Japan Earthquake: Nuclear Plants at Fukushima Daiichi

In summary: RCIC consists of a series of pumps, valves, and manifolds that allow coolant to be circulated around the reactor pressure vessel in the event of a loss of the main feedwater supply.In summary, the earthquake and tsunami may have caused a loss of coolant at the Fukushima Daiichi NPP, which could lead to a meltdown. The system for cooling the reactor core is designed to kick in in the event of a loss of feedwater, and fortunately this appears not to have happened yet.
  • #13,826
turi said:
Do you have any indication that radiolysis would be a significant source of hydrogen compared to zirconium, steel and B4C steam oxidation? Those three sources are modeled in the analysis.

Where did the hydrogen in Unit 4 come from? We're told it went into the unit 3 SGTS from the torus room, then instead of going up the stack it traveled through the vent pipe into unit 4, where it exploded... 19 hours after Unit 3 itself went up.

I have provided elsewhere here citations of research into steam radiolysis. Apparently it is much more efficient than water radiolysis. My idea, and it is nothing more than an idea as I obviously can't run experiments of any kind and I don't even have access to the relevant simulation codes, is that localized bubbling on the surface of fuel elements in the spent fuel pool (where water was no longer circulated by pump, only by convection) might have created the conditions for the production of a sufficient amount of hydrogen.
 
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  • #13,828
LabratSR said:
From Atomic Power Review.

Major New Report released by TEPCO.

http://www-pub.iaea.org/iaeameetings/IEM4/30Jan/Suzuki_d.pdf

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.
 
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  • #13,829
  • #13,830
zapperzero said:
I have provided elsewhere here citations of research into steam radiolysis. Apparently it is much more efficient than water radiolysis. .
But then it would be hydrogen only on the 5th floor.
However, the explosion was also on 4 and 3 floors.
 
  • #13,831
a.ua. said:
But then it would be hydrogen only on the 5th floor.
However, the explosion was also on 4 and 3 floors.

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).
 
  • #13,832
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
 
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  • #13,833
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/MELTSPREAD%20CORQUENCH%20Analysis%201F1%20ORNL_ANL%20Feb2013.pdf
 
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  • #13,836
Joffan said:
Through the faint haze of translation, this seems like an excellent internal response from Tepco.

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.

We thought it would have been difficult to explain that the current nuclear power station was completely safe if we had recognized that measures for handling severe accidents were necessary

So now it will be easy to explain that the NPPs are completely safe?
 
  • #13,837
zapperzero said:
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?


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.
 
  • #13,838
zapperzero said:
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.

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.
 
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  • #13,839
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.
 
  • #13,840
The NHK has another surprising story, dated 10 March 2013 :

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130310/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)
 
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  • #13,841
tsutsuji said:
The NHK has another surprising story, dated 10 March 2013 :

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130310/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.

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)

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?
 
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  • #13,842
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.

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 ! )
 
  • #13,843
zapperzero said:
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.

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...
 
  • #13,844
Russian already invested tens of millions $ in the purchase of new mobile devices to transmit power and high-power pumps.
In Ukraine, not so well (we have less money), but the technique is bought .
And the most important exercise and a good knowledge of their own nuclear power plant.
 
  • #13,845
IRSN explaining the accident:



Nothing new, but everything already uncovered neatly packed together with animations. :)
 
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  • #13,846
http://www3.nhk.or.jp/news/genpatsu-fukushima/20130318/index.html an electric power black out happened on 18 March before 7 PM at the seismic isolated building. After checking, it was found that some of the electric systems were down. The water injection into units 1,2,3 is not affected. However, the cooling of SFP 1, 3 and 4 has stopped. SFP temperatures are between 13.7 and 25 °C. Temperature rise is between 0.1 and 0.3 °C per hour, so that it would take at least 4 days to reach 65°C. Tepco is investigating the cause of the black out and intends to proceed to SFP cooling restart work in function of the investigation results. The nuclear power regulation agency said there was some trouble near a cable connected to a high power switchboard. Monitoring post values are stable. Tepco says it is sorry for being late to disclose the information, as a consequence that it took some time to check the situation.
 
  • #13,848
http://www3.nhk.or.jp/news/genpatsu-fukushima/20130319/index.html Unit 1 SFP cooling was recovered on 19 March shortly after 02:00 PM. Unit 4 SFP cooling was recovered by the implementation of measures such as connecting emergency power generators shortly after 04:00 PM.

The other cooling systems are expected to be recovered by 20 March 2013 08:00 AM.

unit 1,3,4 spent fuel pools and the common pool's cooling systems stopped on 18 March after 3 switchboards connecting to the outside electric power were down.

On 19 March the work to recover two of those swichboards was completed and unit 1 SFP cooling could be started again after a 19 hour long stop.

Unit 4 SFP cooling was restarted using a backup power generator used as an alternative to the remaining switchboard.

Unit 3 SFP cooling is expected to be restarted by around 19 March 08:00 PM, after switching to a different switchboard.

The common pool is expected to be restarted by around 20 March 08:00 AM.

As far as could be checked by visual examination, no damage is seen at the swichboards where the problem occurred, and Tepco is still investigating the causes.

SFP 4 temperature rose from 25°C to 30°C before the cooling was started again, so that the 65°C limit set by the regulation was not reached.

Tepco said it apologizes for causing people to worry as a result of these troubles and apologized again for having been about 3 hours late to publicly disclose the trouble.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130319_02-e.pdf Power Supply Facilities Failure at Fukushima Daiichi Nuclear Power Station [the title says "As of 4:30 PM on March 19", but it is more likely to be as of 3:30 PM, as they don't mention unit 4 SFP secondary system as being recovered]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130319_04-j.pdf unit 4 SFP cooling secondary system was recovered at 16:13 on 19 March.
 
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  • #13,849
Possible cause for the blackout:

A rat may have short-circuited a switchboard.

Tokyo Electric Power Company says it has found burn marks on one of the power distribution boards that stopped working and brought to a halt cooling systems for spent-fuel pools at the damaged Fukushima Daiichi nuclear plant.

A small animal that appeared to be a rat was also found dead near the board. The company suspects the animal touched the terminal of the board and caused a short circuit.

http://www3.nhk.or.jp/daily/english/20130320_28.html

I'm at a loss for words...
 
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  • #13,850
I don't see anything strange about it. Rats exist. They can crawl into all sorts of spaces.
 
  • #13,853
According to Tepco, the power blackout of Fukushima plant was caused by a mouse that came in the terminals to have caused a short circuit.

trying to switch the blame to a dead mouse, good luck with that Tepco, it wasn't a design flaw at all.
 
  • #13,854
That switchgear looks to have flashed over.

I suspect the culprit was one of that mouse's buddies. There should have been nothing left of him. 480 volt makes a loud "BOOM" when it flashes.
 
  • #13,855
jim hardy said:
That switchgear looks to have flashed over.

I suspect the culprit was one of that mouse's buddies. There should have been nothing left of him. 480 volt makes a loud "BOOM" when it flashes.

Europe uses 220V as its standard voltage. I assure you from first hand experience that 220V electric shock doesn't do anything close to that.
 
  • #13,856
Strength damage also depends on the current.
I saw the burning copper thick wire at 36 volts.
And even a 12 volt battery can kill.
If they fall on you from above.:smile:

Europe uses 380V as its standard voltage.
 
  • #13,857
jim hardy said:
That switchgear looks to have flashed over.

I suspect the culprit was one of that mouse's buddies. There should have been nothing left of him. 480 volt makes a loud "BOOM" when it flashes.
So does 440 volts and about 10 or more amps. I know from personal experience when a ground a hot line. There was a bright blue-white flash, my body went stiff, the wrench (I was using the wrench to close a switch that was supposed to be dead) I was holding flew out of my hand, I flew backwards against the wall behind me, and I could smell burning hair and skin. Needless to say, I felt like I'd been hit with a sledgehammer all over. It took me a few minutes to recover, at which point I got myself out there, back to the office, and told I was taking the rest of the day off.
 
  • #13,858
nikkkom said:
Europe uses 220V as its standard voltage. I assure you from first hand experience that 220V electric shock doesn't do anything close to that.
Sorry, the StandarD Voltage in Europe is 230/400V (D/FR/AUT/NL/DK)
 
  • #13,859
triumph61 said:
Sorry, the StandarD Voltage in Europe is 230/400V (D/FR/AUT/NL/DK)

It is now. It wasn't always.
 
  • #13,860
since 1987
 

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