Evaluation of nuclear heating in sample materials irradiated in RSG-GAS core

Abstract

Reaktor Serba Guna GA Siwabessy (RSG-GAS) is a multipurpose Material Testing Reactor (MTR) with nominal power of 30 MW and currently utilized for material irradiation and other research purposes. When a sample material is put in the core of RSG-GAS, there will be some amount of nuclear heating generated in the sample material induced by interaction of gamma rays with the sample material. Evaluating the nuclear heating is one of the important aspects regarding the safety of reactor operation and the safety of the sample material itself. In this work, the nuclear heating of several sample materials commonly irradiated in the RSG-GAS core were evaluated using GAMSET code. The sample materials taken as the case study is sample for radioisotope production (TeO2, MoO3, UO2, Sm2O3, Yb2O3, Zn, S), sample for research purpose (C, AlMg3, Hg), topaz, and sample for cladding material (Al, Zr, Fe, SS304L). The sample materials were irradiated in 3 positions in the core, i.e. E6, D9, and B1, for 5 days with thermal power of 15 MW. From the results of nuclear heating calculation, it was found that the nuclear heating generated in sample material in certain position is greatly determined by the type of core structure that surrounding the material position. The difference of nuclear heating generated in the position of D9 has a higher amount of 5% compared to the nuclear heating generated in the position of E6, while for the position of B1 the amount of nuclear heating generated is much lower. Among all the material samples, UO2 has the highest nuclear heating since it contains fissile material, white for the other sample material the amount of nuclear heating varied between between 3∼11 watts/gram in the E6 and D9 position, and between 0.4∼1.4 watts/gram in the B1 position. The results of nuclear heating obtained in this work can be used as a database for the purpose of evaluating the safety of reactor operation and sample material irradiated in RSG-GAS. The data of the nuclear heating in this work can also be used to complement the RSG-GAS safety analysis report.