Quote:
Originally Posted by Pagy
(Post 16269555)
nuclear power is UNSAFE
we should go back to COAL
it's BETTER
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I know you are being facetious but most people are not aware that fly ash from coal burning is far more radioactive/dangerous to the environment than nuclear waste :(
Quote:
Originally Posted by JoMo
(Post 16269556)
http://www.yomiuri.co.jp/photo/20110313-817987-1-L.jpg
An explosion at an earthquake-damaged nuclear plant was not caused by damage to the nuclear reactor but by a pumping system that failed as crews tried to bring the reactor's temperature down, Chief Cabinet Secretary Yukio Edano said Saturday.
The next step for workers at the Fukushima Daiichi plant will be to flood the reactor containment structure with sea water to bring the reactor's temperature down to safe levels, he said. The effort is expected to take two days.
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The damage there is just to the outer shell which is simply there to protect the containment vessel from the elements. Said vessel is designed to handle anything short of a direct hit from a nuclear bomb.
Quote:
Originally Posted by Zombie
(Post 16269608)
So here's a dumb question.
They said that the reason the cooling pumps failed was because the power to the plant was lost.
The diesel generators failed because of the tsunami.
and the battery backup's didn't last long enough, or something.
Isn't it a power generation facility? Can't they generate their own electricity to operate the pumps?
They still had a ****load of steam, couldn't they use that to power the turbines and generate electricity for themselves?
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They pull energy from the grid and when there is a loss of offsite power they go into automatic shutdown. When the reactor shuts down the turbine used to create power is completely bypassed. The fuel inside the reactor is still creating tremendous amounts of heat though (decay heat) so it is necessary for cooling to continue. Since the plant is no longer generating its own power batteries/generators are needed.
Under ideal circumstances steam builds up and is dumped into the condenser. This water is cooled and pumped back into the reactor to continue the proccess. However, the generators were damaged by the tsunami which meant the systems were not turning that steam back into coolant and pressure started building (this is what everyone was freaking out over) and needed to be vented.
It's not safe to try to harness decay heat to continue to power the plant. They were actually trying to do exactly that when the Chernobyl incident took place (chernobly/fukushima are way different designs though):
Quote:
There had been concerns that in the event of a power grid failure, external power would not have been immediately available to run the plant's cooling water pumps. Chernobyl's reactors had three backup diesel generators. Each generator required 15 seconds to start up but took 60–75 seconds to attain full speed and reach the capacity of 5.5 MW required to run one main cooling water pump.
This one-minute power gap was considered unacceptable, and it had been suggested that the mechanical energy (rotational momentum) of the steam turbine could be used to generate electricity to run the main cooling water pumps while the turbine was still spinning down. In theory, analyses indicated that this residual momentum had the potential to provide power for 45 seconds, which would bridge the power gap between the onset of the external power failure and the full availability of electric power from the emergency diesel generators.
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