Japan [Tag: Fucked]

[Goumindong]

This was my thinking the moment the quake happened.  If the water levels are consistently dropping and they dont know why, the only explanation is a crack in the flooring allowing seepage into the groundwater.
It's no different then when you've got a leak in the vinyl lining of a pool.

It is highly unlikely that they have a containment breach. The levels of radiation that we could detect from a breach would be much higher than the levels we are detecting.

It is much more likely that they know exactly why the water levels are consistently dropping and that reason is that after an earthquake when you're operating off battery power it is hard to constantly cycle the water and/or pump new water into the facility.

The water evaporates (this is what causes the hydrogen gas that exploded, but the explosion only happened after the gas was vented and not in danger of damaging containment)

[Ghambit]

Also, the condition of the steel containment is a big "?" in my eyes.  Anyone who works with steel knows that as strong as it may seem, it's a pretty fragile metal.  This is a Japanese plant, likely using japanese steel (which sux btw), from 40 yrs. ago, along a seawater coastline, just went through a 9.0 quake, tsunami, two hydro. explosions, radiative degradation, crooked management, molten temps, and on and on.  Sure, a meltdown wont do nothin' at all.  Yah... nothin to see here, move along now.  

Keep your pants on.  The steel container being discussed is the second of three vessels.

The 1st vessel being a 16cm steel container.  The 2nd being the outer concrete "blanket."  The third being the now blown away containment building yes?
Let's assume a full meltdown occurs and weak spots in the main steel pressure vessel are compromised.  What happens then?  Concrete tends to burn at 3000C dont it?

I dunno, I just dont see how they can paint such a rosy picture on this situation.  There are too many drastic variables to sit around all comfortable-like when we're talking about containing nuclear forces within a human-made structure no one can get close enough to to even definitively say "all's well."  Everything they've done now has been reactive; sampling the air, pouring water on it, etc.  Can anyone at that plant say definitively the condition of ANY of those reactors w/o turning into a pile of goo or waiting 5 yrs for it to cool enough?

[Sand]

 Can anyone at that plant say definitively the condition of ANY of those reactors w/o turning into a pile of goo or waiting 5 yrs for it to cool enough?

No, which is what I just posted. Quote from a Japanese official.

Japanese officials say the nuclear fuel rods appear to be melting inside all three of the most troubled nuclear reactors.

Chief Cabinet Secretary Yukio Edano said Monday: "Although we cannot directly check it, it's highly likely happening."

[Arthur_Parker]

At the risk of Murgos shouting at me again, I don't really think the reactors are the main problem, the radiation is, if it gets too high in the area, due to the pressure releases or the lack of coverage in the pools then maintenance is difficult.  Each hour that passes since scram is good as the reactors get easier to cool.

[UnSub]

Man, what a tragedy on a grand scale.

Sand:  They always do death tolls like this.  They don't consider them dead until they have corpses, and they don't consider them missing until they are formally reported as such.  Knowing a train got swept away is one thing, having it officially reported that there were 500 people on it by the proper authorities is another.  I think everyone knows that we are talking tens of thousands, though.  Like you, I often wonder why the media dance around it so much.

Anyone else remember the 2004 Boxing Day tsunami? Estimates of up to 300k people killed with most of those bodies never found because they they were washed away.

We probably dance around it because we can't comprehend it.

[Sheepherder]

So I keep hearing that the water levels in the reactors aren't rising.  Is this because the fuel is so hot it's evaporating it all near-instantly or something more dire, like the quake cracked the reactor floor and it's all just spilling out?

The containment is probably mounted on some sort of suspension system.

It doesn't really matter whether it's leaking or not, water anywhere near a slab of steel heated to a few hundred degrees is going to flash to steam, and in the process remove fairly significant amounts of heat from the environment.

The core is undoubtedly fucked though.  After rapid heating, wetting, and cooling the temper will be shot to hell and the inside will probably be caked salt and rust.

[Jeff Kelly]

FYI the Richter scale is a logarithmic scale so an 8.0 earthquake is ten times a strong as a 7.0 earthquake and if the plant was designed for an 8.2 scale quake on site a 9.1 would be seven to eight times as strong.

It is impressive that the plant actually withstood a quake that probably was 5 times as strong as what the facility was designed for.

Also for those wondering where all the water went, you do know that cooling also works by evaporating water? Usually the water circulates and is evaporated in the reactor core, drives the turbines and is then recondensed in the condensor/cooling tower. Since the circulation doesn't work and they don't have any condensers they basically pump water into the reactor and vent the steam into the environment, thereby cooling the core. Or what do you suppose that "controlled release of steam" means?

The safety protocols have three contingencies for that.

1. Attach portable pumps and condensers to the existing circuit and restart the circulation
2. Pump Water into the core and release the evaporation into the environment if pumps/condensers don't work
3. submerge the containment vessel and use the secondary containment as heatsink if the core is too hot or pumping doesn't work

Newer BWR reactors are actually designed so that secondary containment is an effective heatsink and provide emergency water supplies that can be used to submerge the core.

[Goumindong]

The 1st vessel being a 16cm steel container.  The 2nd being the outer concrete "blanket."  The third being the now blown away containment building yes?

No, the first containment is the fuel rods themselves. They're steel tubes filled with the material. The second is the steel container, the third is the concrete surrounding the container.

The building doesn't do any containment. It is simply there to keep the weather out.

[jakonovski]

What I'm worried about, with my layman understanding, is a hydrogen blowout/explosion in the core.  

[Chimpy]

I just love that certain people have turned this into another place to link tons of stuff that they read on the internet that inflames their anti-scientific data conspiracy theories.

[jakonovski]

anti-scientific data conspiracy theories

The what now?

[Mrbloodworth]

I just hope that NE japan does not become uninhabitable, the wave crushed enough, they don't need another issue to contend with.

[NowhereMan]

What I'm worried about, with my layman understanding, is a hydrogen blowout/explosion in the core.  

The hydrogen explosion was the result of the superheated gases getting vented into the air. Hydrogen and oxygen in 2000c temperatures goes bang but the important thing is it's happening when they vent the gases and not inside the core itself. It is, I believe, a pretty expected by product that looks fucking dramatic but isn't cause for concern.

Also Ghambit, everything they are doing is reactive but not in a, "Fuck, stuff just happened? Oh God we need to do stuff about it, how could this have happened?!?!" way. It's all stuff that's been predicted and if what they're doing isn't working they move on the next planned step. I guess I'm not sure why that in particular is cause for concern since it isn't like they can do something before anything happens. Unless their initial reaction to things going wrong had been to flood everything there with sea water, scrapping the fuel for all the reactors and leaving the whole plant off-line for the next 4-5 years as it's replaced. Which would be incredibly expensive.

[Murgos]

I just hope that NE japan does not become uninhabitable, the wave crushed enough, they don't need another issue to contend with.

Oh, jeesus christ.

In the last 48 hours, Tepco has carried out repairs to the emergency core coolant systems of units 1, 2 and 4 and one by one these have come back into action. Unit 1 announced cold shutdown at 1.24 am today and unit 2 followed at 3.52 am.
 
Repairs at unit 4 are now complete and Tepco said that gradual temperature reduction started at 3.42pm. An evacuation zone extends to ten kilometres around the plant, but this is expected to be rescinded when all four units are verified as stable in cold shutdown conditions.

The perimeter radiation monitors have measured a whopping 15 uSv according to tepco (http://bravenewclimate.com/).  You get more standing next to a granite wall.

edit: You know what's really a problem?



Uploaded with ImageShack.us

edit2:  The news quote above is for Fukushimi Danii not Fukushima Daiichi.  My mistake.  Regardless, the cores are damaged, and thus an expensive loss, but the containment is by everyones reports fine.

[TripleDES]

I like how news outlets are shitting their pants about trace releases of Caesium-137 and Iodine-121. While this isn't something you'd actually want or need, their half-times are pretty low (30 years and 2 hours respectively) and it's still just trace amounts. Also, all coal power plants on Earth blow more Uran and Thorium into the atmosphere than there's nuclear waste each year, which no one seems to mind.

The perimeter radiation monitors have measured a whopping 15 uSv according to tepco (http://bravenewclimate.com/).  You get more standing next to a granite wall.

True story: I have a paranoid friend that went from long reading sessions on the toilet to ninja shitting, after I've proven to him that ceramics are radioactive.

[TripleDES]

Just more examples of irresponsible news outlets. The online version of a fairly well reputed news magazine posted an article online with a thick headline dubbed "West winds are causing radioactivity to drift seawards" (translated from German). Then when you read the article, it's just all hypotheticals. 

[NowhereMan]

The SA thread had a link to a piece about some town that's been pretty much replaced with toxic sludge from a nearby industrial plant that will probably make the soil and water in the area pretty toxic for years but the media is far more concerned that these reactors might end up releasing a year's worth of radiation in a single dose. Or not. But there are reactors and things melting down and maybe going critical so it's way more important than places actually being made dangerous to inhabit.

[pxib]

I like how news outlets are shitting their pants about trace releases of Caesium-137 and Iodine-121.

My father, for example, is apparently roaming from pharmacy to pharmacy looking for potassium iodide.

[Mrbloodworth]

I just hope that NE japan does not become uninhabitable, the wave crushed enough, they don't need another issue to contend with.

Oh, jeesus christ.

I wasn't being sensationalist, nor reacting to anything posted in here. It was simply a best wishes comment.


I'm not part of the "I'm an internet physicist" or "OMG Chernobyl" conversation going on in here.

[Merusk]

Nuclear reactors and the words Meltdown scare people. Mainly because they don't understand any of it beyond knowing "oh shit, that's bad."  Scared people read more web pages than concerned people who will empathize with toxic sludge or washed away cities, meaning more revenue.   Never forget this and be disgusted by it and what it's done to reporting.

[Nonentity]

Well, I just recently got on the whole meltdown tip, and this is the sanest link I've found to date, as far as information is concerned:

http://morgsatlarge.wordpress.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors/

Bullet point list after the large scientific explanation:

- The plant is safe now and will stay safe.
- Japan is looking at an INES Level 4 Accident: Nuclear accident with local consequences. That is bad for the company that owns the plant, but not for anyone else.
- Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants’ chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.
- There was some limited damage to the first containment. That means that some amounts of radioactive Cesium and Iodine will also be released into the cooling water, but no Uranium or other nasty stuff (the Uranium oxide does not “dissolve” in the water). There are facilities for treating the cooling water inside the third containment. The radioactive Cesium and Iodine will be removed there and eventually stored as radioactive waste in terminal storage.
- The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the “main” nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.
- The seawater will then be replaced over time with the “normal” cooling water
- The reactor core will then be dismantled and transported to a processing facility, just like during a regular fuel change.
- Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years.
- The safety systems on all Japanese plants will be upgraded to withstand a 9.0 earthquake and tsunami (or worse)
- (Updated) I believe the most significant problem will be a prolonged power shortage. 11 of Japan’s 55 nuclear reactors in different plants were shut down and will have to be inspected, directly reducing the nation’s nuclear power generating capacity by 20%, with nuclear power accounting for about 30% of the national total power generation capacity. I have not looked into possible consequences for other nuclear plants not directly affected. This will probably be covered by running gas power plants that are usually only used for peak loads to cover some of the base load as well.  I am not familiar with Japan’s energy supply chain for oil, gas and coal, and what damage the harbors, refinery, storage and transportation networks have suffered, as well as damage to the national distribution grid. All of that will increase your electricity bill, as well as lead to power shortages during peak demand and reconstruction efforts, in Japan.
- This all is only part of a much bigger picture. Emergency response has to deal with shelter, drinking water, food and medical care, transportation and communication infrastructure, as well as electricity supply. In a world of lean supply chains, we are looking at some major challenges in all of these areas.

[Murgos]

Nuclear reactors and the words Meltdown scare people. Mainly because they don't understand any of it beyond knowing "oh shit, that's bad."  Scared people read more web pages than concerned people who will empathize with toxic sludge or washed away cities, meaning more revenue.   Never forget this and be disgusted by it and what it's done to reporting.

A lot of people still think a 'meltdown' means that the molten fuel is going to melt its way to the center of the earth.  It's just not going to happen.

The meltdown that is being described here is the partial melting of the rods that enclose the uranium which is just going to leave a mess in the bottom of the containment vessel and means that there is no hope of salvaging the core and putting it back in use.

[Simond]

anti-scientific data conspiracy theories

The what now?

Arthur Baylis doesn't believe in climate change, and spammed the last ACC thread in politics with unresearched, borderline irrelevant quotes from dubious sources. Much like he is doing with this one re: nuclear science, in fact.

Let's just hope nobody starts an "Theory of Evolution" thread, eh? 

[Cyrrex]

The meltdown that is being described here is the partial melting of the rods that enclose the uranium which is just going to leave a mess in the bottom of the containment vessel and means that there is no hope of salvaging the core and putting it back in use.

Let me be the first, then, to propose alternate definitions.  Meltdown just seems to be too powerful a word for us to digest:

- Liquefied
- Caramelized
- Frothy
- Oozing
- Creamy
- Gushy
- Sopping

[Mrbloodworth]

Eviscerated?

[Soln]

another concern: has there been any (goldbug) chatter about JP defaulting on its soverign debt because of these disasters?

[Chimpy]

another concern: has there been any (goldbug) chatter about JP defaulting on its soverign debt because of these disasters?

The Japanese government has a great out on that though, they can just tell their creditors: "Go talk to the U.S.A., they owe us almost a trillion dollars."

[Khaldun]

For the folks who honestly know something about this specific field of engineering, here's a few things I'm wondering:

1) The experts who are insisting that there is nothing to be alarmed about here, everything is safe as houses, keep pointing out that the fuel rods are fully inserted and that there is no continuing reaction. How does this square with even the plant operators conceding that there may well have been partial meltdown of the fuel rods inside the reactor? E.g., if that happened, is it something that happened before insertion? If the fuel rods partially melted, would that have made it hard to control the reaction? Or is the melting they're talking about entirely from residual heating after the stopping of the nuclear reaction? Is that what the issue in reactor #2 is now? (TEPCO has reported that the fuel rods in #2 were exposed for over 2 hours earlier today without any coolant.)

2) Why is the containment vessel for each of these particular reactors so impervious to melting? Is it that the melting point of the rods is significantly lower than the containment vessel? Can the reaction inside get hot enough under any circumstances to melt the containment?

3) If the containment vessel for a reactor was breached during a partial or full meltdown on the bottom into soil or subsurface water, would contamination of the environment be as immediately obvious as it would be in a release of radioactive material into the atmosphere?

4) Is caesium-137 really not a big deal? If so, why is there an exclusion zone around Chernobyl, considering that most of that contamination is caesium-137 from an accident that took place 25 years ago?

5) The posting that Nonentity refers to is from an MIT professor whose specialization is the economics of supply chains and product development. He is basing his assessment on risk entirely on news reports like everyone else in this thread and the rest of the Internet. He has no particular expert knowledge of this reactor, none of nuclear engineering except through his family, and no particular contacts at TEPCO. So I guess my question is, why does he (and most of the other commenters, expert and otherwise) think that every pertinent detail that needs to be known about the accident is presently available to them? I promise you that if I went back to the news coverage about TMI, I'd find some experts saying that it wasn't a big deal, or that there was no need to be concerned, who it turns out were unaware of some of the most serious developments inside the facility.

[Sand]

anti-scientific data conspiracy theories

The what now?

Arthur Baylis doesn't believe in climate change, and spammed the last ACC thread in politics with unresearched, borderline irrelevant quotes from dubious sources. Much like he is doing with this one re: nuclear science, in fact.

Let's just hope nobody starts an "Theory of Evolution" thread, eh? 

No, I think Arthur is pointing out that the source of most of the "its okay nothing to see here" press releases are from the same company which has a notorious reputation for ignoring repairs and safety concerns. The same as some coal company telling you not to be concerned with that giant sludge fly ash pond a mile from the elementary school, and even if it is leaking into the ground water its safe! (Coal came from the ground originally after all!  )
And they continue to say this despite other claims that three or more cores are now in some stage of meltdown and they have no way of verifying anything.

I think everyone posting here hopes things turn out for the best, but some are hoping they arent hiding things which in turn could bring lots more pain and suffering to the local population.
Its concern and making sure things arent being ignored, not sensationalism.

[bhodi]

We're saying a "worst case" scenario is a billion dollar, local cleanup effort. There is another city, right now in Japan, that is covered in toxic sludge from a processing factory. The soil there will likely be toxic for decades. It's already a worse disaster than this will ever be. I'm just going to cut and paste from the OP of an informative SA thread instead of re-typing and re-prhasing it all. Links are obviously not working but you can google them if you really want, or pay :10bux:

Your answers are under/after "China Syndrome". This is another 3 mile island - that is to say, "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."

But first, a FAQ (updated at 8:15AM GMT, March 14th):


What in the hell 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 this photo. 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.

Here is a chart showing the effects of various radiation poisoning levels. For perspective, note that this chart starts 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.

Where can I find more information about these issues?

Reading:

Timeline and data sheets for the incident by the Nuclear Energy Institute
The International Atomic Energy Agency is providing regular announcements
Wikipedia on light water reactors and nuclear weapon design
The United States Nuclear Regulatory Commission's Boiling Water Reactor (BWR) Systems manual - the Fukushima reactors are BWRs, a subset of LWRs
More about BWRs
Tokyo Electric Power Company site with press releases - currently hard to reach due to traffic

Video:

"Physics for Future Presidents" lecture ten, on nuclear weapons and nuclear reactors
Footage of the hydrogen explosion at reactor #1

Photos:

before and after satellite photos of Fukushima site one

[Cyrrex]

I think everyone posting here hopes things turn out for the best

No, I actually suspect that's not the case.  Most, sure, but probably not all.  This is a world that turns, after all, on things NOT turning out for the best.

[ghost]

Japan nuclear disaster risk seen receding fast.

This sounds like good news.   

A natural decaying process means that the amount of heat the fuel produces has fallen dramatically, by more than 90 percent, experts said on Monday.

[Sand]

Bhodi,

Quoted from your paste-

One of the safe sources of information is the TEPCO site

Again do you not see the similarity of turning to TEPCO for information like turning to BP for information about the oil spill? Or the coal company for information about the safety record of the mine that just collapsed?


Also noted some other discrepancies with that info dump such as,

This is due to their light water reactor design.

arent the reactors in emergency status actually BWR designs? That was but the first of a few and didnt feel like dissecting the entire post.

No, I actually suspect that's not the case.  Most, sure, but probably not all.  This is a world that turns, after all, on things NOT turning out for the best.

Maybe other places but here in this forum? We might all fight and argue with each other like a bunch of bitter hens, but I have more faith in the posters here than that.

[Khaldun]

One thing in the FAQ that Bhodi posted that struck me as important, and not to just be waved off: decay heat is enough to melt the containment. Ok, so it's not a "China Syndrome" situation with an uncontrolled reaction continuing outside of containment. But it's still something that would involve more than trivial contamination of the environment around the reactor.

I'm just feeling a bit unconvinced by the nonchalance of some of the experts about the situation, without having any desire to buy into omg it's Chernobyl all over again hysteria. I get the sense that there's an excluded middle here where there's an appropriate concern to be expressed--and some appropriate skepticism about the expertise being used to assess the situation (on both sides of the assessment).

I'm also unconvinced by the argument that because there are worse situations elsewhere that don't involve nuclear contamination, nuclear contamination is no big deal. That's a logic I don't particularly buy no matter what the issue is at hand, because no matter what you're concerned about, I can one-up you by pointing out that there's some comparable thing that's far worse than it which you have not addressed.

[Arthur_Parker]

Arthur Baylis doesn't believe in climate change, and spammed the last ACC thread in politics with unresearched, borderline irrelevant quotes from dubious sources. Much like he is doing with this one re: nuclear science, in fact.

Let's just hope nobody starts an "Theory of Evolution" thread, eh? 

Your dislike of me is on record as it was previously when you wanted me hell banned, I'm not going to respond by dragging politics stuff out here.  But just to be clear, you have a problem with me, I don't have a problem with you.