Japanese nuclear reactor problems??

[mississippichem]

I just heard on NPR (sorry no link found), that some experts were considering spraying boric acid solution all over the core. I don't know a whole lot about nuclear physics but if I remember correctly [ce]^{10}B[/ce] has a large neutron capture cross section and readily captures neutrons to form [ce]^{11}B[/ce]. They believe this might help bring down the neutron population and cool down the rods. This is the same principle that is used in boron neutron capture therapy, an anti-cancer treatment.

Edited March 12, 2011 by mississippichem

[insane_alien]

eh i think that would have minimal effect. the neutron population will be low as the chain reaction is already halted.

 

soaking up residual neutrons wouldn't do much as its good old radioactive decay rather than fission keeping it warm just now.

 

as far as i'm aware, free neutron density doesn't affect it too much.

[Ludwik]

(preface: i had absolutely no clue where to put this. i considered physics,

Engineering and a couple others but decided to just guess and let mods move it if they want)

http://www.cnn.com/2...dex.html?hpt=T1

apparently a Japanese nuclear reactor's power source has been disabled by the earthquake in japan and the backup was disabled by the tsunami and now they can't cool the core

what possibility of there being a meltdown (Chernobyl like melt down) or any significant release of radionuclides from the power plant?

 

 

Below is a message just received from a nuclear physicist friend in Japan:

 

Ludwik

 

=============================================

 

 

 

 

Serious rescue efforts for isolated people in destroyed

 

towns by tsunamis and quake are under way.

 

Another serious concern is of the stopped nuclear power

 

plants, Fukushima-I $II with 8 reactors total.

 

The Fukushima-I#1, 40 years old, has got the first trouble

 

after its automatic shut-down by the quake, which was caused

 

by no electricity (an emergent Diesel generator did not work

 

either) for driving circulation pumps of cooling water.

 

Consequently, decay heat of U-fuel pins could not be cooled

 

enough and temperature and steam pressure inside the reactor

 

vessel elevated continuously. Finally the melt-down of

 

reactor-core fuel started to happen, as detected by Cs and I

 

activities outside as the emergency value of reactor vessel

 

gas was opened to decrease the elevated steam pressure. It

 

happened an explosion, by mixing hydrogen-gas (generated by

 

H2O + high-temperature-metal interaction inside reactor) and

 

oxygen gas at the outside of the reactor steel-container,

 

which destroyed the concrete walls of the #1 plant building.

 

The reactor container vessel and reactor vessel were looked

 

not damaged.

 

TEPCO (Tokyo Electric Power Corp.) and NISA (Nuclear and

 

Industrial Safety Agency) decided to fill the inside and

 

out-side of reactor vessel with sea-water adding borated

 

acid to cool the reactor. The work was done. Radioactivity

 

monitors outside showed decrease of radiation level to about

 

ten times of natural BG, which was about several 100 times

 

just after the emergency gas-valve opening. Now the reactor

 

is confined stable. Citizens inside 20 km radius were

 

evacuated for safety.

 

(I think, the usage of sea water, emergent use, was chosen

 

by two reasons: 1) not enough pure-water was not available

 

at the site, 2) NaCl contained in sea water, as well as

 

added borated acid (B-10) has significant thermal-neutron

 

absorption effect which may help avoiding a worst

 

criticality accident of fallen debris of melt U-fuels into

 

water pool of container vessel, if happened.)

 

 

 

 

Probably the Fukushima-I#1 reactor will be closed

 

(disassembled) in near future. But we still need careful

 

watching what will be going on.

 

 

 

 

Now it is aired that Fukushima-I#3 reactor has got a similar

 

trouble. They might do similar treatment, not decided yet.

 

 

 

 

.

Edited March 13, 2011 by Ludwik

[swansont]

The use of Boron is either precautionary overkill or they are worried about a restart casualty of some sort — damaged control rod (or rods) stuck so it's not fully inserted, or perhaps deformation of the fuel from heating resulting in a different geometry, as implied by what Ludwik posted. Also, introducing relatively cold seawater — cold water is more dense and does a more efficient job at thermalizing fast neutrons, so it moves you closer to criticality. And/or perhaps something else I can't think of or don't know about.

[ewmon]

Why does a power plant need external power to run itself?

Safety in redundancy, as we now realize. Like "bootstrapping" in reverse ... no power to shut itself down properly.

 

 

 

From a couple of posts:

 

basically [no] chance of a [horrific catastrophe]

And yet, the human mind has difficulties processing/comprehending the "expected value" in the extremes, especially that of horrific catastrophes that have basically no chance of happening, which is how insurance companies make very nice profits. There's obviously very little empirical data on horrific catastrophes (which is why we view them as horrific), so the "statistics" mostly come from estimates and extrapolations.

 

Not to seem sarcastic, but this is looking like it'll only be a regular nuclear catastrophe, not a horrific one.

[John Cuthber]

Good point.

So far the estimates are something like 10,000 dead of which none are due to radiation and (from what I heard on the news) 4 were due to the damage to the reactor building.

Does that mean we should have 10000/4 threads worrying about earthquakes for every thread about the reactor?

The quake and tsunami are devastating disasters that need international help. The problems with the reactor(s) are rather less important yet they seem to be the focus of attention.

 

BTW, Thanks to Ludwik for some information from someone who is actually there and qualified to comment.

[swansont]

Good article on the events

 

https://morgsatlarge.wordpress.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors/

[A Tripolation]

I'm wondering why Michio Kaku today stated on Good Morning America that there is a chance that this reactor could create a Chernobyl-like incident. When asked point blank if the scientists that were saying that the reactor wasn't going to blow up or anything, he said that they were wrong. Has anything changed or is he speaking of some "danger" that I'm currently unaware of.

 

I tried to find a link to it, but I couldn't.

[Cap'n Refsmmat]

Oh dear.

 

Now that they've poured boric acid into at least one of the reactors, I don't think it's possible for it to go prompt critical and explode like Chernobyl did. I believe the worst case now involves the spent nuclear fuel pools near the reactors -- if a hydrogen explosion launches radioactive nuclear waste into the air, Bad Things will happen.

[swansont]

I'm wondering why Michio Kaku today stated on Good Morning America that there is a chance that this reactor could create a Chernobyl-like incident. When asked point blank if the scientists that were saying that the reactor wasn't going to blow up or anything, he said that they were wrong. Has anything changed or is he speaking of some "danger" that I'm currently unaware of.

 

I tried to find a link to it, but I couldn't.

 

Kaku has a recent history of chiming in about topics he doesn't understand in his role as expert-for-the-camera. He has rapidly become irrelevant.

[jackson33]

On Sunday, TEPCO began filling the container structure with seawater which will be mixed with boric acid to prevent any elevation in nuclear reaction, the government said.[/Quote]

 

http://gulfnews.com/news/world/other-world/japan-tries-sea-water-boric-acid-to-cool-down-nuclear-reactors-1.775701

 

I'm beginning to think media is responsible for a whole lot of misconception "goin on out there". I know absolutely nothing about nuclear reactors, but I do believe if anybody does or certainly should, it would be those scientist in Japan. They are saying one thing, our media another.

 

As for saltwater being used, it's accessible, cheaper and any feeling the reactor complex can be salvaged has vanished. Additionally at some point in time (?), generated heat with out a source will begin to diminish, which should have passed. I'd also suggest, short of something else happening, the fact the main containment facilities are holding would mean something and I'm still waiting to hear WHY back up energy for cooling equipment, wasn't available after the flooding. Apparently all there reactors are designed to automatically shut down, in the event of ground movement. If true, those reactors were shut down, but properly cooling until power was lost.

[Cap'n Refsmmat]

I'd also suggest, short of something else happening, the fact the main containment facilities are holding would mean something and I'm still waiting to hear WHY back up energy for cooling equipment, wasn't available after the flooding. Apparently all there reactors are designed to automatically shut down, in the event of ground movement. If true, those reactors were shut down, but properly cooling until power was lost.

Backup energy was unavailable because of the flooding. Batteries were available, but the diesel generators had been damaged.

 

The reactors did indeed shut down. They are not running currently. Apparently the waste products are still producing significant amounts of heat.

[jackson33]

The plants have several back up diesel generators (locomotive style engines) that supply power to motor driven cooling systems that will supply high flow of water up to about 300 psig.. There are also steam driven systems to supply cooling water up to 1100 psig. There are also pressure relief systems that active at about 1100 psig. If reactor pressure gets too high, relief valves open and discharge steam to a water filled pool inside the containment....

 

Based on limited information, this is what I think might happen:

 

Earthquake hits, high vibration on the main turbine automatically trips the turbine by rapidly closing stop valves. Reactor automatically shuts down (scrams) all rods go in. Earthquake disrupts off site power to the plant and back up diesel generators should have started, maybe they did not. Main sources of water to the reactor are not available. If there is no pipe break off of the reactor, the pressure will slowly increase. After about an hour, a relief valve(1 of about 10) will open at about 1100 psig and drop pressure to about 1080. The steam is sent to a pool of water called a suppression pool in the containment that condenses the steam. This valve will cycle open and close every 5-10 minutes. Operators would use a small steam driven turbine (RCIC) to supply water at high pressure to the reactor under these circumstances for several hours. You can sit like this a long time, hot and at 1000 psig it’s no big deal as long as water covers the fuel in the reactor pressure vessel. If that turbine is not available, there is a larger steam driven turbine (HPCI) that supplies more water meant to provide make up if there was a pipe break.[/Quote]

 

http://theenergycollective.com/nathantemple/53384/how-shutdown-and-core-cooling-japanese-reactors-likely-functions

 

 

If they were shut down, because of ground movement (they were), then they were never restarted (were not), but a number of cooling procedures were in place or should have been. The above link delves into this, although I cannot verify it's authenticity. All I'm trying to say was and is, something does not make sense in my mind for either back up systems available or available power and what I read, is that there are multiple combination, that apparently failed. Keep in mind, though the link doesn't account for this, there was a time period between the ground movement (earthquake and auto shut down) and the tsunami (damaging of equipment).

[swansont]

If they were shut down, because of ground movement (they were), then they were never restarted (were not), but a number of cooling procedures were in place or should have been. The above link delves into this, although I cannot verify it's authenticity. All I'm trying to say was and is, something does not make sense in my mind for either back up systems available or available power and what I read, is that there are multiple combination, that apparently failed. Keep in mind, though the link doesn't account for this, there was a time period between the ground movement (earthquake and auto shut down) and the tsunami (damaging of equipment).

 

That period of time between shutdown and the tsunami taking out the primary and backup power sources was short. The best timeline I can find shows that they reported a loss of generator power within an hour of the earthquake.

http://www.bbc.co.uk/news/science-environment-12722719

 

So the reactor would not have cooled off much in that time. The battery backup was rated to last for 8 hours. After that, you need someone to bring in a portable generator from off-site.

 

Additionally at some point in time (?), generated heat with out a source will begin to diminish, which should have passed.

 

The radioactive fission products continue to be a source of a significant amount of heat.

[jackson33]

When a nuclear reactor has been shut down, and nuclear fission is not occurring at a large scale, the major source of heat production will be due to the beta decay of these fission fragments. For this reason, at the moment of reactor shutdown, decay heat will be about 7% of the previous core power if the reactor has had a long and steady power history. About 1 hour after shutdown, the decay heat will be about 1.5% of the previous core power. After a day, the decay heat falls to 0.4%, and after a week it will be only 0.2%. The decay heat production rate will continue to slowly decrease over time; the decay curve depends upon the proportions of the various fission products in the core and upon their respective half-lives[2]. An approximation for the decay heat curve valid from 10 seconds to 100 days after shutdown is...[/Quote]

 

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

 

swansont; Nuclear Reactors are shut down all the time for a variety of reasons. In assuming all eleven that did so in Japan, naturally shut down (for cause), this in itself was nothing unusual. I understand when the tsunami had done it's damage, natural procedures were not possible, those handling the situation were no doubt the best and my point post 36...media is making a back page story, front page news.

 

As a passing thought from my first post this thread, I am still confused if there was/is a problem, why a back up system wasn't available if a power source failed. Since limited battery power was available, but obviously won't operate as power for a broken generator, there should have been a plan available for maintaining the cooling system, without internal power. A previous link suggested a broken pipe from the primary containment, but even that doesn't make sense to me, since as I understand it that would have caused a meltdown, exposure of core rods. Steam should have continued to forced itself through the cooling system, back to the reactor and so on.

[Cap'n Refsmmat]

Since limited battery power was available, but obviously won't operate as power for a broken generator, there should have been a plan available for maintaining the cooling system, without internal power.

Ordinarily you'd use the electrical grid, but there was a bit of a problem with that as well.

 

The sea wall around the reactors was assumed to be capable of stopping the tsunami, but the generators were on low ground and the tsunami was larger than anticipated.

[swansont]

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

 

swansont; Nuclear Reactors are shut down all the time for a variety of reasons. In assuming all eleven that did so in Japan, naturally shut down (for cause), this in itself was nothing unusual. I understand when the tsunami had done it's damage, natural procedures were not possible, those handling the situation were no doubt the best and my point post 36...media is making a back page story, front page news.

 

As a passing thought from my first post this thread, I am still confused if there was/is a problem, why a back up system wasn't available if a power source failed. Since limited battery power was available, but obviously won't operate as power for a broken generator, there should have been a plan available for maintaining the cooling system, without internal power. A previous link suggested a broken pipe from the primary containment, but even that doesn't make sense to me, since as I understand it that would have caused a meltdown, exposure of core rods. Steam should have continued to forced itself through the cooling system, back to the reactor and so on.

 

1.5% of operating power. You provided a link listing the reactors — reactor 1 has a rate power of 460 MW (the others that are affected are rated at 784 MW edit: those are electrical values; thermal will be about 3x greater). So decay heat was 7 MW 21 MW or more when diesel power was lost, and even now is still a few MW. That's a lot of heat.

 

The plan for operating without power was the generator.

 

I'm not sure what link implies a breach of the system; without pumps the core would uncover as the water boiled away, and they operators vented steam to ensure the pressure vessel didn't rupture. That's consistent with reports I've read. Power is needed to run pumps for cooling and also to inject water into the core.

Edited March 15, 2011 by swansont
fix power values

[jackson33]

1.5% of operating power. You provided a link listing the reactors — reactor 1 has a rate power of 460 MW (the others that are affected are rated at 784 MW). So decay heat was 7 MW or more when diesel power was lost, and even now is still a few MW. That's a lot of heat.

 

The plan for operating without power was the generator.[/Quote]

 

But it had cooled before lost power...

 

swansont; I'm picturing a larger gas/diesel power generator than I could use during a local power outage, not something that requires day's to set up and should have been readily accessible. Frankly, I think some are confusing the steam generator inside the second containment (not the primary) which were not damaged, or doesn't in itself require power. Again, not being an expert, it seems to me there is or should have been someplace short of generating power for the entire operation, to produce enough power to maintain the cooling system. I think you understand what I'm inferring. Here's a good picture diagram of a nuclear generating system, but I'm sure the ones in trouble are a little different...

 

 

http://www.ikonet.com/en/visualdictionary/energy/nuclear-energy/nuclear-generating-station.php

 

 

 

I'm not sure what link implies a breach of the system; without pumps the core would uncover as the water boiled away, and they operators vented steam to ensure the pressure vessel didn't rupture. That's consistent with reports I've read. Power is needed to run pumps for cooling and also to inject water into the core. [/Quote]

 

It doesn't matter and I may have misunderstood the cause/effect relationship, since it's obvious if a cooling, coolent pipe breaks anyplace, the end result would be loss of liquid and total exposure of the rods.

 

Nobody is contesting the highlighted, only that the source of power and I'm not sure battery power alone couldn't be directly charged and directed automatically in the event of external power failure, some very large buildings are set up this way today.

[Cap'n Refsmmat]

But it had cooled before lost power...

 

swansont; I'm picturing a larger gas/diesel power generator than I could use during a local power outage, not something that requires day's to set up and should have been readily accessible. Frankly, I think some are confusing the steam generator inside the second containment (not the primary) which were not damaged, or doesn't in itself require power. Again, not being an expert, it seems to me there is or should have been someplace short of generating power for the entire operation, to produce enough power to maintain the cooling system. I think you understand what I'm inferring. Here's a good picture diagram of a nuclear generating system, but I'm sure the ones in trouble are a little different...

Yes, and the plant had several of those diesel power generators. They were on-site. They were damaged by the tsunami. They would have been able to produce sufficient power to run the cooling system -- that is their purpose.

 

For backup power, the plants had:

 

1. Multiple redundant diesel generator systems.
2. Large batteries.
3. Access to the local electrical grid.
4. Steam turbine backup systems that used the residual heat and steam to pump more water into the reactor.

The diesel generators and local power grids were damaged in the earthquake and tsunami. The steam systems are not sufficient to cool the reactor all the way.

 

Apparently the electrical switching rooms are in the basements of the reactor buildings and flooded, making it difficult to connect new generators and power sources.

[swansont]

But it had cooled before lost power...

 

For an hour, but decay heat is continually produced. This isn't analogous to a hot casserole dish that's cooling down, this is a heating element that's plugged in; the heat source is radioactive decay. Even though the amount of thermal power generated is decreasing, it's still very large — MegaWatts. 1 MW can take a liter of water from room temperature and completely boil it away in less than 3 seconds.

 

 

swansont; I'm picturing a larger gas/diesel power generator than I could use during a local power outage, not something that requires day's to set up and should have been readily accessible. Frankly, I think some are confusing the steam generator inside the second containment (not the primary) which were not damaged, or doesn't in itself require power. Again, not being an expert, it seems to me there is or should have been someplace short of generating power for the entire operation, to produce enough power to maintain the cooling system. I think you understand what I'm inferring. Here's a good picture diagram of a nuclear generating system, but I'm sure the ones in trouble are a little different...

 

They had that. It was damaged in the tsunami.

 

For backup power, the plants had:

 

1. Multiple redundant diesel generator systems.
2. Large batteries.
3. Access to the local electrical grid.
4. Steam turbine backup systems that used the residual heat and steam to pump more water into the reactor.

The diesel generators and local power grids were damaged in the earthquake and tsunami. The steam systems are not sufficient to cool the reactor all the way.

 

Apparently the electrical switching rooms are in the basements of the reactor buildings and flooded, making it difficult to connect new generators and power sources.

 

Also, #4 still requires electricity to run the control systems. This is why the battery backup (or some other power source) is still necessary, from what I understand.

[ecoli]

The media is gonna screw over nuclear power on this one:

 

http://www.overcomingbias.com/2011/03/choose-help-or-show-concern.html

 

The Post has now given more media attention to damaged Japan nuke plants than to the entire rest of the earthquake, tsunami, etc. event. I suspect lots of media worldwide act similarly. Yet, the tsunami was vastly more harmful. As MIT’s Josef Oehmen explains, there is very little chance that many will suffer much radiation harm.

...

Here is yet another example of where people tend to choose showing concern over actually helping. Shrugging your shoulders and saying this is no big deal, that would help. Loudly expressing deep “concern,” on the other hand, hurts.

[jackson33]

Yes, and the plant had several of those diesel power generators. They were on-site. They were damaged by the tsunami. They would have been able to produce sufficient power to run the cooling system -- that is their purpose.[/Quote]

 

swansont/CP; As mentioned I do believe the Japanese have been doing all they could and are certainly more qualified than myself for a solution. I have also understood all you both say, as have been doing a great deal of reading on the subject. In short, I'm not arguing you comments but might be questioning the logic behind them...

 

If they had several and assume they were also in the basement area, it's understandable why they were damaged. However there were no doubt hundreds of others on sites where the tsunami had not damaged infrastructure and were not transferred. I'm sure there are valid reasons (too late, not expecting problems, radiation too high for humans, presumable even in suits, etc) but it appears no effort was made. I'd like to know why.

 

We now have a fifth unit that had been shut down to routine maintenance, where the cores have somehow lost there protection, adding addition meltdown fears, no different than in any of the reactors. Again, there is simply a whole lot of contradicting information coming from the media I hear and what I feel is my problem in trying to grasp a logical explanation...

 

The media is gonna screw over nuclear power on this one:[/Quote]

 

ecoli; I believe your correct, even maybe that's the flow of information is being directed by media and I certainly mean ALL media. Not often said, but those older reactors, were designed to withstand earthquakes only 1/7th the magnitude they did. Chernobyl which exploded in 1986 and could have, should have been retrofitted long before. In fact Three Mile Island DID melt down, burning through a fraction of the steel base, no one died and alls well today. In the meantime 3 Trains are missing, towns full of people are missing and the towns destroyed and media is worried about shutting down California's Nuclear Plants and curtailing any new plants. What's the president doing, Golfing....

[Cap'n Refsmmat]

If they had several and assume they were also in the basement area, it's understandable why they were damaged. However there were no doubt hundreds of others on sites where the tsunami had not damaged infrastructure and were not transferred. I'm sure there are valid reasons (too late, not expecting problems, radiation too high for humans, presumable even in suits, etc) but it appears no effort was made. I'd like to know why.

Mobile replacement generators arrived soon after the incident. As I said, the electrical switching area was in the basement and flooded, so connecting the new generators to the electrical systems was difficult.

[CharonY]

Good article on the events

 

https://morgsatlarge...clear-reactors/

 

I have no idea about the real background, but this is odd http://geniusnow.com/2011/03/15/the-strange-case-of-josef-oehmen/

[swansont]

I have no idea about the real background, but this is odd http://geniusnow.com/2011/03/15/the-strange-case-of-josef-oehmen/

 

All I can say is that of the physics I know and facts I can verify, I only had one quibble with the post, that he called control rods moderator rods. That doesn't jibe with my navy experience.