Sizewell B management of intermediate level waste

EDF Energy Nuclear Generation Ltd, the operator of Sizewell B Power Station, has requested that the Office for Nuclear Regulation (ONR) agrees to a proposed strategy for the long term management of intermediate level waste ion exchange resins.

Background

Spent radioactive resin is accumulated at Sizewell B from routine operations. A proportion of the resin is designated as intermediate level waste (ILW) and this material is currently stored in tanks on site.

Sizewell B has developed a proposal to dry the resins and store them in thick walled cast iron containers, know as Mosaik casks, on site prior to final disposal. These containers are used in Germany to store radioactive wastes pending disposal, and have been designed to meet the requirements of the German disposal system. This is a different concept to that proposed for the UK and ONR is currently considering a series of proposals submitted by another licensee (Magnox Ltd) to store and dispose of wastes in the Mosaik casks.

This proposal was correctly categorised by the licensee, in accordance with its arrangements, as being of lower nuclear safety significance, so would not normally require the formal agreement of ONR. However, in order to ensure consistency of approach to the regulation of waste management proposals across the industry, ONR has decided that this proposal should not be implemented without formal agreement (i.e. issue of a licence instrument).  

Assessment and inspection work carried out by ONR in consideration of this request

Inspectors from ONR have held a number of meetings with the licensee to reach agreement on a Paper of Intent that sets out a proposed strategy for the long term management of ILW ion exchange resins at Sizewell B. 

Matters arising from ONR’s work

The Paper of Intent includes the following changes as a result of discussions with ONR.

  • The proposal makes a clear commitment to produce a radioactive waste management safety case and obtain a final Letter of Compliance from the Nuclear Decommissioning Authority’s Radioactive Waste Management Directorate for the Mosaik casks prior to bulk filling them with ILW resin.
  • In the event that a final Letter of Compliance cannot be obtained prior to bulk filling, a reversibility safety case will be provided as a fall-back strategy, to demonstrate that the ILW resins can be safely removed from the Mosaik casks, if necessary.
  • A safety case for the interim storage on-site of the loaded Mosaik casks will be submitted for ONR Agreement prior to moving from active commissioning to bulk filling them with ILW resin.

Conclusions

An acceptable strategy has been developed by the licensee for the long term management of ILW ion exchange resins at Sizewell B.

Recommendation

Agreement to the proposed strategy for the long term management of ILW ion exchange resins should be given by issuing Licence Instrument 528 to the licensee.

A further specification should be issued, in due course, requiring ONR Agreement to the safety case for the interim storage on-site of the loaded Mosaik casks.

The full Project assessment report can be read here.