A report by the UK’s Nuclear Decommissioning Authority (NDA) concludes that there are significant cost implications in a decision not to restart the Thermal Oxide Reprocessing Plant (Thorp) at Sellafield, driven by the commercial implications of existing BE and overseas light water reactor (LWR) contracts. The costs are estimated to be in the order of several hundred million pounds.

Thorp was shut down in April 2005 following the detection of a fracture in a pipe feeding one of two accountancy tanks. Investigations were carried out by British Nuclear Group Sellafield Limited (BNGSL) and the nuclear safety regulator, the Nuclear Installations Inspectorate (NII) which placed a number of actions on BNGSL before the plant will be allowed to restart operations.

The new report considers the major factors that will be taken into account when deciding whether or not the plant should be restarted. A range of non-restart and restart options were assessed. If Thorp were not to restart operations then a number of issues would arise, including a number of contracts with overseas LWR operators and with British Energy’s to reprocess AGR fuel. Establishing such arrangements would take significant time and be very costly, the report concludes. The non-restart option would also impact on the flexibility to deliver BE contracts and, although still manageable, would ultimately result in the need for storage of increased quantities of AGR fuel at Sellafield.

BNGSL evaluated a number of options for bringing the plant back into operation with the currently preferred option to make use of the undamaged accountancy tank for future operation. This would reduce the plant throughput compared to that previously achieved and require modification to some operating procedures and instrumentation, but still enable delivery of existing customer contracts. BNGSL are developing plans to look at the options for repairing and making use of the damaged accountancy tank, but believes that it is possible to make a safety case for the use of the plant using only one accountancy tank.

A number of mandatory regulatory, BNGSL and NDA requirements must be met to enable a restart to be considered and separately from the considerations of potentially restarting Thorp, the NDA is planning to launch a comprehensive long term spent nuclear fuel management review in April which will look at all the options for UK spent fuel including reprocessing, ongoing wet storage, dry storage in new purpose built stores and dry cask storage. The future role of Thorp in managing spent fuel will be considered as part of this review, the NDA says.