Fukushima Nuclear Accident Facts

[ProgressiveTokyo]

In case you wanted to know:

What is going on here?

In the aftermath of the recent earthquake and tsunami in Japan, two nuclear power stations on the east coast of Japan have been experiencing problems. They are the Fukushima Daiichi ("daiichi" means "number one") and Fukushima Daini ("number two") sites, operated by the Tokyo Electric Power Company (or TEPCO). Site one has six reactors, and site two has four. The problematic reactors are #1, #2, and #3 at site one, which are the oldest of the ten and were due to be decommissioned this year.
In short, the earthquake combined with the tsunami have impaired the cooling systems at these reactors, which has made it difficult for TEPCO to shut them down completely. Reactor #1 is now considered safe after crew flooded the reactor with sea water. Reactor #3 was starting this process as this was originally written (6:00PM CST/11:00PM GST on March 13th). Site crew began preparing to add sea water to reactor #2 around 7:30AM GMT on March 14th, if a cooling procedure does not work.
The four reactors at site two did not have their systems impaired and have shut down normally.
Can this cause a nuclear explosion?
No. It is physically impossible for a nuclear power station to explode like a nuclear weapon.
Nuclear bombs work by causing a supercritical fission reaction in a very small space in an unbelievably small amount of time. They do this by using precisely-designed explosive charges to combine two subcritical masses of nuclear material so quickly that they bypass the critical stage and go directly to supercritical, and with enough force that the resulting supercritical mass cannot melt or blow itself apart before all of the material is fissioned.
Current nuclear power plants are designed around subcritical masses of radioactive material, which are manipulated into achieving sustained fission through the use of neutron moderators. The heat from this fission is used to convert water to steam, which drives electric generator turbines. (This is a drastic simplification.) They are not capable of achieving supercritical levels; the nuclear fuel would melt before this could occur, and a supercritical reaction is required for an explosion to occur.
Making a nuclear bomb is very difficult, and it is completely impossible for a nuclear reactor to accidentally become a bomb. Secondary systems, like cooling or turbines, can explode due to pressure and stress problems, but these are not nuclear explosions.

Is this a meltdown?

Technically, yes, but not in the way that most people think.
The term "meltdown" is not used within the nuclear industry, because it is insufficiently specific. The popular image of a meltdown is when a nuclear reactor's fuel core goes out of control and melts its way out of the containment facility. This has not happened and is unlikely to happen.
What has happened in reactor #1 and #3 is a "partial fuel melt". This means that the fuel core has suffered damage from heat but is still largely intact. No fuel has escaped containment. Core #2 may have experienced heat damage as well, but the details are not known yet. It is confirmed that reactor #2's containment has not been breached.
How did this happen? Aren't there safety systems?
When the earthquakes in Japan occurred on March 11th, all ten reactor cores "scrammed", which means that their control rods were inserted automatically. This shut down the active fission process, and the cores have remained shut down since then.
The problem is that even a scrammed reactor core generates "decay heat", which requires cooling. When the tsunami arrived shortly after the earthquake, it damaged the external power generators that the sites used to power their cooling systems. This meant that while the cores were shut down, they were still boiling off the water used as coolant.
This caused two further problems. First, the steam caused pressure to build up within the containment vessel. Second, once the water level subsided, parts of the fuel rods were exposed to air, causing the heat to build up more quickly, leading to core damage from the heat.

What are they doing about it?

From the very beginning, TEPCO has had the option to flood the reactor chambers with sea water, which would end the problems immediately. Unfortunately, this also destroys the reactors permanently. Doing so would not only cost TEPCO (and Japanese taxpayers) billions of dollars, but it would make that reactor unavailable for generating electricity during a nationwide disaster. The sea water method is a "last resort" in this sense, but it has always been an option.
To avoid this, TEPCO first took steps to bring the cooling systems back online and to reduce the pressure on the inside of the containment vessel. This involved bringing in external portable generators, repairing damaged systems, and venting steam and gases from inside the containment vessel. These methods worked for reactor #2 at site one, prior to complications; reactors four through six were shut down before for inspection before the earthquake hit.
In the end, TEPCO decided to avoid further risk and flooded reactor #1 with sea water. It is now considered safely under control. Reactor #3 is currently undergoing this process, and reactor #2 may undergo it if a venting procedure fails.
The four reactors at site two did not have their external power damaged by the tsunami, and are therefore operating normally, albeit in a post-scram shutdown state. They have not required any venting, and reactor #3 is already in full cold shutdown.

Is a "China Syndrome" meltdown possible?

No, any fuel melt situation at Fukushima will be limited, because the fuel is physically incapable of having a runaway fission reaction. This is due to their light water reactor design.
In a light water reactor, water is used as both a coolant for the fuel core and as a "neutron moderator". What a neutron moderator does is very technical (you can watch a lecture which includes this information here), but in short, when the neutron moderator is removed, the fission reaction will stop.
An LWR design limits the damage caused by a meltdown, because if all of the coolant is boiled away, the fission reaction will not keep going, because the coolant is also the moderator. The core will then only generate decay heat, which while dangerous and strong enough to melt the core, is not nearly as dangerous as an active fission reaction.
The containment vessel at Fukushima should be strong enough to resist breaching even during a decay heat meltdown. The amount of energy that could be produced by decay heat is easily calculated, and it is possible to design a container that will resist it. If it is not, and the core melts its way through the bottom of the vessel, it will end up in a large concrete barrier below the reactor. It is nearly impossible that a fuel melt caused by decay heat would penetrate this barrier. A containment vessel failure like this would result in a massive cleanup job but no leakage of nuclear material into the outside environment.
This is all moot, however, as flooding the reactor with sea water will prevent a fuel melt from progressing. TEPCO has already done this to reactor #1, and is in the process of doing it to #3. If any of the other reactors begin misbehaving, the sea water option will be available for those as well.

What was this about an explosion?

One of the byproducts of reactors like the ones at Fukushima is hydrogen. Normally this gas is vented and burned slowly. Due to the nature of the accident, the vented hydrogen gas was not properly burned as it was released. This led to a build up of hydrogen gas inside the reactor #1 building, but outside the containment vessel.
This gas ignited, causing the top of the largely cosmetic external shell to be blown off. This shell was made of sheet metal on a steel frame and did not require a great deal of force to be destroyed. The reactor itself was not damaged in this explosion, and there were only four minor injuries. This was a conventional chemical reaction and not a nuclear explosion.
You see what happened in the photo of the reactor housing. Note that other than losing the sheet metal covering on the top, the reactor building is intact. No containment breach has occurred.
At about 2:30AM GMT on March 14th, a similar explosion occurred at the reactor #3 building. This explosion was not unexpected, as TEPCO had warned that one might occur. The damage is still being assessed but it has been announced that the containment vessel was not breached and that the sea water process is continuing.
Around 7:30AM GMT on March 14th, it was announced that the explosion at reactor #2 has damaged the already limping cooling systems of reactor #2. It may also receive the sea water treatment if they are unable to use a venting procedure to restart the cooling systems.

Is there radiation leakage?

The radiation levels outside the plant are higher than usual due to the release of radioactive steam. These levels will go down and return to their normal levels, as no fuel has escaped containment.
For perspective, note that charts detailing detrimental radiation exposure start at 1 Gy, equivalent to 1 Sv; the radiation outside the problematic Fukushima reactors is being measured in micro-Svs per hour. The highest reported levels outside the Fukushima reactors has been around 1000 to 1500 micro-Svs per hour. This means that one would have to stay in this area for four to six weeks, 24 hours a day, without protection in order to experience the lowest level of radiation poisoning, which while unpleasant is not normally fatal. And this level will not stay where it is.
Also note the chart of normal radiation exposure levels from things like medical x-rays and airline flights.
There have also been very minor releases of radioactive reactor byproducts like iodine and cesium along with the steam. This material is less radioactive than the typical output of coal power plants. It is significant mainly as an indicator of the state of the reactor core.
I read that there's a plume of radioactive material heading across the Pacific.
In its current state, the steam blowing east from Japan across the pacific is less dangerous than living in Denver for a year. If it makes it across the ocean, it will be almost undetectable by the time it arrives, and completely harmless as the dangerous elements in the steam will have decayed by then.
What's this about fuel rods being exposed to the air?
When the coolant levels inside the reactor get low enough, the tops of the fuel rods will be exposed to the air inside the containment vessel. They have not been exposed to the external atmosphere and the containment vessels are all intact.

Can this end up like Chernobyl?

No, it cannot. for several reasons.
Chernobyl used graphite as a neutron moderator and water as a coolant. For complicated reasons, this meant that as the coolant heated up and converted to steam, the fission reaction intensified, converting even more water to steam, leading to a feedback effect. The Fukushima reactors use water as both the coolant and the neutron moderator, which means that as the water heats up and converts to steam, the reaction slows down instead. (The effect of the conversion of water coolant to steam on the performance of a nuclear reactor is known as the "void coefficient", and can be either positive or negative.)
Chernobyl was designed so that as the nuclear fuel heated up, the fission reaction intensified, heating the core even further, causing another feedback effect. In the Fukushima reactors, the fission reaction slows down as the fuel heats up. (The effect of heating of the nuclear fuel on the performance of a nuclear reactor is known as the "temperature coefficient", and can also be positive or negative.)
Chernobyl's graphite moderator was flammable, and when the reactor exploded, the radioactive graphite burned and ended up in the atmosphere. The Fukushima reactors use water as a neutron moderator, which is obviously not flammable.
Note that while Chernobyl used light water as a coolant (as distinct from heavy water), it was not a "light water reactor". The term LWR refers strictly to reactors that use light water for both cooling and neutron moderation.
The news said this was the worst nuclear power accident since Chernobyl, though.
It's the only nuclear power plant accident of its type since Chernobyl. It's easy to be the worst in a sample size of one.

Is this like Three Mile Island?

There are similarities. The final effect on the world is likely to be similar: no deaths, minimal external contamination, and a tremendous PR disaster for the nuclear industry due to bad reporting by the media.

How can I keep up with developments?

The western media has been very bad about reporting this event, due to a combination of sensationalist reporting, ignorance, and the use of inexact or unexplained terminology.
One of the safe sources of information is the TEPCO site, which has been posting press releases on a regular basis. Unfortunately, this site is often unresponsive due to the immense traffic it is receiving.
The important thing to remember is that most of the "experts" appearing on the news are engaging in speculation. Very few of them are restricting themselves to what they can be sure about, and those that are have often been misrepresented.

[CyberDruid]

Thanks PT.

I have been using Russia Today and AlJazeera for news th past couple of months. Even Malta Today is better than the US reporting. Our news reporting is very poor.

[yogurt_21]

wow, no leak, all 3 were set to be decommissioned, and they're already done with #1, almost done with #3 and working on #2.


total different story from our news here, nice to get a real rundown.

[Fourstaff]

British media is just as bad, but on the other hand its good to know that the Japanese knows what to do in emergencies.

[FordGT90Concept]

I wouldn't say that. Having known what caused the explosion in #1, they should have taken steps to prevent it from happening in #2. Then it happened a third time. That's pretty damn inexcusable.

[Fourstaff]

Originally Posted by FordGT90Concept

I wouldn't say that. Having known what caused the explosion in #1, they should have taken steps to prevent it from happening in #2. Then it happened a third time. That's pretty damn inexcusable.

Its not that easy to handle the reactors, you know. Its easy to say "why don't they pour seawater in and be done with it", but you must know when, how much, etcetcetc. Its the minor details which causes problems. On the other hand, knowing what causes the problem does not mean that you will automatically have the answers.

[FordGT90Concept]

The explosions were separate from the reactors. They occured in other parts of the nuclear power plants. The suspected cause of the explosions was build up of hydrogen. As you should know, once you have hydrogen, all you need is a spark. Once they discovered the cause of the explosion at #1, they should have checked the other 11 reactors for the same conditions and done something about it (venting it, most likely) quickly.

If that weren't enough, the JSDF (Japanese Self Defense Force) arrived in areas of the country that were hit by the tsunami without heavy equipment to clear debris nor canine units that could quickly find survivors. In other words, they came wholely unprepared.

Not to mention, we aren't even a week into this mess. They aren't doing a horrible job but they aren't doing excellent either. I'd say they are about on par with USA's handling of Katrina (poorly).

[Magibeg]

http://www.educatedearth.net/nuclearjapan.php


oh crap breaking news, bad stuff happening at reactor 2.

[FordGT90Concept]

Did that second explosion breach the containment vessel? If it's not holding water, I have to assume it is--or it is creating steam faster than they can fill it. I hope uranium hasn't already escaped the plant. That would be bad joojoo.

[Magibeg]

"I was just listening to a nuclear reactor expert on Al Jazeera explain that things are much more grim than what the Japanese officials are saying at their press releases. The 2nd explosion happened as "water levels were so low they exposed the fuel rods", but why were the water levels so low suddenly? He said the only explanation was that the actual core was now leaking and boiling away all the water at a faster rate than what was previously being pumped in, causing the pressure to rise and a reactor container to explode.
This 3rd explosion now may only reinforce what he was saying: the core is leaking. All those brave men and women working around the clock to keep the reactors cool essentially know they are going to die within a month from the radiation exposure, but they are sticking with it to save their country. This is straight from the expert's mouth. He was visibly distraught because the physics of what the press releases are saying don't add up right.

Edit Two anchors on NHK TV, a news channel from Japan, have a little dry-erase board mock up of the nuclear reactor. They are describing the containment vessel with the fuel rods and the water cooling it off to the television. They just said that this 3rd explosion has damaged the containment vessel, and explained that the containment vessel is now the last vessel protecting the outside world from the radioactive material. They said this means that it is very likely that the radioactive material is now exposed and leaking after this 3rd explosion.

Edit 2 There is a conference being held right now by the people who are directly managing the cooling process, The Tokyo Electric Power Company. They are being very vague and keep "apologizing for the inconvenience and concerns" this situation is bringing about in the public. Media members keep asking questions about what actually happened and insisted multiple times "we just want the facts" because the explosion that just occurred was not from hydrogen build up and the officials are not answering their specific questions about the damage or its implications.

Edit 3 Tensions seem to be very high at the conference. The media is asking questions and the officials are still being vague and not giving them direct answers. To get an idea of their vague replies: Someone asked what the reasoning behind the workers reportedly evacuating because of the explosion. The official replied along the lines of "Because there was a sound." You can see why frustrations are increasing during this conference.

Edit 4 The conference ended with the officials saying the pressure inside the vessel has gone down and that they can increase the water levels, but the people at the conference keep asking how they can do all of this if the vessel is damaged and broken. It is my final analysis of that conference that the officials may not know the extent (if any) of the damage of the vessel, but the media at the conference feel like something is terribly wrong and could not get any direct answers from the officials.

Facts that can be taken from this conference: The explosion occurred near/in the "suppression chamber" (which is located at the bottom of the containment vessel and holds the fuel rods and the water). Extent of damage is not known at the moment, but ALL THE WORKERS AT THE PLANT THAT ARE NOT DIRECTLY INVOLVED WITH PUMPING WATER INTO THE CHAMBER have evacuated. The core is now feared to be leaking.

Edit 5 Water levels are only covering about 2.7m of the fuel rods in Reactor 2. This is "about half the length of the fuel rods." This suppression chamber is the "last line of defense" for Reactor 2, and it is now damaged.
Here is the diagram the Japanese news anchors are showing of the suppression chamber, where the explosion occurred.

Edit 6 Now the anchors have a guest on and they are discussing that things are very serious. They are criticizing the Tokyo Electric Power Company for being very unclear at their press conference and how the officials did not share enough information with the public to explain what the implications of this explosion means. The anchors are now concerned for the safety of the people of Japan because of how vague the Tokyo Electric Power Company was during its explanation.

Edit 7 Officials now report they are observing a vapor coming from the top of Reactor 3. They are unsure of what this vapor/smoke is.

Edit 8 The US Government has now said that Japan has sent out a request for help with cooling the reactors."

[FordGT90Concept]

CNN just jumped briefly to it. He said the word "meltdown" has been used a lot. Very bad joojoo.

I hope the second explosion wasn't caused by steam because, well, that would be the containment vessel.


Glad they asked the US Government for help but what can we do now? It's too late from the sounds of it.

[Magibeg]

Originally Posted by FordGT90Concept

Glad they asked the US Government for help but what can we do now? It's too late from the sounds of it.

Realistically what could they have done before? This might have been the inevitable scenario that has just been delayed due to labored efforts.

[Magibeg]

"// 9:03 PM - March 14 2011
Radiation levels have skyrocketed near the front gate of the Fukushima No.1 nuclear power station, with 1 hour exposure being 8x the amount a human can healthily handle a year."

[Magibeg]

"Edit 9 The pressure in the suppression chamber where the cooling process occurs is now down to 1 ATM. The expert guest on NHK TV has said that this may very well mean that cracks have occurred in the chamber. 1 ATM is the normal pressure you feel everywhere on Earth, and for a SEALED suppression chamber that contains boiling water from the heat emitted from the fuel rods, the pressure should be much higher from all the vapor and gas forming inside the chamber and having no where to go. If the atmospheric pressure inside the chamber is the same as outside, this almost definitely means there are cracks in the chamber.

Edit 10 Water levels rose right after the explosion, but soon thereafter began going back down. Text on the live feed said that the water levels were too low to even be measured, but the officials insisted they are continuing to pump water into the pool. Japanese anchors are saying "this is reaching the point of worst case scenario"

Edit 11: 8:20pm CT The two main stock markets in Japan have fallen between 6-7.5% today, and about 4-5% each right after news of this latest explosion broke out."

[FordGT90Concept]

Originally Posted by Magibeg

Realistically what could they have done before? This might have been the inevitable scenario that has just been delayed due to labored efforts.

Prepared to fill the bastard with cement and minimize the risk of another explosion.

The only option now, if the plant is close enough to the ocean, is for an aircraft carrier to pump a crapton of water into that plant, hopefully faster than it can leave. That would require drilling several large holes in the containment vessel though which, in the long run, would probably be a bad thing. Also, I'm pretty sure the power plant is many miles inland so the odds of that happening at all are none.

Yeah, they're basically screwed.

Originally Posted by Magibeg

"// 9:03 PM - March 14 2011
Radiation levels have skyrocketed near the front gate of the Fukushima No.1 nuclear power station, with 1 hour exposure being 8x the amount a human can healthily handle a year."

That's not even the plant that is leaking like a seive.

Originally Posted by Magibeg

Edit 11: 8:20pm CT The two main stock markets in Japan have fallen between 6-7.5% today, and about 4-5% each right after news of this latest explosion broke out."

Surprised it didn't drop more than that. I bet it's gonna fall at least 20% by the time the market closes today.

[Magibeg]

"Edit: 9:00pm CT The Prime Minister of Japan will be speaking directly to the Japanese people within the hour. Actually it is happening now.
"Please listen to my message calmly....every possible method has been used to cool down the reactors. However, for reactor 1 and 2, hydrogen have come out causing explosion. Reactor 4 we have seen fire.... and radiation has spread from these reactors. And the readings of the levels seem very high. And there is still very high risk of more radioactive material coming out.."
"....We need everyone from 20km from the power plant 1 to evacuate.....everyone near #2 Power Plant within 10km please move out. We are trying everything we can to make sure further radioactive leakage does not occur. Workers injecting seawater are putting themselves at extreme danger in trying to prevent further leakage."
He wants everyone to "please react calmly to all the information they hear."
He was asked a specific question about Reactor 2 but did not want to comment on any specific reactors, only the nuclear power plant as a whole. This ends the Prime Minister's speech

Japan's Chief of Secretary (?) now talks
There is now a fire at #4 reactor"

There are no fuel rods in reactor 4, but there are spent fuels there that still emit heat. #4 reactor is currently burning...
1 and #3 reactors....outer containers were blown off. For #4 reactors, things fell into the reactor rather than being exploded out.

[Magibeg]

Secretary and Prime Minister mainly urged people to evacuate beyond the new radii they determined to reduce radiation. The secretary said they now had radiation readings as high as 400 milli-sieverts, over 1000x the amount reported earlier. This kind of radiation can make someone more fertile. The anchors are saying this is very serious and were surprised that the secretary briefly mentioned the levels were now as high as 400 millisieverts. However, much of the focus was on telling people to evacuate further. This marks the end space of Edit: 9:00pm CT

[ProgressiveTokyo]

Reactors 1 - 3 are now cooled down and have no further problems. The waste in reactor #4 (spent fuel rods) is an urgent issue now after a hydrogen explosion disturbed the waste. They are working to cool it off now.

I think this crisis could be over (from an immediate danger standpoint, obviously clean up will take a while) by tomorrow or the day after.

The Japanese engineers have really brought their A game and gotten a handle on this.

Phew, now lets just hope no more fucking earthquakes for a while!!!

[twilyth]

William Tucker (apparently a nuke expert who wrote an op-ed in the WSJ today) was on Bloomberg. He said the containment vessel is 10ft of steel reinforced concrete and that there was/is no chance of a breach. Chernobyl apparently didn't even have a containment vessel around the core, so comparisons to that disaster are absurd. He said it is most like TMI.

edit: he also said that a test was done in the 90's where a jet was flown at 500mph into the same kind of wall and it just disappeared, it was vaporized with no significant damage to the wall.

[Black Panther]

Things seem to be getting worse?

"Japan has officially asked the UN atomic watchdog to send a team of experts to help in the current nuclear crisis, International Atomic Energy Agency (IAEA) chief Yukiya Amano has said, after a second hydrogen explosion has exposed nuclear fuel rods. And earlier today Japan admitted that the radioactive leaks will effect human health

Radiation from Japan's quake-stricken Fukushima Daiichi nuclear plant on the Eastern coast has reached harmful levels, the Japanese government says. The warning comes after the plant was rocked by a third blast which appears to have damaged one of the reactors' containment vessels for the first time. If it is breached, there are fears of more serious radioactive leaks. The danger zone has been extended, warning residents within 30km to evacuate or stay indoors."

Read more here: http://www.maltatoday.com.mt/news/wo...nto-atmosphere

[ProgressiveTokyo]

Originally Posted by Black Panther

Things seem to be getting worse?

"Japan has officially asked the UN atomic watchdog to send a team of experts to help in the current nuclear crisis, International Atomic Energy Agency (IAEA) chief Yukiya Amano has said, after a second hydrogen explosion has exposed nuclear fuel rods. And earlier today Japan admitted that the radioactive leaks will effect human health

Radiation from Japan's quake-stricken Fukushima Daiichi nuclear plant on the Eastern coast has reached harmful levels, the Japanese government says. The warning comes after the plant was rocked by a third blast which appears to have damaged one of the reactors' containment vessels for the first time. If it is breached, there are fears of more serious radioactive leaks. The danger zone has been extended, warning residents within 30km to evacuate or stay indoors."

Read more here: http://www.maltatoday.com.mt/news/wo...nto-atmosphere

That news is about 8-12 hours behind the current situation. We are getting hourly updates from those on the ground. It is not getting worse, it is getting better.

[de.das.dude]

wow. using water as coolant and moderator is a good idea. what would happen if the water supply was down?

i guess the plants must be using a recycled supply of deuterium dioxide(heavy water) as the moderator and simple water as the coolant?

and since the reactor 1 as been drowned with sea water (which also is to some extent heavy water) will this water be put back into the sea again?? will it be safe??

[Bundy]

Originally Posted by de.das.dude

wow. using water as coolant and moderator is a good idea. what would happen if the water supply was down?

i guess the plants must be using a recycled supply of deuterium dioxide(heavy water) as the moderator and simple water as the coolant?

and since the reactor 1 as been drowned with sea water (which also is to some extent heavy water) will this water be put back into the sea again?? will it be safe??

Answering your Q's
1. There is plenty of water unles the pumps fail - as has happened in this case
2. Don't know
3. it will not go back to the ocean but if it did, there would be no problem. The water itself doesn't become radioactive, it can be filtered to contaoin the contaminants.

[CyberDruid]

Best explanation of how the Japanese Reactors work yet. Explains why a reactor most continue to be cooled even when the boron rods are in place. Explains why Hydrogen is produced.

Unfortunately Twilyth won't know about this because he refuses to watch YouTube videos.

[entropy13]

Just read some of the titles and captions on the articles about this.

"Worst nuclear accident since Chernobyl" LOL yeah it's quite easy to be the worst when you're the only nuclear accident since Chernobyl.