Tōkai Nuclear Power Plant

Updated on Dec 19, 2023

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Country Japan Units decommissioned 1 × 166 MW Construction began 1 March 1961		Units operational 1 × 1100 MW Phone +81 29-282-1211

Status Out of service for 6 years Commission date July 25, 1966 (1966-07-25) Operator(s) Japan Atomic Power Company Address 1-1 Shirakata, Tokai, Naka District, Ibaraki Prefecture 319-1198, Japan Similar Onagawa Nuclear Power Pl, Fukushima Daini Nuclear P, Tsuruga Nuclear Power Pl, Higashidōri Nuclear Power Pl, Shika Nuclear Power Pl

The Tōkai Nuclear Power Plant (東海原子力発電所, Tōkai genshi-ryoku hatsuden-sho, Tōkai NPP) was Japan's first commercial nuclear power plant. It was built in the early 1960s to the British Magnox design, and generated power from 1966 until it was decommissioned in 1998. A second nuclear plant, built at the site in the 1970s, was the first in Japan to produce over 1000 MW of electricity.

Due to the 2011 Tōhoku earthquake and tsunami the number 2 reactor shut down automatically. It has been suggested that the reactor should not be restarted and should be decommissioned.

LocationEdit

The site is located in Tokai in the Naka District in Ibaraki Prefecture, Japan and is operated by the Japan Atomic Power Company. The total site area amounts to 0.76 km² (188 acres) with 0.33 km², or 43% of it, being green area that the company is working to preserve.

Unit 1Edit

This reactor was built based on British developed Magnox technology. Unit 1 will be the first nuclear reactor to be decommissioned in Japan. The experience in decommissioning this plant is expected to be of use in the future when more Japanese plants are decommissioned. Below is a brief time-line of the process.

March 31, 1998: operations cease

March 2001: last of the nuclear fuel moved off-site

October 4, 2001: decommissioning plan announced

December 2001: decommissioning begins, spent fuel pool is cleaned

2003: turbine room and electric generator taken down

Late 2004: fuel moving crane dismantled

2011: the reactor itself is dismantled

Unit 2Edit

This Boiling Water Reactor was the first nuclear reactor built in Japan to produce over 1,000 MW of electricity. By some formalities in the paperwork, the unit is technically separate from the rest of the nuclear facilities at Tokai-mura, but it is managed with the rest of them and even shares the same front gate.

1997 & 1999Edit

Two nuclear incidents happened in 1997 & 1999:

On 11 March 1997, a small explosion in a Dōnen plant.
On 30 September 1999, a serious criticality accident in a JCO plant.

2011Edit

Following the 2011 Tōhoku earthquake and tsunami, the Number 2 reactor was one of eleven nuclear reactors nationwide to be shut down automatically. It was reported on 14 March that a cooling system pump for the Number 2 reactor had stopped working. Japan Atomic Power Company stated that there was a second operational pump and that cooling was working, but that two of three diesel generators used to power the cooling system were out of order.

In 2007, Ibaraki Prefecture took action to shield the facility from tsunamis with heights of 5.7 metres, and additions to the seawall were made to a 6.1 metre height two days before the 2011 Tōhoku earthquake and tsunami on 9 March 2011. A 5.4 metre tsunami arrived on 11 March at the plant. These facts were disclosed to the news media at the time of plant inspection by the Japanese Government on 13 February 2012.

During the earthquake of 11 March 2011, the Tokai power plant suffered external power-loss, just like what happened in Fukushima. Thanks to extra voluntary measures taken by Japan Atomic Power, the reactors could still be safely cooled, and an additional major accident was prevented. In 2002, an evaluation technology adopted by the Japan Society of Civil Engineers had determined that the site of the plant could experience tsunami waves as high as 4.86 metres. The government of Ibaraki prefecture published their own calculations in October 2007, where they estimated that such waves could be as high as 6 to 7 metres. Japan Atomic Power changed its wave level assumption to 5.7 meters. Reconstruction works to raise the height of the 4.9-metre protection around the plant to 6.1 meters were started in July 2009, in order to protect the seawater pumps intended to cool an emergency diesel generator. Although most of the work was completed by September 2010, cable holes in the levee were still not fully covered. This work was scheduled to be completed around May 2011. When the tsunami did hit the Tokai plant in March, the waves were 5.3 to 5.4 metres in height, higher than earlier estimations but still 30 to 40 centimetres lower than the most recent estimation. The Tokai plant suffered a loss of external power-supply just like the Fukushima plant. The levee was overrun in Tokai, as with Fukushima, but only one of three seawater pumps failed, and the reactors could be kept stable and safe in cold shutdown with the emergency diesel generator cooled by the two remaining seawater pumps.

After the disaster in Fukushima, a stress-test was ordered by the Japanese government, since an investigation of the electrical installations of the Tokai Daini reactor revealed that they did not meet the earthquake-resistance standards set by the government.

On 19 March 2012, it was discovered that during the decommissioning of a nuclear reactor, 1500 liters of low-radioactive water (33.000 becquerel/liter) was leaked away over three days from a storage-tank, when it was pumped into another tank. Further investigation should reveal whether the water leaked into the sea or not. The water was used for decontamination. Closer inspection proved that the leakage had been there for much longer, and that from October 2010 some 2200 liters extra had been lost. According to the owner of the plant, nothing leaked out of the building, and the water would be cleaned up.

Public opinionEdit

On 11 October 2011 Tatsuya Murakami, the mayor of the village Tokai, said in a meeting with minister Goshi Hosono, that the Tokai Daini reactor situated at 110 kilometer from Tokyo should be decommissioned, because the reactor was more than 30 years old, and the people had lost confidence in the nuclear safety commission of the government.

In 2011 and 2012, about 100,000 signatures against the resumption of the plant's operation, halted since last year, were submitted to Ibaraki Gov. Masaru Hashimoto. The petition urges the prefectural government not to allow the Tokai power station to resume operation, saying, "We should not allow a recurrence of the irretrievable sacrifice and loss as experienced in the Fukushima Daiichi nuclear power plant accident".

Stress-tests: extra checks needed, because active faults might move simultaneouslyEdit

Seismic research in 2011 did show, that the March 11th quake was caused by the simultaneous movement by multiple active faults at the coast of the Pacific Ocean in northern Japan, and on this way a much bigger earthquakes could be triggered, than the plants were planned to withstand, at the time they were built. In February the Tokai Daini Plant in Ibaraki Prefecture and the Tomari power facility in Hokkaido, said that it could not ruled out the possibility that the plant was vulnerable. Other nuclear power stations declared that the active faults near their nuclear plants would not move at the same time, and even when this would happen, the impact would be limited. NISA would look into the evaluation of active faults done by the plants.