Design and Implementation of ~(10)B + ~3He Integrated Continuous Monitor (BHCM) to Holdup Monitoring in Glove Boxes

摘要

In order to improve the safeguards and nuclear material accountancy of holdup measurements and to establish an alternative technology for ~3He shortage, we have designed and implemented the ~(10)B + ~3He Integrated Continuous Monitor (BHCM) to continuously monitor the holdup in glove boxes at Plutonium Conversion Development Facility (PCDF). The purpose of the BHCM is to record the totals rate from holdup in a glovebox as a function of time to determine the long-term trend with the actual process operation knowledge. The BHCM will also take continuous monitoring data to prove the stability of ~(10)B technology in the relatively high gamma-ray exposure of MOX process monitoring field. Prior to starting the continuous monitoring, we could confirm the consistency between Monte Carlo N-Particle transport (MCNPX) code simulations and actual measurement on the each detector tube (~(10)B and ~3He) in the BHCM. In addition, since the BHCM is equipped with differentially moderated detectors (bottom and top), the change in the average neutron emission energy due to the change in alpha of the holdup can be measured. The change in alpha that we expect to measure is from the fluorine contamination in the glove-box. This will reduce the average neutron energy of the emitted neutrons and the neutron energy spectrometry of the BHCM can provide an estimate of the F (alpha,n) neutron fraction for the emitted neutrons. We believe that this technology can be also extended to improve measurement uncertainty in the Pu quantitative assay when using the Totals neutrons. In this paper, we present BHCM design, set up results of BHCM on the glovebox including comparison between MCNPX simulations and actual measurement and demonstration of process monitoring during operation to see the relation between Totals trend and operation status by using ~(10)B tubes.