On-line measurement of the isotopic composition of uranium in UF6

An in-line monitor used initially to continuously measure the 235U enrichment in liquid UF6 at the Portsmouth Gaseous Diffusion Plant has recently been recalibrated to provide continuous measurements of both 234U and 235U. The instrument using both a gamma-ray detector for 235U and a neutron detector for 234U has produced data that is in good agreement with precision mass spectrometric measurements made on related samples of UF6. Studies now in process suggest that the use of such minor isotope data will provide the safeguards inspector with a useful additional tool in his efforts to independently verify the operations and nuclear material accountancy records of an isotope separation plant. The preliminary results indicate that an instrument originally developed to meet the operational problems of the plant can also make a significant contribution to the difficult problems of providing effective safeguards for an enrichment plant. (U.S.)