Onagawa (Japan)

Map of Onagawa

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1* 500 MW BWR grid connection in 1983
2* 800 MW BWR grid connection in 1994 and 2001
all units by Toshiba

Facilities in Onagawa

plantreactor typconstruction startoperation startshut down
Orchid IslandLLW storage

"In Onagawa-3 during adjustment operation, the reactor was shutdown manually in response to an alarm in the offgas-treatment system indicating 'Off-Gas Dehumidification Cooler outlet Hydrogen concentration high'"


"Under adjustment operation, during a manual start-up test of the high-pressure coolant injection pump, the flow rate at the outlet side was too low. The situation did not improve when a regulating valve was adjusted, so the reactor was shut down manually. The valve stem and parallel pin were broken due to fatigue caused by cavitration within the valve."


"Leak found at insturmentaion nozzle during periodic inspection of Onagawa-1."
(source: http://cnic.jp/english/)


"Cracks found at core spray nozzles during periodic inspection of Onagawa-1."
(source: http://cnic.jp/english/)


"Wastage found at residual heat removal system welds during periodic inspection of Onagawa-1."
(source: http://cnic.jp/english/)


"Cracks found at welds of core shroud (made of SUS304L) middle and lower region during periodic inspection of Onagawa-1; cracks found at outside surface of H2 position and at outside surface of H6a position."
(source: http://cnic.jp/english/)


"Reactor Onagawa-2 manually shut down due to increased water leak from recirculation pump mechanical seal."
(source: http://cnic.jp/english/)


"Coolant leak detected at condenser coolant flux measurement pipe during periodic inspection; 8cm crack found in welds of two measurement pipes."
(source: http://cnic.jp/english/)


Reactor Onagawa-2 manually shutdown due to coolant leak from degraded recirculation pump mechanical sealing.
(source: http://cnic.jp/english/)


Despite Japanese plans, reiterated by the Ministry of International Trade & Industry (MITI) last week, to build 20 new reactors by 2010, the country's nuclear vision will not be realized by a long shot.

Construction of Onagawa-3 by Tohuku Electric Power got underway in 1996 and is expected to be finished in 2002. Tohuku also has approval for construction of Higashitori-1 but construction has not yet commenced.
MITI and Japanese utilities say that, without adding 20 reactors, Japan won't meet its COP3 targets. But Yoshihiko Sumi, executive vice president of Kansai Electric Power Co., predicts that even with all the reactors on line, Japan in 2010 will exceed 1990 emissions levels by more than 20%.
Tepco officials said that Japan's biggest utility last year saw power demand increase by 3%. This year, given Japan's economic slump, demand growth is expected to be lower, unless a hoped-for increase in household consumption, led by more use of air conditioners, makes up for an anticipated lag in demand from Japanese industry.


Onagawa 3 is granted construction permit
Minister of International Trade Industry, on April 12, granted Tohoku Electric Power Co. permission for the construction on Onagawa 3 in Onagawa-cho, Miyagi Prefecture, as planned. Once built it will be the 53rd commercial reactor in Japan. The last time permits were granted they were for Kashiwazaki 6 and 7 in May 1991.


Construction start: excavation for the foundations; construction of the buildings will begin next year. The RPV is due to be installed in 2000, commercial operation is scheduled to start in 2002.
Company says it will "actively employ" new technologies; the unit will have an advanced MARK-I containment.


Manual shutdown due to steam leak from near control valve of moisture seperator reheater.


Start of commercial operation.


Scram due to an earthquake.


Steam leak from coolant purification system: radioactive coolant escaped from an isolation valve of the coolant filtering system. Operation continued, the leaky part of the system was shut down.