Vessel behavior following a through-wall crack

Abstract

A fracture mechanics model has been developed to predict the behavior of a reactor pressure vessel following the occurrence of a through-wall crack during a pressurized thermal shock event. This study has been coordinated with the Integrated Pressurized Thermal Shock (IPTS) Program at Oak Ridge National Laboratory. The fracture mechanics model uses as inputs the critical transients and probabilities of through-wall cracks from the IPTS Program. The model has been applied to predict the modes of failure for plant specific vessel characteristics. A Monte Carlo type of computer code has been written to predict the probabilities of alternate failure modes. This code treats the fracture mechanics properties of the various welds and plates of a vessel as random variables. The computer code also calculates the crack driving force as a function of the crack length and the internal pressure for critical times during the transient. The fracture mechanics model has been applied in calculations that simulate the Oconee-1 reactor pressure vessel. The model predicted that about 50% of the through-wall axial cracks will turn and follow a circumferential weld giving a potential for missiles. Missile arrest calculations predict that vertical as well as all potential horizontal missiles will be arrested and will be confined to the vessel enclosure cavity. In future work, plant specific analyses will be continued with calculations that simulate Calvert Cliff-1 and H.B. Robinson-2 reactor vessels.