Abstract:
For the training of reactor personnel, study on temperature effects is conducted on ULYSSE reactor, in which both water and graphite play a important role in temperature effects. The experiment is performed by changing intentionally the water temperature. Analysis of the recorded parameters give an insight on the temperature effects, showing that the reactor is sub moderated, by conception, participating to the safe operation of the reactor. The temperature coefficient of water, related to dilatation effect, of graphite, related to capture cross section variation with temperature, and the global coefficient (water + graphite) are calculated. The experiment also shows that the apparent temperature coefficient that is "lived" by the operator is not constant through the time. Indeed, it depend on the kinetic of the temperature variation in water and in graphite, the latter presenting a significant inertia. Finally, from the understanding of these temperature effects, empathise is given on there impact on the safety of reactor operation, particularly in the occurrence of an accidental situation.