Decommissioning an Uranium and Thorium Facility A Radiation Protection Approach

摘要

Decommissioning means actions taken at the end of the useful life of a facility in retiring it fromservice with adequate regard for the health and safety of workers and members of the public. In the present work,we introduce a radiation protection approach for the removal of radioactive material to the extent that the facilityor site becomes available for use without restriction. The facility to be decommissioned is a fuel cycle pilot plantthat operated with natural uranium and thorium for almost two decades and then, kept inactive for about 10 yearsat the Nuclear and Energy Research Institute - IPEN. Even after this long period of inactivity, it has presentedsignificant levels of radiation and contamination spread over the floor, walls, windows, doors and ceiling. Thefuel cycle pilot plant was completely dismantled, remaining only the walls and the concrete structures. In thiswork we present the job done to restore the area. According to each step of dismantling a continuous monitoringof the contaminated surfaces was carried out including the survey of the deep material from the floor and walls.The material identified as radioactive waste was stored into appropriated metal drums. A radiation protectionteam guided this stage of the work, prescribing the tasks, and the amount of material that should be removedfrom floors, windows and ceiling. For this, repetitive surveys had to be done. The results of monitoring andcontamination levels were analysed, thus guiding the next steps of the job. In this way radiation protection teamtook over the tasks, running the work with the purpose of achieving acceptable levels of radiation, restoring thearea for unrestricted use.