In order to modify the fatigue design method for pressure vessel components of light water rcactors(LWRs), strain controlled fatigue tests were carried out under various environmental conditions, and the effects of temperature and dissolved oxygen (DO) contents on fatigue lives of carbon steel in LWR-simulated water environments were evaluated and analyzed.

The results of the present study are summarized as follows; 1) The decrease in fatigue life of carbon steel STS410 in BWR-simulated water environments occurs at temperatures above 200°C and with DO higher than 0.1ppm. The rate of decrease is greater at higher temperatures and higher DO concentrations. 2) To offset differences in test condition such as temperature, DO, strain amplitude etc., an new index, Rp, which represents a ratio of the environmental index P-values previously proposed, was introduced. Also a new fatigue life equation based on Rp was proposed. 3) By the new equation, the fatigue life of carbon steel under a certain environmental condition of temperature and DO can be predicted better than by the previously proposed method.