NEUTRON METHODS FOR MONITORING THE BLENDING OF ENRICHED UF6 GAS

Blending a highly enriched UF6 gas stream with low-enrichment material reduces the excess supply of highly enriched uranium that must be clo sely controlled for nonproliferation of nuclear weapons. Computer simu lations and feasibility experiments show that inducing fission in U-23 5 provides means for monitoring the blending process. Detecting delaye d fission neutrons or gamma rays after fission products drift downstre am in the gas gives a measure of U-235 content and flow velocity, At v ery low UF6 gas pressures (5 mm Hg) where the downstream signal is too weak for use, an alternative technique based on attenuation of therma l neutrons passing through the UF6 gives a measure of U-235 content.