Instrumentation and control for reprocessing plants. Instrumentation

The nuclear fuel cycle comprises the following main industrial and commercial activities:

• mining, extraction and refining of natural uranium ;

• enrichment of natural uranium to increase the fissile isotope content ( ²³⁵ U) from 0.7% for natural uranium to around 3.5% for enriched uranium ;

• manufacture of enriched uranium oxide fuels ;

• use of these fuels in power reactors (PWR and BWR) operated by utilities in the major industrialized countries;

• fuel reprocessing for uranium and plutonium recovery and waste conditioning.

In recent years, these activities have been supplemented by the production of fuels based on mixed oxides of plutonium from reprocessing and depleted uranium from enrichment. The use of these fuels (MOX: mixed oxides) in water reactors has necessitated the implementation of MELOX-type fabrication workshops at Marcoule.

Most industrialized countries use this nuclear fuel cycle, at least in part.

In addition to the raw material savings associated with uranium and plutonium recycling, reprocessing provides a more appropriate and forward-looking solution to the problem of waste conditioning than direct storage of irradiated fuel leaving reactors, by reducing volume and radiotoxicity as much as is reasonably possible.

Reprocessing is a major industrial activity involving mainly :

• Destructuring by shearing the fuel;

• nitric dissolution of the latter, followed by separation of the uranium and plutonium by liquid-liquid extraction;

• conversion of uranium and purified plutonium into oxides;

• vitrification of virtually all fission products and residual actinides contained in effluent concentrates;

• on-line waste conditioning: compacting of structural waste (Zircaloy liners) and technological waste destined for deep disposal, and concreting of low-irradiation technological waste that can be stored on the surface.

Great care is taken to ensure safety, radiation protection and the minimization of waste volumes and discharges into the environment.

The downstream fuel cycle, whether closed with reprocessing or open with the temporary storage of irradiated fuel, involves a number of global industrial groups, the main ones being Cogema in France, organized around five families of activities, BNFL in the UK, JNFL in Japan, and so on....