The effect of tritium and neutron irradiation on the structure and properties of reactor steels and alloys

Studies performed under ISTC Project No. 019-94 provided a database on the effect of heavy hydrogen isotopes (concentration up to 0.03 at.%), radiogenic helium and neutron irradiation predominantly on the mechanical properties of FCC 16Cr15Ni3Mo1Ti radiation-resistant reactor steel, which is produced in Russia. It was shown that loading of the steel with tritium and deuterium up to 0.03 at.% and subsequent neutron irradiation at 77 or 320 K with fluence of 1019–1020 n/cm2 led to an abrupt increase in strength characteristics, while a high plasticity (specific elongation δ=30–40%) was preserved even at extremely low temperatures. The microautoradiographic examination showed that strengthening was due to blocking of dislocations by tritium atmospheres, formed at dislocation cores. Comparative studies were performed on BCC alloys (Fe–13Cr, V–4Ti–4Cr, and V–10Ti–5Cr). Exposure to the tritium effect and low-temperature neutron irradiation was shown to lead to an almost complete degradation of their plasticity characteristics at 77 K.