Neutronic and thermal hydraulic study for iridium-192 production in a research reactor

The Egyptian Second Research Reactor (ETRR-2) is a pool type reactor, 22 MW thermal with 27 fuel elements, loaded with ⁶⁰Co production facility in the most relative highest flux position for the production of 200 Ci/g specific activity. The production of this specific activity needs a very long irradiation time, and continuity of operation to produce useful quantities of cobalt-60 over a reasonable period, which means that the reactor would have to operate 24 hours a day, for 5 to 7 days a week. This requirement for the production of cobalt with the required specific activity is difficult to meet in ETRR-2; so this position needs to be reused for the production of other radioisotopes that require shorter irradiation times compared to cobalt. ¹⁹²Ir is the most important radioactive isotopes of iridium; it can be used in the production of ''sealed sources' for industrial or medical applications. In this study, we did a full neutronic analysis of ETRR- 2 reactor core with iridium and with cobalt and compared both cases. For neutronic analysis used two different models; a model using MCNP code (Monte Carlo Neutron Photon) and another model using WIMS/CITVAP code (deterministic code). The models were validated with the results of the experiments done during the commissioning of facility. We concluded that a maximum mass of iridium 661.344 could be used instead of 577 g of cobalt in the core, and 24 molybdenum production plates would fulfil the fixed experiment design criteria, which is lower than 1200 pcm. The average axial/radial flux inside the tube was lower when using iridium disks than when using cobalt pellets, because of the difference between the neutron absorption cross-sections of ¹⁹¹Ir, ¹⁹³Ir and ⁵⁹Co. When comparing the average radial flux inside the irradiation position near the edge of the iridium pellets inside the tube, we found that the flux would be higher for iridium than cobalt because of the empty part of the tube. We also calculated the power peaking factor over the whole core and found it was 2.12, which fulfilled the design criteria (must be less than 3). On other hand for thermal hydraulic parameters using computational fluid dynamics (CFD). ANSYS Fluent is a powerful and flexible general-purpose computational fluid dynamics software package used to model flow, turbulence, heat transfer, and reactions for industrial applications. The thermal results show that the maximum temperature on the wall was ∼ 52 Degree Celsius C which is so far from 105 Degree Celsius C, the velocity outlet contour and turbulence kinetic energy show that the cobalt could be replace safely with iridium disks. The safety goal for TWR and ONBR was verified and meet the design criteria