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 17 In Fig. 13 results of the parametric study performed for H eq is shown. Higher H eq increases the probability of DHC getting initiated form the volumetric flaw. 647

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00

Heq = 25 ppm Heq = 30 ppm Heq = 35 ppm Heq = 40 ppm Heq = 45 ppm Heq = 50 ppm

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a/t (%)

Fig. 13. The plot of _ with respect to the mean value of flaw depth ( = 50 microns, mean 2 = 2.875 mm, = 100 MPa) The effect of on the value of _ probability estimate is plotted in Fig. 14. The is parametrically varied in this case. The value is kept at 0 MPa, signifying that the analysis is valid for the main body of the pressure tube. During the operation of the reactor, the Deuterium gas is generated from the corrosion reaction. This Deuterium gas is absorbed by the pressure tube material which results in the increase of hydrogen concentration with time. Typically, 1 to 2 ppm of Hydrogen equivalent is picked up per year. The probability value of _ increases as the increases. As expected, the probability estimate is higher for flaw with smaller . It is seen that for higher values of , the effect of is significantly less pronounced. Thus, for a reactor which has operated for a long time, the vulnerability is high even for a relatively blunt flaw. The effect of the for different is shown in Fig. 15.