Ruling-out of fractures in pressure boundary pipings. Pt. 2. Application to the primary coolant piping

The experiments and the relevant interpretation of the results, described in Part 1: Experimental studies and their interpretation, are applied to primary coolant piping. Simple fracture mechanics approaches are shown which allow a conservative calculation of failure pressure and failure moment. These calculations are verified by experiments on pipes with longitudinal and circumferential cracks. The experiments were performed both with and without reservoirs under reactor operating conditions (pressure, bending, temperature, material) on part-through and through-wall defects. The interpretation of tests and calculation methods allow a conservative evaluation of critical defect sizes. Leak-before-break behaviour is shown. The application of the tests and calculations on primary components is shown for the primary coolant pipe with anticipated longitudinal and circumferential defects. The paper considers reactor systems, design fabrication, stress analysis, material, non-destructive testing, quality control and in-service inspection. These parameters are essential to an understanding of the leak-before-break behaviour. On the basis of the extreme toughness of the materials, the known loads, the high level of non-destructive examinations, the leakage monitoring system and the high quality of manufacture and processing it is shown that a spontaneous failure need not be postulated. (author)