Prediction of radiation doses during the dismantling of a maintenance cooling reservoir of RBMK-1500 reactor

Abstract

*Decommissioning of the Ignalina Nuclear Power Plant involves multiple problems. Personnel radiation safety during the dismantling activities is one of them. In order to assess the optimal personnel radiation safety, the modelling is performed by means of computer code “VISIPLAN 3D ALARA Planning tool” developed by SCK CEN (Belgium). In this paper it was used for the evaluation of direct gamma radiation from the radioactive equipment to personnel when carrying out dismantling activities and selection of gamma radiation shielding geometry (structure), shielding materials and positions. A modelling of radiation doses during the dismantling of the maintenance cooling reservoir (MCR) of RBMK-1500 reactor has been performed in this paper. The basic MCR model’s development was based on internal contamination and the existing geometrical data. The assessment of workers exposure was performed to comply with ALARA. The effective doses to the workers were calculated for different strategies of reservoir dismantling. The impacts of dismantling tools, shielding types, variation of parameters such as shielding distance, shielding installation time and exhaust ventilation flow rate during the dismantling of reservoir on effective doses were analyzed. The total effective personnel doses were obtained by summarizing the effective personnel doses from various sources of exposure, i.e., direct radiation from radioactive equipment, internal radiation due to inhalation of radioactive aerosols, and direct radiation from radioactive aerosols arising during hot cutting in premises.