Qualla: Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit ENERGY.GOV, Public domain. The fault line known as D-1 runs directly beneath Reactor No. 2 at the Tsuruga Nuclear Power Plant. In December 2012, a team of experts led by NRA Commissioner Kunihiko Shimazaki examined the crushed rock zones under the facility and concluded that D-1 could move in conjunction with the Urasoko fault, an active seismic feature located just 250 meters from the reactor buildings. Japan Atomic Power Company, the plant's operator, spent the next twelve years trying to prove otherwise -- presenting counter-analyses, requesting additional hearings, and at one point altering seismic data in its presentations. On 28 August 2024, the Nuclear Regulation Authority issued its final ruling: Reactor No. 2 cannot be switched back on. The plant sits in the city of Tsuruga, Fukui Prefecture, on a site it shares with the decommissioned prototype Fugen Nuclear Power Plant. Ninety-four percent of the site is green space. Beneath that green surface, the earth is fractured.

Image: ENERGY.GOV | Public domain

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: First Light, First Cover-Up

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit IAEA, CC BY-SA 2.0. Tsuruga Unit 1 began commercial operation on 14 March 1970, a boiling water reactor producing 357 megawatts. It was among Japan's earliest commercial nuclear reactors. Eleven years later, in March 1981, drainage from Unit 1 caused a release of radioactivity. The incident itself w...

Image: IAEA | CC BY-SA 2.0

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: The Urasoko Fault Reveals Itself

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit ENERGY.GOV, Public domain. On 5 March 2012, seismic researchers delivered findings that shook the foundations of the entire Fukui nuclear corridor. The Urasoko fault, which runs beneath and near the Tsuruga site, had been estimated by the Earthquake Research Committee at roughly 25 kilometers long, capable...

Image: ENERGY.GOV | Public domain

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: D-1: A Fault with a Name

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Gtogk, CC0. In November 2012, the NRA dispatched an investigative team to examine the faults beneath the Tsuruga site. On 1 December, Commissioner Kunihiko Shimazaki and four other experts walked the site, examining geological layers at multiple points. Their conclusion, presented on 10 Dece...

Image: Gtogk | CC0

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: A Decade of Denial

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit SONIC BLOOMING, CC BY-SA 4.0. Japan Atomic Power Company fought the findings at every step. On 8 March 2013, the company presented its own geological analysis arguing that D-1 was not active. The NRA panel was unconvinced. On 19 April, the NRA inspection team told JAPC it would not accept the company's refuta...

Image: SONIC BLOOMING | CC BY-SA 4.0

Tsuruga Nuclear Power Plant: The Reactor Built on a Fault Line: The Final Ruling

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit ENERGY.GOV, Public domain. On 28 August 2024, the Nuclear Regulation Authority delivered the verdict that had been building for twelve years: Reactor No. 2 at Tsuruga cannot be restarted due to the risks posed by the active seismic fault beneath it. Unit 1, meanwhile, had already been marked for decommissi...

Image: ENERGY.GOV | Public domain