NONPROPAGATING CRACKS OF CARBURIZED MATERIALS CAUSED BY THERMAL STRIPING IN SODIUM

In order to investigate crack growth characteristics due to thermal st riping in liquid sodium coolant used for fast breeder reactors (FBRs), thermal striping tests in sodium have been conducted using Type 304 s tainless steel and material produced by plasma carburizing Type 304 st ainless steel. The results showed that the threshold stress intensity factor range, derived from a thermal stress analysis under the conditi on of plane stress, could be used to predict the final lengths of the nonpropagating cracks. The depths of nonpropagating cracks increased w ith increasing carbon content. This tendency was attributed to the dif ference of the str-ess intensity factor range, caused by the differenc e ill Young's moduIi of the materials.