Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[BHamilton]

That is the reactor cavity and the columns are the bolts that hold the top (head) of the pressure vessel on.

The transfer canal leads toward the back under the fuel handling machine and the spent fuel pool would be under or behind the fuel handling machine.

Wow, that's some great fact checking there from the Daily Mail

 

[Maxion]

Wow, that's some great fact checking there from the Daily Mail

The media has been full of this ever since the disaster began. One of the largest papers in Finland ran a spread on the fukushima part of the japanese disaster, on pages 2-3 or the first spread and they had an illustration covering both pages where they showed the containment building blowing up and revealing the pressure vessel...

We also have the largest private-owned TV station reporting that radiation levels are about to reach lethal in Tokyo...

 

[rhody]

:-(
http://www.nirs.org/radwaste/atreactorstorage/alvarezarticle2002.pdf

To all,

After reading this nine year old document, to me, this is the most disconcerting of all presented in this thread, by far...

Rhody...

 

[jensjakob]

The media has been full of this ever since the disaster began. One of the largest papers in Finland ran a spread on the fukushima part of the japanese disaster, on pages 2-3 or the first spread and they had an illustration covering both pages where they showed the containment building blowing up and revealing the pressure vessel...

We also have the largest private-owned TV station reporting that radiation levels are about to reach lethal in Tokyo...

Is that channel trustworthy - or is it yet another tabloid tv?

The worst thing in Denmark is all the Tabloid media having a field-day, and it is hard to find good factual sources

 

[Maxion]

To all,

After reading this nine year old document, to me, this is the most disconcerting of all presented in this thread, by far...

Rhody...

It did seem a bit sensationalist. Did not contain any references nor did it answer the question of what exactly would burn in a storage pond. As we can currently guess, the fuel ponds at the Fukushima plants' reactors 1, 2, 3 and 4 are either dry or close to drying out yet no long-lasting fire has been seen. The only fire reported was the one at reactor for during or after the hydrogen explosion.

 

[Maxion]

Is that channel trustworthy - or is it yet another tabloid tv?

The worst thing in Denmark is all the Tabloid media having a field-day, and it is hard to find good factual sources

The idiotic thing is that both of them aren't tabloids, the paper I mentioned is a highly regarded paper that has won many awards around the world and the TV stations news broadcasts are usually the best in the country. This fear mongering is really annoying.

You should see the Finnish yellow press, they have been going insane.

 

[TCups]

In summary, so far, here are some things to ponder. Thanks to all earlier contributors. Please correct any mistakes I may have made.

Many years of spent fuel rods were stored in spent fuel pools (SFP) both in the 6 reactor buildings and in a 7th pool on site. The SFP's are lined with steel and encased in very thick concrete walls.

The SPF's are engineered so that there is no plumbing or drainage in the bottom of the pools to minimize the possibility of leakage, which would be catastrophic.

[PLAIN]http://nei.cachefly.net/static/images/BWR_illustration.jpg

Unlike the reactor vessels which are engineered with multiple, redundant cooling systems, the SFP's don't have the same multiple systems, and consequently the same options to potentially pump seawater into them in an emergency. Dose levels near the top railing of an uncovered pool would be lethal in less than a minute.

While reactor units 4, 5, and 6 were in cold shutdown, only the fuel rod assemblies (which were not completely spent or used up) from the #4 Unit had been removed from the reactor vessel and placed in the SFP, so, both spent and unspent fuel rod assemblies and therefore, a much larger heat load was present in the SFP of unit 4.

Explosions, probably from hydrogen, occurred in units 1, 2, 3, and 4. The hydrogen gas is a byproduct from a reaction of oxidizing zirconium casings from hot fuel rods and steam. Again, no fuel rods were inside the reactor core and primary containment of unit 4.

What first looked like this at unit 4 (again, with no fuel in the reactor core):
[PLAIN]http://i306.photobucket.com/albums/nn270/tcups/r735227_5964756.jpg

now looks like this:

[URL]http://www.spiegel.de/images/image-193170-galleryV9-njkp.jpg[/URL]
Reactor 4

[URL]http://www.spiegel.de/images/image-193230-galleryV9-ovfc.jpg[/URL]
Reactor 4

[URL]http://www.spiegel.de/images/image-193255-galleryV9-wbmd.jpg[/URL]
Reactor 4

The green structure you see is the fuel rod handling equipment that moves over the core and the spent fuel pool to transfer the fuel rod assemblies

I don't read German very well, but these are the radiation spikes measured and it looks like the largest measured spike on site, so far had something to do with an explosion and fire in Block 4, and that since that time, background (baseline) radiation levels have been steadily climbing:

[URL]http://www.spiegel.de/images/image-192946-galleryV9-pakh.jpg[/URL]

Seemingly desperate attempts are being made to get more water in the SFP at unit 4:

[URL]http://mit.zenfs.com/102/2011/03/AP11031702432.jpg[/URL]

the latest shots of the big hole in the side of unit 4 now show much more damage with additional lava-like stuff flowing out from above the original hole.

After the 9.0 quake and tsunami, even if it were called for, a mass evacuation in the absence of trains, roadways, fuel for cars and busses, etc. might not be possible in any effective way. Panicked citizens would be largely on foot. Any clothing and belongings they carried out with them would likely be contaminated.

The US State Department is paying for all US citizens to evacuate Japan.

Sayonara.

 

[jensjakob]

My bet is that it is not molten something, it is just soiled dirty insulation hanging out.

If it actually was something molten - my guess is that radiation would be way off the chart.

For the chart readings - it would be interesting to see if the spikes also co-relate to the dousing of the SFP and steam release?

And - do you have a source/link for "The US State Department is paying for all US citizens to evacuate Japan."? That would be kind of interesting.

Only source I could find so far is http://www.travel.state.gov/travel/cis_pa_tw/pa/pa_5388.html - stating explicitly that the law says that people has to pay themselves.

 

[TCups]

My bet is that it is not molten something, it is just soiled dirty insulation hanging out.

If it actually was something molten - my guess is that radiation would be way off the chart.

For the chart readings - it would be interesting to see if the spikes also co-relate to the dousing of the SFP and steam release?

And - do you have a source/link for "The US State Department is paying for all US citizens to evacuate Japan."? That would be kind of interesting.

Only source I could find so far is http://www.travel.state.gov/travel/cis_pa_tw/pa/pa_5388.html - stating explicitly that the law says that people has to pay themselves.

http://thehill.com/blogs/e2-wire/677-e2-wire/150365-state-department-green-lights-evacuations-from-japan-amid-reactor-crisis

Maybe they are backing off "paying for all US citizens" but I believe that is what I heard on one news source. Your guess is as good as mine. Maybe everything is OK with the SFP and that isn't molten metal. Maybe all that smoke and discoloration around the gaping holes and the melted metal structures in the sagging roof are just coincidental. Let's "hope", right?

 

[plasmaj]

Here is some positive news. This page shows radiation levels detected at various points in Japan. It has some history since the quake. Unfortunately data from the Fukushima prefecture are censured. However, it does have data from the prefecture immediately south, in Ibaraki.

http://www.targetmap.com/viewer.aspx?reportId=4870"

and below is the data for the prefecture (these are maximum of readings taken at various places within the prefecture). Following a spike in the early morning of March 16, the measured radiation has been declining since.The raw data can be found here http://www.bousai.ne.jp/eng/speedi/pref.php?id=08" . Consistently, the highest reading has been in Horiguchi Hitachinaka City.


3/15/11 19:40 1114
3/15/11 23:00 1065
3/16/11 0:30 1046
3/16/11 3:10 1030
3/16/11 6:00 2114
3/16/11 17:40 1044
3/16/11 19:50 1029
3/16/11 23:50 1011
3/17/11 3:00 993
3/17/11 16:40 881
3/17/11 19:20 876
3/17/11 21:40 872
3/18/11 1:00 856
3/18/11 18:00 763
3/18/11 20:50 760
3/19/11 1:00 749

 

[Astronuc]

The top photo is the north face of Unit 4 toward Unit 3.
The bottom photo is the south face of Unit 4.
They are two different sides of the same unit.

What first looked like this at unit 4 (again, with no fuel in the reactor core):

now looks like this:

Reactor 4.

 

[TCups]

The top photo is the north face of Unit 4 toward Unit 3. The bottom photo is the south face of Unit 4. They are two different sides of the same unit.

That is true. We concluded and discussed that earlier. As well as the probability that there are variations in the actual construction at the units and some of the schematics on line. And also concluded, I believe, that there are pools on both sides of the reactor -- one for fuel rod assemblies, and another for equipment that comes off the top of the reactor core, and that the overhead crane (and possibly the fuel handling machinery?) can move back and forth.

If that is insulation, then more of the insulation seems to be cascading down the side of the building now, and additional thermal damage has been done to the north face, the side closest to unit 3, above the site of the original square hole.

I don't know for sure what is happening inside the Unit 4 building, but it isn't good and it is still going on.

 

[STZ]

TCups While your concern is certainly not unfounded it seems that your posts are suggestive in nature all leading to doomsday conclusions... Do you really believe that Molton metal / what you describe as a "Lava Like Flow" would pile up on what is likely a galvanized piece of piping and not absorb it into the flow?

 

[jensjakob]

Thank you very much for the diagram of the SFP.

In meters I guestimate it to 14x14x12 meters = 2352 m3.

Lets say that 153 m3 is taken by fuelrods. Or even 352 m3.

Then there is still 2000 m3 water missing if the pool is dry. That is 2000 tons.

The dousingattempt #1 by firetrucks sprayed 30 tons of water.
The dousingattempt #2 by firetrucks sprayed 50 tons of water.

Lets say that 1/3 made it to the pool. No, let's be generous, let's say that 80% made it to the SFP. 80% og 80 tons = 64 tons = 64 m3.

That means that the pool still lacks 1936 m3 water...

Or let's calculate another way around.

64 m3 water, delivered to a surface of 14x12 meters (168 m2) = a rise in waterlevel of 38 centimeters.

Can someone here please tripplecheck my calculations and tell me that I am way off - or please redo my math and add the boil-off rate from the fuel-rods, and begin to tell people in Japan to evacuate?

Math is your friend.

 

[TCups]

I don't believe I used the word "doomsday" or suggested lethal or near lethal radiation levels anywhere other than at the top rail of a dry SFP

The direct comparison of the north face of unit 4 is this
http://i306.photobucket.com/albums/nn270/tcups/r735227_5964756.jpg
versus this
https://www.physicsforums.com/attachment.php?attachmentid=33222&d=1300451324

Can we agree that something very bad happened inside of Unit 4 in the absence of an an operating reactor, and that the damage, to me at least, seems much greater than might conceivably occur from a fire from generator oil? Might that fire or whatever it was contribute to the accelerated loss of water in the SFP? Does anyone here even know, with certainty, where the precise location of the SFP is in relationship to the building's exterior?

 

[Maxion]

If that is insulation, then more of the insulation seems to be cascading down the side of the building now, and additional thermal damage has been done to the north face, the side closest to unit 3, above the site of the original square hole.

Let's try and keep baseless speculation out of this thread. This thread has been the "cleanest" and most fact based discussion regarding this disaster that I have found so far.

Between the photo and the video they have dropped water via helicopter and have been using firefighting vehicles to spray water, and since this hole is quite low on the building it is not unfeasible that water that did not hit the pool flowed out through it dragging debris and dirt with it.

EDIT: Sorry for the poor quoting, the baseless speculation comment was aimed generally at this thread.

 

[Astronuc]

The problem is that we don't know the exact status of the SFP in any of the units, and until we see pictures, or someone publishes a reliable measure of the depth of water in the pools.

We also don't know the exact status of the fuel and cores of units 1, 2, and 3. For now, in the absence of direct evidence, we can only look from the outside of the damaged reactor buildings at the damage and ask - what would have caused that? Well - we did see explosions, fires, smoke or dust, and steam. The steam is obviously coming from boiled water, either in containment, SFP or both.

It may be the explosion of the containment of Unit 3 did most of the damage to Unit 4. Interestingly, the framework (girders and spans) of Unit 4 is still intact, although the panels got blown off. That indicates that if there was an explosion in Unit 4 upper containment, it wasn't so bad as to take out the framework. The panels are likely held on by metal screws.

Previously, there is a mention of 'melted' framework. I don't believe it is melted, but bulked or twisted (torsions), with large strains in some cases.

(One of my summer jobs during university was ironwork. I used to build metal buildings, and did the framework from floor to peak, and also did the sheet metal. I miss that!)

The smoke from Unit 4 could be burning oil or hyrdaulic fluid. It's not white, so it's probably not steam.

Each unit presents similarities, but is also a separate problem in and of itself.

 

[Maxion]

The problem is that we don't know the exact status of the SFP in any of the units, and until we see pictures, or someone publishes a reliable measure of the depth of water in the pools.

We also don't know the exact status of the fuel and cores of units 1, 2, and 3. For now, in the absence of direct evidence, we can only look from the outside of the damaged reactor buildings at the damage and ask - what would have caused that? Well - we did see explosions, fires, smoke or dust, and steam. The steam is obviously coming from boiled water, either in containment, SFP or both.

It may be the explosion of the containment of Unit 3 did most of the damage to Unit 4. Interestingly, the framework (girders and spans) of Unit 4 is still intact, although the panels got blown off. That indicates that if there was an explosion in Unit 4 upper containment, it wasn't so bad as to take out the framework. The panels are likely held on by metal screws.

Previously, there is a mention of 'melted' framework. I don't believe it is melted, but bulked or twisted (torsions), with large strains in some cases.

(One of my summer jobs during university was ironwork. I used to build metal buildings, and did the framework from floor to peak, and also did the sheet metal. I miss that!)

The smoke from Unit 4 could be burning oil or hyrdaulic fluid. It's not white, so it's probably not steam.

Each unit presents similarities, but is also a separate problem in and of itself.

This was noted on another forum but if you look a bit closer at the various photos that have been circling you can quite easily notice that framework and general construction of the containment buildings upper floor roof & walls of reactor building 1-3 is made of iron and concrete whereas the containment building of reactor building 4 seems to be made out of more heavy materials.

Also TEPCO in their latest press release admit to an explosion at unit 4.

http://www.tepco.co.jp/en/press/corp-com/release/11031901-e.html

And according to this release they have been spraying water on reactor no. 3 via different vehicles today and yesterday. From the radiation readings known from chernobyl I think we can safely say that the tongue sticking out is not corium. If it was they would most likely not be able to be close to reactor 3.

 

[Astronuc]

This was noted on another forum but if you look a bit closer at the various photos that have been circling you can quite easily notice that framework and general construction of the containment buildings upper floor roof & walls of reactor building 1-3 is made of iron and concrete whereas the containment building of reactor building 4 seems to be made out of more heavy materials.

As far as I know, the designs of units 2, 3, 4 and 5 are essentially identical, and probably used the same matierals. I don't know what heavier metals (heavier than Fe, Cr, Ni) would be used in construction. The sheets and framework might be thicker.

I worked on one metal building by the coast in Baytown Texas. The girders at the eaves and building ends were of a heavier gauge, and we doubled the density of girders at the eaves and ends in order to accomplish a high resistance to wind load. It was designed for 200 mph wind IIRC, or at least 175 mph, in order to resist the strongest hurricane or expected tornado.

 

[Maxion]

As far as I know, the designs of units 2, 3, 4 and 5 are essentially identical, and probably used the same matierals. I don't know what heavier metals (heavier than Fe, Cr, Ni) would be used in construction. The sheets and framework might be thicker.

I worked on one metal building by the coast in Baytown Texas. The girders at the eaves and building ends were of a heavier gauge, and we doubled the density of girders at the eaves and ends in order to accomplish a high resistance to wind load. It was designed for 200 mph wind IIRC, or at least 175 mph, in order to resist the strongest hurricane or expected tornado.

What I meant was it appears to be constructed more heavily, sorry English is not my main language :P

It seems the roof and walls of reactor unti 1-3 is made from steel girders whereas reactor unit four is made from a lattice work of concrete covered with concrete panels.

 

[jensjakob]

Does anyone have the exact measurements for the SFP?

 

[jensjakob]

I found a source of dimensions, (and description of SFP fires):
http://www.energyjustice.net/files/nuclear/security/nasrptsfp5.pdf

My initial estimates was a bit off.
Better dimensions are meters 11x12x12 = 1584 m3.

Still, the water added by the firetrucks are peanuts...

Racks can be 4 meters in height. 12x12x4 meters = 576 m3.

So if the SFP is #4 was empty, it would take 576 m3 water to just cover the racks...
A chrashtender holds approx 10m3 of water. If being able to deliver 100% - it would take 58 truckloads to fill the SFP just above the rack-height...

And that is with 100% deliveryrate and no boil-off...

Some-one, please prove my math wrong - I am getting a bad feeling about this

 

[Ms Music]

How do they even KNOW that SPF#4 burned dry? Isn't that complete speculation on their part? If there are no water temperature data from the last few days, I would think that meant that people had been in the buildings at one time, but no longer are able.

Or is #4 boiling dry news media hype? It is nearly impossible to filter facts...

 

[jensjakob]

Sorry, my mistake. WE have no facts about #4 SFP gone dry.

Best possible source, Gregory Jaczko:
http://www.nytimes.com/2011/03/18/world/asia/18nuclear.html?pagewanted=2

And;
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300273535P.pdf

 

[Astronuc]

How do they even KNOW that SPF#4 burned dry? Isn't that complete speculation on their part? If there are no water temperature data from the last few days, I would think that meant that people had been in the buildings at one time, but no longer are able.

Or is #4 boiling dry news media hype? It is nearly impossible to filter facts...

Well there are somethings that are known, and some speculation.

There is what the plant and utility have disclosed to officials, industrial and research institutions and media. Then there are officials, industry spokespersons, media and the consultants hired by those groups, or intervied in the media, and there is a mix of repeating the factual information (which could be wrong or misinterpreted) and speculation/conjecture.

Fortunately, being in the industry, I can pretty much tell when someone is bsing, or just wrong. I also know many folks within the industry in the US and abroad.

I've seen persons reported as experts and self-proclaimed experts provide incorrect and/or inaccurate information, on the details of Fukushima, as well as on the nuclear science and technology.

What I really don't appreciate is celebrity science experts providing comments on nuclear energy when they do not have direct experience in nuclear energy, and particulary in those areas in which I specialize.


As SFPs go, there has been a concern in the industry about the drying out of SFPs, usually in conjunction with an accident within the NPP. As far as I know, it's really considered hypothetical, but it has become a big deal for anti-nuclear groups and individuals. It's treated hypothetically, because it hasn't happened, until possibly now at Fukushima, and other than TMI-2, we haven't had a major accident at an NPP.

 

[jensjakob]

Why do they not provide new radiation measurements since 11.10 March 17th?
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300433768P.pdf

That worries me...

 

[Astronuc]

Why do they not provide new radiation measurements since 11.10 March 17th?
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300433768P.pdf

That worries me...

24 hr cycle. March 18th report should be posted March 19th, and March nth should be posted (n+1)th.

The data is collected, prepared, reported, and QA'd. The last part hopefully, particularly if the data fulfills a legal requirement.

 

[mugaliens]

It was designed for 200 mph wind IIRC, or at least 175 mph, in order to resist the strongest hurricane or expected tornado.

No doubt with a 2.5 factor of safety figured into it, as well.

 

[jensjakob]

24 hr cycle. March 18th report should be posted March 19th, and March nth should be posted (n+1)th.

The data is collected, prepared, reported, and QA'd. The last part hopefully, particularly if the data fulfills a legal requirement.

Then this procedure began after:
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300322727P.pdf

Before that report they updated the measurements in each release. Let's watch this closely, if they also keep on posting the old numbers tomorrow, I begin to notice it for real...

 

[swimmer]

[PLAIN]http://img40.imageshack.us/img40/7456/picture2adl.png

Could anyone put a perspective on the readings of monitoring post [32] located just outside the 30km zone?

Image is from http://www.mext.go.jp/component/a_menu/other/detail/__icsFiles/afieldfile/2011/03/19/1303727_15_1_2.pdf"

Found here: http://www.mext.go.jp/a_menu/saigaijohou/syousai/1303726.htm"

 

[Astronuc]

Could anyone put a perspective on the readings of monitoring post [32] located just outside the 30km zone?

Could be a local spike, and it could be transient. Either side 31 and 33 are lower, but higher than locations further S and W.

 

[rhody]

This thought has been with me all afternoon, from the http://www.guardian.co.uk/world/2006/mar/26/nuclear.russia" above from the quote in the article:

In fact, the reactor had serious design faults: when run at low power it was dangerously unstable and difficult to control; additionally, for the first four seconds after being inserted, the control rods would do the opposite of what they were supposed to - instead of slowing reaction, they would cause a sudden power surge. Under normal conditions these faults were not regarded as dangerous; but were the reactor ever to be pushed beyond its normal limits, they could prove catastrophic.

This is an academic question probably best for Astronuc,

"What design flaw and phenomenon is this ? and what could be done (if anything) today to prevent it ?"

Second concerning http://en.wikipedia.org/wiki/Gamma_ray" , scroll down to health effects, same article:

The most biological damaging forms of gamma radiation occur in the gamma ray window, between 3 and 10 MeV, with higher energy gamma rays being less harmful because the body is relatively transparent to them.

Why is the range from 3 to 10 million electron volts so damaging to human cells ?

Finally, a little further down, same article, under Body Response, can someone address this issue please ?

When gamma radiation breaks DNA molecules, a cell may be able to repair the damaged genetic material, within limits. However, a study of Rothkamm and Lobrich has shown that this repair process works well after high-dose exposure but is much slower in the case of a low-dose exposure.

Thanks...

Rhody...

 

[Reno Deano]

This is a real nice picture of a SFP, showing the door to the reactor compartment:
http://img.ibtimes.com/www/data/images/full/2011/03/17/75371-dd.jpg

So - can one of the problems in Fukushima be that this door is damaged, and that is why they can't keep the waterlevel up?

Does not make sense, since the picture show no gate in place and the water level is up? When in refueling mode the gate can be open or closed, but the reactor vessel water level is kept up (so gate is normally open) for shielding purposes.

 

[marwood]

There is what the plant and utility have disclosed to officials, industrial and research institutions and media. Then there are officials, industry spokespersons, media and the consultants hired by those groups, or intervied in the media, and there is a mix of repeating the factual information (which could be wrong or misinterpreted) and speculation/conjecture.

Fortunately, being in the industry, I can pretty much tell when someone is bsing, or just wrong. I also know many folks within the industry in the US and abroad.

On Wednesday U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko stated at a congressional hearing in Washington:
''Now, in addition to the three reactors that were operating at the time of the incident, a fourth reactor is also right now under concern. This reactor was shut down at the time of the earthquake. What we believe at this time is that there has been a hydrogen explosion in this unit due to an uncovering of the fuel in the fuel pool.
We believe that secondary containment has been destroyed and there is no water in the spent-fuel pool. And we believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.''
http://www.nrc.gov/about-nrc/organi...-gregory-jaczko/0317nrc-transcript-jaczko.pdf

As an official, perhaps the basis for Chairman Jaczko's statement was information from TEPCO staff. According to a Wednesday noon EDT report in http://www.chron.com/disp/story.mpl/ap/world/7475743.html
begin qoute -- Emergency workers ... resumed work after radiation levels dropped, but much of the monitoring equipment in the plant is inoperable, complicating efforts to assess the situation. "We are afraid that the water level at unit 4 is the lowest," said Hikaru Kuroda, facilities management official at Tokyo Electric Power Co. But he added, "Because we cannot get near it, the only way to monitor the situation is visually from far away." -- end quote

However, since Thursday TEPCO has been focussing visible efforts on dropping and shooting water onto the No3 reactor building to add water to the No3 SPF.

NHK TV reports of a helicopter video of the No4 building suggested that TEPCO officials had identified a patch of white seen at the edge of one of the rectangular black expanses framed by the remaining concrete frame of the south part of the east side of No4 was a reflection from water in the SPF. The video was similar or perhaps the same as the link in in a previous post

What degree of confidence could a plant operator or engineer put on identification of a blurred white dot appearing for a couple of seconds in a helicopter flyby as being an adequate level of water in an SPF?

Or is the reason for the re-prioritization of No3 over No4 more likely due to inability to get close enough to No4 to do anything effective, given the comments of Jaczko about radiation levels and the TEPCO facilities manager's comment?.

 

[AtomicWombat]

Thanks for the screenshot.
Check out Wikipedia to see what kinds of levels Chernobyl had. (They had Corium flowing around that place)

http://en.wikipedia.org/wiki/Chernobyl_disaster#Radiation_levels

Vicinity of the reactor core 30,000 Roentgens/hr
Debris heap at the place of circulation pumps 10,000 Roentgens/hr
Debris near the electrolyzers 5,000–15,000 Roentgens/hr

Again, hard to tell, but I don't think we're hearing about stuff on that order of magnitude.

BOTE calculation. See here:
http://www.asianewsnet.net/home/news.php?sec=1&id=17975"

"The radiation level at the scene before the operation was 4.13 millisieverts per hour at an altitude of about 300 meters and 87.7 millisieverts per hour about 100 metres above ground."

The inverse square law would imply a 9 fold increase in radiation from 300 metres to 100 metres. Instead we see a 87.7/4.13 = 21.2 fold increase. (I am still looking for data on gamma ray attenuation in air.)

Now the inverse square law strictly only applies to a point source. We can only extrapolate to the effective cross sectional area of the source from the angle of the helicopter. Let's extrapolate to 2 metres from the source (4 square metre cross section).

If we assume 4.13 millisieverts per hour at 300 metres and no attenuation, we would estimate 4.13*(300/2)^2 = 93000 millisieverts per hour = 93 sieverts per hour = 9300 REM/hr.

If we assume 87.7 millisieverts per hour at 100 metres and no attenuation, we would estimate 87.7 *(100/2)^2 ~ 220,000 millisieverts per hour = 220 sieverts per hour = 22,000 REM/hr ~ 22,000 Roentgens/hr.

These are Chernobyl-like estimates, but they are BOTE calculations and they ignore atmospheric attenuation.

Please check my calculations. I realize these are non-trivial conclusions. I'm hoping to find an error.