Nondestructive Assay of Plutonium in Spent Nuclear Fuel Assembly in Water Pool

We propose a new nondestructive assay method for 235U, 239Pu, and minor actinides in spent nuclear fuel assembly in a water pool. Nuclear fuel materials are detected using nuclear resonance fluorescence (NRF) with laser Compton scattering (LCS) gamma-rays, which are generated by collision of high energy electrons and laser photons. This method can identify each isotope of interest hidden in heavy shields such as lead plates with a thickness of several centimeters. We have demonstrated to detect 208Pb shielded by a 15-mm thickness iron plate using an available LCS gamma-ray source at the AIST. We have also detected two nuclides of 12 C and 14N with wide spread LCS gamma-rays. We have designed an extremely high-flux LCS gamma-ray source based on a new generation electron accelerator of the energy recovery linac and the fiver laser. A simulation calculation shows that we can detect 1% fraction 239Pu in all the fuel rods with statistical error lower than 2% using the proposed high flux LCS gamma-ray source in the measurement time of 4000 s.