Implementation of dynamic cross-talk correction (DCTC) for MOX holdup assay measurements among multiple gloveboxes

Nakamichi, Hideo; Nakamura, Hironobu ; Beddingfield, D.*; Mukai, Yasunobu ; Kurita, Tsutomu 

Plutonium holdup in gloveboxes (GBs) are measured by HBAS (passive neutron based NDA, Holdup Blender Assay System) for the material control and accountancy (MC&A) at Plutonium Conversion Development Facility (PCDF). In the case that the GBs are installed close to one another, the cross-talk which means neutron double counting among GBs should be corrected properly. Though we used to use predetermined constants as the cross-talk correction, a new correction methodology for neutron cross-talk among the GBs with inventory changes is required for the improvement of MC&A. In order to address the issue of variable cross-talk contributions to holdup assay values, we applied a dynamic cross-talk correction (DCTC) method, based on the distributed source-term analysis approach, to obtain the actual doubles derived from the cross-talk between multiple GBs. As a result of introduction of DCTC for HBAS measurement, we could reduce source biases from the assay result by estimating the reliable doubles-counting derived from the cross-talk. Therefore, we could improve HBAS measurement uncertainty to about 10% which is a half of conventional system. Since the DCTC methodology can be used to determine the cross-correlation among multiple inventories in small areas, it is expected that this methodology can be extended to the knowledge of safeguards by design.