There is almost guaranteed significant radiation release.
quote from slashdot:
The outer walls of the Reactor 1 building have partially
blown off, leaving only what looks like a steel frame.
NHK is saying that a sensor within 5km of the plant is detecting
radiation levels approaching 1015 microsieverts
- that is apparently a year's worth of radiation exposure
EACH HOUR
People in the danger zones are being told to cover faces
with wet towels, avoid eating vegetables and other fresh foods,
and refrain from drinking tap water.
"This is starting to look a lot like Chernobyl" Walt Patterson, an associate fellow with Chatham House, has told the BBC after seeing pictures of the explosion at the Fukushima-Daiichi nuclear plant. "The nuclear agency says that they have detected caesium and iodine outside the unit, which certainly indicates fuel melting at the very least," he says. "Once you have melting fuel coming into contact with water, that would almost certainly be the cause of the explosion." (BBC)
(EDIT)
More from Walt Patterson of Chatham House. He says the presence of the radioactive caesium in the surrounding area does not pose a huge threat to public health in the immediate aftermath of the explosion. "What would be serious is if there was an explosion or fire that lifted this stuff high in the air, meaning it could get carried over a wide area."
BBC environment correspondent Roger Harrabin says local officials believe the release of radiation following the nuclear plant explosion is likely to be small. He adds that nuclear incidents aren't always as serious as they may sound or appear, and actually, in terms of loss of life and destruction, accidents at hydroelectric plants are far more dangerous.
Chernobyl also was a _bona fide_ reactivity excursion - a nuclear-driven steam explosion literally blew the core apart and spewed radioactive particulates into the atmosphere.
This is just built-up decay heat and chemical reactions.
Some reports[1] indicate radioactive iodine and cesium are being detected at monitoring stations. How could that happen if confinement hadn't failed? (fuel rods melting, containment failure of the reactor vessel and/or primary coolant loop, and the obvious lack of a containment building at this point)
Based on the description of two-stage containment for BWRs at wikipedia[2], and the video, if that's the containment strategy at Fukushima, it seems the drywell containment structure blew up, since steam being vented into a pool of water shouldn't cause a visible breach.
It seems that what you saw was the building surrounding the reactor being blown up, not the containment vessel, according to news accounts.
The containment referred to in this case is a vessel made of a feet-thick layer of concrete surrounding the reactor. This is the final defense if a fuel meltdown occurs: its job is to contain the burning fuel and prevent it from being exposed to the environment. [1]
What the GP was referring to is that there was no such vessel at Chernobyl, which was a very old reactor design. Modern reactors are surrounded in such vessels. [2]
Another interesting read is the story of the Russian engineers who prevented an explosion at Chernobyl by diving into the pool of water beneath the reactor and opening the drainage valves: http://en.wikipedia.org/wiki/Chernobyl_disaster#Steam_explos...
You could think about the outer building as keeping the rain out, and possibly aeroplanes to some extent. It is not the critical last defence against stuff happening in the reactor, the containment building is.
You can bet that the japanese army is keeping any possible threats out of there.
I read somewhere that this design does not have a containment dome. So basically containment wise (in comparison to Chernobil) this reactor is a bit better that it uses reactor containment vessel, but it does not use containment dome.
I also read that on TMI a similar hydrogen explosion occurred but it was contained by containment dome.
Well, judging from past nuclear accidents (Chernobyl, 3 mile island), I would:
1.) Not trust the government, the plant operator, the plant designer, hell anyone remotely involved. They always downplay whatever is really going on to prevent panic (or divert blame)
2.) Get as far away as possible, preferably in the opposite direction of prevailing winds.
Yea, let's not listen to the people that know what they're talking about. Let's spread fear, uncertainty and doubt. That always improves the situation.
Give me one example of when the government, the plant operator, the plant designer knowingly lied about the situation.
Give me one example of someone who was harmed by Three Mile Island which had a full meltdown with containment. (Chernobyl is irrelevant, it did not have containment.)
> Yea, let's not listen to the people that know what they're talking about.
Really? People with reputations at stake rarely or never spin information that minimizes impact to their reputations? People with dangerous information rarely or never, rightly or wrongly, minimize the impact of that dangerous information for concern over spreading panic?
Next you'll tell me POTUS never lies, Congress is looking out for our best interests, and nuclear power is essentially 100% safe.
> Give me one example of someone who was harmed by Three Mile Island which had a full meltdown with containment.
Quote:
A new analysis of health statistics in the region conducted by the Radiation and Public Health Project has, however, found that death rates for infants, children, and the elderly soared in the first two years after the Three Mile Island accident in Dauphin and surrounding counties.
Quote:
Exposure to high doses of radiation shortly after the nuclear accident at Three Mile Island may have increased cancer among Pennsylvanians downwind of the plant, scientists at the University of North Carolina at Chapel Hill say.
That's two.
> Chernobyl is irrelevant
Excellent news.
--
Another angle is that the "people that know what they're talking about" very often don't know what they're talking about, particularly in the minutes/hours/days following emergency conditions. TMI timeline:
Scranton held a press conference in which he was reassuring, yet confusing, about this possibility, stating that though there had been a "small release of radiation,... no increase in normal radiation levels" had been detected. These were contradicted by another official, and by statements from Met Ed, who both claimed that no radiation had been released.[21] In fact, readings from instruments at the plant and off-site detectors had detected radiation releases, albeit at levels that were unlikely to threaten public health as long as they were temporary, and providing that containment of the then highly contaminated reactor was maintained.
Government spokesman says the nuclear reactor container at the Fukushima-Daiichi plant has not been damaged, and the level of radiation has dropped following the explosion earlier on Saturday, AFP reports
but as you put it, can we believe this anymore? Yesterday everything was supposed to be under control.
Would be interesing to hear from communication professionals what they think about this.
I read his comment and I can't say that I disagree with his assessment given the amount of information that we have. I spent some time on a US nuclear warship and he's probably got some nuclear engineering background.
Right now, my main concern is the release of Caesium-137. If that has been detected, then there is a solid chance that the core has been at least partially exposed. Caesium-137 has a half-life of 30 years and is a gamma emitter. It's also water-soluble. Not a good combination.
The reactor building (the shield wall/missile shield) is also made of steel-reinforced, pre-stressed concrete 0.3 m to 1 m (1–3 feet) thick.
The concrete surrounding the building is now gone (due to excess pressure).
Second edit:
[6:54 a.m. ET, 8:54 p.m. Tokyo] The explosion at Japan's Fukushima nuclear plant was not caused by the nuclear reactor but by "water vapor that was part of the cooling process," Chief Cabinet Secretary Yukio Edano said Saturday. He said no harmful gases had been emitted by the explosion.
[6:44 a.m. ET, 8:44 p.m. Tokyo] Japanese Prime Minister Naoto Kan confirms that the evacuation area around the Fukushima Daiichi nuclear plant has been increased to 20 kilometers. But no one has been harmed by radiation, he says.
Third edit (from the BBC):
1218: It seems clear now from Mr Edano's comments that the nuclear plant building that was blown apart earlier did house a reactor, but the reactor was protected by its metal casing.
1216: Government spokesman Yukio Edano says the pressure as well as the radiation at the Fukushima-Daiichi nuclear plant has fallen following this afternoon's explosion.
So the "explosion" has actually helped the situation.
"We've confirmed that the reactor container was not damaged. The explosion didn't occur inside the reactor container. As such there was no large amount of radiation leakage outside," [Japan Chief Cabinet Minister Yukio Edano] said.
"At this point, there has been no major change to the level of radiation leakage outside (from before and after the explosion), so we'd like everyone to respond calmly," Edano said."
"Edano said due to the falling level of cooling water, hydrogen was generated and that leaked to the space between the building and the container and the explosion happened when the hydrogen mixed with oxygen there."
While damage to internal containment structures are possible, the building is likely to be resistant to these kinds of explosions.
A (what I guess) is a similar explosion happened in the reactor building in TMI, and the risk of an explosion such as this seems to be well known. The reactor building was probably prepared to absorb the explosion away from the containment structures, making it look much worse than it is.
I think you're right. I'm not sure on how PWR vs BWR plays out in this case though, but it definitely seems like they knew this explosion would happen. It looked very "controlled", even if it seemed like there was a lot of vapour and debris on video.
Got a mail from WANO relayed to me, below is the interesting part about the explosion.
-----
1. Hydrogen explosion occurred at 15:36 between containment and reactor building of Fukushima Daiichi unit 1. Walls of reactor building were blown out or damaged.
2. It was confirmed that unit 1 containment integrity was maintained.
Explosion was not inside the containment as it is inert.
3. Radiation level at the Fukushima Daiichi site border once increased when containment vent was conducted and reached 1,015 micro Sv per hour around the time when explosion occurred; however, the radiation level turned to decrease after the explosion down to 860 at 15:40 and 70.5 micro Sv per hour at 18:58.
4. Government has agreed to TEPCO decision to fill the entire containment up with sea water. The filling sea water will contain boron. TEPCO started the work for filling up at 20:20.
Boron has a high neutron cross-section, it therefore absorbs neutrons and slows down the fission process.
In a PWR you add it into the water as a way to moderate the reaction, but in a BWR (like the reactor 1 in Fukushima Daiichi) you only add it as a last resort, since it is incredibly hard to clean out of the system.
Kyodo News agency said radioactive caesium had been detected near the site, quoting the Japanese nuclear safety commission. Radioactivity rose 20-fold outside, reports said. (EDIT: this was before the explosion)
The plant "may be experiencing nuclear meltdown", Kyodo and Jiji reported before the explosion, while public broadcaster NHK quoted the safety agency as saying metal tubes that contain uranium fuel may have melted.(AFP)
Is 20-fold increase in radioactivity actually hazardous? I was under the impression dangerous levels of radiation are many, many times above normal background radiation and typical 'acceptable' levels of exposure.
According to http://www3.nhk.or.jp/daily/english/12_51.html the exposure level measured outside the plant is 1.015 mSv / hr. Exposure to about 1000 times that hourly level in a short time period is needed for life-threatening acute radiation poisoning.
Exposure to 1.015 mSv / hour for a year would give a dose equivalent of 8.9 Sv - the excess relative risk of cancer for low dose chronic radiation exposure is about 0.97 per Sv - so the exposure to that level for a year would drastically increase cancer risk.
Obviously, people won't be allowed into the areas where radiation levels were that high.
I saw a report of a worker acutely exposed to >100 mSv; that single event would be enough to increase that worker's lifetime risk of cancer by about 10%.
The average radioactive dose a person gets per year is about 3,6 to 5 milliSievert a year (for Belgium) of which 2,6 mSv from natural sources, 0,95mSv from medical examinations and 0,05mSv from industry (of which 0,01mSv due to nuclear power)
So when they say around the reactor the dose in an hour is about the same as you get a year, then this is about equivalent to two scans in a hospital.
Note: this is talking about low levels where the only influence radiation has is increasing the chance of cancer. If there are very high doses >100mSv involved, there will be direct radiological damage which can be strongly compared to damage from burning.
"Chief cabinet secretary Yukio Edano has told a press conference that he cannot confirm that the explosion at the nuclear power plant was the reactor, saying details of the incident remained unclear. He said authorities were prepared for the worst emergency but urged people to remain calm and not to listen to rumours. He also asked them to conserve electricity."
Any opinions on what the thing rising up very quickly during the explosion is? I initially thought it was the roof, but I'm wondering now if it isn't actually a flame from burning hydrogen. Ideas?
Can someone provide background information on the type of reactor at Fukusima, it's age, and it's failsafe mechanism. I was under the impression that no modern reactor would sustain criticality in the event of a failure.
It lacks the safety mechanisms of an abwr. Namely even after the control rods are deployed, heat can continue to build up. Hence the plant requires forced cooling, in this case provided by diesel and electric pumps. After the earthquake the diesel pumps failed and cooling was effected by battery power. While the government rushed in new diesel generators, they were not installed in time to prevent the build up of pressure resulting in this explosion.
Japanese officials believe that the tops of the fuel rods are exposed.
Agency officials said a team of National Institute of Radiological Sciences detected cesium, a radioactive substance contained in nuclear fuel rods, near the No. 1 reactor of the No. 1 nuclear plant, leading them to suspect nuclear fuel rods in the reactor began melting amid the high temperatures.
The nuclear safety agency said in the afternoon that the level of cooling water in the No. 1 reactor likely had dropped to 1.7 meters below the top of nuclear fuel rods, leading officials to suspect that about half of the rods' length had been exposed.
Reactor meltdown feared / Quake disabled Fukushima N-plants' cooling systems
This was confirmed by Tokyo Electric Power (the operator):
"A portion of the reactor's fuel rods, which create heat through a nuclear reaction, had become exposed due to the cooling-system failure. The spokesman for Tepco said 1.5 meters of the 4.5 meter long fuel rods were exposed. It was unclear Saturday afternoon whether the water added by workers had re-covered the rods."
From wikipedia: "Fukushima I – 1 BWR First criticality: March 26, 1971". So it isn't a "modern" reactor, not sure what the fail safes are but I have read from some sources all the fail safes are older generations which require power.
The Three Mile Island accident occurred on Wednesday, March 28, 1979. TMI Unit 2 received its operating license on February 8, 1978. So the Fukushima I appears to be slightly older than TMI.
Thanks, wiki continues to provide detailed information in the deep links on the page. It seems we are witnessing a case of failure upon failure. Truly a horrific tragedy for the country and the world.
what I understand now is that the blast at the nuclear plant may have been caused by a hydrogen explosion (pressure) or If nuclear fuel rods overheat and then come into contact with water, this produces a large amount of highly-flammable hydrogen gas which can then ignite. Right?
Can anyone with more knowledge and experience of this confirm?
That's certainly possible, theoretically. However, I'm not sure if those conditions can actually be met (rods should not ever come into contact with water and nothing should be able to ignite the gas, especially not at higher pressure levels).
No, actually the fuel pellets never need to come in contact with water; it is their cladding, which is a zirconium alloy ("Zircaloy"), which can react with steam under extreme conditions. It's a redox reaction: Zr + 2H2O --> ZrO2 + 2H2 or something similar.
This actually happened at Three Mile Island, and there was a hydrogen explosion in the containment building there (which did not break).
An attempt to explain the risk to the Fukushima nuclear plants following the earthquake: The plants are designed to shut automatically, which halts the main nuclear fission reaction, but there is a residual amou ntense heat within the system. Back-up generators should kick in to power the coolin mechanisms needed to dissipate that heat - b they fail, as appears to have happened here, temperatures rise. If this isn't stopped, the reactor vessel itself could eventually melt an eak.
Right? Has anybody found any documents if Japan has been notified or warned about these backup systems of these plants? It sound like a design failure to me. (I know nothing about nuclear power plants)
Watching BBC, it seems mainly the walls and roof have been blown out.
The main steel structure is still standing, and the expert in the studio was saying something like there still is a chance of the 3-Mile Island like scenario. That is that the nuclear material is still contained within the core structure.
As I understood it (when discussing it with someone in the know), was that it was likely caused by zirconium in the fuel-rods reacting with water.
This hydrogen should be taken care of, but without (enough?) electrical power levels of hydrogen gas builds up.
This does not mean that containment is broken, or that there is an imminent danger to outsiders. But it is a very serious situation, especially since there seems to be at least two more reactors in similar situations at Fukushima Daiichi.
Come on, there is absolutely no way for a nuclear plant to make a nuclear explosion. Nuclear fuel at high temperature touching the cooling water separates the water in O and H2, which is an highly explosive cocktail, didn't they show you that in high school?
The main danger now is of a fire lifting radioactive material away. This isn't in any case an immediate life-threatening risk, except for the people in the power plant immediate vicinity.
A nuclear explosion? No chance, it will "simply" leak, worst case it catches fire and goes Chernobyl but spreads its radiation over a more populated area, which is probably worse that a nuclear weapon going off.
Head over to Fark, look up whatever the latest thread is. Yes, there are trolls and idiots. There are also knowledgeable people providing useful information. I'm basically refreshing that every few minutes and using it as my baseline for what's going on.
The things we should fear are myocardial infarction [1] and cerebrovascular accident [2]. These are what will probably kill us in developed countries [3]. The good news is that we know how to prevent many of these deaths: regular exercise, not over-eating, not smoking and moderation in alcohol and drug consumption. Other causes of death and ill-health are also reduced by these actions.
An excellent response to nearly any concern of disaster, terrorism, or other highly-visible but highly-unlikely danger. Fear is only natural, but it's amazing how quickly it can be allayed with a little perspective.
Yes, you will likely be death in the next 100 years.
Seriously though the structure that contained the reactor isn't the only thing that protects the reactor (it was at Chernobyl, which is why it went badly) it is also protected by a thick concrete container (which is pretty much what was eventually built around the Soviet reactor) which means that in the event of a meltdown the structure will contain the radioactive stuff.
So in summary: unless you are really close (which you shouldn't be) or have a burning desire to be inside that reactor building you will die of something else entirely (most likely something boring).
No. Even if shit gets real and the reactor goes Chernobyl, Japan is sufficiently far away from the western world that it doesn't matter at all. People weren't concerned about radiation from the nukes in Bikini either.
Still hard to say. Fortunately, the wind is forecast to go out towards the Pacific for the next few days. But if the situation escalates as badly as Chernobyl, enough stuff may get out for everyone to get some.
it looks to me like a still-standing structure completely disappeared. watch the replay a couple times. there's a white building not unlike 2 other to the right, is partially covering a lightning rod. when you see the shockwave, it's no longer there, at all.
This picture just appeared on Wikipedia, of which I am guessing is the building that may or may not be the one that possibly exploded. Maybe someone more knowledgable than myself can identify what the building is used for. The 2011 Sendai earthquake article says " the outer structure of reactor number 1's containment building had blown off, releasing a large cloud of dust and vapour."
The longer, rectangular buildings on the seaside are the turbine halls, and the square buildings next to them (in the inland direction) are the containment buildings.
fuck everything about shitty government monopolies on dangerous aging infrastructure. not politically popular = not getting renovated this year! (ad infinitum)
I don't think renovating a nuclear power is difficult to stir up popular support for if the experts want it renovated badly. I doubt private industry would have had any more foresight.
There is almost guaranteed significant radiation release.
quote from slashdot: