Safety Issues Related to Production of Fission-based Mo-99 by Using Low Enriched Uranium (LEU)

Technetium-99m (Tc-99m) is the daughter element of Molybdenum-99 (Mo-99) and is work horse of modern nuclear diagnostic. More than 80% (.30 million patients with a growth rate of 1% to 2%) of the world-wide nuclear diagnostic imaging procedures are being carried out by using Tc-99m. Mo-99 can be produced either by reactor-based technology or by accelerator-based technology. Cross sections for reactor and accelerator based technologies are shown in Table 1. Keeping in view the above results, the fission-based option remains an appropriate option for production of Mo-99 on commercial scale. In order to produce fission-based Mo-99 from research reactors two types of targets are being developed and irradiated: HEU with U-235 enrichments more than 90 wt% of U-235 and LEU with U-235 enrichments less than 20wt% of U-235. It is worth noting that medium enriched uranium i.e. 36wt% of U-235 as being used in South Africa is also regarded as non-LEU from the nuclear security point of view. The purpose of this review was to look into the comparative studies of the LEU and HEU targets as well as to discuss and compile the safety issues related to irradiation and processing of LEU targets. Mo-99 production from LEU targets comparable to HEU targets will need more targets, more irradiation facilities, appropriate transportation for large number of irradiated targets and processing facilities capable of holding more liquid and solid waste in comparison to HEU process facilities. The production of radioactive waste is inadvertent however; its impact can be lessened by adopting effective waste storage, monitoring and disposal strategies