March 11 marks the two-year anniversary of the largest natural disaster that Japan has ever experienced. The earthquake and tsunami tidal waves caused considerable damage to the Japanese coast, most notably damaging the Fukushima Daiichi Nuclear Power Plant.
“Following the events at Fukushima Daiichi, the U.S. nuclear energy facilities immediately began taking steps to make them even safer,” explained Scott Northard, who serves as the director of the Utilities Service Alliance (USA) Fukushima Response team. “Key actions included the procurement of additional safety equipment, review and walkthrough of our severe accident management procedures, and improved training of plant personnel to respond safely to extreme natural events.”
Teams at the USA plants continue to make progress in implementing improved safety measures in response to the events. The actions include industry initiated programs, as well as, responding to formal Nuclear Regulatory Commission (NRC) orders and information requests. These responses have been focused on the stations’ ability to cope with beyond design basis events with similar consequences as those which occurred in Japan.
“Improving our Emergency Response Organizations’ ability to respond to such an event and function effectively without normal equipment and power supplies is also a focus of USA,” added Northard.
Together, the USA fleet of ten nuclear stations with fourteen units collaborated on the development of integrated plans to address the three NRC orders issued last March which were submitted to the NRC February 28.
The first order required the development of mitigation strategies to respond to extreme natural events resulting in an extended loss of AC power. Through the Nuclear Energy Institute, the industry has developed a response strategy called “FLEX.” The FLEX approach adds equipment such as portable pumps, generators and other equipment located in diverse locations throughout the sites.
The strategy is flexible in that it does not mandate that permanent equipment be installed, but that portable equipment be protected and maintained for use in a catastrophic event to provide a continuous supply of electricity and water. Various critical plant systems will be set up with standardized connection points for the portable FLEX equipment to tie into. This strategy is much larger and more comprehensive in scale than the one developed following the September 11, 2001 terrorist attacks (often referred to as “B.5.b”).
Additional spent fuel pool level instrumentation will be installed at the sites in response to the second NRC order. While the spent fuel pools did not suffer damage that resulted in radiation releases in Japan, the lack of information on their condition was a distraction from more urgent tasks.
“An active USA team is reviewing and selecting new technology for instrumentation that will provide more detailed information on the condition of the pools and include features to ensure it will be available following severe events,” explained Northard.
In response to the third NRC order – which only applies to boiling water reactors– upgrades will be installed on existing containment vent systems used during specific accident scenarios. The vent system is needed under certain conditions to remove heat and protect containment from conditions that could result in its failure.
Last year, all plants performed walk-downs to verify that plant seismic and flood protection features were in place and would function as designed. Other ongoing activities include emergency preparedness staffing and communications assessments, reevaluations of design basis flooding and earthquake hazards and the development of new procedures to incorporate the new FLEX strategies into existing plans.
“Leveraging the benefits of working together as a fleet, these efforts provide an opportunity for the USA plants to share best practices and experiences and achieve benefits from economies of scale,” said Northard. “Examples include purchasing new spent fuel level instruments and satellite communication equipment as a group.”
Also, Regional Response Centers (RRCs) are being established to provide additional equipment, such as large diesel generators and diesel powered pumps to support longer term operation without offsite power available. All utilities will participate in sharing the cost of equipment stored at the RRCs, which can be delivered to any site in the U.S. within approximately 24 hours.
“Collectively, the nuclear industry’s response to the events in Japan have helped to enhance safety at all nuclear plants and by working closely together, the USA plants have been able to respond more effectively and at lower cost than acting independently,” explained Northard. “Over the next few years, as we implement the changes described above, we expect to continue to identify opportunities for collaboration and cost savings.”
Scott Northard, USA Director – Fukushima Response