History and Actual State of Non-HEU Fission-Based Mo-99 Production with Low-Performance Research Reactors

Table 1

Flux density and corresponding U-enrichment for irradiation of very low enriched targets and given heat removal system capacity. Irradiating of 280 g of U-metal pellets over 100 h with subsequent 20 h cooling time and about 10 h processing time, resulting in 550–740 GBq (15–20 Ci) Mo-99 (calibrated 6 days after end of production), is expected to be delivered under given effective thermal neutron flux densities with the suggested ²³⁵U enrichments.

𝑛th-flux density [𝑛/(cm^2s)]	7𝐸13	5𝐸13	3𝐸13	2𝐸13	1𝐸13
(^235U) enrichment [%]	0.7 (^natU)	1.0	1.7	2.5	5.0