Reprocessing :

The treatment and processing of spent fuel assemblies. These are first chopped into small pieces and dissolved in nitric acid solutions. A chemical extraction is used to separate the uranium, plutonium and fission products. The spent fuel (uranium and plutonium) can be recycled; the fission products are stored in a double wall tank. Next, they are vitrified to eliminate the risk of subsequent dispersion into the environment.

Enrichment :

The modification of the isotopic composition of an element. In the case of uranium, it raises the uranium 235 content to a level higher than that in natural uranium. Natural uranium is a mixture of various isotopes. The most important of these are uranium 238 and uranium 235. Uranium 235 easily undergoes nuclear fission. However, natural uranium only contains 0.7% of uranium 235. In order to use uranium in light water reactors, uranium 235 must be raised to 3 or 4%. The natural uranium must be enriched in the uranium 235 isotope at an uranium enrichment plant.

ALPHA radiation :

Alpharadiation is the spontaneous emission of particles that are relatively big and heavy. Therefore these particles are not very penetrative and are very quickly slowed down. A sheet of paper or a layer of air of 3 cm is sufficient to slow them down.

Plutonium oxide :

Plutonium is produced in reactors by the absorption of neutrons generated during the fission process by uranium 238. During reprocessing, the plutonium is separated from the spent fuel in a nitric acid solution and then purified. Pure plutonium is a hard metal, silver-white in colour which looks like iron. In contact with air, it transforms spontaneously to plutonium dioxide (PuO2). The latter is used in light water reactors as MOX fuel (in combination with the oxide of depleted or natural uranium).