Year
2009
Abstract
Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to verify declared LEU production, detect undeclared LEU production and detect HEU production with adequate detection probability using non destructive assay (NDA) techniques At present inspectors use attended systems, systems needing the presence of an inspector for operation, during inspections to verify the mass and 235U enrichment of declared UF6 containers used in the process of enrichment at GCEPS. In verifying declared LEU production, the inspectors also take destructive assay (DA) samples for analysis off-site which provide accurate, with 0.1% to 0.5% measurement uncertainty, data on the enrichment of the UF6 feed, tails, and product. However, DA sample taking is a much more labor intensive and resource intensive exercise for the operator and inspector. Furthermore, the operator must ship the samples off-site to the IAEA laboratory which delays the timeliness of the results and contains the possibility of the loss of the continuity of knowledge of the samples during the storage and transit of the material. Use of the IAEA’s inspection sampling algorithm shows that while total sample size is fixed by the total population of potential samples and its intrinsic qualities, the split of the samples into NDA or DA samples is determined by the uncertainties in the NDA measurements. Therefore, the larger the uncertainties in the NDA methods, more of the sample taken must be DA samples. Since the DA sampling is arduous and costly, improvements in NDA methods would reduce the number of DA samples needed. Furthermore, if methods of on-site analysis of the samples could be developed that have uncertainties in the 1-2% range, a lot of the problems inherent in DA sampling could be removed. At present, the increased use of the “Mailbox” system and random inspections provide some assurance that undeclared production does not occur. The use of an unattended system that could give data on the enrichment process as well as accurate measurements of enrichment and weights of the UF6 feed, tails, and product would be a major step in enhancing the ability of NDA beyond present attended systems for both verifying declared and undeclared production. The possibility of monitoring the feed, tails, and product header pipes in such a way as to gain safeguards relevant flow and enrichment information without compromising the intellectual property of the operator including proprietary information and operational parameters would be a huge step forward. This paper contains an analysis of possible improvements in unattended and attended NDA systems including such process monitoring and possible on-site analysis of DA samples that could reduce the uncertainty of the inspector measurements reducing the difference LA-UR 09-04263 between the operator’s and inspector’s measurements providing more effective and efficient IAEA GCEPs safeguards.