Development of scientific methods for determining the energy spectrum of neutron radiation to assess its radiation exposure

An approach to assess the radiation exposure of neutron fluxes to personnel in nuclear facilities in a wide energy range has been developed. It is based on the multisphere method, where in the process of measuring the thermal neutron counter is sequentially placed in the center of spherical moderators of various diameters. Knowledge of the sensitivity functions of such spherical detectors make it possible to reconstruct the neutron energy spectrum from the measured counting rates. The reconstruction of the initial flux spectrum is based on calculating the minimum discrepancy of the measured counting rates and obtained by convolution of the sensitivity of the neutron detector in the moderator sphere and a set of model neutron emission spectra. The developed method for assessing the radiation exposure of personnel to neutron fluxes at nuclear facilities in a wide energy range made it possible for the first time to estimate the radiation doses to personnel of facilities using fast neutron reactors. The method was tested at Institute of Nuclear Materials (Zarechniy) and Beloyarsk NPP. The correction coefficients for individual neutron radiation dosimeters obtained by the differences of the calibration field from the neutron radiation spectrum under conditions of real measurement form the basis for improving the radiation safety of nuclear facilities at the present stage of the development of science and technology.