Onagawa nuclear plant

Onagawa nuclear plant is 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.

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.

2011.03.11 Earthquake
After the earthquake and tsunami 2011.03.11, the Onagava nuclear plant had problems, although they are reported to be small compared to the Fukushima disaster. In particular, instead of to evacuate away from the plant (as in the case of Fukushima), hundreds of residents are reported to find refuge at Onagawa .

It is believed, that the Onagawa nuclear plant survived the earthquake 2011.03.11 and the tsunami (and did not explode as the Fukushima nuclear plant did) just due to the professional honesty of the engineer Yanosuke Hirai. According to the Takao Yamada (Mainichi Shinbun), the Onagawa nuclear plant survived the 2011.03.11 tsunami, because long ago, Hirai had insisted to built-up the 14.8-meter-tall shield, instead of the 12 m high shield proposed in the basic project. The tsinami 2011.03.11 is estimated to be 13 meter high. .

2011.03.13 splash of radiation
A fire from the turbine section of the plant following the 2011 Tōhoku earthquake was reported . On March 13, 2011, levels of radiation on site reached 21μSv/hour, a level at which Tohoku Electric Power Company were mandated to declare 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 splash of the radioactivity caused the major trace at the contamination map; the article Who contaminates Japan suggests the interpretation as a result of the unauthorized release of radiation from undetermined source, located to North-East from Onagawa, perhaps at the Hamobai island. For year 2012, neither confirmation nor negation of such a concept is available.

The Japanese authorities assume the temporarily heightened values were due to radiation from the Fukushima Disaster and not from the plant itself , and attribute it to the Fukushima Disaster.

On March 13 20:45 UTC, the IAEA announced that radiation levels at the Onagawa plant had returned to normal background levels .

The three units remain in cold shutdown since the earthquake of 11 March.

The April 7th aftershock damaged 2 of the 3 external power lines to the plant but cooling was maintained through the third line .

Wikipedia
Some parts of the content above are copypasted from Wikipedia . The Wikipedia article may be more complete than this article.

Keywords
Fukushima disaster, Earthquake, Tsunami, Nuclear chimney, Who contaminate Japan