Year
2006
Abstract
Safeguards measurements at a Natural Uranium Conversion Plant (NUCP) have not been a traditional aspect of IAEA safeguards because it has been considered too early in the fuel cycle. However, there has been a recent emergence in interest in monitoring the Uranium conversion and enrichment process. The principle benefit of a Uranium throughput measurement at an NUCP is that it provides a direct comparison to the input receipts of the subsequent enrichment plant. The comparison of the NUCP output to the input receipts of the enrichment plant is a direct indicator of whether there is possible diversion to a clandestine enrichment facility. Under the auspices of NNSA and collaborating with ORNL (see companion paper by Ladd- Lively), we have designed, built, and fielded a Uranium flow meter that measures the flow of Uranium as Uranyl Nitrate in an NUCP. The flow meter consists of two parts: a neutron detector to measure the Uranium concentration by detection of fission neutrons from the 238U decay, and a commercial flow meter that measures the volume throughput of the Uranyl Nitrate fluid. A very clean instrumentation package was developed to acquire data from both the neutron detector and the flow meter. The data are acquired and stored using the IAEA standard UNARM (Unattended and Remote Monitoring) system. The specific location was chosen because it is a “choke point” for the conversion process line: all of the Uranium for a process line must pass through this pipe. The system was fully built and deployed at the Springfields Natural Uranium Conversion Plant in Preston, U.K. We will present a design overview including the MCNP neutronics design, pictures of the final instrument, pictures of the installed system at the Springfields plant, and a review of the data, which we have acquired since late December 2005. Finally, we will present some of the innovations used in this system to achieve the measurement results and discuss the excellent integral precision obtained from this instrument.