Positron annihilation studies of RPV model alloys

Positron annihilation spectroscopy (PAS) is a sensitive probe for studying the structure of defects in solids. The development of structural materials for the main components of nuclear power plants is very difficult compared to the development or selection of materials for the nuclear reactors and traditional thermal power plants. Among the diversity of factors governing the serviceability of structural materials that constitute the main components of nuclear power plants the processes inducing radiation swelling and defect-damage, as well as those that enhance creep and embrittlement, increase the brittle-ductile transition temperature and reduce corrosion-fracture resistance are of greatest hazard. Studies of older East and West water reactor pressure vessel (RPV) steels shown that similar degradation in mechanical properties during equivalent neutron irradiation. In both cases with the identification of and a reduction in the deleterious element concentration the sensitivity of the steel to the neutron irradiation was reduced. Enhancement of parameters, service life, and reliability of conventional thermal and nuclear power plants requires the development of new refractory and corrosion-resistant (stainless) steel and other alloys and also the improvement of existing structural materials capable of long-term reliable operation under high temperatures and stresses. (author)