Reactor pressure vessel radiation damage monitoring by improved surveillance programmes

Reactor pressure vessel materials degradation and ageing due to neutron irradiation are of utmost concern for the safety and reliability of a reactor vessel during events such as pressurized thermal shock. This degradation of properties as a function of reactor operation time is conventionally monitored by surveillance programmes, which include small materials specimens of Charpy V, tensile and sometimes compact tension types. These specimens are irradiated in a higher flux than that to which the pressure vessel is exposed and subsequently tested to yield information on embrittlement of the vessel. There are several possible ways to improve the currently used surveillance programmes and the reliability of their results. The paper describes such improvements, including improved materials testing methods, possibilities of increasing the number of specimens and new ways of analysing the test results. (author). 22 refs, 7 figs, 1 tab