This paper provides an overview of work completed and in progress worldwide to study the effect of radiation on the static crack-arrest toughness, K^Ia, of reactor pressure vessel steels. The impetus for obtaining such data is the desire to realistically assess the need to repair or retire vessels that have been exposed to radiation in service, and to avoid the sometimes unnecessary conservatism associated with safety analyses when no KK^Ia data are available.

The paper reviews recent developments toward achieving an ASTM standard test method for measuring K^Ia. It demonstrates also the acceptability of using crack-arrest specimens that are appreciably smaller than those used frequently in the past, thereby increasing the practicability of studying radiation effects on K^Ia.

The review points out that the data currently available for assessing radiation effects on K^Ia are very limited: only 36 of the more than 900 test results in the Battelle/United States Nuclear Regulatory Commission (USNRC) Crack Arrest Data Bank are for irradiated specimens. Nonetheless, those limited data suggest procedures for estimating radiation effects on K^Ia that are more realistic (less conservative) than those currently specified in Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. Additional tests that include several fluence levels and wider ranges of composition are required, however, to verify the modified procedures or to reveal alternate approaches.