Prompt Criticality

Today, on the 25 anniversary of the Chernobyl disaster, I have two reports on the spent fuel pools.  The first is a frightening report on the huge explosion in Reactor #3 from Arnie Gundeson.  He's the nuclear industry expert who was asked to investigate Three Mile Island, and after discovering a much more serious situation than was being reported, went on to become a nuclear watchdog.  His latest report, at:

http://fairewinds.com

shows a side by side comparison of the two explosions at Fukushima Dai-ichi: Reactor #1 and Reactor #3. The reactor #3 explosion was more powerful and shot straight up.  He posits that it was not the reactor vessel, and its fuel rods exploding here (the reactor is still in tact), but instead that a hydrogen explosion disrupted the spent fuel pool so much that the Uranium & Plutonium there went "Prompt Critical",  and instantly released huge energy, which was channelled upward by the walls of the topless spent fuel pool.  Prompt Critical reactions are a kind of super-critical reaction that happens in nuclear bombs, and also is what happened at Chernobyl.

This analysis is confirmed by a second nuclear expert in an interview on RT.  

The implication is that the Plutonium and Uranium in reactor #3's spent fuel pool was vaporized and shot up to become airborne, in contrast to the expectations I wrote about in my last post that U and Pu would remain mostly at ground level.  This is consistent with ongoing reports of Uranium and Plutonium fallout reaching the whole of the US, with detections occurring in Hawaii, California and New England in particular.    From what I've seen at the EPA website, there doesn't appear to be high levels of U or Pu...but then I'm not sure what level to be concerned with.

Finally...part of the solution?   Here is a figure from the Japanese press, translated into English by former SFSU student Joey Fedrow, who is currently living in Tohoku.  It shows a possible scheme for repairing spent fuel pools.  I assumed this was just for Reactor #4, but perhaps it could be used for other reactors at well.

One thing that is disconcerting is how slow TEPCO is moving to contain the damaged reactors.  At this stage (49 days in) at Chernobyl, they were already building the concrete sarcophagus.

The Night's Plutonian Shore

When I was an undergrad at Berkeley, I was nervous about seeing my professors in office hours, as many students (including mine today) are.  I had good reason to be nervous since my Berkeley Physics profs. were all hot-shots in their field; indeed one (O. Chamberlin) was a Nobel Prize winner.  I remember one time while trying to find a professor's office, (and trying to distract myself from getting there), I discovered and read a plaque on the wall.  It was a historical marker stating that this was the location where the element Plutonium was discovered. (Unlike other elements Plutonium, Pu, must be synthesized, since its too radioactive to occur naturally) At the time I had no idea about Berkeley's role in the Manhattan Project, or what Plutonium really was.  Plutonium was named by its discoverers, McMillan and Seaborg, for the god of the underworld, Pluto.  On the periodic table it follows Uranium, and Neptunium.  (See a pattern there?)

There's been concern about reactor #3 at Fukushima Da-ichi because it contains MOX, or mixed oxide nuclear fuel.  "Mixed" means that Uranium is mixed with Plutonium.   Where did that Plutonium come from if it doesn't occur naturally?  It came from Japan's nuclear reactors, which, in the process of causing Uranium to fission (split in two) also produce plutonium as a by-product.  In Japan and other nuclear countries (but not the U.S.) this Plutonium by-product is "re-processed" by sorting out extraneous isotopes which inhibit fission (so called "neutron poisons") then re-using the Uranium/Plutonium mixture.  It was at one of these re-processing plants that a criticality event killed two Japanese workers.  Because Plutonium is a by-product of all Uranium fission, it can be found in all six of the reactors at Fukushima, not just #3.  In particular, when the explosions & fires at reactors #1,2 &3 destroyed the buildings they were housed in, its likely that the Plutonium & Uranium in the spent fuel pools could have been dislodged or scattered.  This would explain the story I blogged about earlier that "neutron beams" had been discovered around the plant, and the later admission that Plutonium had been found some distance away from the reactors.

Last night my wife and I watched the 1983 movie Silkwood, in which Meryl Streep's character, Karen Silkwood, a worker in a plant fabricating MOX for the Hanford Breeder reactor, somehow gets Plutonium in her lungs.  (Its a true story, the real Silkwood died under suspicious circumstances after whistleblowing serious safety violations at her workplace).   But how dangerous is Pu?  Ralph Nader claimed a small amount could kill everyone on Earth if spread out, but  one pro-nuclear power/weapons scientist bet that he would eat as much Pu as Nader would drink caffeine.   (This bet never happened.)  Because it decays slowly (half-life 24,200 years) Pu-239 doesn't emit as much radiation in a given minute than other radionuclides.  But this long half life implies that it takes 800 centuries for any quantity of Pu-239 to decay until it is 90% gone.   Pu-239 breaks down via Alpha decay, which makes it less dangerous.  Alpha particles are stopped by a piece of paper or skin so they are not harmful when an external exposure occurs.  However internal ingestion of Alpha emitters can be deadly.  My research has not been able to determine how deadly Plutonium is (some Manhattan Project workers actually ingested it by mistake and survived to old age!).  Its may depend a lot on how long it stays in your body.    The primary concern is the long half life and the threat that contamination may affect an area for generations.

These factors came up when a blog which has been covering the Fukushima meltdowns announced "Radioactive Fukushima Plutonium Bombarding US West Coast since March 18".  The site run by one Alexander Higgens is attempting to provide alternative media to complement information not covered in main stream media.  This is a worthwhile goal.   I learned from the site that one can visit the EPA's radiation monitoring website and get data on the isotopes they are searching for.  Higgins has done so, and this prompted his announcement above.   However, when I searched the EPA site for Plutonium in the SF area, I found that the levels detected were less than the uncertainty in the measurement.  Scientifically this means that zero Plutonium was detected in the US (at least in SF area).   Overall I've been somewhat disappointed that a blog/media site(s) which attempts to serve the important role of providing an alternative to the mainstream media has produced such headlines with shock value but not thoroughly researched.

One claim which I have not been able to investigate is that the initial forecasts for the spread of the radioactive plume where doctored to minimize the apparent threat.   This could easily be done by changing the color scale on the maps showing radiation flowing across the Pacific and beyond.  However the video linked above is too small to read the numbers on the scale.   It is clear that some serious downplaying has occurred, however.  For example, initially TEPCO said "its only a level 5 disaster...nothing to worry about".  Then, when they upgraded it to Level Seven, they said "Its OK now because most of the radiation was released back when we said it was Level Five" !!  

At our presentation on the quake/tsunami/meltdowns on Monday, Prof DeWitt pointed out that Plutonium is not volatile and unlikely to become airborne.   So it seems that now plutonium is not one of our main concerns, while keeping an eye on the levels of Cesium-137 and Iodine-131 in local milk and vegetables seems warranted as a precaution, especially for parents.  These levels have shown a rise in recent days.   Any increase in I-131 concentrations is troubling, due to its short half-life.  To me this constitutes further evidence for ongoing nuclear reactions at Fukushima.

     `Be that word our sign of parting, bird or fiend!' I shrieked upstarting -
     `Get thee back into the tempest and the Night's Plutonian shore!
      Leave no black plume as a token of that lie thy soul hath spoken!
      Leave my loneliness unbroken! - quit the bust above my door!
      Take thy beak from out my heart, and take thy form from off my door!'
      Quoth the raven, `Nevermore.'

Disaster Day

San Francisco's First Skyscraper, April 1906

April 18 is probably the most important day in San Francisco's history.  Its the anniversary of the Magnitude 7.9 1906 Great Earthquake and fire which destroyed the city.  It was the costliest natural disaster in Earth's history at the time.  Commemorations are held each year with dignitaries and an ever shrinking list of the quake's survivors at "Lotta's Fountain", a landmark on Market St. at 5:12 AM.   I attended the ceremony in 2006, along with a crowd of tens of thousands of other early risers.  As the exact hour and minute of the 100th anniversary approached, a hush came over the crowd, and people whispered nervously "could there be another quake on the anniversary?  What are the odds?"

This year on Apr. 18 I was scheduled to give a presentation on the Tohoku Earthquake and Nuclear Crisis, the subject of this blog, to San Francisco State, as part of College of Science's presentation on the quake, tsunami and nuclear crisis I mention in my last post.   However, one hour before the talks were to begin the campus suffered a massive power outage which also took out electricity in the surrounding areas.   After walking from my building to the venue (in the vain hope that a different building would have electricity), I was locked inside the room as officials secured building.   As time went on it became clear that we wouldn't get power back, but that a large number of people were interested.  Dean Sheldon Axler asked the participants if they could give their presentations without visuals, and we all agreed.  "The show must go on."  The room wasn't entirely dark since large windows permitted sunlight in.   I was personally quite disappointed because the event had been my idea in the first place and I'd put considerable work into my presentation.  Nonetheless the presentations all went well, and I was happy with the turn out.

Immediately afterward I had to teach my Astronomy 115 class in a darkened 160 seat lecture hall.  attendance was low, around only 100 students, and there was no way for students to see the white board or to see their own notes.   So I ditched my planned lecture on colliding galaxies and simply opened up the floor for students questions on thing the didn't understand well or though should be covered in this class.  This proceeded for some 45 minutes when suddenly we all the room shake in an abrupt jolt.  As people looked around  and began to say "earthquake?"...a second more powerful jolt struck.  At the front  of the class I shouted "that was an earthquake!  Everybody leave the building!"   I was quite jittery from the days events, and began to speculate.  The jolt was so sudden, and lacked the usual swaying feeling of a quake, that I wondered if it wasn't actually an explosion.   I remembered the huge deadly explosions in PGE's gass lines a while back, and PGE was working nearby to fix the electricity proglem.  Could the days two disasters be connected?

I decided to leave the campus and see how my wife and child were at home.  Before collecting my bike, I swung by the Geosciences office for some quick information.  There I met Prof. Ray Pesteron, with whom I shared the stage earlier and Miriam Knof, Geosciences office manager, whose delightful smile and assistance can always be found in that office.   Ray informed me that it was indeed a quake and that what I had felt was first the P-waves hitting then the S-waves.  Since the were so close in time, the quake must be nearby.  We then made guesses as to the quake's magnitude and distance.  Ray said 3.5 within 10 miles and I said 4.0 within 20 miles.  We later learned that it was 3.8 and only a few miles away.   In fact the San Andreas fault, the same fault that caused the 1906 quake had again moved exactly 105 years to the day later!   Ray said the fault "was just trying to remind is: I'm here.  Don't forget about me, with all this activity in Japan!"

In case you missed my presentation...or incase you were there! the slides can be found at:

http://physics.sfsu.edu/~chris/

SFSU Event Monday

A month ago, I suggested to the Dean of the College of Science & Engineering to have an event on the Japanese earthquake/tsunami/nuclear disaster.  Since then the Assistant Dean, Lisa White, has organized an event to coincide with Earthquake Awareness Day, April 18 (the 105th anniversary of the Great Earthquake which devastated San Francisco in 1906.)   Speakers will discuss quakes, tsunamis, earthquake engineering, and I will make a presentation on the nuclear effects at Fukushima.   Here is a flyer for the event.   If we can get it recorded, I'll post the video here.

The Zone is Growing: Level Seven

The Zone, from  A. Tarkovsky's Film Сталкер

"The Zone"  Strangely this term has been used to describe a region of exclusion due to radioactive (or other) contamination several times, both in fiction and real life.  I first heard the term in the film by the great Russian director Andrei Tarkovsky about a Zone sealed off by the Soviet government after an unspecified (extraterrestrial) contamination.  The film, called Stalker  (Russian: Сталкер) is named for the tracker who guides people on illegal journeys into The Zone.   Many people assume this film was inspired by Chernobyl, but in fact it was made about five years before that disaster.  It may have been inspired by the mysterious Tunguska Event, and perhaps the top-secret 1957  Mayak disaster, a radioactive release at a Soviet plutonium reprocessing facility that killed hundreds and was the second worst nuclear accident in history (on the INES scale)...until today.

"The Zone of Alienation"  is the creepy sci-fi sounding official term for the patchy region around Chernobyl that was and still is so radioactive that is it off limits.

At Fukushima, "The Zone" from which people must evacuate was increased to 30 km (18 miles) from the plant as people who have remained behind have now begun to run out of food, while the radiological contamination isn't getting any better.  With a dearth of sketchy information coming from this zone, including disturbing reports of radioactive corpses, some people have decided to brave the radiation and enter the zone, either legally or not.   This video , while not extremely illuminating gives us our first realistic portrayal of the conditions inside The Zone.  There are broken roads, abandoned towns, stray dogs & cows and occasional people in gas masks.  The brave/foolish pair who made the journey wisely took two geiger counters, and left them on, but seem to have the levels set quite low, as they beeped incessantly at the microSeivert levels, a far cry from the hundreds of milliSeiverts the Fukushima workers are getting.

Also inside the Zone, two AP reporters broke off from the officials who let them in, and discovered a man abandoned in his house since the quake!  He hadn't seen anyone for almost a month and braved near freezing temperatures at night.

The big news today is that the event was (finally) upgraded to Level 7 on the INES nuclear incident scale, from Level 5, leapfrogging over Level 6 entirely.   This puts Fukushima on the same level as Chernobyl, confirming the assessments made by the likes of Dr. Michio Kaku, Union of Concerned Scientists, and Arnie Gundersen of fairewinds.com, and disproving the flood of pundits put on the air by the mass media (many of them linked to the nuclear industry) who said "this is nothing like Chernobyl." There will always be ways in which the two disasters are different, but in terms of how much harm they are causing to humanity, they are now on par.

Nuclear Yakuza?

Mr. Ishizawa, 55, raced to the plant’s central gate. But a security guard would not let him out of the complex. ...“Show me your IDs,” Mr. Ishizawa remembered the guard saying, insisting that he follow the correct sign-out procedure. ... “What are you saying?” Mr. Ishizawa said he shouted at the guard. He looked over his shoulder and saw a dark shadow on the horizon, out at sea, he said. He shouted again: “Don’t you know a tsunami is coming?”

Mr. Ishizawa, who was finally allowed to leave, is not a nuclear specialist; he is not even an employee of the Tokyo Electric Power Company, the operator of the crippled plant. He is one of thousands of untrained, itinerant, temporary laborers who handle the bulk of the dangerous work at nuclear power plants here and in other countries, lured by the higher wages offered for working with radiation. Collectively, these contractors were exposed to levels of radiation about 16 times as high as the levels faced by Tokyo Electric employees last year, according to Japan’s Nuclear and Industrial Safety Agency

This harrowing account came from an excellent NY Times article which recounted similar to an account I blogged about earlier, in which workers were trapped inside the Fukushima reactor building as the tsunami approached.   What is remarkable about this article is that is revealed that almost 90% of the people working at Fukushima and all of Japan's nuclear power plants are unskilled temp. workers.   Underpaid and assigned the most dangerous jobs, these workers appear to be treated as "disposable".   Fifty have been diagnosed with leukemia and other cancers and recognized as deserving compensation, according to the NY Times article. Others may not be so recognized and still others may not be yet diagnosed.   Amazingly, when these workers tried to form a union, their leaders were beat up by thugs, a la some mafia/yakuza gangster movie.

The article points out how this situation is not only a disservice to these workers' rights, but also a serious safety issue.   The picture painted is astonishing when one thinks of the role of nuclear power in a hyper-modern society like japan. However, this whole picture makes a lot of sense from the corporate point of view.  It doesn't take much thought to realize the profit advantages of such low status workers.

On Friday I attended a presentation at SF State in which I heard from three Russian experts on Chernobyl, as well as got updates on Fukushima.    Testimony from Dr. Muchmediarova was most striking to me.  A biomedical expert called in to examine the radiological effects of Chernobyl on Pripyat and environs, she described seeing mutated trees with abnormal growths and enormous leaves.  She also gave very specific information on protecting humans from radiation dangers, which, to my relief corroborated what I've shared on this blog regarding Iodine, Cesium & Strontium.  The organizer of this event, SFSU Professor Phil Klasky, reminded us of the Iroquois maxim to take actions with the Seventh Generation in mind.  But when he mentioned that radioactive waste remains dangerous for tens of thousands of years, even the Iroquois seemed short-sighted!  If we are going to have fission plants producing waste, we need to be thinking about their effects on the 200th generation, or 500th.

This makes it clear in my mind that nuclear reactors cannot safely be put in the hands of corporations.  I'm not making (here) an argument that corporations are evil or inherently unhelpful to society.  Its just that the quarterly profit-driven nature of a corporation (and their short lifespans in the face of bankrupcy) is simply inherently at odds with fundamental facts of nuclear reactions (eg Plutonium's 24,000 year half life), and their effects on human, and other biology (eg. decadal timescale for getting thyroid cancer from I-131).     The only social structures which have any chance of persisting on radiological timescales are *stable* governments.    To call for nuclear power plants to be run by government, not corporations, is hardly "nationalization" because the liabilities of nuclear plants are already nationalized.   In the US, no nuclear plant can get insurance, so the government provides it at a huge subsidy.  Also nuclear plants are only liable for the first $12.6 billion in damages, the rest of the tab is picked up by US citizens.   This is hardly corporate capitalism, and indeed has been called "nuclear socialism".

A Hard Rain

It's been a few days since my last blog.  There's a lot to report from
Japan, but I'm going to focus on what's happening here in the US.  The
main news here in the San Francisco Bay Area is the results from
U.C. Berkeley's Nuclear Engineering Lab.  I strongly recommend their
site and its FAQ:

http://www.nuc.berkeley.edu/UCBAirSampling 

http://www.nuc.berkeley.edu/node/2044#lowdoserisk 

First, I should clear up some mis-reporting that occurred: So far
there have been no detections of hazardous levels of radiation in Bay
Area drinking water (as one might have interpreted when reading
certain recent headlines.) ...and drinking water has been tested.  So
tap water is safe at present, and this lab is continuing to test tap
water and I assume they will let us know ASAP if there is any
increase/risk from drinking tap water.

However, it is now clear that on March 17 and afterward radioactive
rain fell in the SF Bay Area.  From that date forward, detectable
levels of I-131 and Cesium have been discovered in rainwater samples
collected from the roof of Etchevary Hall in Berkeley (trivia: I used
to live on the same street, 1 block away from this building.  trivia2:
this building used to house a nuclear reactor!)  The highest recorded
reading for I-131 is 20 Bq/L recorded on 3/23.  (This reading means
that if you drank 1 full liter of that rainwater, then every second
there would be 20 radioactive decays in your body; every hour there
would be 72,000 decays) On other days, the readings were much lower,
(around 5 Bq/L) but still I-131 was detectable.

What to think about this?  The EPA limit for drinking water is 0.111
Bq/L, so the peak rainwater reading is 181 times over the limit.  More
relevantly, the average value is about 5 Bq/L, which is still about 6
times over the limit.  Here are some reasons why this figure is not an
automatic sign of serious danger:

1. you didn't drink that rain water, you've been drinking tap water
which is fine.
2. the EPA calculated that limit assuming the person would be exposed
to this level of radiation for a whole year.  So you'd need to drink 
that rain water for a couple of months  to exceed the EPA annual
max. dose.
3. *IF* the release of radioactive Iodine stops, then the I-131 
present in our environment now will be about 90% gone a month from now.
(due to the 8 day half life)

Here are some reasons to be concerned.

1. That rain fell on everything around here: roofs, gardens, farms,
streams.  Thus it can and will get into the food supply.  (UC Berkeley is
testing the food supply and has not found dangerous levels...yet)

2. If other isotopes, like Cs-137 are present, they will not decay
away quickly.  (30 year half life).  The tables on the site above
suggest that signficantly less Cs-137 is present than I-131.
However I didn't see a quote for the EPA limit on Cs-137

3. We don't know how long this will go on.  If the situation in Japan
continues to deteriorate, then we may well be getting "fresh" rains of
newly made I-131.  In this case the 1 year exposure time defined by
the EPA may come into play.  This is why it is important to look for
signs of continuing out-of-control nuclear reactions at the reactors in
Japan.

Note: the Berkeley site lists (in parentheses) numbers relating to
dosage of one airplane flight from SF to DC.  I don't put much value
in these numbers since they compare internal doses (eg. from food or
water) with external doses, eg. from air flights or X-ray machines.
However they do serve to remind us that we live in an environment has a
small level of radioactivity.  We always have & always will.

This site has an animation of an atmospheric model showing how the air
gets from there to here.

My Thoughts: Food is extremely safe now. We don't know how long this
will go on.  (Today's reports of increased risks of new Hydrogen
explosions at Fukushima Daiichi suggest no end in sight.)  As the
father of an infant, it seems prudent to me to stock up on any foods
that we can make last right now while they are still safe.  The
radioactivity in our food may go up, but will not go down.  I expect
it will never exceed the "unsafe" levels.  However these levels may
not be created w/ infants in mind.

My understanding is that there is no genuinely "safe" level of
radiation.  Every decay contains the possibility of causing damage to
our cells and our genes in particular, however small.  Since we live
with background radiation every day, we need not be concerned about
new radiation sources at the background level.  Its when our level of
exposure exceeds background that we need to start to consider taking
action.  Consider this question:

Assuming you drive every day, what is the safe level of not wearing
your seat belt?  No belt once per week (1/7) is certainly safer than
no belt ever.  Is neglecting a seat belt once per month a safe level?
After all, the odds of something happening are 1/30 times the odds of
getting in a crash in the first place.  A much safer approach would be
to ignore your seat belt only one day per year, every year.  This is
365 times safer than never wearing a belt.  Is that safe enough for
you or not?

My answer is: if you can take some precaution w/o causing additional
risk/harm, why no do it? This is why I just bought large quantities of
yogurt, (high Iodine, high Calcium which is chemically similar to
Strontium), strawberries (high Iodine) and seaweed (high Iodine)
bananas (Potassium, similar to Cesium).  I'm using these healthy foods
to make items (some frozen) to feed to my son over the coming weeks
and months.  These foods have elements we all need anyway, so there's
no downside, and the upside is the peace of mind of knowing that I've
taken a step to reduce the overall risks.

Oh, where have you been, my blue-eyed son? 
And where have you been, my darling young one? 
I've stumbled on the side of twelve misty mountains,
I've walked and I've crawled on six crooked highways,
I've stepped in the middle of seven sad forests,
I've been out in front of a dozen dead oceans,
I've been ten thousand miles in the mouth of a graveyard,
And it's a hard, and it's a hard, it's a hard, and it's a hard,
And it's a hard rain's a-gonna fall.
                      -Bob Dylan, A Hard Rain's a-gonna Fall

Toxic Dumping

A few days ago I commented that I was surprised to hear the media report that "dumping radioactive water into he ocean is not an option", given how "benign", (according to TEPCO) the effects of radioactive leakings to date had been.  Well, be careful what you blog about.   This scenario has now come to pass:

TEPCO has begun deliberately dumping  radioactive water in the Pacific.  In an almost Orwellian slight-of-hand, a spokesman said proudly that the water being dumped was radioactive at a low level only.  (by the way in this context 40,000% over the legal limit is considered "low level"!!).  Ok, so that means that no highly radioactive water is entering the ocean, right?  Think again.  

TEPCO is also stepping up efforts to stop highly radioactive water from leaking into the sea, and the company poured 13 kilograms of white bath agent.... ..

The high level stuff is going in accidentally, but it is going in.  Ok, raise your hand if you would be surprised to hear in few weeks that...ooops some of the "low level" dumping was a little higher level than we thought.   With dosimeters that max out a 1000 mSv, I'm not sure how anyone would know. Characteristically the story contains no actual measurements of water leaking or dumped nor does it state what the legal limit is (maybe we should know by now)

Here's a story that might portend how the installation of new nuclear power plants might be affected in the future.   Imagine if your town was considering getting a new nuclear plant.  Fill in the blanks with local names.

[   xxx  ]   and other town council members championed a plan to build two new reactors at the [] Nuclear Power Plant, a welcome addition of jobs and capital to the otherwise sleepy town of [ xxx ].  " We had no industry here. To flourish, our town needed the plant.”  he said.

In this article, the missing words are: "Fubata" town, Fukushima Daiichi power plant and  city councilman Shiro Izawa.   Instead of flourishing,  Fubata is now a nuclear ghost town and Mr. Izawa is now living in an emergency shelter (because of the meltdown, not quake).   His is new job is to figure out where all 6,900 of the town's residents should now live.

“The plant was supposed to be safe,” Mr. Izawa said at the shelter just outside Tokyo, 150 miles from Fukushima. “That was the promise...."

Related Kyodo headline:  "TEPCO to drop plan to add 2 reactors at Fukushima I nuclear plant". Ya think? Can you imagine if there were 8 reactors (5-6 in service) at the time of the quake?  

There's been extensive news on the rad. fallout in California...I'll try to write on that tomorrow

Corium

Chernobyl Corium

Corium....it sounds like the name of an element that you never learned about in chemistry class.  But its not an element at all; its a slang term in the nuclear industry for the "lava" that a reactor's core turns into after a meltdown.  Here's two photos of corium from previous infamous incidents.  First from the basement of Chernobyl:

Molten Uranium Fuel from Chernobyl called th "Elephant's Foot"

And second, here's what Three Mile Island looked like after the meltdown:

Three Mile Island after Meltdown

Since we have no photos of the Fuksushima cores which have melted down, we must presume they look something like this.   While the reports have so far have admitted "partial meltdowns" in reactors 1,2,3 and 4 (spent fuel pool), US Energy Secretary, Nobel Laureate Stephen Chu has now reported that reactor #1, (whose building exploded March 13) underwent a 70% meltdown. I wonder if he has actually seen a TEPCO photo of the reactor that is still being kept from the public?
Update:  NY Times reports that this info came from modeling of the meltdown(s).

Question for the day:  "At what point does a partial meltdown become a total meltdown"?  We've been told that a total meltdown is a much more serious event likely to result in much larger radiation release.  What then are we to make of a 70% meltdown?  And if reactor 2 and 3 underwent a 99% meltdown, would this still be considered "partial"?   How is that different from what has actually happened?

There's more evidence of sporadic re-crtiticality, that is, the reactors turning themselves on. This video mentions a  blue glow possibly due to ionizing radiation or (if under water) Cherenkev Radiation. Also I've found an excellent new site:

http://fairewinds.com

It contains videos by a guy who used to be in the nuclear power plant industry.  The April 3 video there presents the evidence for re-criticality.  I learned some things from this site's videos:

• Unlike, gamma, beta and Alpha radiation,  neutrons (produced by criticality) are hard to detect, and not being searched for extensively. Heck, TEPCO didn't even protect their workers with cheep  dosimeters.
• Those towers you see in the pictures are not ariels for radio transmission.  They were intended do disperse radioactivity high up in the air, but failed miserably after power went out.  This might be a good thing as this may have kept the radiation close to the ground.

Grim News

Today came the grim news that two workers at Fukushima Daiichi are dead.   The inference from the news so far is that they died as a result of the quake or tsunami, not from radiation, but no definitive statements are available.  It was revealed for the first time that the two have been missing for three weeks.  The bodies were actually discovered Wed (4 days ago), but the information has been withheld.   They were working on reactor 4, but according to this report, heroically ran to check the (lower) turbine rooms when the tsunami struck.

My comments on this tragic turn of events:

• Unlike a small fishing village devastated by a tsunami, a nuclear power plant has the ability to muster workers and determine who is missing, and conduct a search for them within hours if not minutes.  So the plant has known these workers were missing for weeks.
• The delay in finding the bodies suggests that the radiation environment around is/was so extreme that careful searches could not be conducted.   (The bodies had to be de-contaminated.)
• Either this or the urgency of dealing with the ongoing nuclear fires was so severe, that the fate of these missing coworkers could be ignored.
•  Unfortunately this announcement divulges a high degree of cover-up/withholding on the part of TEPCO, perhaps in conjunction with the Japanese govt.  To see this, consider a list of honest announcements that could have been made by TEPCO, but weren't:

Mar 11: Two workers missing at Fukushima Daiichi
Mar 13: Searches (if any) for missing workers unsuccessful
Mar 17: Two missing workers presumed dead
Mar 30: Bodies of workers found; names withheld.
Apr 2:  Dead workers identified.

These types of headlines would be reported in the US press, eg. in the case of missing mountain climbers, sailors, etc.   But all of the above was suppressed.  In the case of the quake and tsunami, there is a completely legitimate reason to withhold the names of the deceased for some time until their family have been tracked down and notified.

• This cavalier attitude with the truth calls into question many of the other TEPCO announcements/claims.  For example, I have noticed on two occasions when extremely high radiation levels are divulged, TEPCO announces one reading which then later gets questioned (eg by NISA), allowing TEPCO to say "we're sorry just ignore that initial reading".  My guess is that a number of legitimate radiation readings have now been dismissed after being combined with clearly false readings (like that of I-134)
• I'm surprised no reporter previously asked TEPCO leaders: "are any employees missing?".  Given the information to date, the best question for TEPCO right now is "what else are you hiding?".  For example, I strongly suspect they have close-up photos of the reactor cores and spent fuel pool showing serious damage, which are not being made public. 

R.I.P. Yoshiki Terashima & Kazuhiko Kokubo

Water

Recently there has been extensive discussion of radioactive water at Fukushima Dai-ichi.  Much of that water sprayed on the reactors and cooling pools either leaked out, splashed out or evaporated then re-condensed in the cold air and pooled on the floor, and in drainage channels between the buildings, and elsewhere. Three workers were hospitalized after stepping into highly radioactive water.

This water then overflowed and somehow drained out into the ocean where it is being monitored, at least sporadically.   Ocean level radiation reports have gone something like this:

"100 times legal limit today"

TEPCO response: nothing to worry about at this level since ocean will disperse it.
My response: "OK, 100x isn't so bad but higher levels would be worse right?"

Next day:  "500 times legal limit".  TEMPO response: nothing to worry about at this level

Next day: "1000 times legal limit".      Ditto.

You get the idea...its up to thousands of times the legal limit, but there's never any worry, since the ocean will always disperse.   This made me surprised to read in one article that "dumping all the radioactive water that has built up into the Pacific is not an option".   Well, why not?  It seems like, according to TEPCO, whatever amount is dumped, the ocean will always disperse it.

I wanted to find out more about the water and saw an excellent graphic on the Asahi news site, but in Japanese.  Fortunately my friend in Tohoku, Joey Fedrow, was able to translate, and I present these two graphics here, with his translation.  

Flow of Irradiated Water

Cross Section View of Water Storage

All this radioactive water accidentally drained into the Pacific (and any intentionally dumped) is supposedly no harm because fishing is prohibited w/in 20 km of the site (has this always been the case or is this a new closure?) , quoth TEPCO.   The best question I heard asked is: how is TEPCO going to ensure that fish in the irradiated water don't swim elsewhere, eg to fishing areas?   I'd like to know how far a typical seafish swims. 

In other news, TEPCO's stock is now trading at its lowest levels in 47 years, causing some to fear that a government takeover/bailout (like the one US banks got) will be needed.   The  80% loss from a level of 2000 to 400 yen per share means that the company's total value (or  "market cap.") has collapsed by 10's of billions of US$    I don't have any  insights into the fiscal implications of TEPCO's stock dropping down to 400 yen.  All I can say is:  "there's nothing to worry about at this level."