Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[artax]

some interesting stuff here

http://online.wsj.com/article/SB10001424052748704281504576329011846064194.html

I'd hope they release these documents and I'd like to see the whiteboard scribblings from the time prior to the explosions!

The continuing conflicting reports about the situation are a nightmare,... I was talking to a colleague last week who said everything's OK there now. Just depends which paper you read!

 

[clancy688]

Also, of interest, i put this article on "passive cooling" (no external power required to cool the reactor).

http://motherjones.com/blue-marble/...chnology-safer-not-always-japans-crisis-shows

BWR3 reactors are of this type, and number 1 unit is a BWR3 (that's why it has a different cooling principle than the others, that we just learned Tepco workers have possibly volountarily turned off after Tsunami and shutdown, in a procedure to "protect" the reactor).

The article is a joke, IMHO. If I understand it correctly, it's telling that the passive safety systems of the BWR/3 is better than later, energy driven safety systems. That's ridiculous.
First, we can perfectly see what happens if an Isolation Condenser is used to cool a nuclear reactor - total meltdown within 16 hours. It was switched off, but switched on again three hours after the earthquake.

And second, the Isolation Condenser is not even designated to provide emergency cooling for extended time periods. In a pdf regarding safety issues of the BWR/Mark-I design it's stated that the IC pool will be boiled dry within 1,5 hours! (Which would allegedly leave enough time to secure other means of cooling - ha, my ***...)

Moreover, the emergency cooling systems of Unit 2 und 3 (RCIC) worked much longer than the IC - for up to three days in case of Unit 2.

 

[~kujala~]

http://www.tepco.co.jp/en/challenge/energy/nuclear/plants-e.html

the plants are built on solid bedrock

I think I found out why they are using this term.

Here is how Merriam-Webster defines "bedrock":
http://www.merriam-webster.com/dictionary/bedrock

the solid rock underlying unconsolidated surface materials

Here is how Wikipedia defines it:

In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil.

http://en.wikipedia.org/wiki/Bedrock

The main thing is "unconsolidated". Mudstone happens to be a special form of shale/clay/mud that has accumulated during million years in the sediment layer of the ground and is considered to be "consolidated":

When consolidated and relatively massive it is known as mudstone (or claystone)...

http://www3.hf.uio.no/sarc/iakh/lithic/mudstone.html

Below "mudstone" is a harder/older layer of consolidated rock but still "mudstone" is thought to be part of "bedrock" when we use the word "bedrock" in its general meaning. If we want to divide between these two some special words has to be used. Like they use words "Mesozoic bedrock" and "Franciscan bedrock" in this page:
http://earthquake.usgs.gov/regional/nca/soiltype/
(I am using the word "harder bedrock" here.)

So when TEPCO says they have built Fukushima plants on solid bedrock they are not lying. Still I feel little bit cheated as the qualities of mudstone and harder bedrock probably differ a lot as seen from the earthquake stand of point. Again referring to previous page:
Vs > 1500 m/sec Includes unweathered intrusive igneous rock.
1500 m/sec > Vs > 750 m/sec Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock.
750 m/sec > Vs > 350 m/sec Includes different kind of sand, sandstones, mudstones and limestones.

Note 1: I am quite sure TEPCO has made some research concerning the qualities of harder bedrock (-46 meters from the current ground level) and mudstone and it would be very interesting to get the results from this research.
Note 2: They removed a 25 meter layer level of soft sand to get to the mudstone layer. Would it have been possible to remove a 46 meter layer of mudstone to get to the harder bedrock layer? But if they had done that the whole plant would have been below sea level which I guess would have been impossible.

 

[zapperzero]

I was talking to a colleague last week who said everything's OK there now.

Your colleague has an interesting idea of what OK is.

 

[MadderDoc]

<..>
5) On one of the T-Hawk videos it can be seen that the service floor is broken only under the north crane boom.

Rive, sorry to be so late in catching up with this. I think quite on the contrary of what you say, in one of the T-Hawk videos the drone hovers close to the west end of the south crane boom, and it is readily apparent that the service floor in this position is also not intact (seeing that the floor has sunk under the boom.)
This is from the THawk video no3 from April 15th.

 

[~kujala~]

I see two possibilities. The first possibility is that the Centralized Waste Treatment Facility was designed some years ago for a given capacity of liquid waste. Storing larger quantities of highly contaminated water there straight away would have somehow meant breaking the rules. So they had to enhance their water leaking countermeasures, like having some more pumps and empty tanks ready in case a leak would occur, and ask NISA for approval. An other possibility is that the building was not designed at all to store liquids, but they made it watertight so that they can flood it with the contaminated water.

Whether A or B I still see problems here. The thing is building watertight systems is not easy and if you do it "fast" you might fail. These things need time and good design to succeed and if you have to improvise it you never know what's the end result going to be.

On the other hand, I assume they simply don't have enough space so they have no other choice as to do it on the fly.

 

[tsutsuji]

some interesting stuff here

http://online.wsj.com/article/SB10001424052748704281504576329011846064194.html

I'd hope they release these documents and I'd like to see the whiteboard scribblings from the time prior to the explosions!

The continuing conflicting reports about the situation are a nightmare,... I was talking to a colleague last week who said everything's OK there now. Just depends which paper you read!

The documents are here : http://www.tepco.co.jp/nu/fukushima-np/index10-j.html (in Japanese). For example you can see some of the snapshots of whiteboards mentioned by the Wall Street Journal from page 17/55 of http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_4_Nisshi1_2.pdf

 

[jlduh]

The non-hardened vent system is the Standby Gas Treatment System. In an emergency it takes a suction on the secondary containment and discharges to the stack through particulate HEPA filters and activated charcoal filters to remove radiation from the vented air. The system maintains secondary containment at a small negative pressure so any leakage of the building is from the atmosphere to the building. Later in an accident the system can be used to take a suction on containment to clean up radiation inside a depressurized containment. Again it would discharge through the filters to minimize the release.

The whole purpose of the hardened vent is to allow a high pressure vent path from the torus air space to save containment integrity. The only motive force is containment pressure. The drywell will releve through the downcomers to the torus water pool which will also hold up soluble contaminants. As torus pressure drops whole containment is being vented.

Ok thanks NUCENG this is much clearer now.

So in fact hardened vent is not so hardened as it has to be operated in a reliable manner (which is the main problem!) very early in a severe accident case, otherwise it's not enough hardened to bear the high pressures.

Do we have data (in the US) about the values of max pressures allowable we are talking about for an" hardened vent" system?

Lookin at the speed at which H2 fills the much too small Mark I containment, yes this has to be VERY quick...

Now, the point that are unclear concerning the venting at Unit 1 during the 3 additional hours after Kan visit are:

- was it because the workers couldn't open the valves?
- was it because Tepco management had some fears of opening them (would be very interesting to know the content of the discussions during the 3 hours)?
- did it finally explode because they finally vented but the pressure was already too high and the tightness of Mark I containment already failed, with H2 entering the top floors (probably first at containment cover seal which was considered to be a weak point, based on data discussed here on the forum)?
- did it finally explode because they vented but the venting (supposedly hardened) failed because of too high pressure and the leak path of H2 entered the building and the top floors before exploding?

These question are currently unresolved IMHO.

 

[jlduh]

The article is a joke, IMHO. If I understand it correctly, it's telling that the passive safety systems of the BWR/3 is better than later, energy driven safety systems. That's ridiculous.
First, we can perfectly see what happens if an Isolation Condenser is used to cool a nuclear reactor - total meltdown within 16 hours. It was switched off, but switched on again three hours after the earthquake.

And second, the Isolation Condenser is not even designated to provide emergency cooling for extended time periods. In a pdf regarding safety issues of the BWR/Mark-I design it's stated that the IC pool will be boiled dry within 1,5 hours! (Which would allegedly leave enough time to secure other means of cooling - ha, my ***...)

Moreover, the emergency cooling systems of Unit 2 und 3 (RCIC) worked much longer than the IC - for up to three days in case of Unit 2.

You are right of course, but the main idea of this article is to say that passive cooling is maybe a more reliable system than active ones (meaning the necessity of AC or DC power). Personally i have no idea of the problems associated with that principle which seems on the paper interesting. But what the paper says is that the newst generations of reactors seem to re-include that kind of systems. Again I have no idea if it is "marketing oriented stuff" (passive cooling seems great!) or if there is real improvement, and the article qustions this also by the way.

That's how I understand the spirit of this article.

 

[artax]

a bit of an update on allthingsnuclear from yesterady.

http://allthingsnuclear.org/

 

[jlduh]

http://www.tepco.co.jp/en/challenge/energy/nuclear/plants-e.htmlI think I found out why they are using this term.

Here is how Merriam-Webster defines "bedrock":
http://www.merriam-webster.com/dictionary/bedrockHere is how Wikipedia defines it:

http://en.wikipedia.org/wiki/Bedrock

The main thing is "unconsolidated". Mudstone happens to be a special form of shale/clay/mud that has accumulated during million years in the sediment layer of the ground and is considered to be "consolidated":

http://www3.hf.uio.no/sarc/iakh/lithic/mudstone.html

Below "mudstone" is a harder/older layer of consolidated rock but still "mudstone" is thought to be part of "bedrock" when we use the word "bedrock" in its general meaning. If we want to divide between these two some special words has to be used. Like they use words "Mesozoic bedrock" and "Franciscan bedrock" in this page:
http://earthquake.usgs.gov/regional/nca/soiltype/
(I am using the word "harder bedrock" here.)

So when TEPCO says they have built Fukushima plants on solid bedrock they are not lying. Still I feel little bit cheated as the qualities of mudstone and harder bedrock probably differ a lot as seen from the earthquake stand of point. Again referring to previous page:
Vs > 1500 m/sec Includes unweathered intrusive igneous rock.
1500 m/sec > Vs > 750 m/sec Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock.
750 m/sec > Vs > 350 m/sec Includes different kind of sand, sandstones, mudstones and limestones.

Note 1: I am quite sure TEPCO has made some research concerning the qualities of harder bedrock (-46 meters from the current ground level) and mudstone and it would be very interesting to get the results for this research.
Note 2: They removed a 25 meter layer level of soft sand to get to the mudstone layer. Would it have been possible to remove a 46 meter layer of mudstone to get to the harder bedrock layer? But if they had done that the whole plant would have been below sea level which I guess would have been impossible.

Ok i admit the definition of bedrock can be discussed and your infos are very interesting.

But as you, "I feel little bit cheated as the qualities of mudstone and harder bedrock probably differ a lot as seen from the earthquake stand of point". I feel also a little bit cheated with their illustrations i posted yesterday in their safety section.

By the way they also did some tests of liquefaction of soil during this survey, this could also be interesting. Anyway this is i think a secondary problem based on the current accidents.

 

[SteveElbows]

Have we noted that drywell CAMS data for reactor 1 started to be published again? I noticed it on japanese version of data today, but if I look at yesterdays data in English it seems to have appeared one data release earlier there...

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

One of the sensors is reading 218 Sv/h in that data!

 

[NUCENG]

Does anyone here now what the pressure relief or steam relief valves are set for on one of these BWRs? Maybe running them above double design pressure is risky.

Also, did they actually ever successfully vent any of the 3 reactors or did they all blow a gasket, or rupture disk?

Are you confusing the fardened wetwell vent with the SRVs? The Safety Relief Valves vent the RPV to the torus. The pressure that was double its limit was containment pressure.

SRVs have automatic setpoints, mechanical setpoints, depressurization timers and are operated manually in accordance with Emergency Operating procedures. The mechanical setpoints are designed with sufficient capacity that the vessel should never exceed its design limit.

 

[jlduh]

Have we noted that drywell CAMS data for reactor 1 started to be published again? I noticed it on japanese version of data today, but if I look at yesterdays data in English it seems to have appeared one data release earlier there...

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

One of the sensors is reading 218 Sv/h in that data!

As I keep seeing very variable and it seems inconsistent CAMS numbers from the very beginning, do some specialists here have an idea of what could be considered as the maximum thinkable radiation reading in mSv/h? Let say close to a corium mass, which number could we imagine? I guess there must be some data from testing and or historical recordings?

This would enable us to clarify is it is useful data or just jaggies from unreliable equipement.

 

[gbettanini]

I found a presentation that describes the accident’s phases and the venting processes.
http://www.scribd.com/doc/52131245/fukushima-areva

This scaring phrase in the NYT article:
“the pressure inside Reactor No.1 had reached roughly twice the maximum pressure the unit had been designed to withstand, raising fears that the vessels that house fuel rods would rupture, setting a possible meltdown in motion.”
… seems to be not true, the RPV can withstand a pressure of over 8 MPa, the primary containment can withstand a pressure of around 0.8 MPa, so the wet-well could have ruptured well before the RPV (as in reactor n.2… maybe).
So the question is if TEPCO could have been able to vent hydrogen and radionuclides through the stack before the explosions… but is seems to me a question of secondary importance, the amount radionuclides released would have been quite the same, maybe monitoring the wind direction the releases could have been diluted and directed to the sea but the total amount of PBq released must have been quite the same.
So this second sentence of the NYT article seems to be not true:
“venting would have allowed some radioactive materials to escape, analysts say that those releases would have been far smaller than those that followed the explosions at three of the plant’s reactors”

 

[SteveElbows]

As I keep seeing very variable and it seems inconsistent CAMS numbers from the very beginning, do some specialists here have an idea of what could be considered as the maximum thinkable radiation reading in mSv/h? Let say close to a corium mass, which number could we imagine? I guess there must be some data from testing and or historical recordings?

This would enable us to clarify is it is useful data or just jaggies from unreliable equipement.

Yeah I try not to take the CAMS readings too seriously because of unknown quality of data, but still can't help observing them anyway.

Meanwhile I think I just saw the NHK world news ticker say that workers who entered reactor 2 building today had to leave after 14 minutes due to steam.

 

[swl]

Are you confusing the fardened wetwell vent with the SRVs? The Safety Relief Valves vent the RPV to the torus. The pressure that was double its limit was containment pressure.

Yes, I was confused. Thank you for that.

So now another question: Does the containment system have an automatic pressure relief valve to vent the system through piping rather than the first point of failure? If so, why did the pressure rise to double the design limit? If there is no automatic pressure relief valve for the containment, why not?

I imagine a controlled relief of contaminated steam would almost always be preferable to an uncontrolled and irreversible containment failure.

 

[tsutsuji]

You can see the data in table form, where it is easy to read the exact values around March 21st.

However there is a problem. Yesterday Tepcos links to modern graphs, tables of data, and csv files did not just contain very recent data like they normally do, they were much larger and contained data going all the way back to before the 20th march. But today the same links have returned to their normal state, just showing data from recent days in may. So I cannot give you links to this information, maybe someone can reupload the data or find different urls?

I have looked at http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf and found those 3 data (A系　原子炉圧力) (system A reactor pressure) :

2011/03/21 1:25 ... 8.968 MPa
2011/03/21 1:45 ...11.571 MPa
2011/03/21 2:30 ...10.774 MPa

Here is my post where I talked to someone about this new data yesterday, but as I said the links in it don't give the info I was talking about anymore :(

https://www.physicsforums.com/showpost.php?p=3305309&postcount=7502

In recent messages here I have been disagreeing with someone else about whether the smoke events of 21st march may be responsible for the increased radiation detected far away just a few hours later. I was blaming the weather. Well, I do not mean to sound so certain about this at all.

At first I was blaming the rain for most of the radioactivity in Kanto region after March 16th. But I had to revise my position after the discussion started at : https://www.physicsforums.com/showthread.php?p=3257862#post3257862

Its only that I do not want to rule the weather out completely, because I checked messages I posted at a different forum around 19th-20th march to remind myself what was being said then. Stories were already appearing in the press about food and water contamination by the 19th march.

Water or food problems are a complex result of a number of events that happened earlier at the plant. I agree that the later events, if responsible for anything, may be responsible for only one part of the problems.

I am also trying to check the wind direction to see if the peak at 6 AM on March 21st in Mito (1) is correlated with a sudden change of wind direction, but the data at http://www.data.jma.go.jp/obd/stats...CB&year=2011&month=3&day=21&elm=minutes&view= seem to say that the wind had been nearly steady with an East-North-East direction from 5 AM to 7 AM, without showing anything special at 6 AM in correlation with the peak. But we would need a thorough meteorological study to know exactly about atmospheric transport on that day.

(1) already mentioned attachment at https://www.physicsforums.com/showthread.php?p=3258585#post3258585

 

[ottomane]

Although it is off topic in relation to the current discussion I'd like to post another question:

The (control?) rods usually contain Boron to catch neutrons. Each Boron-nucleus can only catch one neutron once, so Boron is getting used up. So the rods have to be exchanged after some years.

If the fuel rods and control rods melt together into one mass, this changes the geometry and heat conditions in the reaction. Also water would be gone, so there is no moderator.

Does this setup affect the Boron consumption?

 

[ihatelies]

So I'm back from a mini vacation, and I see that TEPCO has finally admitted that the fuel has breached the RPV in unit 1 and probably the same in units 2 and 3.

I assume this has come as no surprise to anyone following the event, however it does negate much of the "data" that has been provided around RPV pressure, temperature and water level over the rods - which apparently no longer exist (as rods at least).

So I come back to my theory that some portion of the RPV#3 actually ejected during the explosion on March 14th. If you'll recall, many here said that I could not possibly be correct, because the temp and pressure data proves that the RPV is still intact.

However, now that we know the temp and pressure data is likely incorrect, that argument against my theory is dead.

I will remind everyone again, of the hole in the roof shown in this picture:

And I will provide Fred's excellent analysis of the roof structure and hole here. His conclusion as I recall was that it did appear that something went through the hole, but it must have fallen down rather than up. I'm not sure I agree with that view, but i will say I cannot refute it.
[PLAIN]http://k.min.us/jntf3c.jpg

My question is this. Can anyone factually rule out that all or part of the reactor did not eject in the explosion on March 13th, and if it did what are the consequences globally of the fallout?

 

[NUCENG]

Yes, I was confused. Thank you for that.

So now another question: Does the containment system have an automatic pressure relief valve to vent the system through piping rather than the first point of failure? If so, why did the pressure rise to double the design limit? If there is no automatic pressure relief valve for the containment, why not?

I imagine a controlled relief of contaminated steam would almost always be preferable to an uncontrolled and irreversible containment failure.

Containment does not have any automatic venting provision. Thus it requires conscious operator action to vent containment, because in an accident the venting is releasing radioactivity to the environment and exposing the public. One of the reasons that installation of hardened vents was contoversial was that there was no design basis accident that ever required containment venting (hardened or otherwise) until the cleanup phase. In the end it was agreed to install the capability in all US Mk1 containments even though its only use would be for a severe accident (beyond the design basis).

I don't know if hydrogen explosions would have been prevented had Fukushima operators vented before exceeding the containment design pressure, but it couldn't have made it any worse. The loss of decay heat removal and fuel pool cooling would still have caused fuel damage, but maybe the roofs would still be in place.

 

[jlduh]

Containment does not have any automatic venting provision. Thus it requires conscious operator action to vent containment, because in an accident the venting is releasing radioactivity to the environment and exposing the public. One of the reasons that installation of hardened vents was contoversial was that there was no design basis accident that ever required containment venting (hardened or otherwise) until the cleanup phase. In the end it was agreed to install the capability in all US Mk1 containments even though its only use would be for a severe accident (beyond the design basis).

I don't know if hydrogen explosions would have been prevented had Fukushima operators vented before exceeding the containment design pressure, but it couldn't have made it any worse. The loss of decay heat removal and fuel pool cooling would still have caused fuel damage, but maybe the roofs would still be in place.

I think that it's oversimplified to say the roofs would still have been there, many other things would have been there i think... (of course I'm talking about the other reactors than just N°1).

Heavy damages to the structures and all the equipements around have considerably increased the difficulties for workers around to restore or contain the situation...

This venting mess (with all the problems that occurred on the vent system) is a good part of the current situation IMO. Not the initial cause of course.

 

[swl]

NHK TV News on 18May @ 21:00 JST:

Unit 2 has 99% humidity inside. It is thought that the humidity is coming from the spent fuel pool. TEPCO is planning to move up it's plan to improve cooling of the spent fuel pool. Four workers entered unit 2 today for 15 minutes. There efforts to inspect the facility were complicated by the high humidity. The highest radiation reading noted within unit 2 was 50 mSv/h. They also reiterated that TEPCO feels the torus was damaged in unit 2 by an explosion and that the unit has been leaking highly radioactive water since the explosion.

 

[zapperzero]

My question is this. Can anyone factually rule out that all or part of the reactor did not eject in the explosion on March 13th, and if it did what are the consequences globally of the fallout?

Let me rephrase first for clarity.

"1. Can anyone rule out the possibility that part of the core (by which I mean fuel rods, heavy metals such as uranium and plutonium) was ejected in the March 13th event?
2. If so, what parts of the world could be affected by fallout, and how?"

Now, on to the answers.

To your question 1: No. You should not, however, take this as an endorsement of your theory. It's simply that the matter is undecided. Multiple pieces of evidence (such as the evident absence of people dropping like flies on the plant grounds minutes after and continued work at the site) strongly suggest that it is, in fact, incorrect. Pictures from inside the reactor and chemical testing of the plant grounds and environs should settle the question.

To your question 2: What can be said with relative certainty is that the plume was nowhere near high enough to inject particulates (such as fine uranium and plutonium oxide dust) into the high-altitude currents. Such fallout would have been, thus, local and remain localized. Initial deposition would depend solely on local weather patterns on the day and in the subsequent week or so.

 

[ihatelies]

Let me rephrase first for clarity.

"1. Can anyone rule out the possibility that part of the core (by which I mean fuel rods, heavy metals such as uranium and plutonium) was ejected in the March 13th event?
2. If so, what parts of the world could be affected by fallout, and how?"

Now, on to the answers.

To your question 1: No. You should not, however, take this as an endorsement of your theory. It's simply that the matter is undecided. Multiple pieces of evidence (such as the evident absence of people dropping like flies on the plant grounds minutes after and continued work at the site) strongly suggest that it is, in fact, incorrect. Pictures from inside the reactor and chemical testing of the plant grounds and environs should settle the question.

To your question 2: What can be said with relative certainty is that the plume was nowhere near high enough to inject particulates (such as fine uranium and plutonium oxide dust) into the high-altitude currents. Such fallout would have been, thus, local and remain localized. Initial deposition would depend solely on local weather patterns on the day and in the subsequent week or so.

OK thanks for the response. Your rephrasing my question is not exactly what I meant.

I meant - did the plug, the containment cap, the nuclear fuel or the entire RPV eject in the explosion.

However, your rephrasing is the worst case scenario. Let's compare your answer to the evidence:

Answer 1: You say people didn't drop like flies immediately following the explosion, however I do recall that some employees did in fact die in that explosion and several more were seriously injured. I seem to recall 2-6 dead and 11 injured. I have not heard any updates on those early reports. Just a few days later, a couple of employees were "lost" and assumed dead as they were out reading radiation data. I think they were later found in or around the turbine buildings dead.

You also say work has continued on site. It did not immediately. They evacuated, and later information indicated that evacuation was prompted by a 12x increase in radiation in the control room.


On your answer 2: I certainly hope you are correct, but I've seen fully mixed opinions on this. I don't doubt that the initial smoke plume wasn't high enough to reach the jetstream, however that doesn't mean in any way the dust from that explosion couldn't have. Do you have data to support that these particles couldn't have circulated far from the plant? or is that your opinion.

What we do know is that shortly after the explosion, the USS Ronald Reagan encountered a "radioactive cloud" and a nuclear emergency was declared on the vessel, and they changed course. Early reports were that a helicopter and crew were exposed to slight radiation and they took showers and washed the helicopters down and all was well. Later reports detailed that the radiation monitors on the ship went ballistic, the ship went on nuclear emergency for three days, the air and water supply on the ship were contaminated, and they had near panic onboard.

Certainly the Reagan and her crew had the equipment and knowledgeable personel to determine exactly what the substances in that cloud were. I've not seen any data.

 

[ottomane]

IMO there are two alternative explanations for the vertical smoke plume and the energy released in the explosion:

1) The SFP went critical / exploded H2

2) Same with the RPV

Both of them are a mess and release huge amounts of radioactive particles. So, basically it does not matter if 1) or 2) happened.

 

[Rive]

IMO there are two alternative explanations for the vertical smoke plume and the energy released in the explosion:

1) The SFP went critical / exploded H2

2) Same with the RPV

Both of them are a mess and release huge amounts of radioactive particles. So, basically it does not matter if 1) or 2) happened.

Well, based on the missing heavy contamination of radioactive fuel particles and pieces all around the site there are two conclusions:
- none of those alternatives happened
- there must be other alternatives.

 

[ottomane]

Well, based on the missing heavy contamination of radioactive fuel particles and pieces all around the site there are two conclusions:
- none of those alternatives happened
- there must be other alternatives.

Not all fuel must have been ejected. And yes, in the days after the explosion they had to "bulldoze over" an area on the site because of some extreme radioactive material. And they found (at least) one piece of fuel 2 km away from the site.

What is your explanation for this?

 

[ihatelies]

IMO there are two alternative explanations for the vertical smoke plume and the energy released in the explosion:

1) The SFP went critical / exploded H2

2) Same with the RPV

Both of them are a mess and release huge amounts of radioactive particles. So, basically it does not matter if 1) or 2) happened.

This would be true if they contained exactly the same materials. As far as I've been able to understand they did not. Spent fuel contains some small percentage of plutonium molecules that have resulted from the fission process in the reactor. They are embedded in the fuel.

The reactor core of 3 contained the newly loaded MOX fuel, which as far as I know is made from finely ground (nanometer lever ground - finer than household dust) plutonium and uranium powders that are mixed and "sintered". What is unclear is whether the sintering process binds these materials permanently or are they simply pressed together and in the midst of an explosion they will return to the powder form. It's also unclear if the operating heat of 6 months in the reactor would bind them (I tend to think it would)

Certainly if a nanometer ground powder of even a heavy metal like plutonium were released it would be serious.

Of course if the spent fuel pools of either #3 or #4 contained new unused MOX rods, then I would think those are even more dangerous than the rods in the core, because I suspect the sintering process in manufacture does not tightly bind the powder.

 

[Rive]

Not all fuel must have been ejected. And yes, in the days after the explosion they had to "bulldoze over" an area on the site because of some extreme radioactive material. And they found (at least) one piece of fuel 2 km away from the site.

What is your explanation for this?

https://www.physicsforums.com/showpost.php?p=3304969&postcount=7484", and some earlier posts of that thread.