THERMAL HYDRAULIC AND NEUTRONIC CORE MODEL FOR POWER TRANSIENT ANALYSES OF REFLECTOR EXPERIMENTAL DEVICES DURING SHUTDOWNS IN JULES HOROWITZ REACTOR (JHR)

The Jules Horowitz Reactor (JHR) is expected to become the most important material testing reactor in the framework of European nuclear research and development. It is designed to exploit a fast in-core spectrum as well as a thermal neutron flux within the experimental locations in the reflector. The latter are mainly used to investigate fuel behaviour under nominal, abnormal and post-failure operating conditions. Since the core power is relatively high (100 MW), the power released within the reflector fuel devices is not negligible. Heat removal is a main topic in nuclear safety and power transient analyses concerning these experimental devices are requested in order to control fuel samples heating. Here a model of JHR core is implemented by means of the pointwise kinetics code DULCINEE. It takes into account both the neutronic features of the system and the thermal hydraulic properties as far as reactivity feedbacks are concerned. The core power transients are evaluated with respect to normal shutdown and safety shutdown. Then neutronic coupling between reflector and core is computed by means of the Monte Carlo calculation code TRIPOLI 4.7. Thus power evolution in experimental devices is obtained accounting for four burnup levels during the equilibrium cycle – namely Beginning of Cycle (BOC), Xenon Saturation Point (XSP), Middle of Cycle (MOC) and End of Cycle (EOC). Fission energy is released through different nuclear interactions. Depending on the considered radiation, the yield of energy deposition is different and the time behaviours are specific to particle production mechanisms. Finally neutrons and gammas are considered in terms of energy deposition and contribution to total in-reflector fuel sample power transients during the considered shutdown procedures.