Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[jim hardy]

i just can't get excited by microscopic amounts of reactor protoplasm detected anywhere downwind.

I was active at another blog in the early days. Here's what i recall from the time.

We looked into the "Neutron Beams" when news reports of them first showed up. The false positive on CL38 combined with "neutron beams" was real scary.

.. From the plant logs available then it appeared the "beams" were measured at main gate's neutron monitor 12-15 March. A resident of Japan translated the newspaper reports for us and "beams" meant more like individual 'rays' or particles than an intense beam like a searchlight. That was consistent with the English version of press release which said less than 0.02uSv/h, which isn't a lot of neutrons.

At the time i proposed it was somebody walking past the monitor with contaminated boots.

Later we found that the times on logsheets were shortly after water injection. That made it seem obvious - ever pour water on a campfire and watch how much ash goes up with the steam?
I was unaware until recently their vessel was likely already breached at that time. If so, there's the path for flyash right around the SRV's into drywell. There are plenty of occurrences of phrase "PCV vent" in the IAEA report as early as March 12,,, Adobe search works well on M&M's one piece document.

maybe NucEng knows if that "PCV Vent" term infers bypassing the torus so flyash could go right out to the stack without scrubbing in Torus.

My point is it does not startle me that when a dried out reactor core gets suddenly hit by water it might sizzle and sputter and spew some ash-like particles that get wafted out with the steam and drift away. What does amaze me is our remarkable ability to measure it in minute amounts.

Some of the atoms in that reactor ash should be Pu, and all the other stuff they found in the car air filter described over at StrangeBeauty's ExSkf link comments section:

late May: "We tested an air filter from a car in Tokyo. It full of particles of strontium, metallic zirconium and Zr alloys, iron and steel encrusted with terbium, yttrium, lanthanum, and neodymium. There are bismuth/rhenium particles. One nearly pure strontium particle is crusted with sodium chloride, a k a seawater."

One assumes it was a radionuclide analysis, he didn't say.
He didn't say whether the car had been driven near the plant either.

The Sr coated in salt might suggest it was from some incore rowdiness associated with seawater injection. But -- that claim should be made by somebody who knows more chemistry than me.

There's my second point -- rehash can be useful to tie together loose ends from early observations, but we must remain vigilant against speculation and unsupported claims..

 

[Bioengineer01]

Assuming we are not being told everything and somethings are being actively hidder. The behavior of a US air craft carrier battle group may be relevant data to consider...

"...You have to remember at the time that Fukushima was in desperate need of diesel fuel for their generators and electricity to run the plant. The United States sent the USS Reagan and it’s carrier battle group (not the whole navy fleet).

They were reported to be steaming to Fuku and about 100 miles out when #3 blew. 100 miles in an aircraft carrier is about 3-4 hours travel time. The explosion happened just before nightly news time in the US – so all the news shows had live feeds on what was going on – because they hadn’t begun covering everything up yet.

So somebody on live TV revealed that the navy had detected “low level” radiation in the cloud and Reagan was diverting. This was met with surprise on the news, but accepted as normal. For those of us with military experience though, it meant much more. The Navy doesn’t divert an aircraft carrier on a mission. Those things are made to take on anything – (except for a MOX cloud I guess)..."

Reader comment: James2
June 8, 2011 at 7:38 am
http://enenews.com/govt-report-suggests-situation-worse-meltdown-worst-possibility-nuclear-accident
https://www.physicsforums.com/attachment.php?attachmentid=36260&stc=1&d=1307587734

 

[etudiant]

The Asahi Shimbun coverage of the TEPCO culture continues with segment 2.
http://www.asahi.com/english/TKY201106080182.html

It suggests that a long period of success and a strong desire to avoid creating any concerns had a debilitating effect on the flexibility of the operators, as well as on their detailed understanding of their systems under non standard conditions.

 

[Atomfritz]

Questions:

1. Where is the Japan CTBTO sensor? Are the peaks in CTBTO data correlated with wind direction to the sensor from the Fukushima site?

2. Have the peaks been checked for increases in other short half life isotopes?

3. If the peaks are due to short recriticalities shouldn't the increase be followed by an exponential decay from the new peak? It looks like they drop right back to the decay trend that was in place before the short peaks.

4. Shouldn't the Unit 1 drywell radiation detectors show some time delay to the CTBTO sensor unless that sensor is on site.

Regarding questions #1/2 see Bodge's post https://www.physicsforums.com/showpost.php?p=3342625&postcount=9081".

Regarding question 2: All these measurements have been and are being done, but no exact details published by Tepco (usually only I and Cs, as you know). Unless these are published one cannot rule out the possibility that there is something going on.

Regarding question 3: It would require relevant production of new FPs to make a relevant difference to a "background radiation" approaching 250 Sv. So can the absence of a decay ramp really be a proof that there is no oscillating recriticality in a small core part in the RB or CV?
Wouldn't this send out intensive radiation during reaction until dying out, and after that go unnoticed like an recently used, but now inactive "Slotin toy" probably would in this really big nuclear mess?

Regarding question 4: The distance of the sensors (100/200km) will, depending on the weather, eventually cause some phase and amplitude shift with the measurements on site (that usually are not published en detail). If I consider this there I cannot deny that to me there seem to be some coincidencies.

So how does plutonium get out of a nuclear reactor? Or spent fuel pond? It's not like the airborne isotopes, wafting about in the air, the steam, the smoke. Right?

It doesn't float or escape in a cloud of steam. Does it?

Yes, but not that easily like Iodine, Cesium or even noble gases for instance.
As Plutonium is very heavy and reactive, most of it usually clings to other material, making "hot particles".
Most of them fall down in a range of around 30 km, but some are distributed worldwide.

This btw is lesson learned from old russian nuclear mishap experience, so the 30km zone around Chernobyl.
Experience from many accidents/"experiments" has shown that more than 9/10 of the emitted plutonium goes down in a radius of 30km.

I have heard that soil chemistry is complicated.

It is, indeed. So the behavior of the various elements which we worry about some isotopes. In fact there has been much research. Just google "soil nuclide distribution" or such.

There could be hot spots of iodine on the debris/in the ground and then depending on how water is flowing/diluting we could see some sudden changes in the relative amount of cesium/iodine although this would not necessarily prove re-criticality.

Afaik iodine is one of the most volatile non-gaseous nuclear contaminants and mostly is present in ion form, I don't think that there are to be expected hot spots/hot particles like those of Plutonium, Strontium etc. So I doubt this a bit.

Interesting why they are installing this not in center of SFP, sfp is weakest there ?, the point where they are installing it is strongest I think (because of drywell thick): http://www.tepco.co.jp/en/news/110311/images/110607_1f_2.pdf

The spot marked in green on the bottom left diagram is where the steel support pillars will be - under the middle of the pool.

Looks like they'll also build a concrete wall at the red spot next to the dry well wall.

This worries me. The photos reveal interesting things.

1. It is interesting that the floor and ceiling of the room is not shown in the photos.
Are they already cracked? Is there danger of other cracks extending?
If not so, why then the support?

2. The support bars do not have diagonal reinforcement bars, as would be necessary to avoid deformation under load.
Instead they show mounting plates for mounting something like metal grouting forms.
This indicates they will probably mount steel plates as rebar and concrete form onto the pillars and pour in concrete, else the SFP support would probably not be very earthquake resistent.

How will they vibrate/compress the concrete correctly with that dangling SFP above them?
Or even drill/hammer out mounting holes in the floor, walls and ceilings etc?

Really scary construction site!

3. If the assumption is correct that they just fill the inner half of the room below the SFP with concrete this could make bad things even worse.
The walls are covered with thick epoxy painting, what makes up a very strong insulation. The concrete will not stick well to the wall, until this insulating paint cover is removed with demolition hammers, sanding etc.
There is no rebar connection to keep this heavy blob of concrete in place in case of a new heavy quake, as it does not adhere with the walls/floors.
So this loose giant thing will put heavy additional loads onto the already-weakened structure on the next big quake.

This kind of "support reinforcement" could finally pry open, crack and leak the still-intact SFP walls!

If Tepco is really so desperate doing such then I wonder what surprises this haunted plant still has for us what we have not been shown yet...

 

[razzz]

Since while replacing the shroud and rearranging the spent fuel pool to carry the load of at least two cores worth of assemblies and it didn't fail during a 9+ quake with aftershocks, I'd say the chances are good of propping up the pool to withstand the next great quake. Appearing dry and clean it amazes me that they can actually work in there.

 

[westfield]

Interesting why they are installing this not in center of SFP, sfp is weakest there ?, the point where they are installing it is strongest I think (because of drywell thick): http://www.tepco.co.jp/en/news/110311/images/110607_1f_2.pdf

Perhaps their concern is the fuel handling machine falling into the pool of RB #4?

And\ or, yes as you have noticed, perhaps another reason is that particular place has the best support from below, ie, the concrete to be poured will largely place load on the super strong containment structure itself, rather than the less strong reinfoced concrete framework & floor of the surrounding RB.

Or some other reason that is nothing at all to do with the above.

 

[rowmag]

If we post a link to original copyright owner site, is that OK? I know the PF posting guidelines recommend not quoting large portions of articles to prevent violation of copyright information.

They don't have fixed links to articles on their site. You have to sign up for a "trial mail," wherein they send you a temporary link to an article, in exchange for the right to send you notices -- presumably enticements to sign up for a full subscription so you can keep up with the latest developments in Japanese civil engineering. Who knows, you might become addicted. Even if you don't, by going through the publisher-approved route to get the paper, you will have at least boosted their click/circulation numbers, which they may appreciate. And the clean conscience is yours to keep for free.

Let me recap the proper process.

To download a paper on TEPCO's civil engineering for the Fukushima Daiichi site, which was published in the journal "Civil Engineering Technology" in 1967, click here:

Part 1: http://www.doboku-g.com/DownloadPDF.aspx?TocID=6608
Part 2: http://www.doboku-g.com/DownloadPDF.aspx?TocID=6637

In the middle of the page that shows up, there is a blue box, inside of which you have to provide a mail address twice (and not an obviously free mail address), check a box to the lower left agreeing to let the journal send you notices now and then, and click on the button in the lower right. With this you will be mailed a URL from which to download the PDF file.

 

[razzz]

If remember right, Japan failed to inform the US Navy Unit 3 just had vented itself.
Nuclear fallout plays havoc with a nuke carrier's sensors, bet they were looking for an on-board nuke leak first or at least their instruments alerted them to high concentrations. Of course being somewhat educated, they left the area.

 

[westfield]

This worries me. The photos reveal interesting things.

1. It is interesting that the floor and ceiling of the room is not shown in the photos.
Are they already cracked? Is there danger of other cracks extending?
If not so, why then the support?

2. The support bars do not have diagonal reinforcement bars, as would be necessary to avoid deformation under load.
Instead they show mounting plates for mounting something like metal grouting forms.
This indicates they will probably mount steel plates as rebar and concrete form onto the pillars and pour in concrete, else the SFP support would probably not be very earthquake resistent.

How will they vibrate/compress the concrete correctly with that dangling SFP above them?
Or even drill/hammer out mounting holes in the floor, walls and ceilings etc?

Really scary construction site!

3. If the assumption is correct that they just fill the inner half of the room below the SFP with concrete this could make bad things even worse.
The walls are covered with thick epoxy painting, what makes up a very strong insulation. The concrete will not stick well to the wall, until this insulating paint cover is removed with demolition hammers, sanding etc.
There is no rebar connection to keep this heavy blob of concrete in place in case of a new heavy quake, as it does not adhere with the walls/floors.
So this loose giant thing will put heavy additional loads onto the already-weakened structure on the next big quake.

This kind of "support reinforcement" could finally pry open, crack and leak the still-intact SFP walls!

If Tepco is really so desperate doing such then I wonder what surprises this haunted plant still has for us what we have not been shown yet...

re 1. - Perhaps their concern is the fuel handling machine falling into the pool.

re 2. - formwork doesn't need diagonals as the face of the formwork itself when fitted braces the formwork. re setting the concrete, vibration would be fine and finishing with an expanding grout would be the norm in any situation where new concrete structure is required to "pick up" existing load.

re 3 - It would be no problem to fix steelwork to the existing concrete structure. Even if the epoxy coating was removed as you suggest, there would be no proper bond of any strength between old and new concrete. If they have that concern then it's easily negated by fixing steel before the pour.

imho, in the scheme of things there is nothing wrong with the pool as such at the moment but there is a concern about the fuel handling machine or other heavy item falling in the pool and overloading its floor. I have no evidence whatsoever to back up that idea.

 

[NUCENG]

The source says it exceeds 100 Sv/h at that stage, so the number is >100 Sv/h.



I suppose an expert could do a better job than I, otoh since in the context it is more a question of producing a rough order of magnitude estimation.. :-)

If the spent fuel after ten years in the pool is at >100 Sv/h, I'd expect it to be at >1000 Sv/h after one year in the pool, and plausibly at >10000 Sv/h at the time of removal from the core, i.e when the fuel has been fully spent. So, doing simple interpolation I'd find it plausible that half spent fuel could have an activity of >5000 Sv/h, give or take one order of magnitude.

I did some rough calculations to get estimates of dose rates due to fresh fuel being ejected. I used a simplifying assumption that gamma and beta radiation of all energies have the same effective dose rate. As a result I believe the results are probably within one order of magnitude of a more detailed calculation. It only considers external dose and neglects neutron and alpha radiation effects.

A complete bundle at the instant of shutdown near end of useful life will produce about 9000 Sv/hr at 1 m distance.

An average fuel pellet at shutdown at 1 m will produce a dose rate of about 500 mSv/hr at 1 m and a contact reading of 500 Sv/sec on contact,

The decay rate will follow the fractional trend as follows:

1 sec 30 min 1 hour 8 hours 1 day 4 days 30 days 90 days 180 days
9.92E-01 5.48E-01 4.53E-01 2.46E-01 1.85E-01 1.20E-01 4.66E-02 2.31E-02 1.24E-02

1 year 3 years
5.82E-03 2.40E-03

 

[elektrownik]

Can someone look at my post about unit 5 here: https://www.physicsforums.com/showpost.php?p=3346232&postcount=9333
I don't understand still what they were doing there, if the reactor was at 7MPa it must be on ? I don't remember information about scram in unit 5, it was reported always as cold shutdown

 

[sp2]

Since while replacing the shroud and rearranging the spent fuel pool to carry the load of at least two cores worth of assemblies and it didn't fail during a 9+ quake with aftershocks, I'd say the chances are good of propping up the pool to withstand the next great quake. Appearing dry and clean it amazes me that they can actually work in there.

I have to say, I'd draw the opposite conclusion.

They didn't have a 9 at Fukushima, they had a 9 a hundred miles out to sea.
What they got at the plant (if I remember correctly) was more like a 6.8, or something in that ballpark.
And that was *still* enough to give them some shakes that actually *exceeded* their design limits.
Similarly, the big 7+ after-shake a month later was enough to shake some meters at Onagawa beyond *its* rated limits.

Clearly, whatever the level of Dai-ichi-4's shake-resistance now, it's got to be lower than before (and possibly a *lot* lower).

The combination of these simple facts should be enough to scare the crap out of any objective analyst, and to convince us that a large after-shock in the near vicinity of Dai-ichi is entirely capable of bringing something down.

Since the seismological theory holds that very-large quakes are capable of producing after-shocks as big as 1 point below their initial magnitude, we can probably conclude that there's still *plenty* of reason for concern.

 

[NUCENG]

Regarding questions #1/2 see Bodge's post https://www.physicsforums.com/showpost.php?p=3342625&postcount=9081".

Regarding question 2: All these measurements have been and are being done, but no exact details published by Tepco (usually only I and Cs, as you know). Unless these are published one cannot rule out the possibility that there is something going on.

Regarding question 3: It would require relevant production of new FPs to make a relevant difference to a "background radiation" approaching 250 Sv. So can the absence of a decay ramp really be a proof that there is no oscillating recriticality in a small core part in the RB or CV?
Wouldn't this send out intensive radiation during reaction until dying out, and after that go unnoticed like an recently used, but now inactive "Slotin toy" probably would in this really big nuclear mess?

Regarding question 4: The distance of the sensors (100/200km) will, depending on the weather, eventually cause some phase and amplitude shift with the measurements on site (that usually are not published en detail). If I consider this there I cannot deny that to me there seem to be some coincidencies.
..

I don't find a wind direction correlation, but the met data is only for Fukushima and you may need to know what the wind direction was at the transport time before the measured reading at the CTBTO sensor.

Question 3 is about the graph which shows I-131. The base decay rate is about a half life of 8 daya. The individual peaks are about a factor of 10 and if they aren't due to wind I would expect that they would decay from the new peaks at about an 8 day half life. Inmstead the drop back an order of magnitude in as little as one day. That now seems to confirm what I was trying to find in questions 1 and 2.

Question 4 The problem with the met data provided is that it is an average direction and windspeed for a 24 hour period. If the wind speed is less than 10 km/hr there will be nearly a full day time shift from the peak at Fukushima to a sensor 200 km away. The peaks that seem to corelate seem to have no time shift.

 

[razzz]

Can someone look at my post about unit 5 here: https://www.physicsforums.com/showpost.php?p=3346232&postcount=9333
I don't understand still what they were doing there, if the reactor was at 7MPa it must be on ? I don't remember information about scram in unit 5, it was reported always as cold shutdown

Decay heat? Assemblies need constant water circulation to remove the heat, can't be left alone unattended unless they can be committed to air cooling.

 

[razzz]

I have to say, I'd draw the opposite conclusion.

They didn't have a 9 at Fukushima, they had a 9 a hundred miles out to sea.
What they got at the plant (if I remember correctly) was more like a 6.8, or something in that ballpark.
And that was *still* enough to give them some shakes that actually *exceeded* their design limits.
Similarly, the big 7+ after-shake a month later was enough to shake some meters at Onagawa beyond *its* rated limits.

Clearly, whatever the level of Dai-ichi-4's shake-resistance now, it's got to be lower than before (and possibly a *lot* lower).

The combination of these simple facts should be enough to scare the crap out of any objective analyst, and to convince us that a large after-shock in the near vicinity of Dai-ichi is entirely capable of bringing something down.

Since the seismological theory holds that very-large quakes are capable of producing after-shocks as big as 1 point below their initial magnitude, we can probably conclude that there's still *plenty* of reason for concern.

I get what you are saying but is there a better plan for Unit 4 at the moment? It is just like not letting basements overflow with contaminated cooling water or the site itself will become 'hot,' pumping contaminated water out to sea while sad is the only option until storage is completed.

 

[MiceAndMen]

I get what you are saying but is there a better plan for Unit 4 at the moment? It is just like not letting basements overflow with contaminated cooling water or the site itself will become 'hot,' pumping contaminated water out to sea while sad is the only option until storage is completed.

If it were my plan the Unit 4 SFP would be empty by now. Or pretty close to it depending on what fuel assemblies had clear vertical paths up and out of the water.

 

[elektrownik]

Decay heat? Assemblies need constant water circulation to remove the heat, can't be left alone unattended unless they can be committed to air cooling.

Yes, but this wasnt question, the problem is what is "stress test" and could reactor have such pressure without turning on ? Now unit 5 is at atmospheric pressure, but during earthquake it was 8MPa...

 

[~kujala~]

Afaik iodine is one of the most volatile non-gaseous nuclear contaminants and mostly is present in ion form, I don't think that there are to be expected hot spots/hot particles like those of Plutonium, Strontium etc. So I doubt this a bit.

Okay. I noticed there was a more sophisticated discussion about iodine/cesium levels also in another thread:
https://www.physicsforums.com/showpost.php?p=3342335&postcount=294

 

[razzz]

Yes, but this wasnt question, the problem is what is "stress test" and could reactor have such pressure without turning on ? Now unit 5 is at atmospheric pressure, but during earthquake it was 8MPa...

I'm sorry but your quote said it had a full load in the core and I take it the pressure test was done just before start up or re-starting. Whether they were pumping air to pressure check seals and for other leaks or using the heat generated by the fuel assemblies for the pressure check, the test was interrupted and they had a loss of cooling circulation for whatever reason and then the decay heat continued building up until cooling circulation was reestablished and lowered the pressure. And yes with no cooling water circulation with assemblies in the core, it is going to heat up no matter what just from decay heat. They got cooling circulation back and the heat that caused the pressure build up is gone now or it would heat up/pressurize and blow the seals or something else.

 

[sp2]

I just now recalled that I posted this here, a month or so ago (#5257):

<<When TEPCO tells me it's 10% of Chernobyl, I'll assume it's most likely at least 20%, and I'm fairly sure that I at least won't be way high.
Could I be way low? Yeah, I suppose so, but I'll wait for better evidence to support that.
(And, if it *is* way low, there will surely be evidence of that, eventually. Even if it takes a while to seep out, so to speak.)>>

So what did they announce yesterday? That it's more like 20%.

(I'm now working off the assumption it's probably really more like 40%, but we'll see what happens.)

 

[MiceAndMen]

Yes, but this wasnt question, the problem is what is "stress test" and could reactor have such pressure without turning on ? Now unit 5 is at atmospheric pressure, but during earthquake it was 8MPa...

Notice the JAIF daily reports now show the number of fuel assemblies loaded into Units 5 & 6 on 11 March: http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1306813176P.pdf

I was following those reports several times a week but stopped looking at them back in April. When did they start reporting that? And why did they not report it from the beginning? It certainly looks like both Units 5 and 6 had full loads of fuel at the time of the earthquake, and that is definitely NOT what TEPCO led everyone to believe back then.

 

[razzz]

If it were my plan the Unit 4 SFP would be empty by now. Or pretty close to it depending on what fuel assemblies had clear vertical paths up and out of the water.

You are asking a lot there. Clean the mess up on the refueling floor, get the fueling crane and equipment working, find a place to store the fuel and all this has to be done underwater and in water. The assemblies can't be exposed to air so how do you get the assemblies transported anywhere in water and stay cool.

 

[razzz]

I just now recalled that I posted this here, a month or so ago (#5257):

<<When TEPCO tells me it's 10% of Chernobyl, I'll assume it's most likely at least 20%, and I'm fairly sure that I at least won't be way high.
Could I be way low? Yeah, I suppose so, but I'll wait for better evidence to support that.
(And, if it *is* way low, there will surely be evidence of that, eventually. Even if it takes a while to seep out, so to speak.)>>

So what did they announce yesterday? That it's more like 20%.

(I'm now working off the assumption it's probably really more like 40%, but we'll see what happens.)

I think that 10% was for a 30 day time frame. The cumulative totals must be near 50% by now and continues to tally up.

 

[MiceAndMen]

You are asking a lot there. Clean the mess up on the refueling floor, get the fueling crane and equipment working, find a place to store the fuel and all this has to be done underwater and in water. The assemblies can't be exposed to air so how do you get the assemblies transported anywhere in water and stay cool.

Perhaps, but I would have done as little cleanup of the refueling floor as possible, used a regular crane and had a fleet of trucks with open water tanks ready to receive each assembly as it came down. Park the truck, evacuate the driver until the assembly was safely underwater, and send him back into get the assembly out of there. One at a time. Might take an hour or two for each one, but it would be done.

If the assemblies couldn't withstand being exposed to the air for 5 minutes (hopefully less), then perhaps the older ones that were less "hot" could.

 

[razzz]

Perhaps, but I would have done as little cleanup of the refueling floor as possible, used a regular crane and had a fleet of trucks with open water tanks ready to receive each assembly as it came down. Park the truck, evacuate the driver until the assembly was safely underwater, and send him back into get the assembly out of there. One at a time. Might take an hour or two for each one, but it would be done.

If the assemblies couldn't withstand being exposed to the air for 5 minutes (hopefully less), then perhaps the older ones that were less "hot" could.

Exposed assembly easily irradiates everything within 3 feet of it hence the need for water containment. How long would it take to boil off a tank of water, say about 3x its size would be a good question. The nearest storage pool is the common pool which I think has more assemblies in it than all the intact reactors and the intact SFPs combined. Have make room in that pool first.

 

[MiceAndMen]

I was following those reports several times a week but stopped looking at them back in April. When did they start reporting that? And why did they not report it from the beginning? It certainly looks like both Units 5 and 6 had full loads of fuel at the time of the earthquake, and that is definitely NOT what TEPCO led everyone to believe back then.

Reply to self: Apparently I stopped looking at those reports much earlier than I realized. The first one that reported on the number of fuel assemblies loaded into the reactors was the afternoon report from 23 March http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300882515P.pdf

Prior to that they reported the status of loaded fuel assemblies at Units 5 & 6 to be "Not Damaged", so maybe I wrongly assumed there was not fuel loaded. See early morning report from 23 March http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300842324P.pdf .

I did download the 20 April report and the numbers are clearly in the report; I just didn't notice them.

What is noticeable is that right up until the reports of 19 March http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300544332P.pdf they listed the status of "Core cooling requiring AC power" and "Core cooling not requiring AC power" as "Not necessary" for both units 5 & 6. For an entire week someone wasn't telling the complete truth, be it TEPCO or JAIF.

 

[sp2]

I think that 10% was for a 30 day time frame. The cumulative totals must be near 50% by now and continues to tally up.

Well, it's certainly not thought to be linear.
TEPCO seems to suggest that it's been negligible after the first two weeks, so that initial total roughly equals THE total.

(Not that I necessarily *believe* that, but I think that's the 'official position.')

One thing I'm pretty confident of: the new number will eventually be exposed as nonsense, just like the old number was.

Then all the 'nuclear experts,' who pompously told us again and again that "this is nothing like Chernobyl; anyone who says it is is an idiot" are going to be even more red-faced than they already are.

And they should be mercilessly held to account for it.

 

[MiceAndMen]

Exposed assembly easily irradiates everything within 3 feet of it hence the need for water containment. How long would it take to boil off a tank of water, say about 3x its size would be a good question. The nearest storage pool is the common pool which I think has more assemblies in it than all the intact reactors and the intact SFPs combined. Have make room in that pool first.

Yes, I remember learning early on that the water was just as important as a radiation shield as it was a coolant. They could have also dug out something like Sellafield's Dirty-30 up the road fairly quickly without the reactor buildings too close by.

It might be unworkable as a plan, but I would have most definitely put it on the table. Even emptying a half, or a third would have decreased the weight and thermal load significantly.

You wouldn't want to lift an assembly out and find it damaged, of course, that would spew fission products into the air, but as I recall the water sampling and video from 8 May showed very little damage. I also would have prioritized that task, not waited 2 months.

 

[NUCENG]

i just can't get excited by microscopic amounts of reactor protoplasm detected anywhere downwind.

I was active at another blog in the early days. Here's what i recall from the time.

We looked into the "Neutron Beams" when news reports of them first showed up. The false positive on CL38 combined with "neutron beams" was real scary.

.. From the plant logs available then it appeared the "beams" were measured at main gate's neutron monitor 12-15 March. A resident of Japan translated the newspaper reports for us and "beams" meant more like individual 'rays' or particles than an intense beam like a searchlight. That was consistent with the English version of press release which said less than 0.02uSv/h, which isn't a lot of neutrons.

At the time i proposed it was somebody walking past the monitor with contaminated boots.

Later we found that the times on logsheets were shortly after water injection. That made it seem obvious - ever pour water on a campfire and watch how much ash goes up with the steam?
I was unaware until recently their vessel was likely already breached at that time. If so, there's the path for flyash right around the SRV's into drywell. There are plenty of occurrences of phrase "PCV vent" in the IAEA report as early as March 12,,, Adobe search works well on M&M's one piece document.

maybe NucEng knows if that "PCV Vent" term infers bypassing the torus so flyash could go right out to the stack without scrubbing in Torus.

My point is it does not startle me that when a dried out reactor core gets suddenly hit by water it might sizzle and sputter and spew some ash-like particles that get wafted out with the steam and drift away. What does amaze me is our remarkable ability to measure it in minute amounts.

Some of the atoms in that reactor ash should be Pu, and all the other stuff they found in the car air filter described over at StrangeBeauty's ExSkf link comments section:



One assumes it was a radionuclide analysis, he didn't say.
He didn't say whether the car had been driven near the plant either.

The Sr coated in salt might suggest it was from some incore rowdiness associated with seawater injection. But -- that claim should be made by somebody who knows more chemistry than me.

There's my second point -- rehash can be useful to tie together loose ends from early observations, but we must remain vigilant against speculation and unsupported claims..

PCV vent the way it is used may be either venting from the drywell (dry venting) or the preferred path - the wet or Wetwell vent from the torus air space. If you have melted and aerosolized fuel and fission products in the drywell venting from the wetwell scrubs the release through the suppression pool. SRV venting from the RPV also discharges below the waterline in the torus. vaporized fuel or heavy metals could be released directly into the drywell through piping leaks or breaches in the RPV. Dry venting of containment, containment leakage or breaches could then release vaporized fuel and aerosols. Subsequent hydrogen explosions could eject that contamination like your concept of reactor ash.

I don't believe "chunks of fuel could be ejected from the vessel in any of these paths. If chunks of fuel were ejected it would be more likely they would come from the spent fuel pools. My calculations for the unit 4 pool indicate the fuel there remained covered. hydrogen from the pool would have detonated above the pool and would probably not eject fuel from the building. In the case of unit 3 the fuel in the spent fuel pool was older and would have been slower to boil. I don't believe this would have been able to drain the pool. If there were leaks in the pool sufficient to uncover fuel before the explosion, this could have ejected fuel from the pool. I haven't been able to prove or disprove this with the reported volumetric makeup to the pool since the explosion. We still haven't seen whether the drywell cap and or RPV head remain in place for possible fuel ejection from the core. However, this path would also require ejecting the steam dryers, and separators as well as the RPV head and Drywell CAP.

So I am doubtful of any reports of "pieces of fuel" miles from the plant site. If there are fuel and plutonium deposits, they are probably microsco[ic particles of fuel that were small enough to behave like "ash." If they are actually measuring multiple isotopes of plutonium it is possible they can conclude that it came from the accident and not from atmospheric testing. Remeber that gram for gram, the long half life of plutonium or uranium isotopes is also going to result in fairly low decay rates (Bq/sec) compared to other fission products like cesium. If they are finding and burying hot spots it probably isn't plutonium or uranium.

 

[razzz]

Unit 3 SFP is the obvious suspect for losing it fuel assemblies as the updraft would take anything not bolted down with it and then some. Looks like plenty of heat generated to flash the pool water to steam and then excite the assemblies. They are not telling us what fallout was measured in yard sensors during the Unit 3 blast yet.

 

[joewein]

Can someone look at my post about unit 5 here: https://www.physicsforums.com/showpost.php?p=3346232&postcount=9333
I don't understand still what they were doing there, if the reactor was at 7MPa it must be on ? I don't remember information about scram in unit 5, it was reported always as cold shutdown

The reactor was probably shut down but with the fuel loaded and undergoing a leak test using nitrogen fed via a compressor (I don't think they would use air, because air at 70 bar would give 14x the oxygen of pure oxygen at atmospheric pressure, which would be a fire hazard).

When the power failed, the pressure must have increased due to steam from the water in the core boiling from decay heat of the loaded fuel. They then performed alternating "feed and bleed" operations, allowing the steam release valve of the reactor pressure vessel to vent steam into the containment and topping up again with water from the condenser tank.

They sure must have been glad to have one surviving diesel between unit 5 and 6, or there would now be 5 melted cores at Fukushima 1 instead of 3 of them.

 

[NUCENG]

Perhaps, but I would have done as little cleanup of the refueling floor as possible, used a regular crane and had a fleet of trucks with open water tanks ready to receive each assembly as it came down. Park the truck, evacuate the driver until the assembly was safely underwater, and send him back into get the assembly out of there. One at a time. Might take an hour or two for each one, but it would be done.

If the assemblies couldn't withstand being exposed to the air for 5 minutes (hopefully less), then perhaps the older ones that were less "hot" could.

Some things need to be included in considering offloading fuel with an external crane:

1. Debris or damage to fuel assemblies in the pools may make movement risky of further damage and radiation release.

2. Fuel assemblies are easily damaged by side loads so they need to be supported in whatever vessel or tank is used for the transfer.

3. If you provide sufficient support to prevent damage during transfer you need very fine control of location and speed of movement into the transfer support.

4. Movement in air will cause rapid heating and very intense radiation fields.

5. The transfer will be exposed to wind and elements.

6. A commercial grade crane could fail during transfer. If the assembly is out of the water when this happens it could get dicey. If the failure results in a dropped rod that would be bad.

7. What happens if there is another seismic event during transfer?

Supporting and protecting the pools and leaving the fuel there may not be best option but it also might not be the worst.

 

[SteveElbows]

I think that 10% was for a 30 day time frame. The cumulative totals must be near 50% by now and continues to tally up.

Thats really not a safe assumption at all. All data we have points to some very large releases in the early days, but no really large releases since then. Estimated daily releases, when added up over weeks or months, would amount ot a significant event on their own. But compared to the early releases, they don't seem hugely significant, and they certainly don't push the estimates up to 50% of Chernobyl.

Also some people & the media tried to have it both ways with the revised estimate. First let's be clear that these are not TEPCO estimates, rather estimates were provided by 2 different nuclear agencies within Japan. One of these estimates has now doubled, but it was the lower of the two estimate originally, and so at the time everyone ignored this one anyway and focussed on the bigger number. So its a little bit misleading to just paint this updated estimate as a doubling of what we previously heard, because mostly everyone ignored this lower estimate in the first place.

Really there are 3 ways I can think of that the estimates will leap to levels significantly closer to that of Chernobyl than the current estimates:

They could simply decide that the estimates were wrong, and bump the numbers up one day.

A significant new event on site causing a significant new release.

A problem with the highly contaminated water on site, water that was recently estimated to contain about as much radiation dose as these total air release estimates.


Personally I think total release estimates are useful but for the most accurate picture that focusses on real-world implications, the actual levels of contamination at various locations around Japan and beyond is what I look at.

 

[joewein]

After reading the article on ex-skf site (http://ex-skf.blogspot.com/2011/06/fukushima-iis-contaminated-water-cobalt.html) about the water in the basement at Daini, I tried to check the official government report to the IAEA about Daini (http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iii-3.pdf) and how all the info jives. But, as too often, I'm way out of my depth here.

Therefore, my question:
How do the report of tsunami-caused seawater in the basement and the info as posted and referred to above by others fit with what's in the report to the IAEA?

"Japan Atomic Power Co. has been surveying traces of how high the tsunami ran up on the NPS site. The results are shown in Figure III-3-8. The tsunami marked traces as high as H.P. + 5.9 m (5.0 m above sea level, H.P.: the reference surface for construction of Hitachi Port) to H.P. +6.3 m (5.4 m above sea level, provisional). Based on these findings, the height of the run-up tsunami was estimated to be approximately H.P. +6.3 m (5.4 m above sea level, provisional). The tsunami did not reach H.P. +8.9 m (8 m above sea level), on which the major buildings are located." (page III-53, bolding added by me)

"The tsunami flooded the north emergency seawater pump area in the seawater pump room, as shown in Figure III-3-8." (page III-54)

Mentioned Figure III-3-8 on page III-61.

The quote mentioning Japan Atomic Power Co. is obviously not about Fukushima II (or I) because they're operated by TEPCO, not JAPC. Instead the above description talks about the Tokai II NPP in Ibaraki prefecture.

 

[SteveElbows]

This worries me. The photos reveal interesting things.

1. It is interesting that the floor and ceiling of the room is not shown in the photos.
Are they already cracked? Is there danger of other cracks extending?
If not so, why then the support?

Various photos were posted towards the end of may in TEPCO's 'photos for press' area of their website (http://www.tepco.co.jp/en/news/110311/index-e.html). Some of them show the area in question.

For example this one shows the ceiling:

http://www.tepco.co.jp/en/news/110311/images/110529_09.jpg