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:
§ 50.61 Fracture toughness requirements for protection against pressurized thermal shock events. ( a ) Definitions. For the purposes of this section: ( 1 ) ASME Code means the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section III, Division I, “Rules for the Construction of Nuclear Power Plant Components,” edition and addenda and any limitations and modifications thereof as specified in § 50.55a . ( 2 ) Pressurized Thermal Shock Event means an event or transient in pressurized water reactors (PWRs) causing severe overcooling (thermal shock) concurrent with or followed by significant pressure in the reactor vessel. ( 3 ) Reactor Vessel Beltline means the region of the reactor vessel (shell material including welds, heat affected zones and plates or forgings) that directly surrounds the effective height of the active core and adjacent regions of the reactor vessel that are predicted to experience sufficient neutron radiation damage to be considered in the selection of the most limiting material with regard to radiation damage. ( 4 ) RT NDT means the reference temperature for a reactor vessel material, under any conditions. For the reactor vessel beltline materials, RT NDT must account for the effects of neutron radiation. ( 5 ) RT NDT(U) means the reference temperature for a reactor vessel material in the pre-service or unirradiated condition, evaluated according to the procedures in the ASME Code, Paragraph NB-2331 or other methods approved by the Director, Office of Nuclear Reactor Regulation. ( 6 ) EOL Fluence means the best-estimate neutron fluence projected for a specific vessel beltline material at the clad-base-metal interface on the inside surface of the vessel at the location where the material receives the highest fluence on the expiration date of the operating license. ( 7 ) RT PTS means the reference temperature, RT NDT , evaluated for the EOL Fluence for each of the vessel beltline materials, using the procedures of