Document: 10 CFR Part 50
Document ID: a6c1b81f-bcf5-4ef9-9e8b-2a055aaed0aa
Document Type: cfr
Title: 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-50.61
Revision Date: 
Chapter: 
Section ID: 50.61
CFR Part: 50
CFR Title: 10

Content:
the irradiated and unirradiated conditions must be small enough to permit the determination of the 30-foot-pound temperature unambiguously. ( C ) Where there are two or more sets of surveillance data from one reactor, the scatter of ΔRT NDT values must be less than 28 °F for welds and 17 °F for base metal. Even if the range in the capsule fluences is large (two or more orders of magnitude), the scatter may not exceed twice those values. ( D ) The irradiation temperature of the Charpy specimens in the capsule must equal the vessel wall temperature at the cladding/base metal interface within ±25 °F. ( E ) The surveillance data for the correlation monitor material in the capsule, if present, must fall within the scatter band of the data base for the material. ( ii ) ( A ) Surveillance data deemed credible according to the criteria of paragraph (c)(2)(i) of this section must be used to determine a material-specific value of CF for use in Equation 3. A material-specific value of CF is determined from Equation 5. ( B ) In Equation 5, “n” is the number of surveillance data points, “A i ” is the measured value of ΔRT NDT and “f i ” is the fluence for each surveillance data point. If there is clear evidence that the copper and nickel content of the surveillance weld differs from the vessel weld, i.e. , differs from the average for the weld wire heat number associated with the vessel weld and the surveillance weld, the measured values of ΔRT NDT must be adjusted for differences in copper and nickel content by multiplying them by the ratio of the chemistry factor for the vessel material to that for the surveillance weld. ( iii ) For cases in which the results from a credible plant-specific surveillance program are used, the value of σΔ to be used is 14 °F for welds and 8.5 °F for base metal; the value of σΔ need not exceed one-half of ΔRT NDT . ( iv ) The use of results from the plant-specific surveillance program may result in an RT NDT that is