Neutronic analysis on potential accident tolerant fuel U₃Si₂ in pressurized water reactors’ fuel assembly

To support the nuclear R&D program, especially on its first nuclear power plant in Indonesia, Research Organization for Nuclear Energy (ORTN) BRIN has carried out several stages of research related to the safety of reactor operations. This study was part of increasing the safety of nuclear power plants, by determining the neutronic behavior of the U₃Si₂ fuel assembly as a substitute for the UO₂ in the AP1000 reactor. U₃Si₂ fuel is promising because its high thermal conductivity will provide lower fuel temperatures during normal operation, and its high uranium density could lead to economic benefits. Neutronic parameters were calculated using the PIJ module from SRAC2006 with the ENDF/B-VII nuclear data. The infinite multiplication factor (k-inf), reactivity coefficient, and neutron spectrum of the PWR AP1000 fuel assembly will discuss. In general, calculations were carried out in Hot Full Power (HFP) conditions, with 900 K fuel temperature, the coolant temperature, and cladding temperature was 557.55 K with 1184 ppm boron and without boron. The calculation results show that the Moderator Temperature Coefficient (MTC) and Doppler Temperature Coefficient (DTC) of U₃Si₂ fuel are always negative for all operating conditions that could ensure the reactor core’s inherent safety. The MTC value of U₃Si₂ is more negative than UO₂ because of the hardened spectrum, which reduces the number of thermal neutrons and increases the neutron moderator role. The k-inf of UO₂ fuel is greater than U₃Si₂ with the highest being around 501 pcm in without boron condition. Meanwhile, in the presence of boron in the coolant, the U₃Si₂ fuel k-inf is greater than UO₂ with a difference between 306 – 520 pcm. This is because UO₂ fuel has a thermal neutron spectrum larger than U₃Si₂, which caused boron to be more effective at oxide than silicide. Hence by using silicide fuel, it is possible to readjust the amount of boron and a burnable poison to increase its fuel efficiency. The results of this calculation show that U₃Si₂ fuel has good potential for use in the PWR reactor because it provides several benefits on neutronic parameters to increase the safety of reactor operation.