The main reason for reprocessing is to separate the remaining uranium and plutonium in the fuel from fission products and transuranic elements other than plutonium, so that these materials can be reused as material for new fuel (MOX fuel with plutonium mixed with uranium or REPU fuel with reprocessed uranium).

During reprocessing the spent fuel is dissolved in hot nitric acid and the solution is subsequently exposed to several chemical processing steps to

separate the different components. In the present reprocessing facilities four main product streams can be distinguished:

• Uranium

• Plutonium

• Fission products and transuranic elements other than plutonium

• The metal components of the fuel element (fuel cladding, end pieces and spacers).

The uranium and plutonium are purified such that they can be either reused as MOX fuel or re-enriched to form REPU fuel, while the waste streams are treated and conditioned as described in Section 14.3.3.

At present two large reprocessing facilities, La Hague in France and Sellafield in the UK, are in operation, with a capacity of 1600 and 800 tonnes of spent fuel per year (measured as heavy metal (HM)) respectively. A third large facility (800 tonnes HM/year) is in pre-commercial testing at Rokkasho in Japan. Smaller reprocessing plants (100-400 tHM/year) are in operation in Russia, India, Japan and China. Approximately 15-20% of the spent fuel being generated today is reprocessed. The remainder is stored for direct disposal or a future decision to reprocess.

Reprocessing is a proven industrial technology. Development work is going on to increase the proliferation resistance (e. g. by not producing separated plutonium). Recycling of the plutonium as MOX fuel in light water reactors as well as the reprocessed uranium is also performed on a routine basis, in particular in France. The economy of reprocessing and recycling in LWR will differ from country to country. The situation is quite different for a country with its own reprocessing facility than for a customer country. Some countries also have political concerns about reprocessing. All in all this has led to the situation that today reprocessing plants are not fully utilized and most countries have adopted a wait-and-see position.

The increasing expectations for nuclear power use in the future have, however, revived the interest in reprocessing and recycling. Several initia­tives have been launched over the last few years to increase the interna­tional cooperation in this field, e. g. the International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) (IAEA, 2010), the Generation IV International Forum (GIF, http://www. gen-4.org/ ), and the International Framework for Nuclear Energy Cooperation (IFNEC, earlier the Global Nuclear Energy Partnership (GNEP)).

For nuclear energy to be sustainable in the long term (more than a few hundred years) it will be necessary to introduce at some time fast reactors that will utilize the uranium resource in a more efficient way. The real eco­nomic value of recycling will only come with the development of fast reac­tors. The important question for spent fuel management is when fast reactors will be introduced such that recycling can have a real impact.

The waste from reprocessing, i. e. HLW containing fission products and transuranic elements, and ILW containing the metal components of the fuel elements and secondary waste, will require geological disposal after condi­tioning. The heat generation from the HLW needs to be considered in the design of the repository. Development work is going on to also separate out the transuranic elements during reprocessing to reduce the long-term heat generation (over >100 years) and also the radiotoxicity of the high-level waste (advanced reprocessing). This would have the potential to simplify the design of the repository and the long-term safety assessment (although the transuranic elements rarely are dominating the doses in the safety assessment). To achieve this gain, the separated transuranic elements will need to be recycled and burned in a fast reactor system. As for fast reactors, this development will require at least another 50 years for commercial introduction.