Irradiation capsule design for neutron coloration of topaz in a WWR-K reactor.

This study justifies irradiation capsule design calculations used for efficient coloring of topaz in a WWR-K reactor. Various radiation screens used for removing thermal and epithermal neutrons and their influence on the activation of the main impurities in topaz are considered. Neutron analysis has been performed by means MCNP transport code. It is shown that the use of a sandwich screen composed of boron carbide and tantalum decreases the fraction of thermal neutrons by 24% and increases the fraction of fast neutrons by 15%. These are the optimal neutron conditions for topaz irradiation in a WWR-K reactor. Thermal analysis has been performed by means Comsol code and two approaches were taken: conservative and realistic. A thermo-physical analysis with a conservative approach showed that for boron carbide and tantalum screen the temperatures under forced and natural convection modes were 134°Ð¡ and 274°Ð¡, respectively. The temperature of the case body was 75 °C with forced cooling and 238 °C without cooling. In case of realistic approach, the topaz temperature does not exceed 65°Ð¡ if regular cooling of the irradiation capsule is ensured. Calculation results showed the importance of the ensure circulation between topaz during irradiation, which makes it possible to reduce the temperature of topaz by almost half.

Analysis of lutetium-177 production at the WWR-K research reactor.

Production of lutetium-177 using direct nuclear reaction 176Lu(n,γ)177Lu by WWR-K reactor neutrons on enriched LuCl3 (up to 82% of 176Lu) is described. Calculations were performed by MCNP6 transport code. Two different irradiation positions of the WWR-K research reactor were considered. Estimates of the maximum specific activity of the luthetium-177 are obtained for the reactor irradiation positions located: (a) in the reactor core centre, (b) in the core periphery. In these positions, thermal neutron flux is two times different. Experimental data was shown that k-factor is 1.5 for considered irradiation positions. The study shows that for the position located in the core center, the estimated maximum specific activity of lutetium-177 is 819 GBq/mg, is to be achieved after 15 days of irradiation. For the position located in the core periphery, specific activity of lutetium-177 is 561 GBq/mg, is to be achieved after 20 days of irradiation. Ratio of Lu-177m to Lu-177 specific activity is not more than 0.025 for both irradiation positions.