ECCS and the causes for the failures at Fukushima Diiachi

In response to a previous post on this topic, a nuclear engineer left the following comment:

“The RCIC system was only DESIGNED to operate at 8 hours. I agree it should run indefinitely, but 8 hours is well beyond what the system is designed to do in a single run, especially with no suppression pool cooling.

RCIC cools itself using a little bit of the water that it is pumping. RCIC operates in 2 modes, 1 which draws from an outside tank, and 2 which draws from the suppression pool inside the containment. When water is no longer available from the tank, RCIC runs in pool mode, which means it uses the pool water to cool itself. With no power to run the pool heat removal systems, the water temperature heats up, and eventually either through a loss of NPSH or through the increase in temperature in the cooling water to the turbine, RCIC fails mechanically.”

And I appreciate this information very much. I re- read the Nuclear Society of America’s Accident report on Fukushima Diiachi. I have about my understanding of ECCS arose as a result of my reading of Nader and Abbott, and as a result of the common knowledge I and others have held (from simple schematics) that the GE Mk1 design included reactor steam powered turbines which powered emergency pumps. I also had awareness of the ‘ECCS’ controversy as described by the “NRC short history” . Lastly I found the NRC Acceptance Criteria for Emergency Core Cooling Systems here:

The paragraph which states the requirement which perplexed me to a very great degree in relation to the events at Fukushimna Diiachi is this one :”(5) Long-term cooling. After any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.”

My understanding was that the reactors in question had self powered Emergency Core Cooling Systems in all aspects. And that is a wrong assumption.

As for the RCIC and I gather the HPCI also, while the torus/suppression pool can act as a heat bank, it cannot on its own act as heat radiator. It’s design gives a “buffer” period of some hours.

The detailed NSA accident description gives the events which led to the failure of each reactor, and I shall place the text here tomorrow. The Nuclear Society of America report is here:

The assumption that the Emergency Core Cooling System was totally self powered from the intrinsic power of the reactor (steam) is false. I held that believe in error. It is however tragic that the reactors, which power the grid, cannot power essential systems in station blackout. That leaves me in a circular loop of thought, for the promise of safety embodied in the criteria that “decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.” only holds true if the ECCS is externally powered.

And that confirms the tragic view that foresight appropriate to the undertaking did exist, and that foresight did cause objections to be raised many years ago. At that time, regulators ignored these warnings. This is the group-think which enabled the Fukushima Diiachi to exist. The ECCS did not work. That, as a layman, is all I need to know.

It was coincidence that led me to be reading Nader and Abbott’s book in Feburary – March of 2011. At the time of the disaster in Japan, as each reactor blew, I asked myself where is the ECCS?

2 Responses to “ECCS and the causes for the failures at Fukushima Diiachi”

  1. CaptD Says:

    I salute the Nuclear Engineer for posting and also want to say that many believe that reports BASED UPON TEPCO DATA ARE HIGHLY SUSPECT SINCE THEY HAVE A HISTORY OF SUBMITTING FALSE REPORTS…

    This further complicates matters since reports written by the Nuclear Society of America and others may N☢T be based upon factual data!

    Here are the actual US NRC emails* made after 3/11/11, they give a great insight into just how “bad” things were at the time, not that sometimes they started speaking in Spanish and or “code” to remind each other that they should watch what they say, knowing that these emails might be made public…

    IMO They were more concerned about PR “damage control” than anything else! There was a later directive for people working in other US National Labs to not get involved unless they had permission (Hint: Don’t say or volunteer any help)…

    Even the Japanese are still debating what caused the reactors to meltdown:

    The Loss of Coolant risk in reactors and the urgent call for a “technical fix” that never came.
    Fukushima nuke disaster investigative panel rejects TEPCO tsunami claims

    Even without getting into “far out” “causes” like this:


    Making money is one thing but controlling a Government is quite another (a must read article):
    The Nuclear Mafia Derails Democracy in Japan

    Power industry campaigns to pull the plug on the DPJ


    Quakes will become much more important as scientists and especially the Nuclear Industry admits that they don’t know as much about them as they thought they did, instead they have just been very lucky until now…

    Think shaman throwing bones and trying to decipher the future!

    Fukushima proved that Nature can destroy any land based nuclear reactor, any place anytime 24/7/365 and all the mathematical modeling in the World cannot change the FACT that even if something has a once in a thousand year probability, IT STILL CAN HAPEN TOMORROW!

    That is a key factor we must all remember…

    Ask The Japanese, they’re now paying for a Trillion Dollar Eco-Disaster because they believed their Nuclear Professionals knew far more than they did, when they claimed that nuclear energy was 100% safe!

    * I suggest you save these to disc since they could be “removed” at any time…

  2. Mara Says:

    Sorry but I have to note that you are mispelling Daiichi–it is not

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