 Recontamlnation rates
As a general rule, recontaminatlon rates following dilute chemical decontamination ere
similar to or slightly greater than Inltlal radiation buildup rates on new plants, but less
than buildup rates ou new components such as replacement reclrculatlon piping in BNRs or
replacement steam generator channel heads in PNRs.

0
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Z a
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Chcmic~tl dccontuminution tcchnolo~ ~7
For BWRs, the most effective passlvatlon process for decontaminated surfaces would seem
to be continuous zinc injection (45). In fact, zinc is most effective on fresh or
decontaminated surfaces, and a decontamination represents a desirable starting point for
zinc injection.
For PNRs, operation at elevated pH is the most cost-effective method of reducing
radiation buildup. Preferably, elevated pH should be adopted for the fuel cycle before the
decontamination so that the inventory of radioactive corrosion products in the core is
reduced, thereby minimizing the source of cobalt-60 for subsequent redepositfon out of
core.
6. WASTE MANAGF~ENT
6.1 Introduction
After use, chemical solutions from the decontamination process become radioactive and
are processed through ion-exchange resins to remove the radioactive material and other
unwanted ionic species. The processed liquid is then either transferred to normal plant
water systems or further processed as plant liquid effluent. The spent resins become
radioactive waste that must be stabilized, transported and disposed according to Nuclear
Regulatory Commission regulations 10CFR61 and applicable revisions (46,47). Additional
criteria are also imposed by the three licensed commercial disposal sites. Compliance to
regulations has been demonstrated for CAN-DECON, LOMI, NS-1 and AP/CITROX processes. The
presence of chelating components in the waste products is significant, in that the
Baruwell, South Carolina waste disposal site requires a stabilization step for chelate
concentrations exceeding 0.1Z and places a maximum 8Z (by weight) on chelate content in a
given shipment.
A review of decontamination waste management was conducted by EPRI in 1985 describing
early utility experience in dealing with this type of waste stream (48).
6.2 Minimizing waste volume generation
Chemical decontamination of nuclear power plant systems using dilute chemical processes
has replaced earlier processes that used high concentration chemicals not only to overcome
concerns about system corrosion but also reduce the volume of wastes generated. However,
even with current chemical reagents operating at 0.1% concentrations, disposal of the
resultant wastes can represent up to 30% of the cost of a decontamination campaign.
Options for optimizing existing decontamination processes have been successfully introduced
which reduce the volume of waste generated significantly. Reagent chemistry was adjusted
and a new ion exchange material was introduced without loss of process decontamination
efficiency (I_II). Similar improvements have been realized for both CAN-DECON and CITROX
when the new ion exchange material is adopted. These processes, because of their inherent
regenerative mode, result in smaller waste resin volumes.
6.3 Low-formate LOMI reagents
The basic LOMI decontamination reagent consists of 1 mole of vanadous formate (V 2+) ion,
6 moles of picolinic acid, and up to 10 moles of formic acid for each mole of ferric (Fe ~+)
ion to be dissolved. The quantities of vanadous picolinate and picolinic acid ~e in
stoichiometric proportions required to react with the calculated quantity of Fe ~- that will
be removed; however, formic acid is present in large excess due to the vanadous
manufacturing process.
Vanadous formate is manufactured using electrolytic reduction of vanadium pentoxide
(V205) in the presence of excess formic acid. High concentrations of formic acid are
required during the manufacturing process to act as a charge carrier during the+)
electrolytic reduction and to prevent t~ precipitation o~hydrnted vanadic (V ion as
the vanadium is reduced from vanadyl (V "T) to vanadous (V'T). Once all the vanadium is In
the 2+ oxidation state, the excess formic acid is no longer required and can be removed
before the LOM1 reagent is shipped to the user.
The LONI solution suppller ~itially believed that the excess formic acid was necessary
to maintain the stability of V 6 in solution. However, this excess formic acid then
required additional ion-exchange resins at the end of the decontamination process which
resulted in larger waste volumes. The additional ion-exchange resin was required for two
reasons:

5S C.J. Wool)
(I) -The removal of formate at the conclusion of the decontamination process requires
additional anion-exchange resins.
(2) The addition of NaOH to neutralize the excess formic acid to adjust for proper pH
prior to the decontamination requires additional cation-exchange resins to remove the
Na- at the conclusion of the decontamination.
The vanadous supplier was able to reduce the formate to vanadous ratio from 8:1 to as
low as 2.5:1 by adding a suspension of strong base anion resin beads to the vanadous
formate solution (II). By reducing the amount of formate in the LOMI solution, it was
possible to reduce the volume of Ion-exchange resins by one half. Laboratory tests
established that the decontamination performance and thermal stability were unchanged from
the original LOMI formulation. In fact, long term storage tests indicated that the low-
formate reagent had storage properties at least as good as the original high-formate
formulation (49).
6.4 Introduction of an improved anion resin
Further improvement of the LOMI process was realized when a new, weak base anion
exchange resin was used in field applications, loner A-365 has a capacity of 2.5
mlllIequlvalents per milliliter of volume, which is a factor of 2.5 times the capacity of
the previous anion resin beads.
The combination of reduced formic acid and use of loner A-365 in the LOMI process,
resulted in waste volumes comparable to those produced by CAN-DECON and CITROX processes
(ii). A comparison of resulting waste volumes in recent decontamination projects Is shown
in the table below.
Table 5. Resin requirements at recent BWR RWR decontaminations
Plant Vermont Dresden Brunswick Quad Cities Peach Bottom
Yankee Unit 3 Unit 2 Unit 1 Unit 3
Decontamination Dilute LOMI Dilute LOMI** LOMI
Process CITROX CITROX NP NP
Utilized HYDROLASE LOMI LOMI
Cubic Feet ***
Resin 192 163 225 168 240
Generated
Overall
System DF 8.0 12.4 12.5 8.1 15.2
Total
Decontamination ii* 9 19 8 ****
Time (Days)
*Includes 6 days for hydrolaslng
**RRS Discharge had a three-step process while Suction and RWCU experienced
on a one-step LOMI
***Quantity includes both RRS and RWCU decontaminations
.... Due to plant delays total length of time not relevant. From initial
chemical injection to final cleanup required approximately 3.5 days
Data taken from Reference (IO).
6.5 Future potential Improvements in waste volume reduction
Laboratory and pilot tests indicate additional potential improvements that may in time
be adopted to reduce waste volumes arising from dilute chemical decontaminations.
Possibilities include:

Chemical decontamination technology 59
Ca) Spent resin destruction using wet oxidation techniques (50).
(b)
(c)
Substitution of potassium permanganate oxidation processes by the use of ozone to
produce gaseous decomposition products (I_!I).
Use of strong acid, hydrogen form cation exchange resins to lower pH and to
effectively replace the addition of HNO 3 during permanganate destruction and thus
reduce waste volumes (I!I).
6.6 Disposal of solidified wastes
The spent resin must be solidified for disposal according to NRC Regulations 10CRF61,
and the U.S. NRC Branches Technical Position (BTP) on Waste Form (1983), which establishes
the procedures, criteria and terms upon which NRC issues licenses for handling radioactive
wastes destined for landfill burial. The form to be buried must possess structural
stability such as to satisfy the 300-year criteria required by Part 61. For resins, the
most commonly used form of solidification is mixing and setting into a homogeneous cement
monolith (51,52). To obtain process approval for a given waste stream, the solidified
mixture must be subjected to a series of "stability" tests, producing data to be included
tn a topical report for review and approval by NRC 46-48). Additional special criteria
have been imposed by the burial sites and these will be discussed in subsequent paragraphs
of this report 446-48).
6.7 Stablllt~ tests
Stability of waste forms must be established by means of a formal process control
program (PCP) which must include the following components:
Compressive strength 450 psi)
Biodegradatlon resistance
Resistance to leaching in specified solutions 490 days)
Demlnerallzed and sea water immersion for 90 days followed by
a compressive test (50 psi)
Resistance to thermal degradation in structure
Integrity after exposure to gamma radiation (10E8 fads)
Contains less than 0. SZ (volume) of free standing liquid.
The results from the stability tests must be provided in a topical report, and waste
stream stability test results must specify the content of chelating agents.
6.8 Requirements of disposal sites
Because of differences in hydrological conditions, the licensed disposal sites have
placed specific requirements for waste burial. In addition to the chelate concentration
limitation mentioned above, wastes buried at Baruwell must be separated from other class B
and C wastes by I0 feet, and an extra charge is assessed (4_~8).
Although there is no upper limit to chelate concentrations for disposal at the Hartford,
Washington disposal site, there is a segregation requirement for wastes that contain
chelates exceeding 0. I percent by weight. A 10-foot soll separation is required, either by
separating trenches or segregation within a given trench, usually resulting in doubling the
burial volume when compared to waste containing less than 0.1Z by weight. The
Hanford/Richland burial site considers "chelated" waste only when the chelate exceeds 0.1Z
by weight, before pretreatment. Segregation is required if the chelate concentration
exceeds 0.1% after treatment.
Each waste stream must be certified as to its compliance to 10CFR61 stability tests, but
different plants can utilize the same PCP (vendor qualified) and be certified for
disposal. A new certification is required when the formulation of the decontamination
reagent changes significantly. Shipment of solidified liners is performed according to
U.S. Department of Transportation regulations that stipulate container radiation limits and
the use of strong, tight containers. Upon arrival at the burial sites, inspection
techniques consist of drilling the cemented liner at random locations, with at least one of
the core samples taken from the bottom perimeter of the cylindrlcal containers.
The acceptance criteria are that no free standing lfquld is found and homogeneity of
core samples is apparent upon visual inspection. Drilled holes are then plugged and liners
are buried in appropriate trenches. Liners that fall to pass inspection are returned to
the originating site for repackaging, along with an imposition of a fine to be paid by the
shipper according to regulations.

60 C.J. Wooo
6.9 Complications encountered with the cement solidification of spent resins
In a recent EPRI seminar, the subject of waste solidification, packaging and burial took
center stage in view of field experience from reactor decontamination activities (51-53).
The Nuclear Regulatory Commission seminar participants made several key observations that
warrant mentioning. Over the past couple of years there have been several incidents where
problems have been encountered with cement solidified wastes. These incidents include
problems with expansion, disintegration, non-solidlflcatlon, and overly-rapld
solidification of cement solidified waste forms. Examples are (I) the cracking and
splitting of two liners at Three Mile Island (caused by expansion and disintegration of the
cement-solldlfled bead resin waste); (2) expansion of a liner containing cement-solldlfled
LOMI decontamination waste on bead resin at Millstone; (3) non-solldlflcatlon of LOMI-
decontamination waste (on resin beads) at Fitzpatrick; (4) too-rapid solidification
(occurring before the prescribed amount of cement could be added to the mix) st Quad
Cities; and (5) excessive foaming (due to detergent "impurities") at Sequoyah.
Contributing factors in these cases appear to include the following:
Excessive loading (as a fraction of the total volume of the waste form) of bead
resin.
The presence of decontamination solution chemicals.
The presence of ingredients ("impurities") in the waste stream that were not
tested in the laboratory development of the waste formulation or recipe.
A lack of knowledge by the waste generator/processor of what specific composition
is being processed.
The potential impact of this situation on the future use of cement for low-level waste
stabilization is that NRC may take certain actions in the near future. First, at least for
certain troublesome waste streams such as those involving bead resins and decontamination
chemicals, waste loadings will have to be significantly reduced. In some cases, the
current waste loading approach 70 to 80 percent by volume of the waste; that is, cement
comprises only 20 percent by volume of waste form. Thus, there is simply too little
cementitiOus material available to bind the waste together and to provide the required
structural stability. The approach taken toward qualifying the waste formulation, or
recipe, has been essentially empirical and is not one that is primarily based on a precise
scientific understanding of the fundamental mechanisms involved. Some margin must be
provided to compensate for effects that are not addressed in the laboratory testing where
PCP data are generated.
A second approach that should help to reduce the llkellhood of encountering problems in
producing stable solidified waste forms is to improve the waste handling end
characterization. Though some utilities are doing well in that regard, it is clear that in
some cases the wastes are being handled in a manner that can lead to solidification
problems. Examples include situation where wastes from different waste streams are placed
in the same tank and where adequate analyses of the resultant mix of wastes are not
obtained prior to processing. A few hundred parts per million of ingredient can have a
drastic effect on the set time and ultlmate solidification of a cement waste form.
A third approach that should be investigated further involves the chemical or thermal
treatment of the waste material, particularly bead resin material, to render it move
resistant to interaction with the cementltlous material. An example of such a process is
one that is used in Sweden, where certain resins wastes are heated to 150 degrees Celsius
for ten to fifteen hours, as a pretreatment before solidification in cement. The volume of
organic ion exchange resins is reduced by loss of interstitial and internal water by the
heat treatment. Thermal decomposition of the quaternary ammonium groups produces a reduced
tendency to swell when wetted.
Recent attempts to solldlfy waste resins generated from reactor system decontamination
provided an opportunity to study the cementation process more closely (5_~4). The genesis of
the problem is believed to be the introduction of weak anion resin Ionac A-365 with a
capacity 2.5 times that of anion resins used in the past to remove plcollnlc acid from LOMI
streams (I0). A "solidlfled" llner was found to contain serious nonhomogeneltles, sample
portions showing large concentrations of resin not set into cement.

Chemical decontamination technology 6!
Independent studies by two waste disposal vendors (51,52). and by a utility affected by
a "non-solidlfled" liner revealed that plcolinic acid forms a calcium hydrate compound when
lime is added to the resin which is to be cemented. When the amount of ptcolinic acid is
"excessive" as in the Ionac A-365 anion beads, the hydrate formed interferes with the
mixing process (54). Although the mechanism is still being studied, thixotroplc mixtures
were produced in the laboratory where picolinic acid was treated with lime.
The same studies showed that solidification could be improved by a) reducing the loading
of picollnlc acid on the resins, or b) reducing the fraction of anion resins in the liner,
c) using sodium hydroxide in whole or in part for pH adjustment or d) dilution of resins
with water. The overall impact of all but remedy c) will be to increase the volume of the
final waste form and thus impact burial costs. A cost/benefit analysis during the planning
stages of decontamination should include remedial strategies for waste dlsposal, Including
impact on volume increase in order to achieve solidified liners acceptable for burial.
6.10 Reduction of waste volume - new techniques
When cemented for disposal, each cubic foot of resin yields 2 to 3 cubic feet of
buriable volume. Thus, burial charges alone could be as high as $180/ft ~ of untreated
resins waste..There is a compelling incentive to reduce the volume of waste resins either
by loading more activity per unit volume or by converting the resin to volatile products
(H20, CO 2) and then treating the small fraction of residue by solidification (50).
Ion speclfic,_high capacity "media" were reported to absorb radioactive species with a
total dose of 109 fads, a factor of I0 higher than the levels now permitted for organic
resins (55). In addition, these "media" can be further volume reduced by heating to 150°F,
and their selectivity and capacity can be further tailored to make them more efficient.
Work is in progress to develop specific information to handle radioactive wastes using the
absorption, ion specific media.
Yet another approach is to "wet oxidize" resins using hydrogen peroxide to form CO 2 and
H20, plus a smell volume of residue which can be solidified using conventional techniques
(3__O0). This effort, underway at EPRI and CEGB (UK) is now being brought to pilot scale for
testing in early 1989. Initial tests will include only non-radloactlve resins, to be
supplemented with later demonstrations featuring resins which contain radioactive
species. Projected volume reductions of 3 to 5 are targeted, a significant improvement
over the 2.5 to 3 increase when burlal-ready resins are now the normal disposal options.
7. METHODOLOGY FOR COST-BENEFIT ANALYSES FOR DECONTAMINATION
7.1 Introduction
Several methods have been developed for determining if decontamination is cost
beneficial or not. They range from analyzing doses received on a Job-by-Job basis to more
global approximations of doses saved followlng a decontamination at the beginning of a
major outage. There is no simple formula that allows a utility to quickly and easily
determine if a decontamination will be cost beneficial for a particular maintenance Job.
7.2 Description of elements used in cost-beneflt analysis
Experience suggests that a more complex algorithm will be required, such as that
developed by LeSurf (56).
Value = Benefit - Cost (I)
Benefit = Man-rem Saved + Critical Path Time Saved + (2)
Future Residual Benefits ÷ Intangible Benefits
Cost = Vendors Charges + Waste Disposal Charges + (3)
Utility In-house Costs ÷ Critical Path Time
+ Rem Expended
Each element in these equations can be accurately determined for past decontaminations,
or estimated for future work based on past experience. Items included in each element are
discussed below, looking first at the elements of cost.

62 C.J. Wo¢)o
7.2.1 Vendor char~es
This is the total price charged by the decon vendor plus assistance that may be provided
by other vendors for equipment setup and tear down. If addltional HPs (Health Physicists)
are hired to monitor the Job, their costs should be included here. If waste handling is a
separate contract it may be included here or under waste disposal charges.
7.2.2 Waste disposal charges
This is the cost of solidifying, shipping, and disposing of the waste. Some of this may
be included under Vendor Charges especially if an all-lncluslve contract is let.
7.2.3 Utility In-house costs
Coats incurred by the utility in supporting the decon. This includes supplying
engineers, chemists, and HPs to support the decon and the cost of training and badging
vendor's staff. In-house craft labor may be used for equipment setup. Any supplies
purchased by the utility (e.g., ion exchange resin) should be included here.
7.2.4 Crltlcal path time
This is the extra critical path time taken during an outage because a decontamination is
performed, multlplled by the cost of crltlcal path time. The latter quantity is usually
determined from the cost of replacement power which is in the $23-$27/HWh range.
7.2.5 Rem expended
For the purpose of these examples, it is assumed that each Rem of exposure coats
$I0,000, so the total dose incurred In performing the decon should be multlplled by this
quantity.* However, care must be taken to avoid charging twice for the same exposure. For
example, the vendors may include some of these costs for their staff in their contract
price. If the utlllty includes in this quantity the cost of training, badging, monitoring,
etc., then such charges should not also be Included under Utility In-house Costs.
7.2.6 Rem saved
This is normally estimated by multlplylng the Rem actually used for a particular Job by
the DF obtained in the area to obtain the Rem that would have been used without a decon.
The difference is multiplied by the cost of the men-ram to obtain a dollar value for the
savings. This can result in an under estimate of the savings, due to factors such as
reduction of nonproductive exposure time, elimination of some crew changes, smaller number
of crews, etc. In one case analyzed, a DF of five resulted in a factor of six reduction in
the work force end factor of eight reduction in the total dose.
7.2.7 Crltlcal path time saved
If a decontamination results in subsequent maintenance work being done more efficiently
and saving critical path time, this should be calculated as a benefit using the same value
for replacement power costs as in the Costs section.
7.2.8 Resldual benefits
A decon performed in one outage will have a resldual effect on the fields in the next
outage. After a full system decon it is possible to theoretically calculate how fast
recontamlnatlon should occur, end this has been done for several cases. After a
reclrculatlon system decon, experience shows that recontamlnatlon to about 50Z of the pre-
decon value will occur In one cycle and more slowly thereafter. Therefore, it is possible
to estimate the man-rem savings in the next outage assuming work will be done in the area
of the decontaminated system. For estimating purposes it appears reasonable to assume a
residual DF of two at the following outage.
7.2.9 Intangible benefits
This category includes items that are difficult or impossible to put a price on but
which are real benefits none the less. For example, improved worker morale, social and
moral implications of reduced exposure, more frequent inspections of critical equipment,
the option to perform preventative maintenance, etc. Alsoj it may be impossible to perform
a certain task without a decontamination due to a shortage of skilled workers (e.g., ISI
inspectors, welders, IHSI operators). For some major operations such as pipe replacement,
the NRC is imposing an upper limit on the total exposure for the Job. In many cases it is
*Surveys of utilities in the United States show that a cost of $5000 to $20,000 is
attributed to each Ram of incurred exposure. The actual value used in cost benefit
analyses depends on several factors, such as dose distribution between key workers.

Chemical dccontamim~tion technology 63
not possible to stay under the limit without decontamination. Calculation of the value of
rem savings under these circumstances is meaningless, since the utility would not have been
allowed to spend the rem regardless of the cost.
If it can be shown by detailed analysis that a particular decontamination is cost
beneficial, then intangible benefits can be looked upon as no-cost extras. If
decontamination is not of net value when using the well-deflned costs and benefits, then it
may be necessary to consider the intangible benefits in more detail and perhaps assign a
dollar value to them.
7.2.10 Value
The value of decontamination is the difference between the total benefit and the total
cost, i.e., value = Z(benefits) - Z(costs).
A negative value means that the decontamination is not cost beneficial with the assumed
values assigned to the various parameters. It may still be desirable to perform a
decontamination, even at a net cost, if the work cannot be done without it or if an
excessive radiation burden would be incurred. In most cases analyzed here, there is a
large, positive cost benefit to the decontamination.
7.2.11 Cost/Rem Saved
The cost of saving one Rem by the decontamination is calculated by subtracting from the
total cost the benefits derived from future decontaminations avoided and critical path time
saved. The resulting "value" is divided by the number of Rem saved (exposure avoided) to
give the "Cost/Rem saved." If a Rem is valued st $10,000 and the cost of avoiding a Rem is
less then this amount, the decontamination looks attractive. In many cases already
analyzed the Cost/Rem saved is around $1000, making the decontamination very attractive
with the assumptions used.
7.3 Worked example of BWR reclrculatlon plpln~ system decontamination
In this section, the best available data for each of the factors discussed above for a
BWR recirculation system LOMI decontamination at Quad Cities or Dresden are used in the
overall cost/benefit equation. It is assumed that the decontamination is performed before
a major outage Involving factors such as pipe replacement, ISI or IHSI. The
decontamination is assumed to save 2000 Rem, in keeping with actual experience at Quad
Cities and Dresden. "Best Estimate" values are used for the cost elements because of the
considerable experience with decontaminations of the Commonwealth Edison stations. The
resulting value of the decontamination, in dollars, is calculated.
7.3.1 Costs
Enchant in the cost equation has been chosen so that it is st the high end of the
expected range to ensure that a minimum or worst case value is obtained.
7.3.2 Benefit
Decontamination Vendor
Chemicals
IX Resins
Waste Processing, Transportation and Burial
Utillty In-house (includes support and Rem
Exposure During Equipment Set-Up and Tear-Down)
Critical Path Time Taken (six days for a 789 MWe
unit with replacement power ($25/MWh)
Miscellaneous (badging, training, protective
clothing, etc.)
$ 350,000
60,000
20,000
60,000
350,000
2,850,000
100,000
Total Cost $ 3,790,000
Rem Saved - year 1 (shut-down in which decontamination
performed)
2000 Ram x $i0,000
Future Residual Benefits - year 2 (or next shut-down)
[2000 + 2000/(2-1)] 1/2 = 1167 ram
20,000,000

64 C.J. W

Chemical decontamination technology ~55
7.4.1 Costs
The vendor costs assumed are much higher than for the BNR case, because it is assumed
that nozzle dam supply and Installation will be the responsibility of the decontamination
vendor.
The utility In-house costs and critical path time are also significantly greater than
with the BNR reclrculation piping example, reflecting the complexity of equipment
connections and level control involved in decontaminating four channel heads (two steam
generators) simultaneously, then repeating the exercise on the other two steam generators.
The total cost estimates (minimum, best estimate, and maximum) are $6.4M, $8.2M, and
$II.I~ for LOMI and $6.9M, $9.3M, and $12.2H for CAN-DECON (see Reference 57). The major
difference between the processes is the extra critical path time assumed for CAN-DECON.
Wlth a relatively small volume compared with a full system decontamination, the advantage
of lower chemical cost and less waste produced for CAN-DECON is not significant in the
overall total.
7.4.2 Benefits
The decontaminatlon is assumed to be coincident with major steam generator inspection
and repairs, so that 300 Ram are saved by the decontamination in the best estimate case
(exposure without the decontamination assumed to be around 400 Rem or more). The maximum
immediate benefit is 500 Ram saved, and the minimum 150 Ram saved. For the second year (or
next outage), additional savings of 200 Ram (max.), 120 Rem (best estimate), and 60 Ram
(mln.) are assumed.
Savings in critlcal path time for the work to be done after the decontamination are
assumed to be 12 days (max.), 6 days (best estimate), and 4-I/2 days (mln.). In the
subsequent outage, savings of 4 days (max.), 2-I/2 days (best estimate), and i-I/2 days
(min.) are assumed.
7.5 Discussion
The decontamination shows a net benefit in the best estimate and maximum benefit cases,
with the cost to save a Rem being significantly less than $10,000. In the minimum benefit
case, the decontamination is not cost beneficial, and it would cost more than $30,000 to
save one Ram. This could only be Justified if crucial work has to be done which could not
be done in the existing fields.
8. FULL SYSTEM DECONTAMINATION
8.1 Introduction
Compared with the current practice of part-system decontamination, full-system
decontamination offers a number of advantages (57):
Lower rate of recontamlnatlon, thereby avoiding additional exposure in subsequent
years of plant operation and maintenance.
Extended interval between subsequent decontaminations, because of lower rate of
recontamination.
Easier and quicker to apply than major subsystem decontamination, with consequent
additional savings in critical path time.
General reduction in fields all around the plant, with consequent savings in
exposure of all the work force not Just those involved with a particular system
maintenance.
Increased reactor availability, because the preventative maintenance which is
possible following a full system decontamination should reduce the frequency of
outages due to equipment malfunction.
The additional maintenance, repair, replacement, end general equipment overhaul made
posslble by reduced radiation flelds will contribute to the improved performance of
crltlcal items and increased plant 1lie (PLEX, plant 1lie extension).

66 C.J. WOOD
Many full system decontaminations with the fuel in place have been conducted on the
pressure-tube design reactors, particularly in Canada (CANDU-PHW reactors), the USA
(Hanford N-reactor and other production reactors st Hanford and other government controlled
sites), and the UK (Winfrlth SGHW reactor).
A few full system decontaminations have been performed on pressure-vessel reactors, with
or without the fuel in place. Principal among these are:
Shlpplngport PWR 60 MWe USA
Dresden-I BWR 200 MWe USA
Rhelnsberg ~ 70 He GDR
Novovoronezh-I PNR 210 MWe USSR
There have been no full system decontaminations of large (>500 MWe) utillty-owned LNRs.
The next section describes the current state of knowledge on full system decontamination
and outlines on-golng work which has the objective of plant demonstrations for both BWR and
PWR plants in 2 or 3 years time. It is anticipated that the first applications will be
with the fuel removed, but that subsequent applications may include the fuel.
8.2 En$1neerln~ feasibility - BNR
The attached flowsheets (Figures 8-I and 8-2) show the primary systems that are either
directly or indirectly involved in the decontamination for the defueled and fueled
conditions respectively (56). The Reactor Pressure Vessel (RPV), Reactor Reclrculatlon
System (RECIRC), Standby L'i'quld Control (SLC), the High Pressure Coolant Injection System
(HPCI), the Reactor Water Cleanup System (RWCU), and part of the feedwater lines are
dlrectly Involved in the decontamination, since reagents will floe in these systems.
Several other primary systems which tie into the RPV will be isolated from the
decontamination flow path (and the reagents) by the first In-llne system valve. These
systems are:
o Most of the feedwater system,
o Residual Heat Removal (RHR) system
o Core spray system,
o Reactor Core Isolation Cooling (RCIC).
A chemical injection system will be flanged into the RECIRC, RWCU, or the RHR system as
appropriate for the decontamination proposed.
The control rod drives (CRD) will be isolated from the reagents in the RPV by a constant
flow of pressurized demlnerallzed water from the CRD hydraulic system into the vessel.
The maximum level of fluid within the RPV will be approxlmately the level of the top of
the steam separators. The main steam lines are above this level and therefore do not
require to be isolated from the RPV.
8.3 En~ineerin~ feasibility -
The proposed flow path for the decontamination will include the reactor vessel, the
steam generators, the reactor coolant pumps, the pressurizer the RHR systems, and all
interconnecting piping. Figure 9-3 illustrates the proposed flow path. All branch
connections which do not require decontamlnstlon will be isolated from the main floe path
(5_~.6).

Chemical decontamination technology 67
In order to perform a chemical decontamination, the following unit operations must be
provided:
o Fluid flow
o System volume and pressure control
o Process temperature control
o Chemical injection
o Ion exchange
o Corrosion monitoring
o Waste processing
Some of the required unit operations already exist as part of the system to be
decontaminated and can be used with little or no modification. Other unit operations will
have to be supplied by the decontamination vendor.
The most logical source to provide fluid circulation is the reactor coolant pumps ~nce,
(a) they are already a part of the system to be decontaminated, and (b) they have the
required flow capability (87,500 gpm each) sufficient to create turbulent flow in the
entire system.
The CAN-DER~ reagents can be added as solids, but in s LOMI decontamination, a
significant volume of chemicals will have to be added to the system. In order to maintain
pressure control of the system a surge tank will be required. The pressurizer can serve as
the surge tank since, (a) it is already connected to the reactor recirculation system, (b)
it has the necessary level and pressure control, and (c) has sufficient capacity to
accommodate the volume of reagent to be added to the system. During the decontamination,
the system pressure would be maintained at 350 to 400 psig which is the minimum for reactor
coolant pump operation.
The LOMI process operates between 165°F and 190°F. For both the fuel-ln and fuel-out
options, heat from the reactor coolant pumps (6310 kW) will be more than enough to maintain
the process. Since expected heat losses for the entire system will only be approxlmately
1200 kW, the RHR system will be required to remove the excess heat. For the fuel-in
option, the RHR system will also remove the excess decay heat. The process temperature
will be controlled by adjusting the flow rates through the RHR heat exchangers.
The LOMI chemicals must be pre-mlxed carefully and injected In a controlled manner.
There is no existing PNR system which can provide this capability. A separate chemical
injection system will Include the followlng components:
o Chemical mix tank
o Chemical injection pumps (2)
o Nitrogen purge system
o Vanadous formate container handling system
o Associated piping, valves, and instrumentation
The chemical injection system should be skid mounted to facilitate In-plant
installation. Connection to the primary piping system will probably be made through the
chemical volume and control system (CVCS).
8.4 Waste hendlins
Considerably more activity will be removed when fuel is included in the
decontamination. Full-system decontamination with fuel removed produces significantly more
waste then current part-system decontaminations but much less then the "fuel-ln"
decontamination.

68 C.J. Wo~,~
Comparative costs (LOMI) decontamination for IX resins, transport and burial are as
follows:
BWR recirc system $ 80,000
Full system - fuel out 1,300,000
- fuel in 6,400.000
PWR reclrc system $ 120,000
Full system - fuel out 635,000
- fuel in 1,300.000
Waste management is one of the key issues associated with full system decontamination.
Considerable progress is being made in improving waste disposal technology, including ion-
specific resins, volume reduction and interim storage, any of which could significantly
reduce costs. However, the high cost penalty associated with the fuel-in case is one of
the main reasons why most utilities will initially opt for fuel removal.
8.5 Materials compatibility
As a result of extensive corrosion test programs by the BWR Owners Group for
Intergranular Stress Corrosion Cracking research, the BWR position is considerably more
advanced than the PWR situation. Recently-completed tests on highly irradiated stainless
steels filled the last remaining gap in the BWR data base. These tests used 304 stainless
steel which is susceptible to Irradlation-asslsted stress corrosion cracking (IASCC).
Neither CAN-DECON nor LOMI had any adverse effects on these materials (30,37).
A recent evaluation of the corrosion data has led General Electric to conclude that the
risks associated with the use of the LOMI process for full system decontamination wlth the
fuel removed are low provided that a plant-speclfic material review of all LOMl-wetted
surfaces Is performed to verify the applicability of the existing data base (see Appendix
A).
Unfortunately the PWR data base is less complete. In particular corrosion data in the
presence of boric acid is lacking, and there are no data at the high flow rates expected
when the reactor coolant pumps are used to circulate the decontamination solvent. A two-
year industry-funded program has been initiated with Westinghouse to evaluate corrosion
issues.
8.6 Cost benefit
Cost-beneflt evaluations (56) for a number of decontamination scenarios are shown in
Figures 8-4 to 8-7, including estimates for BWR decontaminations using the LOMI and CAN-
DECON processes. The three options are (i) reclrculatlon piping system, (2) full system
Including fuel, and (3) full system with fuel removed. For these calculations the
reference plant was Quad Cities for an outage with above average maintenance requirements.
Figures 8-8 to 8-11 show estimates for PWR decontamination, using Zion as a reference
plant. The four options in this case are (1) steam generator channel heads, (2) full
system including fuel, (3) full system wlth fuel removed, and (4) as (3) but for the
special case of steam generator replacement.
For each example, costs include vendor charges, waste disposal and critical path time at
$624,000 per day. Savings include rents saved at $10,000/man-rem and critical path
savings. The net benefit is savings less costs. The second graph in each set shows the
estimates of the cost of each rem avoided.
Several interesting conclusions can be deduced from these graphs:
BWR reclrculatlon system decontaminations are more cost effective than P~R channel
head decontaminations.
The greatest net benefit is obtained from full system decontamination including
the fuel. However, radwaste disposal costs make this the most expensive option.
(Recent work suggests that radwaste costs might be significantly greater than the
costs used in this study because they assumed resin bed efflclencles orlglnally
are high.)

Chcmic~l decontamination technology 69
Full system decontamination with the fuel removed is highly cost effective prior
to steam generator replacement.
o Cost differences between the LOMI and CAN-DECON processes are not significant.
The above calculations used "best estimate" numbers for costs and savings. To give an
idea of the uncertainties involved, an example of minimum, best estimate and maximum costs
is given in Figure 8-12. The "minimum" case uses a combination of the lower range of costs
and the upper rangs of savings; whereas the "muxlmum" case uses the highest cost and lowest
savings. In this example, even the most pessimistic case shows s net benefit from the
decontamination, but in some of the other esamples, the most pessimistic assumptions give a
small negative net benefit, which means that the cost of each man-rem saved exceeds
$10,000.
All these examples are crltically dependent on the assumptions made about outage work
requirements. Tighter worker exposure limits, as discussed recently (62), or increased
requirements for inspection of pressure vessel and/or core internals w~Id drastlcally
influence the cost-beneflt calculations. Therefore, plant-speciflc evaluations are
recommended.
i )1
i )1
,)I
I~qeneratlv*
i )
i )
, - i )
mt Bxcha4nge [ I
IMF ~** "~"
.4~BD
/L
ellllll~
Fig. 10. Flowsheet for BWR full system
decontamination - defueled
IHiain Steam Flow
i~ln reed Flov
~'~ -From Turbine
d 4 ~
J~e A.*o
p4oo~r~

70 C.J. WOOD
Filter Demlneril i zeta
t4on- Reqenerat I v'
Regenerative ll:at Exchangecs
¢
)
~ Coce Sp¢iy~
iJ
Rb~.~ Pumps
(
E
]6/ .....
NRe¢icculat~n Pu~p
RItRS L> uilIpli
Fig. II. Flowsheet for BWR full system
decontamination - fueled
Main Steam Flow
i
~-To Turbine
/ LA /l~in Feed Flow
'! --~ ..... L ~ . ~ . ~ ~ i .............. ' ..... ~ ....
Flg. 12. Proposed flow path for PWR
full system decontamination
~]
Rills
~eat
Excha ncJe cs

(n
iz
3
-I
o
¢3
It.
o
(n
z
o
u
-I
..J
U~
<
.J
.J
o
6O
50-
4O
30
20
10
2000
1500
1000
500
Chemical decontamination technology 71
BWR 1 BWR 2
DECON OPTION
BWR1 RECIRC IqlqNG
IlWR2 FULL SYSTEM PLUS FUEL
BWR3 FULL SYSTEM NO FUEL
BWR 3
Fig. 13. BWR cost-beneflt analysis:
LOMI process
BWR 1 BWR 2
DECON OPTION
BWR 3
Fig. 14. Estimated cost of each rem
avoided BWR decon: LOMI process
[] COST
[] SAVING
[] NET BENEFIT
[] REM COST

T2 C.J. WOOD
(n
n-,
,<
_1
.J
o
e.,
u.
o
¢n
z
o
m
_1
.,J
¢0
n-.
,<
..I
.J
o
60
50
40
30
20
10
0
2000
1500
1000
500
BWR 1 BWR 2 BWR 3
DECON OPTION
BWR1 RECIRC PIPING
BWR2 FULL SYSTEM FLUS FUEL
SWR3 FULL SYSTEM NO FUEL
Flg. 15. BWR cost-beneflt analysis:
CAN-DECON process
BWR 1 BWR 2 BWR 3
DECON OPTION
Fig. 16. Estimated cost of each ram
avoided BWR decon: CAN-DECON process
[] COST
[] SAVING
[] NET BENEFIT
[] REM COST

ul
n-
<
.,J
.J
O
iA.
O
01
z
o
..J
,.J
30
20
10
6000
5000
4000
3000
2000
1000
0
Chemical dccontalminution technology 73
PWR 1 PWR 2 PWR 3 PWR 4
DECON OP~ON
~ml i,uu. ~ ~.us i,tm,
IqA,J. ~ No i,tl.
AI I~JlU WtYN ~3LMJ ~ IMLmi.AClBMB~I'
Fig. 17. PWR cost-benefit analysis: LOHI process
PWR 1 PWR 2 PWR 3
DECON OPTION
PWR 4
Fig. 18. Estimated cost of each rem
avoided PIJR decon: LOHI process
[] COST
Q SAVING
• NET BENEFIT
[] REM COST

74 C.J. WOOD
cn
,<
_1
O
a
u.
O
cn
z
2
.J
30
25
20
15
S
0
10000
8000
6000
4000
2000
PWR 1 PWR 2 PWR 3
DECON OPTION
PWR 4
ImmW1 ~IFjtltl ~ C~P@WI. 14BAO
IRIIJ. 8~'111rIM lq.Ul RJm.
Rjt~ IpffnIM NO IRIIB.
411 im#Ri WIWI I111AM ~ RIIJM.JtCm~NI'
Fig. 19. PNR cost-beneflt enalysls:
CAN-DECON process
PWR 1 PWR 2 PWR 3
DECON OPTION
PWR 4
Fig. 20. Estimated cost of each rem
avoided ~ decon: CAN-DECON process
[] COST
D SAVING
Im NET BENEFIT
[] REM COST

50-
40.
30,
20 ¸
10 ¸
Chemical decontamination technology' 75
COST SAVING NET BENEFIT
BWR FULL SYSTEM(FUELREMOVED)
CAN-DECONPROCESS
Fig. 21. Example of minimum, best
estimate and maximum best cases
9. FUTURE DECONTAMINATION STRATEGIES FOR NUCLEAR PLANTS
[] MI~MUM
[] BEST EST.
MAXIMUM
9.1 Current status
Conservative utility estimates show man-rem savings equivalent to the total annual
exposure of all U.S. nuclear power plants have been achieved from chemical
decontaminations. Even so, only about six plants per year are currently using the
technology. The main reason for the relative unpopularity of decontamination at the
present time is that fever major repairs of BWR recirculatlon systems are taking place, and
steam generator repairs are less common than five years ago.
There is no doubt that many utilities still regard chemical decontamination as a major,
expensive, tlme-consumlng exercise which is to be avoided whenever possible. Early
applicatlons were indeed fraught with problems, critical path delays, corrosion concerns
and waste handling dtfflcultles. In almost every case the desired reduction in fields was
achieved, but sometimes only after additional steps were taken, such as hydrolaslng. One
purpose of this review is to document the maturing of the technology to the point where it
Is a tellable option for outage planners to consider. It is now possible to accurately
predict the costs and the benefits for plant specific applications. Several utilities who
have carried out more than one decontamination, have demonstrated the typical "learning
curve" of increasing efficiency at each appllcation.
9.2 Future development
Effective chemical reagents are conunerctally available for most appllcatlons and
dramatic advances are not anticipated. Some developments concerning the oxidizing
processes Involve concerns about corrosion and partlculate residues, but the main technical
development will probably be in the area of waste processing. Several methods are under
development with the objective of reducing the volume of waste and avoiding current resin

76 C.J. \Vooo
solidification practices by producing an inert organlc-free solid residue. None of these
techniques has been fleld tested yet, and it will probably be two to three years before
they are implemented. The oxidizing decontamination processes using ozone are a promising
method of producing a low volume of waste. Studies of one such process are being carried
out by the Empire State Electric Energy Research Corporation (ESEERCO). The main problem
with processes using ozone in the past has concerned the production, stabillty and control
of the ozone itself; although hlghly effective on a laboratory scale, seallng up major
plant systems has been thought difficult.
9.3 Possible future strategies
The importance of decontamination technology to the utility industry in future years
will depend primarily on two issues: radiation exposure limits and major repair
requirements.
Regulations imposing lifetime exposure limits and reductions in annual exposure limits
to below 5 rem per indivldual worker are probably going to be introduced. These will
severely restrict the use of key workers who currently receive doses above 2 rems/year.
Even in situations where outage work can be carried out within a reasonable total dose
limit, decontamination may be beneficial as it will increase the productivity of key
workers ( 6__00 ) •
Up to the present time, steam generator replacements have been achieved without large
scale decontaminations, but recent estimates (61) show that considerable dose savings can
be achieved, particularly with full-system decontamination. In fact, decontamination may
prove to be essential at many plants, Just to keep within mandated dose limits.
Requirements for the inspection of BWR core internals may give added Justification for
full-system decontamination.
Improvements in other areas of radiation control technology also affect decontamination
considerations. Replacement of major in-core cobalt sources and improved water chemistry
specifications will result in lower radiation field buildup rates in the future. This
conclusion applies to both BNRs and PWRs. The cobalt-60 already deposited on out-of-core
surfaces is essentially fixed - the only significant removal process in normal operation is
decay at less than 15% per year. The net result is that fields in most plants older than 3
years have leveled off, but are not declining to any great extent. With full-system
decontamination, radiation fields will probably re-estsbllsh and level off at significantly
lower values than are currently typical.
It is concluded that utilities should consider chemical decontamination in the following
circumstances:
o Part-system decontamination in conjunction with significant outage work (typical
situation at the present time).
o Routine part-system decontamination at every outage to minimize individual
exposures (as at Commonwealth Edison BWR plants).
Assuming successful completion o£ work currently in progress to qualify full-system
decontamination, after 1990:
o Full-system decontamination with fuel removed in conjunction with major
repalr/replacement work.
o Full-system decontamination to achieve permanent reduction in fields. This would
involve one application with fuel in place or two with fuel removed. In the
latter case, the second application should be made two refueling outages after the
first. Assuming that relatively little activity is transferred from the dirty
fuel to new fuel after the first decontamination (which would seem to be a
particularly valid assumption for a ~ operating at elevated pH), all remaining
cobalt-60 on the system surfaces should be removed by the second
decontamination. Activity on the fuel is removed when the fuel is replaced.
Plant-specific cost-benefit assessments will be necessary to determine if either
of these options is Justified.

Chemical decontamination technology 77
ACKNOWLEDGMENTS
The author wishes to thank the following individuals for their contributions to this paper
and their generous assistance during the reviewing process.
Timothy Swan and David Brad bury, Central Electricity Generating Board, Paul Denault and Jerry
Moll, LN Technologies Thomas Beaman and Jeremy Smee, Niagara Technical Consultants, Robert
Mason and Ray Danlels, Bechtel/KWU Alliance, Eric Le Surf, Thomas Oliver and David
Schneidmiller, Pacific Nuclear Services~ Barry Gordon and bllng Wang, General Electric Company,
Douglas Vandergriff, EPRI/NDE Center, Costas Spalarls, Howard Ocken and Robin Jones, EPRI, plus
numerous individuals from the electric utilities who contributed significant technical input
during the EFRI decontamination seminars.
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78 C.J. W~,t~
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Chemical decontamination technology 79
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55. K. L. Atwood and P. G. Delozler, "Testing to Reduce Waste Volume from Full System
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56. J. E. Le Surf, "Feasibility of Full-System LWR Decontamination Project., Ibld.,
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