Document: NRC Regulatory Guide
Document ID: 0d99822b-1af0-41be-a088-75b961301b4f
Document Type: regulatory_guide
Title: Regulatory Guidance on the Alternate Pressurized Thermal Shock Rule + HISTORY - HISTORY 03/2015 – DG-1299 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1405/ML14056A011.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.230
CFR Part: 
CFR Title: 

Content:
events, are characterized by rapid cooling (i.e., thermal shock) of the internal RPV surface that may be combined with repressurization. The simultaneous occurrence of critical-size flaws, embrittled steel, and a severe PTS transient is a low probability event. The NRC established the requirements for fracture toughness in 10 CFR 50.61 and many operating plants were licensed to meet these requirements. However, after additional information became available, it was recognized that the initial requirements established in 10 CFR 50.61 were based on overly conservative assumptions. In the Federal Register dated January 4, 2010 (Ref. 4), the NRC amended its regulations to provide alternate fracture toughness requirements for protection against PTS events for PWR RPVs. The alternate requirements contained in 10 CFR 50.61a maintain adequate safety while reducing regulatory burden for a PWR licensee who expects to exceed the requirements contained in 10 CFR 50.61 before the expiration of its license. A PWR licensee may choose to apply the provisions of 10 CFR 50.61a as a voluntary alternative to complying with the requirements of 10 CFR 50.61. DG-1299, Page 3 The “Alternate PTS Rule” contained in 10 CFR 50.61a is revised PTS screening criteria in the form of an embrittlement reference temperature, RTMAX-X, which characterizes the RPV material’s resistance to fracture initiating from flaws based on more comprehensive analysis methods. This document contains four regulatory positions that provide guidance concerning methods that the NRC staff considers acceptable for meeting the various criteria within the Alternate PTS Rule. These four regulatory positions are described below: 1. Criteria relating to the date of construction and design requirements: The Alternate PTS Rule is applicable to PWR licensees whose construction permits were issued before February 3, 2010, and whose RPVs were designed and fabricated in accordance with Section III of the ASME Code, 1998