Japan Earthquake: nuclear plants

Jorge Stolfi

I would agree so far, except that the consensus now seems to be that the RPV had been breached several hours earlier, and part of the fuel had already dropped to the bottom of the drywell. Published radiation figures start just before the explosion, on the morning of 3/14, and already show 200 Sv/h in the drywell atmosphere.

There may be some confusion here. AFAIK the concrete shield plugs are meant to block radiation only, not pressure. They may be octagonal in other reactors, but in #2--#4 all drawings indicate that the opening of the refueling pit is round and the plugs are three disks, 1--2 feet thick, each cut into two halves (presumably so that they can be more easily moved and stacked on the cramped service floor). AFAIK those plugs are held in place only by their weight.

This seems unikely. At those temperatures and pressures, any oxygen that remained in the drywell from before the breach or that was generated by radiolysis/thermolysys should have been promptly consumed by the excess hydrogen, before it could buid up to an explosive concentration.

But maybe not.

I did not do the math, but pesumably a massive leak of steam at 60 psi (400 kPa) into the refueling pit could have lifted the shield plugs, enough to let that steam escape into the service storey --- unless it found some easier way out.

However, I do not see how a sudden reduction in pressure (which would have cooled the steam) could have caused it to explode. Everything I see in the wreck suggests that the explosion happened some time after the H2 began to escape -- enough time for it to flow down to the 4th and 3rd storeys and mix with the air. I would rather believe that the steam leaked ignited the colder H2+O2 mixture that was already there, just with for being hot.

According to the floorplans, he "cattle trough" that leads to the SFP (through which steam may be still leaking) is very narrow and short. The gate on the opposite side, to the dryer storage pool (through which steam is definitely still leaking) is as wide as the storage pool. I do not see either as being able to vector the steam significantly upwards.

The head bolts *of the RPV* probably held fine, since the bottom had already been breached so the RPV was at ~400 kPa instead of its normal ~6500 kPa.

But for this scenario we need a path for the steam to get from the drywell to the refueling pit. One possibility is by breaching the diaphragm that connects the drywell wall to the RPV flange, and then leaking between the flanges of the yellow *drywell* cap. This may require stretching the bolts *of the yellow cap*. But there are other possible paths.

Neither do I. I suppose that both gates (to the SFP and to DSP) were closed, and that there was no water in the SDP or in the refueling pit at the time of the explosion.

Joe Neubarth

OK, let's say we dismiss Gunderson's Prompt Criticality theory because we can see a few square feet of what looks like the top of the spent fuel modules. If the fuel modules are in place then there must have been NO EXPLOSION from the pool.
The Hydrogen explosion only seems to carry us so far. We saw the horizontal explosion and almost all of us agree that THAT was the hydrogen explosion clearing out the rafters at the top of the building.
Assuming that we did see a second and more powerful explosion that was directed UPWARDS, what was that?

jim hardy

Bioengineer

Thank you - that's a real interesting article.

It links to this Telegraph article
http://www.telegraph.co.uk/news/worl...interview.html

which repeats the tale as related by an unnamed worker
"As the situation deteriorated, the first explosion, at reactor 3 on March 14, happened at the precise moment that six soldiers from the Japanese Central Nuclear Biological Chemical Weapon Defence Unit arrived at the reactor in two vehicles. The six of them are now dead, buried under flying concrete."

The Wikipedia at
http://en.wikipedia.org/wiki/Fukushi...tor_4_building

has several references related to the incident, two in Japanese i couldnt read.
Ref #208, dated June 7th says four of the soldiers were injured none killed
http://search.japantimes.co.jp/cgi-b...0110607a5.html

It relates a conversation with Col. Shinji Iwakuma the CO of the outfit.

Thanks - at least i have something to go on.
I was checking whether somebody mihgt have been spraying down the pool and it sounds like they hadn't yet got started.

I have a zillion of these loose ends floating around my alleged mind and am tracking them down one at a time.

thanks for the help. i wasnt so far off on that memory it seems, and new info has come in since i made the mental note.

old jim

swl

Why could energy only have come from the pond?

NUCENG

Thanks, that clip made my day,n now, what day is it again?

swl

I heard that rumor broadcast by NHK on the day of the explosion at unit 3. The broadcast was in Japanese, so I asked my 'translator' to verify my understanding of the six fatalities and she told me that it sounded like 6 soldiers had died, but that the wording used could also have indicated missing or injured.

I recently read an interview from NHK where the reporter spoke with a lieutenant responsible for 5 other men (for a total of six) who were preparing to start water spraying at unit 3 on the day of the explosion. He described how he was just opening the door of his vehicle when the unit exploded and injured many of his men. I believe he described the injuries as being serious, but that the men had survived. I don't know if his experience is related to the the NHK report of six dead, missing or injured men.

It also should be pointed out that many of the people working at the plant are contractors or soldiers, so if TEPCO say none of their employees have died, that does not indicate that nobody has died. And of course, with history as our guide, TEPCO could also be telling the truth or lying.

joewein

According to this analysis of the hydrogen explosions:
http://tec-sim.de/images/stories/fusfpfail.pdf

the gate is only watertight while some rubber seals around it are inflated by a compressor.

According to this report by Daily Yomiuri Online:
http://www.yomiuri.co.jp/dy/national/T110428006723.htm

the reactor pit was flooded at the time and TEPCO thinks the explosion triggered a leak from the reactor pit to the SFP.

If there's water circulation between the SFP and the reactor pit then the hot spot on the thermal image could well be the location of the RPV, without there having to be any fuel in it.

elektrownik

Yes, but for example, unit 4 sfp is 80-90C from sensor data, from thermography sfp was for example 31C, this is not great computation but we can see that 10C from thermography = 30C from sensor, in some photos difference (Core location temp bigger) was 10C, so it would mean that when sfp was 80-90C, core location ~120C, this is big difference between core and sfp...

joewein

I'm not sure I understand what temperature data you're referring to, but an empty core can't be hotter than 100 deg C, especially when filled with liquid water at atmospheric pressure.

There is no way they could have left the core in there while they were cutting up the old shroud to replace it.

It was scheduled for refueling once the shroud replacement was done, but the fresh fuel for that was still in the fuel pool - the only fuel in the pool not giving off decay heat. That's why the fuel count was revised upward from an initial value of 1331 to over 1500, they remembered that was also there.

tsutsuji

I am not sure if the following statement by the Asahi writer fits very well with the contents of the Japanese Government's report to the IAEA :
Compare with :

Compare also

with :

The Jogan earthquake is presented to the Asahi readership as a problem emerging in February 2011, while the Japanese government tells us that it was raised as early as July 2009.

Asahi's "Behind the myth" series was published in 8 instalments in the Japanese language paper version of Asahi Shinbun. http://www.asahi.com/english/TKY201106100215.html is an English translation of the 8th one published on June 1st. Perhaps it is already becoming a bit outdated as the Japanese report to the IAEA was published on June 8th.

I agree. See also :

htf

The whole story is puzzling! I don't see any reason why they should have fuel in the RPV. But we see these hot spots. If it is water circulating between the RPV and the SFP why do we these delimited hot spots within the circle. Shouldn't the whole circle be an equally warm area? If it is from irradiated parts of the reactor then I can't believe that there is water in the RPV. How could parts get so hot when covered with water?

etudiant

Thank you, Tsutsuji, for the incremental perspectives.

A more complete story of the decisions made and the warnings not heeded gradually emerges.
It will be interesting to see the Japanese community's eventual response.

Bioengineer01

More than warming not heeded, the explanation is different, it is a common regulatory practice, even in the USA of not defining in hard numbers the limits when those are known to be too high due to cost considerations and leaving the decision making to Industry, fully knowing that they will be forced to compromise. The problem with NP is that the final liability is taken by taxpayers, differently from other industries.

Bioengineer01

"TEPCO did the test run of the contaminated water processing facility by Areva at Fukushima I Nuclear Power Plant, and found leaks in more than 10 places."
http://ex-skf.blogspot.com/2011/06/f...as-system.html

Bioengineer01

Reactor 3 Bldg Radiation


Source: TEPCO press conference June 10.

5 TEPCO employees, 4 from affiliate companies entered the reactor building to prepare for nitrogen injection into Containment Vessel. In 30 minutes, surveying ~half the floor, got exposed to 5.88 to 7.98 millisieverts

96 millisieverts/hour radiation at the staircase going down to the basement, at the southwest corner blue print at llink.
http://ex-skf.blogspot.com/2011/06/f...3-bldg_10.html

etudiant

Interesting insight into the regulatory system. Illustrates the process of regulatory capture to perfection.
If imposing the proper standard would kill the project, (as well as the need for the regulators), just fuzz the requirement to what is commercially viable.
Also interesting that the final liability is with the taxpayer no matter what the regulatory structure. Japan has no Price-Anderson Act, but the government is paying compensation for the TEPCO accident anyways.

thehammer2

This story is of precisely zero importance.

In the process and related industries, when a unit is new/repaired/modified/etc., one of the things you do is to run a hydrostatic test with just plain water (or a compatible fluid if water is not compatible with the process going on inside the unit). This test is SUPPOSED to find the leaks and all the little gremlins in the system. You run the test, you fix what you find, and you repeat until you run the test and the system holds. Then, you introduce the process to the system. It's how you ensure that what's supposed to be on the inside stays on the inside and what's supposed to be on the outside stays on the outside.

Nuclear is just a process industry with WAY more rules. This is completely normal in a new unit or process.