Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[AntonL]

Yes. TMI-2 successfully contained the hydrogen. Some plants have hydrogen recombiners to safely control of the combustion hydrogen.

and can these cope with the vast amount of hydrogen produced in an emergency situation? Why not just flood the building with CO2 in an emergency?

 

[Astronuc]

I'm a humanities guy but I've been doing some reading and have some questions that maybe posters could answer.

1. I heard that the quick path to cold shutdown at Daiini was restoration of grid power then use of its normal pump systems. I heard that grid power was restored to Daiichi but none of the plant's primary and backup feedwater and injection systems are back up or seem to have any chance. Does anyone know why not? Could every single pumping system be disabled? Doesn't that seem unlikely?

It appears that the damage at the Daiichi site is much more extensive than at Daini. The damage seems to be due to a combination of seismic activity (?) and tsunami.

2. Is there absolutely no scenario in which the reactor vessel or drywell could be breached? Some in media insist on that. Could someone put some figures to it?
2A. Temperature angle. I read that the melting point of steel is 2800 Faren and zircaloy 2200 F. Also that concrete starts to crumble at 1800 F. Does that mean there is no way a molten core could reach and sustain a temp of > 2800 F? If it could, why couldn't it melt through the vessel?

Melting pt of UO2 2800°C (5070°F)
Melting pt of Zr-2 1850°C (3362°F)
Melting pt of SS304 1400-1455°C (2550-2650°F)

The oxidation of Zr-2 takes places at temperatures less than melting. A 'line in the sand' number is 1204°C (2200°F). However, it is expected that the cladding won't remain at that temperature for more than so many seconds. As the temperature increases, the oxidation rate increases exponentially.

At the base of a BWR fuel assembly is a cast steel tie-plate or nozzle. Under each fuel assembly is a steel pad which supports 4 fuel assemblies. The pad is supported by a large steel support plate. Under the support plate in a BWR, are various pieces of hardware supporting the control rod drive mechanism.

The core is inside a steel pressure vessel, and the pressure vessel sits in a steel-reinforced concrete chamber. It is expected that the damage fuel would be retained in the core supported by the various steel components. They should have the pressure vessel and containment flooded with water.

With the control rods interspersed between the fuel assemblies, the reactor is not expected to regain criticality.

2B. Pressure angle. Seems like pressure must be able to present a problem and that is the reason for the current "feed and bleed" method. Is there a critical pressure level for the vessel? What has to happen for that level to be reached (i.e., rods totally exposed for x hours with no water?)?

The critical pressure is based on the weakest part that would give way. The design pressure for containment is 4 atm based on what's been published so far. Usually there is some margin in design, so it could be a lot higher. In FK-I, a pressure of approximately 8.4 atm was recorded, and as far as we know, it's primary containment held. Not sure about the other units.

3. Spent fuel rods. If a group of them get totally uncovered by cooling water, what could happen?
3A. Everyone agrees the rods could heat up, then zircaloy cladding melt, then what? If zircaloy melts at 2200 F, wouldn't the concrete under it start to at crumble at 1800 F? Could they sponteously combust, have a conventional fire, that could disperse radioactive material?
3B. I read different things on whether these rods could go "critical", which I understand to means "to restart fission" (but not explode like a bomb). Most in media say "no way" but TEPCO just said it can't rule it out in the case of Unit 4, and it seems like it may have already. See these articles. So can they go "critical" or not?
3C. If fresh fission is possible, that's really bad bc it is outside of containment. Freshly fissioned uranium could disperse by fire or explosion (say by hydrogen).

The spent fuel pools would not go critical, especially if water is removed. The concern is that the fuel rods would get too hot, the Zr-2 cladding would breach and leak radioactive Xe and Kr gases, and maybe some I, Br, or worse the Zr-2 rapidly oxidizes (some are concerned about burning) which would release those aforementioned elements and Cs, and other volatile radioisotopes. That would add to the contamination at the unit, in the plant, but the gases and some volatiles, perhaps some small particulates would be carried into the atmosphere where they are carried on the wind.

I pray for the people of Japan and especially the heros at Daiichi who are sacrificing themselves.

We all do.

 

[TCups]

The spent fuel pools would not go critical, especially if water is removed. The concern is that the fuel rods would get too hot, the Zr-2 cladding would breach and leak radioactive Xe and Kr gases, and maybe some I, Br, or worse the Zr-2 rapidly oxidizes (some are concerned about burning) which would release those aforementioned elements and Cs, and other volatile radioisotopes. That would add to the contamination at the unit, in the plant, but the gases and some volatiles, perhaps some small particulates would be carried into the atmosphere where they are carried on the wind.

We all do.

Astronuc:

IF the rods in the pool were perhaps not fully spent. . . for example, Unit 4 were shut down for maintenance, and all the fuel rod assemblies removed from the reactor core (and therefore removed from the primary containment) and IF, instead, they were in the SFP outside of the primary containment . . .

THEN, could loss of circulating coolant surrounding the rods in the SFP result in heat sufficient to boil off the remaining water, oxidize the Zr-2 cladding, generate steam + hydrogen + fires, burn through the floor and sidewall of the "dry" SFP, and "blow out" the side of the Unit 4 building?

Look where the photo (I hope it was a remote robotic taking the picture) is centered. What do you think they were assessing? Does it look to you like there is a "slag-like" tongue of something hanging out of a relatively square hole in roughly the location that might correspond to the SFP, and that a sideways blast has taken out some of the structures external to the building as well as the roof of the building?

http://www.abc.net.au/reslib/201103/r735227_5964756.jpg

The damage from explosion at Unit 4 is fundamentally different than that at Unit 3, where all the structures seem to be blown out away from the primary containment.

 

[Astronuc]

Astronuc:

IF the rods in the pool were perhaps not fully spent. . . for example, Unit 4 were shut down for maintenance, and all the fuel rod assemblies removed from the reactor core (and therefore removed from the primary containment) and IF, instead, they were in the SFP outside of the primary containment . . .

THEN, could loss of circulating coolant surrounding the rods in the SFP result in heat sufficient to boil off the remaining water, oxidize the Zr-2 cladding, generate steam + hydrogen + fires, burn through the floor and sidewall of the "dry" SFP, and "blow out" the side of the Unit 4 building?

The spent fuel pool (3) is outside of primary containment. It sits on top of the concrete structure. Each fuel assembly sits in a square tube in a rack. The rack has neutron absorber material to prevent criticality. The water covering the fuel provides cooling and shielding. The concern is that the water evaporates, and exposes the fuel to air. The oxgyen in the air then oxidizes the Zr-2 cladding, which produces hydrogen. The question then is what caused the fire at unit 4? If it was hydrogen deflagration (not an explosion) - then what is the source of the hydrogen? If there is no fuel in the reactor vessel - it may be that it is coming from the SFP, which has already dried out. Could there have been other sources of hydrogen? Perhaps if the plant uses hydrogen water chemistry. Could there have been other sources of fuel? If so, what?

If fuel is taken from the spent fuel pool and shipped out of the reactor building, it would be do so in a shielded cask, which is shown in the picture. The cask contains several assemblies (~28 perhaps), and it is filled with He for cooling. Even so, the casks can get pretty hot. Smaller shipping casks, which hold fewer assemblies, do not get as hot as storage casks. The oldest, coolest fuel is put in storage casks if there is insufficient room to store all discharged fuel + a full core's worth.

Look where the photo (I hope it was a remote robotic taking the picture) is centered. What do you think they were assessing? Does it look to you like there is a "slag-like" tongue of something hanging out of a relatively square hole in roughly the location that might correspond to the SFP, and that a sideways blast has taken out some of the structures external to the building as well as the roof of the building?

http://www.abc.net.au/reslib/201103/r735227_5964756.jpg

The damage from explosion at Unit 4 is fundamentally different than that at Unit 3, where all the structures seem to be blown out away from the primary containment.

Units 1 and 3 had significant explosions, whereas unit 4 may have had a smaller explosion or fire. Or, was it damaged by the explosion and fire of unit 3?

I expect they are trying to assess the damage to unit 4 and how they might get water to the spent fuel pool.

 

[Borek]

If memory serves me well unit 4 fire was explained as burning leaking oil - either lubricant or hydraulic. I can't locate source right now, besides, I read it in Polish.

 

[Astronuc]

That Nuclear power plants have heated swimming pools (spent fuel storage tanks)
and that the swimming pool heaters can start a meltdown process or catch fire
is news to me. Fukoshima I no 4 reactor fuel rods are all in this indoor swimming pool!

Any discussion on containment primary or secondary is now superfluous

What sort of safety is this!
And that the plant was designed by USA's General Electric the question to ask now is:
How many USA nuclear power plants have heated swimming pools?

The spent fuel pools are actually cooled. They are designed for interim storage of discharged fuel, and they are heated by the decay heat from the spent fuel. Every plant has them. In Mk I containment systems, they are at top of the reactor building under the metal housing atop the concrete structure. More modern plants have SFP locates in separate structure adjacent to the reactor building.

With respect to the spent fuel pool, clearly the Mk I containment is inadequate in the Fukushima event.

 

[Astronuc]

If memory serves me well unit 4 fire was explained as burning leaking oil - either lubricant or hydraulic. I can't locate source right now, besides, I read it in Polish.

I have heard the same - that the fire(s) at unit 4 came from a fuel source not related to the SFP. However, the situation seems to be evolving (rapidly deteriorating according to some).

 

[TCups]

If memory serves me well unit 4 fire was explained as burning leaking oil - either lubricant or hydraulic. I can't locate source right now, besides, I read it in Polish.

I read that, too, but not in Polish -- and I can't remember if it was the 1st or 2nd (recurrent) fire that was attributed to the oil fire. Nonetheless, there is that big, square hole, there was an explosion, and there have been reports of boiling water in the SFP with apparent heroic but aborted attempts, due to radiation levels, to dump water on the SFP via a helicopter

Excerpt, WSJ:
TOKYO—Efforts to extinguish smoldering spent fuel were thwarted Wednesday, after high radiation levels above forced the cancellation of a plan to dump water from a helicopter on the power plant at the center of Japan's escalating nuclear crisis.

cite:
http://online.wsj.com/article/SB10001424052748703899704576203850892933990.html

Taking a closer look into the square hole, I wonder if portions of exposed spent fuel rods might be glowing red?

 

[Borek]

Perhaps worth of noting: both Onagawa and Tokai NPPs, while also hit by the earthquake, did not develop into a nightmare.

 

[TCups]

Well, here is my "radiologist" interpretation of this image

PS: Borek - someone posted this reference a day or so earlier. Look down the list and check out the "Spent Fuel Integrity" status. Neither "no info" nor "temperature rising" are that reassuring to me. Also, note that seawater injection into the reactor vessels of units 4, 5, 6 was "not necessary" -- because perhaps the fuel rods weren't in the reactor vessel? Don't fuel rods, once they have "reacted", wherever they are, and in whatever state they are in (spent, or otherwise) require ongoing cooling? I believe so.

http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300189582P.pdf

 

[Drachma]

The horror-show continues:

"Chief Cabinet Secretary Yukio Edano told reporters the assistance of the United State military is now being considered, but that it might be too risky to use helicopters to drop water on the damaged reactors to try to keep cool the radioactive fuel rods.



The top government spokesman says the containment vessel of Reactor Three at the Fukushima nuclear power plant may have cracked. He says it is highly probably that this may be the source of a cloud of white smoke being seen in video images relayed from a helicopter 30 kilometers away from the crippled nuclear facility.



Japanese officials acknowledge they are being reduced to desperate measures in an attempt to stop what may become a significant and continuing spread of radiation into the atmosphere from the crippled nuclear power generating facility.



Earlier in the day, Tokyo Electric Power Company spokesman Hajimi Motojuku acknowledged the possibility that spent fuel rods at the number four reactor at the same plant could again enter a state of a nuclear chain reaction.



The spokesman says a fire was again spotted for about 30 minutes Wednesday morning coming from the reactor's spent fuel cooling pond. He says the cooling pond water may be boiling off, exposing the rods again to the atmosphere.



That would allow them again emit radioactive substances. The utility is now considering using helicopters to spray boric acid on the rods.



The fire was originally spotted Tuesday, apparently triggered by a hydrogen explosion. But Tokyo Electric said they halted fire-fighting operations late in the day because workers believed the flames had been extinguished.



Radiation levels are so dangerous on the ground at the Fukushima plant that workers have had to give up trying to pour water into the cooling pool and all of the facilities' 800 workers have now evacuated the site."

Sounds like everything is under control.

 

[Angry Citizen]

That's both incredibly old (the workers have long since returned) and incredibly unsourced.

 

[AntonL]

From BBC:
1520: (GMT) The IAEA says the Japanese authorities "have reported concerns about the condition of the spent nuclear fuel pool at Fukushima Daiichi Unit 3 and Unit 4". The pools are where the still-radioactive fuel rods are kept after they have completed their useful life in the reactor.

and
1525:(GMT) The EU's energy chief Guenther Oettinger has said that in the coming hours "there could be further catastrophic events, which could pose a threat to the lives of people on the island". He told the European Parliament the Fukushima nuclear site was "effectively out of control". "The cooling systems did not work, and as a result we are somewhere between a disaster and a major disaster."

 

[turbo]

The helicopter air-drop is not going to help #4 SFP.

TEPCO was planning to battle the fire and provide additional water to cool used nuclear fuel with water dumped from helicopters, but abandoned the plan because a hole in the building's roof is not in close proximity of the used fuel pool.

http://nei.cachefly.net/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/

 

[TCups]

The horror-show continues:

"Chief Cabinet Secretary Yukio Edano told reporters the assistance of the United State military is now being considered, but that it might be too risky to use helicopters to drop water on the damaged reactors to try to keep cool the radioactive fuel rods.



The top government spokesman says the containment vessel of Reactor Three at the Fukushima nuclear power plant may have cracked. He says it is highly probably that this may be the source of a cloud of white smoke being seen in video images relayed from a helicopter 30 kilometers away from the crippled nuclear facility.



Japanese officials acknowledge they are being reduced to desperate measures in an attempt to stop what may become a significant and continuing spread of radiation into the atmosphere from the crippled nuclear power generating facility.



Earlier in the day, Tokyo Electric Power Company spokesman Hajimi Motojuku acknowledged the possibility that spent fuel rods at the number four reactor at the same plant could again enter a state of a nuclear chain reaction.



The spokesman says a fire was again spotted for about 30 minutes Wednesday morning coming from the reactor's spent fuel cooling pond. He says the cooling pond water may be boiling off, exposing the rods again to the atmosphere.



That would allow them again emit radioactive substances. The utility is now considering using helicopters to spray boric acid on the rods.



The fire was originally spotted Tuesday, apparently triggered by a hydrogen explosion. But Tokyo Electric said they halted fire-fighting operations late in the day because workers believed the flames had been extinguished.



Radiation levels are so dangerous on the ground at the Fukushima plant that workers have had to give up trying to pour water into the cooling pool and all of the facilities' 800 workers have now evacuated the site."

Sounds like everything is under control.

All of that said, including the sarcasm, this is still nowhere near the level of the Chernobyl disaster where a critical graphite pile with no primary containment exploded and burned for days because of gross incompetence.

It seems to me that there were no fundamental operator errors immediately apparent in Japan's "event" -- the 40-year old systems worked as well as they could for as long as they could under the circumstances. Pretty sure someone will have to be found to blame, eventually, though. They always are.

In retrospect, the original GE design with storage of spent fuel outside of a primary containment system seems very risky for a power plant on an active geologic fault. Weren't there some skilled engineer types that have been saying just that? And let's not forget that the geologic fault, quake, and tsunami were the "crisis" here and the nuclear "accident" was only one of the disastrous results.

Undoubtedly, history will prove that the loss of life from the quake, tsunami, and subsequent lack of heat and shelter to a population with no power will far exceed any loss of life from the nuclear "accident". Or in other words, "stuff happens".

One of the greatest tragedies will be that the nuclear power industry and engineers, who, I feel confident, will learn from and design better systems that would be safe even with a 9.0 quake and massive tsunami, will be shouted down by the hype and hysteria that follows all of this. And poor Japan, with no oil, no coal, and for now in many places, no power, will desperately need to resume nuclear power production in order to recover.

Just as the news media now seems amazed at the lack of panic and looting in Japan, I think they will also be amazed at how quickly Japan rebuilds, including, new nuclear power plants. Just my opinion

 

[Drachma]

Dear Angry Citizen:

I am not anti-nuke as you say. I just don't appreciate a white-wash and delusion. It is always more informative to look at the actions of 'officials' and not their words. It seems that many posters on this site suffer from normalcy bias, and so attack me for suggesting that the picture is not as rosy as they might like to believe.

For crazyisraeli:

#1 Japanese Prime Minister Naoto Kan is urging all people living within 30 kilometers of the Fukushima Dai-ichi nuclear facility to stay indoors.

#2 Andre-Claude Lacoste, the head of France’s Nuclear Safety Authority, says that the containment vessel surrounding the No. 2 reactor at Japan’s Fukushima Dai-ichi nuclear complex is “ HYPERLINK "http://www.asiaone.com/News/Latest+News/Asia/Story/A1Story20110315-268286.html" no longer sealed“.

#3 Radiation levels in Tokyo are already* HYPERLINK "[PLAIN]http://www.haaretz.com/news/international/rising-radiation-triggers-panic-and-evacuations-in-tokyo-1.349301" [/URL] 10 times above normal levels.

#4 HYPERLINK "http://www.reuters.com/article/2011/03/15/us-japan-quake-idUSTRE72A0SS20110315" Reuters is reporting that some residents of Tokyo are already starting to flee the city.

#5 Radiation levels in one city north of Tokyo, Utsunomiya, were recently reported to be* HYPERLINK "http://www.stratfor.com/analysis/20110315-red-alert-radiation-rising-and-heading-south-japan" 33 times above normal levels.

#6 Radiation levels in the city of Saitama have been reported to be* HYPERLINK "[PLAIN][PLAIN]http://www.telegraph.co.uk/news/worldnews/asia/japan/8382504/Japan-earthquake-panic-in-Tokyo-as-radiation-spreads.html" [/URL][/URL] 40 timesabove normal levels.

#7 According to Japanese Prime Minister Naoto Kan, the “ HYPERLINK "[PLAIN]http://www.haaretz.com/news/international/rising-radiation-triggers-panic-and-evacuations-in-tokyo-1.349301" [/URL] possibility of further radioactive leakage is heightening.”

#8 The Japanese government is admitting that radiation levels near the Fukushima Dai-ichi complex* HYPERLINK "[PLAIN][PLAIN]http://www.telegraph.co.uk/news/worldnews/asia/japan/8382504/Japan-earthquake-panic-in-Tokyo-as-radiation-spreads.html" [/URL][/URL] are very harmful to human health.

#9 According to the World Nuclear Association, exposure to over 100 millisieverts of radiation a year can lead to cancer.* At this point the level of radiation being measured right outside the number 4 reactor at the Fukushima Dai-ichi complex is* HYPERLINK "http://www.cnbc.com/id/42083931" 400 millisieverts*per hour.

#10 A U.S. Navy crew that was assisting in relief efforts was exposed to a month’s worth of nuclear radiation* HYPERLINK "http://www.dailymail.co.uk/news/article-1366341/Japan-tsumani-earthquake-America-nuclear-accident-radiation-alert.html" in just a single hour.

#11 According to the U.S. Navy, low levels of radiation* HYPERLINK "http://www.stripes.com/news/pacific/earthquake-disaster-in-japan/u-s-navy-low-level-radiation-detected-at-some-tokyo-area-bases-1.137754" have been detected at their bases in Yokosuka and Atsugi.

#12 The USS Ronald Reagan recently detected* HYPERLINK "http://www.thesun.co.uk/sol/homepag...uke-cloud-crisis-after-Japan-earthquake.html" significant levels of radiation 100 miles off the Japanese coast.

#13 The operator of the Fukushima Dai-ichi complex has pulled out* HYPERLINK "[PLAIN]http://www.haaretz.com/news/international/rising-radiation-triggers-panic-and-evacuations-in-tokyo-1.349301" [/URL] 750 of the 800 workers that were working at the facility.

#14 The French embassy in Tokyo is advising French citizens* HYPERLINK "[PLAIN][PLAIN]http://www.telegraph.co.uk/news/worldnews/asia/japan/8382504/Japan-earthquake-panic-in-Tokyo-as-radiation-spreads.html" [/URL][/URL] to leave the city.

#15 The German embassy in Tokyo is advising all German citizens* HYPERLINK "[PLAIN][PLAIN]http://www.telegraph.co.uk/news/worldnews/asia/japan/8382504/Japan-earthquake-panic-in-Tokyo-as-radiation-spreads.html" [/URL][/URL] to leave the country entirely.

#16 German technology company SAP* HYPERLINK "http://www.cnbc.com/id/42083931" is evacuating their offices in Tokyo.

#17 Austria has announced that it is moving its embassy* HYPERLINK "http://austrianindependent.com/news/General_News/2011-03-15/6727/Austrians_should_depart_Tokyo,_ministry_says" from Tokyo to Osaka due to fears about the radiation.

#18 Finland is urging* HYPERLINK "http://www.helsinkitimes.fi/htimes/domestic-news/general/14604-foreign-ministry-urges-families-with-children-to-leave-japan-.html" all of their citizens to leave Tokyo.

#19 The Czech military is sending planes to Japan* HYPERLINK "http://www.winnipegfreepress.com/world/breakingnews/czech-military-says-it-sent-planes-to-japan-to-evacuate-czech-philharmonic-118003499.html" specifically to evacuate the Czech Philharmonic Orchestra.

#20 Air China is* HYPERLINK "[PLAIN][PLAIN]http://www.telegraph.co.uk/news/worldnews/asia/japan/8382504/Japan-earthquake-panic-in-Tokyo-as-radiation-spreads.html" [/URL][/URL] canceling many flights to Tokyo.

#21 The Chinese Embassy has announced that it will be* HYPERLINK "http://www.washingtonpost.com/business/china-to-pull-citizens-from-ne-japan-other-foreigners-ponder-exit-amid-nuclear-crisis/2011/03/15/ABfGEjW_story.html" evacuating all Chinese citizens from the Miyagi, Fukushima, Ibaraki and Iwate prefectures.

#22 Russia is making preparations to evacuate civilians and military units HYPERLINK "http://online.wsj.com/article/SB10001424052748704662604576202003408046120.html" from the Kuril Islands.

#23 Physicist Frank von Hippel recently told the New York Times* HYPERLINK "http://www.dailymail.co.uk/news/article-1366341/Japan-tsumani-earthquake-America-nuclear-accident-radiation-alert.html" the following about this disaster: “It’s way past Three Mile Island already”.

#24 The president of France’s nuclear safety authority says that this crisis* HYPERLINK "http://www.cnn.com/2011/WORLD/asiapcf/03/15/japan.nuclear/" is now almost as bad as Chernobyl was….
“It’s clear we are at Level 6, that’s to say we’re at a level in between what happened at Three Mile Island and Chernobyl.”

#25 There have been reports of extremely high radiation at another nuclear facility in Japan.* It has been reported that at the Onagawa nuclear plant radiation that is* HYPERLINK "http://www.whatreallyhappened.org/content/emergency-onagawa-nuclear-plant-radiation-700-times-over-normal" \l "axzz1GibYbo4M" 700 times the normal level was detected at one point.

#26 One anonymous senior nuclear industry executive told* HYPERLINK "http://timesofindia.indiatimes.com/world/rest-of-world/Emergency-cooling-effort-failing-at-Japanese-reactor-deepening-crisis/articleshow/7705671.cms" The Times Of India that Japanese power industry managers are “basically in a full-scale panic” and that “they don’t know what to do”.

#27 It is also being reported that there were over* HYPERLINK "http://www.infowars.com/alert-fukushima-coverup-40-years-of-spent-nuclear-rods-blown-sky-high/" 600,000 spent fuel rods stored at the Fukushima Dai-ichi complex.* Most of these rods were apparently stored* HYPERLINK "http://www.infowars.com/alert-fukushima-coverup-40-years-of-spent-nuclear-rods-blown-sky-high/" near the top of the 6 reactor buildings.*

What does your intuition tell you about the situation Mr. Crazy. What colour-code would you put on this disaster scenario? All green?

Cheers.

 

[promecheng]

Update from MIT Nuclear Science & Engineering student blog: http://mitnse.com/

 

[Angry Citizen]

#3 Radiation levels in Tokyo are already* HYPERLINK "http://www.haaretz.com/news/international/rising-radiation-triggers-panic-and-evacuations-in-tokyo-1.349301" 10 times above normal levels.

Well this is inaccurate. Here's a graph regarding the radiation count in Tokyo: http://park18.wakwak.com/~weather/geiger_index.html

As you can see, it's only about 20-30% higher.

 

[Astronuc]

One of the greatest tragedies will be that the nuclear power industry and engineers, who, I feel confident, will learn from and design better systems that would be safe even with a 9.0 quake and massive tsunami, will be shouted down by the hype and hysteria that follows all of this. And poor Japan, with no oil, no coal, and for now in many places, no power, will desperately need to resume nuclear power production in order to recover.

We already have better containment designs. The Mk I containment was superceded by Mk II, which was superceded by Mk III, and those are superceded by more robust containments for ABWR and ESBWR. All containments will be reviewed, especially the existing Mk I, and I would expect authorities would consider some kind of retrofitting.

In Mk III, the spent fuel is in a separate facility.

The plant site characteristics are plant specific. All sites now and in future will have to ensure that the emergency cooling systems are more robust - NO FAIL!

 

[TCups]

We already have better containment designs. The Mk I containment was superceded by Mk II, which was superceded by Mk III, and those are superceded by more robust containments for ABWR and ESBWR. All containments will be reviewed, especially the existing Mk I, and I would expect authorities would consider some kind of retrofitting.

In Mk III, the spent fuel is in a separate facility.

The plant site characteristics are plant specific. All sites now and in future will have to ensure that the emergency cooling systems are more robust - NO FAIL!

Astronuc:

Have you seen these:

http://www.nirs.org/reactorwatch/accidents/6-1_powerpoint.pdf

http://www.infowars.com/alert-fukushima-coverup-40-years-of-spent-nuclear-rods-blown-sky-high/

seems like an awfully lot of spent fuel is at risk.

 

[PRDan4th]

Can't we design these plants be to be "fail-safe"? That is in any major interruption in outside power or people can the plants control their own shut-down and cooling maintenance using only gravity or waste heat/steam from the decay of spent fuel. Assume all people and services external to the facility are unavailable. As long as the structural design does its job and contains the radioactive exposure, just shut down automatically and provide for self-cooling without staff or external power.

 

[Reno Deano]

Well this is inaccurate. Here's a graph regarding the radiation count in Tokyo: http://park18.wakwak.com/~weather/geiger_index.html

As you can see, it's only about 20-30% higher.

The graph is accurate in that it only show a meters relative response to who knows what radiation source or type. Even though they indicate that so many CPM = so many Sieverts (cellular dose equivalent), using a GM detector without stating the its specific calibration characteristics would only give you Grays (absorbed dose in material). Gives a good time line on changes in detector response to something.

 

[AntonL]

It seems to me that there were no fundamental operator errors immediately apparent in Japan's "event" -- the 40-year old systems worked as well as they could for as long as they could under the circumstances. Pretty sure someone will have to be found to blame, eventually, though. They always are.

The stations architects "Ebesco" will be the ones to blame - the station withstood the earthquake but being built to low allowed the Tsunami wave to destroy the pump intake, diesel standby power etc and that such high Tsunamis are possible was common knowledge when the station was designed

On October 28, 1707, during the Hōei era, an 8.4 earthquake and tsunami 25.7-meter-high struck at the Kochi Prefecture

An undersea earthquake of estimated magnitude 7.4 occurred near Yaeyama Islands in Okinawa, Japan on 4 April 1771 at about 8 A.M.. The earthquake is not believed to have directly resulted in any deaths, but a resulting tsunami is thought to have killed about 12,000 people, (9313 on the Yaeyama Islands and 2548 on Miyako Islands according to one source [18]). Estimates of the highest seawater runup on Ishigaki Island, range between 30 meters and 85.4 meters.

The Ansei Quake which hit the south coast of Japan, was actually set of 3 quakes, two magnitude 8.4 quakes and a 7.4 quake all in 3 days.
The first on Nov 4, 1854 near what is today Aichi Prefecture and Shizuoka Prefecture with tsunami.
It was followed by another 8.4 the next day in Wakayama Prefecture, Earthquake generated a maximum wave of 28 meters at Kochi, Japan, and the earthquake that tsunami killed 3,000 people.

On 15 June 1896, at around 19:36 local time, a large undersea earthquake off the Sanriku coast of northeastern Honshū, Japan, triggered tsunami waves which struck the coast about half an hour later. Although the earthquake itself is not thought to have resulted in any fatalities, the waves, which reached a height of 100 feet,

The Great Kanto Earthquake, which occurred in eastern Japan on 1 September 1923, and devastated Tokyo, Yokohama and the surrounding areas, caused tsunamis which struck the Shonan coast, Boso Peninsula, Izu Islands and the east coast of Izu Peninsula, within minutes in some cases. In Atami, waves reaching 12 meters were recorded.

With these known facts one does not build a nuclear power station less than 30 or 40 metres above sea level - If Fukushima was built that high above sea level then we would not have this discussion today and the nuke industry could praise itself how safe it is, and remember the west coast of USA can be hit by a similar tsunami.

I have changed overnight from a nuclear tolerant person to a anti-nuke vulture as it has been proven now that most nuke stations are actually unsafe - after 40 years the luck ran out.

 

[andyr]

It seems to me that there were no fundamental operator errors immediately apparent in Japan's "event" -- the 40-year old systems worked as well as they could for as long as they could under the circumstances. Pretty sure someone will have to be found to blame, eventually, though. They always are.

In retrospect, the original GE design with storage of spent fuel outside of a primary containment system seems very risky for a power plant on an active geologic fault. Weren't there some skilled engineer types that have been saying just that? And let's not forget that the geologic fault, quake, and tsunami were the "crisis" here and the nuclear "accident" was only one of the disastrous results.

Undoubtedly, history will prove that the loss of life from the quake, tsunami, and subsequent lack of heat and shelter to a population with no power will far exceed any loss of life from the nuclear "accident". Or in other words, "stuff happens".

This is where the flaws in anti-nuclear logic show. Why are people not looking for the person that allowed the building of civilisation near the coastline? That has proved to be of deadly consequence, far more so than all nuclear plant incidents. Of course you have the trade-off of freedom and happiness vs. safety.

The cities will be rebuilt, and be vulnerable to the same event again whereas the nuclear power industry will use this event has a chance to review and improve their emergency systems even further to the point where they will still be able to operate when 1 in 1000 year disasters occur.

I have belief that the Japanese will see the facts on this one, and that it was a tsunami that caused all this, not the power plant.

 

[Reno Deano]

Can't we design these plants be to be "fail-safe"? That is in any major interruption in outside power or people can the plants control their own shut-down and cooling maintenance using only gravity or waste heat/steam from the decay of spent fuel. Assume all people and services external to the facility are unavailable. As long as the structural design does its job and contains the radioactive exposure, just shut down automatically and provide for self-cooling without staff or external power.

"Fail-safe"...can you describe a major technological and complicated human engineered system that is "fail-safe", so I can further understand you question?

The newest and most modern commercial nuclear power plants on the drawing boards and some are already approved for construction (see NRC website) are as close to "fail-safe" as human engineering will get us. Japan is or has built one of these advanced PWRs that the US of A designed and the NRC approved.

 

[uart]

Just a quick question about the quake damage versus the tsunami damage. Would it be fair to say that if it were only the quake damage and without the following tsunami damage that even these 40 yo reactors would have achieved a relatively safe shutdown? From what I've read that seems to be the case.

Although it might be impossible to site a reactor in Japan without some risk of massive earthquake, surely it is possible to situate them out of reach of any likely tsunami. Even if pumping water was more costly it would still be possible right? Japan has a long history of tsunamis, so why would they put a nuclear power station where it could get hit by one?EDIT. I hadn't seen this post before I posted this (thread is moving fast and my internet is slow)

The stations architects "Ebesco" will be the ones to blame - the station withstood the earthquake but being built to low allowed the Tsunami wave to destroy the pump intake, diesel standby power etc and that such high Tsunamis are possible was common knowledge when the station was designed

Yes Anton, this is exactly what I was thinking.

 

[andyr]

The stations architects "Ebesco" will be the ones to blame - the station withstood the earthquake but being built to low allowed the Tsunami wave to destroy the pump intake, diesel standby power etc and that such high Tsunamis are possible was common knowledge when the station was designed

Going off topic slightly: If they knew about tsunamis, why build their homes on the coast? This is not a case of a power plant being the only thing built in a dangerous place. Peoples homes were built in the affected areas too. Clearly a lot of people didn't know about the tsunami risks being so great, else they wouldn't live there right? If they didn't live there the plant also wouldn't be there.

 

[russ_watters]

I see some of this has been answered so I apologize for the rehash but...

Astronuc or others with knowledge of the issue: I'm trying to assess how bad it is and could be compared with Chernobyl. Could you please comment on my understanding of how they compare:

1. The explosions in Japan have been steam and/or hydrogen explosions. Chernobyl's explosions were steam and likely a small nuclear explosion.

2. The explosions in Japan have destroyed the reactor buildings, leaving the reactor cores mostly intact due to their containment structures. The explosion in Chernobyl destroyed the reactor core due to the lack of containment, ejecting the core material itself into the surrounding area (and air).

3. The explosion combined with burning graphite remnants of the destroyed core is what released most of the radioactive material into the environment at Chernobyl. Most of the radioactive material released into the environment in Japan thus far has been carried by semi-controlled steam releases and uncontrolled steam explosions outside of the reactor core, neither of which can carry anywhere close to the quantities of radiactive material that were dispersed at Chernobyl.

4. The primary ongoing risks in Japan are the continued release of steam carrying small amounts of radioactive material and the potential for groundwater contamination due to cracks in the containment vessel and building foundation. Direct ejection of large quantities of core material is unlikely due to the containment vessels (Q: Is a "nuclear excursion" - a small nuclear explosion like at Chernobyl - a possibility here and could it destroy the reactor core containment vessels?).

5. Chernobyl had physics flaws that made it more difficult for the operators to stop the accident once it started (such as positive feedback loops leading to run-away increases in output for counterintuitive reasons). Japan's reactors contained an external safety flaw in the backup power systems that made it impossible to stop the accident. Q: Does the reactor physics that helped cause the "excursion" in Chernobyl exist in any form in Japan's reactors?

 

[Reno Deano]

Here is a link to current advanced design commerical reactors on the drawing boads and being reviewed for acceptibility:

http://www.nrc.gov/reactors/advanced.html"

 

[uart]

Going off topic slightly: If they knew about tsunamis, why build their homes on the coast? This is not a case of a power plant being the only thing built in a dangerous place. Peoples homes were built in the affected areas too. Clearly a lot of people didn't know about the tsunami risks being so great, else they wouldn't live there right? If they didn't live there the plant also wouldn't be there.

They know about tsunamis, they invented the word "tsunami", they're taught about there danger and there real possibility from the time they start school. The people who build homes on the coast do so as a calculated risk and assume that they will be able to evacuate in time given the warning systems in place. You can evacuate to higher ground in most places in half an hour but you cannot pick up a whole nuclear power station and move it somewhere else in that time. They should have known better than to situate it there given Japans tsunami history.

 

[Reno Deano]

4. The primary ongoing risks in Japan are the continued release of steam carrying small amounts of radioactive material and the potential for groundwater contamination due to cracks in the containment vessel and building foundation. Direct ejection of large quantities of core material is unlikely due to the containment vessels (Q: Is a "nuclear excursion" - a small nuclear explosion like at Chernobyl - a possibility here and could it destroy the reactor core containment vessels?).

Graphite reactors use highly enriched Thorium or Uranium for fuel and is more subject to "excursion" than low enriched (<5%) BWR or PWR commercial plants. Most BWR or PWR plants after running for several FP months created a Xenon gas poisoning that moderates off-the-bottom excursions. Control rod withdrawal stepping will generally thwart any attempt at excursion. Most excursions have occurred at highly enriched military reactor(s) and were preceded by a control rod(s) ejection from the core.

 

[TCups]

I see some of this has been answered so I apologize for the rehash but...

Astronuc or others with knowledge of the issue: I'm trying to assess how bad it is and could be compared with Chernobyl. Could you please comment on my understanding of how they compare:
. . .
4. The primary ongoing risks in Japan are the continued release of steam carrying small amounts of radioactive material and the potential for groundwater contamination due to cracks in the containment vessel and building foundation. Direct ejection of large quantities of core material is unlikely due to the containment vessels (Q: Is a "nuclear excursion" - a small nuclear explosion like at Chernobyl - a possibility here and could it destroy the reactor core containment vessels?).

I fear, physics fans,that it isn't a reactor meltdown or primary containment failure at any of the Fukushima reactors that will be big problem at Fukushima. It is 40 years worth (some 600,000) of spent fuel rods, stored on site atop the exploding buildings and in a large pool out back, that are going to be the long-long-long-long-term legacy and danger of this particular disaster.

No new reactor design will, at this point, take care of 40 years of accumulated nuclear waste on site that is now exposed or about to be exposed to the local environment, short of a miracle.

 

[Astronuc]

The U.S. has about 23 Mk-I's if I'm not mistaken.

I just read that the Ministry of Health Labour and Welfare has increased the legal limit of exposure for plant workers from 100mSv to 250mSv/hr.

Why would they do that? I thought radiation levels were decreasing around the plant, at least from what I can gather from the news.

Any thoughts.

Such a move would then 'legally' allow the workers to be exposed to a higher level - without taking the legally mandated actions at the lower level (whatever those are) - so they can stay at the site and deal with the situation.

That by the way is dose rate. The dose is the dose rate integrated over time. Has the dose limit been increased?

 

[Astronuc]

Another good site for information - http://www.jaif.or.jp/english/

and courtesy from the ANS Nuclear Cafe - http://ansnuclearcafe.org/. I believe the data came from JAIF reports.

Fukushima Daiichi Unit 1 reactor At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.17 MPa. The water level inside the reactor core was measured at 1.8 meters below the top of the fuel rods.

Fukushima Daiichi Unit 2 reactor At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.043 MPa. The water level inside the reactor core was measured at 1.4 meters below the top of the fuel rods.

Fukushima Daiichi Unit 3 reactor At 8:37AM on March 16, white smoke was observed emanating from the vicinity of the secondary containment building.

At 9:55AM on March 16, the pressure inside the reactor core was measured at 0.088 MPa. The water level inside the reactor core was measured at 1.9 meters below the top of the fuel rods.
At 11:32AM on March 16, the Japanese government announced that the possibility of significant damage to the primary containment vessel was low.

Fukushima Daiichi Unit 4 reactor At 4:08AM on March 15, the temperature of the spent fuel pool was measured at 183 degrees Fahrenheit.
At 5:45AM on March 16, a fire occurred in the vicinity of the third floor of the secondary containment building.
At 7:26AM on March 16, no flames or smoke was observed and thus it was concluded that the fire extinguished on its own accord.
Fukushima Daiichi Unit 5 reactor At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 141 degrees Fahrenheit.
Fukushima Daiichi Unit 6 reactor At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 137 degrees Fahrenheit.

Those temperatures are acceptable.

 

[lapsedgeo]

I see on Twitter that the US Embassy in Japan is now advising US citizens within 80k to evacuate area.