On performance experience and measurements with Ningyo Waste Assay System (NWAS), 2

Zaima, Naoki; Nakashima, Shinichi ; Nakatsuka, Yoshiaki; Kado, Kazumi

We developed uranium mass assay systems for 200-litter wastes drums applied neutron and measurements by NDA method. In this report we will describe measurement experiences followed by the previous report. The systems are composed of the 16 pieces of helium-3 (He) proportional counters for neutron detection. The neutron measurement methodology is consist of U (,n)F reaction and spontaneous fission of U. The extensive test trials using the known amount of uranium with different enrichment and some kinds of matrices in drums were performed. By using this NWAS we tried to determine uranium mass in the actual uranium wastes drums stored in the URCP at Ningyo-toge. The actual uranium wastes drums are of great variety, in the point of matrix, bulk density, packing condition and total uranium mass. Therefore we have tried some challenging methods which eliminate problems, and established the applicability to almost all kinds of wastes drums.