Fukushima plant chief admitted mishandling of reactor cooling system

[FBaggins]

Before his death from cancer last year, Masao Yoshida told a government committee that he felt “regret” for making a “wrong presumption” in handling the critical situation in the wake of the Great East Japan Earthquake and tsunami.

According to a copy of Yoshida’s testimony, recently obtained by The Asahi Shimbun, a worker at the plant’s central control room noticed that the cooling system, an isolation condenser (IC) attached to the No. 1 reactor, was losing its functions on the evening of March 11, 2011. Suspecting that the condenser was losing cooling water, the worker requested that Yoshida, who was in the emergency response center, take steps to refill the condenser with water using a light oil-powered pump.

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The isolation condenser serves as a last-ditch measure to cool the reactor when ordinary pumps cannot operate due to a lack of outside power supplies and emergency generators. Placed above the reactor vessel, it cools steam from the pressure vessel, condenses it into water and returns water into the reactor. Steam is cooled as it passes through piping in a water-filled tank, which needs to be refilled after water evaporates in the process.

But Yoshida was unaware of how the mechanism worked, because it was the first time that an isolation condenser was operated at the plant in 20 years.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201405230034