Improvement of precision of NRF-based NDA using monochromatic -ray beam for nuclear materials in debris of melted fuel

Shizuma, Toshiyuki; Hajima, Ryoichi; Hayakawa, Takehito; Angell, C.; Minato, Futoshi   ; Suyama, Kenya; Seya, Michio

Nondestructive assay (NDA) of actinide nuclei in spent nuclear fuel or melted fuel using a -ray beam is possible using a scattered method or a transmission method. These methods use nuclear resonance fluorescence (NRF) which is a process of nuclear excitation by photo-absorption and de-excitation by photo-emission. In the scattered method, system performance such as counting precision is affected by radiation background from the spent fuel and can be improved by using resonances at high energies where an optimum signal-to-noise ratio is obtained. In this talk, we will show calculated results on statistical uncertainties of the scattered method for various NRF cross sections in the range of 3 to 100 eV barn at excitation energies between 2 and 5 MeV. We will also mention the methodology of the transmission (self-interrogation) measurement and recent experimental results obtained using a quasi-monochromatic -ray beam.