The neutron detectors based on oxide scintillators for control of fissionable radioactive substances

In this work comparative response measurements and analyses of detection efficiency were carried out for oxide and alkali-halide scintillators exposed to fast and thermal neutrons from a Pu-239-Be source. The experimentally-obtained fast neutron detection efficiency for heavy inorganic (oxide) scintillators (Z >= 50) was found to reach similar to 40-50%. One of the most probable mechanism of the interactions between matter and fast neutrons is the inelastic scattering reaction (n, n'gamma); by directly measuring the occurrence of this reaction in oxide scintillators, high-efficiency fast neutron detection can be achieved, especially in the case of oxide scintillators containing heavy atomic constituents. It is concluded that the use of heavy oxide scintillators, which at the same time are efficient gamma-detectors allows the creation of a highly efficient gamma-neutron detector, which enables the high efficiency of detection of fissionable radioactive materials. In addition, detector design arrangements with associated electronic systems incorporating active protection methods were configured and tested, allowing a considerable (similar to 10(3) times) reduction in the level of registration of scattered external high-energy gamma rays. Our experimental results show that the efficiencies of fast neutron detection by different scintillator crystals are proportional to the thickness of the crystal in the range of 10-40 mm, and do not depend on the thickness of the crystal in the range of 40-100 mm. It was demonstrated the correlation between detection efficiency and the effective atomic number Z(eff) of the crystalline scintillation material.