Taking the power out of plutonium
Lynda Warren | 09/02/2011
The UK’s Department of Energy & Climate Change (DECC) has just published its long-awaited consultation on options for dealing with stocks of plutonium: Management of the UK’s Plutonium Stocks: A Consultation on the Long-Term Management of UK owned separated civil Plutonium (Issued 7 February 2011 and available from the DECC website.
The UK has a stockpile of about 110 tonnes of civil separated plutonium, 84 tonnes of which is UK owned and 28 tonnes foreign owned. The plutonium comes from the reprocessing of spent nuclear fuel, i.e. fuel that has been used in a nuclear reactor. Reprocessing started over 50 years ago and was initially carried out to produce plutonium for defence purposes. During the 1960s government attention turned to the possibility of using fast nuclear reactors to provide nuclear power and thereby mitigate the risk of fossil fuels running out. Fast reactors require plutonium to start up so surplus plutonium from the defence programme was reclassified as civil and stored for potential future use. Over time the stockpile has grown with the addition of plutonium recovered from reprocessing of spent nuclear fuel from nuclear power stations. In the event, it was decided not to proceed with research into commercial fast reactors on grounds of cost. The plutonium stockpile continued to grow nevertheless, partly because of the technical need to reprocess fuel used in the Magnox type of nuclear power station and partly because of contractual obligations to reprocess overseas fuel.
For the time being the plutonium stockpile is stored in specially designed facilities and it will be possible to maintain the status quo for some time. In the long term, however, storage is not a satisfactory solution, not least because it is expensive and entails exposing workers to radiation risks when refurbishment is needed. More importantly, perhaps, storage does not solve the problem and there is a danger that we will be passing responsibility for managing this hazardous material to future generations who have had no say in its creation in the first place. Finally, we cannot ignore the fact that we would be reducing potential threats from terrorism if the plutonium were disposed of once and for all or at least put into a form that would make it far less attractive to terrorists.
The consultation paper sets out the Government’s proposed approach for addressing these issues in the long term. Chapter 3 identifies and discusses the various options. These are burning the plutonium in a new generation of fast reactors; using it as a fuel in other types of reactor; immobilisation followed by disposal; or continued long term storage. The first of these options is largely discounted by Government on the grounds that fast reactor technology for commercial stations is still many years away at best. It is noted, however, that this decision could be re-opened at any time before the plutonium is put beyond reach.
Reuse as a fuel would be possible if the plutonium were converted into a Mixed Oxide fuel (MOX). This option is the only one that makes use of the embedded energy in the plutonium. It is estimated that if all the plutonium was converted to MOX it would generate enough fuel to power two nuclear power stations for about 60 years. MOX conversion is technically achievable and would only require application of current processes. However, UK experience with the MOX Plant at Sellafield (SMP) has not been satisfactory to date and very low throughput s have been achieved. SMP has a large backlog of contractual obligations and DECC conclude that a reuse strategy would only be viable if a new MOX Plant was constructed – at considerable cost. Furthermore, the MOX spent fuel would still need to be managed and this presents particular problems of its own for technical reasons.
If plutonium is to be disposed of in a geological disposal facility it will first be necessary to immobilise it by converting it into a stable form that will not readily disperse into the environment. There are several options for immobilisation but none is full developed and all are likely to negatively impact on the disposal of waste. Options include immobilisation in glass or in ceramic forms.
Plutonium is currently stored at Sellafield and Dounreay and present plans assume its continued storage there until 2120 and 2078 respectively although it is likely that plutonium stocks will be consolidated at one site during this period. There is currently no provision for ongoing storage beyond these dates.
The consultation paper goes on to state a number of conditions that will have to be satisfied before any final decisions are made. These are that the option is achievable and deliverable; capable of meeting health & safety, environmental, non-proliferation and security requirements; and demonstrable value for money.
Government’s preliminary view, however, is that the best prospect for the long term management of plutonium is through reuse as MOX fuel either in the UK or overseas.
The consultation document invites responses to seven questions as follows:
- Do you agree that it is not realistic for the Government to wait until fast breeder reactor technology is commercially available before taking a decision on how to manage plutonium stocks?
- Do you agree that the Government has got to the point where a strategic sift of the options can be taken?
- Are the conditions that a preferred option must in due course meet, the right ones?
- Is the Government doing the right thing by taking a preliminary policy view and setting out a strategic direction in this area now?
- Is there any other evidence Government should consider in coming to a preliminary view?
- Has the Government selected the right preliminary view?
- Are there any other high level options that the Government should consider for long-term management of plutonium?
The closing date for responses is 10 May 2011.
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