THE REPROCESSING–RECYCLING OPTION AS A SOLUTION TO SPENT NUCLEAR FUEL MANAGEMENT

Alongside the development of its civil nuclear programme, France has opted to reprocess spent fuel. At present, this operation is carried out at a large industrial facility based at La Hague in western France. Two plants known as UP2 800 and UP3 are currently being operated on the La Hague site by the French AREVA group, with an annual capacity of 1700 t of spent fuel. Since 1976, 21 600 t of spent fuel have been reprocessed in these plants, which in energy terms corresponds to the equivalent of four years of oil production in Kuwait. This industrial facility has also led to the formation of a major techno-logical and economic area and is currently directly responsible for more than 8000 jobs. Reprocessing operations have been performed on behalf of the French electricity operator, EDF (11 700 t), but also for foreign clients, and countries such as Belgium, Germany, Japan, the Netherlands, Sweden and Switzerland (9900 t) have concluded reprocessing contracts with AREVA since the mid-1970s.

2.1. The principle behind spent fuel reprocessing

After irradiation in a power reactor, spent fuel still contains 97% reusable materials which are capable of providing energy (the spent fuels from

BACK END OF THE NUCLEAR FUEL CYCLE: FRENCH CHOICES

pressurized water reactors contain 96% uranium and 1% plutonium). The reprocessing procedure used in France is the PUREX process, and this entails separating these materials from the final waste, which represents the remaining 3% and consists of minor actinides and fission products. This waste is currently packaged in strong vitrified matrices which are specially adapted for long term waste management.

The uranium contained in the spent fuel contains slightly more U-235 (1%) than natural uranium (0.7% U-235); it is therefore still valuable in energy terms. Direct recycling of the reprocessed uranium (URT) is technically possible, and reloads of fuel assemblies manufactured using URT have already been successfully recycled in French reactors. For foreign clients of AREVA, much of the uranium requiring reprocessing has also been recycled by these clients in their reactors (4750 t out of 7350 t of uranium processed), and the rest will be recycled over the coming years. This is, therefore, a tried and mature technology.

The plutonium also has a high energy value (just one gram of plutonium can produce as much electricity as a tonne of oil) and it can also be recycled on an industrial scale via the use of mixed oxide fuel (MOX), either in the 20 French pressurized water reactors operated by EDF which use 30% MOX, or in foreign countries which have opted for the reprocessing–recycling option, e.g. Belgium, Germany and Switzerland. Since the La Hague reprocessing plant started operation, 118 t of plutonium have already been recycled in this form. A total of 35 European nuclear power plants have been authorized by their national safety authorities to use MOX type fuel. AREVA has a new plant, MELOX, in the south of France, which is responsible for manufacturing this MOX fuel. In summary, France now has a coherent, industrially mature and competitive set-up for its reprocessing and recycling technologies.

2.2. Benefits of spent fuel reprocessing

2.2.1. Rational management of natural uranium resources

The uranium and plutonium present in 1 t of spent fuel have the same energy value as 20 000 t of oil. The reprocessing–recycling strategy therefore offers a real potential for solving the problem of resources. It means that savings of approximately 20% can be made on the natural uranium resources needed to operate the French nuclear reactor network.

While this aspect may have seemed of secondary importance or outdated only a few years ago in a market where prices were very low, recent changes in the price of uranium confirm the benefits of reprocessing for the rational management of resources. The price of uranium increased from US $6 to

US $45 per pound of U₃O₈ at the time of the first oil crisis and dropped back down to US $7 per pound of U₃O₈ in December 2000, but was at around US $41 per pound at the end of April 2006. Furthermore, faced with the prospects of a developing nuclear power sector — in countries such as China or India, for example — and the need to control emissions of greenhouse gases, the reprocessing–recycling option provides an answer in advance of the development of the new generation of fast neutron reactors.

2.2.2. Optimized management of the back end of the fuel cycle

The reprocessing option has also allowed the optimization of the back end of the nuclear fuel cycle. Spent fuels are collected on a centralized site — the La Hague site — prior to being reprocessed. This means that the amounts of spent fuel present on the 20 nuclear sites currently operated by EDF are limited, and this facilitates the management and monitoring operations on these sites.

Reprocessing also results in a reduction of the space required for interim storage of the unloaded fuel. The plutonium from seven uranium oxide fuel assemblies is required in order to produce one MOX fuel assembly. A small amount of spent fuel is therefore still placed in interim storage. The policy of in-line plutonium recycling via the manufacture of MOX fuel and ongoing devel-opments with regard to burnup rates leads to a near balance in the levels of spent fuel which are currently in interim storage at La Hague awaiting reprocessing.

2.2.3. Economic management of the back end of the fuel cycle

A great deal of international research work has been done to examine the costs associated with the back end of the fuel cycle, especially in comparing the reprocessing–recycling solution with the open cycle strategy, which involves direct disposal of the spent fuel. The majority of these studies conclude that there is a slight difference between the cost of electricity produced by nuclear means in an open or closed cycle. This is due to two terms with opposite effects when calculating the cost of electricity. In the case of direct disposal there are no reprocessing costs, but the fuel requires longer interim storage for cooling purposes and the disposal facilities are more expensive. To be more specific, an economic assessment conducted in France in 2003 on reference costs for electricity production showed that, in the case of a series of 10 third generation reactors of the European pressurized water reactor (EPR) type, assuming a discount rate of 8%, the cost per kilowatt hour of nuclear electricity is €28.4/

MW·h, with fuel cycle costs representing €5.1/MW·h, or 18% of this figure, and

BACK END OF THE NUCLEAR FUEL CYCLE: FRENCH CHOICES

reprocessing accounting for €0.9/MW·h, or approximately 3% of the reference cost. In summary, the recycling–reprocessing operations result in savings of 20% to 30% on raw materials set against an increase in production costs of only 3%.

2.2.4. Safe and sustainable management of the resulting final waste

Finally, reprocessing has led to waste packaging methods that are both compact and effective in the long term. For the French nuclear reactor network as a whole, and assuming that these facilities will have an average operating life of 40 years, a maximum of approximately 80 000 m³ of intermediate level long lived waste will be produced, along with 6300 m³ of high level vitrified waste.

Compared with an open cycle, the volume of final waste is reduced by a factor of 4 and the radiotoxicity of this waste is reduced by a factor of 10. In addition, the surface area required by a disposal facility in a geological formation deep underground is also reduced (by a factor of up to 2 or 3 in the latter case).

Finally, vitrified waste represents a robust and resilient waste package suitable for long term disposal: research conducted on this subject by the Commissariat à l’énergie atomique (CEA) has suggested that this glass matrix will retain 99.9% of its integrity after a period of 10 000 years.

2.3. Non-proliferation

The decisions made in France have led to a reprocessing process that complies with international standards on non-proliferation. Recycling arrange-ments (via the conversion of 20 French nuclear reactors to MOX) have been developed to permit in-line management of the plutonium resulting from reprocessing operations, thereby avoiding the formation of separate stocks of plutonium. Furthermore, when irradiating the MOX fuel making up around 30% of the reactor core, approximately 30% of the plutonium is used up in the operation, representing a positive balance from a non-proliferation point of view, as well as from an economic viewpoint, as this makes it possible to generate approximately 10% of electricity from nuclear origins. Finally, the PUREX industrial process is already suitable for adaptation to an evolutionary third generation formula, known as COEX, which avoids any need to separate the plutonium.

2.4. The future of reprocessing: Third and fourth generation processes

To conclude, opting for the reprocessing–recycling option has placed France in a particularly flexible position at the present time.

In the event that future energy policy decisions lead to the use of fast neutron reactors over the coming decades, spent fuel which is currently in interim storage (and particularly spent MOX fuel) would provide the necessary strategic energy materials to allow the operation of these reactors.

In addition, apart from the trends which have already been identified towards third generation processes, the PUREX process also provides a foundation for developing fourth generation processes compatible with a strategy which includes recycling and transmutation of minor actinides.

3. IMPLEMENTATION OF A NATIONAL RADIOACTIVE WASTE