Combustible caramel for research reactors: Experience gained in manufacture, controls and irradiation of the core Osiris

One of the results of the different activities carried out in France regarding the concept, manufacture and development of nuclear fuels was the fuel plate type (CARAMEL) developed by the CEA, which can be adapted to different categories of water reactors (power reactor, naval propulsion, urban heating, research pile). These studies have been crowned by the realization of the whole core and fuel refreshments of the high power research reactor, Osiris, Saclay. The old fuel of strongly enriched U AI alloy has been replaced by a caramel fuel weakly enriched (7%), non-prolific. This new core has worked satisfactorily since January 1980. Following a brief description of the caramel fuel characteristics and its main advantages, we present its fabrication as well as the overall quality controls to which it is subjected. The qualification program as well as the main results concluded are given. The program of the course of the in pile fuel is also described whose aim is to ensure good behaviour of the fuel under irradiation conditions. The good operation of Osiris which completed II irradiation cycles on 21st April 1981 has justified the choice and the excellent behaviour of the fuel element under severe conditions in a high power research reactor. (orig.)