March 11, 2011 was a sobering day for the world when a magnitude 9.0 earthquake off the coast of Japan triggered a massive tsunami that destroyed 430 miles of coastline and killed nearly 16,000 people.
The tsunami led to a total loss of power at the Fukushima Daiichi nuclear power plant and caused fuel melting in three of its reactors and a release of radioactive materials into the environment.
While no deaths were attributed to radiation exposure from these accidents, there are still many lessons to be learned from these events. Since the accidents, the U.S. government has been collaborating with Japan to further our understanding about the accident progressions that occurred in these three units.
One aspect of that partnership is analyzing data that came from the damaged reactors to see what we can learn and how to apply that knowledge to enhance nuclear safety.
Several Japanese organizations, including Tokyo Electric Power Company (TEPCO) Holdings, have worked closely with the U.S. to provide information and support this effort.
The Boiling Water Reactor Owners’ Group (BWROG), led by utility personnel and GE Hitachi Nuclear Energy, has also been a key contributor to this work through an international forensics program led by the U.S. Department of Energy (DOE). This effort includes experts from industry, national laboratories and universities, as well as the U.S. Nuclear Regulatory Commission.
BWROG recently highlighted three successes enabled by the forensics program that are already having a direct influence on the performance and safety of boiling water reactors (BWRs) in the U.S. thanks to new training programs, operational procedure upgrades and implementation of accident management guidance.
Severe Accident Interactive Learning
The BWROG recently developed an interactive computer-based training program for reactor operators, decision makers, and implementors of accident management guidance. The Severe Accident Interactive Learning (SAIL) program was enhanced by information obtained from the forensics working group and is currently hosted on the Institute of Nuclear Power Operations e-learning portal.
More than 3,000 individuals, including control room operators, emergency response center staff, and other cognizant personnel, have already been certified through SAIL. This resource frees plant owners and operators from having to develop and provide their own training. It has also led to significant cost savings by reducing training costs by more than $6 million per year over the BWR fleet.
Updated Operating Guidance
The forensics program information also contributed to revised guidance developed for operating BWR emergency cooling systems during extreme external events.
The new guidance is based on insights gained from evaluating Fukushima Daiichi’s Unit 2 and 3 Reactor Core Isolation Cooling (RCIC) system operation, along with tests that were conducted as part of the Terry Turbine Expanded Operating Band project. The work was a collaborative effort between the Light Water Reactor Sustainability Program (LWRS), BWROG, the Electric Power Research Institute, the Government of Japan, and Texas A&M University.
The new procedures provide operators increased RCIC operating flexibility, such as overriding certain trips or adjusting inlet flow, to ensure reactor cooling. This allows RCIC systems to now operate in conditions well beyond their initial design basis during some events, such as station blackouts.
The revised guidance was put to direct use during an August 2020 Derecho that significantly damaged a local power grid in Iowa.
While the Duane Arnold Energy Center lost offsite power as a result of this weather event, revised operating procedures were used to maintain natural circulation of water through the core as operators worked to safely shutdown the reactor.
The Fukushima forensic working group is led by DOE’s Office of International Nuclear Energy Policy and Cooperation, which collaborates with international partners to support the safe, secure, and peaceful use of nuclear energy.
Other outcomes include updates to severe accident code models, which are used to support new accident management strategies, plant risk assessments, and new reactor licensing applications.
Activity results are presented at international Japan-led projects, paving a path for U.S. industry to evaluate and provide input to post-Fukushima actions being taken by other countries.
Source: U.S. Office of Nuclear Energy