2009 Report to Government on National Research and

Magnox Fuel
A.20 Magnox fuel consists of uranium metal in a magnesium-alloy cladding. The
NDA's current strategy, as embodied in the Magnox Operating Plan, MOP8
(NDA, <strong>2009</strong>e) is <strong>to</strong> reprocess all spent Magnox fuel. The UK Inven<strong>to</strong>ry indicates
that around 5,800 <strong>to</strong>nnes (heavy metal, tHM) of Magnox fuel remains <strong>to</strong> be
reprocessed (Defra/NDA, 2008b). Some of it is in operating reac<strong>to</strong>rs, some in
temporary dry s<strong>to</strong>rage in shut-down reac<strong>to</strong>rs and in the Wylfa dry s<strong>to</strong>re, and the
rest is s<strong>to</strong>red under water, mainly at Sellafield. The reprocessing strategy is
contingent upon the Sellafield Magnox Reprocessing Plant continuing <strong>to</strong> operate
until all Magnox spent fuel that can be reprocessed has been. Given the elderly
nature of the Magnox Reprocessing Plant, considerable effort and resource is
being expended on keeping it operating but the possibility of chronic or acute
failure before reprocessing is completed (currently projected as 2016) must be
considered (CoRWM doc. 2520).
A.21 Accordingly, contingency plans for any un-reprocessed Magnox fuel are required
(CoRWM doc. 2520). The NDA is investigating these (NDA, 2008d; CoRWM
docs. 2418, 2500, 2624) along three principal lines, namely:
• Reprocessing through the Thermal Oxide Reprocessing Plant (THORP) with
the recovered uranium and plu<strong>to</strong>nium and the associated HLW being
managed in the same way as other THORP products. This would be difficult
and costly, entailing modification <strong>to</strong> the THORP head end, and would require
significant R&D for the necessary adaptations of the THORP process. It
would also disrupt and prolong the THORP programme. For these reasons
this option is currently 'shelved' by the NDA.
• Dry s<strong>to</strong>rage followed by geological disposal. This necessitates drying the
spent fuel before placing it in one of the preferred forms of dry s<strong>to</strong>rage (para
A.34). An issue is how dry <strong>to</strong> make the fuel. There is at present no capability
in the UK for drying spent fuel of any kind on a large scale but there is
considerable experience in other countries. The work at Hanford in the USA,
where metal fuels have been successfully dried as a prelude <strong>to</strong> dry s<strong>to</strong>rage
and eventual disposal, is of relevance <strong>to</strong> Magnox fuel. Although the Hanford
process has been shown <strong>to</strong> be viable, even for seriously corroded fuel
elements, it is unlikely it could be transferred <strong>to</strong> the UK for Magnox fuel
without substantial R&D (CoRWM doc. 2520). The Hanford experience is
with smooth zircaloy clad metal fuel. In contrast, Magnox fuel cladding has
large fins which result in a much higher surface area. Magnox fuel cladding
is considerably more reactive than zircaloy and hence is much more
susceptible <strong>to</strong> corrosion in water. In addition, carbonaceous deposits, which
may be particularly difficult <strong>to</strong> dry out, are often found on Magnox fuel. Due
<strong>to</strong> the potential for continued reactivity of uranium metal further R&D would
be needed on packaging the dried product for s<strong>to</strong>rage and geological
disposal in a UK facility (CoRWM doc. 2500). Our understanding is (CoRWM
docs. 2418, 2523, 2624) that the NDA is funding some R&D in<strong>to</strong> the drying
of Magnox fuel and in<strong>to</strong> packaging it for disposal, and will evaluate this
option shortly with a view <strong>to</strong> pursuing it further.
• Encapsulation in preparation for interim s<strong>to</strong>rage and geological disposal.
Experience with encapsulation of relatively small amounts of reactive metals
such as uranium has shown that existing cement formulations would not be
CoRWM Document 2543, Oc<strong>to</strong>ber <strong>2009</strong> Page 103 of 151