Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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

 

[swl]

Wait, what ? Unit 5 is at atmospheric pressure, there was info that RPV was open to refueling but look what I found in report:

Dont understand this, so there was no water in reactor after earthquake ?
How they reduced RPV pressure ?

According to the quote you posted, there was water and fuel in the reactor during the quake. Water and fuel were in there for pressure testing of the RPV. The water and fuel may have been necessary to simulate the loading and mechanical stresses on the system during normal operation.

The system was then pressurized by what I assume was a gas. After the blackout, the pressurization system for the test stopped, so the rpv pressure began to drop (which might indicate that the system was in fact leaking, but it may have been leaking backwards through check valves back into the test equipment, or from any other path that may have existed either before or after the quake). After a time at a lower pressure, the decay heat of the fuel (that was not critical at the time of the quake) increased the pressure in the RPV. Which makes me wonder about the leak that existed after the quake; was it secured by the ever competent staff, or did the system continue leaking. Anyway, they then vented gas from the reactor and eventually succeed in controlling the pressure and water level.

If true, this makes me wonder. Did this reactor also suffer fuel damage? Maybe not, since it didn't explode. ;-)

 

[SteveElbows]

If true, this makes me wonder. Did this reactor also suffer fuel damage? Maybe not, since it didn't explode. ;-)

Well they made holes in the roof of the building, suggesting that they were keen to avoid an explosion there, and that in theory the risk of explosion existed.

 

[SteveElbows]

I see that according to latest plant parameters, they measured unit 4 fuel pool temperature at 19:52 on the 8th June and it was 86-88 degrees C.

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11060906_table_summary-e.pdf

 

[NUCENG]

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.

Prior to startup from a refueling outage, one of the normal tests is a hydrostatic pressure test. This is performed after the fuel has been reloaded, and the vessel has been reassembled and the head has been installed and torqued. The usual procedure is performed using recirculation pumps to heat up and pressurize the system to a proof pressure above the normal operating pressure, but below SRV setpoints. There is no air or nitrogen involved. The reactor remains shutdown with all control rods inserted. The containment is not inerted with nitrogen during this test.

 

[elektrownik]

Well they made holes in the roof of the building, suggesting that they were keen to avoid an explosion there, and that in theory the risk of explosion existed.

Unit 5 is at atmospheric pressure so the question is if they are venting it science earthquake ? I understand that is RPV is closed (it must be during pressure tests) the pressure shouldn't be at atmospheric level. Someone should look into raw data of unit 5&6, it could be find here: http://www.tepco.co.jp/nu/fukushima-np/index10-j.html
and here is translation of this page (but data arent in english): http://translate.google.pl/translat....co.jp/nu/fukushima-np/index10-j.html&act=url

 

[MiceAndMen]

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.

Very true, and I've thought about all that for the most part. To focus only on point 6, what are the statistics for industrial crane accidents? I'll bet the probability of an accident is less than the probability assigned by the designers of the plant to the possibility of a magnitude 9 earthquake and a 15m tsunami. And there are probably hard statistics to back that up, as opposed to just pulling it out of thin air and calling it my design basis.

Sorry for the snark :) Precautions would obviously be necessary. You don't paint without a dropcloth, cameras for observation underwater and above would be required, the vehicular transfer tanks would need the proper supports inside... all true. My opinion is it would still entail less risk than letting all that spent fuel stay 30 meters in the air for another year waiting for another earthquake. It all would depend on whose Probabilistic Risk Assessment numbers you believed. I sincerely do not believe such a plan would necessarily entail any more risk than they've already signed on for.

Thanks for the considered response, and again my apologies for the snark :)

 

[tsutsuji]

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...

The pillars were included in the FEM analysis presented in a press release on 28 May : http://www.tepco.co.jp/en/press/corp-com/release/11052801-e.html , and the result is that they improve the safety margin against earthquakes. The 3D model including the pillars is shown on figure 1 page 115 (attachment 4-4-1) of http://www.tepco.co.jp/cc/press/betu11_j/images/110528b.pdf

 

[mscharisma]

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.

It is in the report under this heading:
"(2) Seismic ground motion and tsunami height observed at Tokai Dai-ni NPS", so you are right. Sorry about that and thanks for pointing out my error. (Now I know why it instructs to not drive or operate heavy machinery on my latest prescription.) Deleted my post so as to not clutter up things here unnecessarily.

 

[NUCENG]

The articles in question are in Japanese, so quoting would be limited to Japanese text and asking someone to translate. We might ultimately end up with the whole article translated, which would completely be against the fair-use spirit of limited reproduction of copyrighted works. Then there is the matter of Japanese copyright law which I am totally unfamiliar with.

Being able to read the text would be nice, but my inability to read Japanese is my problem, not the author or publisher's. For the 2 articles in question, that's OK though because the diagrams and pictures convey substantial information by themselves.

I was using Google Translate to get some idea of the article text, but it's slow going. For example, first article, first section, title is which google translates as "For Example Oyster Or". I gave up soon thereafter.

Yes, my Japanese is also limited, and the technical terms are sometimes difficult to interpret. I have spent as much as four hours trying to read a single page. And Google translate has often been as bad as your example. It is a pretty intensive refresher, but won't really help the next time I visit a sushi restaurant.

 

[maddog1964]

Wait, what ? Unit 5 is at atmospheric pressure, there was info that RPV was open to refueling but look what I found in report:

Dont understand this, so there was no water in reactor after earthquake ?
How they reduced RPV pressure ?

could you please post your link for this information... as I believe that they may have been in the process of doing a "pressure test" and this is standard... required... and nothing scary!.. but without your source its very difficult to know what date and document your are looking at.

 

[SteveElbows]

Spraying of the creme-coloured agent onto one side of reactor 1 building shown on this timelapse video from the webcam:

http://www.youtube.com/watch?v=bPl1RKh548Y&feature=channel_video_title

Also the video of the hour prior to that shows multiple humans in the foreground near the camera at some points.

 

[NUCENG]

I see no data in support of that. No reduction of containment pressure was observed between the time PCV spraying is said to have been initiated (7:39 on March 13th ), and the time of the announcement that PCV spraying had been canceled (9:00 on March 13th).

That may be true. I was trying to explain that Containment Spray is a separate function from Core Spray. The question was what were they talking about when they said "spraying the PCV.

 

[NUCENG]

Thank you for the explanation.
Would these emissions be a plausible explanation for the cesium contamination in the sea water pooled in the basement?
I'm having a difficult time quantifying the scale of that problem, as contamination 30x the standard for release no longer sounds very threatening. Is this in line with some fuel rod breach or some steam leak from the turbines or what?

Probably not. Offgas extraction of steam would have ended at the time of the earthquake and scram and MSIV closure. The fans thyat exhaust steam to the offgas stack would have lost power as well. Fuel damage would not have begun until the station blackout occurred for units 2 and 3. Unit 1 may have lost decay heat removal before that if operators isolated the Isolation Condenser,

I would expect that the initial releases of cesium probably coincided with containment leakage from unit one due to rising containment pressure or containment venting. Unit 2 and 3 wouldn't have experienced significant fission product releases until HPCI and RCIC systems failed or batteries were depleted.

 

[NUCENG]

A sudden drop in pressure maybe. Such as when there's a fuel-air explosion above the pool. The high-pressure wave is "followed" by a very low pressure front which is relatively long in duration.

This has been mentioned before, but not by me. Apologies to whoever it was, I can't find that post :(.

We can verify this, by the way. Was there a drop in #3 SFP level post-blast? I still think it's low-probability, btw.

If you postulate a fuel air explosion, why do you need a steam explosion too?

 

[tsutsuji]

I had left the Onagawa nuclear power plant's happy-ending story with Pr. Omoto's 3 May 2011 presentation :

Site ground level → saved Onagawa units

page 9 https://www.sfen.fr/content/download/30655/1616957/file/1-ICAPP_Omoto2.pdf

This is not wrong, but we now know that it was a bit more complicated than that :

The observed tsunami height was 13 m, and despite the land sinking, the tsunami did not
cause the seawater pump room (on the site as high as 13.8 m, adjusted to sinking by
about 1 m) to be directly submerged. However, as the water level rose due to the tsunami,
the water level in the underground intake pit also rose as shown in Figure III-3-5, caused
by the siphon phenomenon. This resulted in seawater overflowing through the opening of
the tide gauge into the seawater pump room. Then the seawater flowed from the pump
room, via the trench, into the basement floors of the reactor buildings, causing the heat
exchanger room of the component cooling water system in the second basement to be
submerged. In addition, the component cooling water pump of Unit 2 was also
submerged, which thereby caused the cooling function of emergency diesel generators to
be lost, with two units stopped out of those three generators.

page III-50 (page 4 of http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iii-3.pdf)

 

[zapperzero]

If you postulate a fuel air explosion, why do you need a steam explosion too?

I don't need it, really. Others do, because it's really hard to for most people to believe that a "mere" hydrogen blast would lift so much stuff so high into the air and twist steel beams and scour paint off them and break steel-reinforced concrete pillars.

To most, I think, a fuel-air detonation is what happens when you get your fuel mix wrong and your engine starts "pinging". Annoying and possibly expensive, but not so dangerous, overall.

It's hard to make the jump from that to "flour mill wiped clean off the face of the earth" or "elevator cab blown literally a mile away in coal-dust mine blast" or "apartment building in Grozny demolished with one Shmel rocket".

 

[MadderDoc]

I am left wondering how it could possibly have been determined, that a fire was ongoing -- concurrent with the explosion -- in the oil of the recirculation flow control system M/G sets.

If they eyeballed a fire at that location once the initial dust from the explosion died down, they may reach that conclusion.

However, that would be a non sequitur, would it not :-)

Anyhow -- on a photo of the location once the initial dust from the explosion had died down there appears to be not one iota more of a lubricant fire to eyeball in the NW corner if unit 3, than there is on a photo taken 3 days later.

Here's the location 3 minutes after the explosion:

and here, the location 3 days after the explosion:

 

[Quim]

it's really hard to for most people to believe that a "mere" hydrogen blast would lift so much stuff so high into the air and twist steel beams and scour paint off them and break steel-reinforced concrete pillars.

I am one of the people who don't believe that a hydrogen explosion could have caused the vertical blast we see in the unit 3 explosion, but it is not because I don't believe a hydrogen explosion would be limited in power. To my eyes, the explosion, or the second part of the explosion of unit three, was a vectored blast.

I don't see the "mushroom cloud" as being merely a case of heat rising and carrying with it contaminates from a blast (as is the case in a surface burst nuclear explosion.) I see the vertical cloud as being the actual product of the blast itself. Imagine if you took all the shot out of a shotgun shell, replaced it with a dark powder of some sort and fired it into the air - that effect is what I see in the unit three blast,

I apologize if this explanation sounds too elementary or condescending but there are obviously some here who don't understand the significance of a vectored vertical blast - some force or some structure was responsible for containing the explosive force to a single direction.

The reactor containment structure can be ruled out as the vectoring agent simply because the equipment crane is lying on top of the containment structure with the remnants of the roof laying on top of that. These would not be so if the vertical blast had originated from the RPV or its containment,

The unit three explosion has to be seen as a two part event, a hydrogen blast (which did in fact break steel-reinforced concrete pillars) and a vectored vertical blast.

To jumble these two events and see them both as a single "explosion" would be to ignore the visual evidence.

 

[tsutsuji]

The approved storing capacity and water level at the process main building has been further extended :

maximum capacity : 14,200 m³ (up from previous 11,500 m³)
maximum level : OP + 5100 mm (this is 1.4 m above the 1st basement floor) (up from previous OP + 4200 mm)

However lowering that level back to the 1st basement floor level will be the top priority once the water purifying unit starts running.

http://www.meti.go.jp/press/2011/06/20110608003/20110608003.html

measured level : OP + 4507 mm as of 7AM 8 June 2011 : http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110608_01-j.pdf

 

[zapperzero]

some force or some structure was responsible for containing the explosive force to a single direction.

Ok. Something guided that plume upwards. It's going up faster than just heat would push it. There are big chunks in there that couldn't float up in a warm breeze regardless. So far, we are in agreement.

But how does all that make it necessary for a second explosion to have happened? There's any number of structures in there that could have shaped the hydrogen blast.