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Fukushima Daiichi nuclear disaster

Barking_Mad

Barking_Mad

Non sibi sed omnibus
Fingers, toes and all appendages crossed...

According to Kyodo news, the operator of the Fukushima No. 1 nuclear plant in northeast Japan has reported an abnormality after today's earthquake, the industry ministry said. The system to cool reactor cores in case of emergency stopped at the No. 1 and No. 2 reactors of the plant, which is run by Tokyo Electric Power, Kyodo quoted the ministry as saying.
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from sky news "Japan Government official: unable to pump water to cool down reactor at nuclear plant"
 
aqua said:
4.5 quake has hit hawaii - the news is reporting 4 nuclear installations shut down ok - hasn't said anything about the others yet :(
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Conflicting & confused repoerts at this time (as you would expect) from one nuclear reactor saying a cooling process is not going as planned. So no panic but that sounds like something I hope gets sorted quickly.
 
and now

Japan issues state of emergency at nuclear power plant following failure of cooling system; no radiation leak reported.

so yep, not going to plan sounds about right!
 
aqua said:
and now

Japan issues state of emergency at nuclear power plant following failure of cooling system; no radiation leak reported.

so yep, not going to plan sounds about right!
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I guess any problem at a nuclear facility triggers an state of emergency - a refinery going up is one thing but this is a bit different.

BM, I've seen those pictures - that first one, the sense of scale! Looks like a model, rather than real houses...
 
they've asked people to evacuate

Kyodo News Agency says 2,000 residents near Fukushima nuclear plant urged to evacuate.
half a minute ago via SkyNews Alerts - Breaking

can't see anything else yet though
 
The evacuation is most likely a response to the coolant problem. There may have been damage to the moderating rods that is preventing them being fully inserted into the pile, but otherwise its perhaps most likely that the reactor has been shut but cant dump excess heat.
 
...
People within 2km of the Fukushima nuclear plant have been told to evacuate as a precaution against radioactive leakage from the reactor, which is subject to a state of emergency, Sankei reports (Japanese link). The authorities said earlier there has been no radiation link from the plant but it has a problem with its cooling system.
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A fire at the Onagawa nuclear plant has been extinguished, according to the International Atomic Energy Agency. Note: this is not the plant in respect of which a state of emergency was issued because of problems with its cooling system.
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Gruan
 
form the wiki page:

After the March 11, 2011 earthquake, NHK Broadcasting reported that all six reactors shut down automatically, but that electrical problems prevented all cooling pumps for reactor #1 from functioning. Because cooling pumps are needed to reduce residual reactor heat, a nuclear emergency was declared. Under Japanese law, a nuclear emergency must be declared if there is a release of radiation, if there is a dangerous level of water in the reactor, or if the cooling mechanisms fail. However, there is no evidence of any radiation being released At 12.37 2000 residents living within a 2km radius were ordered to evacuate.
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From here:

# Core uncovery. In the event of a transient, upset, emergency, or limiting fault, LWRs are designed to automatically SCRAM (a SCRAM being the immediate and full insertion of all control rods) and spin up the ECCS. This greatly reduces reactor thermal power (but does not remove it completely); this delays core "uncovery", which is defined as the point when the fuel rods are no longer covered by coolant and can begin to heat up. As Kuan states: "In a small-break LOCA with no emergency core coolant injection, core uncovery generally begins approximately an hour after the initiation of the break. If the reactor coolant pumps are not running, the upper part of the core will be exposed to a steam environment and heatup of the core will begin. However, if the coolant pumps are running, the core will be cooled by a two-phase mixture of steam and water, and heatup of the fuel rods will be delayed until almost all of the water in the two-phase mixture is vaporized. The TMI-2 accident showed that operation of reactor coolant pumps may be sustained for up to approximately two hours to deliver a two phase mixture that can prevent core heatup."[6]
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Not sure im understanding this properly, anyone help?!
 
Barking_Mad said:
From here:



Not sure im understanding this properly, anyone help?!
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When there is no coolant running the reactor will steadily boil off its coolant exposing the pile. When the pile is exposed it can get very warm even though the reactor is no longer creating new reactive material, the already created material is still generating heat.
 
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