L - KTH

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).