Integrity assessment for safety relevant nuclear piping

• Description of the German Basis Safety Concept and Integrity Concept is presented.
• Application is demonstrated for the main feed water line of a PWR plant.
• Leak-before-break qualification of nuclear power plants in India.
• Practical application to PHT system piping of a pressurized heavy water reactor.
• Evaluation of leakage size crack and stability analysis verified by experiment.

The failure behavior of pipes and piping components (e.g. straight pipe, pipe bend, T-joint) with and without cracks under different loading conditions has been investigated in numerous experimental and analytical/numerical research projects. The results of these projects were used to adjust and to verify different methodologies and procedures to calculate the failure loads, the respective critical crack sizes as well as the leak area and the leak rates. On the basis of the actual material characteristics, the actual as-built configurations and design of the piping systems, the knowledge of possible failure mechanism, concepts for the assessment of the integrity of the systems could be developed for the different actual as well as for postulated loading conditions. Based on the integrity assessment the leak before break behavior and break preclusion of safety relevant nuclear piping can be demonstrated. Examples are presented of the German assessment procedure for a main feed water line of a PWR as well as for the Indian assessment procedure for the primary heat transport system piping of a PHWR.