Issue 41

G. G. Cunto et alii, Frattura ed Integrità Strutturale, 41 (2017) 332-338; DOI: 10.3221/IGF-ESIS.41.44 338 Fig. 4 shows that all the material zones and crack orientation fulfill the requirements for LBB application, since all critical cracks size considered are more than twice the size of the crack that would causes a 10gpm leak. For the critical crack size found in the weld, which is the region that presented the lowest toughness, elastic-plastic J-Integral analysis was performed, to verify the possibility of tearing instability failure. In this analysis, two important consideration shall be taken, specifically, initiation or first extension of an existing crack denoted as J IC , and stability or instability of a growing crack. If the material toughness J IC is bigger than the applied value of J, the not occurrence of crack initiation or significant growth is guaranteed. When the J IC is less than the applied J, the crack growth must be evaluated by a ductile instability analysis, e.g. Tearing Modulus analysis, to determine if the crack grows in a stable manner, or if the crack will grow unstably resulting in a structural collapse [6]. The applied J calculated using Eq. 4, considering the normal plus seismic SSE loads conditions, the size of critical through- wall crack found for the weld zone, and the material properties for the weld zone found in the hot tensile tests, was: J aplied = 164 kJ.m -2 This value is less than the lower J IC value of 168 kJ.m -2 found in the toughness test performed in weld zone. This way, it was demonstrated that the failure by tearing instability will not occur under the considered conditions. C ONCLUSIONS he lowest critical crack size was found for the base material presenting circumferential orientation crack. After a certain crack size, the leak rate in base material is much higher than for the HAZ and for the weld zones. For the critical crack size found in the weld, Integral-J analysis was performed, considering failure by tearing instability. It has been demonstrated that the failure by tearing instability will not occur under the considered conditions of this project. All critical cracks size found for the three different zones and two different orientation, are more than twice the size of the crack that would causes a 10 gpm leak. Thereby, it can be concluded that the investigated 316LN austenitic steel pipes welded using 316L can be applied in the LABGENE reactor coolant loop considering LBB criterion. A CKNOWLEDGMENTS his work has been performed as a part of the LABGENE program supported by Navy Technological Center in São Paulo. R EFERENCES [1] NUREG-1061, Report of the U. S. Nuclear Regulatory Commission Piping Review Committee, Piping Review Committee, NRC, Volume 1-5, (1984). [2] NUREG-0800, SRP - Standart Review Plan, Nuclear Regulatory Guide, United States Nuclear Regulatory Commission, (1987). [3] Norris, D. M., Chexal, B., PICEP: Pipe Crack Evaluation Program (Revision 1) EPRI NP-3596-SR, (1987). [4] Zahoor, A., Ductile Fracture Handbook, NP-6301-D Research Project, Electronic Power Research Institute, (1989). [5] REGULATORY GUIDE 1.45, Reactor Coolant Pressure Boundary Leakage Detection System, USNRC-United States Nuclear Regulatory Commission, (2007). [6] Anderson, T.L, Fracture Mechanics: Fundamentals and Applications. 3rd Edition, CRC Press, Taylor & Francis Group, (2005). T T