TMSR500 has potential to provide energy that are sustainable, safe, and low in CO2 emissions in Indonesia. Therefore study about TMSR500 will have a significant impact on the development of nuclear energy in Indonesia. Neutronic analysis of TMSR500 core will be conducted in this study. Influence of fuel composition, fuel volume fraction, coolant quantity, and material temperature on reactor criticality will be evaluated. The method used to obtain the neutronic aspects of the reactor is neutronic calculation by computer simulation using the SRAC2006 code system and the JENDL4.0 nuclear library. The data obtained for neutronic analysis are graph of keff against time for each design parameter variation, graph of reactivity against relative coolant nuclide density and relative temperature, and coolant nuclide density and temperature reactivity coefficient at BOL. The data shows that the fissile material is directly proportional to keff. While fuel volume fraction is inversely proportional to keff at BOL. Coolant nuclide density and fuel salt-graphite temperature are inversely proportional to keff and reactivity. With fuel volume fraction value of 27 percent, TMSR-500 core requires minimum U-235 concentration of 1.14 percent to achieve criticality. TMSR-500 core have a negative coolant nuclide density and temperature reactivity coefficient at BOL, where the value are -0.02764 (cm cubic) and -0.00003864 (/K) respectively.
