DL-EPR measurements on a sensitised Type 304 stainless steel pipe section

lntergranular stress corrosion cracking has been the most frequent failure mode in BWR primary piping. Modern, low carbon stainless steels, improved welding and water chemistry has reduced the amount of IGSCC drastically. Simultaneously the need for investigations on sensitisation has decreased. This could cause a lack of knowledge transfer which could be harmful should the problem arise again. The SAFIR 2014 ENVIS project got permission to use a pipe section from a BWR steam line, suffering from IGSCC, for measurements on the degree of sensitisation. The intentions were twofold: to transfer the knowledge on IGSCC sensitisation measurements from the main investigator (who performed these measurements in the ao·s for BWR primary piping) to the younger generation, and to actually measure the degree of sensitisation as a function of distance from the weld fusion line. Both objectives were achieved, and this report summarises the results. The performed DL-EPR measurements showed that the SS2333 material (Type 304) is slightly sensitised. The highest values were measured at a distance of 6.25 mm from the fusion line. The crack in the pipe was located still further away from the fusion line, between 7 and 12 mm. That the highest DL-EPR value was measured closer to the fusion line than the location of the crack is understandable, since the crack was located in a region where the most severe repair had been performed (based on the appearance of the weld.) The DL-EPR measurements, again, where measured from a region without a crack, and with less severe repair welding. The results show also that intergranular stress corrosion cracking is the result of the three parameters, stress, material and environment. In this case, sensitisation has played a role, but the probably high residual stresses from the repairs during the assembly welding, was likely also been decisive. The third factor, the environment, is involved since the steam environment is oxidising.