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:
t be based upon modifications to equipment, systems, and operation of the facility in addition to those previously proposed in the submitted analyses that would reduce the potential for failure of the reactor vessel due to PTS events, or upon further analyses based upon new information or improved methodology. ( 7 ) If the limiting RT PTS value of the plant is projected to exceed the screening criteria in paragraph (b)(2), or the criteria in paragraphs (b)(3) through (b)(6) of this section cannot be satisfied, the reactor vessel beltline may be given a thermal annealing treatment to recover the fracture toughness of the material, subject to the requirements of § 50.66 . The reactor vessel may continue to be operated only for that service period within which the predicted fracture toughness of the vessel beltline materials satisfy the requirements of paragraphs (b)(2) through (b)(6) of this section, with RT PTS accounting for the effects of annealing and subsequent irradiation. ( c ) Calculation of RT PTS . RT PTS must be calculated for each vessel beltline material using a fluence value, f, which is the EOL fluence for the material. RT PTS must be evaluated using the same procedures used to calculate RT NDT , as indicated in paragraph (c)(1) of this section, and as provided in paragraphs (c)(2) and (c)(3) of this section. ( 1 ) Equation 1 must be used to calculate values of RT NDT for each weld and plate, or forging, in the reactor vessel beltline. Equation 1: RT NDT = RT NDT(U) + M + ΔRT NDT ( i ) If a measured value of RT NDT(U) is not available, a generic mean value for the class [ 3 ] of material may be used if there are sufficient test results to establish a mean and a standard deviation for the class. ( ii ) For generic values of weld metal, the following generic mean values must be used unless justification for different values is provided: 0 °F for welds made with Linde 80 flux, and −56 °F for welds made with Linde 0091, 1092 and 124 and ARCOS B-5 weld