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This paper presents evaluations of the onset of fracture and crack arrest in a thick-walled A508 steel cylinder (530-mm outside diameter, 240 mm inside diameter and 910 mm long) for thermal shock loading conditions similar to those postulated for a nuclear reactor vessel. The evaluations include static finite-element as well as static and dynamic finite-difference analyses of the flawed cylinder. The calculated values of the stress-intensity factor at initiation and at arrest are compared with the fracture toughness (KIc) and crack arrest toughness (KIm) values obtained from small specimens tested at the same temperatures. The stress-intensity factor at initiation agrees with KIc, while the stress-intensity factor at arrest is less than KIc and consistent with estimates of KIm. Dynamic effects (such as inertial effects) at arrest are negligible, and the static and dynamic analyses give the same result for the rather small (12 mm) crack extension experienced by the vessel. However, a dynamically calculated large (93 mm) crack extension for a hypothetical brittle steel is 52 percent longer than predicted by the static analysis. It follows that dynamic effects may not be negligible for very deep penetrations of the vessel wall.

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Intermediate test vessel V-8, a 152-mm-thick vessel fabricated of SA533, grade B, class 1 steel, was pressurized to failure at -23°C. The vessel contained a fatigue-sharpened notch adjacent to a half-bead weld repair that had not been stress relieved. Residual stresses and fracture toughnesses were determined before the pressure test by measurements on a prototypical weld, and fracture predictions were made by linear elastic fracture analysis. Predictions agreed well with test results, demonstrating the important influence of high residual stresses on fracture behavior.

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