Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[dezzert]

Sorry, in a list of the most the most dangerous resource ever created on this planet, nuclear isn't anywhere near coal (including TMI2, Chernobyl and Fukushima). ]

There is one major difference. If there is a world calamity, EQs like Tohoku, or just a shutdown of the grid, a coal plant no longer in use is just a coal plant no longer in use, where as a nuke plant is a disaster waiting to happen. Its the future that doesn't look bright.

If Fukushima is to teach us anything, its that the future is entirely unpredictable. And its that uncertainty that needs to be addressed, not whether or not nuclear can be made safe under current paradigms. If it can never be made entirely safe, why would we burden future generations with our need for electric shavers and all the rest.

 

[nikkkom]

There is one major difference. If there is a world calamity, EQs like Tohoku, or just a shutdown of the grid, a coal plant no longer in use is just a coal plant no longer in use, where as a nuke plant is a disaster waiting to happen.

Not necessarily. There is no law of physics which says NPP can't be designed to shut down safely without any electric power.

If Fukushima is to teach us anything, its that the future is entirely unpredictable.

Yes. Theoretically, tomorrow we may be invaded by aliens. So what?

If it can never be made entirely safe, why would we burden future generations with our need for electric shavers and all the rest.

Nothing can be made *entirely* (meaning: 100%) safe.

 

[dezzert]

Quick question concerning the SGTS and the R4 blast. I know that the valves fail open, but I don't understand why the hydrogen would find its way up the SGTS and through the filtration system on 4, (4 being an airtight structure, yes) when it had an obvious vent path through the 3/4 stack. Wouldnt there already be a draw occurring up the stack.

The amount of hydrogen needed to do the level of damage to R4, including damage as low as the 1st floor, would have been massive. How does this much hydrogen enter an airtight structure in these amounts, and penetrate down to the 1st floor from the 4th floor, while most is being exited out the stack, without having built to levels in R3 that would have caused it to explode much sooner.

And if this much hydrogen did enter R4, why did it not exit R4 (after the R3 blast) the same way it came in. After R3 blew the SGTS was severed at the R3 side of the stack, an open vent path to the outside. If the pressure that built up in R3 pushed that much hydrogen out the SGTS, why would not the subsequent pressure build up in R4 push it out the same line which is now open to the atmosphere (and without even having to go through a second filtration system).

This one never has worked for me and still doesnt. Any help is appreciated.

 

[dezzert]

Not necessarily. There is no law of physics which says NPP can't be designed to shut down safely without any electric power.

But there is a law of physics that says that any reactor designed to be water cooled cannot be shutdown safely without water. And you get the water into the plant how?

Yes. Theoretically, tomorrow we may be invaded by aliens. So what?

Not sure what aliens has to do with nuke plants, so I think Ill let this one slide.

Nothing can be made *entirely* (meaning: 100%) safe.

Excuse me? Have you ever heard of distributed power systems.
And the 'nothing can be made perfectly safe' argument is almost as ridiculous as referring to aliens. It all depends on the level of threat you are trying to be made safe from.

 

[Rive]

But there is a law of physics that says that any reactor designed to be water cooled cannot be shutdown safely without water.

Really? Can you please give me a link or something on that one?

Because I can think of some ways to achieve this (also not on-topic here)...

 

[nikkkom]

But there is a law of physics that says that any reactor designed to be water cooled cannot be shutdown safely without water.

Wrong. But anyway...

And you get the water into the plant how?

Water can be transferred by gravity alone.

 

[dezzert]

Really? Can you please give me a link or something on that one?

Because I can think of some ways to achieve this (also not on-topic here)...

I only joined the safety discussion because others brought it up. I agree its off topic. But I would like to know in what ways a water cooled reactor in an emergency like Fukushima can be cooled without it, and why weren't these alternatives brought forth earlier, like say March 11th.

 

[dezzert]

Water can be transferred by gravity alone.

Excellent idea. And how high would the source have to be to produce the amount of pressure needed during a meltdown. And how big would the pipe have to be to deliver water to 5 reactors, 6 SFPs, and one huge common pool in the amounts needed. Practically speaking.

But yes its off topic and I swear I won't go off topic again. End of the safety discussion for me. My only real interests at this time have to do with understanding the current situation. Which is why I was asking about the SGTS and R4. To me this is an important issue that needs deep analysis, and why I came on yesterday to post. I am sorry I got diverted into the safety discussion, because to me safe nuclear is an oxymoron, and therefor pointless to discuss IMHO.

 

[gregtomko]

Sorry, in a list of the most the most dangerous resource ever created on this planet, nuclear isn't anywhere near coal (including TMI2, Chernobyl and Fukushima).

There has never been a nuclear accident in any US Naval Nuclear Propulsion Plant or prototype.

Reference: http://www.nasa.gov/pdf/45608main_NNBE_Progress_Report2_7-15-03.pdf

When the total damage is assessed for coal, every byproduct is gone after a few decades. In nuclear much of the hazardous waste isn't gone for tens of thousands of years. If spent fuel is safe today, how do you know it will be secure 100 years from now? Do you feel comfortable handing off responsibility for your waste to future generations?

 

[clancy688]

Water can be transferred by gravity alone.

Which worked pretty well in the current case of Fukushima...

...as long as they were able to reduce pressure by venting the containments. Wait, they couldn't vent in some cases? So they had to wait until Unit 2 for example already melted down and containment failed, so that pressure reduced and water injection was finally possible...?

 

[rmattila]

Optimization is not always simple. For example, at Fukushima Daiichi, they were able to inject firewater into the reactor because the reactor pressure vessel could be vented down to a sufficiently low pressure.

But the ability to lower the reactor pressure low enough for fire engines would not be possible, if the containment vent lines had a passive scrubber (which would be a good thing from point of view of reducing the radioactive releases), and if the RPV blowdown valves would be steam-operated rather than require compressed air (which would be good from reliability point of view).

If you sum the 2-3 bar required by a typical passive wet scrubber, and the 2-5 bar required by self-powered RPV pressure relief lines, plus the 1-3 bar needed to overcome the hydrodynamic pressure caused by the height of the RPV, you end up with a counter-pressure high enough to prevent direct firewater injection by fire engines, which typically pump to 6-10 bar.

 

[Rive]

When the total damage is assessed for coal, every byproduct is gone after a few decades.

[rant on]
That depends on the person who makes the assessment.
For example I tend to consider the CO2 to being around for some million years, and I really wonder why some ash deposites considered for mining Uranium and some heavier elements.

[/rant off]

 

[Rive]

...

One thing always confuses me about the RCIC. Was it ever considered as a 'final' solution for SBO?

While there is enough pressure difference between the wetwell and the RPV it can maintain a continuous water flow to the RPV. As I know it has only two limits: the battery power and the heat capacity of the wetwell.

But I see no reason why its turbines can't be used also for emergency generators to power the RCIC control in exchange for some more heat to the wetwell.
And some low pressure heat exchangers installed in the wetwell could take care on the heat, even with makeup water sources, like diesel powered agrocultural pumps.

 

[gmax137]

One thing always confuses me about the RCIC. Was it ever considered as a 'final' solution for SBO?

Station blackout (loss of all AC power) was not an original design basis for plants of that time. In the US, SBO first appears as a design basis (AFAIK) during the licensing of St. Lucie Unit 2 (in the mid 1980s), where the event is defined as a blackout lasting four hours. Later, the SBO was added to the US regulations with a formula for determining the duration based on site characteristics. But it's always 4, 8, or 12 hours. The 'final solution for SBO' was, the power comes back on at 4 (or 8 or 12) hours. So, the RCIC (or turbine driven auxiliary feedwater) has to operate for a fixed, finite time.

What Fukushima drives home is (1) the absolute importance of the external event design bases (since these events can lead to common cause failures like loss of both trains of service water, or loss of both diesel generators, or loss of all the switchgear) and (2) the need to consider much longer duration SBO. A third point which some people see (me included) is a kind of flaw in the design basis concept - it misses the need to design to fail gradually if the design basis is exceeded (rather than the design basis being a 'cliff edge'). This last point is hard for some to grasp.

 

[tsutsuji]

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111122_02-j.pdf Assessment of the operation of unit 1's Isolation Condenser. An English translation will probably follow soon. I attach a partial translation of the last figure.

 

[nikkkom]

Excellent idea. And how high would the source have to be to produce the amount of pressure needed during a meltdown.

A few meters above the reactor would work. Look at IC condensers at Unit 1. Their shell side is at *1 atm* at all times. As long as you have water to pour into it, they will keep reactor cooled.

In emergency (such as "IC is damaged"), there should be a procedure to depressurize reactor vessels to ~1 atm and feed the water directly to the reactor vessels. IIRC it is normally not allowed because associated rapid drop in temperature can cause cracks in piping, necessitating costly repairs. But it is infinitely better than meltdown.

And how big would the pipe have to be to deliver water to 5 reactors, 6 SFPs, and one huge common pool in the amounts needed. Practically speaking.

Who says one pipe should deliver water to all reactors? That would be a bad design wrt safety. I would even require at least two separate gravity-fed water sources per each reactor.

 

[nikkkom]

> Water can be transferred by gravity alone.

Which worked pretty well in the current case of Fukushima...

...as long as they were able to reduce pressure by venting the containments. Wait, they couldn't vent in some cases? So they had to wait until Unit 2 for example already melted down and containment failed, so that pressure reduced and water injection was finally possible...?

My points are:

(a) At Fukushima they did not ever expect to be left without electricity. They were not trained for this. The accident manuals did not tell them what to do in this case. Even emergency lights went out - how come, aren't they supposed to be battery-backed?!?

(b) Even if they would be trained for this - they did not have gravity-fed water sources. All they had is water in IC good for about 8 hours of cooling. But they were NOT trained and as such, they failed to use even that!

Both these points need fixing - worldwide.

 

[thebluestligh]

Here are some composite images of the R4 SFP generated from the TEPCO video released on 11/11/2011

http://www.tepco.co.jp/en/news/110311/movie_1111/1111_19-e.html
http://www.tepco.co.jp/en/news/110311/movie_1111/1111_20-e.html
http://www.tepco.co.jp/en/news/110311/movie_1111/1111_21-e.html

 

[dezzert]

Does anyone here buy the SGTS explanation for R4s hydrogen buildup, and if so, why?

 

[NUCENG]

Does anyone here buy the SGTS explanation for R4s hydrogen buildup, and if so, why?

I am open minded on the cause of damage on Unit 4.

Initially I received information that operators believed a second explosion had occurred in Unit 3. Other theories were of steam explosions, which I never found convincing. We basically rehjected that theory because we couldn't find photographic changes in unit 3 indicating a second explosion. Then the possibility of hydrogen from damaged fuel in a drained spent fuel pool was proposed based on NRC statements that the pool was empty. That was proved wrong by photos showing no significant damage. For a while people were looking for welding gases supporting the shroud chane project or lubricating oils as sources for the explosion.

The next theory was radiolysis of water in the spent fuel pool. Calculations were made that showed that was possible if the pool was boiling. There was some good work on this by other posters.

Then TEPCO postulated the Unit 3 source via the stack piping. Apparently that has gained credence by the photos and inspections of the debris on the 3rd and 4th floors. It is relatively easy to see a difference between an explosion inside ducting and ducting that has benn crushed or damaged from an exterior explosion. The isometric sketches of the SBGT ducting seems consistent. We don't really know when the exterior duct failed on the side of unit 3. Recent information confirms the dampers fail open and there are no backdraft damper. The explosion of unit 3 could have followed a period when the hydrogen was present with increasing hydrogen concentrations and pressure forcing hydrogen into unit 4 or the explosion itself may have been the driving force. The explosion may not have been propagated to unit 4 because the hydrogen concentration in the ducting was to rich for deflagration or detonation. The timelag before the Unit 4 explosion could have been awaiting an ignition source or dilution to a combustible or explosive mixture.

In summary I still have unanswered questions. to change the maybes into facts. If I have to answer your question, I will default to "Mythbusters" terminology and say it is somewhere neither BUSTED, nor CONFIRMED, but somewhere between POSSIBLE, and PLAUSIBLE.

 

[NUCENG]

My points are:

(a) At Fukushima they did not ever expect to be left without electricity. They were not trained for this. The accident manuals did not tell them what to do in this case. Even emergency lights went out - how come, aren't they supposed to be battery-backed?!?

(b) Even if they would be trained for this - they did not have gravity-fed water sources. All they had is water in IC good for about 8 hours of cooling. But they were NOT trained and as such, they failed to use even that!

Both these points need fixing - worldwide.

Just a partial answer. On (a) the latest reports revealed that not only EDGs were flooded, but the essential AC and DC electrical panels as well in some of the plants. That may have explained why even some DC systems or lighting failed. The timelines also suggest that some time short elapsed before flooding took out some of the systems. Some time later they were repeatedly frustrated by bringing in external systems only to see them wiped out by explosions. On (b) only Unit 1 had an IC and there is conflicting information about its use. .

 

[NUCENG]

Station blackout (loss of all AC power) was not an original design basis for plants of that time. In the US, SBO first appears as a design basis (AFAIK) during the licensing of St. Lucie Unit 2 (in the mid 1980s), where the event is defined as a blackout lasting four hours. Later, the SBO was added to the US regulations with a formula for determining the duration based on site characteristics. But it's always 4, 8, or 12 hours. The 'final solution for SBO' was, the power comes back on at 4 (or 8 or 12) hours. So, the RCIC (or turbine driven auxiliary feedwater) has to operate for a fixed, finite time.

What Fukushima drives home is (1) the absolute importance of the external event design bases (since these events can lead to common cause failures like loss of both trains of service water, or loss of both diesel generators, or loss of all the switchgear) and (2) the need to consider much longer duration SBO. A third point which some people see (me included) is a kind of flaw in the design basis concept - it misses the need to design to fail gradually if the design basis is exceeded (rather than the design basis being a 'cliff edge'). This last point is hard for some to grasp.

I would ad a bit of a clarification to your cliff edge analogy.The problem with Fukushima, and which may be present elsewhere, is that the unrecognized seismic and tsunami risk was indeed a cliffedge.

From the very beginning of nuclear plant design, there was a recognition that accidents that exceed the design basis are possible. So plant designs had two levels of design and analysis This remains true today.

The design basis for safety systems is to prevent core damage that would release any radiation. This was based by conservative deterministic analysis with margin. In the case of containment safety systems the design basis was assumed to be the safety systems had failed resulting in an "arrested core melt accident" (Arrested meaning the core was damaged, but stopped after a partial melt. Again conservative, deterministic analysis was used to assure that containment would limit radiation dose to workers and the public within limits. This included margin for system leakage. The offsite release models were based on limiting atmospheric models and that the persons exposed were at the site boundary for two hours during the worst radiological dose or continuously in the low population zone for thirt days with no evacualtion.

The second type of analysis used is for severe accidents. Here the use of probabilistic approaches is allowed. This is supported by PRA for events that resu;lt in core damage and for containment failures. The consequences are also treated as probabilities. The WASH-1400 study was the first example of a systematic PRA approach to bring it all together. Other studies have followed, indicating the WASH-1400 study overestimated the consequences. NRC has initiated a recent update in the SOARCA project.

If you think about it, TMI2 was consistent with a beyond design basis reactor accident but within the design basis of the containment. (The lack of containment at Chernobyl is outside the process I am describing.) Fukushima is a severe accident but the consequences to date seem to confirm much of the severe accident analysis.

To relate this back to your post the SBO probabilities were used to justify the coping periods. They were based on grid performance studies that are available in reports from national labs. In addition to PRAs there are Integrated Plant Examinations of External Events (IPEEE) that are PRAs for external events. Clearly the Fukushima lessons learned witll include three basis response areas. The IPEEE for seismic and flooding events will need to be reviewed and updated. The basis of the SBO programs will need to reconsider duration bases on changes to IPEEE and likely new regulations. Design changes will probably need to be installed. PRAs and IPEEEs will ned to be updated reflecting new plant modifications. And during this whole process the results of each step will need to be reviewed to identify other vulnerabilities and guide corrective actions and modifications to areas with the greatest impact.

So my contention is that the current design of plants provides complete protection for design basis events and a reasonable process to install additional protection should accidents get past that point. As a result, absent a glaring design deficiency such as the Fukushima tsunami protection, it may be closer to a hillside than a cliff. I expect that the slope of that hill will be even shallower when the process is complete.

 

[NUCENG]

When the total damage is assessed for coal, every byproduct is gone after a few decades. In nuclear much of the hazardous waste isn't gone for tens of thousands of years. If spent fuel is safe today, how do you know it will be secure 100 years from now? Do you feel comfortable handing off responsibility for your waste to future generations?

It would be unfair of me to interpret that as a defense to continued use of coal over nuclear. I think what you meant is the long term storage of spent nuclear fuel is one issue where coal is "less harmful." Is that fair?

I agree the spent fuel issue remains unsolved, but the volume of nuclear waste is miniscule compared to fly ash, which is a larger uncontrolled source of environmental radiation than spent fuel in geological storage. The chances of controlling access to that spent fuel will be much lower if we can eventually combine it in a single repository.

As to the distant future, I don''t know. That doesn't mean I don't care. But I do recognize that failing to provide for energy sources for the future will not help solve that issue - after society collapses.3

 

[NUCENG]

There is one major difference. If there is a world calamity, EQs like Tohoku, or just a shutdown of the grid, a coal plant no longer in use is just a coal plant no longer in use, where as a nuke plant is a disaster waiting to happen. Its the future that doesn't look bright.

If Fukushima is to teach us anything, its that "the future is entirely unpredictable. And its that uncertainty that needs to be addressed, not whether or not nuclear can be made safe under current paradigms. If it can never be made entirely safe, why would we burden future generations with our need for electric shavers and all the rest.

Respectfully, "the future is entirely unpredictable, and that uncertainty needs to be addressed" assumes that we might somehow be able to make the future predictable? I doubt that was what you meant.

In the same vein you said, "If there is a world calamity ... a nuke plant is a disaster waiting to happen." Is a disaster on top of a calamity worse than the calamity?

Unfortunately, I do not know how to make the future predicatable or to prevent furure calamities. I do know that 7 Billion people cannot be sustained on this Earth without technology and a stable society. Providing safe and reliable energy is essential for preserving that stability. Right now I do not think we have any other alternative than to include nuclear power in the mix of energy sources.

 

[nikkkom]

Just a partial answer. On (a) the latest reports revealed that not only EDGs were flooded, but the essential AC and DC electrical panels as well in some of the plants. That may have explained why even some DC systems or lighting failed.

Interesting.

I though "battery-backed emergency lighting", when used in the context of nuclear power plants, means lighting *integrated with battery*. Maybe even the lamp and battery in an air- and water-tight unit. With photodiode detector which switches it on automatically when it detects darkness. You know, something designed to be fail-safe.

How naive I was...

 

[NUCENG]

You have a point there. However, I was not thinking so much of the experiences we have had so far (the number of which is fortunately very limited), but rather the design bases of the containments. If you don't have large enough volume to accommodate all hydrogen produced by cladding oxidation, a full meltdown will probably result into a release. And if you don't have filters in the vent line, you will probably have a rather large release (and even if you have filters, they will not be able to catch noble gases or organic iodine, unless it's a large dry bed instead of the more compact wet scrubber type).

If you don't have a core catcher, and your containment does not allow for flooding of the drywell in case of melt-through (either due to the pools sitting lower than the drywell or due to fear of steam explosions), you have difficulty controlling the core-concrete interaction, which may result into a containment failure.

Etc. My point was simply that if a full-scale meltdown is not included in the original design basis of the containment, it's difficult to prove it can prevent release in 99 % of the cases, which would be a plausible target for new reactor designs.

I understand, and agree in general that existing plants may not be the best design for safety. So I work to ensure that their operation as as low risk as I can provide. I would prefer to see new designed plants with all their safety advances being built so we can retire the older designs. I would hope that advances to intelligent grid design to increase the potential sor reliable addition of wind and solar generation sources. And I hope Miss America finally gets world peace. We only fail if we quit trying.

 

[jmelson]

There has never been a nuclear accident in any US Naval Nuclear Propulsion Plant or prototype.

Are you sure about that? There was a serious accident that cost 3 lives and destroyed a
reactor at Idaho National Engineering Lab in, I believe, 1958. I believe this was a prototype
of a Naval power reactor. The fuel was nearly spent and due for exchange, and therefore the
reactor was very touchy. An operator was apparently lifting a control rod to attach it to the control
rod drive after an unattended shutdown. It was sticking, and he lifted it too far, causing a rapid
power excursion and exploding the RPV. The three operators in the facility were burned by radioactive steam and died. This should be a fairly well-known accident.

Jon

 

[nikkkom]

Are you sure about that? There was a serious accident that cost 3 lives and destroyed a
reactor at Idaho National Engineering Lab in, I believe, 1958. I believe this was a prototype
of a Naval power reactor. The fuel was nearly spent and due for exchange, and therefore the
reactor was very touchy. An operator was apparently lifting a control rod to attach it to the control
rod drive after an unattended shutdown. It was sticking, and he lifted it too far, causing a rapid
power excursion and exploding the RPV. The three operators in the facility were burned by radioactive steam and died. This should be a fairly well-known accident.

http://en.wikipedia.org/wiki/SL-1

It wasn't a Navy program. It was an Army program.

 

[westfield]

I am open minded on the cause of damage on Unit 4.

Initially I received information that operators believed a second explosion had occurred in Unit 3. Other theories were of steam explosions, which I never found convincing. We basically rehjected that theory because we couldn't find photographic changes in unit 3 indicating a second explosion. Then the possibility of hydrogen from damaged fuel in a drained spent fuel pool was proposed based on NRC statements that the pool was empty. That was proved wrong by photos showing no significant damage. For a while people were looking for welding gases supporting the shroud chane project or lubricating oils as sources for the explosion.

The next theory was radiolysis of water in the spent fuel pool. Calculations were made that showed that was possible if the pool was boiling. There was some good work on this by other posters.

Then TEPCO postulated the Unit 3 source via the stack piping. Apparently that has gained credence by the photos and inspections of the debris on the 3rd and 4th floors. It is relatively easy to see a difference between an explosion inside ducting and ducting that has benn crushed or damaged from an exterior explosion. The isometric sketches of the SBGT ducting seems consistent. We don't really know when the exterior duct failed on the side of unit 3. Recent information confirms the dampers fail open and there are no backdraft damper. The explosion of unit 3 could have followed a period when the hydrogen was present with increasing hydrogen concentrations and pressure forcing hydrogen into unit 4 or the explosion itself may have been the driving force. The explosion may not have been propagated to unit 4 because the hydrogen concentration in the ducting was to rich for deflagration or detonation. The timelag before the Unit 4 explosion could have been awaiting an ignition source or dilution to a combustible or explosive mixture.

In summary I still have unanswered questions. to change the maybes into facts. If I have to answer your question, I will default to "Mythbusters" terminology and say it is somewhere neither BUSTED, nor CONFIRMED, but somewhere between POSSIBLE, and PLAUSIBLE.

NUCENG, I understand large (main) generators are cooled using hydrogen gas circulated through the windings. Would you or anyone with NPP generator knowledge care to comment on this hydrogen system being a possible source of Unit #4's hydrogen buildup?

Apart from the hydrogen that is circulated through the generator while its running there would also be hydrogen generation systems and\or bottled hydrogen on-site to provide the initial charge of hydrogen on start-up and then "make up" while the generator is running.

I realize that Unit #4 was not running and the generator casing would presumably be inerted however that still leaves the hydrogen generation system or "bottled" hydrogen somewhere onsite. I wish I could find a drawing which indicates where this is located. One would tend to think if it's anywhere inside of Unit #4 it would be in the Turbine building however one would not normally expect the EDG's to be located where they are at fuku ichici so I for one wouldn't be surprised if the generator cooling hydrogen system is somewhere "surprising" as well.

Edit : I guess without knowledge of the actual location of the main generator cooling hydrogen at fuku-ichici Unit #4 we are in the dark. FWIW, on the Oyster Creek Turbine Building general layout drawings there are hydrogen gas bottles shown in the TB loading dock. That location would seem to eliminate that hydrogen as a possible source leaking into the RB.
Again, having some drawings of the fukushima plant would be rather handy in these discussions.

 

[dezzert]

NUCENG, thank you very much for that response. I truly appreciate it.

Then TEPCO postulated the Unit 3 source via the stack piping. Apparently that has gained credence by the photos and inspections of the debris on the 3rd and 4th floors. It is relatively easy to see a difference between an explosion inside ducting and ducting that has benn crushed or damaged from an exterior explosion. The isometric sketches of the SBGT ducting seems consistent.

Yes, but could the exhaust system pick up emissions from lower in the building and not from the SGTS. The reason I ask this is because of the pulse/explosion that is believed to have occurred in R2 at the same time as the R4 blast, and because of the damage to the SGTS valve in the basement of R2 after the R3 blast. Schematics of the plant show an extensive tunnel system (both piping and electrical) connecting numerous points within the R1 to R4 compound. Studying the R3 blast extensively there appear to be numerous expulsions, cloud bursts, emanating from the switching yard up to 12 seconds after the main pulse from R3. Could R3s explosion have blown open this tunneling system allowing communication between the reactors underground.

We don't really know when the exterior duct failed on the side of unit 3.

With only the DigitalGlobe sat photos to go by that's going to be hard to determine, but Id have to say from the looks of the exhaust line from R3 after the blast, Id say its likely at the same time.

Recent information confirms the dampers fail open and there are no backdraft damper. The explosion of unit 3 could have followed a period when the hydrogen was present with increasing hydrogen concentrations and pressure forcing hydrogen into unit 4 or the explosion itself may have been the driving force. The explosion may not have been propagated to unit 4 because the hydrogen concentration in the ducting was to rich for deflagration or detonation. The timelag before the Unit 4 explosion could have been awaiting an ignition source or dilution to a combustible or explosive mixture.

Like you I include possible to this scenario but then go the other way to not probable. Knee jerk reaction. The only possibility to me is if the R3 blast blew the valves shut.

 

[dezzert]

Unfortunately, I do not know how to make the future predicatable or to prevent furure calamities. I do know that 7 Billion people cannot be sustained on this Earth without technology and a stable society. Providing safe and reliable energy is essential for preserving that stability. Right now I do not think we have any other alternative than to include nuclear power in the mix of energy sources.

In the early eighties, peak winter, I visited a geek friend in the mountains of southern Mendocino Co. California for a week. He built a beautiful house with every inch of roof covered with solar panels, and not far away, a wind generator all hooked to a huge battery collection for electricity. For hot water he had panels on the southside below the house and a water line connected to the back of his wood stove feeding a large heat tank in the attic. For cooking he had both a wood and gas stove, but in the winter only uses the gas side for hot coffee water in the morning. He also had a back up nat gas generator and nat gas on demand water heater, which again were seldom used. For cooling his house in the summer, he had a 2 ft pipe that ran from a group of trees, 6 feet underground, and into his house. He said it worked unbelievably well and I believe him.

During my stay there was a massive storm that knocked out the grid throughout the northern bay area into his area. That morning, while drinking a cup of coffee, I watched his good enough sized (24"?) TV picking up the bay area stations via antenna, talking about the blackout. As I sat there, listening to his son play music on his stereo upstairs, and my friend taking a hot bath that was steaming up the bathroom, and watching flooding scenes in downtown Santa Rosa, I had an epiphany. This was the future.

Now we need to actually make it the future.

 

[jmelson]

http://en.wikipedia.org/wiki/SL-1

It wasn't a Navy program. It was an Army program.

Yup, apparently so, although they did train some Navy people at the same site.
Well, I remembered most of the details without too much error.

Jon

 

[jmelson]

NUCENG, I understand large (main) generators are cooled using hydrogen gas circulated through the windings. Would you or anyone with NPP generator knowledge care to comment on this hydrogen system being a possible source of Unit #4's hydrogen buildup?

Well, that would have been in the turbine building, not the reactor building. There have been some alternator hydrogen fires in the US, but I haven't heard of "explosions" due to the hydrogen coolant.
Of course, an earthquake can affect any system.

Jon

 

[westfield]

Well, that would have been in the turbine building, not the reactor building. There have been some alternator hydrogen fires in the US, but I haven't heard of "explosions" due to the hydrogen coolant.
Of course, an earthquake can affect any system.

Jon

Indeed that system is presumably located in the TB but considering the SGTS hydrogen scenario involves another entirely separate building, a different scenario involving an attached building doesn't seem out of the realms of possibility.

While not quite related to what we are talking about here you may be interested in this accident - http://www.powerplantforum.com/generator-auxiliary-systems/460-hydrogen-explosion-accident-u-s-lessons.html

If there are gen cooling related systems happen to be near the western end of the TB it's not a giant leap to see a potential scenario where hydrogen has leaked and instead of making its way throughout the TB it has insteadmade its way up through into the RB - this is post a major earthquake as you say. Oyster Creek drawings indicate HVAC ducting extends throughout the TB.

Thankyou for the reply.

Edit: PS, I'm not trying to sell this idea, just wanted to explore it. Didn't seem too outragous to me when the SGTS theory is the current leading one.

 

[nikkkom]

In the early eighties, peak winter, I visited a geek friend in the mountains of southern Mendocino Co. California for a week. He built a beautiful house with every inch of roof covered with solar panels,

Solar panels. Reasonably efficient. Reasonably durable. In early eighties. Really?

and not far away, a wind generator all hooked to a huge battery collection for electricity. For hot water he had panels on the southside below the house

Which he needed to not forget to drain before winter sets in. Meaning - in winter it doesn't work.

Come to think about it, where did your friend in the mountains got the clean, drinkable water from in the first place?

and a water line connected to the back of his wood stove feeding a large heat tank in the attic. For cooking he had both a wood and gas stove, but in the winter only uses the gas side for hot coffee water in the morning. He also had a back up nat gas generator and nat gas on demand water heater, which again were seldom used.

He must be enjoying everyday trips to forest for wood. Not everyone would like to do it. Not in Manhattan, for sure.

During my stay there was a massive storm that knocked out the grid throughout the northern bay area into his area. That morning, while drinking a cup of coffee, I watched his good enough sized (24"?) TV picking up the bay area stations via antenna, talking about the blackout. As I sat there, listening to his son play music on his stereo upstairs, and my friend taking a hot bath that was steaming up the bathroom, and watching flooding scenes in downtown Santa Rosa, I had an epiphany. This was the future.

Wind generator doesn't work in massive storms. Solar power is likely not available too. Unless you have a submarine-sized battery (very expensive), you can't operate TVs and stereos for long.

Heating a full bath of hot water would take helluva lot of wood. For people who need to collect that wood by hand, I bet not many would engage in such wasteful use of it (unless they are masochists).

In short, you need to stop making up stories. Of course, Internet is full of people engaging in mental masturbations of all imaginable kinds...