Chernobyl was a completely different design, which allowed the core itself to overheat and explode.

Fukushima is a completely different design, and:
1) the core chain reaction has already been slowed or stopped completely.
2) Internal containment of the core and its long-term radioactive materials remains intact.

The water being pumped in is in secondary containment, to carry off the residual heat. This water is only moderately radioactive. Similarly, the radioactive gases released so far decay rapidly. The long-term radioactive materials - uranium and cesium - are still contained.

Fukushima is 40 YEAR OLD TECHNOLOGY.
Using this incident to sow panic about nuclear energy is dishonest.

Modern nuclear plants are smaller, safer, and more efficient than Fukushima.

According to this article:

http://www.nytimes.com/2011/03/14/world/asia/japan-fukushima-nuclear-reactor.html

radioactive releases of steam from the crippled plants could go on for weeks or even months.

Pentagon officials reported Sunday that helicopters flying 60 miles from the plant picked up small amounts of radioactive particulates — still being analyzed, but presumed to include cesium-137 and iodine-121 — suggesting widening environmental contamination.

Japanese reactor operators now have little choice but to periodically release radioactive steam as part of an emergency cooling process for the fuel of the stricken reactors that may continue for a year or more even after fission has stopped.

As one senior official put it, “under the best scenarios, this isn’t going to end anytime soon.”

Brief video of the explosion at reactor 3:

http://www.youtube.com/watch?v=T_N-wNFSGyQ&feature=player_embedded

The NYT article is not inaccurate Snoopy - but it still manages to be a sensationalist piece of crap. Yes, they're venting slightly radioactive steam. If that worries you, don't live anywhere near a coal fired power plant, or work in a building made of granite.

Lots of juicy technical detail here

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

If anything, we should be applauding the operators of the plant - they got hit with the worst of circumstances and they've still handled it. Flooding with seawater is going to totally fuck the equipment up, but they've done it anyway.

Worry about the tens of thousands of people without food, water, or shelter instead.

Interesting that the people who are most afraid of nuclear *power plants* are generally also the ones least-bothered by the prospective Iranian possession of nuclear *weapons*.

Amy, I'm late for work and was out when you posted this, but I have a short story on how fission plants work which might shed some light on what's going on. Most of the commentators are selling Kleenex. Yes, it's serious, but after an 8.9-9.0 earthquake that moved the whole nation, it's better to have some perspective and not whine that force fields didn't spring up to preserve the flowers and bunnies. I'll post about 3 PST.

As Rad implied - the REAL story here is that 40 year old technology still contained the mess after an unanticipated disaster.

picked up small amounts of radioactive particulates — still being analyzed, but presumed to include cesium-137 and iodine-121 — suggesting widening environmental contamination

Translation: We have no idea whats going on, we have no idea what kind of particles were detected, but were assuming the worst in order to sell the story

Also, driving around listening to the new the keep playing blurbs of some "offical news correspondent physicist"

My only thought is the guy who takes a ful time gig consulting for news services obviously couldnt get a real job.

Here's some more:

http://www.nytimes.com/2011/03/14/world/asia/14plume.html?_r=1

The Pentagon was expected to announce that the aircraft carrier Ronald Reagan, which is sailing in the Pacific, passed through a radioactive cloud from stricken nuclear reactors in Japan, causing crew members on deck to receive a month’s worth of radiation in about an hour, government officials said Sunday.

The Pentagon was expected to announce

So, did they?

And what government officals announced that other government oficails would soon make an anouncement?

> The Pentagon was expected to announce
> So, did they?

Yes, now they have:
http://hosted.ap.org/dynamic/stories/A/AS_JAPAN_EARTHQUAKE_NUCLEAR_CRISIS?SITE=TXHAR&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2011-03-14-11-26-01

after a roundup of the bloggers/friends I know in Japan... my suggestion is that we worry over the living, and grieve over the dead...

and ignore 40 year old, obsolete nuclear plant designs that we can't change anyway. I'd say the things are doing OK for having an 8.9R quake nearby...

Sorry Snoop they didnt

It was 'government officals', so probably the same oficals who sad the pentagon was going to announce

lujlp - are you denying that it happened?

The statement was made by the ship's skipper, Capt. Thom Burke. Do you have any reason to suspect he's lying about this?

I am happy to know I will not be glowing in the dark. Although evidently there are condoms that will provide that effect--localized effect, of course.

Americans are afraid of odd things--terrorists, nuke explosions, airplane crashes. This guy Peter King is honking about Muslin domestic terrorists--based on what, two or three such attacks nationwide? Out of nation of 300 million people?

But 30,000 Americans die every year in auto accidents, and 18,000 in plain-vanilla gunshots.

I am not afraid of nuke plants, plane crashes or terrorists, domestic or otherwise.

Here is the actual statement from skipper Burke:

http://homepost.kpbs.org/2011/03/uss-ronald-reagan-commanding-officer-speaks-out-on-crew-radiation-exposure/

"As you may have already heard, radioactivity was detected on 17 personnel from our ship, however, we promptly took the proper precautions and the radioactivity was easily removed by soap & water. The levels that were detected were very low levels. To put this into perspective, the maximum dose received was equivalent to the amount of natural background radiation I would receive in 1 month from sources such as rocks, soil and the sun."

Does anything in that statement suggest a genuine threat to health & safety?

Here's a good post by a nuclear engineer:

http://futurejacked.blogspot.com/2011/03/japanese-reactors-bad-but-not.html

The short version: Things are very bad, but not catastrophic.

> Does anything in that statement suggest a genuine
> threat to health & safety?

No, but only because they could move away from the area in a short time.

Snoopy, my only point was the sources you linked to quoted nothing but secretive unnamed governemtn officals, while you were saying they were quoteing specific officals and specific agencies.

If your going to say your storyy is quoting the pentagin, the story aught to acctually quote the pentagon.

Did up better links, or dont make claims about them that they cant support.

Okay, here goes.

Let's start with the fuel and a couple of terms.

An atom of Uranium, the fuel, is forced to decay abruptly by striking it with a neutron. When it decays, it splits into 2 or 3 fragments, called fission fragments, and a couple of neutrons are released.

When you weigh the pieces, you'll find that the sum of their masses is less than the atom which split. The difference shows up as kinetic energy - speed of the fission fragments and of the neutrons.

You might not know this, but temperature is actually a measure of the kinetic energy possessed by a substance. Normally, solids retain their shape until temperature gets too high, and then they melt; temperature rising some more produces a gas. This is logical, right? Very hot substances give off gases, which speed off into the distance?

So. Back to the fuel. The difference between the weight of the Uranium and the fragments is energy. We can use that to heat something. We normally heat water, because we know how to use water to spin a steam turbine and generate electricity with it.

All we have to do is make sure that the temperature doesn't get too high, and we can continue until the fuel runs out.

How do we regulate the process?
In normal operation, the number of fissions per second is proportional to the amount of heat generated. If we have a lot of Uranium present, that's a way to get a lot of fissions per second, but there's a better way: moderation.

Remember the fuel above, the couple of neutrons? If I can make them produce just 1 fission when a fission occurs, then I have a self-sustaining reaction.

As it turns out, Uranium is picky. It won't split for just any neutron. The neutron has to be slow. Its speed has to be close to the average kinetic energy of the fuel it is passing through. If it's not the right speed, or it's lost to somewhere outside the reactor, then the number of fissions goes down and the reactor shuts off.

As it turns out water is a terrific moderator. If it cools, it becomes denser and slows more neutrons to the speed Uranium finds tasty. When it warms, more neutrons escape and the reaction rate isn't enough to sustain the load; temperature drops.

Control Rods actually adjust the effective size of the reactor. If I absorb a neutron in a control rod, that's the same as letting it escape entirely. Control Rods are always "oversized" for the reactor core, so that it can be shut down, literally, with one or two rods stuck in the fully extracted position.

So. What I do after the engineers figure out how to load the core with fuel is, pull out control rods, adjust them slowly when I reach the height calculated to result in startup, then watch instruments and confirm that water temperature is controlling neutron population. If I want the core hotter by a few degrees, I can pull the rods out a little, because the water doesn't act as a switch. Its effect is gradual. It's called, "alpha-T".

Remember the fuel, above - again? Those fission fragments?

That's actually the problem the Japanese plant is having.

See, fission fragments also decay, but they don't depend on neutrons to trigger that. When they do, they release as much as 7% of the heat that the core can put out at 100% thermal power. If you have a 1000 megawatt plant, as much as 70 megawatts is being produced by fission fragments. This continues after reactor shutdown, which is based on neutron production, for many hours. In the earthquake, the electric plant was flooded and disabled, killing circulating water pumps and their generators. With no way to move heat from the source - the core - to a load - either a turbine or a cooling tower, the 7% power continued to heat and damage the core.

So - what happens when the core melts?

Water is essential to the core to produce a neutron chain reaction and actual continuing power. The geometry of the core is lost, and without the geometry, the core cannot "start up" again.

In normal operation, Uranium fission produces a large array of elements as fission fragments. The most frequent division is Krypton and Xenon, and these decay into an assortment of other isotopes/nuclides. We worry about Iodine, Strontium and Cesium because our bodies can accumulate them.

You've heard about pressure being a problem, and Hydrogen. That's because, during reactor operation, a bunch of H is produced, but it recombines in the primary coolant loop with the Oxygen it was once married to - yes, the source is water, beaten apart by the neutron storm and later by the Gamma radiation from the fission fragments. But if you have no circulation, it can't find Oxygen and recombine - it will collect, and go Bang! later.

The hardest thing to do with this is to understand that almost all of it happens without anything visible at all. The operation of a reactor is one of the best practical examples to show people that yes, we know what matter is made of. For references, look up "Steam" in Wikipedia, and find a copy of Nuclides and Isotopes, by GE Nuclear Energy, in the library. It's about 720 in the Dewey system.

And if you're skeered, buy a dog. And think how likely an 8.9+ earthquake is next to you.

-----

PS - the reaction where U235 + n => 2FF + ~2n + E is called "thermal fission". U-235 likes slow neutrons, called "thermal" for their KE being close to that of the material around them. If the neutrons are fast, U-238 likes those, and you can call that "fast fission", which looks the same: U238 + n => 2FF + ~2n + E.

Thanks Radwaste!

if you guys want a visual on the type of reactor this is, one of the Japan bloggers I read has a link...
http://www.nucleartourist.com/type/bwr.htm

Rad, thank you so much. That was a treat for my brain, and I so appreciate how simply and understandably you explained it. I find that truly smart people who don't have ego issues will explain complex science for you in a way that is completely comprehensible. I just love encountering people like that. My friend Dr. Barbara Oakley is one of them. That reminds me...she explained to me how a refrigerator works when I was in Michigan and I have to go clean the dust off the coils of mine so it won't use energy unnecessarily (so it won't have to work so hard).

Hey, there are more treats in nuke physics. For instance:

The probability that a nuclide will absorb a neutron is called the mouthful, "microscopic cross-section for neutron absorption" - and it's rated in, I kid you not, "barns". A "barn" is 10^-24 cm2.

If you leave a neutron alone for a little bit, it'll emit an electron and become a proton. The freed electron can be captured and let it be a Hydrogen atom.

The collisions that a neutron has with the atoms of the moderator and other substances in the core are evaluated in the term, "average logarithmic energy decrement per collision", and this shows you that water or a dense petroleum are best, due to a multitude of small atoms. Energy transfer happens best when the impacted atom is close to the mass of the neutron.

People think that when a decay happens, it can only happen one way. Ahhh, no. Several isotopes can absorb particles and do nothing. Others fall apart by emitting protons, neutrons, betas, alphas, gammas or just losing it entirely. Some isotopes change their half-life a tiny amount with a change in temperature, and some are more stable when bonded to other atoms.

Plutonium spontaneously changes its crystalline structure when warm but not hot, and gets denser all of a sudden - enough to change criticality estimates and put you in big trouble if you have enough in one lump.

I really can make matter from energy. If I crank a bad-enough gamma past a heavy nucleus, that can produce matter, which can then be slowed and captured by the materials at hand. I just have to have enough energy to hit a threshold and I can make an electron and a positron. It's called "pair production".

And I'm actually just a technician. A standard that blows my mind, and which I use to ask people why they think something they heard really happened in antiquity, is this: The Systeme Internationale unit, the second, is the duration expressed by 9192631770 oscillations of the Cs-133 atom between two hyperfine ground states. Think about that. Somebody had to figure out how to go get Cesium, determine it had two ground states that it would oscillate between, determine that this was stable enough to use as a standard, determine it was superior to other materials that do this - and then measure its behavior to less than one part in a billion well enough to trust it.

So, there was this talking snake...

-----

So - do you remember the difference between the evaporator and condenser?

Learning's always been fun. I mean, please. The alternative is...?

And here's a treat - the Sharpest Manmade Thing!

Don't miss work looking at the links!

Update: An explosion early Tuesday morning damaged the No. 2 reactor at Japan’s Fukushima Daiichi Nuclear Power Station, the third in a series of blasts that have now hit each of the three crippled reactors at the plant, plant officials said.

Here's a thoughtful, related article from Josh Marshall:
http://www.talkingpointsmemo.com/archives/2011/03/just_a_thought_11.php

Folks who need further calming down should compare those scary numbers in the newspaper with the Banana Equivalent Dose (BED):

http://en.wikipedia.org/wiki/Banana_equivalent_dose

Things continue to get worse:

http://www.nytimes.com/2011/03/15/world/asia/15nuclear.html?_r=1&hp

Japan’s nuclear crisis verged toward catastrophe on Tuesday, after an explosion at one crippled reactor damaged its crucial steel containment structure and a fire at another reactor spewed large amounts of radioactive material into the air, according to official statements and industry executives informed about the developments.

After an emergency cabinet meeting, the Japanese government told people living within 30 kilometers, about 18 miles, of the Fukushima Daiichi Nuclear Power Station to stay indoors, keep their windows closed and stop using air-conditioning.

Soem compare and contrast phtos of the damage

http://www.nytimes.com/interactive/2011/03/13/world/asia/satellite-photos-japan-before-and-after-tsunami.html?src=tptw

I hear from a guy on the ground in Japan with a lot of contacts... that much of what you are hearing from media may be hyped, [because a nuclear disaster gets ratings? could be.]
so you might want to stop by and see what he has agregated from Japan... he even has a feed from geiger counters out a fukajima's gate.

http://altjapan.typepad.com/my_weblog/2011/03/should-i-stay-or-should-i-go.html

This gets you a MUCH better picture than what is coming in from the Times.

How many people are stupid enough to belive the reports that the japanese government is telling people to make their homes 'airtight'?

Okay, now there's more.

People are using the term "radiation" wrong. Yeah, just plain wrong. It doesn't make this less serious, but not paying attention to definitions makes understanding and coping with the news literally impossible.

Above I explained how a reactor operates in the simplest of terms. Now, I'll describe what radiation is, what contamination is, and how they relate.

First, contamination.
This is really simple. Contamination is radioactive material in an unwanted place.
Next, radiation is the transfer of energy from one place to another by means of a particle or wave, emitted by a radioactive element as it decays to a stable state.

There are actually three or so types of radioactive material in the immediate vicinity of a nuclear reactor: the fuel (duh), the fission fragments (shown above), and activated components. Neutrons hit so hard that they can make unstable isotopes - radioactive material! - out of ordinary construction materials.

If you took my advice and found Nuclides and Isotopes in the library, you'll find that several materials, like Manganese and Iron, make splendid Gamma emitters after they've been irradiated for awhile. Of course, the fission fragments and the fuel are near to the very definition of "hot", radiologically. These are all tied up nicely in the construction design...

...until the island jumps out from under you.

Mechanical failure and overtemperature release the radioactive material into the air. There, it is contamination. From there, it shines on you, which is why people talk about the radiation first. To many, it doesn't matter what it is, just stop it shining at me!

-----

There are a couple of properties of Rx material you might be interested in.

The units we use at work, to measure dose rate and dose, are milliREM, abbreviated mR or MRem. The REM part stands for Roentgen Equivalent Man, and it corresponds to the energy deposition in a gram of body tissue. Get 1 REM, that's 100ergs/gram.

The isotope involved determines the hazard to you. Here, the problem gets really complex, because some materials that shine hard aren't absorbed by the body, some are, and some shine the "wrong way" to hurt you.

There is a classic question for you: you have a Gamma cookie, a Beta cookie, an Alpha cookie and a Neutron cookie. You must EAT one, throw one away, hold one in your hand and put one in your pocket. What do you do to minimize your exposure?

The answer, and a short story about half-life, after a break!

Snoopy, I'd be very careful about citing the NY Times as a source on this. Their reporting on it so far has been atrocious, which is typical for their reporting on technological issues in general.

From reading mitnse.com and some other sources, here's what appears to be going on:

The most serious incident right now is that a hydrogen explosion has damaged part of the primary containment of unit 2. This means that at least some radioactive water has leaked out into the secondary containment chamber. That appears to be intact, but the leak has uncovered part of the unit 2 core. A partial meltdown may have occurred there. It is not clear why the hydrogen wasn't vented into the secondary structure, as it was at units 1 and 3; maybe they were afraid that another explosion damaging a secondary containment would damage other parts of the plant.

MIT is disputing the widespread reports that the spent fuel pool at unit 4 is on fire. If that were true, the possibility of a large release of radioactivity would exist. However, MIT says the fire was in a pump motor and no radioactive material was involved.

Also: I'm seeing claims that some media outlets have been using aerial footage of a burning oil refinery to illustrate their reports on the Fukajima situation. I don't know if this is true or not; I've not seen any such reports myself. But watch out for that. There are no credible reports of a large fire at Fukajima that would be readily visible from the air.

Rad,

Post TMI in '79 (I was about 80 mi. down range) I read the science -- not the media crap -- and understood in general that I didn't have to worry.

Thanks for the explanation. I know it emotionally and rationally. Explaining it to the naive is hard.

Granted the one reactor has cracked -- we should be sending over a ton of lead and a portable smelting plant to build a sarcophagus for it. Let the Japanese worry about friends, family and the missing.

Japan has been a friend post WWII.

Jim P, it doesn't look like the lead and sandbags are needed just yet. So far, it sounds like the secondary containment on the reactor with the cracked case is holding. One of the problems with the Chernobyl reactors was that they had no secondary containment -- heck, they barely had any primary containment.

Experts Had Long Criticized Potential Weakness in Design of Stricken Reactor:

http://www.nytimes.com/2011/03/16/world/asia/16contain.html?_r=2&hp

The warnings were stark and issued repeatedly as far back as 1972: If the cooling systems ever failed at a “Mark 1” nuclear reactor, the primary containment vessel surrounding the reactor would probably burst as the fuel rods inside overheated. Dangerous radiation would spew into the environment.

Japan suspends work at stricken nuclear plant:

http://finance.yahoo.com/news/Japan-suspends-work-at-apf-3314845701.html?x=0

Japan suspended operations to keep its stricken nuclear plant from melting down Wednesday after surging radiation made it too dangerous to stay.

Japan nuclear emergency workers to return to plant:

http://news.yahoo.com/s/ap/20110316/ap_on_bi_ge/as_japan_earthquake

"Emergency workers forced to retreat from a tsunami-stricken Japanese nuclear power plant as radiation levels soared prepared to return Wednesday night after emissions dropped to safer levels"

From the earlier Yahoo Finance article:

"It's more of a surrender," said David Lochbaum, a nuclear engineer who now heads the nuclear safety program for the Union of Concerned Scientists, an activist group. "It's not like you work 10 days and the radiation goes away. In those 10 days things are going to get worse. It's basically a sign that there's nothing left to do but throw in the towel"

Anti-nuclear activists prophesying doom are not the source to turn to for accurate, sober information in times of nuclear emergency.

Snoopy, that suspension lasted for less than an hour... for actual up to dat info, you might want to go to a Japanese source that has current stuff, like NHK, which is real time:

http://www3.nhk.or.jp/daily/english/16_35.html

Annnnd here we go again!

The answer to the question above:
Throw the Neutron cookie away. It has the highest rate of interaction with your body of any of these, given similar energy.

Eat the Gamma cookie. It has infinite range, but has less than half the rate of interaction with tissue the Neutron has, and interacts less dramatically.

Put the Beta cookie in your pocket. Beta particles, essentially electrons emitted from the nuclei of atoms, generally can't penetrate paper or cloth.

Hold the Alpha cookie in your hand. Though Alpha particles are huge risks if taken internally and are the bane of people who have somehow ingested heavy radioactive metallic particles like the transuranics, the heavy weight and high charge stop them on contact with anything. They can't penetrate skin. Since your skin is actually dead already (epidermis), you have nothing to lose.

In sum: the Neutron is a microscopic bullet, with mass, that zips along at up to about 600 thousand feet/second. The Gamma is a very high energy light wave, like an X-ray, but emitted from an atomic nucleus. The Beta is like an electron (-1 charge) emitted from a nucleus. The Alpha particle is basically a Helium nucleus, broken out of a bigger atom and moving pretty slowly; it's 2 protons and two neutrons (+2 charge).

All of these are called ionizing radiation. When they strike somthing important - oh, like you, for instance - they cause chemical changes in the immediate vicinity of the impact, starting with, you guessed it, creating ions.

A particle born of a nucleus, formerly held by the strong nuclear force, has no trouble disrupting the weak nuclear force and charge and maybe Van der Waals-like forces holding your DNA together. Hey, the third eye could be useful!

-----

Now, about half-life:

Yet another wild thing about radioactive materials is that although we cannot look at an individual atom and tell when it will split on its own, we can look at a bunch of them and say with near-total precision how the bunch will break down.

Simply put, an element's "half-life" is the amount of time that element takes for half of the mass under observation to decay into something else.

But now it gets complicated. Surprise! After one half-life passes, a pound of Stuff 1 doesn't turn into a half-pound of Stuff 2 and leave a half-pound of Stuff 1!

If you look at many of the heavy elements, they put out Alphas, or they can spontaneously fission (and that produces a mess!). Or they can emit a Beta. All three things can be happening in the same observed mass.

We don't care. Do we?

Yes, we do.

The manner in which an element decays is called the decay chain. This is because, for a lot of the elements in the Periodic Table, and to a greater extent in the Chart of the Nuclides, the manner of decay has a lot of influence on what goes on around a mass of that element.

More in the next post!

By the way: Dose Rate x Time = Dose.

Ballpark: 1 gram of Co-60 produces a Gamma rate of 1 REM/hr at 1 meter. 50 REM, received in one exposure event, is detectable in blood chemistry changes. LD50 is about 600 REM, IIRC. It depends on the level of hospital care.

If you have a big radiation field to work in, the solution is to bring hundreds of people, shortening the task for any one person.

Exposure can be high enough to result in instant confusion and death, as it was for Chernobyl firemen, but in most cases it won't be.

Many years ago, a Californium-252 neutron source rod melted inside the Process Room at a reactor in the USA. Since it wasn't an explosion, and the containment building was designed to mitigate a widespread reactor failure, it didn't challenge any equipment; the problem was, how do you get the residue cleaned up?

Simple. Every available employee at that Federal site was told to walk by the scene in the process room, make a swipe with a cleaning cloth, drop the cloth in a bag afterward, and do not stop for anything. I'm told more than five thousand people made that trip.

Heh. So many people see Geordi LaForge yelling about a "warp core breach!" Then, they panic about reactors, not knowing anything, about anything, really. The reality of how all this stuff works is simply awesome. If I told you I could make electrical power just by bringing two hunks of metal closer together, you'd tell me to log off WOW and get a life!

That or burn you for witch craft

I thought death threats were a crime.

I probably would have set my own doormat on fire(assuming an outside entrance to the apts, and not a totaly enclosed building) and then called the cops again.

"That or burn you for witch craft"

How did this end up here, and what am I missing?

Schwarz wird Grün - ausgerechnet BW bekommt einen grünen Ministerpräsidenten. Es war halt nur eine Frage der Zeit. Wäre es auch ohne Fukushima dazu gekommen? Jetzt muss sich zeigen, ob grüne Politik auch in der Realität funktioniert.

Please note that

"The REM part stands for Roentgen Equivalent Man, and it corresponds to the energy deposition in a gram of body tissue."

should read

"The REM part stands for Roentgen Equivalent Man, and it corresponds to the biological damage done by the energy deposition of 100 ergs per gram of body tissue."

The REM is corrected for the effectiveness of the particle/wave transmitting energy, so it does not matter if a gamma, beta, alpha or neutron caused the damage.