Up & Atom

A divided Commission at the US Nuclear Regulatory Commission (NRC) on January 24 approved the Mitigation of Beyond-Design-Basis Events rulemaking (Final Rule). The NRC began the rulemaking in December 2016 as part of its efforts to evaluate and implement, if necessary, regulatory changes in response to the Fukushima Daichi event in March 2011. In somewhat of a surprise, the majority of Commissioners last week rejected large portions of the proposed rule submitted by the NRC staff over two years ago. The rationale for changing the Final Rule demonstrates a renewed emphasis on applying backfit analyses.

As readers know well, after the Fukushima Daichi event, the NRC began a comprehensive review of the preparedness of nuclear reactors in the United States to respond to beyond-design-basis events. The NRC took three main actions that are relevant to the Final Rule:

  • The NRC issued two orders, Orders EA-12-049 and EA-12-051, modifying each reactor license to require licensees to implement emergency response strategies for beyond-design-basis events and to install spent fuel pool water level instrumentation, respectively;
  • The NRC staff sent letters to each reactor licensee pursuant to 10 CFR § 50.54(f), requiring licensees to reevaluate site-specific seismic and flooding hazards using updated hazard information; and
  • The Commissioners directed the NRC staff to conduct a Mitigation of Beyond-Design-Basis Events rulemaking, as proposed by COMSECY-14-0037.

In COMSECY-14-0037, the staff had proposed requiring licensees to take four actions: (1) consider the effects of reevaluated flooding and seismic hazards in its beyond-design-basis events response strategies; (2) create an overarching integrated response capability for beyond-design-basis events, including emergency operating procedures that included staffing and organization changes; (3) implement training and qualification requirements; and (4) conduct initial and subsequent drills or exercises on the mitigation strategies. In the Staff Requirements Memorandum in response to COMSECY-14-0037, the Commission agreed that the rulemaking should proceed, and directed the NRC staff to evaluate potential changes to relevant NRC guidance documents.

Now, in the Final Rule that the staff submitted to the Commissioners, the staff proposed a new section to Title 10 of the Code of Federal Regulations, § 50.155, Mitigation of Beyond-Design-Basis Events. This section makes Orders EA-12-049 and EA-12-051 generally applicable to all current licensees as well as future applicants and licensees to mitigate beyond-design-basis events. But a three-member majority of the Commission—over two dissenting votes by Commissioners Stephen Burns and Jeff Baran—rejected large portions of the NRC staff’s proposed rule for failure to appropriately consider the backfit requirements of 10 CFR § 50.109. Specifically, the Final Rule rejects the proposed regulatory requirements regarding the hazards reanalysis, integration of beyond-design-basis events response capabilities into the emergency operations procedures, specified training, and drill requirements. The Staff Requirements Memorandum (SRM) “found no basis to conclude that codifying these items in the final rule would constitute a substantial increase in the overall protection of the public health and safety or the common defense and security,” as required to implement a backfit pursuant to 10 CFR § 50.109(a)(3).

Instead, the SRM emphasized that the 10 CFR § 50.54(f) process “remains in place to ensure that the agency and its licensees will take the needed actions, if any, to ensure that each plant is able to withstand the effects of the reevaluated flooding and seismic hazards.” In relying on 10 CFR § 50.54(f) and NRC guidance, the revised Backfit Analysis approved by the Commission, emphasized that it was intentionally applying a “performance-based requirement” to meet beyond-design-basis events, consistent with the approach in Orders EA-12-049 and EA-12-051 to allow flexible mitigation strategies.

The Commission’s action is another in a string of actions focused on ensuring backfits are applied appropriately. The proposed rule was issued just before the NRC’s Office of General Counsel (OGC) recommended revisiting guidance restricting applicability of the “compliance exception” to the backfit rule. The NRC staff did not have the benefit of OGC’s recommendations when it published the proposed rule, nor the additional NRC training that followed thereafter. That the majority of Commissioners rejected large portions of the proposed rule on backfit grounds suggests that they are continuing to emphasize the need for a rigorous backfit analysis in any rulemaking or order.