Development of sample assay system equipped with ³He Alternative Neutron Detectors (ASAS). (2) Results of ASAS measurement test

Against the background of the serious shortage of ³He gas, design and development of a new detector equipped ZnS/¹⁰B₂O₃ ceramic scintillation neutron detectors in JAEA, with the support of the government (the Ministry of Education, Culture, Sports, Science and Technology). The design of the alternative ³He detector is referred from INVS (INVentory Sample assay system (HLNCC (High Level Neutron Coincidence Counter) type)) which is being used for the verification of MOX powder etc. and is named it as ASAS (Alternative Sample Assay System). In order to prove the Pu quantitative performance as an alternative technology, several measurement tests and comparison test with INVS were conducted using ASAS. In these tests, evaluation of fundamental performance (counting efficiency and die-away time) and uncertainty evaluations were implemented. As a result, although fundamental performance of ASAS was not achieved to the one of INVS, we could confirm that ASAS has almost the same Pu quantitative performance including measurement uncertainty as that of INVS. (author)