The Fukushima accident has brought into question the way used nuclear fuel is handled at the reactor site (see used-nuclear-fuel-what-happens-after-fukushima-) but so far the issue has largely been one of whether the fuel should be removed more quickly from the reactor site and put into centralised storage. The wider issue, of course, is what happens to the used fuel subsequently. If we take the three countries whose nuclear programmes have been most adversely affected by Fukushima, namely Japan, Germany and Switzerland, each has always been actively involved in reprocessing used fuel and subsequently the use of recycled uranium and/ or plutonium in reactors. In addition, the United States is gradually moving away, it seems, from a previous clear preference for the ‘once through’ nuclear fuel cycle, with the termination of the Yucca Mountain repository project. And the United Kingdom, a country with over 100 tonnes of separated civil plutonium in storage, is once again actively considering new reactors. Yet the Sellafield MOX Plant (SMP), which could fabricate fresh reactor fuel from this inventory, is now closing. So there is clearly plenty of reason at this point also to reassess the way in which used fuel is dealt with.
The advantages and disadvantages of used nuclear fuel reprocessing have been debated since the dawn of the nuclear era. There is a range of issues involved, notably the sound management of wastes, the conservation of resources, economics, hazards of radioactive materials and potential proliferation of nuclear weapons. Every position seems to have a strong counter-claim made by an opposing party. Sifting through these is not easy.
As a start, it is important conceptually to distinguish reprocessing from recycling. Reprocessing is stage one: the separation of uranium and plutonium out of used fuel and conditioning of the remaining material as waste. Recycling is then stage two: the use of the uranium and plutonium from the reprocessing plant, which can be either as mixed oxide (MOX) fuel or reprocessed uranium (RepU) fuel in current reactors or as fuel for future Generation IV reactors. Reprocessing effectively sets up the possibility of recycling. This doesn’t necessarily have to follow, but in practice, the two stages are bound together as reprocessing will likely only be undertaken with a view to eventual recycling. (The recent UK experience may offer an alternative to this; it has carried on reprocessing used fuel without any clear future use).
Although world uranium resources are extensive, many people do not them see them as any lasting solution to world energy needs. If nuclear power expands rapidly, the quantity of uranium mined and processed each year may have to rise from the current 50,000 tonnes per annum, to 100,000 tonnes and beyond. Reprocessing arguably contributes to sound stewardship of uranium resources by allowing the recycling of reusable materials, which, introduced as MOX fuel and RepU can save around one quarter of uranium needs. It has to be seen in a holistic sense as a complete waste management system. Although it still involves a repository for materials where there is no future use, it also envisages re-use of materials (albeit only most extensively in the next generation of reactors).
Much of the opposition to reprocessing centres on a huge amount of hype about plutonium created by anti-nuclear forces. Yet despite being toxic both chemically and because of its ionising radiation, plutonium is far from being ‘the most toxic substance on earth’ or so hazardous that ‘a speck can kill’.
The other aspect of plutonium which raises the ire of nuclear opponents is its alleged proliferation risk. Opponents of the use of MOX fuels commonly state that such fuels represent a proliferation risk because the plutonium in the fuel is said to be ‘weapons-useable’. But MOX is a mixture of uranium and plutonium oxides, with the plutonium being very much in the minority. For light water reactor fuel, the plutonium content is typically around 5%. MOX cannot possibly be used in nuclear weapons or nuclear explosives. To separate the plutonium content from MOX fuel elements would be a major undertaking, similar to reprocessing.
Another critique of reprocessing centres around the transportation of materials, notably the shipments of used fuel from Japan and other countries to the reprocessing facilities in France and the UK and the subsequent return of MOX fuel and high level wastes. This is very much a special case of the difficulties of transporting any fissile materials today but, in reality, involves no greater risk to human health and to weapons proliferation.
Finally, the reprocessing facilities themselves have come under attack through alleged risk to populations near and far through contamination of the air and sea. Studies have so far failed to show any conclusive risk to either the workforces or the local population: the leukaemia clusters found near Sellafield in UK have been explained by alternative causal factors. Despite the lack of data, and without any acceptance that current or past levels are harmful, both French and UK plants have stringent targets for reducing the concentrations of radionuclides in the nearby seawater (see ne-atlantic-discharges-april-2011).
There was a strong push towards reprocessing in the 1970s. But as things transpired, the pressure on uranium resources was very much less than expected and prices remained low in the period up to 2003. This was caused by the discovery of several new uranium deposits, the entry onto the world market of large quantities of uranium from the dismantling of nuclear weapons, and the slower growth of nuclear power than had been expected. There became little incentive to develop fast breeder reactors, particularly as these present major engineering challenges that could prove expensive to resolve. Nevertheless, since the late 1970s, around 30% of spent fuel arising from commercial nuclear reactors outside the former Soviet Union and its satellite states have been covered by reprocessing contracts with plants in France and the UK. Without fast breeder reactors, there has been an accumulation of separated plutonium stockpiles. So far, some 80,000 tonnes (of 280,000 tonnes discharged) of used fuel from commercial power reactors has been reprocessed.
MOX fuel was introduced mainly to reduce the stockpiles of plutonium, which were building up as spent fuel reprocessing contracts were fulfilled. MOX was therefore an expedient solution to a perceived problem, which had been created by changed circumstances. The MOX era, however, may pass relatively quickly, even if plutonium stockpiles worldwide are not substantially reduced, if the mooted move to Generation IV reactors takes place. This will largely depend, however, on nuclear power developing rapidly with the current generation of reactors.
Looking at the immediate term, EDF will continue to send for reprocessing 850 tonnes of its 1200 tonnes of used fuel discharged each year from its reactors. This is then introduced as MOX, saving about 2000 tonnes of fresh uranium each year. The remainder is preserved for later reprocessing to provide the plutonium required for the start-up of Generation IV reactors, the prototype of which is envisaged by 2020. In Japan, the Rokkasho-mura reprocessing plant has been delayed, but even after Fukushima, it is envisaged that 16-18 reactors will eventually be loaded with MOX fuel. A MOX fuel fabrication facility is also under consideration there, but until it opens, fabrication of MOX for Japan will take place in Europe.
In the United Kingdom, the plant reprocessing Magnox fuel is closing following the permanent shutdown of the four remaining reactors it serves, and uncertainty surrounds the future of the THORP reprocessing plant after the closure of SMP. Nevertheless, the UK has a substantial inventory of both separated reactor-grade plutonium (over 100 tonnes) and depleted uranium (about 60,000 tonnes). This inventory has been the subject of several studies. A Royal Society report in September 2007 recommended that the plutonium be used in MOX fuel. This will depend on persuading reactor operators in the UK (including those running any new reactors) to adopt this as a fuelling strategy; it is by no means certain that they will.
Russia may eventually achieve its stated aim of closing its fuel cycle, although it has so far achieved very little in this direction. Plans for expanding the Mayak reprocessing facility or building a second plant, as well as a fuel fabrication facility, have so far come to naught. Nevertheless, its revival in the Russian nuclear industry and Russia’s interest in playing a major role in the world suggests that it may return to investing in reprocessing.
It is in the United States, however, that there is now an apparent increased interest in reprocessing. It is reassessing its previous policy, which was set strongly against this and subsequent recycling of recovered materials since the Carter Administration in the late 1970s. The decision to introduce MOX fuel from ex-weapons plutonium in civil reactors was an important element in this; the first assemblies have been successfully used in reactors operated by Duke Power. Both the United States and Russia have declared 34 tonnes of military plutonium as surplus to requirements and have reached a framework agreement on the disposition of this as MOX. For this purpose, MOX fabrication plants were planned in both the USA and Russia, each with a capacity of 2 tonnes of plutonium per annum. This may displace a combined 840 tonnes of uranium per annum or a total of 14,300 tonnes over the life of the programme. The Russian plant has now been abandoned, but the US plant, the MOX Fuel Fabrication Facility (MFFF), is now under construction with commissioning planned in 2016.
In November 2005 the American Nuclear Society released a position statement in favour of fast reactors that envisages on-site reprocessing of used fuel from fast reactors, since ‘virtually all’ long-lived heavy elements are eliminated during fast reactor operation.
The Global Nuclear Energy Partnership (GNEP) programme, announced by the US Department of Energy in early 2006, fitted in closely with this. It is now somewhat uncertain where this programme is going, but without the Yucca Mountain repository, the issues it considered have to be addressed. Used fuel inventories are rising without any place to go. One priority has therefore been the development of new reprocessing technologies. One of the concerns when reprocessing used nuclear fuel is ensuring that elements separated are not used to create a weapon. GNEP enables countries to collaborate on proliferation-resistant processes.
The second main technological development envisaged under GNEP is the advanced recycling reactor—basically a fast reactor capable of burning minor actinides. Thus, used fuel from light water reactors would be reprocessed at a recycling centre and the transuranic product transferred to a fast reactor on site, which both produces perhaps 1000 MWe of power and incinerates the actinides. A key objective of this programme is to obtain design certification of a standard fast reactor from the US Nuclear Regulatory Commission.
Nearly all the new reactor models being developed under the Generation IV and INPRO projects have closed fuel cycles recycling all the actinides. Although part of the motivation remains making savings in the use of the (now more expensive again) natural uranium resource, the key today is saving on used fuel inventories and developing ways to deal with the existing volumes of fuel created by commercial nuclear power to date.
Looking beyond MOX fuel and advanced reprocessing and the attendant reactors, the upward movement in uranium prices since 2003 suggests that utilities owning inventories of RepU will look once again at utilising these. The greater expense at the conversion and enrichment stages may now be outweighed by the substantially increased prices for fresh fuel. EDF is at centre stage here, owning significant quantities of RepU as a strategic asset.
To summarise, it seems clear that reprocessing and recycling remains a live issue in the nuclear sector, and indeed has apparently recently had a push from several quarters to pursue it more vigorously in the future.
Steve Kidd is deputy director general of the World Nuclear Association, where he has worked since 1995 (when it was still the Uranium Institute). Any views expressed are not necessarily those of the World Nuclear Association and/or its members.