# Japan Earthquake: nuclear plants

by gmax137
Tags: earthquake, japan, nuclear
P: 192
 Quote by elektrownik This ? If (as we seen on underwater sfp 4 video) gate is undamaged, there is no other explanation...
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.
P: 296
 Quote by 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.
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...
P: 192
 Quote by elektrownik it would mean that when sfp was 80-90C, core location ~120C, this is big difference between core and sfp...
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.
PF Gold
P: 1,220
 Quote by etudiant Fourth and final section of the Asahi Shimbun report on the Japanese nuclear experience is here: http://www.asahi.com/english/TKY201106100215.html This part of the report deals with the earthquake and tsunami provisions, which were apparently mostly retrofitted after the plants were already built. There is no editorial wrapup, which might have added some local perspective. Overall, a very good series.
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 :
 Both the earthquake and tsunami exceeded levels anticipated by the revised guidelines. http://www.asahi.com/english/TKY201106100215.html
Compare with :

 Incidentally, the Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities finalized in 2006 specifies in "8. Consideration for the event accompanied by an earthquake" that "During the service period of the facilities, safety features in the facilities [must not] be significantly affected even by such a tsunami that could likely to occur on very rare occasions," and the guideline asks for proper design for such a assumed tsunami. IV-139 of http://www.kantei.go.jp/foreign/kan/...ter_iv_all.pdf ([] is my own translation from page IV-111 http://www.kantei.go.jp/jp/topics/20...4-accident.pdf , changing "might not" into "must not")
Compare also

 In February, the subcommittee held discussions on the Jogan Earthquake of 869 http://www.asahi.com/english/TKY201106100215.html
with :

 Regarding this, NISA requested TEPCO at the 33rd Joint Working Group (July 13, 2009) to take into account the Jogan earthquake for evaluating design tsunami height when new knowledge on the tsunami of the Jogan earthquake is obtained. III-31 http://www.kantei.go.jp/foreign/kan/...pter_iii-2.pdf
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.

 Quote by rowmag Obviously TEPCO underestimated the elevation needed to protect against tsunamis, but they did at least consider the issue in advance.

 ...in the application document for establishment permit, subject tsunami source is Chile Earthquake (M9.5 in 1960) and the design basis tsunami water level is 3.1 m. In 2002, TEPCO evaluated (...) assessing Fukushima-oki Earthquake (M7.9 in 1938) (...) and the highest water level of each Unit was set as 5.4 to 5.7 m. According to the evaluation, elevation of Unit 6 sea water pump motor for emergency diesel generator was raised up 20 cm and also that of sea water pump motor for High Pressure Core Spray was raised up 22 cm. III-31 and III-32 http://www.kantei.go.jp/foreign/kan/...pter_iii-2.pdf
P: 57
 Quote by joewein 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.
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?
 PF Gold P: 866 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.
P: 123
 Quote by 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.
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.
 P: 123 "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
 P: 123 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
PF Gold
P: 866
 Quote by 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.
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.
P: 16
 Quote by 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
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.
P: 84
 Quote by Jorge Stolfi I would agree so far, except ......the RPV had been breached several hours earlier....................
No matter Jorge, as long as we are in agreement that there was a path between the RPV and the drywell we have no differences here.

 Quote by Jorge Stolfi 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 is another trivial divergence, but I was under the impression that the original GE design had a round hole at the top and at Fukushima they had used an octagonal design - I probably got this from T-Cups' post #649 on page 41.

There were a number of design considerations for the secondary containment structure; it was meant to shield radiation, but it was also meant to be able to ward off at least medium sized aircraft or debris from tornadoes etc.

Another of it's qualities obviously was to seal the drywell from the rest of the building (which was at a negative pressure.)

In an earlier post it was disclosed that a GE mark I had been subjected to a real life pressure test and it had leaked at something like 60 psi. The report or the post about that implied that it had "failed" at 60 psi.

When I said that the Fukushima design may have held to 125 psi I was trying to avoid that apparently controversial subject, but it appears that I found another aspect to be controversial about.

Sorry for the lack of detail.

 Quote by Jorge Stolfi 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.
This point lies at the heart of the matter IMO and I would love for one of our forum chemists (or physicists) to chime in with an opinion.

When I describe "flashovers" I believe I am describing the exact process described by "(oxygen)should have been promptly consumed by the excess hydrogen"

 Quote by Jorge Stolfi 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.
What I was attempting to describe is a process whereby hydrogen had been seeping out of containment and was building up in the building above before any "massive leak of (hydrogen laden) steam" occurred.

 Quote by Jorge Stolfi 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.
Hydrogen is lighter than air, it would not flow "down."

 Quote by Jorge Stolfi 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.
But steam had been accumulating above the trough also. And I had hoped to be painting a picture of hydrogen accumulating in the trough before the explosion.

 Quote by Jorge Stolfi 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.
Again, I was just trying to head off what I see as an extraneous argument.
I probably should not have mentioned the headbolts.

 Quote by Jorge Stolfi But for this scenario we need a path for the steam to get from the drywell to the refueling pit.
I left off before the explosion had progressed that far.

 Quote by Jorge Stolfi 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.
Well, we agreed on something!
P: 74
Quote by Quim
 Quote by Jorge Stolfi 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.
Well, we agreed on something!
Maybe you are both wrong?

These seals are not watertight, as Christian Mueller explained in the document Joe linked at in his post?
Unclear yet is, how much water could leak when the inflated rubber seals lost their pressure when the compressor's electric supply failed?

 Quote by 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?
Maybe because water cools down in the RPV, compressing/getting more dense, and so the RPV as a heat sink sucks up the hot water circulating over from the SFP?
Sort like the gulf stream going north, being sucked to there by the cooling-down and falling water masses there?

Maybe there are some "interesting water dynamics" in the other reactors' pools also?

(Just the 2 cents of an annoying layman...)
 P: 57 Well, but why are these spots in the RPV the hottest points on the whole image? If the RPV is full of water this would mean that there are powerful heat sources located at this place that can maintain a temperature gradient. Can irradiated reactor parts generate so much heat? I am not an expert but I hardly can imagine thas. Or is the explanation quite simple: was the picture taken before the gates started leaking?
 Sci Advisor PF Gold P: 3,738 So are we looking down into the vessel with that IR photo, or are we seeing hot water & steam at surface of pool?
 P: 68 http://ex-skf.blogspot.com/ "In the first photo, you can see the pipe that's bent. That was the pipe that TEPCO was counting on to connect the cooling system for the Spent Fuel Pool, according to Jiji News (6/11/2011). The cooling system for the Reactor 4 Spent Fuel Pool won't be operational at least until July, as TEPCO will have to either fix the pipe or come up with alternative connection. The second photo shows a mess of broken pipes, concrete bits and equipments. Any mechanics, engineers, who want to dissect the photo? The Reactor 4 was in a scheduled maintenance when the earthquake hit on March 11. All the fuel rods had been moved to the Spent Fuel Pool. The workers were in the process of replacing the stainless-steel shroud of the Reactor Pressure Vessel at the time of the earthquake." That means: The RPV was empty, no Water in the RPV at the time of the Earthquake
P: 84
 Quote by htf Well, but why are these spots in the RPV the hottest points on the whole image? If the RPV is full of water this would mean that there are powerful heat sources located at this place that can maintain a temperature gradient. Can irradiated reactor parts generate so much heat? I am not an expert but I hardly can imagine thas. Or is the explanation quite simple: was the picture taken before the gates started leaking?
As I understand it, unless you have calibrated the infrared camera to some standard of sensitivity and heat spectrum a photograph like that one is meaningless.
P: 238
 Quote by triumph61 http://ex-skf.blogspot.com/ "In the first photo, you can see the pipe that's bent. That was the pipe that TEPCO was counting on to connect the cooling system for the Spent Fuel Pool, according to Jiji News (6/11/2011). The cooling system for the Reactor 4 Spent Fuel Pool won't be operational at least until July, as TEPCO will have to either fix the pipe or come up with alternative connection. The second photo shows a mess of broken pipes, concrete bits and equipments. Any mechanics, engineers, who want to dissect the photo? The Reactor 4 was in a scheduled maintenance when the earthquake hit on March 11. All the fuel rods had been moved to the Spent Fuel Pool. The workers were in the process of replacing the stainless-steel shroud of the Reactor Pressure Vessel at the time of the earthquake." That means: The RPV was empty, no Water in the RPV at the time of the Earthquake
But there could be debris in the reactor.

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