Document: 10 CFR Part 50
Document ID: ebc72932-4988-4c38-b485-e106d10d737c
Document Type: cfr
Title: Alternate fracture toughness requirements for protection against pressurized thermal shock events.
Source: 10 CFR Part 50
Source URL: https://www.ecfr.gov/current/title-10/part-50/section-50.61a
Revision Date: 
Chapter: 
Section ID: 50.61a
CFR Part: 50
CFR Title: 10

Content:
imum credible heat-average residual must be calculated using Equation 10 of this section. The value of σ used in Equation 10 of this section must be obtained from Table 5 of this section. ( iii ) The licensee shall estimate the slope of the embrittlement model residuals (estimated using Equation 8) plotted as a function of the base 10 logarithm of neutron fluence for the specific data set. The licensee shall estimate the T-statistic for this slope (T SURV ) using Equation 11 and compare this value to the maximum permissible T-statistic (T MAX ) in Table 6. For surveillance data sets with greater than 15 data points, the T MAX value must be calculated using Student's T distribution with a significance level (α) of 1 percent for a one-tailed test. ( iv ) The licensee shall estimate the two largest positive deviations ( i.e., outliers) from the embrittlement model for the specific data set using Equations 8 and 12. The licensee shall compare the largest normalized residual (r *) to the appropriate allowable value from the third column in Table 7 and the second largest normalized residual to the appropriate allowable value from the second column in Table 7. ( v ) The ΔT 30 value must be determined using Equations 5, 6, and 7 of this section if all three of the following criteria are satisfied: ( A ) The mean deviation from the embrittlement model for the data set is equal to or less than the value in Table 5 or the value derived using Equation 10 of this section; ( B ) The T-statistic for the slope (T SURV ) estimated using Equation 11 is equal to or less than the Maximum permissible T-statistic (T MAX ) in Table 6; and ( C ) The largest normalized residual value is equal to or less than the appropriate allowable value from the third column in Table 7 and the second largest normalized residual value is equal to or less than the appropriate allowable value from the second column in Table 7. If any of these criteria is not satisfied, the licensee must propose ΔT 30