UK EPR Waste and Spent Fuel Disposability Assessment

November 10th, 2009.

AREVA and EDF obtained the support of the Nuclear Decommissioning Authority’s Radioactive Waste Management Directorate (RWMD) to perform an assessment of the higher activity wastes and spent fuel of the UK EPR to determine whether they would be suitable for disposal in a Geological Disposal Facility (GDF).

The results of this assessment are published today in «Summary of Disposability Assessment for Wastes and Spent Fuel arising from Operation of the UK EPR».

In its report RWMD conclude that, compared with legacy wastes and existing spent fuel, no new issues arise that challenge the fundamental disposability of the wastes and spent fuel expected to arise from operation of the UK EPR.
AREVA/EDF have carried out a review of the RWMD disposability assessment and have identified a number of detailed technical issues which would benefit from further consideration. These are addressed below:
Fuel Burn-up
As a bounding case RWMD has assumed that all UK EPR fuel assemblies would be subjected to the maximum burn-up of 65 GWd/tU which tends to overestimate the total heat output and radionuclide inventories of the spent fuel by about 30% compared to the average burn-up of the UK EPR fuel assemblies, which is expected to be around 48 GWd/tU.
Clad Failures
For the purposes of defining a worst-case radionuclide inventory of intermediate level operational waste streams, RWMD has assumed that the reactor primary circuit is contaminated by actinides and fission products escaping from a failed fuel assembly. RWMD has based its calculations on the pessimistic assumption that the reactor runs at all times with one failed fuel assembly.  For reasons of waste minimisation and operational efficiency the UK EPR would not operate in this way and serious clad failures would result in the removal and replacement of the faulty fuel assembly.
Spent Fuel Interim Storage
Following from RWMD’s assumption about fuel burn-up, RWMD has estimated that the spent fuel will need to be cooled for up to approximately 100 years for the heat output to reduce to an acceptable level before it can meet the surface temperature requirement of the GDF bentonite backfill. Based on wider international experience we believe RWMD figures to be pessimistic. Taking into account the average burn-up of spent fuel and employing a mix of spent fuel with different cooling periods the overall cooling period could be reduced. RWMD has also recognised in their report that the GDF concept has not been optimised for high burn-up fuel and that there are a number of areas where changes can be made.
AREVA/EDF agree with RWMD that these technical issues can be addressed through further joint working. We note the conservative nature of the assessment approach adopted by RWMD and are pleased that the Disposability Assessment confirms that ILW and spent fuel should be disposable and that no new issues are expected to arise.