Analysis of Mo-99 production capability of gama aqueous homogeneous reactor (GAMA-AHR)

Nuclear Engineering and Engineering Physics Department – Faculty of Engineering – Universitas Gadjah Mada developes new nuclear reactor to produce medical radioisotopes (primarily Mo-99). The reactor is AHR (Aqueous Homogeneous Reactor) type namely GAMA-AHR. The GAMA-AHR uses fissile (seed) fuel of 3.5 % mole uranyl nitrate solution in H2O and fertile (blanket) fuel and of 4 % mole thorium nitrate solution in H2O. The GAMA-AHR uses light water as primary coolant, neutron reflector as well as radiation shielding. The aim of this design is to avoid utilization of graphite reflector, thus simplify the design and allows totally passive post shutdown cooling systems. The GAMA-AHR is designed with 200 kWth thermal power and with Mo-99 production capability more than 2000 six-day Ci per week with near continuous operation. The analysis of Mo-99 production capability is performed by solving Mo-99 material balance equation for each process stages. The Mo-99 material balance formulation includes Mo-99 generation by fission reaction, by related its parent decay, Mo-99 depletion due to decay and neutron absorption and Mo-99 accumulation in reactor fuel solution. And also Mo-99 extraction, decay and accumulation in extraction apparatus, delay tank, purification apparatus and final processing apparatus, i.e. packaging and calibrating apparatus. Mole balance of other Mo isotopes is formulated and solved to calculate the purify degree of Mo-99. The calculation results shows that GAMA-AHR with 200 kWth thermal power has equilibrium standard delivered Mo-99 production capability of 2531 six-day Ci (delivered) per week. The equilibrium production capability does not depend on extraction delay time. The peak Mo-99 production capability however, depend on extraction delay. The longer time extraction delay time the higher the peak Mo-99 production capability. All of Mo radioisotope contaminants have far shorter half-life then the half-life of Mo-99. Delay time and processing time significantly eliminate these contaminants.