Characteristics of neutron fields at pool-type research nuclear reactors

Abstract

The article presents results of experimental determination of the characteristics of neutron fields behind the biological shielding of reactor facilities in the physical hall of pressurized water research reactors of the pool type. In the work, measurements of the energy distribution of the neutron radiation flux density, determination of anisotropy and correction factors for individual dosimeters were carried out. The energy distribution of the neutron radiation flux density was obtained using an MKS-AT1117M multi-sphere dosimeter-radiometer with a BDKN-06 detection unit and a set of polyethylene moderator spheres. Based on the results of determining the energy distribution of the neutron radiation flux density, the average values of the neutron energy were established, which are in the energy range: 0.06–0.35 MeV. The difference between neutron fields at the surveyed personnel workplaces and neutron fields in which individual dosimeters are calibrated leads to an additional error in estimating such dosimetric quantities as ambient dose equivalent, individual dose equivalent or effective dose. The performed studies allow to improve the system of individual dosimetric control based on the cycle of improvements: new knowledge – experimental studies – implementation of research results – regulation of activities to reduce the exposure of workers – analysis of the data obtained – new knowledge. The radiation anisotropy was estimated from the results of measurements of the accumulated dose of neutron radiation by individual thermoluminescent dosimeters placed on four vertical planes of a hu-man phantom. Adequate estimates of the effective dose to personnel can be obtained using correction factors for individual dosimeters. For various workplaces and methods, the correction factors range from 0.04 to 0.7. © 2022, Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev. All rights reserved.