Verification of irradiation conditions at the LVR-15 research reactor for monitoring of long-term radiation damage of concrete specimens

The aim of the experiments is to irradiate concrete specimens in the research reactor for reasonable period of time (1-2 years), which corresponds to 80 years of operation of the nuclear power plant.It represents neutron fluence higher than 1·10¹⁹ n/cm² for neutrons with energy greater than 1 MeV. The ratio of the total neutron fluence to these fast neutrons should be approximately 20. The temperature of the concrete must not exceed 93 grad C (this also applies to the centre of the specimen).It would be good to maintain the temperature below 65 grad C which corresponds to the real operation power. At a temperature of 93 grad C a structural changes in the concrete occur. The aim of the designed experiment was to test the possibility to irradiate concrete specimens under required conditions in the LVR-15 reactor. The experiment also allowed to determine the thermal conductivity of serpentine concrete. The thermal conductivity of the material is an important parameter for thermo-technical calculations. This value is significantly different for various types of concrete. Calculations for different levels of reactor power were compared with measured data (validation of thermo-technical calculations). During the experiment the method of extracting and analysing the gases generated during irradiation was verified. A significant amount of gas is generated during irradiation. This gas must be regularly released,otherwise there is a risk of capsule damage due to high pressure. (authors)