Use of Minor Uranium Isotope Measurements as an Aid in Safeguarding a Uranium Enrichment Cascade

摘要

Surveillance and containment, which are indispensable supporting measures for material accountability, do not provide those charged with safeguarding an installation with the assurance beyond the shadow of a doubt that all of the input and output uranium will in fact be measured. Those who are concerned with developing non-intrusive techniques for safeguarding uranium enrichment plants under the Nuclear Non-Proliferation Treaty have perceived the possibility that data on the minor uranium isotope concentrations in an enrichment cascade withdrawal and feed streams may provide a means to either corroborate or contradict the material accountability results. A basic theoretical study has been conducted to determine whether complete isotopic measurements on enrichment cascade streams may be useful for safeguards purposes. The results of the calculations made to determine the behavior of the minor uranium isotopes ( exp 234 U and exp 236 U) in separation cascades and the results of three plant tests made to substantiate the validity of the calculations are reviewed briefly. Based on the fact that the exp 234 U and exp 236 U concentrations relative to that of exp 235 U in cascade withdrawal streams reflect the cascade flowsheet, the authors draw the conclusion that the use of the minor isotope concentration measurements (MIST) in cascade withdrawal streams is a potentially valuable adjunct to material accounting for safeguarding a exp 235 U enrichment cascade. A characteristic of MIST which qualifies it particularly for safeguards application under the NPT is the fact that its use is entirely non-intrusive with regard to process technology and proprietary information. The usefulness of MIST and how it may be applied are discussed briefly. (ERA citation 04:025693)