Advances in fracture mechanics analysis of primary system performance under operating and accident conditions

The methods of Linear Elastic Fracture Mechanics and of Elastic Fracture Mechanics have been validated for prediction of pressure vessel performence by the Intermediate Vessel Test program results at the Oak Ridge National Laboratory. The test results from both hydraulically and pneumatically loaded vessels are in very good agreement with the pretest predictions of vessel failure for the given conditions of pressure, temperature, material, properties, and type and size of flaw. A second advance in fracture mechanics technology has been made in thermal shock analysis. This advance has been verified by the confirmatory results of testing small thick-walled cylinders under thermal shock conditions in the Heavy Section Steel Technology program, and of warm prestressing tests at the U.S. Naval Research Laboratory. The analyses developed in these efforts have shown that operational pressure-temperature transients can be effectively modeled and applied to pressure vessel materials having appropriate mechanical properties simulating radiation embrittlement, and that the crack initiation/arrest conditions predicted will occur. Thirdly, the technology of crack arrest has reached a level wherein standardization of test specimens and testing methods is now possible and, indeed, is underway. The detailed factors which affect arrest of running cracks, and how those factors must be evaluated to permit determination of a minimum toughness descriptive of crack arrest are better understood. (Auth.)