Simulation of the radiation situation during the "early" dismantling of the building structures of the Shelter object

A model of the "early" dismantling of the building structures of the Shelter object is developed in the ChNPP VRdose Planner program. The ChNPP VRdose Planner software product was developed at the Institute for Energy Technology (IFE), Norway. ChNPP VRdose Planner is a tool for real-time computer simulation of the radiological environment and actions sequence planning. The simulation is performed in a directly existing environment, while optimizing radiation protection, and makes it possible to prepare reports on work plans with dose estimates. Based on experimental data, mathematical modeling of gamma fields was carried out and spatial distributions of the power of gamma-radiation dose over the roof of the central hall of the "Shelter" object ChNPP. The distributions were analyzed to clarify the location of the most intense sources of gamma radiation, the characteristics and locations of the sources of ionizing radiation were determined, a visual display of the change in the radiation field above the roof of the Shelter object is shown. The eastern wall of the central hall is an accumulation of fragments of the reactor core in the vertical plane, located from an altitude mark of 38.0 m to an altitude of 64.0 m — about 26 m high, about 23 m wide and 3 m thick. It has been established that the dismantling of the roll-off from the pipes should be started from the western side of the Shelter, since this provides a lower level of ambient equivalent dose rate. After dismantling the "light" roof and rolling up from pipes, the ambient equivalent dose rate at the 67.5 m mark increases from 1.1 to 2.8 times. The use of the ChNPP VRdose Planner program for planning and performing installation activities, as well as the activities for the maintenance, repair and replacement of the equipment in the radiation-hazardous conditions will allow: make justified decisions about the feasibility of a particular activity; choose the best technical solutions to achieve set goals; calculate or optimize the structure of radiation protection of the personnel. The use of a computer model will allow selecting and optimizing design solutions for the unstable structures deconstruction, verify them for the compliance with the established characteristics and requirements, and create an interactive software package for the personnel training. (author)