Japan Earthquake: nuclear plants

LabratSR

From Atomic Power Review.

Major New Report released by TEPCO.

http://www-pub.iaea.org/iaeameetings...n/Suzuki_d.pdf

zapperzero

Took a quick look. The bit about shortening the cooling loops is rather interesting, as is the fact that currently the cooling water is only being scrubbed of cesium.

I kinda stared a little at the picture of workers in street clothes... apparently air dose rates at site boundary (as measured by shielded detectors in decontaminated locations) are a good indicator of the overall contamination level of the site.

VCortex

I hope structural integrity and water tightness are not an issue, as it seems the grand plan involves filling everything up to the brim with water.

a.ua.

But then it would be hydrogen only on the 5th floor.
However, the explosion was also on 4 and 3 floors.

zapperzero

You seem a bit confused. There is no simple way to tell where the hydrogen was and wasn't - you can only see the damage caused by the blast (which does indeed extend downwards as well as outwards).

LabratSR

After taking a closer look at the Sandia National Labs report, I found a link inside it to an information portal established at Idaho National Labs.

https://fukushima.inl.gov/

From there, click the "Public" link and you can get access to other stuff such as this report.

https://fukushima.inl.gov/PDF/FDASIP-Ver-6.pdf

LabratSR

From the INL portal.


"Enhanced Ex-Vessel Analysis for Fukushima Daiichi Unit 1:
Melt Spreading and Core-Concrete Interaction Analyses with MELTSPREAD and CORQUENCH"

https://fukushima.inl.gov/PDF/MELTSP...%20Feb2013.pdf

LabratSR

Reassessment of Fukushima Nuclear Accident
and Outline of Nuclear Safety Reform Plan

http://www.tepco.co.jp/en/press/corp...21214e0201.pdf

Joffan

Through the faint haze of translation, this seems like an excellent internal response from Tepco.

zapperzero

Excellent, you say. Have you read it? There's a lot of pious noise and nothing BUT reactive measures, based solely on what happened in this particular accident. They are preparing to weather another tsunami, not to improve safety overall. The next accident will again be a surprise that no-one could have predicted. Maybe a crane will make a nest in their new autocatalytic recombiner.

So now it will be easy to explain that the NPPs are completely safe?

LabratSR

Ok Zap, You have SO honed in on EXACTLY my problem. No two incidents EVER happen the same. They are concentrating on the last accident instead of the NEXT. BULLSEYE.

turi

Well to be fair, they do divide the response into two parts: "Direct measures based on [...] Accident" and "Measures to structural problems[...]". It's from the latter where one would expect to see changes in the safety culture of the company and new risk assessments. But it would be equally stupid not to learn the direct lessons from the accident. Especially as those direct lessons (spare high pressure pumps, better means to bring in external power and coolant supplies, more resilient power supply, more redundancy in lighting and communication...) can help if something completely different than a tsunami occurs.

jim hardy

The objective is in simplest terms to move decay heat to a heat sink.

A. The science of that is not so difficult - reliable pumps and reliable power for them.


B. Human nature is complex. To get a committee(or a group of committees) to agree on how to go about achieving A is daunting.

That the TEPCO report speaks to both is positive IMHO.

tsutsuji

The NHK has another surprising story, dated 10 March 2013 :

http://www3.nhk.or.jp/news/genpatsu-...310/index.html : As specialists had suggested that part of the water injected by fire-engine had leaked somewhere, the NHK procured by itself the unit 3 piping drawings and conducted a detailed analysis together with some specialists.

As a result, it was found that there is a byroad starting between the fire-engine and the reactor, and there is a possibility that water runs through the byroad and leaks into another device which is not the reactor.

At the end of the byroad, there is a device called "condenser" which is used to generate electricity and transforms steam back into water. Normally, the pump that is located there on the way, is running, so that the water is kept back, so that it does not flow into the condenser.

However, as we tested in an experiment with the help of the specialists, it was found that in the case where the pump is down, the water flows through without stopping, and there is a high probability that the water leaked during the Fukushima accident as all electric power had been lost.

This experiment result is corroborated by a press conference held by Tepco immediately after the accident, where Tepco indicated that at that time, unit 3's condenser was in a full-of-water status which cannot happen in normal time.

Furthermore, when unit 3's water flow generated by fire-engine injection is experimentally reconstructed and when that experimental result in used by specialists in a simulation, they find that 55% of the water volume leaks out instead of being injected into the reactor, and they conclude that this leaked amount is sufficient to explain why the meltdown could not be averted.

On the other hand, they conclude that if the leaked amount had been 25% or less, the meltdown could have been averted.

After the accident, fire-engines have been installed as a safety measure at every nuclear power plant in the country, but more than two years after the accident, what is emerging is that sufficient verifications have not been carried out about how certain it is that the water will enter the reactor.

According to Hosei University visiting professor Hiroshi Miyano, "the job is not finished after fire-pumps are installed, and it is meaningless if one does not check if a sufficient amount of water for cooling the nuclear fuel is coming into the reactor. The verifications made after the accident have not been sufficient."

http://www3.nhk.or.jp/daily/english/20130310_28.html (NHK World English version)

etudiant

Welcome back, Tsutsuji-san, your insightful comments have been missed!

Once again, this report underlines the need for practical training.
Theoretical studies of what happens in the event of a complete power failure may miss major complexities in the real world system that only become apparent when actually exercised.
Is there any program in Japan to actively train operators to deal with such a complete station black-out contingency?

jim hardy

Arrgh !
Usually there's a check valve at a pump discharge to prevent just that from happening..reverse flow when pump is off.
But check valves can stick partway open......

Big disasters are always a string of dominoes , little things individually until something pushes the first one over.
That's how "... the small thngs of the earth confound the mighty".

Welcome back tsutsuji (finally i spelled it right ! )

nikkkom

Sounds much better than response from almost every other country's nuclear industry, which 95% of the time boils down to "we checked our accident preparedness and it's just fine, we aren't like those stupid Japanese. Nothing needs to be done". Yeah right...