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Tsunami hits north-eastern Japan after massive quake 
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jonbwfc wrote:
Worst case scenario they'll have a way to 'scram' the core. OK, I assume at this point not everyone knows how nuclear reactors work, but the quick summary is nuclear reactors work due to neutrons being emitted and absorbed in the 'fuel', which generates a lot of heat. 'Scramming' is flooding the core with something that absorbs neutrons, which stops the reaction and therefore cools the reactor. That's not what they are doing now - what they are doing now is trying to slow the reaction in a controlled way because the thing is scramming means you pretty much have to rebuild the reactor core after you do it. You're effectively writing off the core to stop it going critical. So they'll only do it if they consider the reactor to not be salvageable and in immediate danger of causing containment to fail.

As it stands, the situation is not imminently dangerous. Nuclear reactors have multiple levels of failsafes and recover systems. And the Japanese are really, REALLY careful about this stuff - much more so than the Russians or the French or us, for that matter. There is obviously still a chance of a series of catastrophic failures which could lead to a nuclear disaster but we're probably still looking at that being the least likely outcome.

For information, the reactors that are currently having problems are 'BWR' - Boiling Water Reactors

Jon

Considering that this was now a 9.0 quake the buildings coped incredibly. It is all the loose items like shelf contents that will be replaced. The buildings looked like they coped very well. It looks like the Tsunami did almost all the killing.

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Fri Mar 11, 2011 9:24 pm
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Actually, even given what I said, they've just announced they're increasing the 'evacuation zone' around the power station to 10KM. That's really not a good sign.

Jon


Fri Mar 11, 2011 9:40 pm
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It is not until you see the pictures do you realise how devastating the tsunami was.

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Fri Mar 11, 2011 11:50 pm
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Sky news are quoting a japanese news agency who are reporting that the walls and roof of one of the buildings at the Fukushima-Daiichi plant have 'been destroyed.'

BBC updates here.

Film of the actual explosion on the BBC front page.

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Sat Mar 12, 2011 8:35 am
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Holy Crap! That's one hell of an explosion! :shock:

I hope this doesn't turn into a second Chernobyl.

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Sat Mar 12, 2011 12:11 pm
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Latest update is the explosion was due to a hydrogen buildup - basically coolant water reacting with something and 'cracking', which creates hydrogen and oxygen. Which is obviously a very volatile combination. That mix came in contact with a heat source and <boom>. The explosion did not breach the reactor core.

Current winds will carry any radioactive gas/steam leak out over the pacific but they've increased the exclusion zone to 20km. Radiation levels at reactor #1 are apparently dropping.


Sat Mar 12, 2011 1:05 pm
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jonbwfc wrote:
Latest update is the explosion was due to a hydrogen buildup - basically coolant water reacting with something and 'cracking', which creates hydrogen and oxygen. Which is obviously a very volatile combination. That mix came in contact with a heat source and <boom>.

Isn't that exactly what caused the explosion at Chernobyl? I remember some people confusing a chemical hydrogen explosion with the nuclear fusion of a hydrogen bomb.

I wonder if there will be a call to decommission remaining reactors that require active cooling...

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Sat Mar 12, 2011 1:38 pm
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JJW009 wrote:
jonbwfc wrote:
Latest update is the explosion was due to a hydrogen buildup - basically coolant water reacting with something and 'cracking', which creates hydrogen and oxygen. Which is obviously a very volatile combination. That mix came in contact with a heat source and <boom>.

Isn't that exactly what caused the explosion at Chernobyl? I remember some people confusing a chemical hydrogen explosion with the nuclear fusion of a hydrogen bomb.

Yes, but the Chernobyl explosion breached the reactor vessel, exposed the graphite damping rods in the reactor core which were already at a high temperature and the exposure to air caused them to ignite, a bit like charcoal. The resultant cloud of highly radioactive smoke was what caused the larger disaster. The explosion in this case (apparently) blew the roof off the reactor building (and killed 30 people who were working to shut the reactor down :( ) but did not breach the reactor vessel, therefore the smoke cloud from it is only mildly radioactive and, as I said, it's being blown out to sea anyway.

Given that, however, they do seem to be running out of fail-safes. Presumably the reactor vessel is now in the open air and still hasn't cooled sufficiently, so if they have another explosion there's a much higher possibility of the reactor vessel being breached and them we do have a major disaster on our hands. Maybe not Chernobyl bad but still a major release of radiation.

JJW009 wrote:
I wonder if there will be a call to decommission remaining reactors that require active cooling...

I can't remember seeing a reactor design that didn't need some form of active cooling - in fact it's a bit of a misnomer as the 'cooling' is almost always 'taking energy in the form of heat from the reactor vessel and using that to generate power'. Heat transfer is a fundamental process in the design of pretty much every nuclear reactor in existence. Maybe we should start figuring one out....

Jon


Sat Mar 12, 2011 3:10 pm
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jonbwfc wrote:
Heat transfer is a fundamental process in the design of pretty much every nuclear reactor in existence. Maybe we should start figuring one out....

They already have. An "expert" on the wireless was saying that modern designs rely on natural convection rather than forced cooling to keep them at a safe temperature when they're shut down.

Obviously when they're powered up, the thermal energy is extracted and turned into electricity. However, they still produce a large amount of heat when they're shut down simply due to natural decay and this is a very particular problem. It's why they had diesel generators running the cooling, but they failed an hour into the quake.

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Sat Mar 12, 2011 4:16 pm
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JJW009 wrote:
jonbwfc wrote:
Heat transfer is a fundamental process in the design of pretty much every nuclear reactor in existence. Maybe we should start figuring one out....

They already have. An "expert" on the wireless was saying that modern designs rely on natural convection rather than forced cooling to keep them at a safe temperature when they're shut down.

That's all very well in a controlled situation but it's patently not fast enough in an emergency, as we've seen. That's why they're currently flooding the thing with seawater, which is essentially a pretty improvised method of 'forced cooling'.

JJW009 wrote:
Obviously when they're powered up, the thermal energy is extracted and turned into electricity. However, they still produce a large amount of heat when they're shut down simply due to natural decay and this is a very particular problem.

In theory that's what the damping rods are for - they absorb mobile neutrons therefore reducing the cascade and slowing decay, thereby increasing the pace of cooling. Guess in this case they weren't enough, or they had a problem with them they're not telling people about.

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It's why they had diesel generators running the cooling, but they failed an hour into the quake.

Possibly that's as long as they were expected to have to work for, given proper function of other cooling systems. The quake caused those other system to fail, leaving the generators to do the whole job and they weren't up to it. It's a bit like a UPS on a PC - they're not there to power the PC for any length of time, just long enough for it to shut down safely. They maybe didn't plan for the general situation to be so tits up that they couldn't fix things/get in a backup power supply within an hour - generally speaking you'd expect a failing nuclear reactor to be everyone's 100% top priority but it turns out that at the same time as a 10m tidal wave after force 9 earthquake, people tend to be a bit busy.

Jon


Sat Mar 12, 2011 4:59 pm
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anyone know if the sky went dark or changed a funny colour before the quake?

soon as I heard about this I knew "certain" people were going to blame that HAARP device ;(

http://www.atlanteanconspiracy.com/2011 ... haarp.html

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Sat Mar 12, 2011 5:27 pm
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It might have caused the plates to move by as much as 40m!

http://www.newscientist.com/blogs/short ... r-its.html

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Sat Mar 12, 2011 8:08 pm
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brataccas wrote:
anyone know if the sky went dark or changed a funny colour before the quake?

soon as I heard about this I knew "certain" people were going to blame that HAARP device ;(

http://www.atlanteanconspiracy.com/2011 ... haarp.html


HAARP is an Illuminati Earthquake machine used in Japan
The Truth! Really!


:?

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Sat Mar 12, 2011 8:34 pm
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did the quake happen on 3-11-2011?

interestingly close to 9-11-2001

or perhaps just another of the countless "coincidences" :(

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Sat Mar 12, 2011 9:20 pm
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JJW009 wrote:
jonbwfc wrote:
Latest update is the explosion was due to a hydrogen buildup - basically coolant water reacting with something and 'cracking', which creates hydrogen and oxygen. Which is obviously a very volatile combination. That mix came in contact with a heat source and <boom>.

Isn't that exactly what caused the explosion at Chernobyl? I remember some people confusing a chemical hydrogen explosion with the nuclear fusion of a hydrogen bomb.

Nope.

There were two explosions at Chornobyl. The first was a steam explosion caused by steam from broken fuel channels entering the core's inner working and blowing the lid off. The second explosion was, most probably, a localised nuclear power transient.

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Sat Mar 12, 2011 9:31 pm
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