APPLICATIONS OF X-BAND 30 MeV LINAC NEUTRON SOURCE TO NUCLEAR MATERIAL ANALYSIS FOR FUKUSHIMA NUCLEAR PLANT ACCIDENT

摘要

We plan to use our X-band (11.424GHz) electron linac as a neutron source for the nuclear analysis for the Fukushima nuclear plant accident. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, TRU and MA especially in epithermal (0.1-10 eV) neutrons. Therefore, we have decided to suspend the Compton scattering X-ray experiment and move the linac to the core of the experimental nuclear reactor "Yayoi" which is now under the decommission procedure. Due to the compactness of the X-band linac, the RF gun and accelerating tube and other components can be installed in a small space in the core. First we plan to perform the TOF (Time Of Flight) transmission measurement of the total cross sections of the nuclei for 0.1-10 eV neutrons. Therefore, if we adopt a TOF line of less than 10 m, the macro-pulse length of generated neutrons should be shorter than 100 ns. Electron energy, macro-pulse length, power and neutron yield are ～30 MeV, 100 ns - 1 micros, <0.5 kW and <10~(12) n/s, respectively. Optimization of the design of a neutron target (Ta, W, U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. Installation, commissioning and measurement starts in 2014. Detailed design and way how to contribute to the analysis of the Fukushima nuclear plant accident will be presented.