APPLICATION OF THE LIMITED FREQUENCY-UNANNOUNCED ACCESS STRATEGY MEASUREMENT TECHNOLOGY IN GAS CENTRIFUGE ENRICHMENT PLANTS*

As part of a limited frequency—unannounced access inspection strategy for international safeguards, a gamma ray measurement technique for confirming the absence of highly enriched uranium inside gas centrifuge enrichment plant cascade header pipes has been developed by the U.S. Enrichment Safeguards Program, and equipment for application of this measurement technique by an international safeguards inspector has been designed. This pipe measurement strategy is based on a two-phase measurement approach that is capable of verifying whether the enrichment of the UFs gas currently in a pipe exceeds 20% U-235 and whether UFs gas exceeding 20% U-235 has been in a pipe within the last 24 h. An automated measurement process sequence has been incorporated into the firmware of a portable multichannel analyzer to lead an international safeguards inspector through the measurement sequence, and implementation and inspection procedures have been developed. Described are the verification technique, the detection equipment, and the automated decision process that have been developed by U.S. Enrichment Safeguards Program participants at Los Alamos National Laboratory and Martin Marietta Energy Systems, Inc., Oak Ridge Gaseous Diffusion Plant. Also noted are measurement technology developments from other countries that were useful in developing the U.S. Enrichment Safeguards Program's gamma ray measurement technique. Results from an initial International Atomic Energy Agency session for evaluation of the verification technique, the detection equipment, and the procedures for their use are summarized.