Collimated neutron beam design for TRR thermal column

Tehran Research Reactor (TRR) is the main neutron source in Iran which can be used for different applications of neutrons such as neutron radiography and neutron therapy. TRR has a thermal column which can provide high intensity flux of thermal neutrons for users. The aim of this study is to design a neutron collimator for TRR thermal column to produce parallel neutron beam with suitable intensity of thermal neutrons. To achieve this goal, Monte Carlo code of MCNX has been used to evaluate different configurations, geometries and materials of neutron collimator. The results show that the final selected configuration can provide a uniform thermal neutron beam with a flux of 1.21E+13 (cm-2·s-1) which is suitable for many different neutron applications.

Evaluation of promethium-147 production as a by-product of the fission molybdenum-99 process in Tehran research reactor

Molybdenum-99 and some other fission products such as promethium-147 are formed by the fission of 235U. Applying an efficient separation approach, the 147Pm can be isolated. The production of 147Pm as a by-product of previously optimized conditions for fission molybdenum-99 process is precisely evaluated. Considering the numerous radionuclides with various half-lives accompanying the 147Pm as impurities, a precise time window can be determined to perform an efficient separation process. The fission products activity calculations, using MCNPX and ORIGEN2.1 computer codes, were performed to achieve such a proper time window. Here, it is shown that 300 days after the end of bombardment (EOB), the radioactivity of the other radionuclides is reduced to 1% of 147Pm radioactivity. The chemical process needed to separate the remaining radionuclides is then explained in detail.