Fuel reprocessing - Processes, engineering and plants

Since its first industrial application in 1954 at Savannah River in the United States, the PUREX reprocessing process has demonstrated its ability to adapt to changing fuel conditions. It is still open to further improvements, with the aim of reducing costs and environmental impact.

The development and success of the PUREX process have not prevented parallel studies of other, very different processes, particularly in non-aqueous media, such as halide volatilization processes or pyrometallurgical or pyrochemical processes.

A radical change of process could only be justified in response to fuel choices that do not lend themselves well to the PUREX process, such as zirconium-based alloys that are particularly difficult to put into nitric solution, or molten salts. Today, however, there is renewed interest in pyrochemical processes for the reduction of long-lived elements in waste from reprocessing plants.

Like uranium, thorium can be fed into a fuel cycle for energy production. More widespread than uranium, and hence attractive to certain countries such as India and Japan, thorium has no fissile isotope. It must therefore be combined with uranium or plutonium to make nuclear fuel. The difficulties of implementing the cycle, linked in particular to the presence of highly energetic gamma emitters in the products recovered from reprocessing (uranium 233 and thorium), have largely hindered its application.

Reprocessing plants bear no resemblance to conventional industrial plants, due to the draconian precautions required when handling highly radioactive materials, some of which are also fissile. Containment of radioactivity, prevention of criticality risks and the choices made in terms of plant upkeep and maintenance all have a major impact on their structure.

Reprocessing reached industrial maturity with the commissioning in 1990 of COGEMA's commercial UP3 plant at La Hague, followed in 1994 by the UK's Thorp plant at Sellafield and the UP2-800 plant at La Hague, and the construction of Japan's Rokkasho-Mura plant, scheduled to start up around 2005.

Modern plants have achieved excellent performance in terms of capacity, yield and product quality, with releases of radioactivity into the environment well below authorized levels. The high reliability of the process and equipment, and the predictability of servicing and maintenance operations have led to a constant reduction in the dose equivalents received by personnel, by avoiding the need for direct intervention. The volume of waste containing long-lived elements is also constantly decreasing.

While French plants largely cover domestic needs, enabling us to offer services to foreign customers, the...