ANALISIS JUMLAH PRODUK MOLYBDENUM-99 (99Mo) SEBAGAI FUNGSI WAKTU BURN-UP PADA NILAI KRITIKALITAS OPTIMUM PADA AQUEOUS HOMOGENEOUS REACTOR (AHR)

Analysis of the amount of 99Mo production has been done by neutronic simulation using MCNPX software, which 99Mo is produced from fission 235U on AHR. The AHR geometry is of a cylinder with a diameter of 122 cm, height of 155 cm, 30 cm thick beryllium reflector, 3 cm thick stainless steel tank, and fuel. The UO2(NO3)2 solutions with concentration of 250 gU/l is used as a fuel, with the enrichment variation of 235U from 15% to 25%. AHR criticality expressed by keff value that directly proportional with the enrichment value. At optimum keff (16%) used to burn-up calculation for 15 days, and result 99Mo production is activities and mass. Nett production rate is composed of fission product rate that reduce by decay rate, and the result in an exponential equation y=1,2993×1020(1-e-0,2523t) as a function of time in days. On 15 days burn-up showed that the nett production rate still increases close to a constant rate. 99Mo results will be extracted on 11th day with activity 2118 6-day Ci and 0.02 gram mass. Keywords : AHR, MCNPX, Radiopharmaceutical, 99M