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8.9 earthquake in Japan: tsunami warnings

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turbo
#163
Mar12-11, 05:23 PM
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Quote Quote by Ivan Seeking View Post
I think there is far too much fear mongering towards CNN. They no sooner announced the "official release" from the Nuclear Agency than they had Japan's ambassador in front of the camera, who was downplaying the report. So let's stop the anti-cnn hype please. If you didn't watch the report then you have no business commenting.
The CNN "experts" apparently had no data on core temperatures, core cooling levels, flows, etc. I'm not saying that there is not a threat, just that reporting and grading threats with NO specifics is dangerous. The US needs to have nuclear power on-deck (IMO) in order to supply our energy needs, and we need to have relative risks and strengths of that industry presented fairly.
Ivan Seeking
#164
Mar12-11, 05:26 PM
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Quote Quote by turbo-1 View Post
The CNN "experts" apparently had no data on core temperatures, core cooling levels, flows, etc. I'm not saying that there is not a threat, just that reporting and grading threats with NO specifics is dangerous. The US needs to have nuclear power on-deck (IMO) in order to supply our energy needs, and we need to have relative risks and strengths of that industry presented fairly.
Just stay on topic please, for a change! It was an official report from Japan's Nuclear Regulatory Agency. This is not a thread about CNN.
Jimmy Snyder
#165
Mar12-11, 05:31 PM
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Quote Quote by Borek View Post
From what I understand that's not the source of the problem. Reactor has been shut down, but there is enough short living isotopes in it to create excess heat that has to be dealt with. That's expected and not surprising, just their backup cooling systems failed.
But now they're talking about a partial meltdown. That would mean the fuel rods are still in there wouldn't it?
OmCheeto
#166
Mar12-11, 05:34 PM
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Quote Quote by Jimmy Snyder View Post
I haven't read all the posts in this thread so please be patient with me if this question has already been asked. Soon after the tsunami hit, I started hearing reports that the cooling system and all of its backups in one of the nuclear reactors had failed. In the following hours the situation grew worse. My question is, why can't they just pull all of the rods out of the reactor and separate them so that the nuclear fissioning dies out?
Readers Digest version of how reactors work:

1. The rods being pulled out increase reactor power
2. The rods were all inserted during the earthquake, shutting down the reactor
3. The by-products of splitting Uranium are radioactive, ie, decay over time, releasing energy
4. These radionuclides are what are keeping the reactor hot.
5. It will take several days before these radionuclides have decayed to the point where forced cooling in not required to keep everything from melting.

My solution to the problem would have been to start up one of the other 3 reactors to provide power to the damaged ones. Unless of course, independence was not designed into the plant.
lisab
#167
Mar12-11, 05:36 PM
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Quote Quote by Jimmy Snyder View Post
But now they're talking about a partial meltdown. That would mean the fuel rods are still in there wouldn't it?
That was exactly what I was wondering. I read that they had successfully achieved a SCRAM, but I've been reading about this from so many sources I can't remember exactly where I read that.
OmCheeto
#168
Mar12-11, 05:37 PM
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Quote Quote by Jimmy Snyder View Post
But now they're talking about a partial meltdown. That would mean the fuel rods are still in there wouldn't it?
Eek!

Yes. The fuel rods are still in there. I read "rods" as control rods.

But the entire system is under tremendous pressure. To remove anything would depressurize the entire system. Doing this would ensure meltdown.
Jimmy Snyder
#169
Mar12-11, 05:39 PM
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Quote Quote by OmCheeto View Post
Readers Digest version of how reactors work:

1. The rods being pulled out increase reactor power
2. The rods were all inserted during the earthquake, shutting down the reactor
3. The by-products of splitting Uranium are radioactive, ie, decay over time, releasing energy
4. These radionuclides are what are keeping the reactor hot.
5. It will take several days before these radionuclides have decayed to the point where forced cooling in not required to keep everything from melting.

My solution to the problem would have been to start up one of the other 3 reactors to provide power to the damaged ones. Unless of course, independence was not designed into the plant.
Sorry, my knowledge of nuclear reactors and the vocabulary is not all that good. I meant pull the fuel out of the reactor so that they would stop reacting. Then separate them from each other or put them in lead envelopes so they can't react with each other.
Lacy33
#170
Mar12-11, 05:51 PM
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Is this all coming from the Large Print Version of Readers Digest because I can't see well when I am screaming and crying?
hypatia
#171
Mar12-11, 05:54 PM
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Ivan, my gut feeling is that the ambassador is not disclosing all he knows. He seemed to be trying to change the subject, while remaining calm.
OmCheeto
#172
Mar12-11, 05:59 PM
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Quote Quote by Jimmy Snyder View Post
Sorry, my knowledge of nuclear reactors and the vocabulary is not all that good. I meant pull the fuel out of the reactor so that they would stop reacting. Then separate them from each other or put them in lead envelopes so they can't react with each other.
I don't know what the radiation levels are at the moment around the pressure vessel. But it is my guess that it would be suicide for anyone to attempt such a feat, in such a short time.

Astro has much more knowledge of industrial sized reactors. I'm more familiar with tiny ones that run boats. And we didn't do a re-fueling during the overhaul, so I don't know how many people would be involved.

As I said before, they just need to get power to the cooling pumps.
Lacy33
#173
Mar12-11, 06:03 PM
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Quote Quote by hypatia View Post
Ivan, my gut feeling is that the ambassador is not disclosing all he knows. He seemed to be trying to change the subject, while remaining calm.
Well then everyone get under your desk and put your hands over the back of your neck.

btw
don't eat the oatmeal.
rootX
#174
Mar12-11, 06:05 PM
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(Meanwhile, my company is resuming its (Tokyo) business activities on Monday. There wasn't much damage. I don't know if this is true for all other companies.)
Astronuc
#175
Mar12-11, 06:23 PM
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Quote Quote by Jimmy Snyder View Post
I haven't read all the posts in this thread so please be patient with me if this question has already been asked. Soon after the tsunami hit, I started hearing reports that the cooling system and all of its backups in one of the nuclear reactors had failed. In the following hours the situation grew worse. My question is, why can't they just pull all of the rods out of the reactor and separate them so that the nuclear fissioning dies out?
The nuclear fissioning stopped when the control rods were inserted, and the reactor went subcritical.

They would normally let the core cooldown and depressurize before opening the reactor vessel, but they lost that cooling when the lost offsite power and then the emergency diesel generators quit after one hour. It would normally be a day or so before they start preparing to unload the core. But since they lost cooling, there was no cooling down of the reactor, and it would be unsafe to try and unload the core.

At shudown, the fission products are still generating heat from beta and gamma decay, and there are also some alpha-decaying transuranics. The heat is about 5 to 7% of operating power, but this quickly decays as the short-lived isotopes decay rapidly over a few days.
This provides a reasonable overview -
http://en.wikipedia.org/wiki/Decay_h...rs_in_shutdown

I would expect TEPCO and the government to very cautious about what they reveal to the public.

In theory, they should be able to determine from certain radioisotopes whether or not the fuel in the core has been breached. Xe and Kr can be present in low levels from tramp uranium, or small breaches in the cladding. If there is Cs and Sr in the coolant, that could be indicative of fuel failures. If the detect Np-239, Ce-144 and other isotopes, this is a pretty good indicator of fuel failure.


The last I heard, the plant personnel were attempting to flood the containment with seawater in order to cool the reactor.

This shows the Mark I containment (from World Nuclear Net/GE) -
http://a4.sphotos.ak.fbcdn.net/hphot..._4177387_n.jpg

The will try to get water into the core which is inside the pressure vessel. I don't have any information on the integrity of the containment or the primary system, so I don't know if any of the recirculation piping has been ruptured. The steamlines go out of the upper portion of the reactor vessel, but steam line valves isolate the primary side from the turbines when the plant is shutdown.
Jimmy Snyder
#176
Mar12-11, 06:39 PM
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Quote Quote by Astronuc View Post
They would normally let the core cooldown and depressurize before opening the reactor vessel, but they lost that cooling when the lost offsite power and then the emergency diesel generators quit after one hour. It would normally be a day or so before they start preparing to unload the core. But since they lost cooling, there was no cooling down of the reactor, and it would be unsafe to try and unload the core.
Thanks Astronuc, this explaination satisfies me.
jhae2.718
#177
Mar12-11, 06:44 PM
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Thanks for all the explanations, Astro. My knowledge of nuclear engineering is lacking, to say the least.
DevilsAvocado
#178
Mar12-11, 06:50 PM
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Quote Quote by Astronuc View Post
The last I heard, the plant personnel were attempting to flood the containment with seawater in order to cool the reactor.
Yup:

http://www.tepco.co.jp/en/press/corp...1031301-e.html

All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.

Unit 1(Shut down)
- Reactor has been shut down. However, the unit is under inspection due to
the explosive sound and white smoke that was confirmed after the big
quake occurred at 3:36PM.
- We have been injecting sea water and boric acid which absorbs neutron
into the reactor core.
rhody
#179
Mar12-11, 06:52 PM
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Astro, thanks for clarifying things,

My next concern is how they will get power restored even partially with 40% of the plants not functioning, there are 6 total and 2 appear to be kaput. The others need to be inspected for damage, and repaired as soon as possible if it is safe to do so. Does anyone know what percentage of power these five reactors provide to the city and grid it was designed to serve ? Can power from other plants be rerouted to take up the slack once power is restored to what inhabitable structures remain ?

Finally, Astro, does the US possess fuel rod technology that can in the absence of cooling water with the control rods inserted, or in the absence of control rods and cooling water to them entirely self arrest so to speak, shutting themselves down ? I was under the impression these was, please correct me if I am mistaken.

Thanks...

Rhody...
nismaratwork
#180
Mar12-11, 06:56 PM
P: 2,284
Quote Quote by Astronuc View Post
The nuclear fissioning stopped when the control rods were inserted, and the reactor went subcritical.

They would normally let the core cooldown and depressurize before opening the reactor vessel, but they lost that cooling when the lost offsite power and then the emergency diesel generators quit after one hour. It would normally be a day or so before they start preparing to unload the core. But since they lost cooling, there was no cooling down of the reactor, and it would be unsafe to try and unload the core.

At shudown, the fission products are still generating heat from beta and gamma decay, and there are also some alpha-decaying transuranics. The heat is about 5 to 7% of operating power, but this quickly decays as the short-lived isotopes decay rapidly over a few days.
This provides a reasonable overview -
http://en.wikipedia.org/wiki/Decay_h...rs_in_shutdown

I would expect TEPCO and the government to very cautious about what they reveal to the public.

In theory, they should be able to determine from certain radioisotopes whether or not the fuel in the core has been breached. Xe and Kr can be present in low levels from tramp uranium, or small breaches in the cladding. If there is Cs and Sr in the coolant, that could be indicative of fuel failures. If the detect Np-239, Ce-144 and other isotopes, this is a pretty good indicator of fuel failure.


The last I heard, the plant personnel were attempting to flood the containment with seawater in order to cool the reactor.

This shows the Mark I containment (from World Nuclear Net/GE) -
http://a4.sphotos.ak.fbcdn.net/hphot..._4177387_n.jpg

The will try to get water into the core which is inside the pressure vessel. I don't have any information on the integrity of the containment or the primary system, so I don't know if any of the recirculation piping has been ruptured. The steamlines go out of the upper portion of the reactor vessel, but steam line valves isolate the primary side from the turbines when the plant is shutdown.
Do you have any information about the Daikishi facility?


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