[en] The use of 250 g uranium silicide as fuel in RSG-GAS core had been started and will be continued with the use of 300 g uranium silicide fuel. Therefore a study on radioactive materials released from RSG-GAS when using 300 g uranium silicide fuel should be done. A situation was postulated and the source term characteristic was calculated using ORIGEN2.1 program whereas the radioactive materials released from RSG-GAS was calculated using PC-COSYMA. The reactor condition was assumed being in the LOCA situation which caused one fuel element melted. The calculation results indicate that the radioactivity and radiation doses received by public in 5 km radius from RSG-GAS are still lower than permitted doses for non radiation worker. (author)