Solid Radioactive Waste Strategy Report.pdf - UK EPR

EPR UK
N° NESH-G/2008/en/0123
REV. A PAGE 82 / 257
has been implemented. In particular the use of stellite for hard facing surfaces has been
minimised.
Where complete elimination of cobalt containing materials cannot be achieved, low cobalt
content alloys have been selected. Alloy 690 has been selected instead of alloy 600 for the
steam generator tubes. This minimises the quantity of cobalt in the corrosion products
circulating in the primary system. The amount of cobalt in some steel components has been
limited to 6 ppm.
8.1.1.2 Optimisation Of Neutron Shielding
Shielding and barriers have been optimised to minimise the activation and contamination of
equipment. For example, the UK EPR design incorporates neutron shielding around the core.
This shielding reduces neutron activation of material and equipment in the vicinity of the core
and thereby simplifies the clean-up of the structure while minimising the volume of active waste.
The neutron shield will become activated during service. The neutron shield is modular by
conception and has been designed for ease of removal from the reactor core.
8.1.1.3 Optimisation Of Access Routes To Nuclear Areas
The design of access points in nuclear areas, handling equipment and access routes has been
optimised in order to reduce the expected duration of exposure of workers (provisions facilitating
removal of components and structure, and facilitating personnel access). The design makes use
of international experience from past reactor decommissioning projects and measures taken to
facilitate maintenance (for example, feedback from the replacement of steam generators in
currently operating PWR plants).
8.1.1.4 Reactor Systems Design
The design of reactor systems (core instrumentation, steam generators, reactor coolant pumps,
pressuriser, heat exchangers etc.) has been optimised to facilitate decommissioning.
Systems have been designed to minimise the creation, transportation and deposition of
contamination.
8.1.1.5 Ease Of Removal Of Major Process Components
The major process components within the reactor building (and reactor building access routes)
have been designed to allow their removal from the reactor building each as a single item
without the need for size reduction. This can allow their removal to other facilities for size
reduction, waste conditioning and packaging.
8.1.1.6 Submerged Disassembly Of Reactor Pressure Vessel
The design of the reactor compartment (fitted with a lost steel framework embedded in the
concrete) makes it possible to fill the reactor compartment with water to allow the pressure
vessel to be disassembled whilst submerged. The reactor compartment is lined with
decontaminable steel to prevent contamination of its concrete structure.