Investigating an alternative sustainable low-enriched uranium target for the manufacture of 99Mo using MCNP6.2 modelling with CINDER90

Abstract

Introduction: Current fission-based methods of 99Mo production use targets that are based on high output without taking into consideration the amount of radioactive waste produced. We examine the idea of using a low enriched target (<20%) to reduce the amount of nuclear and chemical wastes produced by the manufacture of 99Mo via fission of uranium-based targets.Methods: MCNP6.2 was used to model targets of 20%, 10%, 7%, 3%, and 1% enrichment for 99Mo output and sustainability.Results and Discussion: The 1% enriched target at the lowest density of 0.2 g/cm3 of UO2 was found to have the highest sustainability score at 6 days irradiation but it had a low 99Mo output. On the other hand, the highest output target was found to be 20% enriched with a density of 8.0 g UO2/cm3 with an irradiation time of 20 days. Target security and safeguards concerns were modelled and found to be of minimal concern.

Investigating 99Mo output changes in high-sustainability uranium targets by modifying target volume and geometry

“…In the quest for a more sustainable method of fission-based 99 Mo production, the concept of a reusable uranium-based target was explored (Raposio et al, 2021), with target efficiency defined as the amount of 99 Mo activity produced per gram of 235 U present in the target, with the aim of designing a uranium target with a high burnup. This study was followed by research developing the target sustainability index (Raposio et al, 2023). In this study, a theoretical uranium-oxide-based target (UO 2 ) for manufacturing 99 Mo gave results indicating that a low target density of 235 U leads to high sustainability, with the trade-off of a much lower 99 Mo output.…”

“…The following simulations were modeled using MCNP6.2 (Werner et al, 2018) and CINDER90, with reactor dimensions and target positioning identical to the model reactor used previously (Raposio et al, 2021;Raposio et al, 2023) and the sustainability index calculated as outlined in Raposio et al (2023).…”

“…It is expected that a cylindrical uranium target would hold more heat than a plate-type target after irradiation. Target proliferation concerns also need to be addressed (Raposio et al, 2023); the amounts of 239 Pu produced by targets of different geometries need to be considered as well.…”