Trials NDA systems for uranium determination in waste drums applied active neutron method

Suwaki, Takuro*; Zaima, Naoki; Nakashima, Shinichi ; Nakatsuka, Yoshiaki; Fujiki, Naoki*; Kureta, Masatoshi   ; Ozu, Akira  

Japan Atomic Energy(JAEA) configurated the non-destructive assay (NDA) systems, which applied to the bulk state nuclear inventory and actual uranium bearing waste drums generated from Ningyo-Toge uranium plants. The methodology of newly active neutron assay systems (JAWAS-N) is based on the fast neutron direct interrogation (FNDI) method developed by NSEC. The systems are composed of neutron generator and He-3 proportional counters with concrete structures functioned as reflector or shielding. FNDI method is defined as followings. Neutron generator produces pulses of 14 MeV neutrons that are directed into drum to induce U-235 fissions in matrix. Secondary fission neutrons generated from U-235 with fast or epithermal neutron energy will be detected by He-3 proportional counters with the diffusion decay time on the order of hundreds micro-second. Neutron detectors which are designed to detect only fast and epithermal neutrons, will be extracted fission neutrons by mathematical analysis methods and be determined U-235 mass. The Systems will be contributed to the field of material accountancy in Ningyo-Toge uranium plants. The systems' verifications through the mockup tests and trials for actual waste drams measurement will be reported.