Onagawa Nuclear Power Plant
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|Onagawa Nuclear Power Plant|
The Onagawa Nuclear Power Plant
|Construction began||July 8, 1980|
|Commission date||June 1, 1984|
|Operator(s)||Tohoku Electric Power Company|
|Reactors operational||1 x 524 MW
2 x 825 MW
|Annual generation||5,283 GW·h|
|Net generation||157,545 GW·h|
|As of July 25, 2007|
The Onagawa Nuclear Power Plant (女川原子力発電所 Onagawa ( pronunciation) genshiryoku hatsudensho , Onagawa NPP) is a nuclear power plant located on a 1,730,000 m2 (432 acres) site in Onagawa in the Oshika District and Ishinomaki city, Miyagi Prefecture, Japan. It is managed by the Tohoku Electric Power Company. It was the most quickly constructed nuclear power plant in the world.
The plant conforms fully to ISO 14001, a set of international environmental management standards. The plant's waste heat water leaves 7 degrees Celsius higher than it came in and is released 10 meters under the surface of the water, in order to reduce adverse effects on the environment All the reactors were constructed by Toshiba.
According to Reuters the Onagawa nuclear power plant was the closest nuclear power plant to the March 2011 earthquake epicenter. All three reactors at the power plant successfully withstood the 2011 Tōhoku earthquake and tsunami, demonstrating the ability of a well designed nuclear facility to withstand even one of most powerful of megathrust earthquakes and tsunamis ever recorded and to shut down safely, as designed, without incident.
Reactors on Site
|Unit||Type||Start of Operation||Electric Power|
|Onagawa - 1||BWR||June 1, 1984||524 MW|
|Onagawa - 2||BWR||July 28, 1995||825 MW|
|Onagawa - 3||BWR||January 30, 2002||825 MW|
Shut down manually on 25 February 2005 because it was determined that the reactor containment leaked small amounts of nitrogen. The unit was restarted once Nuclear and Industrial Safety Agency was satisfied that the countermeasures taken by the plant operator to prevent a reoccurrence were adequate.
- May 2006 it was confirmed that a pipe was leaking due to debris damage.
- June 7, 2006 Difficulties with pressure control prompted further inspections.
- July 7, 2006 METI and the Nuclear and Industrial Safety Agency determined that the plant's performance was not satisfactory.
- July 7, 2006 Due to pipe integrity concerns the reactor was shut down.
- November 25, 2006 Following repairs the reactor was restarted.
Small fire in the administrative offices. Did not affect functioning of the plant.
The Onagawa Nuclear Power Plant was affected by the 2005 Miyagi earthquake and recorded vibrations above what the plant was designed for. Analysis after the event, however, found no damage to the reactor systems. Some people reported seeing smoke come from the plant after the earthquake and reported it, thinking that it indicated an accident, but the smoke was actually produced by the backup diesel generators.
The Onagawa Nuclear Power Plant was the closest nuclear power plant to the epicenter of the 11 March 2011 Tōhoku earthquake, less than half the distance of the stricken Fukushima I power plant. However no reactor damage occurred at the Onagawa plant.  The town of Onagawa to the northeast of the plant was largely destroyed by the tsunami which followed the earthquake, but the plant's 14 meter (46-foot) high seawall was tall and robust enough to prevent the power plant from flooding, The reactors automatically shut down without damage, and all safety systems functioned as designed. A fire which broke out in the Power Plant, in a building housing the electricity-generating turbine, which is sited separately from the plant's reactor, was soon extinguished.
Following the tsunami two to three hundred homeless residents of the town who lost their homes to the tsunami took refuge in the Onagawa nuclear plant's gymnasium, as the reactor complex was the only safe area in the vicinity to evacuate to, with the reactor operators supplying food and blankets to the needy. At the time Reuters suggested that the Onagawa nuclear power plant may demonstrate that it is possible for nuclear facilities to withstand the greatest natural disasters, and to retain public trust. The plant was shut down following the earthquake and tsunami, in accordance with standard legally mandated procedure after such an event, but despite the IAEA finding that the plant had survived the quake remarkably undamaged,  the three units remain in cold shutdown. Whereas the mishaps at Fukushima I radically changed public opinion on safety and risks, Tohoku Electric seems to have preserved much of its pre-disaster goodwill in the area of Onagawa. While the tsunami was more than 13m high at both Fukushima I and the Onagawa power plant, the largest difference between them, apart from the reactor safety systems being designed some twenty years apart, the Fukushima I seawall was built to a height of just 5.7m. Whilst the Onagawa power plant seawall was nearly 14m high and thus successfully blocked the tsunami from causing flood damage. It was this tsunami at Fukushima I that has been determined to be solely responsible for precipitating the loss of cooling and ultimately the Fukushima disaster which had a much shorter sea wall of 6 meters.
On 13 March 2011, two days after the earthquake and tsunami, levels of radiation on site reached 21μSv/hour, a level at which Tohoku Electric Power Company were mandated to declare a state of emergency, and they did so at 12:50, declaring the lowest-level such state. Within 10 minutes the level had dropped to 10μSv/hour. The Japanese authorities believe the temporarily heightened values were due to radiation from the Fukushima I nuclear accidents and not from the Onagawa plant. On March 13 20:45 UTC, the IAEA announced that radiation levels at the Onagawa plant had returned to normal background levels.
A 7 April 2011 aftershock damaged 2 of the 3 power lines connecting to the plant, but it did not damage any of the backup cooling systems, which remained undamaged and unneeded, including the ESWS, the ECCS and the back up diesel generators.
- 2011 Japanese nuclear accidents
- List of boiling water reactors
- Lists of nuclear disasters and radioactive incidents
- Tohoku Power. The Onagawa Plant (information).
- Tohoku Power. Onagawa Nuclear Power Station.
- Toshiba. Nuclear List of Delivered Units.
- Manual Shutdown of Onagawa NPP Unit-1
- Yamaguchi, Mari, Associated Press, "Nuke plant near quake epicenter undamaged", Stars and Stripes, 11 August 2012, p. 8
- Mogi, Chikako (March 11, 2011). "Fire at Tohoku Elec Onagawa nuclear plant". Reuters. Kyodo | Reuters. Retrieved March 13, 2011.
- Mogi, Chikako (11 March 2011). "Fire at Tohoku Elec Onagawa nuclear plant -Kyodo | Reuters". Reuters. Archived from the original on 18 April 2011. Retrieved 13 March 2011.
- "Fire at nuclear power plant extinguished". The Australian. 12 March 2011. Archived from the original on 18 April 2011. Retrieved 13 March 2011.
- Ito, Shingo (Agence France-Presse/Jiji Press), "Neighbors of Miyagi reactor mull getting out", Japan Times, 1 April 2011, p. 3.
- Hafez Ahmed @ http://www.thefinancialexpress-bd.com. "March 2011 Japan's atomic plant neighbours mull leaving homes". Thefinancialexpress-bd.com. Archived from the original on 28 July 2011. Retrieved 7 September 2011.
- Plant weathered Japan quake well: IAEA
- "Contamination checks on evacuated residents". world-nuclear-news.org. 2011. Retrieved March 13, 2011. "A technical emergency was declared at 12.50 pm today at the Onagawa nuclear power plant after radiation levels in the plant site reached 21 microSieverts per hour. At this level plant, owner Tohoku Electric Power Company is legally obligated to inform government of the fact. Within just ten minutes, however, the level had dropped to 10 microSieverts per hour."
- "IAEA update on Japan Earthquake". iaea.org. March 13, 2011. Retrieved March 13, 2011. "Japanese authorities have also informed the IAEA that the first (i.e., lowest) state of emergency at the Onagawa nuclear power plant has been reported by Tohoku Electric Power Company. The authorities have informed the IAEA that the three reactor units at the Onagawa nuclear power plant are under control. As defined in Article 10 of Japan's Act on Special Measures Concerning Nuclear Emergency Preparedness, the alert was declared as a consequence of radioactivity readings exceeding allowed levels in the area surrounding the plant. Japanese authorities are investigating the source of radiation."
- Chico Harlan, Steven Mufson: Japanese nuclear plants' operator scrambles to avert meltdowns. The Washington Post, March 11, 2011
- IAEA (2011). "Fukushima Nuclear Accident Update Log - Updates of 13 March 2011". iaea.org. Retrieved March 13, 2011.
- "Sea water injected into troubled Fukushima power plant | The Manila Bulletin Newspaper Online". mb.com.ph. 2011 [last update]. Retrieved March 13, 2011. "Meanwhile, radiation monitored at the Onagawa nuclear power plant in Miyagi Prefecture on the Pacific coast shot up on Sunday, Tohoku Electric Power Co. said, adding that it was likely caused by radioactive substances let out at the troubled Fukushima No. 1 nuclear power plant in Fukushima Prefecture."
- Japan earthquake today: Tsunami warning lifted, but Fukushima evacuated, Christian Science Monitor, Gavin Blair, April 7, 2011