# Nuclear knowledge??



## Anvilandhammer (Apr 12, 2012)

So I have been reading around as usual and I kind of read how nuclear power plants would handle a power outage. Now a general power outage can be weathered for the usual four to eight hours without problems, but any longer than that and the backup system begins to take a hit. Correct me if I'm wrong, but if there were an emp situation, wouldn't that lead to a nuclear plant meltdown..? Hope no one lives near a blant. The meltdown radius of danger is pretty far. In my state of Michigan, there is just a small belt of safety in manistee forest on projections based on various factors. As much as I tend to keep my fighting attitude I have to say it seems like we are all Proper F'd. The US would be a radiation cesspool. Any thoughts?


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## The_Blob (Dec 24, 2008)

Actually, the opposite would happen, the plants are engineered in a 'safe mode normal' manner. Which means that the control rods are designed to engage, the pool is set to flood to max, and the valves are set to a 'closed system/no load' configuration. This is to give personnel time to correct the situation or remove the fuel (worst case scenario), eventually if nobody applies any corrections, 'bad things' will happen -- but very bad things will have had to have happened already if nobody performs these duties...

this is a VERY simplified explanation of just some of what happens.


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## Marcus (May 13, 2012)

Anvilandhammer said:


> Correct me if I'm wrong, but if there were an emp situation, wouldn't that lead to a nuclear plant meltdown..?


No, it would probably lead to a SCRAM.
http://en.wikipedia.org/wiki/Scram

A lot of folks are afraid of the China Syndrome (probably due to the movie), but such a scenario is only caused by a series of failures of equipment and personnel. Most of the systems have double or triple redundancy to prevent this and to allow components to be serviced without taking the reactor offline.


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## bacpacker (Jul 15, 2011)

It will take time, but in a total grid down scenario where no power is present to run the cooling water pumps, the water will eventually boil away and cause the melt down. That is more or less what happened in japan. They have to be cooled for a long time after shut down. Most spent fuel rods are stored in copling ponds for many years.


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## CulexPipiens (Nov 17, 2010)

bacpacker said:


> It will take time, but in a total grid down scenario where no power is present to run the cooling water pumps, the water will eventually boil away and cause the melt down. That is more or less what happened in japan. They have to be cooled for a long time after shut down. Most spent fuel rods are stored in copling ponds for many years.


Correct... from what I understand there is no such thing as an emergency shutdown... you're looking at months to cool the rods to the point that the plant can be "left alone" without eventually going into meltdown.


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## bacpacker (Jul 15, 2011)

They do have emergency shutdown procedures, which remove the fuel rods from the core to stop the actual reaction process. However the fuel rods themselves stay very hot (as in heat) for years, not months afterward. Radioactivity last much longer than that.


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## Marcus (May 13, 2012)

http://en.wikipedia.org/wiki/Nuclear_safety_systems
http://en.wikipedia.org/wiki/Boiling_water_reactor_safety_systems

I worked in the instrumentation industry before and after 3 Mile Island. I will tell you that everything is designed and tested to operate over the 40 year lifespan of a reactor (thermal, radiation, & seismic) and then deal with a LOCA.

From the second link: "At T+40, core temperature is at 650 °C (1200 °F) and rising steadily; CS and LPCI kick in and begins deluging the steam above the core, and then the core itself. First, a large amount of steam still trapped above and within the core has to be knocked down first, or the water will be flashed to steam prior to it hitting the rods. This happens after a few seconds, as the approximately 200,000 L/min (3,300 L/s, 52,500 US gal/min, 875 US gal/s) of water these systems release begin to cool first the top of the core, with LPCI deluging the fuel rods, and CS suppressing the generated steam until at approximately T+100 seconds, all of the fuel is now subject to deluge and the last remaining hot-spots at the bottom of the core are now being cooled. The peak temperature that was attained was 900 °C (1650 °F) (well below the maximum of 1200 °C (2200 °F) established by the NRC) at the bottom of the core, which was the last hot spot to be affected by the water deluge.

The core is cooled rapidly and completely, and following cooling to a reasonable temperature, below that consistent with the generation of steam, CS is shut down and LPCI is decreased in volume to a level consistent with maintenance of a steady-state temperature among the fuel rods, which will drop over a period of days due to the decrease in fission-product decay heat within the core."


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