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Two plants near Tokyo, each with multiple reactors are on the verge of meltdown after emergency backup cooling was shut down by loss of power due to flooding.  (Source: CNN)

An explosion damaged the roof of one plant, releasing radiation on Saturday.  (Source: Reuters)

The plants lie within the Tokyo metropolis. People are being evacuated from within a 20 km radius.  (Source: CNN)
Japanese nuclear disaster is cause for pause, reflection

The Sendai Earthquake struck Japan early Friday morning with unrelenting fury.  Measuring 8.9 to 9.1 Mw-megathrust the quake was among the five most severe in recorded history and the worst quake to hit Japan.  In the aftermath of this severe disaster, as the nation searches for survivors and contemplates rebuilding, an intriguing and alarming storyline has emerged -- the crisis at the Fukushima Daiichi nuclear plant.

You may recall that a few years back Japan was struck by another quake which cracked the concrete foundation of a nuclear plant, but yielded virtually no damage.

By contrast, this time the damage was far worse, creating what could legitimately be called a nuclear disaster.

I. Fukushima Daiichi - a Veteran Installation

The Tokyo district of Fukushima is home to two major nuclear power installations.  

In the north there is the Fukushima "Daini" II plant, which features four reactors -- the first of which went online in 1982.  These units produce a maximum of 4.4 GW of power and are operated by the Tokyo Electric Power Company.

To the south lies the Fukushima "Daiichi" I plant, a larger and older installation featuring six reactors, the first of which went online in 1970.  Operated by Tepco, the installation offers a combined 4.7 GW of power.  It was here that disaster struck.

II. Disaster at Fukushima Daiichi 1

While the southern installation is over four decades old, Japan has been responsible in retrofitting the plant with modern safeguards.  Among those is an automatic switch which shuts off the reactor when an earthquake struck.

The switch performed perfectly when the quake hit Friday morning, shutting of the three reactors that were active at the time.  Control rods lowered and the reaction stopped.

The next step was the cooling the power rods, composed of uranium-235, to prevent them from melting.

Cooling water was pumped over the rods for about an hour, but before the rods could be fully cooled, stopping the reaction, the pumps failed.  According to the International Atomic Energy Agency, and multinational oversight group, the failure was due to failure in the backup generators due to the tsunami flooding.

On Saturday Japanese authorities and power officials tried to use sea-water injections to complete the cooling process, but those plans were stalled when another tsunami warning arrived.

An explosion occurred inside at least one of the reactor buildings.  It is believed to be due to the build-up of pressure after the pumps failed creating hydrogen and oxygen gases, which subsequently combusted from the heat.

Malcolm Grimston, Associate Fellow for Energy, Environment and Development at London's Chatham House told CNN:

Because they lost power to the water cooling system, they needed to vent the pressure that's building up inside.My suspicion is that as the temperature inside the reactor was rising, some of the metal cans that surround the fuel may have burst and at high temperature, that fuel cladding can react with water to produce zirconium oxide and hydrogen.

That hydrogen then will be part of the gases that need to be vented. That hydrogen then mixes with the surrounding air. Hydrogen and oxygen can then recombine explosively. So it seems while the explosion wasn't directly connected with the nuclear processes, it was indirectly connected, because the hydrogen was only present because of what was going on in the reactor core.

The explosion damaged the roof of the plant and sent billows of smoke up into the air.  According to officials some radioactive material was released into the atmosphere.  Outside the plant perimeter, levels of radiation measured 8 times higher than normal.

Meanwhile reactors at the newer Fukushima II are also beginning to heat up after their own cooling systems failed.

Japanese officials have evacuated people from an expanding radius around the plants as a precaution.  Currently the evacuation zone is at almost 20 km.  They hope to try to continue cooling, but have to work around tsunami alarms from earthquake aftershocks that have continued into Saturday.  U.S. Secretary of State Hillary Clinton has announced that the U.S. is sending high-tech coolant to the plants, in and attempt to avert disaster.

III. Can a Meltdown be Avoided?

Without proper cooling, the rods will continue to heat and proceed towards meltdown, releasing clouds of radioactive gas.  The first question is thus whether meltdown can be avoided.

At the Fukushima I plant, radioactive cesium was discovered.  Cesium is in the beta decay chain tellurium -> iodine -> xenon -> cesium.  Its occurs roughly 16 hours after an unchecked uranium reaction and its presence indicates that one of the fuel rods may already have melted down.

Once one rod melts, it will be much more difficult to prevent the others from melting down as well.

According to reports, the coolant temperatures inside the reactor have exceeded 100 degrees Celsius.  If they reach 540 degrees Celsius the fuel rods will fully melt down.

The question now becomes what to do.  

According to reports by Nippon Hoso Kyokai (Japan Broadcasting Corporation), three individuals have already been exposed been the victims of radiation poisoning (likely plant workers) and that radioactivity levels at the plant have risen to 1,000 times the normal levels at the plant control room.

One option on the table is to vent the reactors, allowing them to blow off the steam and prevent a greater buildup of pressure and heat.  However, doing so could release significant levels of radioactivity into the surrounding area.

The alternative is to try last ditch cooling and hope that if the rods do melt, that the secondary containment will hold.  The release of radioactive gases from venting would pale to that if the secondary containment was breached.  Such a scenario would likely result in the modern day equivalent of Chernobyl.

Whichever course of action is selected, there's a great deal of risk of radiation exposure to those who inhabit the area in the near future.  States James Acton, international physicist, in an interview with CNN, "There's a possibility of cancer in the long term -- that's the main hazard here."

IV. Grim Lessons From the Disaster

At Three Mile Island, the U.S. learned the hard way not to put vital controls in the hands of plant operators.  Operators almost created a meltdown, when they accidentally disabled necessary cooling.  That was due to the poor quality of indicators. 

As the result, the nuclear community learned to automate shutdown processes.

Ultimately the Fukushima disaster illustrates the need for sealed backup generators.  The containment procedures in all their modern glory are useless if the backup power goes out.  And, if possible, it shows that it is desirable to build new nuclear plants farther from the sea and from fault lines (though this could cause costs to increase).

As the fight to avert meltdown plays out, the final damage won't be known for weeks to come.  But the international community is already reacting.

At this time it's vital not to overreact to this worse case scenario.  

The disaster does illustrate that nuclear fission power is far from failsafe, particularly older reactors -- even if retrofitted with modern controls.  Ultimately the international community needs to work towards fusion power, which should be much safer and cheaper.

At the same time, it's important to consider that there's a great deal of background radiation released from the burning of fossilized coal and that mining fossil fuels has led to many a great loss of life and resources as illustrated by recent coal and oil disasters.

And nuclear power is far less expensive than solar or wind power in base costs, and generally less expensive even after all the red tape that increases plant creation costs by an order of magnitude in the U.S.

There's no easy answers here.  Oil and coal power emit dangerous nitrogen and sulfur-containing gases and carbon dioxide into the ozone.  And their fuel is dangerous to obtain.  But they're cheap.  Solar and wind power are relatively safe, but they're expensive and offer inconsistent power.  Nuclear power is cheap and produces no emissions normally, but it can be a danger in the case of natural disaster or malicious attack.

It's important not to turn a blind eye to this disaster, but it's equally important not to overreact.


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A bad placement decision on Japan's part....
By someguy123 on 3/12/2011 4:04:30 PM , Rating: 5
This will delay nuclear another century. People are so nonsensically afraid of nuclear already and this will just be used as "proof" of the downsides of nuclear.

Hope this doesn't come off as Japan bashing. I wish them nothing but the best and hope this disaster end soon.




RE: A bad placement decision on Japan's part....
By Lerianis on 3/12/11, Rating: 0
By TennesseeTony on 3/12/2011 5:12:47 PM , Rating: 2
Best case scenario, this reactor, ALL reactors, affected will be safely shutdown. Perhaps if that happens, it will actually bolster the safety image of nuclear power, having survived a 8.9 earthquake AND a tsumami. Yeah, I'm dreaming, I know. :)

Separate topic:

As to the 1000x greater radiation level in the control room, hmm, that's a concern, definitely got something leaking. As to the 8x increase in external radiation, (I likely am wrong, but) aren't 'normal' radiation levels outside a nuke plant as close to zero as it is sitting at your desk reading this?


By vol7ron on 3/12/2011 7:35:30 PM , Rating: 1
No, I think there is normally a small circumference of higher radiation surrounding the plants, due to the extreme heat, though these levels are still considered non-fatal, much like the contamination from sitting at your desk (or living in a brick house).

All-in-all, this is a very sad situation. I'm somewhat surprised as china and japan have done very well with earthquake-proofing their structures.


RE: A bad placement decision on Japan's part....
By spread on 3/12/2011 7:41:49 PM , Rating: 2
quote:
1000x greater radiation level in the control room


The control room had almost no radiation to begin with. 1000x more than than almost zero radiation. Nothing major to be concerned with.

quote:
aren't 'normal' radiation levels outside a nuke plant as close to zero as it is sitting at your desk reading this?


If the plant is built to proper standards and maintained well, yes.


RE: A bad placement decision on Japan's part....
By Solandri on 3/12/2011 7:52:00 PM , Rating: 4
From the numbers I've been able to gather, the "1000x higher" radiation level in the control room was about the same as getting a chest x-ray every 1-2 hours. Not fatal, but definitely not a place you want to stay in for an extended period of time.


By paydirt on 3/14/2011 2:55:35 PM , Rating: 2
SO FAR, calling this a disaster is irresponsible in the least because the press is causing people to panic about this. A meltdown would be caught in the third level of containment. The only "disaster" part of this is the loss of electrical generation.


RE: A bad placement decision on Japan's part....
By BZDTemp on 3/12/11, Rating: -1
RE: A bad placement decision on Japan's part....
By bbomb on 3/12/2011 9:33:54 PM , Rating: 4
And I say enough of the no nuclear ever propaganda. Its benefits outwiegh the risks if you ask me. Some places would never have power if it wasnt for the nuclear option. The only stupid decision in this case was to put a nuclear power plant next to an ocean on top of a fault line. Brilliant thinking there. Once again it isn't the technology that makes it dangerous is the human component that does.

I still can't believe they didn't have fully protected dedicated backup power to the shutdown systems given their history with floods and earthqaukes.


By Breakfast Susej on 3/14/2011 11:19:19 AM , Rating: 2
It is always the human element that leads to problems.

I have a bit of an obsession with Chernobyl and thus I have spent a lot of time watching documentaries, reading about it, etc.

It actually would have been more astound had there NOT been a disaster at Chernobyl given the comedy of errors and human stupidity that led to the disaster. That isn't even taking into account the very poor design of the RMBK reactor in question.

Chernobyl was akin to pouring five gallons of gasoline on some dry tinder, having a drunken monkey with a torch dance around it, and then questioning how on earth the pile of dry tinder caught on fire.


RE: A bad placement decision on Japan's part....
By Solandri on 3/12/2011 11:46:12 PM , Rating: 5
quote:
When something goes wrong with gasoline production it does not affect people living a thousand miles away or more.
...
Oil spills and fires at refineries can be bad but they are nothing compared to how bad Nuclear disasters can get so enough with the pro-Nuclear propaganda.

And when a car crashes, it is nothing compared to how bad a plane crash can get. Yet cars are still more dangerous than planes. How can that be?

It's because you're cherry-picking a specific subset of incidents (or in this case, one incident) where nuclear accidents are more dangerous than gasoline refining. If you look at all the cases - the entire history of each power generation technology between two specific dates - you find that not only is nuclear safe, it's safer than any other power source we've invented. That's right. Per unit of energy produced, nuclear is safer than coal, gas, hydro, wind, and even solar. All of them have killed more people per GWh of energy generated than nuclear.
http://nextbigfuture.com/2008/03/deaths-per-twh-fo...

So basically, your argument boils down to: Because nuclear could kill a whole lot more people in a single incident, we should use other technologies which will kill a whole lot more people than nuclear. That makes no sense if your goal is to save lives.


By karlostomy on 3/13/2011 12:51:52 AM , Rating: 5
+6 Solandri.

The only problem with your excellent post is that the people who really need to read it, will likely not do so, and even if they do, will ignore it in favour of their own established anti-nuclear bias.

Ironically, the people who don't need to read it, do.


RE: A bad placement decision on Japan's part....
By chrnochime on 3/13/11, Rating: -1
RE: A bad placement decision on Japan's part....
By Scabies on 3/13/2011 1:58:14 AM , Rating: 3
people seem to lump all nuclear events into the Cherynobyl category, what with the catastrophic explosions and uncontrollable fires and lie-till-they-die government coverup.

Nuclear reactors in "civilized" nations are designed to be self-contained in the event of a fully screwed pooch. If a meltdown occurs and the reactor is lost, its NOT going to create a ghost town of radiological quarantine. The reactor sits within a containment vessel that, unless breached by explosion or environmental damage, will hold all the fun stuff inside. (note that the explosion video is a hydrogen explosion outside the reactor building, which this article is somewhat misleading about.) Venting steam might have some of the core products in it, but once the water runs out and everything turns to magma, they just seal it and walk away. Three Mile Island, also a light water reactor (though pressurized as opposed to boiling) still has a working reactor today (TMI-1) and there's no exclusion zone.

tl;dr- until the building explodes, there really isn't any danger unless you're sitting under the steam clouds they periodically (and temporarily) vent. and the building isn't going to explode.


RE: A bad placement decision on Japan's part....
By MPE on 3/14/2011 3:17:03 PM , Rating: 2
Well we are about 1 step away from 2 buildings blowing up and releasing bad stuff.

It is fucking terrible but this is the reality. We can do the blame game later but for now, we hope Japanese and her citizens are OK.


RE: A bad placement decision on Japan's part....
By JediJeb on 3/15/2011 12:57:14 PM , Rating: 2
Even if the buildings blow up, which they have already, you still are not losing the containment on the reactor only the shell of a building that surrounds that containment unit. Except for the cooling units, everything else at the plants is working as it is supposed to when something like this happens. Had the backup generators been protected from the sea water these plants would probably not had much of a problem at all. That is one design feature that can now be improved on all other nuclear plants around the world to make them even more safe.


By MPE on 3/16/2011 9:46:50 AM , Rating: 2
As of today, there is a possibility you may need to revise your thinking.


RE: A bad placement decision on Japan's part....
By Solandri on 3/13/2011 3:23:33 AM , Rating: 5
quote:
what it boils down to is that an area contaminated by nuclear meltdown is uninhabitable for *much* longer than any other kind of power plant destroyed. That and the widespread effect on people and the wildlife is much longer lasting as well.

You're making the same mistake I just pointed out. You're looking at a specific risk instead of overall risk. Chernobyl resulted in about 336,000 people evacuated. Pollution from coal plants is estimated to kill 100,000 people each year in the U.S. 100,000 people killed each year vs 336,000 people evacuated in 65 years. Yet people shrug at the pollution billowing out of a coal plant's smokestacks, while they freak out at the mere presence of a nuclear plant. Why?

Because if there's a serious nuclear accident, the harm is concentrated in a small area and thus avoidable by declaring the region uninhabitable. When you operate a coal plant, the harm is spread all around and avoidable. Just running the things normally is much more dangerous than the worst nuclear accident in history. But because you can't avoid the air pollution there is no evacuation, no declaration of contamination, no keep out signs.

quote:
If you find nuclear power plant so safe, are you living near one already?

I have no problem living next to a nuclear plant. I am looking to buy a house near the San Onofre plant because I like the area. I hear the fishing near its warm water oulet is pretty good too.

If you're so afraid of nuclear power, here are some other risks you should take steps to minimize:
http://www.flatrock.org.nz/topics/older_and_under/...

Nuclear accident: 1 in 10,000,000 chance of dying
Scalding: 1 in 5,000,000
Food poisoning: 1 in 3,000,000
Falling out of bed: 1 in 2,000,000
Drowning in bath: 1 in 685,000
Work accident: 1 in 43,500
Car crash: 1 in 8,000

All of these are more likely to kill you than a nuclear power accident. So if you think nuclear power is too dangerous to use, then I assume you aren't doing any of these other things which are even more dangerous. You must not use hot water, you must grow/harvest/prepare all your own food, you must sleep on the ground, you must not take baths, you must not work, and you must not drive/ride in a car.

Do you do any of these things? If you do then you need to stop doing them, or you need to reassess how dangerous you think nuclear power is.


By Solandri on 3/13/2011 3:25:16 AM , Rating: 2
quote:
When you operate a coal plant, the harm is spread all around and avoidable

Obviously that should be "unavoidable".


By monitorjbl on 3/14/2011 3:12:56 PM , Rating: 2
quote:
Nuclear accident: 1 in 10,000,000 chance of dying Scalding: 1 in 5,000,000 Food poisoning: 1 in 3,000,000 Falling out of bed: 1 in 2,000,000 Drowning in bath: 1 in 685,000 Work accident: 1 in 43,500 Car crash: 1 in 8,000


Just to play devil's advocate, the chance for nuclear accidents would go up as more reactors are brought online. Not that I buy into any of the FUD about nuclear power, just pointing out that your numbers are not static.


By someguy123 on 3/13/2011 3:59:57 AM , Rating: 2
Even with meltdowns causing areas to become completely uninhabitable, and issues with radiation spreading far distances, nuclear power has still, by far, killed the least amount of people out of all power sources.

Nuclear still accounts for about 6% of total global energy. It's not like we merely stopped using nuclear after Chernobyl. I'm sure there are plenty of people who receive nuclear power and don't even realize it. Even though it's a source that generates quite a bit more power than "green" sources it still kills significantly less people than all of these sources combined.


RE: A bad placement decision on Japan's part....
By kattanna on 3/14/2011 1:37:16 PM , Rating: 1
quote:
If you find nuclear power plant so safe, are you living near one already?


do you own a cat or eat bananas?

cause if so, you are exposed daily to more radioactivity then you will find living next to a nuclear plant

knowledge.. look into it ;>)


RE: A bad placement decision on Japan's part....
By sascham on 3/14/2011 8:27:50 PM , Rating: 1
Totally missed the point. The point is that however safe the plant is when operating properly, accidents can occur no matter how many safeguards are put in place.


By JediJeb on 3/15/2011 1:00:26 PM , Rating: 2
True, but a meteorite can also fall from the sky and hit you on the head and kill you, but you don't see everyone wearing Kevlar helmets.


RE: A bad placement decision on Japan's part....
By BZDTemp on 3/13/11, Rating: -1
RE: A bad placement decision on Japan's part....
By JediJeb on 3/13/2011 6:41:42 PM , Rating: 2
quote:
Also expecting the world to be rational is futile. Look at how much money is being spend on countering terrorism - if that money was instead spend fighting pollution and improving traffic safety the results would be much better.


We could all be breathing clean air when the terrorist blow us up while driving safely in our better cars. If we can't expect the world to be rational, don't you believe we need money spent on counter terrorism? The terrorist are the non rational people out there, not the ones trying to protect us from them.

quote:
Heck, the money could be spend building schools, providing the most basic health care and thus making the whole world a better place (and likely make many wannabe terrorists into happy productive people).


Osama Bin Laden was a very rich. well educated man, yet that didn't stop him from becoming a chief among terrorists. You can educate everyone to the level of Einstein and there will still be some of them who if you pay their way in everything will be lazy and simply let others do the work and leach off the more productive ones. Anyone who believes that the only reason there are bad people in the world is because those people didn't have enough food or comforts of life are sadly mistaken and probably also believe in magic pixie dust and unicorns. Some people will be bad because they want to be regardless of their situation in life, and others will be good in spite of their situation in life. There is no magic solution to all of the worlds problems.


RE: A bad placement decision on Japan's part....
By tastyratz on 3/14/2011 10:26:12 AM , Rating: 3
I believe what the OP was trying to express is that he believes the most quantifiable gains will result from better use of funding.

I agree to a point as well (maybe not that extreme), we clearly are mismanaging funds and putting more towards things where it is not necessary. The "war on terror" is a label for what has become the largest pork barrel of unnecessary expenditures in existence.
While I might not think we should be building schools along the world the US is just as much an evil machine when it comes to the military as any other, we just hear less about it because of the propaganda. War is ugly any way you put it, and we create these bitter individuals and extremists by making a mess and not cleaning it up. There will always be extremists and those who are angry at the world no matter what country they are in, but the idea is to minimize the number of ant hills we step on along the way. The greater the quality of life individuals have, the less they have to be bitter about. The more educated people are, the more likely they are to make intelligent choices. These things result in a greater per capita rate of satisfaction


By Spuke on 3/15/2011 1:27:36 PM , Rating: 2
quote:
There will always be extremists and those who are angry at the world no matter what country they are in, but the idea is to minimize the number of ant hills we step on along the way.
I guess the next question is, who determines what is satisfactory?


By Dr of crap on 3/14/2011 12:55:16 PM , Rating: 2
I here your objections but do you have proof of this, your statement -
"A worse case Nuclear accident will touch the lives of millions and it can make nations uninhabitable for countless years"

I don't know of one nation that is black, desolate and can't be lived on. Do you?


By 3DoubleD on 3/14/2011 10:41:26 AM , Rating: 2
While I agree with your general point, that "study" you linked to is pretty ridiculous. Saying solar power kills people because roofers generally disregard workplace safety is absurd. If the roofers were too stupid to follow appropriate safety procedures and fell off the roof then that's their own problem. If large skyscrapers can be built without deaths, I think solar installations on residential houses could also be done without fatalities. Following the study's ridiculous reasoning, it would probably be correct to say that hanging Christmas lights on your house is more dangerous than nuclear power, just because some idiots fell off their ladders.


By AstroGuardian on 3/15/2011 7:04:04 AM , Rating: 2
+6


By Iaiken on 3/12/2011 6:23:20 PM , Rating: 4
The problem is that people at large are ignorant to the difference between light water reactors like this one that require volatile highly enriched fuel rods and heavy water moderated reactors that don't.

People will simply see the word Nuclear Reactor and be flooded with negative emotions and fears that are nothing more than products of their own ignorance.

This is most unfortunate for everyone and not just Japan. It is my sincerest hope that they can not only overcome this problem, but take away valuable lessons for improving other reactors.


By mikeyD95125 on 3/12/2011 6:30:06 PM , Rating: 2
This is actually a case for investment in new nuclear plants. The new reactors need energy input to sustain fission so if the power is cut the reaction dies out automatically. The reactors that are in trouble are the older style ones that depend on humans controlling the rate of fission from getting above a safe threshold.

Naturally this information will probably not enter in the arena as people will have ignorant debates for the next few weeks about the merits of nuclear power.


RE: A bad placement decision on Japan's part....
By JonB on 3/13/2011 3:26:12 PM , Rating: 2
quote:
The new reactors need energy input to sustain fission so if the power is cut the reaction dies out automatically.


The new reactors you are talking about are test versions or demo versions, some barely past computer simulations or sub-megawatt power levels. They are not commercially viable or available. The German attempts are all de-commissioned.

Commercially usable power needs to be in the 100's of megawatt or gigawatt range.

Look up Pebble Bed reactors on wikipedia.


RE: A bad placement decision on Japan's part....
By MozeeToby on 3/14/2011 12:05:24 PM , Rating: 2
There are simple and effective solutions in use today that guarantee a reactor shutdown if coolant power is lost. Simply suspending the control rods above their slots via electromagnets is probably the simplest. If the magnets lose power the control rods drop into the reactor and bring the nuclear reactions to a stop (or near enough anyway).

Incidently, the author of this article, and most of the people commenting on it, clearly don't understand what the term 'meltdown' means. It just means that the fuel is melted by it's own heat. It doesn't mean an explosion or even a release of radioctive material. In the design that is having problems in Japan, all that a meltdown means is a puddle of nuclear fuel on the bottom of the containment vessel. A pain to clean up no doubt, but unlikely to be of concern to the general public.

Now that they've given up on salvaging the reactors and flooded them with boronic acid, nuclear reactions have essentially come to a stop, all that is happening is the residual heat is causing a hydrogen buildup which is 'exploded' in a semi-controlled way to prevent a more significant failure. Very little is happening in terms of the issues they are experiencing which wouldn't have been predicted by their engineers in the event of a power loss and backup failure.


By JonB on 3/15/2011 6:04:22 PM , Rating: 2
quote:
There are simple and effective solutions in use today that guarantee a reactor shutdown if coolant power is lost. Simply suspending the control rods above their slots via electromagnets is probably the simplest. If the magnets lose power the control rods drop into the reactor and bring the nuclear reactions to a stop (or near enough anyway).


Current PWRs already use electromagnetics of several designs to hold both control rods and safe shutdown rods in the OUT position. If power is lost for any reason, the rods fall into place as you describe. Once in, they will suppress neutrons to the point that the core cannot support fission. The only heat will be decay heat.

BWRs insert their rods from the bottom. They use a hydraulic control unit with a pressurized storage tank to rapidly insert the control rods (about 4 seconds) upon any interruption of the electric current.


RE: A bad placement decision on Japan's part....
By superPC on 3/12/2011 10:17:18 PM , Rating: 4
or we can move past this and see things in perspective. there's more than two power plant in the area. the others don't have as much problem as this one, and this only has problem with one reactor out of several. amazing isn't it? with the latest technology a nuclear power plant can get hit by the 7th biggest earthquake in recorded history AND hit by a TSUNAMI not counting numerous aftershock and only 1 of its reactor is facing a meltdown (and still a few ways away from meltdown). if the designers has the foresight to fully isolate the backup generator none of this condition would have happened. i say this is a triumph of nuclear technology, not a failure.


RE: A bad placement decision on Japan's part....
By PrinceGaz on 3/13/2011 8:22:28 PM , Rating: 1
It's actually 3 of the 7 are in trouble now, and the authorities seem to have decided to scupper them by flooding them with seawater, rather than risk a major radioactive release. Given the cost of building a nuclear power-station, that is a pretty expensive choice, which suggests it was/is either right them off or something much worse could happen given the cooling system problems. The much worse being a total core meltdown and breach of the inner containment chamber resulting in a release of large amounts of highly radioactive material on a Chernobyl scale.


RE: A bad placement decision on Japan's part....
By Solandri on 3/14/2011 4:20:44 AM , Rating: 5
The plant was actually scheduled for decommission in a couple weeks. I'm hearing now that the government granted an extension on its use last month. But still, it's nearing the end of its expected useful lifespan (various internal structures tend to become more brittle over decades of irradiation). So it's not exactly a huge loss to kill it this way like the media is making it out to be. I've stopped counting the number of times I've had to roll my eyes every time they try to over-dramatize what's going on.

Normally you cool these things with deionized water to stave off corrosion (heat + ionized water = really bad corrosion). Because the cooling system isn't functioning, they've been having to vent steam to cool it, which means they're losing water. They probably used up their entire supply of deionized water, forcing them to resort to seawater.
quote:
The much worse being a total core meltdown and breach of the inner containment chamber resulting in a release of large amounts of highly radioactive material on a Chernobyl scale.

Sigh. This type of reactor can't release radioactivity on a Chernobyl scale. No western reactor can. Chernobyl's reactor was an inherently unstable design. You had to actively work to keep its power from spiking out of control. That's why it exploded instead of simply melting. Many of the radioactive isotopes produced in a fission reactor are normally too heavy to become airborne, but the explosion and graphite fire provided a vehicle for those particles to become airborne.

The uranium in this reactor is already sub-critical. It is not fissioning anymore. The heat they're trying to get rid of is being generated by they decay of short-lived radio-isotopes created by the fissioning process prior to shutdown. The primary concern with this reactor are isotopes which can become airborne (iodine) or are water-soluble (cesium). Every time they vent steam to cool the reactor, it allows these airborne and water-soluble isotopes to escape. There is no graphite inside, nothing which can catch fire or cause an explosion*, and the containment vessels are specifically designed to contain a worst-case meltdown. So the worst-case would involve dumping lots of water and neutron absorbers like boron onto a completely molten core. None of this stuff can catch fire, so the only vehicle for radioactivity to escape is still airborne or water(steam)-borne.

The reason they are so concerned about melting (as opposed to a meltdown) is because the fuel is surrounded by a zirconium cladding which keeps the fuel and isotopes created by fission on the inside, while the water stays on the outside. This is what lets you cool the core with water without picking up any radioactive iodine or cesium. If part of the fuel melts, the cladding melts with it, and the containment it provides is breached. That allows the water to directly contact the fuel, pick up water-soluble isotopes and mixing with airborne isotopes.

No melting = no radioactive iodine and cesium released when you vent steam.
Melting = radioactive iodine and cesium released when you vent steam.

*The hydrogen comes from a reaction between the water and zirconium. If the temperature becomes high enough, the zirconium disassociates the water into hydrogen and oxygen. Hydrogen molecules are really small so can leak through things which are otherwise water- and air-tight. So it leaked out and collected in the roof of the building. Some time later, a spark caused it to react with airborne oxygen, causing the explosions. Otherwise, it should be released into the atmosphere via the regular venting they're doing. As long as you're venting, it doesn't threaten the containment vessel.


By 3DoubleD on 3/14/2011 11:03:10 AM , Rating: 2
That is the best explanation I have yet read. THANK YOU!

I've studied different reactor designs (Candu heavy water) in the past and so I was unfamiliar with the design of the Japan reactor. Also, I kept thinking there was a contradiction in the news reports where they would say the reaction was stopped, but heat was still being produced. I had forgotten about isotope decay!

So it would appear the best case scenario is then to keep cooling the fuel for several half-lifes of the fission by-products while keeping the Zr tubes cool enough to prevent excess hydrogen build-up. By minimizing high temperatures they minimize the venting requirements and the less radiation released.

So is it safe to say that one or more of the Zr fuel tubes have melted if the release of steam causes an increase in environmental radiation levels?


By cpeter38 on 3/14/2011 12:28:33 PM , Rating: 2
Excellent description!!

Check out http://bravenewclimate.com/2011/03/13/fukushima-si... for a more detailed explanation of the situation.

Solandri,
You appear to either work in the industry or do good research.

Thank you!!


By ApfDaMan on 3/13/2011 1:28:52 AM , Rating: 3
I Agree, I have seen far too many comments on news websites using this incident as an argument against nuclear power, saying it is too dangerous. You know what is too dangerous? Not strategically placing nuclear power plants away from disaster prone areas. The real danger here is overthinking these possibilities.


RE: A bad placement decision on Japan's part....
By MartyLK on 3/13/2011 11:16:42 AM , Rating: 2
Nah...what it will do is increase efforts for an alternative, as stated, such as fusion. Ppl tend to be limited in their imagination about outcomes. There are always alternatives to be explored.


By JediJeb on 3/13/2011 11:48:38 PM , Rating: 2
I think it would talk quite a lot of research to make fusion feasible if it ever can be. Currently it takes more power to create fusion than it produces doesn't it?


By Hiawa23 on 3/14/2011 8:04:45 AM , Rating: 2
I see the political rhetoric has started about halting any production on nuclear plants in the US, as a result of what's happening in Japan, which is sad. I am not saying nuclear is the only answer but perhaps we can learn from Japan & put some safeguards in place that might not be in place that might reduce the chance of this happening here. we need to find alternate methods of producing energy under every stone.


By cpeter38 on 3/14/2011 12:18:15 PM , Rating: 2
Unfortunately, you are probably correct.

I wish Jason had posted a more matter of fact summary of the situation. Brave New Climate (http://bravenewclimate.com/2011/03/13/fukushima-si... has a much better summary.

Here are a few highlights:

"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."


By sascham on 3/14/2011 8:33:36 PM , Rating: 2
And where do you suggest Japan place their nuclear power plants that would be totally safe? The reason you are worried this will negatively impact the nuclear movement is that it is a totally rational response to the event. To suggest that this reaction is nonsensical is nonsensical itself.


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