April 2, 2015 

The Honorable James Inhofe 

Chairman, Committee on Environment 

 and Public Works 

United States Senate 

Washington, DC 20510 

Dear Mr. Chairman: 

 On behalf of the U.S. Nuclear Regulatory Commission (NRC), I am responding to your 

letter of March 4, 2015, in which you and seven of your Committee colleagues urge the agency 

to integrate the remaining post-Fukushima issues into the agency’s ongoing work. 

The agency continues to seek a balance between implementing lessons learned from 

Fukushima and the need to ensure that those efforts do not displace ongoing work of greater 

safety benefit, work that is necessary to maintain safety, or other higher-priority work. The 

majority of lessons learned activities have been transitioned back to the NRC’s line 

organizations, and only four issues remain under the direct control of the Japan Lessons 

Learned Division. Additional information on this topic is included in our enclosed responses to 

your specific information requests. 

Your letter also offered an endorsement of the NRC staff’s recommendations in 

COMSECY-14-0037, “Integration of Mitigating Strategies for Beyond-Design-Basis External 

Events and the Re-Evaluation of Flooding Hazards.” We appreciate receiving your views on 

this matter. 

The Commission recently completed its evaluation of the staff’s proposal in COMSECY14-0037, and the Commission approved the first two staff recommendations.1

 However, the 

Commission did not endorse staff recommendation 3, i.e., that the NRC staff should revise the 

Near-Term Task Force Recommendation 2.1 flooding assessments and integrate the Phase 2 

decision-making into the development and implementation of mitigating strategies in 

accordance with Order EA-12-0492

 and the related mitigation of beyond-design-basis events 

rulemaking. The Commission believes that the existing direction to address Recommendation 

2.1 continues to represent the best approach on this issue. 

 

1

 1) Licensees for operating nuclear power plants need to address the reevaluated flooding hazards within 

their mitigating strategies for beyond-design-basis external events, and 2) licensees for operating nuclear 

power plants may need to address some specific flooding scenarios that could significantly damage the 

power plant by developing targeted or scenario-specific mitigating strategies, possibly including 

unconventional measures, to prevent fuel damage in reactor cores or spent fuel pools. 2

 Order EA-12-049 directed power reactor licensees to develop, implement, and maintain guidance and 

strategies (“mitigating strategies”) to maintain or restore core cooling, containment, and spent fuel pool 

cooling capabilities following a beyond-design-basis external event. 
- 2 - 

At the same time, we recognize that additional insights gained since those initial safety 

enhancements were approved in 2012 indicate that some modification of our original direction is 

prudent. Therefore, instead of the path outlined in recommendation 3, the Commission directed 

the staff to reassess the guidance developed for the Phase 1 integrated (total plant) 

assessments to be performed at those plants with a reevaluated flood hazard that exceeds the 

current design basis. The guidance should: 

• Include a graded approach for determining the need for, and prioritization and scope 

of, plant-specific integrated assessments so that those assessments focus on plants 

where there is the greatest opportunity for additional safety enhancements; 

• Use resources judiciously, and be risk-informed and performance-based, to the 

extent practicable, to reduce any unnecessary conservatisms and identify any areas 

with insufficient conservatisms; 

• Evaluate potential changes to the guidance to introduce more realism for the 

purpose of identifying potential safety enhancements for operating reactors; 

• Focus on flood scenarios that could result in cliff-edge effects and where substantial 

safety benefits can be achieved, rather than on scenarios where limited risk 

improvements are expected; and 

• Consider available physical margin data in order to assess the flooding vulnerability 

for each site. 

 The Commission also directed the staff to develop the acceptance criteria and guidance 

for Phase 2 of the flooding reevaluations to: 

• Add clarity on how Phase 2 decisions about whether further regulatory actions are 

necessary will be made within the current regulatory process, including the Backfit 

Rule; 

• Allow flexibility in the way in which licensees address vulnerabilities identified 

through the integrated assessment process that relied on hazards developed using 

guidance for new plants; 

• Take into account the fact that the licensees are protecting mitigating strategies 

equipment from the reevaluated flood hazard developed in accordance with the 

10 CFR 50.54(f) letter and the associated guidance; and 

• Consider an appropriate balance between protection and mitigation based on the 

principle of defense-in-depth. 

The Commission directed the staff to (1) work with licensees to expeditiously complete 

the flooding hazard reevaluations in order to ensure that flooding hazards are understood for 

every site, and (2) define the steps needed to complete agency actions in response to 

Recommendation 2.1 for flooding. Fifty-four of the 63 sites have submitted their flooding hazard 

reevaluations. Licensees for six of the remaining nine sites requested assistance with analysis 

related to upstream dam failures from the U.S. Army Corps of Engineers, through the NRC. 
- 3 - 

Licensees for the remaining three sites requested extensions of their submittal date to develop 

site-specific models or studies or to refine analysis for certain flood hazard scenarios. 

Thank you for your interest in this important matter. I hope this letter and enclosure are 

responsive to your inquiry. If you need any additional information, please contact me or 

Mr. Eugene Dacus, Director of the Office of Congressional Affairs, at (301) 415-1776. 

 Sincerely, 

 /RA/ 

 Stephen G. Burns 

Enclosure: 

As stated 

cc: Senator Barbara Boxer 
Identical letter sent to: 

The Honorable James Inhofe 

Chairman, Committee on Environment 

 and Public Works 

United States Senate 

Washington, DC 20510 

cc: Senator Barbara Boxer 

The Honorable David Vitter 

United States Senate 

Washington, DC 20510 

The Honorable John Barrasso 

United States Senate 

Washington, DC 20510 

The Honorable Shelley Moore Capito 

United States Senate 

Washington, DC 20510 

The Honorable Mike Crapo 

United States Senate 

Washington, DC 20510 

The Honorable John Boozman 

United States Senate 

Washington, DC 20510 

The Honorable Jeff Sessions 

United States Senate 

Washington, DC 20510 

The Honorable Mike Rounds 

United States Senate 

Washington, DC 20510