Methodology for the scoping assessment of radioactive releases during dismantling of RBMK-1500 reactor systems with low-level contamination

The Ignalina nuclear power plant operated two reactors of the RBMK-1500 type which are now under decommissioning. Decommissioning has been started from the reactor's periphery, with dismantling of non-contaminated and low contaminated equipment and installations. This paper discusses a method for the scoping assessment of airborne radioactive releases to the environment when the number of items of equipment and the variety of installations to be addressed is significant, and separate consideration of each item becomes impractical, especially when the level of radioactive contamination is low. The method is based on the grouping of items into the manageable number of mass streams with particular geometric and other decommissioning-approach-related properties. Radioactive releases are then evaluated by application of “mass factors” that are detailed for two geometric forms - pipes and plates. These forms are the most usual outcomes from Ignalina nuclear power plant decommissioning activities performed on reactor periphery components. The method can be used for the scoping assessment of radionuclide releases considering that the radiological impact is expected to be low and, therefore, simple and straightforward solutions are sufficient for demonstration of compliance with the established radiation protection goals.