PSI - Issue 60

P.A. Jadhav et al. / Procedia Structural Integrity 60 (2024) 631–654 P.A. Jadhav et. al./ Structural Integrity Procedia 00 (2019) 000 – 000

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The time available (t LBB ) before a leaking flaw length becomes equal to the critical crack length (CCL) is significant with respect to the LBB evaluation. This is time available during which the leak is to be detected and the subsequent procedure need to be invoked to shut down the reactor. The statistics of the time for the TWC to become critical at sustained hot conditions, is also evaluated. The results are presented in Fig. 19. It is seen from Fig. 19 that the t LBB shows dependence on the residual stress. However, it is not dependent on the a/t ratio. The median value is around 50 hours and the 5 percentile value is around 40 hours, when the crack is located away from the rolled joint region. If the residual stresses of 100 MPa are used in the calculation, the median value reduces to around 28 hours and the 6 percentile value reduces to around 20 hours.

0 10 20 30 40 50 60 70

5% 50% 95%

t LBB (hours)

123456789101112

Case number

Fig. 19. The statistics of T LBB for the 12 cases defined in Table 3.

The CSA standard has defined a LSC for deterministic analyses as 20 mm. The time taken for this crack to grow to the size of the CCL is also estimated. The histogram is presented in Fig. 20. The 5 percentile, median and 95 percentile values obtained are 33, 43.3 and 52.6 hours respectively. The residual stress is not considered while deriving these results. The statistics of the CCL is also evaluated. The histogram of CCL is shown in fig. 21. The 5 percentile, median and 95 percentile values obtained are 33.2, 40.3 and 46.7 mm respectively.