A Continuous In-Line Monitor for UF₆ Enrichment

A system has been developed to measure continuously the ²³⁵U and ²³⁴U enrichment in the UF₆ product of a gaseous diffusion plant. The measurements are made on liquid UF₆ prior to withdrawal into product cylinders. The ²³⁵U enrichment is measured to a relative accuracy of 0.5% at two sigma by counting the 185.7-keV gamma ray from ²³⁵U with an NaI detector. The ²³⁴U enrichment is measured with a neutron detector counting (α,n) neutrons from UF_6. The neutron system can measure either ²³⁴ U enrichment directly or ²³⁵ U enrichment indirectly (for low-enriched uranium, 2 to 5% ²³⁵U, the two enrichments are nearly proportional). The accuracy of the neutron measurement is 2.5% at two sigma. The gamma and neutron measurements are independent and could be used singly if only one isotope were desired. Both are required to measure ²³⁵ U and ²³⁴ U enrichment. The system is presently installed at the Goodyear Atomic Corporation gaseous diffusion plant in Piketon, Ohio.