SHUTDOWN TRANSIENTS ANALYSIS FOR REFLECTOR DEVICES POWER CALCULATIONS IN JULES HOROWITZ MATERIAL TESTING REACTOR (JHR)

Jules Horowitz Material Testing Reactor (JHR) is planned to be the first European nuclear experimental facility of next decades thanks to its testing capacity. High flux level ac- cording to 100 MW power is exploited through many test slots. Fast core spectrum allows high dose rates for material testing and thermal neutron flux is achieved inside a large re- flector. Here fuel samples are irradiated inside experimental devices – namely MADISON, ADELINE and MOLFI – and each specific power is then worth to be evaluated for safety reasons. Moreover, devices transients require particular analyses for reactor shutdown conditions, in order to evaluate power behavior. All nuclear heating effects are concerned and related time-dependent description is carried out in this work. First, thermal hydraulic and neutronic core model is implemented through DULCINEE code to obtain core tran- sients. Then, detailed power calculations for reflector devices are obtained through an enhanced multi-point kinetics model accounting for every device which is now thought of as a single lumped system - coupled with reactor core as external source. Core-device coupling coefficients to define this model are finally obtained by means of Monte Carlo simulations with TRIPOLI 4.8 code, about different core fuel compositions – namely Beginning of Cycle (BOC), Xenon Saturation Point (XSP), Middle of Cycle (MOC) and End of Cycle (EOC). Complete power deposition in devices is obtained through TRIPOLI simulations considering prompt gamma irradiation. Delayed gamma sources are evaluated with PEPIN2 burnup code.