V. V. Yehorov, L. I. Pavlovsky, D. O. Khomenko
Institute for Safety Problems of Nuclear Power Plants,
NAS of Ukraine, 36a, Kirova st., Chornobyl, 07270, Ukraine
The territory of the industrial site of the New Safe Confinement of the Shelter object (NSC SO) was investigated after the installation of the arch structure in the design position over the destroyed Unit 4 of the Chornobyl NPP. Radiation studies of the industrial site were carried out by the specialists of the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine in 2020–2021. The subject of research was the distribution of the dose rate values and the characteristic of the angular distribution of the intensity of gamma radiation at the NSC SO industrial site. Comprehensive studies of radiation conditions include both dose rate measurements and the angular distribution of gamma radiation intensity. The study of the angular distribution of the intensity of gamma radiation and the determination of the sources forming the dose rate in the research sites was carried out using own developments — the ShD-1 device  and the MKS-07 “Poshuk” radiometer-dosimeter with an external collimated detector. This equipment was previously successfully tested and was repeatedly used at the stage of pre-design studies and during the implementation of projects at the site of the Chornobyl NPP. Based on the results of modern research, a comparative analysis was carried out with the results of research before the construction of the arch structure (2004) and during the construction of the NSC (2010). At all points of the study, a decrease in the dose rate from 5 to 15 times was recorded. The decrease is due to the removal during the construction period of all local sources of ionizing radiation from the territory of the industrial site, as well as to the construction of new structures, which are protective barriers for work performed at the NSC SO site. Insignificant changes in the angular distribution of gamma radiation were found, which are associated with the construction of new structures in the middle of the SO and on the industrial site. The research results can be useful for the selection of sites for the construction of new facilities for radioactive waste management in the process of transformation of the SO into an ecologically safe system.
Keywords: radiation research, source of ionizing radiation, dose rate, angular distribution of gamma radiation, New Safe Confinement, Shelter object.
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