Magnetic nondestructive evaluation of degradation of nuclear pressure vessel steels due to mechanical loading

Abstract

We performed magnetic nondestructive evaluation of degradation of nuclear pressure vessel steels due to mechanical loading as a fundamental research. We measured magnetic properties of low alloy steel samples, which were degraded due to tensile and cyclic loads. Magnetic hysteresis curves change depending on the loading conditions. The changes of the coercive force, residual magnetic flux density and permeability were obtained and analyzed in details as a function of the residual strain. Based on the above results, we performed the sensitivity analysis of magnetic property changes for the mechanical load. Finally we concluded that the incremental permeability at H = 0 is the most sensitive index for early degradation due to the mechanical loads. The feasibility of application of this magnetic technique to the evaluation of degradation due to neutron mechanical and thermal loading is now under consideration.