Corrosion mechanism on heat transfer surface of pressure boundary materials used in nuclear environments

The ultra-high burnup more than 100 GWd/t and fast neutron spectrum tailoring are considered to be the most promising technologies applied to the advanced MOX LWRs for minimizing the electrical cost and waste management. The development of new cladding materials with the excellent irradiation properties has been conducted to realize these needs. Comparing with UO2, to increase the internal pressure by FP gas release is accelerated with the co-production of Xe and He in MOX fuels. New stainless steels with the excellent irradiation properties, creep strength and compatibilities to high temperature water were selected to attain the reliability. The irradiation assisted stress corrosion cracking through the past experience in LWR plants is possible to inhibit by new steel making process. The problems of tritium release and PCMI is possible to inhibit by ductile niobium alloy lining. (author)