Managing spent fuel at Sizewell B 


British Energy has issued a consultation document entitled “Managing spent fuel at Sizewell B” which can be downloaded by application to:-

The document was submitted to a public consultation held in the Sizewell Sports Centre on 11 November 2009.

The Sizewell B spent fuel pond is expected to be full by 2015, after only 20 years of its anticipated 40 years operational life from 1995 to 2035. The problem has occurred because the design packing density was reduced by NII for safety reasons. Freshly removed fuel assemblies have to be placed in the pond well away from the last previously removed fuel assemblies to avoid any potential criticality. The placing of the spent fuel assemblies is subject to computer analysis, thus the additional space is utilised.


Four remedial options were considered, viz.,

Dry storage in casks

Dry storage in vaults


Wet storage in a new fuel pond

Dry casks

The option selected is to place the entire spent fuel arising throughout the 40 years operational time in dry casks which will be accommodated in a “mausoleum” around 100 m x 50 m by 30 m high. If in metal casks there will be 120 and in concrete there will be 190 of them in total. 

The residence time in the pond is 10 years, so that as some of the fuel will have been in the pond for around 11 to 12 years, some can be transferred to dry casks as soon as they are constructed. So provided the dry casks are ready by 2015 there need be no operational interruptions.

In the US the dry casks are stored in outdoor “cemeteries”, whereas in Belgium and Switzerland they are accommodated in “mausoleums” suitably provided with air vents allowing cooling air to circulate.

Removal to a repository

The Sizewell B management see this as a local initiative to solve an impending problem and have no mandate to plan the eventual transfer of the contents of the casks to the final underground repository. It is anticipated that there will be no repository until 2080, nor will one be needed before then, because the assemblies in the dry casks will need time to cool from when the last spent fuel is extracted from the pond in 2045.

The dry casks are expected to endure for 100 years after which the contents would have to be re-housed in replacement containers. Should the same practice be adopted for Sizewell C and D, which with operational times of 60 years and a 20 years residence thereafter due to the incorporation of higher enriched fuel, the last cask to be filled would be at the turn of the century.

The consensus of the consultative body at the meeting was that the Sizewell site is the final repository and would be used throughout the 22nd Century..

Local compensation

CoRWM envisaged that communities would be offered a considerable sum for local projects to compensate them for the poor image the placing of a neighbouring repository would engender. As it is likely that Sizewell will host three enormous buildings housing 800 casks from the end of the century, it was put to the Sizewell B management that such compensatory payments would be applicable to neighbouring communities.

John Busby 13 November 2009