Safety analysis of inadvertent control rods withdrawal of RSG-GAS research reactor for various initial powers

Abstract

RSG-GAS is an Indonesian MTR-type multipurpose research reactor with a nominal power of 30 MW. Within the context of Design Basis Accidents (DBAs), numerous potential initiating events with the potential to lead to reactivity insertion accidents (RIA) have been identified. Among these, simultaneous inadvertent control rod withdrawal stands out as one of the most limiting scenarios for MTR-type research reactors. In these safety analyses, we employ the PARET code to simulate three distinct initial power conditions: 1 MW, 15 MW, and 30 MW during high power with forced convection cooling mode. The selection of 15 MW as an initial power level is based on the fact that the reactor predominantly operates at this power level. In addition, another safety evaluation was also performed during low power of 300 kW with natural convection cooling mode. Throughout these simulations, it was postulated that the first trip signal fails to initiate a reactor scram, and eventually, the second signal successfully scrams the reactor. This transient journey may activate various reactor protection systems, including but not limited to, period-based protection, floating limit value protection, overpower trip protection, and more. The analyses have confirmed that no single safety limit was exceeded.