Because heavy water research reactors (HWRRs) have high thermal neutron fluxes, they are commonly used in fundamental physics research. Due to the moderating effects of heavy water, the resulting neutron beams are free of fast neutrons, which is beneficial for materials physics experiments. Conversely, these reactors are not appropriate for materials testing since the closed vessel used to retain the heavy water makes it impossible to reach equipment that is situated close to the reactor core. Irradiation test loops are coupled to this kind of reactor so that it can benefit from its neutron advantages.

Still, it is precisely this kind of test loop that leads to the most dangerous design-basis accident, a reactivity insertion accident (RIA). Following a RIA in a heavy water reactor, this study examines the uncertainty and sensitivity of a few input parameters on the computed outcome of the peak cladding temperature (PCT) and the pellet-cladding mechanical interaction (PCMI).

Using the FEMAXI6 code, the behavior of a fuel rod during a limiting RIA is examined. Safety analysis of the reactor core is performed using the RELAP5 code. We analyze the uncertainty and sensitivity of the RELAP5 and FEMAXI6 results for the HWRR RIA using the SUSA 4.0 code.

According to this study, the operating regime under analysis, steady state, transient, or accidental, determines the set of parameters that impact a particular outcome. In fact, the uncertainty effect of coolant temperature and coolant velocity was disregarded in our earlier work when the system was operating in steady state, but in the case of an accident, these two parameters had a significant impact on PCT and PCMI.