Modification and validation of GAMSET computer code for gamma heating analysis of innovative research reactor core

One of the important factor on design of nuclear reactor core is how to maintain the reactor core always on the save condition, both for normal operation and accident condition. The gamma heating is one of the safety factor that should be determined correctly. To support Innovative Research Reactor core conceptual design, gamma heating distribution value should be determined correctly. The GAMSET computer code is one of the tool that can be for gamma heating calculation for research reactor core. Unfortunately, GAMSET computer code that initially dedicated only for small core configuration (10x10) as RSG-GAS core type, has the constraint for the Innovative Research Reactor core configuration, because of relatively large core configuration (20x20) and new fuel element used in this innovative research reactor (UMo). For this reason, GAMSET computer code should be modified and updated with additional nuclear data associated with UMo fuel element. This paper describe the GAMSET modification, nuclear data additional related for UMo fuel and the validation of the resulting data compared before and after modification. From the tests results, that can be conclude that GAMSET was successfully modified and ready for gamma heating analysis for Innovative Research Reactor core. (author)