Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[83729780]

tsunami wave receding from plant:

video:

 

[Borek]

They failed about thirty minutes after the Earthquake (and reactor Scram) because they no longer were there.

Could be I misread the information Astro posted here:

https://www.physicsforums.com/showpost.php?p=3185466&postcount=46

My impression was that the tsunami wave was first and they stopped some time later, but now I see it can be read differently - they started immediately and stopped when the wave came.

 

[Joe Neubarth]

The fact that they can get into the plants and grounds around them indicate that there are no spent fuel rods from the SFPs laying about.

Most of us are still trying to find out what is happening and what actually happened.

I am convinced that we had some fuel meltdown. I also know that the steam release to decrease pressure on the reactor carried considerable radiation release with it. That cesium and strontium and iodine came from at least one of the reactors.

Some on here seem to think that Reactor Number Three had a full melt down and loss of fuel material through the reactor vessel.

I keep on looking and can not find a reference to the pressure of Reactor Number three at the present time. Those of you in the know, can you post the present values if they have been released by Tokyo Electric?

 

[tadjik]

Could it be ... that :
http://www.nisa.meti.go.jp/english/files/en20110325-1-4.pdf

Supression chamber : 2 atm
Dry water : atmospheric
Temperature : relatively low
Radioactivity similar to other reactors

 

[turbo]

My impression was that the tsunami wave was first and they stopped some time later, but now I see it can be read differently - they started immediately and stopped when the wave came.

That is likely the case, Borek. Power turbines are large, but delicate and they trip on anomalous vibration, and likely the plant was set to scram its reactors on input from seismic sensors. Earthquake takes out the turbines and reactors, and the tsunami arrives later and takes out the emergency backup generators. Battery back-ups are limited and can't take the place of backup generators - maybe they have the capability of providing critical instrumentation and closing or opening critical valves to fail-safe conditions.

 

[Reno Deano]

Most of us are still trying to find out what is happening and what actually happened.

I am convinced that we had some fuel meltdown. I also know that the steam release to decrease pressure on the reactor carried considerable radiation release with it. That cesium and strontium and iodine came from at least one of the reactors.

Some on here seem to think that Reactor Number Three had a full melt down and loss of fuel material through the reactor vessel.

I keep on looking and can not find a reference to the pressure of Reactor Number three at the present time. Those of you in the know, can you post the present values if they have been released by Tokyo Electric?

If Cesium and Sr got out, where are the other long lived fission products? If am not wrong, there were no significant quantities of long lived fisson products reported to have beern blown by the steam into the environment around and offsite of the plant. Sure there is reactor core and SFP bundles damaged, but some what contained within their respective locales.

 

[Jakeh]

Battery back-ups are limited and can't take the place of backup generators - maybe they have the capability of providing critical instrumentation and closing or opening critical valves to fail-safe conditions.

No expert but as I understand it (from here or elsewhere) the battery power controls valves, the back-up system pumps themselves being powered by steam from the reactors. Which is pretty clever for as long as the valves can be controlled.

The amount of battery power available must be a possible lesson-learned thing. 8 hours wouldn't be acceptable for a mobile phone. That's probably very unfair. But also true.

First post here as well, I've been watching this unfold through here. Thanks to everybody, by far the best resource I've found on the web.

 

[Gilles]

Hi everybody

do you know the chemical properties of compounds and cesium and iodine ? iodine is very volatile, what about Cs and Sr compounds ? could it explain the fact that they could have been emitted together with water vapor , but not heavier elements ?
(1st post too - hello especially to other French people here - very interesting forum)

 

[jlduh]

About the generators, i think this info will have to be clarified by further inquiry but what i heard about was that they started (probably just after the quake) then stopped after. Looking at the vidéo above of the flooding of the plant we can understand that they have been flooded and probably destroyed as they were on the ground floor of the building, just close to the white fuel tanks as shown earlier on FRED's drawing.

We can be surprised that no mobile power generator could be available soon (I'm talking about these kind of things, like gas turbine generators: http://www.netimago.com/image_181981.html )

I heard an info at the beginning of the crisis that Tepco asked for ten of them... but found on the GE site that only three of them where available... in Florida! Ok i understand that total loss of power (including safety groups) was not a scenario conceived by Tepco and this perfectly demonstrates it...

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside? This looks an odd way of doing it, considering that there was a risk of explosion. Why inside instead of outside? This looks strange to me and i find no analysis or answer on this point.

 

[Joe Neubarth]

Could it be ... that :
http://www.nisa.meti.go.jp/english/files/en20110325-1-4.pdf

Supression chamber : 2 atm
Dry water : atmospheric
Temperature : relatively low
Radioactivity similar to other reactors

So why are the pressure readings negative? Those are negative signs I see in front, right?

 

[Gilles]

concerning the release of volatile cesium, I found that
http://blogs.nature.com/news/thegreatbeyond/2011/03/first_estimates_of_radioactive.html

The researchers estimate that 3x10^15 becquerels of Cs-137 (which has a half-life of 30 years) were released during the first two days following the disaster on 11 March. A further 3x10^16 was released over the next two days, totalling 50% of the Cs-137 emitted in the Chernobyl accident. 4x10^17 becquerels of I-131, with a half-life of 8 days, were likely released over the same period, roughly 20% of I-131 released from Chernobyl. Wotawa says he was "surprised at the cesium levels, but less so with respect to iodine, as its highly volatile."

with this comment

It would be nice if someone would give a better discussion of this result. By my understanding of the definition of a Bequerel, 3x10^16 Bq would amount to about 10 kilograms (!) of Cesium. That size of release seems completely impossible without a major containment failure, which pretty clearly has not occurred.

Posted by: Dean Townsley | March 24, 2011 03:32 AM

are 10 kg plausible ?

 

[tadjik]

Don't know why ...
The figures for the inside (I suppose) reactor are hardly understandable.
Below atmospheric pressure un all cases except reactor 1 (and negative for 2 3).

That's why I only read ther Dry well and Supression Chamber.
If anyone has a explanation (except instrumentation broken) ...

 

[Joe Neubarth]

About the generators, i think this info will have to be clarified by further inquiry but what i heard about was that they started (probably just after the quake) then stopped after. Looking at the vidéo above of the flooding of the plant we can understand that they have been flooded and probably destroyed as they were on the ground floor of the building, just close to the white fuel tanks as shown earlier on FRED's drawing.

We can be surprised that no mobile power generator could be available soon (I'm talking about these kind of things, like gas turbine generators: http://www.netimago.com/image_181981.html )

I heard an info at the beginning of the crisis that Tepco asked for ten of them... but found on the GE site that only three of them where available... in Florida! Ok i understand that total loss of power (including safety groups) was not a scenario conceived by Tepco and this perfectly demonstrates it...

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside? This looks an odd way of doing it, considering that there was a risk of explosion. Why inside instead of outside? This looks strange to me and i find no analysis or answer on this point.

My understanding is limited with respect to what they do, but I read somewhere that they vent steam from the primary inside of the building rather than to the open air. This supposedly is done to decrease the radiation released outside the building.

It looks to me that they did not know that they would be releasing hydrogen from the reactor plant. Hydrogen can come from breaking the bonds of the water molecule, and that could most likely happen in a scrammed reactor if the surface temperature of the fuel plates reached approximately 1000 degrees Fahrenheit. At some temperature in that range, the Zirconium cladding will oxidize with the Oxygen in the water molecule I thing the above is correct but will not be offended if corrected. I am not certain about the temperature needed for the Zirconium oxidation.

 

[Borek]

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside?

If I recall correctly venting inside of the building means lower chances of radioactive contaminants getting outside, hence the design.

Edit: beaten by Joe.

 

[jlduh]

Joe NEUBARTH: i asked several times here if we were talking about relative pressures or absolute pressures and got no answer. On the METI doc that you link, i think you'll find an answer if you go down a little bit, to the line "D/W design service pressure". You will read a first pressure number and then the second is defined as "abs" -absolute. So all the numbers you have in this report otherwise specified are relative pressure i think, which explain why it can be negative.

But, it means that on reactors 2 and 3, those pressures are below atmospheric pressure, which is kind of strange and... scary?

Again, it's very difficult to draw a conclusion based on some numbers but to me this could (i say could) mean that the 2 and 3 reactors are dead from their confinement standpoint... and that N°1 is still rising...

All three reactors had explosions, n°1 seemed to bit quite "clean" (outer walls). N°2 had an explosion that nobody saw, it has been said that it was in the suppression pool and that it was leaking. N°3 had 3 simultaneous big explosions (the most impressive) and some here expressed concerns about it's current state.

Concerning the explanation given of why venting in the building instead of outside: ok that's what i heard BUT would you do it deliberately a second time (N°3) after having experienced the first time an explosion in the building (where the pools are!) because of H2 presence? Notice that venting in a room that explodes ends up with everything in the atmosphere + a severe explosion... That's a strange thing.

 

[Reno Deano]

If I recall correctly venting inside of the building means lower chances of radioactive contaminants getting outside, hence the design.

Edit: beaten by Joe.

Venting to inside the Reactor Building is not the design. The offgas holdup system is the design, but would not be available due to loss of power and valves failing closed. They were in no win situation and vented to the upper part of the building (do not know if they could even control the discharge location), but failed to open the pressure equalization louveres (if they even could). Most new plants have 72 hours electrical backup and hydrogen igniters inside the primary containment to control hydrogen buildup. But then again with a long term station blackout, those may have not worked.

 

[jlduh]

Thanks Reno, so your explanation is that it's because there was no power available...

So the only vent they could open was inside the building, there was none actionnable toward the outside (what a pity...). Then that was a constraint, not a choice (like to avoid radioactive venting outside), right?

Are we talking about a valve that a man had to actionnate physically being close to it?

The reason why I'm asking these questions is that it seems that a modification has taken place in the US after the TMI accident under the NRC requirement, with the installation on all BWR reactors in the US of a so called "hardened vent" which is a direct realease to the atmophere to depressurize the containement. THis was to avoid precisely H2 release inside the building. Then the question is: did the japanese had this hardened vent? I have the impression that these vents are the big structures (like antennas) that we see close to every reactor (right or wrong?) but in this case it means that they still couldn't activate them because no power (seems not to "hardened" to me but...).

 

[Bodge]

The IAEA have just measured very high beta/gamma contamination 4,900,000 beq / metre squared in Fuk. Pref.

"At distances between 30 and 32 kilometers from the Fukushima Nuclear Power Plant, in a north westerly direction from the site, dose rates between 16 and 59 microsievert per hour were measured. At these locations, the results of beta-gamma contamination measurements ranged from 3.8 to 4.9 Megabecquerel per square metre. At a location of 21 km from the Fukushima site, where a dose rate of 115 microsieverts per hour was measured, the beta-gamma contamination level could not be determined."

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

Here is a map of Chernobyl's "Zone of Alienation"

I converted 40 curies / square km to 1.48 Megabeq / square metre

Also 1.48 is mentioned here:

http://books.google.com/books?id=g3...age&q=chernobyl cs soil contamination&f=false

We seem to have 4.9 Megabecquerels in Japan

edit: Forgot to mention not all of the radiation detected yesterday by the IAEA was from Cs137, there will be Iodine,Strontium,Cobalt etc and maybe Plutonium too. Also one site was "unmeasureable", but mSv was highest at that point !

 

[TCups]

Thanks Reno, so your explanation is that it's because there was no power available...

So the only vent they could open was inside the building, there was none actionnable toward the outside (what a pity...). Then that was a constraint, not a choice (like to avoid radioactive venting outside), right?

Are we talking about a valve that a man had to actionnate physically being close to it?

There was also speculation earlier that operators were reluctant to vent until absolutely necessary. That, combined w/ the technical info that the drywell cap could leak H₂ under a pressure as low as 2 ATM and w/ the additional technical info that the fuel transfer gate seal (between the upper drywall containment & SFP) is an electric pump-sustained pneumatic seal could explain one possible mechanism for H₂ accumulation in the drywell cap region, SFP, and upper building structures that may not have been apparent to operators reluctant to vent earlier, and at lower pressure. Search the earlier portions of this thread for more discussion of same.

 

[jlduh]

An other extract of the report of AIEA cited above (about hi beta gamma radiation in an area north west of Fukushima):

"Reactor pressure is increasing in Unit 1, pressure readings are unreliable in Unit 2, and stable in Unit 3 as water continues to be injected through their feed-water pipes. The temperature at the feed-water nozzle of the Reactor Pressure Vessel (RPV) is decreasing at Units 1 (243 °C) and 3 (about 185 °C), and stable at Unit 2 (about 102 °C).

Units 5 and 6 are still under cold shutdown, they are undergoing maintenance using off-site AC power and existing plant equipment.

Dose rates in the containment vessels and suppression chambers of Units 1 and 2 have decreased slightly."

So for them, the pressure readings -below 1 atmosphere- in reactor 2 and 3 that we talked about earlier would be unreliable... hummm, maybe.

 

[Bodge]

Hard facts are hard to come by I'm afraid.

 

[Joe Neubarth]

Hard facts are hard to come by I'm afraid.

Yep, I'm not certain I understand what I think I used to know, but I do know that I don't understand what is happening now.

 

[Joe Neubarth]

Yep, I'm not certain I understand what I think I used to know, but I do know that I don't understand what is happening now.

AND you can quote me on that, too.

 

[Bodge]

NHK WORLD:

"Caesium 141 found in plant."

Half life 24 seconds ? Please explain

 

[Bodge]

KYODO: as of 10 minutes ago.

"NEWS ADVISORY: Reactor vessel of Fukushima plant No. 3 unit may have been damaged: Gov't panel"
"NEWS ADVISORY: U.S. forces to provide water to cool Fukushima plant: Defense chief Kitazawa"

Where are all the resident experts?

I need answers to my last 3 posts, the situation is very concerning and still as clear as mud.

 

[JUrban]

> According to experts, salt from seawater pumped via fire hoses into reactor cores and spent fuel rod pools is depositing on fuel rods and nonoperational cooling systems, diminishing cooling, and that freshwater flushing and usage is critical.

> According to experts, delays (possibly weeks or months) expected due to observed cooling system damage and hazardous work environment.

> Surprisingly both US Marines and Army have Hose Reel Systems (HRS) at Okinawa bases, and should offer HRS to Japanese authorities (may prove invaluable).

> Each HRS has at least 5 miles of 6 inch diameter high capacity lay flat hose (Figure 1), which, along with accompanying mobile pumps, are presently at Okinawa bases.

> Multiple lakes within ~1.2 to 3 miles and beyond from nuclear plant (Figure 2) from which freshwater could be continually pumped using HRS (pump located lake side).

> Pumping is variable, reliable, high flow (~600 GPM), and high pressure (potentially aiding in high pressure water injection into reactor cores).

> HRS water delivery system can be tied into existing fire hose systems that are being used on site to both inject water into cores as well as water spent fuel pools.

> For contingency of extended time in which nuclear plant unapproachable due to excessive hazard levels, freshwater pumping (and likely borate injection) from safe distance miles away could continue, preventing continued situation deterioration.

> HRS maker LaBarge Inc., as well as former GE chief of safety research Richard Lahey, agree with use of HRS high flow freshwater delivery from lakes.

Comments, suggestions?

 

[Joe Neubarth]

KYODO: as of 10 minutes ago.

"NEWS ADVISORY: Reactor vessel of Fukushima plant No. 3 unit may have been damaged: Gov't panel"
"NEWS ADVISORY: U.S. forces to provide water to cool Fukushima plant: Defense chief Kitazawa"

Where are all the resident experts?

I need answers to my last 3 posts, the situation is very concerning and still as clear as mud.

Most of us are coming to the opinion that something worse than just venting on Reactor Three has happened. We still do not have enough evidence to convict.

 

[lou512]

No expert but as I understand it (from here or elsewhere) the battery power controls valves, the back-up system pumps themselves being powered by steam from the reactors. Which is pretty clever for as long as the valves can be controlled.

The amount of battery power available must be a possible lesson-learned thing. 8 hours wouldn't be acceptable for a mobile phone. That's probably very unfair. But also true.

First post here as well, I've been watching this unfold through here. Thanks to everybody, by far the best resource I've found on the web.

I agree thanks to all of you.

 

[Bodge]

The fresh water idea sounds essential and should have been actioned 10 days ago.

 

[BHamilton]

Steve Herman on twitter:

Yomiuri: TEPCO detected zirconium 95 at 0.23 Bq 330m south of Fukushima-1 drainage outlet on Wednesday.

looking for confirmation now

EDIT: found it, http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110324e6.pdf

 

[Joe Neubarth]

NHK WORLD:

"Caesium 141 found in plant."

Half life 24 seconds ? Please explain

That is as far as it could get before it died.

 

[Astronuc]

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside? This looks an odd way of doing it, considering that there was a risk of explosion. Why inside instead of outside? This looks strange to me and i find no analysis or answer on this point.

A colleague indicated it was apparently unintended for the hydrogen and steam from containment to be vented into the secondary or upper containment (metal structure). He indicated that duct work to carry to the appropriate stack had ruptured, and the hydrogen leaked into the upper containment area. As far as I know, one would not design a system to vent H₂ into the upper containment, precisely in order to prevent what did happen.

Salty seawater, which I expect has a fairly good soluble oxygen content, is problematic because it corrodes SS304. I imagine the intrusion produced a crud burst - crud being oxides of Fe, Cr, Ni, etc, and that could deposit on the fuel as it boils dry. Any crud on the fuel would be transportable in the seawater, which would explain the increase in Co-58,60 activity.

I'm curious about the behavior of UO₂ oxidation in seawater. I'm not aware of any studies.

 

[Astronuc]

NHK WORLD:

"Caesium 141 found in plant."

Half life 24 seconds ? Please explain

That doesn't make much sense to me. The half-life is very short, and that of Ba-141 and La-141 is much longer.

The precursor Xe-141 has an even shorter half-life, so there shouldn't be any significant accumulation of Cs-141 outside of containment.

 

[Bodge]

That doesn't make much sense to me. The half-life is very short, and that of Ba-141 and La-141 is much longer.

The precursor Xe-141 has an even shorter half-life, so there shouldn't be any significant accumulation of Cs-141 outside of containment.

I'm guessing this must have been a mistranslation. Cs-131 ?

 

[Astronuc]

I'm guessing this must have been a mistranslation. Cs-131 ?

I was wondering about that, but I'm not sure.

Here's the radionuclides around Cs-131, 133. Xe-131 is stable, so any Cs-131 should be a direct fission product.