Thermal-Hydraulic Benchmarking of RSG-GAS Research Reactor Using RELAP5 (Endiah Puji Hastuti1,a), Andy Sofrani Ekariansyah1,b), Sudarmono1,c), Sujarwono2,d), Saensuk Wetchagarun3,e)

Abstract. RSG-GAS multipurpose reactor was designed to be able to operate with 30 MW power. In order to obtain
operation license renewal from Indonesia Nuclear Regulatory Body-BAPETEN, it is required that evaluation or
assessment on any systems related RSG-GAS full power operation should be performed. This research has two
objectives. The first is to re-evaluate overall RSG-GAS system capability, the second objective is to benchmark RELAP5
model for RSG-GAS based on the input obtained from the experiment results. The results of the experiment on the raising
of RSG-GAS power to its full power of 30 MW and power calibration by calorimetric indicate that there is a significant
difference between definitive power and measured power, caused by the determination of correction factor. The RELAP5
modeling for RSG-GAS using experimental data input indicates a deviation of 1.77 % to 8.73 % for temperature
calculation, while the deviation is 5.6% - 7.66% for flow rate. These figures indicate that this modeling for RSG-GAS is
valid. The highest fuel temperature at steady state condition at 30 MW is 87.12°C. The highest temperature limit at the
beginning of the cycle is 175°C, which is still in the permitted envelope. It was shown that RSG-GAS could operate at its
full power of 30 MW. Key words: RSG-GAS, RELAP5, periodic safety review, benchmarking , thermal-hydraulic