Abstract
Developing a nondestructive method for estimating material degradation before crack initiation will contribute to improvement of safety and economical efficiency of fast breeder reactor plants. In this study, fatigue tests on type 304 stainless steel at 923 K, measurements of magnetic flux density, and microscopy studies were conducted. As a result, it was shown that the maximum value of variation of magnetic flux density during the fatigue tests increased linearly in relation to the number of loading cycles and this magnetic property change was due to phase transformation.