Effets de transmutation dans le carbure de bore : un point clef pour le design des futurs reacteurs nucleaires ?

Orateur : Lionel LAGRANGES (CEA Cadarache)

Seminaire Bilingue (diapo. en Anglais, discours en Francais) The French government decided to build a new research fast reactor named ASTRID. The design of this reactor requires data on the behavior of materials that are not only the fuel or the metallic assembly but also absorbers. Information on absorbers can be gained from many B4C samples that have been used as absorber in Phenix reactor, and that are available in CEA. However, the irradiation history of these samples is complex with different types of damage (ballistic or transmutation) and a neutron flux that had varied during irradiation. In order to get a full understanding of these reactor irradiated samples, we are trying to have B4C samples irradiated in a well-defined environment with only one type of damage. Therefore ion irradiations of B4C samples are performed in CEA-Saclay in order to study ballistic damage. On our side, we would like to have B4C samples irradiated in the pure thermal neutron flux at ILL in order to study transmutation damage.On a more general point of view, studying transmutation damage in neutron absorber materials by thermal neutron irradiation opens a new scientific field that has been poorly addressed up to now : chemical reactions without gradient. Because transmutation modifies the chemical composition of the material at the local scale, chemical reactions can occur without the existence of a reactive front or a temperature change. This effect has been observed on AIC (Silver, Indium, Cadmium) material that is used as absorber for pressurized water reactors but would deserve more efforts.

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