Mihama Nuclear Power Plant
Encyclopedia
The is operated by The Kansai Electric Power Company, Inc.
and is in the town of Mihama
, Fukui Prefecture
, about 320 km west of Tokyo. It is on a site that is 520,000 m2 of which 60% is green space.
with full activation of the Emergency Core Cooling System. Eventually, a small amount of radiation was released to the outside.
The Mihama 3 is an 826 megawatts electric, 3-loop Westinghouse type pressurized-water reactor (PWR) which has been in service since 1976. The pipe rupture occurred in a 55.9 centimeter (cm) (22 inch) outside diameter pipe in the ‘A’ loop condensate system between the fourth feedwater heater and the deaerator, downstream of an orifice for measuring single-phase water flow. At the time of the secondary piping rupture, 105 workers were preparing for periodic inspections to commence.
A review of plant parameters did not uncover any precursor indicators before the accident nor were there any special operations that could have caused the pipe rupture. An investigation concluded that water quality had been maintained since the commissioning of the plant.
Japan's previous most deadly accident at a nuclear facility took place at a uranium processing plant in Tokaimura
, north of Tokyo, on September 30, 1999, when an uncontrolled nuclear chain reaction was triggered after three poorly trained workers mixed Uranium
nuclear fuel in a bucket. The resulting release of radiation killed two workers
, and exposed one other worker to radiation above legal limits.
The Mihama NPP started back up in January 2007 after making various changes and obtaining permission from Fukui Prefecture
and industry regulators.
Kansai Electric Power Company
, also known as , is an electric utility with its operational area of Kansai region, Japan . The company is regarded as one of the leading companies in Kansai, as well as a leader of the Japanese electric power industry....
and is in the town of Mihama
Mihama, Fukui
is a town located in Mikata District, Fukui, Japan.As of 2003, the town has an estimated population of 11,148 and a density of 73.19 persons per km²...
, Fukui Prefecture
Fukui Prefecture
is a prefecture of Japan located in the Chūbu region on Honshū island. The capital is the city of Fukui.- Prehistory :The Kitadani Dinosaur Quarry, on the Sugiyama River within the city limits of Katsuyama, has yielded the Fukuiraptor kitadaniensis and Fukuisaurus tetoriensis as well as an unnamed...
, about 320 km west of Tokyo. It is on a site that is 520,000 m2 of which 60% is green space.
Reactors on Site
| Unit | Reactor Type | Average Electric Output | Electric Power Rating | Beginning of Construction | First Criticality | Commission date |
|---|---|---|---|---|---|---|
| Mihama - 1 | PWR Pressurized water reactor Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors... |
320 MW | 340 MW | 01.02.1967 | 08.08.1970 | 28.11.1970 |
| Mihama - 2 | PWR Pressurized water reactor Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors... |
470 MW | 500 MW | 29.05.1968 | 21.04.1972 | 25.07.1972 |
| Mihama - 3 | PWR Pressurized water reactor Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors... |
780 MW | 826 MW | 07.08.1972 | 19.02.1976 | 01.12.1976 |
Events
The Mihama NPP has been notable beyond most nuclear plants due to the severity of accidents that have happened there, the 2004 steam explosion in particular.September 2, 1991
Unit 2 steam generator had one tube fully break. This triggered a SCRAMScram
A scram or SCRAM is an emergency shutdown of a nuclear reactor – though the term has been extended to cover shutdowns of other complex operations, such as server farms and even large model railroads...
with full activation of the Emergency Core Cooling System. Eventually, a small amount of radiation was released to the outside.
May 17, 2003
Unit 2 steam generators had two holes open simultaneously. There was no radioactive release to the environment.August 9, 2004
On 9 August 2004, an accident occurred in a building housing turbines for the Mihama 3 reactor. Hot water and steam leaking from a broken pipe killed four workers and resulted in seven others being injured. The accident had been called Japan's worst nuclear power accident before the crisis at Fukushima I Nuclear Power Plant.The Mihama 3 is an 826 megawatts electric, 3-loop Westinghouse type pressurized-water reactor (PWR) which has been in service since 1976. The pipe rupture occurred in a 55.9 centimeter (cm) (22 inch) outside diameter pipe in the ‘A’ loop condensate system between the fourth feedwater heater and the deaerator, downstream of an orifice for measuring single-phase water flow. At the time of the secondary piping rupture, 105 workers were preparing for periodic inspections to commence.
A review of plant parameters did not uncover any precursor indicators before the accident nor were there any special operations that could have caused the pipe rupture. An investigation concluded that water quality had been maintained since the commissioning of the plant.
Japan's previous most deadly accident at a nuclear facility took place at a uranium processing plant in Tokaimura
Tokai, Ibaraki
is a village located in Naka District, Ibaraki, Japan. It is approximately 120 km north of Tokyo, Japan on the Pacific coast.As of 1 January 2005, the village has an estimated population of 35,467 and a population density of 946.29 persons per km²...
, north of Tokyo, on September 30, 1999, when an uncontrolled nuclear chain reaction was triggered after three poorly trained workers mixed Uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
nuclear fuel in a bucket. The resulting release of radiation killed two workers
Tokaimura nuclear accident
The Tokaimura nuclear accident , which occurred on 30 September 1999, resulted in two deaths. At that time, it was Japan's worst civilian nuclear radiation accident. The criticality accident occurred in a uranium reprocessing facility operated by JCO , a subsidiary of Sumitomo Metal Mining Co...
, and exposed one other worker to radiation above legal limits.
The Mihama NPP started back up in January 2007 after making various changes and obtaining permission from Fukui Prefecture
Fukui Prefecture
is a prefecture of Japan located in the Chūbu region on Honshū island. The capital is the city of Fukui.- Prehistory :The Kitadani Dinosaur Quarry, on the Sugiyama River within the city limits of Katsuyama, has yielded the Fukuiraptor kitadaniensis and Fukuisaurus tetoriensis as well as an unnamed...
and industry regulators.