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:
eld deposit made using the same weld wire heat number as the critical vessel weld. If these values are not available, the upper limiting values given in the material specifications to which the vessel material was fabricated may be used. If not available, conservative estimates (mean plus one standard deviation) based on generic data [ 4 ] may be used if justification is provided. If none of these alternatives are available, 0.35% copper and 1.0% nickel must be assumed. ( B ) f is the best estimate neutron fluence, in units of 10 19 n/cm 2 (E greater than 1 MeV), at the clad-base-metal interface on the inside surface of the vessel at the location where the material in question receives the highest fluence for the period of service in question. As specified in this paragraph, the EOL fluence for the vessel beltline material is used in calculating KRT PTS . ( v ) Equation 4 must be used for determining RT PTS using equation 3 with EOL fluence values for determining ΔRT PTS . Equation 4: RT PTS = RT NDT(U) + M + ΔRT PTS ( 2 ) To verify that RT NDT for each vessel beltline material is a bounding value for the specific reactor vessel, licensees shall consider plant-specific information that could affect the level of embrittlement. This information includes but is not limited to the reactor vessel operating temperature and any related surveillance program [ 5 ] results. ( i ) Results from the plant-specific surveillance program must be integrated into the RT NDT estimate if the plant-specific surveillance data has been deemed credible as judged by the following criteria: ( A ) The materials in the surveillance capsules must be those which are the controlling materials with regard to radiation embrittlement. ( B ) Scatter in the plots of Charpy energy versus temperature for 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