What does it take to convince a nation scarred by disaster to trust nuclear power again? In Niigata Prefecture, that question has dominated debate for years, culminating this week in the decision to restart the Kashiwazaki-Kariwa nuclear power plant the largest in the world, with a total capacity of 8.2 GW after 15 years of dormancy following the Fukushima Daiichi meltdown.
The restart, which was voted through by the Niigata Prefectural Assembly, involves Tokyo Electric Power Company’s No.6 reactor and is expected to start operating by around January 20. Prior to the Fukushima accident, nuclear power contributed around 30% of Japan’s overall power supply. Currently, fuels like coal and liquefied natural gas contribute approximately 60-70% of power supply and average an amount of 10.7 trillion yen ($68 billion) per annum. Revival of nuclear power is one of the key pillars of new energy policy outlined by Japan’s new Prime Minister Sanae Takaichi. By 2040, she aims for an increased share of approximately 20%.
Kashiwazaki-Kariwa is as much about safety innovation as energy economics for engineers and policymakers. TEPCO’s post-Fukushima improvement work responds to risks brought to light by the 2011 earthquake and tsunami at Fukushima Daiichi, which knocked over seawalls and flooded important systems. At Kashiwazaki-Kariwa, seawalls and water-tight doors have been constructed to guard against extreme tsunamis, incorporating experiences from actual events such as the 869 Jogan tsunami event. These seawalls are modeled using high hydrodynamic simulation to predict maximum wave-runup heights to guard against reactor buildings and cooling systems.
Resilience for emergency power situations has also been revolutionized. Mobile diesel generators and extra fire trucks are strategically staged for quick mobilization to provide cooling water supplies even when power is out. This is modeled on the FLEX initiative of the nuclear power sector in the United States, where there is a focus on portable equipment strategically stationed to address beyond-design basis events. TEPCO’s mobile equipment is housed in elevated storages that can withstand flood damage, and drills on procedure have been extended to include mobilized equipment in emergency responses.
Another very important enhancement of this plant is the filtration systems, which are designed to deal with the distribution of radioactive material in case of a breach of containment. These highly efficient filtration systems are equipped with multi-stage particulate and iodine retention, which provides redundancy for operation under seismic loadings. These systems are a move towards separating safety and security systems, where intrusion detection and communication are not disabled in the event of a breach of reactor protection systems.
However, public sentiment remains sceptical. In fact, Niigata has found that 60% of inhabitants feel that the restart requirements are not being met, and TEPCO’s handling of the power plant remains suspect in the community, with nearly 70% lack of confidence. Its residents still remember Fukushima’s chain of meltdowns, including loss of off-site power, flooding of diesel generators, and delayed evacuations. Protesters, including evacuees of the stricken area, picketed the assembly to assemble.
The restart also relates to the forthcoming surge in electricity demand due to the use of AI data centers in Japan. According to the International Energy Agency, data centers are projected to account for over half of Japan’s electricity demand by the year 2030, thereby putting the power system close to maximum capacity. The potential of Japan’s nuclear power plants, including Kashiwazaki Kariwa, which has the capacity to produce 1.36 GW per reactor, lies in providing baseload electricity to compensate for the intermittency of the supply due to renewable resources and the lack of dependency on carbon resources.
From an engineering design perspective, the coastline position of Kashiwazaki-Kariwa requires a high level of tsunami protection. The station’s seawalls are designed above the maximum expected heights, taking into account the possible subsidence resulting from earthquakes, which reduces the land elevation. Water-tight doors are used for restricting access, and critical equipment such as pumps and generators are placed above the highest known flooding positions. The design is based on the implications of the subsidence and the underestimated height of the tsunami, as identified for several nuclear power stations from the Great East Japan Earthquake.
Its restart is also a proof-of-concept for the new regulatory system for nuclear in Japan, requiring multiple levels of safety redundancy, backup power for security systems, and detailed plans for evacuating the area. TEPCO plans on investing 100 billion yen in the area over the next decade, part of its plans to restore public confidence through economic and transparent communication on safety. For energy policymakers in Japan, Kashiwazaki-Kariwa is both a milestone and a test bed, says Christoph Frei, secretary general of the World Energy Council. The plant will be scrutinized not only for its role in helping to minimize the country’s dependence on fossil fuels, but also for the role that its safety engineering will play in the region, which is always at risk to both seismic activity and tsunamis.
