Just how long does it take to cool a reactor?

[doodab]

So what about the spent fuel rods (there are an awful lot of them, far more than in all the reactors I hear). How much cooling do they need?

Apparently after a year or so it generates about 10kW per tonne.

Decay heat - Wikipedia, the free encyclopedia

[TimberWolf]

Apparently after a year or so it generates about 10kW per tonne.

Decay heat - Wikipedia, the free encyclopedia

That's a rather surprisingly benign figure, 10W/kg, with only passive cooling required. I thought some had reportedly caught fire and were becoming a real menace.

[TimberWolf]

That's a rather surprisingly benign figure, 10W/kg, with only passive cooling required. I thought some had reportedly caught fire and were becoming a real menace.

A Wiki has already been updated to say that a spent fuel pond did catch fire:

But if the pool were to be drained of water, the discharged fuel from the previous two refuelings would still be "fresh" enough to melt under decay heat. However, the zircaloy cladding of this fuel could be ignited during the heatup. The resulting fire would probably spread to most or all of the fuel in the pool. The heat of combustion, in combination with decay heat, would probably drive "borderline aged" fuel into a molten condition. Moreover, if the fire becomes oxygen-starved (quite probable for a fire located in the bottom of a pit such as this), the hot zirconium would rob oxygen from the uranium dioxide fuel, forming a liquid mixture of metallic uranium, zirconium, oxidized zirconium, and dissolved uranium dioxide. This would cause a release of fission products from the fuel matrix quite comparable to that of molten fuel. In addition, although confined, BWR spent fuel pools are almost always located outside of the primary containment. Generation of hydrogen during the process would probably result in an explosion damaging the secondary containment building. Thus, release to the atmosphere is more likely than for comparable accidents involving the reactor core. [4] A spent fuel pool accident releasing radioactive material to atmosphere happened in a Mk-1 type BWR reactor in Fukushima, Japan, on March 14, 2011.

[TimberWolf]

[PAH]

Build a sarcophagus around the damaged reactor.

We just need some very brave souls to go and build it.

Those chaps at Chernobyl were incredibly brave in their self sacrifice.

If only the japs had been more advanced with that humanoid robot stuff we had a thread on in the last week or so. Send in the robots to build it and have them seal themselves in if they get too contaminated.

They could use prisoners on day release. Send our life-sentenced scum over as part of a multinational effort. Everyone's a winner, who deserves to be.

[AtW]

AtW mentioned this proposal a day or so ago and I asked him how you'd keep the reactor cool, with something like 2GW of heat to remove. Okay, getting water down there won't be a problem under gravity feed, but you might need to be pumping a tonne or more water a second (I did a rough calculation once but have forgotten the result) 2 miles uphill. Assuming you can't cool the water underground.

Build it under ocean floor....

[MarillionFan]

Build it under ocean floor....

You are Patrick Duffy, but you can keep your £5, you need it more.

[suityou01]

Has anyone called Red Adaire?

[OwlHoot]

Build it under ocean floor....

Sorry, but that's a ridiculous idea.

There'd be too much sediment in most places. Having to shore up several thousand feet of mud would be hideously expensive and probably technically impossible.

Also, if a meltdown occurred it would seep back up through the mud and contaminate the ocean.

Far cheaper and simpler to drill into watertight basement rock (basalt or granite or something) on dry land.

[OwlHoot]

Has anyone called Red Adaire?

or failing him, Red Robbo?