Though still focussed on converting UK’s stockpile of separated plutonium into Mixed Oxide (MOX) fuel – in line with the Government’s ‘preferred option’ for dealing with the material – the Nuclear Decommissioning Authority (NDA) has announced that it is now also working on additional/alternative re-use options submitted to the Authority following an invitation made to ‘third parties’ earlier this year.
In its web announcement on the 27th June 2012 – ‘Alternatives to re-use of plutonium as MOX fuel’ – the NDA has said that, after detailed discussions following the third party submissions, it has engaged General Electric-Hitachi (GEH) and Atomic Energy of Canada Limited (AECL) to provide further information regarding their respective proposals to use the PRISM Fast Reactor and the latest CANDU reactor. Whilst a CANDU reactor featured in the NDA’s 2010 plutonium credible options paper, the PRISM fast reactor was not included and has not so far been subjected to any public consultation.
Despite having already turned its back turning on the several viable immobilisation options which would see plutonium treated as a waste and put ‘beyond reach’ in terms of non-proliferation risk, last week’s announcement will be seen by some as open-mindedness by NDA. Others however will see it more as clutching at straws with a belated recognition of the problems and pitfalls that lie ahead for its preferred ‘re-use as MOX’ option – an option that would not only require the contentious construction of a new MOX plant and the raising of its estimated £5Bn – £6Bn costs, but also finding a market for the fuel – a market currently conspicuous by its absence. In addition, the NDA must still be smarting from recent humiliation suffered at the hands of the failed Sellafield MOX Plant (SMP) on which some £1.4Bn of tax-payers money was wasted.
Although the NDA’s announcement last week refers to alternatives to the plutonium re-use option, the submission by AECL proposing the use of its CANDU reactor does not itself offer much of an alternative. For whilst the new 700Mw Gen III reactor is designed to ‘burn’ conventional uranium fuel, its design can also accommodate MOX fuel and would therefore offer the same MOX option. This is not the first time that AECL has ventured into UK nuclear waters. Its ACR1000 LWR reactor was one of the reactor types to come under initial assessment by UK regulators via their new-build Generic Design Assessment (GDA) programme, but was withdrawn from the process by AECL in 2007.
AECL’s current submission is for the heavy water moderated and cooled Enhanced CANDU 6 reactor (EC6) which is still little more than a design concept. The IAEA’s 2012 ‘Status Report for Advanced Nuclear Reactor Designs – Report 68’ claims that in terms of build-time for a single unit, ‘the EC6 is targeted to achieve a construction schedule of 55 months from first concrete to in-service’. Such optimism does not accord with current UK or European experience, and last week the UK’s Office for Nuclear Regulation (ONR) confirmed to CORE that no approach has yet been made by AECL for a generic assessment to be made of the EC6 reactor and that such an assessment would at best take between 3-4 years.
By contrast, the submission by GEH for the use of its Power Reactor Innovative Small Modular (PRISM) reactor to be considered by the NDA does offer an alternative to MOX fuel and is apparently seen by some inside the industry as offering a more attractive proposition than following the MOX route. But whilst it would certainly replace the need for a MOX plant to be built, it would instead require the construction of at least a new conversion plant in which to convert Sellafield’s existing stockpile of plutonium dioxide to a metal form for use in PRISM. GEH’s claim that PRISM will also burn its own spent fuel suggests that some process or reprocessing plant will be needed if that is to be achieved.
The adoption of the PRISM fast reactor by the NDA would represent a significant U-turn by the Authority whose earlier high level assessment of fast reactors had concluded that ‘the maturity of the technology for the fuel, reactor and recycling plant are considered all to be low and that a concept unlikely to start until 2050 does not appear to meet the requirement for deployment within 25 years’. It would also indicate a reversal of the UK Government’s February 2011 view that fast reactors would not be commercially viable for the foreseeable future.
However, a softening of the NDA’s view was evident in an email to GEH on 29th November 2011 in which it confirmed an agreement to set a ‘hurdle for credibility’ – a challenge to demonstrate the credibility of PRISM. After robust lobbying by GEH and a further softening of attitude by the NDA, a Memorandum of Understanding with GEH was signed in early April 2012 under which the NDA agreed to pay an undisclosed sum for four months of further studies to be undertaken by GEH to demonstrate that PRISM was indeed a ‘credible alternative’ to the MOX option. Current engagement is focused on the technical and commercial credibility of GEH’s approach. As with the CANDU EC6 reactor, no PRISM fast reactor is currently built or in operation and the costs of building and operating such a reactor have been estimated as being some 50% higher than a conventional reactor.
PRISM is a small, modular, sodium-cooled reactor producing 311MW of electricity. GEH was quoted in March this year (i-Nuclear website) as saying that, as best value for the UK taxpayer, two modules would be built and combined to form one PRISM power block of 600+ MWe. Under a 60-year plan this ‘£multi-billion’ power block would be built at Sellafield within a timeframe of 10 years and ‘would burn through the UK’s huge stockpile of plutonium in about five years’. During the remaining 55 years of its plan, GEH claims that the spent fuel arising from the first 5 years of operation (during which the plutonium stockpile is consumed) would itself then be used to fuel the fast reactor.
The latest figures show that as at 31st December 2011 the UK stockpile of unirradiated separated plutonium – treated as a zero-value asset – stands at 113.3 tonnes and includes 27.9 tonnes of foreign-owned material which, under the terms of the overseas reprocessing contracts, remains destined for repatriation. Around 80% of the stockpile is derived from the reprocessing of magnox spent fuel in Sellafield’s B205 plant, with the remainder sourced largely from the reprocessing of oxide fuel in the Thermal Oxide Reprocessing Plant (THORP). Of the UK-owned plutonium, the NDA estimates that around 0.2% will have to be treated as waste because of historic chemical contamination and that a further 11 tonnes will need to be chemically cleaned to make it suitable for re-use.
Though the NDA’s original credible options for plutonium was limited to an assessment of its re-use as MOX fuel in reactors operating overseas – CANDU in Canada and Light Water Reactors (LWR) in Europe, the UK Government’s 2011 public consultation document widened the scope to the use of MOX fuel ‘either in UK or overseas reactors’. Today’s emphasis appears to have further shifted to the fuel predominantly providing the feedstock for the 10 new LWR reactors planned for the UK – the French EPR and Westinghouse AP1000. Current evidence however suggests that the prospect of achieving that new-build target is looking increasingly remote and, should the PRISM fast reactor proposal be rejected, attention will again have to be focused on securing overseas outlets for MOX fuel with all the attendant problems of markets, logistics and international opposition.
It remains unclear how the construction and operation of a PRISM fast-breeder reactor at Sellafield would affect the current plans by the NuGeneration (NuGen) consortium to build LWR reactors on a greenfield site owned by the NDA adjacent to the Sellafield site. Though an investment decision by NuGen is not expected to be made for its proposed Moorside site until 2015, its choice of the EPR or AP1000 reactor is expected in 2013. Both reactor types are capable of burning MOX fuel but their proposed construction will inevitably lead to questions as to how their operation can be justified alongside an operating PRISM at Sellafield.