Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[elektrownik]

I don't think that fuel was ejected from SFPs. It would give very hight radiation, not 300 or 900mSv, and for example, if there is ~1500 fuel racks in #4 sfp, (or #3) then for example if only 10% fuel would be ejected it would give us 150 fuel racks so they would be everywhere, we could see them on thermal images and also radiation from them would kill workers very fast.

 

[bytepirate]

About the picture of blue flash: fresh spent fuel is glowing even without recriticality, so without further observations it proves nothing. Is the glowing still visible? Has it happened any more times? Any similar observations from satellites, maybe?

the cherenkov light is still visible (a faint blue shadow on the webcam pics).
this is the normal glow of a (outdoor) spent fuel pool. i would worry, if it is NOT visible (that could mean, the pool is dry)

 

[elektrownik]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

The reactor (only one in Poland) is old (from 70s) and it is research reactor, it have small power (30MW) but it generate 80% more neutrons than normal reactor. It is not military or private, it owner is government. Also this reactor is only 30km from Warsaw (capital of Poland)... Good that they change this fuel from 80 to 36%, they fuel is from Russia...
You can see some pictures here: http://iea.cyf.gov.pl/nowa/index.php?option=com_wmtsimpleflashgallery&Itemid=93
And here video:

 

[Rive]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

Low power research and/or training reactors (up to dozen megawatts) are 'common', even in the US. If you google 'TRIGA' or 'TRIGA flash' you can see some really nice vids about them.

80% enrichment is unusual, but such fuels are being withdrawn for now and used only special military or scientific reactors AFAIK.

 

[mikefj40]

the cherenkov light is still visible (a faint blue shadow on the webcam pics).
this is the normal glow of a (outdoor) spent fuel pool. i would worry, if it is NOT visible (that could mean, the pool is dry)

This is from the evening of April 1. Play 00:42 to 00:45 and you'll see the glow in the dark spot. http://www.youtube.com/watch?v=CtgRBpgbZww&feature=related. I believe it's been visible on a few other occasions. Is that the SW corner of #4?

 

[mikefj40]

Evening glow from April 2 - 4: http://www.youtube.com/watch?v=7vhI86uYquc&feature=related

 

[Samy24]

Low power research and/or training reactors (up to dozen megawatts) are 'common', even in the US. If you google 'TRIGA' or 'TRIGA flash' you can see some really nice vids about them.

80% enrichment is unusual, but such fuels are being withdrawn for now and used only special military or scientific reactors AFAIK.

Maybe it is a research breeder reactor? 20% Plutonium and 80 % Uranium is normal. Many countries experiment with this. So it must be safe.

 

[Borek]

It is terrible to hear what experiments are done in europe. Who will take the responsibility if something happens? Is this military or private stuff?

http://www.iea.cyf.gov.pl/index_ang.html

http://www.iea.cyf.gov.pl/historia_ang.html

 

[elektrownik]

Maybe it is a research breeder reactor? 20% Plutonium and 80 % Uranium is normal. Many countries experiment with this. So it must be safe.

No, there is no plutonium, only uranium.

 

[M. Bachmeier]

I hate the sort of headlines such stories generate, talking about 'rising levels'. Without knowing whether the robot(s) visited exactly the same locations at reactor 1 as they did on their first visit, we don't know if anything has risen, or whether the robots just stumbled upon a more contaminated area this time.

Either way its not a good number, but numbers even higher than this would not surprise me as they slowly explore further.

These sorts of numbers are also a reason not to stretch the complaints of PR and coverups too far. In theory there may be plenty we are not being told but they have also released plenty of info that was not good news by any stretch of the imagination. The explosions somewhat reduced the temptation to do a complete and utter coverup, and although I am not overjoyed with the quality of data that is available to us, its a lot more than I might have imagined we would get.

"The explosions somewhat reduced the temptation to do a complete and utter coverup, and although I am not overjoyed with the quality of data that is available to us, its a lot more than I might have imagined we would get."

I don't think a 'cover-up' is the way most Japanese would perceive selective information dissemination. I think that most would either believe, or like to believe that information is controlled in the best interests of workers, people displaced, long term economic factors and the desire not to bring nuclear contamination shame to those exposed.

There are many Japanese who never reported suspected radiological effects upon they're children (Hiroshima, Nagasaki) because of stigma. There are some in Japan who might believe these events to be punishment for arrogance.

If there are errors in the degree of timely reporting of events, it most likely has to do with what (persons in the position of responsibility) feel is the path of least harm. TEPCO has no financial future, so no motive to be irresponsible. Their employees, however, are aware of their future financial difficulties and never forget that almost all have suffered personal loss. If errors did not occur in this situation I would wonder if they (TEPCO personnel) were human.

I make no criticism of you Steve, but thought that we all could apply some perspective to our analysis'. Many errors are made when one faces enemies on multiple fronts...

 

[ascot317]

Thanks for the ideas about fission/not fission difference.

About explosion/recriticality: IMHO every explosion were hydrogen explosion and maybe containment damage, but none of them were originated directly from any SFP. It would scatter at least some fuel, and scattered/damaged fuel rods would cause much more serious contamination nearby than the actually observed. It would end in Chernobyl-style radiation zones around the affected unit (with much stronger Uranium and Plutonium presence).

There's nothing visible on the IR pictures. Spent fuel is quite hot. Particles thrown out of the SFP are either very small, or very few.
The IR pictures show only the SFP itself to be hot, nothing around it. Ballistic fuel would likely disintegrate and spread pellets all over the place, leaving a lot of traces around the SFP (and not "just" 1 mile away).

 

[elektrownik]

Questions: What is radiation in core at max reactor power, what is radiation in core after shutdown, what would be radiation of fuel rod/set from sfp, without water or any other protection ?

 

[Astronuc]

"Damage" was a highly misleading euphemism. That is what I come to understand now.

Not to me. As a nuclear engineer, fuel designer and fuel analyst, damage simply means 'Failure!', particularly in the context of an 'accident'. It means something happened that shouldn't have, so it is a failure - a violation of the prime directive - 'Thou shall not allow fission products into the environment!'. In the context of core damage, that is a BIG deal, and I would expect cladding breach (fuel failure).

More importantly is the fraction of core that has breached/ruptured cladding, and for that one has to go look at the activities being measured.

 

[PietKuip]

Not to me. As a nuclear engineer, fuel designer and fuel analyst, damage simply means 'Failure!', particularly in the context of an 'accident'. It means something happened that shouldn't have, so it is a failure - a violation of the prime directive - 'Thou shall not allow fission products into the environment!'. In the context of core damage, that is a BIG deal, and I would expect cladding breach (fuel failure).

More importantly is the fraction of core that has breached/ruptured cladding, and for that one has to go look at the activities being measured.

My interpretation (I am not in the industry) of "damaged fuel rods" would be rather conservative. It could mean that they were bent or corroded. A damaged car can still be functional: a scratch, a dent. Maybe worse. But one would not describe a burnt-out car wreck as "a damaged car".

Of course, all the emissions meant that volatiles had escaped, so they would have burst open, I realized that. But I had not realized that it meant that rods had desintegrated, that their fuel pellets had fallen out.

 

[MiceAndMen]

We're not in the 80ies or 90ies anymore, making information available to masses is the easiest thing to do. In this situation, there's absolutely no reason to withhold information. We're beyond the stage of possible mass panic.

There have been decades of collusion between the nuclear industry, regulators, and the media in Japan. There are ample reasons having nothing to do with mass panic for them to want to withold information.

http://www.bloomberg.com/news/2011-03-17/japan-s-nuclear-disaster-caps-decades-of-faked-safety-reports-accidents.html

People are fired from their jobs if they dare to question the official company line.

http://japanfocus.org/-Makiko-Segawa/3516

I don't think a 'cover-up' is the way most Japanese would perceive selective information dissemination. I think that most would either believe, or like to believe that information is controlled in the best interests of workers, people displaced, long term economic factors and the desire not to bring nuclear contamination shame to those exposed.

There are many Japanese who never reported suspected radiological effects upon they're children (Hiroshima, Nagasaki) because of stigma. There are some in Japan who might believe these events to be punishment for arrogance.

If there are errors in the degree of timely reporting of events, it most likely has to do with what (persons in the position of responsibility) feel is the path of least harm.

Wow. They are certainly under tremendous pressure from many sides. I do not agree that their culture absolves irresponsible actions on their part in the name of some "path of least harm". If shame is necessary then it needs to be felt, and strongly, by those responsible. They should be shamed where appropriate. They NEED to be shamed where appropriate.

http://www.nytimes.com/2011/04/27/world/asia/27collusion.html?_r=1&hpw=&pagewanted=all

Does anyone think TEPCO's plan to remediate the situation over the next 3, 6 and 9 months is realistic? They barely got off of square one and found their plan to fill Unit 1's containment with water may be compromised by a leak. They are only now coming to the realization that Unit 4's SFP is probably leaking.

Here is what Japanese leaders have to fear: that at some point an international consensus develops that they are no longer capable of managing the ongoing problems on their own. At some point, perhaps, the international community may find it desirable to take away the keys to the car, so to speak, and TELL them how to proceed with the cleanup.

Patience does not last forever, and Japans's political and industrial institutions are well aware of that. The longer they are able to prolong a "fog of war" type atmosphere surrounding this fiasco, the longer they can put off their day of reckoning.

 

[M. Bachmeier]

Not to me. As a nuclear engineer, fuel designer and fuel analyst, damage simply means 'Failure!', particularly in the context of an 'accident'. It means something happened that shouldn't have, so it is a failure - a violation of the prime directive - 'Thou shall not allow fission products into the environment!'. In the context of core damage, that is a BIG deal, and I would expect cladding breach (fuel failure).

More importantly is the fraction of core that has breached/ruptured cladding, and for that one has to go look at the activities being measured.

Which I assume to mean fuel breaking up, but not melting. I'm sure it is not possible from the data (questionable, instruments and all, as it is) to know that melting has occurred? It may be sitting in lower containment, but not core melt? However, the events around #3 are disturbing and unresolved.

 

[DSamsom]

Mm, something's going wrong there. See webcam image 28/4 08:00 AM (Japan Time)

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

 

[Astronuc]

Question for Astronuc et al:

As I think about this, if the shape and depth of the SFP could focus the blast into a vertical mushroom, then the shape and depth of the SFP, particularly if there were water covering all or part of the spent fuel would also tend to focus the force of an explosion toward the bottom of the SFP. Might it be that either a blast from the primary containment or a blast from hydrogen + air in the service floor, "amplified" by the geometry of the SFP and efficiently transmitted by water in the SFP did indeed exert a hydrostatic, crushing force on the spent fuel assemblies?

This wouldn't be a shaped HE charge crushing two subcritical hemispheres of plutonium, but on a much larger scale, a large explosion crushing several tons of spent fuel racks -- at least in theory, the hypothesis of a sudden criticality in the SFP doesn't seem too far fetched to a lay person.

The fuel in the SFP is 'spent', in addition to the fact that is started with low enrichment. The available reactivity is low because it is 'spent'. The rate a which positive reactivity could be inserted is relatively low, so a prompt critical event is unlikely. Coming out of a subcritical configuration with a very low neutron source, rather than starting at a critical configuration, I don't believe the configuration in the SFP supports prompt supercritical.

The explosions at Units 1 and 3 occurred well before the pools would have dried out, and it is more likely the hydrogen came from oxidation of the cladding in the cores.

I don't see the explosions being nuclear.

If the pools had dried out, there certainly wouldn't be any moderator to allow criticality. If there was water covering the fuel at the time of the explosion, the pressure in the pool would have been more of an increase in hydrstatic pressure, and that would crush the fuel into a more critical configuration.

Re-criticality would have been a concern AFTER the hydrogen explosions, when they TEPCO was reintroducing water into the SFPs. However, I would have expected them to borate that water.

All I see are chemical (H₂+O₂) explosions, not nuclear.

 

[PietKuip]

At some point, perhaps, the international community may find it desirable to take away the keys to the car, so to speak, and TELL them how to proceed with the cleanup.

Patience does not last forever, and Japans's political and industrial institutions are well aware of that. The longer they are able to prolong a "fog of war" type atmosphere surrounding this fiasco, the longer they can put off their day of reckoning.

I see the international nuclear industrial complex colluding with them. The Swedish nuclear authority says that the French regulator was out of line to regard Fukushima as an INES level 6 accident when the Japanese said 4 (or later 5).

It needs a British professor Busby to produce alarming graphs of uranium spreading out over the Pacific from tabular EPA data. The EPA that does not want to monitor the radioactivity in fish.

The IAEA (with its Japanese boss) is completely passive.

 

[M. Bachmeier]

Mm, something's going wrong there. See webcam image 28/4 08:00 AM (Japan Time)

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

Hard to say it looks like venting of 1-3, any current sat photos?

 

[NUCENG]

So, let's take the following example for dummies like me:

Let's guess there's an RPV with only one fuel rod. Now there have been severe cooling problems. The fuel rod was uncovered for a short amount of time and has oxidated and ruptured. We don't know if it indeed has molten.
But because of the constant cooling, fission products such as iodine, cesium, cobalt, strontium etc. have been washed out and are now somewhere in the RPV, the dry- and wetwell.
CAMS is now measuring extremely high radiation, indicating that 30% of the radiating inventory is somewhere in the drywell and 5% somewhere in the wetwell.
Overall it doesn't necessarily mean that the fuel has molten. It's only indicating, that the fuel cladding ruptured and fission products can escape from the fuel rods?

Back to Fukushima: So 55% of Unit 1s core inventory of fission products is not contained by the fuel rods anymore but swimming in the cooling water? But there's NOT 55% of the core gone, like molten down? Or at least, those numbers do not indicate or show whether or how much of the core has molten?

You have it as I understand it. And if you have used the SRVs venting steam from the RPV to the suppression pool some of that radioactivity went along. And then there are vacuum breakers that may have returned some of that radioactivity to the drywell outside the RPV and much less shielded from the CAMS detectors. If there has been a break in piping or instrument lines outside the RPV, the liquid and steam released directly into containment releases more radioactivity into containment. That will increase pressure in the drywell and spill over into the vent lines to the torus. And all that can happen while most of the core metal and core pellets remain inside the RPV. And hydrogen gas can go everywhere the fission products do.

 

[Astronuc]

Which I assume to mean fuel breaking up, but not melting. I'm sure it is not possible from the data (questionable, instruments and all, as it is) to know that melting has occurred? It may be sitting in lower containment, but not core melt? However, the events around #3 are disturbing and unresolved.

Yes - I expect the fuel oxidized like heck, hydrided and broke apart. It might be rubble, but didn't necessarily melt - particularly if the actually had water in the bottom third of the core.

Jorge Stolti's figures are interesting. The plot the recorded/reported water levels. I don't necessarily trust them, because I don't know the state of the instrumentation.

If there was water, that precludes melting in the bottom of the core, and particularly the RPV.

However, I would imagine close to half, if not more, of the fuel is damaged to the point of cladding failure in Units 1, 2 and 3.

 

[Astronuc]

Mm, something's going wrong there. See webcam image 28/4 08:00 AM (Japan Time)

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

I would very much like to be there in person.

 

[clancy688]

I would very much like to be there in person.

Is that supposed to be ironic...? You saw the radiation maps. High radiation hotspots all over the plant. And now there's a plume... could be fog, could be a giant insect swarm, could be pure cesium... ^^;

 

[turbo]

I would very much like to be there in person.

My wife and I would very much like you to stay right here state-side so maybe we can see you and yours in years to come.

 

[Astronuc]

My interpretation (I am not in the industry) of "damaged fuel rods" would be rather conservative. It could mean that they were bent or corroded. A damaged car can still be functional: a scratch, a dent. Maybe worse. But one would not describe a burnt-out car wreck as "a damaged car".

Of course, all the emissions meant that volatiles had escaped, so they would have burst open, I realized that. But I had not realized that it meant that rods had desintegrated, that their fuel pellets had fallen out.

Yes - damage means some abnormality - a dent or ding - such that one cannot use the fuel anymore because it's outside of design spec. A damage fuel rod could be corroded, but still hermetic (sealed), but one would not use it, because it might fail. Similarly, a damaged fuel assembly means that it got dinged/dented, therefore is out of spec, and could lead to failure if used, so it's gone. Damage implies that a fuel rod or fuel assembly may not be able to perform its intended function.

Fuel failure means the cladding is breached - and fission products have escaped the first barrier between them and the environment. The industry takes fuel failures, even one, very seriously.

Core damage is a more significant context. It is a gravely serious matter, and then one would asked how damaged? How many failures? What's the off-gas and coolant activity? . . . . That's a very BIG deal.

 

[Astronuc]

Is that supposed to be ironic...? You saw the radiation maps. High radiation hotspots all over the plant. And now there's a plume... could be fog, could be a giant insect swarm, could be pure cesium... ^^;

No - I'm not being ironic. If TEPCO invited me, I'd be on-site ASAP.

 

[M. Bachmeier]

You have it as I understand it. And if you have used the SRVs venting steam from the RPV to the suppression pool some of that radioactivity went along. And then there are vacuum breakers that may have returned some of that radioactivity to the drywell outside the RPV and much less shielded from the CAMS detectors. If there has been a break in piping or instrument lines outside the RPV, the liquid and steam released directly into containment releases more radioactivity into containment. That will increase pressure in the drywell and spill over into the vent lines to the torus. And all that can happen while most of the core metal and core pellets remain inside the RPV. And hydrogen gas can go everywhere the fission products do.

I have never heard of a BWR or BWFF (Boiling Water Fossil Fuel) producing a directional force or equivalent to what happened at #3?

I've been present to see, first hand, what happens in an ordinary water boiler accident and am just lacking some explanation for #3 explosive sounds and two steam expansions? (five sounds)...

 

[default.user]

Yes - damage means some abnormality - a dent or ding - such that one cannot use the fuel anymore because it's outside of design spec. A damage fuel rod could be corroded, but still hermetic (sealed), but one would not use it, because it might fail. Similarly, a damaged fuel assembly means that it got dinged/dented, therefore is out of spec, and could lead to failure if used, so it's gone. Damage implies that a fuel rod or fuel assembly may not be able to perform its intended function.

Fuel failure means the cladding is breached - and fission products have escaped the first barrier between them and the environment. The industry takes fuel failures, even one, very seriously.

Core damage is a more significant context. It is a gravely serious matter, and then one would asked how damaged? How many failures? What's the off-gas and coolant activity? . . . . That's a very BIG deal.

Have I understood you correctly?
You believe that there was no damage to the nuclei in the reactors, and therefore no meltdown?

 

[PietKuip]

The fuel in the SFP is 'spent', in addition to the fact that is started with low enrichment. The available reactivity is low because it is 'spent'. The rate a which positive reactivity could be inserted is relatively low, so a prompt critical event is unlikely. Coming out of a subcritical configuration with a very low neutron source, rather than starting at a critical configuration, I don't believe the configuration in the SFP supports prompt supercritical.

The explosions at Units 1 and 3 occurred well before the pools would have dried out, and it is more likely the hydrogen came from oxidation of the cladding in the cores.

I don't see the explosions being nuclear.

If the pools had dried out, there certainly wouldn't be any moderator to allow criticality.

Would a fast-neutron chain reaction in the plutonium be absolutely excluded?

 

[Astronuc]

Questions: What is radiation in core at max reactor power, what is radiation in core after shutdown, what would be radiation of fuel rod/set from sfp, without water or any other protection ?

In the core at power, the radiation field is so very different than simple radionuclide decay. The thermal and fast neutron fluxes are on the order of 10¹⁴ n/cm²-s. And the gamma and beta radiation is intense.

About 20 years ago, I was involved as a consultant to a utility where they managed to break a fuel rod outside of the core. It had failed during the cycle, and they managed to break it while moving the assembly during the refueling outage. The fuel rod was not discovered until they were draining the cavity above the RPV, and the radiation alarms went off. The operators stopped, reflooded the cavity and went to take a look.

The fuel rod was broken in 4 pieces. The top and bottom sections were about 2 ft each, and there were two 5-ft sections. One section was empty of fuel! It's activity was about 5000 R/hr, IIRC. Another section was about 2000 R/hr. I'd have to dig up my notes - but they were hot. The NRC wanted to know - where did 1 kg of UO2 go!? Well the answer was - it was distributed in the primary system as fuel particles and uranyl ions. The Np-239 in the reactor coolant (as well as increased Xe, Kr, I and Cs) was a really good indication that they had a degraded failure in the core. They just didn't bother to go look for it during the outage.

The senior plant management were fired.

 

[M. Bachmeier]

No - I'm not being ironic. If TEPCO invited me, I'd be on-site ASAP.

Astronuc, as a manager I'm not be surprised but your sentiments. I feel a certain amount of responsibility and commitment to the projects I undertake and am always willing to assume some degree of association and responsibility. No good manager ducks his responsibility, or his ability to ameliorate a site site situation.

 

[Astronuc]

Have I understood you correctly?
You believe that there was no damage to the nuclei in the reactors, and therefore no meltdown?

I believe there is washout and dissolution of the fuel, but not nessarily melting - particularly if there was water in the bottom third of the cores. The question is - was there water in the bottom third of the cores?

 

[rowmag]

Further follow-up (context: cphoenix's superheated steam explosion theory):

Searching through the file finds no other reference to the plastic covering, but some references to fiberscope searches for foreign matter in the assemblies (not much found), but no particular reason given why this should be a MOX-specific issue (to go to NUCENG's query). So perhaps such plastic covering may have been used in SFP4 as well?

I skimmed through a bunch of past press releases on the TEPCO site last night, particularly (but not exclusively) those related to Unit 4. There are several reports of foreign objects falling into the SFP or being found in the stored fuel assemblies over the years (bolts, washers, metal shavings, etc.), and the more recent reports mention that they are continuing strict countermeasures against foreign object introduction that were adopted a few years ago. The only enumeration I found of what those countermeasures consists of was basically different ways of saying, "we'll be more careful," and no mention was made of plastic covers being adopted on a regular basis. In fact the locations of where some of the foreign objects were found inside the fuel assemblies suggest that they are not using plastic covers on a regular basis. I also see no mention of plastic covers in the list of things to be done in the maintenance period that was underway when the earthquake hit.

So, not much support so far for the possibility of plastic covers being in place in SFP4.
Maybe the covers were a special-case for the MOX study after all?

 

[Astronuc]

Would a fast-neutron chain reaction in the plutonium be absolutely excluded?

Fast reactors use a tight fuel lattice configuration and 20% fissile inventory. LWRs have a maximum of 5%, and TEPCO probably uses 4% or less, based on annual cycles and between 1/4 and 1/3 core batch sizes. The spent fuel is even lower enrichment because of depletion of fissile inventory. So no fast-neutron chain reaction.

 

[Astronuc]

Further follow-up (context: cphoenix's superheated steam explosion theory):


I skimmed through a bunch of past press releases on the TEPCO site last night, particularly (but not exclusively) those related to Unit 4. There are several reports of foreign objects falling into the SFP or being found in the stored fuel assemblies over the years (bolts, washers, metal shavings, etc.), and the more recent reports mention that they are continuing strict countermeasures against foreign object introduction that were adopted a few years ago. The only enumeration I found of what those countermeasures consists of was basically different ways of saying, "we'll be more careful," and no mention was made of plastic covers being adopted on a regular basis. In fact the locations of where some of the foreign objects were found inside the fuel assemblies suggest that they are not using plastic covers on a regular basis. I also see no mention of plastic covers in the list of things to be done in the maintenance period that was underway when the earthquake hit.

So, not much support so far for the possibility of plastic covers being in place in SFP4.
Maybe the covers were a special-case for the MOX study after all?

All utilities are concerned with 'foreign materials' on nuclear fuel, and all have a 'foreign materials exclusion' program - at least they should by now. Failure due to 'debris' has been a significant issue in the 1980s through 1990s. Debris-resistant features were added to the fuel, but more importantly, utilities implement programs to prevent contamination of fuel. Foreign materials do not belong in the fuel or the core.

Fresh fuel arrives at the plant in containers, and there is usually a plastic cover. MOX fuel in which the MOX is derived from reprocessed spent fuel has more radioactivity than conventional UO2, so it is protected more so. The plastic covers are there to protect the fuel and to some extent protect the workers. However, the plastic covers are normally removed when the fuel is placed under water. On the other hand, I am not familiar with TEPCO practices or procedures, or the context of plastic covers in conjunction with fuel in Unit 4. Unit 4 did have a large batch of fresh fuel, but Unit 3 had MOX fuel - and only 32 assemblies of MOX.

 

[densha_otoko]

Smoke from 4 (maybe 3) on the increase this morning. Most I have seen in April, yet it might just be the first calm wind day in weeks. http://www.tepco.co.jp/nu/f1-np/camera/index-j.html.

 

[MiceAndMen]

I see the international nuclear industrial complex colluding with them. The Swedish nuclear authority says that the French regulator was out of line to regard Fukushima as an INES level 6 accident when the Japanese said 4 (or later 5).

It needs a British professor Busby to produce alarming graphs of uranium spreading out over the Pacific from tabular EPA data. The EPA that does not want to monitor the radioactivity in fish.

The IAEA (with its Japanese boss) is completely passive.

IAEA is a completely toothless tiger according to some reports I've seen. No surprise there. I'm more concerned about China and the Koreas, especially if the plant is still chuffing out radioactivity when typhoon season gets going.

 

[MadderDoc]

Mm, something's going wrong there. See webcam image 28/4 08:00 AM (Japan Time)

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

Yes, the position of this plume at 08:00 is a bit unusual. It looks to me as if it is coming from no 1? That's rare. In the current webcam at 09:00 however, it appears SFP4 has now started steaming, so no longer easy to discern what's going on behind that. Cache of older than current webcam is held at: http://gyldengrisgaard.dk/tepcowebcam/

 

[sp2]

If you don't mind my asking, how the hell did they clean that up?

That sounds like a big-deal accident.

In the core at power, the radiation field is so very different than simple radionuclide decay. The thermal and fast neutron fluxes are on the order of 10¹⁴ n/cm²-s. And the gamma and beta radiation is intense.

About 20 years ago, I was involved as a consultant to a utility where they managed to break a fuel rod outside of the core. It had failed during the cycle, and they managed to break it while moving the assembly during the refueling outage. The fuel rod was not discovered until they were draining the cavity above the RPV, and the radiation alarms went off. The operators stopped, reflooded the cavity and went to take a look.

The fuel rod was broken in 4 pieces. The top and bottom sections were about 2 ft each, and there were two 5-ft sections. One section was empty of fuel! It's activity was about 5000 R/hr, IIRC. Another section was about 2000 R/hr. I'd have to dig up my notes - but they were hot. The NRC wanted to know - where did 1 kg of UO2 go!? Well the answer was - it was distributed in the primary system as fuel particles and uranyl ions. The Np-239 in the reactor coolant (as well as increased Xe, Kr, I and Cs) was a really good indication that they had a degraded failure in the core. They just didn't bother to go look for it during the outage.

The senior plant management were fired.

 

[Danuta]

Many countries experiment with this. So it must be safe.

LOL. I know you didn't mean this the way I read it.

 

[UNECCS]

2. they ADD the core-damage values of drywell and wetwell. i simply don't understand the logic behind that. shouldn't both methods give the SAME result?

I have same question.
I think reason is Goodness of TEPCO's hart.

 

[Astronuc]

If you don't mind my asking, how the hell did they clean that up?

That sounds like a big-deal accident.

It wasn't a big accident. But it was serious because the fuel rod broke outside of the reactor vessel.

They carefully picked up the pieces of broken fuel rod and put them in the appropriate container. About half the fuel had washed out and ended up dispersed in the primary system. It would mostly be caught on filters. It costs a utility big bucks to disposed of those filters, hence utilities really don't want fuel failures - not even one - for an economic standpoint and from a safety standpoint.

PWRs are actually capable of handling hundreds of failed rods, but no one would ever want to have to deal with that. In the last 20 years, even one failure causes alarm at a NPP.

As of Jan 1, 2011, the US has adopted a zero fuel failure policy. It has been an industry objective for the last two decades.

 

[MiceAndMen]

If you don't mind my asking, how the hell did they clean that up?

That sounds like a big-deal accident.

In 2004 it was revealed that the Vermont Yankee plant had lost track of some fuel rod pieces. They were last seen in 1979. A couple of years before that, the operators of the Millstone I plant lost 2 fuel rods completely. They are reasonably sure they know what happened to them, but can't prove it.

http://www.vpr.net/news_detail/71411/

There have been other cases, too. In the United States incidents such as this most definitely become federal cases.

 

[MadderDoc]

This is from the evening of April 1. Play 00:42 to 00:45 and you'll see the glow in the dark spot. http://www.youtube.com/watch?v=CtgRBpgbZww&feature=related. I believe it's been visible on a few other occasions. Is that the SW corner of #4?

Yes, more precisely the position of that light is the upper half of the remaining top wall panel on the south wall of unit 4. Tepco has installed powerful lamps in the area, so I think it more likely is a reflection of light from those that we see in that video, than Cherenkov light coming from the sfp.

 

[Astronuc]

In 2004 it was revealed that the Vermont Yankee plant had lost track of some fuel rod pieces. They were last seen in 1979. A couple of years before that, the operators of the Millstone I plant lost 2 fuel rods completely. They are reasonably sure they know what happened to them, but can't prove it.

http://www.vpr.net/news_detail/71411/

In the United States incidents such as this most definitely become federal cases.

I've been involved in similar situations where we reconstructed a fuel rod or two from various broken pieces, and records.

For older units like VY, Millstone-1 and Pilgrim, it can be a royal pain for complete accountability. VY, and I believe Pilgrim, had some problems with CILC failures in the 1970s. Millstone-1 may have had similar problems. I remember reading some horrendous off-gas activities.

 

[sp2]

Thanks.

So, forgive me for another stupid question, but does that mean somebody's absorbing 20 or 50 Sv/hr for a while (or anything close to that), somewhere in that clean-up process?
(I assume not, since they'd probably be dead?)

Also, what's the 'zero-tolerance policy' mean? Just that these incidents have to be reported now?

It wasn't a big accident. But it was serious because the fuel rod broke outside of the reactor vessel.

They carefully picked up the pieces of broken fuel rod and put them in the appropriate container. About half the fuel had washed out and ended up dispersed in the primary system. It would mostly be caught on filters. It costs a utility big bucks to disposed of those filters, hence utilities really don't want fuel failures - not even one - for an economic standpoint and from a safety standpoint.

PWRs are actually capable of handling hundreds of failed rods, but no one would ever want to have to deal with that. In the last 20 years, even one failure causes alarm at a NPP.

As of Jan 1, 2011, the US has adopted a zero fuel failure policy. It has been an industry objective for the last two decades.

 

[NUCENG]

I believe there is washout and dissolution of the fuel, but not nessarily melting - particularly if there was water in the bottom third of the cores. The question is - was there water in the bottom third of the cores?

This event seems to exceed the predictions of the LOCA and Arrested Core Melt scenario which is the design basis for radiological consequences for plant licensing. The scenario of a total loss of AC (Station Blackout) and Loss of decay heat removal after battery failure are way beyond design basis space. The complete loss of Secondary Containment is beyond design basis. Spent fuel pool fires, and hydrogen explosions have been postulated and studied, but never to the extent of four plants on the same site.

But so far the consequences are not very far from predictions for the design basis accident. Evacuations have helped. But even employees and contractors on site are still within emergency dose limits. The reactors are write-offs, Dislocation and compensation of evacuees will be expensive. Impact of the loss of power production and expense of replacing that generation will affect the economy for a while. Japan which is short of space for its population will be more crowded. Long term health impacts will probably have to be estimated because they may not be statistically detectable. I hesitate to say no radiation induced early deaths, because I agree that the accident may be responsible for traumas and suicides as well. But this accident could have been, and still could become, so much worse.

 

[dh87]

About explosions, I am not expert, I write only on base of observations: #1 explosion, big pressure in reactor building from venting then small, centered hydrogen explosion. #3 explosion, yest we can see it on video, first fireball from SFP location, then big explosion going up, but I don't think that it was from recriticality in SFP, I think that first explosion in SFP damaged drywell and reactor vessel so there was big release of pressure and maybe hydrogen explosion. If there would be so big explosion from SFP then there would be more very hight radioactive pieces of fuel rods, but they found only 300 and 900 mSv/h mayby from reactor cap... Also the big "up" explosion appear to be from center of building/core location not from sfp like fireball...

I claim to know less about explosions than you, but I had been thinking about the #3 explosion the same way as you for exactly the reasons you cite. The trouble with this explanation is that the reported pressures in the primary containment vessel don't seem to be changed by the explosion. In contrast, in #2 the pressures fall sharply after the explosion apparently blows a hole in the containment.

 

[Astronuc]

This event seems to exceed the predictions of the LOCA and Arrested Core Melt scenario which is the design basis for radiological consequences for plant licensing. The scenario of a total loss of AC (Station Blackout) and Loss of decay heat removal after battery failure are way beyond design basis space. The complete loss of Secondary Containment is beyond design basis. Spent fuel pool fires, and hydrogen explosions have been postulated and studied, but never to the extent of four plants on the same site.

But so far the consequences are not very far from predictions for the design basis accident. Evacuations have helped. But even employees and contractors on site are still within emergency dose limits. The reactors are write-offs, Dislocation and compensation of evacuees will be expensive. Impact of the loss of power production and expense of replacing that generation will affect the economy for a while. Japan which is short of space for its population will be more crowded. Long term health impacts will probably have to be estimated because they may not be statistically detectable. I hesitate to say no radiation induced early deaths, because I agree that the accident may be responsible for traumas and suicides as well. But this accident could have been, and still could become, so much worse.

I believe the DBE/DBAs assume core coolability is re-established pretty quickly using available systems. I don't think DBAs assume the ECCS and EDGs (emergency power) is completely gone.

This event is an entirely different chapter. It is a textbook example of what to avoid.