G.A. Siwabessy Multipurpose Reactor (GAS-MPR) located in Center of Science and Technology Research (Pusat Penelitian Ilmu Pengetahuan dan Teknologi/PUSPIPTEK), Serpong, South Tangerang, is one of the research reactors owned by Indonesia, and operated by BATAN’s Center of Multipurpose Reactor (CMPR). Interatom International from West Germany built this reactor in 1983. This reactor reaches critical condition in March 27th, 1987 and being authorized by Indonesia’s second President (Grand General of TNI Purn. H. Muhammad Soeharto) in August 20th, 1987.