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on 6/20/24 at 9:40 AM
Participants from 14 organisations, representing 11 countries, performed the benchmark exercise. Each participant provided a high-level summary of the leak-before-break (LBB) requirements in their country and documented the computational codes and approaches that they used in their evaluations. The participants determined whether the baseline problem would meet their country’s LBB acceptance criteria and provided supporting information. This information included the leak rate detection limit (LRDL), the leak rate (LR) used to determine the leakage crack size (LCS), the LCS value and the critical crack size (CCS).
The high-level summary of the LBB requirements in each of the participating countries revealed that the basic tenets and underlying principles of the LBB philosophy among the countries are generally consistent. Most countries’ procedures are rooted in NRC SRP 3.6.3, but virtually every country has modified either the analysis or the acceptance procedure based on additional knowledge that has been gained since the establishment of NRC SRP 3.6.3. Some of the more common modifications include explicitly allowing a lower LRDL, allowing a lower LRDL margin, requiring an additional subcritical cracking analysis to demonstrate that LBB or inspection intervals are not challenged, and requiring that worst-case strength and toughness properties are chosen from the base and weld metal properties. These modifications represent a natural progression of both technical and operational knowledge since the NRC SRP 3.6.3 was first established.
