Safety Analysis of Indonesia's Multipurpose Reactor During Irradiation of Natural UO₂ Pin Target at Power Ramp Test Facility

To support the utilization of the power ramp test facility (PRTF) at the reactor Serba Guna GA Siwabessy (RSG-GAS) reactor, the investigation of safety parameters both on the target and the reactor during the irradiation of natural UO₂ has been conducted. The program for the analysis of reactor transient (PARET) and Monte Carlo N-particle version 6 (MCNP6) codes were integrated for thermal-hydraulic and neutronic analysis under the reactivity insertion phenomenon. The reactivity insertion and linear heat rate (LHR) were calculated by MCNP6 to confirm that the maximum values are well below the safety limits. Also, the code computed the reactor kinetic parameters to provide inputs for the PARET code to evaluate the reactor response due to the target movement at the PRTF. The target moves from the farthest position to the nearest one traveling 440 mm and then moves back to the original position. The safety analysis indicated that both maximum reactivity insertion and LHR values did not exceed the safety limits. The target induces maximum reactivity insertion of 0.023%dk/k and produces the maximum LHR of 137.53 W/cm and 275.06 W/cm; when the reactor operates at 15 MW and 30 MW, respectively. The PARET simulation results showed that the reactor power oscillated due to the target movement. Therefore, the recommended velocities of the target are below 0.17 m/s and 0.08 m/s for reactor power of 15 MW and 30 MW, respectively, to avoid the reactor scram, and no safety limits are exceeded.