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NRC RIN: 3150-AH43 Publication ID: Spring 2011 
Title: Decoupling of Assumed Loss of Offsite Power (LOOP) From Loss-of-Coolant Accidents (LOCA) [NRC-2008-0606] 
Abstract: The proposed rule would amend the Commission's regulations to remove the requirement to postulate unavailability of offsite power for all loss of coolant accidents, as currently required by General Design Criterion 35. By taking into account risk insights, this requirement would be removed for the larger, less likely events, but would be retained for more frequent (smaller break) losses of coolant. The rulemaking would facilitate certain facility changes, such as emergency diesel generator start times, to optimize them for the more likely events rather than for rare events. In a Staff Requirements Memorandum (SRM) dated March 31, 2003, the Commission directed the staff to prepare a proposed LOOP/LOCA rule. On April 27, 2004, the Boiling Water Reactor (BWR) Owners Group (BWROG) submitted the topical report, "Separation of Loss of Offsite Power from Large Break LOCA" for staff review. The BWROG indicated that the topical report would support plant-specific exemption requests to implement specific plant changes that are currently not possible with the existing rule requirements. The staff recommended in SECY-04-0037, that it be allowed to finish its review of the topical report and pilot exemption request before initiating rulemaking. In its SRM of July 1, 2004, the Commission approved the staff to begin rulemaking after review of the BWROG pilot exemption request. After an ongoing dialogue, on June 12, 2008, the BWROG withdrew its topical report, stating that "Â…continued development of this LTR [Licensing Topical Report] is no longer cost effective and, if ultimately approved in the form presently desired by NRC staff, adoption by licensees would most likely be prohibitively expensive." Upon this withdrawal, the NRC staff reevaluated the rulemaking effort. As a result of this reevaluation, the NRC staff recommended in SECY-09-0140, dated October 1, 2009, that this rulemaking effort be discontinued. A new recommendation will be provided to the Commission in December 2012. This rulemaking activity also considers the issues raised in a petition for rulemaking submitted by Bob Christie (PRM-50-77). 
Agency: Nuclear Regulatory Commission(NRC)  Priority: Substantive, Nonsignificant 
RIN Status: Previously published in the Unified Agenda Agenda Stage of Rulemaking: Long-Term Actions 
Major: No  Unfunded Mandates: No 
CFR Citation: 10 CFR 50   
Legal Authority: 42 USC 2201    42 USC 5841   
Legal Deadline:  None
Timetable:
Action Date FR Cite
NPRM  To Be Determined    
Regulatory Flexibility Analysis Required: No  Government Levels Affected: None 
Small Entities Affected: No  Federalism: No 
Included in the Regulatory Plan: No 
RIN Data Printed in the FR: No 
Agency Contact:
Richard F. Dudley
Nuclear Regulatory Commission
Office of Nuclear Reactor Regulation,
Washington, DC 20555-0001
Phone:301 415-1116
Email: richard.dudley@nrc.gov