Abstract
High cycle thermal fatigue is one of postulated failure modes at the pipes of the cooling systems of the nuclear power plants. We examined this phenomenon and identified heat transfer coefficient, wall thickness and frequency of temperature fluctuation of fluid as dominant parameters. Thorough the fmite element analysis, we could obtain the curves to evaluate the effects of dominant parameters. And using these curves and theoretical equations, we proposed the frame work of evaluation method of high cycle thermal fatigue. As a result, the evaluation has found to be more accurate than current guideline of JSME and have proper safety margin against the actual phenomenon.