Last Post on Fukushima for a while...

I've had a few, genuine comments from people in the area of the reactors, looking for advice and thanking me for providing some clear insight.   I was writing a response back to one of them when I just decided to make this my (possibly nearly final) post on the Fukushima reactors.

"one cup of coffee" asked,

If you don't mind me asking, I'd like to know what you think? If, as they are saying, they are able to get power to the plants and restore the cooling system will they have saved the plant from dumping more radiation into the environment? At that point will the situation be "under control?" What exactly would it take to get the situation under control? It seems like the foreign press is obsessed with worst case scenarios, what about a reasonable set of most likely scenarios? And lastly, what about the plutonium? Is this significantly more dangerous than the uranium?

and it spawned a whole host of emotions.  Here's my response.

I'd give it another WEEK before we can safely say that we're "out of the woods" and that there will be no more flare-ups.  A recent report I read said that some of the concrete wall surrounding the spent fuel pool of reactor #4 has fallen away, but that the steel liner remains.  If the pool crumbles, my guess is that it would make cleanup considerably messier, but *shouldn't* provide any additional risk to the general public.

Getting reliable power to the site will help tremendously: they may be able to turn on some of the pumps and ensure good water circulation, and they should be able to get a more reliable flow of water to the core.  But even then, the road ahead is a lot of (boring) circulation of water as the core cools down to a point where they can safely inspect it with cameras and robots.

And the plutonium: I've enjoyed looking at what other sites link to mine (thanks Google Analytics!), but some of the sites out there are just absurd.  My jaw dropped at the rampant mis-representation of the facts, and heralding the fact that "Mox fuel is two million times worse than uranium."  Baloney.  Yes, plutonium has a higher toxicity and a lower melting point than uranium, so it's not quite as robust.  It might result in a slightly higher dose to those at the plant (who have tools and equipment to deal with it appropriately), but in no way will it lead to any additional dose to the general public.

Earlier in the comment, "one cup of tea" noted that people have a very visceral response to radiation.  And sadly, that's very true.  Radiation is all around us, and I think people are ignorant of that.  The background radiation you get from the Colorado Plateau is five times higher as on the eastern seaboard, and yet you don't see people fleeing Colorado for the coasts.  And as I noted in a previous post, people are exposed to small amounts of toxic chemicals all the time due to spills and accidents, and yet humanity moves on.  Remember the Union Carbide plant in Bhopal?  A hideous, gruesome release of methyl isocyanate killed thousands and injured tens of thousands, and yet the industry goes on.  I wish the public could put radiation in the same context that almost everything else is, and I guess that starts with education.

Lastly, a comment on frustration: I have read reports from scores of "experts" proclaiming that the Fukushima "crisis" will be worse than Chernobyl and that lives are at risk all around the world.  Where is the accountability?  Where are the apologies when these people are shown to be wrong?  Where is the public excoriation when the "expert opinions" turn out to be nothing more than fear-mongering, playing on the deep-rooted fears of the general public?  When does the loss of credibility set in?

Sadly, it won't.  The nuclear "debate" will continue, fueled more by emotion than by fact when no one in the general public is affected by this event.  And the nuclear "experts" will continue pressing the panic button and gleefully watching the response.  And most of the mainstream media will follow them doggedly because it sells newspapers and it generates interest.

The solution, I think, starts with education.  Patient, careful, instructive education.  I hope I've been able to provide some of that here.

I'll leave with the most recent update from JAIF on the status of the reactors (click for bigger):

Summary of Fukushima

I have stopped reading cnn.com and other mainstream media news outlets because of the hysterical, sensational headlines that they're touting.  This entry is going to try to set some of the record straight, based on what I've compiled from reputable news organizations, press releases, and colleagues.

1. Status

This is current as March 15th, 6pm or so EDT.  Summarized from a more technical JAIF publication.

Update, 9:50am, March 16: Here is the latest technical publication from JAIF.  The situation has become slightly worse over the past 12 hours, with more damage to spent fuel pools and more damage to primary plant integrity than my above chart.

• Fuel: This is the current condition of the fuel in the reactor vessel.  Units 1, 2, and 3 have had some level of core damage because of the falling water levels (I'm making an educated guess at Unit 2 for simplicity).  Melting core means the release of radioactive fission products, and these now get released when they burp the reactor to relieve pressure.  This is what US Navy ships and others in the area are detecting.  The release of radiation is a bad mark on the industry, but it still has no measurable impact on human health.  This kind of thing happens all the time in the chemical industry (each one of those words is a link to a separate incident!!!); the nuclear industry is held to a sterling standard.
• The primary plant integrity is questionable on Unit 2 because of the unexplained explosion (the one inside the reactor building, not the ones that blew the top off the buildings) and related drop in pressure.  This is usually indicative of a hole opening up.  I haven't been able to determine if the torus is isolable from the reactor or not.
• In the case of Unit 1, not only are they trying to fill up the reactor vessel and cover the core, they're also trying (or were trying) to fill up the primary containment as an additional cooling measure.  This will require millions of gallons of seawater, and will take a while.
• Vent to atmosphere: all three reactor plants have been burped at least once.
• Spent Fuel: Unit 4 did not have any fuel in its reactor vessel -- it was all located in the spent fuel pool for tests.  Which caught fire.  OK, this is bad.  I'm not sure how the operators allowed the pool level to get that low: the pool is 45 feet deep, and the fuel elements are about 12 feet tall, leaving over 30 feet of water to go.  A lot of water has to boil off before you expose the fuel elements, but apparently that's what happened.  That caused additional radiation to be released, but still not enough to affect the area outside of the nuclear plant facility.

2. Future.
Core cooling efforts will continue.  There is probably a small slurry of reactor fuel, cladding, control rods, and core structural material in the reactor vessel.  This is similar to what happened at Three Mile Island.  By keeping water on the cores, they're keeping it from melting any further.  Unit 1 was scheduled for retirement on March 26th, 2011, so that was very near the end of its useful life anyhow.  Units 2 and 3 will never operate again; cleanup is going to be too hard and too expensive to get them back into working condition again.

TEPCO is calling in helicopters to dump water on the spent fuel pools to prevent them from catching fire again.  I'm still shocked that happened in the first place.

There remains at least 6 inches of reactor vessel steel and about 6 feet of steel reinforced concrete that is keeping the worst of the stuff inside.  Occasional burps of steam and gas may occur, and these are sent through "scrubbers" and filters before they are released.  Some radioactivity will still be in there, though.

3. Stop the Hysteria.
A dose rate of 40 REM/hour was measured between Units 2 and 3 sometime yesterday.  This is pretty hot for a localized spot.  But a single location DOES NOT endanger the entire island of Japan.  I'm sick and tired of reputable news organizations linking the awful conditions in Japan with the nuclear incident -- while this is an unprecedented situation with 3 reactors having core damage, the situation has not had one iota of impact on the health and safety of the residents of Japan.

Personally, I believe people are being evacuated out of an overabundance of caution.  In the interest of full disclosure / total honesty, there is a possibility that the Japanese government knows of large cracks in the 6 foot thick containment walls due to the magnitude 8.9 earthquake. (I was told that the design basis earthquake was 8.2, which means the actual quake was 7x larger than design.)  If history shows that the government or other authorities were trying to keep something like that secret, the political and regulatory impacts would be terrible.

There is NO chance of hazardous material raining out across the Pacific or endangering the US.  The hysterics and comparisons to Hiroshima are unwarranted.  And newer designs will only weather this kind of event better, with built-in passive safety systems that don't need offsite power to work.

4. Shout-outs.
As part of all this, I've discovered other bloggers who have been doing fantastic jobs getting out information in a clear, easy-to-understand manner.  Reward these folks by hitting their site, too:

• The Neutron Economy. I love that name.
• Futurejacked.  Also a nuclear engineer who has similar socioeconomic interests as I do.
• Brave New Climate.

And that's about it.  Thanks to everyone for the emails, comments, and input.  I'm glad to help where I can.

A turn for the confusing ...

Things are starting to get more confusing as the news pours out of Japan.  When I last wrote, things appeared relatively calm, as it looked like TEPCO had managed to get mobile electric generators on site and were keeping the reactors (mostly) cool through injection of seawater.

Then the hydrogen explosion that started on Unit 1 also happened on Units 2 and 3 (see bullet #1 from my previous post).  The explosion from Unit 3 apparently knocked out some of the cooling pumps on Unit 2.  There has been a very different type of explosion on Unit 2.  And a fire broke out in or near the spent fuel pool of Unit 4.  It's hard to keep it all straight, it's hard to follow along without spending hours sifting through all the reports.  The TEPCO press releases aren't all that great, but I imagine they're putting every available resource on fixing the problem, not posting web pages.

NEI is reporting that radiation levels as high as 40 REM/hour were measured between Units 2 and 3.  Yes, at that location, that's pretty high and I wouldn't want to stand there for very long.  But to put that in perspective, it's still not a level that represents enough radioactivity that would threaten anyone outside the fence of Fukushima.

The most interesting tidbit, to me, is the explosion in Unit 2, and the hole that it created in the suppression pool.  And this is where my knowledge of BWR's hits a wall: I don't fully understand the purpose, potential leakage paths, or impact of a hole in the suppression pool, so I'm not going to make any predictions about it.  I'll be watching for updates on that today.

The reported fire at Unit 4 is scary at first because it was in a spent fuel pool, but it appears to have been put out.  My guess is that oil or debris got in there and caught fire.  I have seen analysis that all you really need to keep water in those pools is a garden hose, and that is sufficient to keep the spent fuel covered and cool.

TEPCO and the folks on the ground at Fukushima are doing a heroic job at trying to keep three nuclear reactors under control after a magnitude 8.9 earthquake.  I'm sure all of them have families, all of them have relatives, all of them have lost something in this earthquake.  And there's a lot more going on in Fukushima than just the reactors -- a water dam broke as a result of the earthquake and washed out 1800 homes -- but that doesn't seem to get much press coverage.  If you want a calming, strong essay on why there's other, bigger things to worry about, go over and read this piece on Atomic Insights.

Daiichi Reactor Design

The Fukushima-1 Reactor at Daiichi is a General Electric BWR-3 design with Mark I containment.  It turns out that the Boiling Water Reactor at Oyster Creek, New Jersey, is an almost identical design: BWR-2 with Mark 1 containment.  Oyster Creek is the oldest operating commercial nuclear reactor in the US today.

Here's a very, very pretty picture of Oyster Creek.

The above is from a University of New Mexico archive of fascinating drawings of nuclear power plants from around the world, which will make almost any nuclear engineer drool.  You can get the full pdf of Oyster Creek here.

In particular (I think you need the full pdf to see the detail), note the location of #14 (the spent fuel pool), #6 (safety valve -- this is probably what they used to burp the reactor), and #27 (the recirculation pump, which is what's keeping the water circulating and core cool right now).

Details:

Fukushima-1: 460 MWe, initial criticality in October 1970.
Oyster Creek: 619 MWe (it's been uprated a few times), began operation on December 23, 1969.

Update on Daiichi Reactors

It's frustrating to see the hysterics and out-of-proportion headlines that are being streamed all over the internet.

In the 24 hours since my last post, we've learned a few things:

1.  The explosion that happened on Unit #1 may happen again on Unit #3.  (There were 3 reactors at Daiichi operating when the quake hit: Units 1, 2, and 3.) Below is a (now famous) video of the explosion ... fast forward to the 45-second mark and you'll see it go.

Why did this happen?  How could such an enormous explosion not be catastrophic to the plant?  And should we panic if this can happen to another unit?

First, the why -- and an admission that my initial guess / explanation wasn't 100% accurate: When metals get really hot -- like around 1800F, far hotter than normal operation -- metals can interact with steam to create hydrogen.  In the case of the 439 megawatt (electric) Unit #1 reactor, it's probably 200 to 300 kilograms of H2.  In the case of the 760 megawatt (electric) Unit #3 reactor, it's probably 300 to 400 kilograms of hydrogen.  The release of hydrogen causes pressure to build up very fast, and the operators had no choice but to burp the reactor, like I described before.

(My initial explanation neglected to explain the steam / metal interaction. Sorry.)

Okay, so you burp the reactor ... where does it go?  Into the containment structure.  See picture below.

The lower structure (called the primary containment) is a very, very robust (6 foot thick, steel reinforced walls) containment structure.  When they burp the reactor, the gases initially vent to that area.  But pressure can rise too high there, too, over time (above 840 kPa, as I mentioned before), and the primary containment needs to be burped ... into the secondary containment.  The upper structure, perhaps the top 1/4 of the picture above, is the secondary containment, and it's just steel framing and siding.  It holds the refueling crane and ... unfortunately ... the spent fuel pool.

When the pressure from the primary containment was burped into the secondary containment, the pressure and humidity dropped suddenly.  With less steam in its environment, the hydrogen was free to autoignite -- which is does, happily, at about 900 degrees Fahrenheit.  What we see is the top 1/4 of the containment building -- the part with steel framing -- blowing off.

Here's a picture from the NYT of what's left.  

The warnings that TEPCO is giving out now are indications that the pressure has risen in Unit #3's primary containment enough that they're going to have to burp to the secondary containment ... and the hydrogen could accumulate there (without steam) to cause a second explosion.  Since Unit 3 is about 50% bigger than Unit 1, the resulting explosion could be bigger.  The primary containment has been designed to withstand this kind of shock.

But note one thing that I've learned in this process -- do you see those spent fuel pools in the above picture?  That's where they put spent nuclear fuel after it has been in the reactor ... and they're outside the primary containment. (In hindsight, that's a very silly place to put spent fuel.)  I DO NOT know if there was any spent fuel in there at the time the quake hit.  I HAVE NOT seen any evidence or news reports mentioning the presence of spent fuel.  But the fact that there could have been spent fuel there makes me nervous.  If there was, the pools were probably emptied as part of the explosion, and without water to cool / shield the spent fuel, the risk of spreading contamination increases.

Again, I haven't seen any mention of whether there WAS or WAS NOT spent fuel in there.

2.  News agencies are really trumpeting the fact that radiation was detected and that people had been tested for contamination and -- gasp! -- some levels were as high as 100,000 counts per minute.  These numbers sound terrifying, but it's important to keep some perspective: the level at which you can detect radiation is far, far less than the level at which it becomes a hazard to health.

For example, here is a link to where you can purchase your very own radiation sources, and no NRC license is required.  The strength of these sources?  1 microCurie, or about 2.2 million counts per second.  Literally, I could buy one of these sources, cut it up and distribute it evenly to 20 of my best friends, and the level detected would still be higher than what they're finding on the general public.

I reiterate: 

The level at which you can detect radiation is far, far less than the level at which you need to be concerned for health reasons.

3.  Some core damage appears to have occurred.  I got a mailing from the American Nuclear Society yesterday, and it mentioned that some of the core fuel may have been damaged as part of the increased temperature and reduced water supply.  The Nuclear Energy Institute is also saying that there may have been some core damage.   This is unfortunate.  But would somebody please tell the Japanese chief cabinet secretary to quit saying things like, "We're assuming there was a meltdown"???  Good grief; this is really feeding the trolls.

The word "meltdown" has very big implications, and instills fear and panic in the general public.  With the decision to throw seawater on the core -- a basically limitless supply of coolant -- the chance of a meltdown is ridiculously small.  As long as backup power and / or fuel for the generators can keep putting water in, the core will stay covered and cool.

I'm still following these sites for good info:

• World Nuclear News (probably the best summaries I've seen)
• Nuclear Energy Institute and its Fact Sheet
• Atomic Insights (good, rational interpretation of things)
• CNN for the laughs.

Fukishima Daiichi and Daini Reactors Perspective

Japan's 8.9-magnitude earthquake may well turn out to be one of those nation-defining moments that is seared in the psyche of its citizens.  My thoughts and prayers go out to the millions without electricity, without homes, without food, without clean water.  When the earthquake hit, almost all major electricity-producing entities shut down.  Including nuclear facilities.

Here's what's going on in mostly plain English, for the readers out there who might come across this site.

First of all, it's important to keep this in perspective: Japan has 52 operating nuclear power plants, and the issue at hand relates to 7 units.  The other 45 have handled the earthquake and tsunami acceptably.

Three of the reactors at Daiichi were operating when the quake hit: units 1, 2, and 3.  They're all Boiling Water Reactor types (dangit! the physics just got harder), and they produce between 440 and 760 megawatts of electricity -- each.  Assuming they're 33% efficient, that's almost 6,000 megawatts of power that they produce, total.

When the earthquake hit, they all began a normal shutdown procedure by driving the control rods UP into the core. (You normally think of control rods falling DOWN into the core, but this is a boiling water reactor, which means things are very different for various reasons.  In a BWR, the rods come up from the bottom.  See figure.) This shuts down the nuclear chain reaction -- but it doesn't stop the generation of heat.  This continuation is from the continued radioactive decay of the core, known as decay heat.

Nuclear engineers have a few rules of thumb about decay heat: at time of shutdown, it's typically about 5% of the initial core power, and declines steadily (although not linearly) after that.  In this case, 5% of the initial 6,000 megawatts of power means it's still producing about 350 megawatts of power. (Note this is just thermal power, not electricity, as the turbines are isolated as part of the shutdown procedure.)  Simple physics and heat transfer dictate that the heat must be removed -- or the reactor starts heating up.

A former mentor of mine, when teaching a reactor thermohydraulics course, wisely stated it as:

The reactor is going to get the heat out, or it's going to die trying.

That's kind of where the Japanese are (or were, as of last night) with their reactors.  If the 350 megawatts of heat isn't removed from the core, the core starts heating up.  To address this, all reactors have circulation pumps to move cooling water around and remove the decay heat.  But what powers the pumps?

The cooling pumps have multiple, independent power sources, nearly all of which were wiped out by the tsunami: remote power stations went offline; the diesel generators either didn't work or were damaged by the tsunami; but they did have battery backups that lasted for a little while.

As things heat up, the pressure increases.  This is okay, up to a point.  The Tokyo Electric Power Company (TEPCO) has notified the Japanese government that they have initiated a few releases of steam -- basically, a controlled burping the reactor.  The World Nuclear News site says that pressure is normally 400 kPa, and the "burping" starts at 840 kPa.

Does this release radioactivity?  Well, theoretically, yes.  It does.  There are trace amounts of tritium, activated nitrogen, and activated oxygen in the cooling water.  But the amount is very, very small, and does not present a hazard to life, or a significant risk for cancer.  It's a drop in the bucket compared to the amount of natural background our bodies are exposed to every day from the earth and sun.  I'm quite sure this point will be lost or glossed over in the press headlines over the next few days.

Then there was an explosion at one of the containment domes at the Daiichi site.  Wow; that got my attention this morning.  The burping cycle I described above can keep things under control for quite a while (as long as you've got backup power to run the pumps, which they appear to have fixed the generators, and they are now pumping seawater into the reactor for makeup water).  The question is, did the explosion come from the reactor itself?  Or something outside the reactor?

In this case, it appears to have come from outside the reactor.  During this burping process, things can get pretty hot.  Hot enough, in fact, to separate the oxygen from the hydrogen in water.  So now you have hydrogen and oxygen floating around, and they get burped to the containment dome.  A small spark from the stator of one of the cooling pumps is all it takes to ignite the hydrogen, and poof.  (Apparently these pumps aren't ignition protected, which IS a requirement in US reactors today.)  An unfortunate explosion inside the containment dome.  That's better than the reactor exploding, but it's undesirable because you've now lost one of the (many) protective barriers between the fuel and the outside world.  I don't know what damage was done to the reactor in the explosion.   Modern day reactors are designed to handle this; the three Daiichi reactors were built in 1971, 1974, and 1976, and I don't know what design criteria were in effect then.  The four reactors at Daini were all built in the 1980's.

Lastly, some perspective:
Chernobyl: Absolutely, positively, NO CHANCE of something like that happening here.  At Chernobyl, the operators were doing something stupid, ignoring at least 4 levels of safety alarms and automatic shutdowns, and managed to get an aging reactor (designed in 1954) into an unstable condition that is totally impossible in any modern reactor (including the ones in Japan today).  The reactor went prompt supercritical, blew the lid off the reactor vessel, exploded the reactor building, and sprayed fuel elements around the countryside.  Not remotely possible here.

Three Mile Island: Distant possibility of that happening here, but even in that case, it's important to remember: even though 30% of the core melted, "there will either be no case of cancer or the number of cases will be so small that it will never be possible to detect them. The same conclusion applies to the other possible health effects." Wikipedia has a good summary of the incident.  In this case, the operators have seawater available, they appear to have power to operate the circulation pumps, and it's just a waiting game until remote power can be restored to the sites.


So, that's where we are now, as of about 9:00am EST on March 12th.  Certainly, an industry-defining moment.  Many will proclaim this to be another nail in the coffin for nuclear power; many will hail this as showing that nuclear reactors can safely withstand an 8.9 magnitude earthquake.  Me?  I'm somewhere in the middle: yes, the design appears to be working okay (even though this is one more reason that I don't like boiling water reactors and prefer pressurized water reactors), but why weren't the diesel generators housed / located / sized / reinforced to handle the tsunami?  If those generators had worked like they were supposed to, we wouldn't be in any of this mess.

Here are the sites I'm going to be following:

• American Nuclear Society's Nuclear Cafe.
• World Nuclear News's coverage of the event. (Very good.)
• Nuclear Townhall