Guest contribution by David Lowry, Independent Consultant, London, UK

In January-March 2010 the United Kingdom completed the first shipment of foreign high activity radioactive waste (HLW) that was produced by the spent nuclear fuel reprocessing program. The waste was delivered to Japan on board of Pacific Sandpiper - the double-hulled ship that was specially designed for this purpose. It consisted of 28 steel canisters of HLW, each weighing half a ton, sheathed in 100-ton steel flasks. Pacific Sandpiper had left Sellafield, the site of the UK reprocessing facility THORP, on 21 January 2010 and reached the Rokkasho Mutsu-Ogawara Port in the Japanese Prefecture of Aomori on March 9, 2010.

The initial 14 ton cargo of vitrified HLW represents the first shipment of 1,850 canisters of foreign waste held at Sellafield that are due to be returned to Japan, Germany, Italy, Switzerland and the Netherlands by 2020, following their spent nuclear fuel being reprocessed - to separate potentially reusable plutonium and uranium from highly radioactive fission products at Sellafield - based on contracts dating back to the early 1970s. A second shipment with 28 canisters of vitrified HLW left Sellafield on 11 March 2010 and reached the Netherlands on 16 March 2010. It was delivered by one of the Nuclear Decommissioning Authority's vessels, Atlantic Osprey.

These first commercial repatriations of HLW (a much smaller amount of HLW was shipped to Japan more than a decade ago in a pilot trial shipment) have raised security concerns, some of which have a twenty year vintage (e.g. The Sea Shipment of Radioactive Materials: Safety and Environmental Concerns, by Edwin S. Lyman, then Scientific Director of the Nuclear Control Institute (NCI), Washington DC, 1999). This complex, expensive, and potentially hazardous activity is being carried out because Japan's utilities believed nearly forty years ago that they would want to re-use the plutonium created in the fuel loads in breeder reactor cores, and shipped the resultant irradiated nuclear fuel to the UK to be reprocessed. (See the IPFM Research Report "Japan's Spent Fuel and Plutonium Management Challenges" and "Status of Japan's MOX fuel program".) Power utilities in several other European countries did the same, including the then government-owned Central Electricity Generating Board (CEGB) and South of Scotland Electricity Board (SSEB) in the UK, and as a result, as of the end of 2008, there was a total stockpile of around 109 metric tons of separated plutonium in various forms stored at Sellafield. About 27 tonnes of this plutonium belongs to foreign customers, while the rest is the U.K. material.

The shipments of MOX and HLW to foreign customers remind us that the United Kingdom has no strategy of dealing with its separated plutonium. Although a small number of the utilities that own the plutonium still consider that in the long term their plutonium could provide a feedstock for MOX fuel in the future, in practice this store of nuclear explosive material is now seen as a massive, security-sensitive liability. (See "The Legacy of Reprocessing in the United Kingdom".)

On 21 May 2009 the responsible UK government ministry, the Department for Energy & Climate Change (DECC) had held a meeting with invited stakeholders. A few months later, taking into consideration views expressed at a NDA's National Stakeholder Group meeting in June 2009, the Government decided that, because of the many differing views, some of the key issues should be worked through in more detail and set out in publicly available discussion papers so that a wider audience could contribute to the development of official thinking in this area, prior to the Government launching a public consultation.

The first paper was published on 16 July 2009 and considered the factors, which could be important when judging one potential option for long term plutonium management against another. A second paper has also been published and considers decision methodology and a timetable for decision-making. Both papers are available at the DECC web site.

DECC 's papers set out the main plutonium management options as follows:

• Reuse. The plutonium could be reused in the manufacture of MOX fuel, burnt in a reactor, put in interim fuel storage before eventual disposal as spent MOX fuel. This option would require a new MOX fabrication plant and would raise complex issues, especially in terms of commercial viability. New nuclear build in the UK are expected to deliver reactors that are able to burn MOX but it is not certain that the ability to use MOX in the future would be sought by potential operators. There is also the possibility to sell MOX fuel to overseas utilities.
• Treat as waste. The plutonium could be immobilized in a safe and secure form before being disposed of as waste material. Again the issues are challenging as immobilization techniques have yet to be demonstrated outside the laboratory. Putting plutonium into a safe and secure form will produce a product with at least three times the storage volume requirements of the current plutonium stores. New interim stores would be needed before the immobilized plutonium could be disposed of. These are very likely to require the highest security standards, which would mean very high costs.
• Indefinite storage. Safe and secure storage is the only option available for the short term while thinking around the reuse or waste options is developed. A new storage facility is currently under construction. Storage beyond 30 to 50 years is likely to require a new plutonium store and probably a new treatment plant. It is known that the plutonium and the can in which it is contained degrade over time and packages will need to be reconditioned to allow continued safe storage.

In November 2009 the UK branch of the respected international nuclear disarmament group, Pugwash, published a study on the options for secure long term management of plutonium, "The Management of Separated Plutonium in the UK". The Pugwash suggestions, which can be simply summarized as "bury or burn it", repeat the first two UK government options in reverse order.

(Ed. Mycle Schneider and Pavel Podvig)