, , , ,

Although everyone is told that everything was fine at the Onagawa Nuclear Power Plant, after the 11 March 2011 Tōhoku earthquake, such appears not to have been completely true. A small offshore earthquake on the 26 of January should serve as a reminder of the clear and present earthquake-tsunami danger.
Onagawa NPS 26-1-2015 earthquake vs. 3-11 earthquake
According to English wikipedia: “A fire broke out in the Turbine hall, which is sited separately from the plant’s reactor[17] in a building housing the electricity-generating turbine, but was soon extinguished.[18]http://en.wikipedia.org/wiki/Onagawa_Nuclear_Power_Plant Also reported here: http://fr.wikipedia.org/wiki/Centrale_nucléaire_d%27Onagawa Originally reported from Reuters-Kyodo news: “Fire at Tohoku Elec Onagawa nuclear plant -Kyodo” TOKYO, March 11 Fri Mar 11, 2011 4:45am EST (Reuters) – A fire broke out at Tohoku Electric Power Co’s (9506.T) Onagawa nuclear plant in northeastern Japan following Friday’s major earthquake, Kyodo news agency said….” Originally reported by Justin McCurry of the Guardian (from Osaka): “A fire broke out in a turbine building and was extinguished at the Tohoku Electricity company’s Onagawa nuclear plant in north-east Japan. Smoke was seen coming from the building, which is separate from the plant’s reactor.http://www.theguardian.com/world/2011/mar/11/japan-declares-nuclear-emergency-quake

What if they had been unable to extinguish the fire, given the context of a major earthquake and tsunami?

The 14 meter (46-foot) high seawall better protected it, than the Fukushima Daiichi Nuclear Power Station, but there was still flooding, it seems. http://en.wikipedia.org/wiki/Onagawa_Nuclear_Power_Plant This video shows the tsunami in action: http://youtu.be/0ey-4_iWEfU

According to French wikipedia:
On Friday April 8th (the day after a large 7.1 aftershock) the operator of the nuclear power station announced the leakage of radioactive water from the spent nuclear fuel cooling pools in reactors one and two. Euronews first presented this as a minor incident (small overflow of radioactive water in another reactor situated to the north of Sendai, the Onagawa Nuclear Power Station, which has been shutdown since the March 11th earthquake. The incident is considered minor). Water was found on the ground of the power station on several floors in the three units, but in very small quantity and with a very low level of radioactivity according to Tōhoku electric company. A second Euronews announcement said that radioactive water escaped from spent fuel storage pools in the three reactors of the power plant.

Additionally, Unit Number 2 was damaged by the wave of water. Three other leaks were found in the unit. According to the Tōhoku electric company, the level of radiation around the site did not increase. The Japanese Nuclear and Industrial Safety Agency confirmed that anomalies were reported by the Tōhoku electric company at reactors 2 and 3 after the aftershock. Furthermore, several aerial images illustrating the press releases show that an oil slick (hydrocarbon) was flowing from the power station in the zone protected by dikes and then toward the sea. http://fr.wikipedia.org/wiki/Centrale_nucléaire_d%27Onagawa
Onagawa Nuclear Reactor waterfront-construction
Onagawa is really on the waterfront! Whatever are they working on? Repairs?
According English wikipedia:
The Onagawa Nuclear Power Plant was the closest nuclear power plant to the epicenter of the 11 March 2011 Tōhoku earthquake,[10] less than half the distance of the stricken Fukushima I power plant.[11] The town of Onagawa to the northeast of the plant was largely destroyed by the tsunami[12] 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 experiencing severe flooding. All safety systems functioned as designed, the reactors automatically shut down without damage, and no reactor damage occurred.[13] A fire broke out in the Turbine hall,[14][15][16]which is sited separately from the plant’s reactor[17] in a building housing the electricity-generating turbine, but was soon extinguished.[18]
On 8 April 2011, a small 3.8 liter leak of radioactive water spilled from spent fuel pools holding fuel rods following an aftershock from the March 2011 Tōhoku earthquake.
Hirai Yanosuke, who died in 1986, is cited as the only person on the entire power station construction project to push for the 14.8-meter breakwater. Although many of his colleagues regared 12 meters as sufficient, Hirai’s authority eventually prevailed, and Tōhoku Electric spent the extra money to build the 14.8m tsunami wall. Another of Hirai’s proposals also helped ensure the safety of the plant during the tsunami – Expecting the sea to draw back before a tsunami, he made sure the plant’s water intake cooling system pipes were designed so it could still draw water for cooling the reactors.[33]http://en.wikipedia.org/wiki/Onagawa_Nuclear_Power_Plant

Various “incidences” at the Onagawa Nuclear Power Plant from English wikipedia:
Unit 1
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.[8]
Unit 2
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.[citation needed]
Unit 3
July 7, 2006 Due to pipe integrity concerns the reactor was shut down.
November 25, 2006 Following repairs the reactor was restarted.

Of related interest: Cracks, like those discussed below, could undergo sudden failure, especially in the event of earthquakes

Characterization of Oxide Film on the Surface of SCC in PLR Pipe by Micro Raman Spectroscopy and Its Implication to Crack Growth Characteristics at Onagawa Nuclear Power Plant” by Akira Kai, Michael P. Short, Yuichiro Terayama, Tadashi Tatsuki, Takeshi Watanabe and Tetsuo Shoji, Paper No. ICONE12-49400, pp. 83-92; 10 pages
doi:10.1115/ICONE12-49400, From: 12th International Conference on Nuclear Engineering, Volume 1, April 25–29, 2004 From the abstract: “Micro Raman Spectroscopy (MRS) is known as one of the most convenient techniques for surface analysis. In this study, a MRS system was applied to analyze oxides on a stress corrosion cracking (SCC) fracture surface at the site of a nuclear power plant in Onagawa, Japan. The sample was cut from a cracked component of the Primary Loop Recirculation (PLR) Pipe of the Onagawa Nuclear Power Plant in operation for 14.6 EFPY… These oxides were identified as one or more of the following spinel oxides: NiFe2 O4 , Fe3 O4 , and FeCr2 O4 . These were present over the whole crack surface. It is worthwhile to note that α-Fe2 O3 was detected near the crack mouth and Cr enrichment in the oxides was detected at the crack tip. Although α-Fe2 O3 formed on the surface of austenitic stainless steel exposed to oxygenated water, since conditions in the shallow crack maintained a low pH and a low electrochemical potential, Cr enrichment and a lack of α-Fe2 O3 would be expected at the crack tip. On the other hand, when the crack opening became large α-Fe2 O3 was observed. Since oxides formed appeared to correspond to the size of the crack opening, oxide analyses were performed on the fracture surfaces of two different size specimens. SCC was generated in these specimens with different crack growth rates in a simulated BWR environment in the laboratory. α-Fe2 O3 was observed near the crack tip in the small specimen with a slow crack growth rate. A correlation between the distribution of oxides and the size of the crack opening was extrapolated. It is likely that the existence of α-Fe2 O3 near the crack tip in the plant sample is associated with either blunting or a large crack opening caused by crack growth retardation. Finally, it is assumed that the crack in the plant sample grew in the circumferential direction rather than the radial direction since α-Fe2 O3 was observed closer to the tip of the central part of the crack rather than to the side edge.

[Emphasis throughout this blog post, our own.]

And, before we even finished this post, there was yet another small earthquake in Japan! And, of course, another nuclear power station nearby!
26 Jan 2015 earthquake vs. Tokai NPS