Themes > Science > Chemistry > Nuclear Chemistry > Nuclear Reactions > Transmutation > Breeding and transmutation > Transmutation and incineration

Nuclear energy production is accompanied by production of radioactive wastes of different nature:
  • Fission products
  • Activation products obtained from neutron capture by nuclei belonging to the structure of the reactor, such as, for example, Cobalt 60.
  • Transuranic nuclei obtained from neutron capture by the nuclear fuel.

Nuclear wastes are characterized by their radiotoxicity and their life-time. Only wastes with life-times exceeding about ten years are associated to significant storage problems. These are essentially some fission products and transuranic elements. Fission products decay by $\beta $ radiation, while transuranic elements decay essentially through $\alpha $ radiation. For the same disintegration rate, $\alpha $ emitters are much more radiotoxic than $\beta $ emitters. It follows that the main nuclear waste problem is that of transuranic elements.

Two different strategical approaches are proposed for high activity nuclear wastes disposal:

  • Direct spent fuel elements underground storage, without any reprocessing.
  • Spent fuel reprocessing with the aim of optimized extraction of transuranics and fission products and their transmutation by nuclear reactions into less radiotoxic or short lived species. Here we examine this strategy in more details, especially in the French context which appears to be one of its more systematic approach.

Available nuclear reactions for nuclear waste processing are of two types:

  • Transmutation which, by neutron capture, transforms a radioactive nucleus into a stable one. This method is suitable for fission products. As stable nuclei could be, simultaneously, transformed into radioactive ones, the method requires an initial separation of the isotopes to be transmuted. This separation is still not available on an industrial scale.
  • Incineration which amounts to nuclear fission following neutron capture. This method is suitable for transuranic elements. It is always associated to energy and neutron production. It is already applied, at an industrial scale to Plutonium.

The Plutonium case. From the preceding Plutonium can be considered according to two different view points. In the breeding strategy it is a nuclear fuel. In normal PWR reactors it appears to be a nuclear waste which is apt to be incinerated. Incineration is possible with thermal reactors like PWR, but, as will be seem below, it cannot be complete in this case. Indeed, it is associated with the production of transplutonic elements( Americium and Curium) which cannot be incinerated in PWR.


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