Specific Features of Structural-Phase State and Properties of Reactor Pressure Vessel Steel at Elevated Irradiation Temperature

摘要

This paper considers influence of elevated irradiation temperature on structure and properties of 15Kh2NMFAA reactor pressure vessel (RPV) steel. The steel is investigated after accelerated irradiation at 300 degrees C (operating temperature of VVER-1000-type RPV) and 400 degrees C supposed to be the operating temperature of advanced RPVs. Irradiation at 300 degrees C leads to formation of radiationinduced precipitates and radiation defects-dislocation loops, while no carbide phase transformation is observed. Irradiation at a higher temperature (400 degrees C) neither causes formation of radiation-induced precipitates nor provides formation of dislocation loops, but it does increase the number density of the main initial hardening phase-of the carbonitrides. Increase of phosphorus concentration in grain boundaries is more pronounced for irradiation at 400 degrees C as compared to irradiation at 300 degrees C due to influence of thermally enhanced diffusion at a higher temperature. The structural-phase changes determine the changes of mechanical properties: at both irradiation temperatures irradiation embrittlement is mainly due to the hardening mechanism with some contribution of the nonhardening one for irradiation at 400 degrees C. Lack of formation of radiation-induced precipitates at T = 400 degrees C provides a small Delta T-K shift (17 degrees C). The obtained results demonstrate that the investigated 15Kh2NMFAA steel may be a promising material for advanced reactors with an elevated operating temperature.