Crack-arrest testing of irradiated nuclear reactor pressure vessel steels at the Oak Ridge National Laboratory

Crack-arrest testing of nuclear pressure vessel steels has been conducted a t Oak Ridge National Laboratory for many years. Four methods have been used to initiate fast-running cracks in crack-arrest specimens: (1) the deposit ion of a brittle weld bead using hardfacing weld electrodes, (2) water quen ching a chevron crack tip, (3) quenching the crack tip by discharging a lar ge current into the crack tip region, and (4) the use of duplex specimens. A problem often encountered with Methods 1 and 4 is the control of the widt h of the heat-affected zone (HAZ). The HAZ is generally tough and can arres t crack propagation before it has run into the test section. Irradiated cra ck-arrest specimens were prepared using Methods 1, 3, and 4. Method 1 was t he most successful, while Method 4 was the least successful. This paper wil l discuss some of the reasons for the success, or lack of, as well as the r esults of testing both a high-copper weldment and a low-copper forging in t erms of the shift and shape of the K-a toughness curve compared to the Char py V-notch shift. The present ASTM Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, K-Ia, of Ferritic Steels (E 1221-88) vali dity criteria will also be discussed in light of the results.