THERMAL ANNEALING OF WWER-440 NUCLEAR REACTOR PRESSURE VESSEL INTERNALS: PRESENT STATUS

Reactor pressure vessel (RPV) of light water reactor and its internals are the most important components of any nuclear power plant. RPV and its internals are exposed to high temperatures, pressures and intensive neutron flux during the operation. These conditions lead up to material degradation - especially radiation hardening and embrittlement. Paper presents the annealing treatment as one of the possible solutions to provide and re-establish sufficient mechanical properties of RPV internals during the operation. The first part of the poster is dedicated to the description of equipment which is used for the annealing of unirradiated and irradiated materials at the UJV Rez hot cell facility. Following part shows selection of unirradiated material for definition of original mechanical properties. Next part is an overview of selected annealing regimes. The main section is focused on definition of mechanical properties (especially hardness) of original and annealed material of WWER 440 type reactor internals as well as on methods and analyses employed to study of mechanical properties changes. The final part discusses the next planned steps in the solution of the research project TH02020565: "Assurance of Safe and Long Term Operation of Nuclear Reactor Pressure Vessel Internals" which is realized in the period from 2016 to 2020 with the support of Technology Agency of the Czech Republic.