Neutronic aspect of Subcritical Assemby for Mo-99 Production (SAMOP) Reactor

NEUTRONIC ASPECT OF SUBCRITICAL ASSEMBLY FOR Mo-99 PRODUCTION (SAMOP) REACTOR. Design of a subcritical assembly for Mo-99 production (SAMOP) is in progress at National Nuclear Energy Agency. The main purpose of the project is to b able to produce Mo-99, which is a parent of Tc-99m an important nuclide for nuclear medicine application. The major source of Mo-99 is from fission of U-235. The conventional technique is by forming the uranium into targets and irradiated by neutrons from research or test reactors, then the irradiated targets are dissolved and the Mo-99 is extracted from the solution. Another technique to produce Mo-99 from U-235 is by using homogeneous reactor fueled with uranyl nitrate. This method introduced by Ball in 1992 and some advantages compared with the conventional method. On the SAMOP design, the low enriched uranyl nitrate is placed in the stainless steel container and irradiated by neutron generator. In this paper, the neutronic aspect of the design will be reported. Including the criticality analysis to secure the subcriticality of the design and the neutron flux distribution analysis, also the effect of the graphite reflector. The neutronic analysis was using the general monte carlo code, MCNP