The phenomenon of neutron flux during irradiation of the 4.5%UO2 PWR pin at the power ramp test facility RSG-GAS

Abstract

PRTF is the only testing facility based on irradiation process of PWR fuel pin in Indonesia. Several related studies, focused on the pin target. However, the safety state of RSG-GAS during irradiation process must be analyzed. The neutronic analysis of this paper is a preliminary study to confirm the safety state of the reactor. The phenomenon of neutron flux distribution during irradiation process of pin target in PRTF has been successful simulated using the Monte Carlo method, MCNP6. The UO2 pin target is assumed to have 4.5% enrichment. The pin target is placed inside the PRTF and moved into the reactor core. The PRTF has a total track length of 440 mm, and 280 mm of the track located outside the reactor core. The phenomenon has been studied at 440, 200, 100, 80, 60, 40, 20, 0 mm to the reactor core. In general, the distribution of thermal neutron flux decreases forming a cavity. The phenomenon occurred due to the thermal neutrons are used for fission reaction on the pin target. On the other hand, the distribution of fast neutron flux increases forming a new peak. The new population of fast neutrons are the product of fission reaction of the pin target during irradiation process. Each phenomenon is related to the position of pin target inside the PRTF. It has been observed that the neutron flux changes depends on the target position. The significant effect has been noticed when the target at the position of 20 – 40 mm of the reactor core. The information can be used as a description of neutronic characteristics inside the PRTF during irradiation pin target. With the result that the safety analysis of the RSG-GAS as an MTR type research reactor during irradiation target at PRTF can be studied more deeply.