By Jack Grobe, Deputy Director for Engineering, NRC’s Office of Nuclear Reactor Regulation
The Nuclear Regulatory Commission (NRC) responded to the events at Fukushima by sending NRC staff to Japan, monitoring the event in our Operations Center at the agency headquarters in Maryland, sharing evolving information regarding the event with the U.S. nuclear industry and public and focusing our inspections on the plant design and plant procedures that will help ensure U.S. nuclear plants safely ride out a similar event if it occurs in the United States.
A few days after the earthquake and tsunami knocked out all electrical power to the Fukushima Dai-ichi plant, the NRC reminded every U.S. reactor owner of post-9/11 requirements for resources and procedures to ensure the reactors could maintain or restore core cooling, containment integrity and spent fuel pool cooling. The procedures are called Extensive Damage Mitigation Guidelines (EDMGs). The NRC then instructed its resident inspectors at every reactor site to verify those resources and procedures were in place. This first round of inspections also examined the plants’ resources and procedures for dealing with a station blackout (complete loss of AC electrical power), as well as severe flooding events.
I was honored to serve on the NRC task force of senior managers and staff that examined the near-term lessons learned from Fukushima, and we began our work shortly after those inspections began. The task force members looked closely at the results, which showed the plants have enough strategies in place to safely handle the loss of large areas of an individual plant. At about a third of the plants, however, the inspections showed that specific pieces of post-9/11 or station blackout equipment could be vulnerable to earthquakes, flooding or severe weather. This information played an important role in the task force recommending that plants provide better protection for those sorts of resources. The task force also recommended that plants have enough resources available to support every reactor at a given site, given that a severe event could affect more than one reactor at once.
The first round of inspection results also prompted the NRC to formally require all U.S. nuclear power plants to reconfirm their compliance with the post-9/11 requirements. The NRC’s request refocused the plants’ attention on not only having resources on hand, but ensuring the strategies can be carried out with current plant staffing. The plants also had to provide additional information on how the resources are maintained, tested and controlled; how strategies are re-evaluated if plant conditions or configurations change; and how arrangements are reached and maintained with local emergency response organizations.
The task force paid close attention to the role emergency procedures played at Fukushima. We realized we needed and up-to-date look at how U.S. plants plan for the most severe emergencies, so the task force requested another NRC staff inspection at each U.S. plant. The NRC’s resident inspectors examined the Severe Accident Management Guidelines (SAMGs) at each plant, a voluntary set of staff instructions meant to cover accident scenarios that go beyond a plant’s emergency operating procedures (EOPs). SAMGs are designed to contain or reduce the impact of accidents that damage a reactor core. The resident inspectors looked at where the plants keep the SAMGs, how the guidelines are updated and how the plants train their personnel to carry out the guidelines.
As with the previous inspection, the results on SAMGs were mixed. The inspectors found that all plants have implemented the guidelines, with 97 percent of the plants having the SAMG documents available in their Technical Support Center, generally considered the best location for plant employees to properly implement the guidelines. The inspectors found SAMGs in 89 percent of plant control rooms, and in 71 percent of plant Emergency Operations Facilities. However, only 42 percent of the plants periodically reviewed and updated their SAMGs. This lack of regular review could impact the effectiveness of the guidelines as plant upgrades and modifications are made. The inspectors found that staff at 92 percent of the plants received initial training on SAMGs. Only 61 percent of the plants, however, include use of the SAMGs in their periodic emergency drills.
The task force concluded the SAMGs and EDMGs provide important complements to plant EOPs. Each of these programs, however, is treated differently in the NRC’s regulations, inspection program, and licensing process, as well as in licensee programs and organizations. The task force therefore recommended integrating these accident support functions logically and coherently, along with NRC applying comprehensive regulatory oversight for maintaining the procedures and training the staff. This approach would enhance the readiness of plant personnel to take effective actions during an accident.
The task force concluded existing U.S. plants can continue to protect the public going forward, but offered 12 overarching recommendations to improve that protection. The agency’s senior management has proposed to the agency’s five Commissioners an approach to implementing the task force’s recommendations. The proposed approach balances the potential level of safety enhancement from each recommendation against other existing safety work and considers the availability of NRC staff critical skills and resources.
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