L - KTH

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.