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Key Valves Failed at Fukushima

Posted February 06, 2016 12:00 AM by Engineering360 eNewsletter

Nearly five years after a 9.0 magnitude earthquake in Japan triggered an accident at the Fukushima Daiichi nuclear power station, the Tokyo Electric Power Co. concluded that key pressure relief valves failed, preventing water from being injected into the Unit 2 reactor to reduce pressure. Failure was likely caused by rising temperatures and extreme stresses that built up in the early stages of the March 2011 disaster. In the Unit 3 reactor, valves initially failed because of insufficient electricity, according to TEPCO's 4th Progress Report.


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#1

Re: Key Valves Failed at Fukushima

02/06/2016 5:09 PM

That disaster is not over yet in many many many ways.

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#2

Re: Key Valves Failed at Fukushima

02/06/2016 8:00 PM

Seems like pressure relief valves for plant safety should operate on overpressure.

There were engineers involved in the construction of these reactors that attempted to get many of the design and construction errors corrected. They lost their jobs.

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#3
In reply to #2

Re: Key Valves Failed at Fukushima

02/07/2016 2:17 AM

Two weeks ago we were talking about the Challenger disaster, and how the "administrative process" overruled engineering decisions.

So, what else is new?

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#4
In reply to #3

Re: Key Valves Failed at Fukushima

02/07/2016 3:26 AM

'..what else is new?'

.

Doubly nothing since the problems with Fukushima Daiichi plant predate the Challenger problems.

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#5

Re: Key Valves Failed at Fukushima

02/10/2016 5:32 AM

valves initially failed because of insufficient electricity...Then that's not a valve failure is it?
Del

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#6
In reply to #5

Re: Key Valves Failed at Fukushima

02/10/2016 8:43 AM

I think the article was not clear and possibly unintentionally misleading. It's doubtful that the pressure relief valves were electrical and failed because of insufficient electricity.

When I read that line (valves initially failed because of insufficient electricity ) it made me think that the operation of electrically controlled valves failed causing increased temperatures and pressures thus requiring the pressure relief valves to function.

Subsequently, those failed.....or maybe had failed at some point in the distant past.

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#7
In reply to #6

Re: Key Valves Failed at Fukushima

02/10/2016 8:45 AM

Many approach design with the idea that having safety elements (pressure relief valves, etc.) will mitigate risk. I don't know how many times I hear managers and even engineers use the argument "We are not required to design for simultaneous failures". And while in many systems there may not be a requirement to design for simultaneous failures, it's a fallacy that such system failures are simultaneous.

For instance, a safety valve (passive pressure relief valve) may sit unused (closed) for years. It may have failed at some point over those years....maybe even year one. That's just a single failure. However, no one is aware of it and it exists for years after it's failure. Eventually another failure occurs in the system which requires the safety system to function. These are not simultaneous failures. Yes, they exist at the same time, but the failures are serial.

Hence the importance of periodically testing safety components.

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