Potential Roles for Unattended Safeguards Instrumentation at Centrifuge Enrichment Plants

As global uranium enrichment capacity under international safeguardsexpands, the International Atomic Energy Agency (IAEA)is challenged to develop effective safeguards approaches at gaseouscentrifuge enrichment plants, particularly high-capacity plants,while working within budgetary constraints. New safeguards approachesshould detect and deter plausible diversion scenarios,but should also strive for efficiency advantages in implementation,for both the IAEA and operators. Under the IAEA’s Statelevelapproach to safeguards implementation, the IAEA needsa flexible toolbox of technologies allowing tailoring of the safeguardsmeasures for each enrichment facility. In this paper, thepotential roles, development status and remaining developmentquestions for three different types of unattended measurementinstrumentation are discussed. Online Enrichment Monitors(OLEM) could provide continuous enrichment measurementfor 100 percent of the declared gas flowing through unit headerpipes. Unattended Cylinder Verification Stations (UCVS) couldprovide unattended verification of the declared uranium massand enrichment of 100 percent of the cylinders moving throughthe plant, but also apply and verify an “NDA Fingerprint” topreserve verification knowledge on the contents of each cylinderthroughout its life in the facility. Sharing of the operator’s loadcell signals from feed and withdrawal stations could count all cylindersintroduced to the process and provide periodic monitoringof the uranium mass balance for in-process material. A fictitious“Facility X” is used to illustrate qualitatively how the data streamsfrom these instruments could be integrated in a way that addressesall prominent diversion scenarios. An example case study in FacilityX demonstrates quantitatively how unattended instrumentscould simultaneously improve effectiveness and efficiency overtoday’s measures. In this case study, load-cell monitoring ensuresthat only declared cylinders are introduced to the process areas,and that the total uranium mass balance of in-process materialindicates no evidence of undeclared excess production. The integrationof load cell, OLEM and UCVS data streams provides100% verification of declared cylinder flow and enables the periodicverification of the declared 235U mass balance in the plant.The case study illustrates how the continuous presence and relativelyhigh accuracy of the OLEM and UCVS 235U assay couldsupport the detection of protracted diversion scenarios in a waythat has never before been viable for the IAEA, due to accuracyand operational limitations associated with portable instrumentsfor cylinder verification. Such unattended instrumentation couldalso reduce or eliminate the need for announced inspections, andsignificantly reduce the need for drawing samples from gas andcylinders during inspections. This paper uses data and informationgathered from technology development projects in the internationalsafeguards community to illustrate and evolve the IAEA’svision for unattended technology in enrichment plant safeguards,and to provide the IAEA’s perspective on remaining developmentchallenges for these unattended instruments.