Neutronic study on direct conversion of the Indonesian research reactor RSG-GAS core to use silicide fuel

The Indonesian multipurpose reactor RSG-G.A. Siwabessy (RSG-GAS) which is designed by Interatom (now Siemens) obtained first criticality in July 1987 using Low Enriched Uranium (LEU), U3O8Al with fuel density of 2.96 g/cm3, 21 plate MTR type fuel element. Due to an excellent result of RERTR program [1] on both performance at high burn-up and possibility to have high fuel loading of Silicide fuel, activities to convert RSG-GAS core from Oxide to Silicide U3Si2Al fuel has been performed. The objective is to have higher fuel loading and to increase the fuel burn-up in such a way that the penalty of using LEU could be compensated. By using lattice code WIMSD4 and UM2DB diffusion code, preliminary result showed that using U3Si2Al fuel with the density of 3.55 g/cm3 has given satisfactory result such as, keff and flux distribution comparable to Oxide fuel; operation cycle 32.84 full power days as compared to 25 fpd for Oxide and higher burn-up 64% (56% for Oxide). Power peaking factor at TWC core and during transition from Oxide to Silicide fuel shows similar range to Oxide core with value of less than 1.30. Preliminary result shows the feasibility of LEU to LEU conversion from 2.96 g/cm3 U3Si2Al (250 gr U235 loading) to 3.55 g/cm3 U3Si2Al (300 gr loading) at RSG-GAS core with promising advantage in safety optimizing reactor operation cost. (author)