Reactor dosimetry in NPP lifetime management and decommissioning tasks

•The RD methodology developed at INRNE on the state-of-the-art level is presented.•The relations between RD and other disciplines involved in PTS analysis are illustrated.•The methodology enhancement for decommissioning purposes is discussed.•Tasks and directions of the further methodology improvement are proposed.

The methodology developed in the Institute for Nuclear Research and Nuclear Energy of Bulgarian Academy of Sciences and used for the reactor pressure vessel and “surveillance” neutron fluence evaluation is presented. It includes both calculation aspects and experimental measurement used for the calculation verification. The methodology is being developed and improved so to be in consistency with the state-of-the-art requirements. The main tools of this methodology are the calculation codes together with the approved measurement technique for activity determination of the irradiated samples. These tools will be applied in the development of a new methodology for reactor system radiological characterization needed for decommissioning purposes. The fast neutrons causing material damaging as well as the lower energies’ neutrons inducing materials activation will be considered. The measured activity of irradiated samples from decommissioned reactors will be used in the verification procedure.