SAKIGAKE管理人 Introduction
At 10:13 AM on July 16, 2007, a magnitude 6.8 earthquake struck off the coast of Niigata Prefecture’s Kamigoshi region. According to the finalized report by the Fire and Disaster Management Agency, the earthquake caused 15 deaths, 2,346 injuries, 1,331 completely destroyed homes, 5,710 partially destroyed homes, and 37,633 homes with partial damage.
One reason this earthquake drew international attention was its impact on Tokyo Electric Power Company’s Kashiwazaki-Kariwa Nuclear Power Station, located near the epicenter. With seven reactors, this plant holds one of the world’s largest total generating capacities as a single facility, and it experienced ground motion far exceeding what had been assumed at the design stage.
The reactors operating at the time of the earthquake shut down automatically and subsequently transitioned safely into cold shutdown. At the same time, however, a fire broke out in the on-site transformer at Unit 3, water containing radioactive material leaked, and damage occurred to non-safety-related equipment and surrounding facilities — numerous issues were confirmed, and the plant entered a prolonged period of inspection and shutdown.
What the Chuetsu-oki earthquake demonstrated is the reality that “meeting a standard” and “being able to withstand an event that exceeds assumptions” are not necessarily the same thing. This article looks back at the impact this earthquake had on the seismic safety of nuclear facilities, and considers what implications it holds for corporate disaster prevention planning and BCP (Business Continuity Planning).
When “Shaking Beyond Assumptions” Struck the Facility Directly
Each unit of the Kashiwazaki-Kariwa Nuclear Power Station had been designed and licensed based on the seismic design standards under the laws and regulations applicable at the time of construction. However, the ground motion actually observed on July 16, 2007, far exceeded what had been assumed at the design stage.
For example, the foundation slab of the Unit 1 reactor building recorded a maximum acceleration of 680 Gal in the east-west direction — approximately 2.5 times the maximum design response acceleration of 273 Gal. The reactors operating at the time of the earthquake detected the tremor and shut down automatically. No serious loss of function was confirmed in safety-critical equipment, and the reactors transitioned into cold shutdown.
Meanwhile, multiple issues occurred simultaneously within the plant. A fire broke out in the on-site transformer at Unit 3, and leakage of water containing radioactive material, as well as the release of trace amounts of radioactive substances, were confirmed. Damage and deformation also occurred to non-safety-related equipment, piping, facilities surrounding the buildings, and the ground itself. While no significant radiological impact on surrounding residents or the environment was confirmed, this event was extremely significant in that it made visible the effects that ground motion exceeding assumptions can have on an entire facility. All seven units entered a prolonged period of inspection and shutdown; Unit 7, the first to resume commercial operation, did so in December 2009 — approximately two years and five months after the earthquake.
“Meeting a Standard” and “Being Safe” Are Separate Issues
The central question the Chuetsu-oki earthquake posed to society was this: “Is meeting laws and regulatory standards, by itself, sufficient to be considered truly safe?”
At the time, the Kashiwazaki-Kariwa Nuclear Power Station complied with the seismic design standards required under the laws and regulations then in effect. However, natural phenomena do not necessarily occur within the range of standards set by humans. What matters is that meeting a design standard is not the endpoint of safety measures, but the starting point. Compliance with a standard secures a certain level of safety, but what is required is preparedness that also looks ahead to events that exceed that standard, and to the “residual risk” that remains even after countermeasures have been taken.
This lesson is not limited to nuclear facilities. Legal compliance is essential. However, complying with the law and having the safety level truly necessary for your own business continuity are not necessarily the same thing.
The Review of Seismic Safety That Followed the Chuetsu-oki Earthquake
In 2006, the year before the Chuetsu-oki earthquake, the seismic design review guidelines for nuclear facilities had already been revised. Following the earthquake, seismic back-checks, reassessments of ground motion, and reviews and strengthening of geological and ground surveys were carried out. Furthermore, following the 2011 Great East Japan Earthquake and the Fukushima Daiichi Nuclear Power Station accident, new regulatory standards were enforced in 2013.
Within this progression, what came to be emphasized was “recognizing events and residual risks that exceed design standards, and implementing multi-layered preparedness.”
Implications for Corporate Disaster Prevention and BCP — Building an Organization That Can Recover Even Beyond Assumptions
The lessons of the Chuetsu-oki earthquake offer an essential perspective for reviewing the risk assessment of your own critical facilities and equipment.
First, do not treat “meeting legal standards” as equivalent to zero risk. Meeting seismic, building, and fire safety standards secures a minimum level of safety, but the assumptions underlying those standards are not guaranteed to remain valid in the future.
Second, identify the single points of failure in your critical facilities and equipment. Just as the shutdown of the Kashiwazaki-Kariwa plant had a major impact on power supply, it is essential to understand “what impact the shutdown of a single piece of equipment would have on the business as a whole,” and to assess risk across the supply chain, not just within your own company.
Third, develop a BCP premised on compound, simultaneous troubles. At the Chuetsu-oki earthquake, multiple events — a fire, equipment damage, and the leakage of water containing radioactive material — occurred simultaneously. Companies, too, need drills and response plans that assume not just a single disaster, but a situation in which multiple failures overlap.
The purpose of a BCP is not to eliminate the “unexpected.” It is to build an organization that can restore operations swiftly and continue fulfilling its social responsibilities even when events exceeding assumptions occur. The Chuetsu-oki earthquake can be described as a case that demonstrated, in corporate disaster prevention, the importance of building not only the ability to “prevent damage,” but the resilience to recover even after sustaining damage.
An Option for Enhancing Seismic Performance
Enhancing the resilience of buildings and infrastructure is not limited to developing a BCP. Improving the seismic performance and durability of existing buildings is also an important measure for strengthening business continuity capability. SAKIGAKE JAPAN handles “Aster Power Coating,” a coating that contributes to improving the durability and seismic resistance of concrete and mortar simply by being applied. It is used to extend the service life of bridges, public infrastructure, and buildings, and is also drawing attention as a measure to prepare for disaster risk.
▶ For more information about Aster Power Coating:
https://sakigakejp.com/en/sales/aster-power-coating-2/
Conclusion
The Chuetsu-oki earthquake demonstrated, through one of the world’s largest nuclear power stations, the reality that “meeting a standard” and “being able to respond to events that exceed assumptions” are not the same thing.
What companies are truly being asked is:
- Are the assumptions underlying our standards still valid today?
- If critical equipment goes down, do we have alternative means?
- Can we still make decisions even if multiple failures occur simultaneously?
- How quickly can we recover once an event exceeds our assumptions?
The sense of reassurance that “our facilities meet the standards, so we’re fine” must never become a reason to stop assessing risk. Through corporate disaster prevention consulting, disaster risk management, and BCP development support, SAKIGAKE JAPAN supports the construction of effective disaster prevention and crisis management systems that go beyond mere legal compliance.
Contact Us
For inquiries regarding corporate disaster prevention consulting, BCP development support, or disaster prevention products and solutions, please feel free to contact us.
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References and Sources
- Japan Meteorological Agency, “The 2007 Niigata Prefecture Chuetsu-oki Earthquake”
- Fire and Disaster Management Agency, “Damage Status from the 2007 Niigata Prefecture Chuetsu-oki Earthquake (Final Report)”
- Tokyo Electric Power Company Holdings, “Kashiwazaki-Kariwa Nuclear Power Station: Information Related to the Niigata Prefecture Chuetsu-oki Earthquake”
- Nuclear Regulation Authority, “Seismic and Safety Assessment Materials Related to the Kashiwazaki-Kariwa Nuclear Power Station”
- Headquarters for Earthquake Research Promotion, “Assessment of the Niigata Prefecture Chuetsu-oki Earthquake”
- Organization for Small & Medium Enterprises and Regional Innovation, “BCP Formulation and Operation Guidelines for Small and Medium Enterprises” (referenced for BCP-related content)