Solid Radioactive Waste Strategy Report.pdf - UK EPR

EPR UK
N° NESH-G/2008/en/0123
REV. A PAGE 81 / 257
8 DECOMMISSIONING WASTE
This section examines the nature and quantity of radioactive waste to be generated through the
decommissioning of the nuclear island of a single UK EPR unit. The decommissioning
methodology is outlined. It is explained how the design of the UK EPR will facilitate its
decommissioning. This study does not take into account the conventional waste or nonradioactive
waste generated from the dismantling of the conventional island plant (principally the
turbine house and electrical switchgear) or the administrative buildings and non-nuclear site
infrastructure. This section does not take into account decommissioning of the ILW and Spent
Fuel Interim Stores.
8.1 EPR Plant Inventory and Radiological Characteristics After 60 Years of
Operation
8.1.1 EPR Design Features for Decommissioning
The UK EPR has been designed with maintenance and decommissioning in mind. The future
decommissioning of the EPR has been planned and optimised at the design stage. Thus the
design will enable decommissioning to be performed to minimise radiation doses to workers and
minimise radioactive waste generation. In particular, the design incorporates the following
features:
· Choice of materials of construction to minimise activation;
· Optimisation of neutron shielding;
· Optimisation of access routes to nuclear areas;
· Reactor systems design;
· Ease of removal of major process components;
· Submerged disassembly of reactor pressure vessel;
· Modular thermal insulation;
· Fuel cladding integrity;
· Design for decontamination;
· Prevention of contamination spread;
· Minimisation of hazardous materials;
· Summary of design principles.
These are discussed in more detail below.
8.1.1.1 Choice Of Materials Of Construction To Minimise Neutron Activation
Materials with a minimum propensity to become radioactive through activation (directly or
through their corrosion products) have been selected for equipment subjected to irradiation.
Cobalt-59, a stable isotope, is present in stainless steel and other alloys. Upon activation by
neutrons it transmutes into cobalt-60 which is an intense gamma radiation emitter. Although
cobalt-60 has a relatively short half life of 5.27 years, its presence is significant for
decommissioning, if not for long term waste management. Therefore, elimination, wherever
possible, of the use of alloys containing high cobalt levels in areas subject to neutron irradiation