Document: NRC Regulatory Guide
Document ID: 921f4c90-482e-4f9e-a835-28839c357dcb
Document Type: regulatory_guide
Title: Flexible Mitigation Strategies for Beyond-Design-Basis Events + HISTORY - HISTORY 11/2015 – DG-1301 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1316/ML13168A031.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.226
CFR Part: 
CFR Title: 

Content:
06, Rev. 1A provide an acceptable method for licensees to follow to develop a baseline coping capability for mitigating an ELAP concurrent with either an LUHS or, for nuclear power plants with passive reactor designs, a loss of normal access to the normal heat sink with the following clarifications: a) It should be noted that the initial and boundary conditions described do not accurately reflect a loss of all ac power condition due to the limitation of initial conditions (1) and (2) of NEI 12-06, Rev. 1A, Section 3.2.1.3. The additional contingencies described in section 1.2 of this document are necessary for compliance with the requirement to mitigate a loss of all ac power. b) An element of a set of strategies to maintain or restore core and SFP cooling and containment functions includes knowledge of the time a licensee or applicant can withstand challenges to these key safety functions using installed equipment during a BDBEE. This knowledge provides an input to the choice of storage locations and conditions of readiness of the equipment required for the follow-on phase. This duration is related to, but distinct from the specified duration for the requirements of 10 CFR 50.63, “Loss of All Alternating Current Power,” paragraph (a), because it represents the current capabilities of the licensee or applicant rather than a required capability and licensees and applicants should 1) account for the SFP cooling function, which is not addressed by 10 CFR 50.63(a), and 2) assume the non-availability of alternate ac sources, which may be included in meeting the specified durations of 10 CFR 50.63(a). This is implicit in the NEI 12-06, Rev. 1A principles described in Section 3.2.1.7, Paragraph (6) and Section 3.2.2, Paragraph (1). However, maintenance of the guidance and strategies requires that the estimate of capability be kept current to reflect plant conditions following facility changes such as modifications or equipment outages. Changes in the facility can