Science Questions

If nuclear waste is hot, can it be used as an energy source?

Sat, 17th Jul 2010

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Question

Martin Kilgore asked:

If nuclear waste is hot - as I have heard - why can it not be connected to some type of heat exchanger to drive a turbine and provide energy as in a geothermal plant?

Answer

We put this question to Professor Swadesh Mahajan from the Institute for Fusion Studies at the University of Texas in Austin....

Swadesh -   Yes, it can be, but when an actinide fissions inside a nuclear reactor, it produces about 200 MEV of energy.  That means a large amount of energy in a single reaction.  Anything that you might be able to get from the geothermal thing will be about a factor of 40 to 50 less.  So it will be a tremendous wastage of the actinide energy, just to get it in the form of geothermal energy from the waste.

Chris -   And also, presumably taking into account the infrastructure you would have to plumb in in order to recover the heat from the storage materials.  It just wouldn’t be financially or from a safety perspective, viable, would it?

Swadesh -   Too little energy for that much investment.

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Because it might be hot but no longer hot enough to boil water into steam to drive a turbine. Madidus_Scientia, Fri, 9th May 2008

I _think_ it may largely be due to economical reasons.  Although it'll still produce heat, and so could still be used to generate energy, the amount of energy you could generate from it would be insufficient to justify the costs needed to do so.
LeeE, Fri, 9th May 2008

You could run water pipes from all the old Russian nuclear subs in the Arctic Circle to blocks of flats in Minsk, for instance. 'Combined Waste and Power'; that would be a nice sounding acronym. lyner, Fri, 9th May 2008

You'd really want to put a heat exchanger in the system, somewhere between the subs and the flats.  Otherwise I wouldn't fancy the chances much, for a plumber called out to fix a leaking radiator.
LeeE, Fri, 9th May 2008

Yes, and I wouldn't wear Russian underpants either, if I were you...because "Cher-nobyl fallout"...

chris, Fri, 9th May 2008

It is of course used in small power plants on satellites that have to travel into deep space where solar panels would have to be very large but it is a very expensive form of power generation.
"A General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) provides electrical power for the Pluto mission. Electricity for the Pluto New Horizons spacecraft is generated from the conversion of heat caused by the radioactive decay of plutonium in the form of plutonia (PuO2). The RTG contains 18 heat source modules, with four 151-gram plutonia pellets in each. With a total mass of plutonia at 10.9 kilograms, the RTG will provide approximately 250 watts of power at the beginning of the mission".

syhprum, Sat, 10th May 2008

Surely the waste could be used to power a stirling engine? skp, Tue, 1st Nov 2011

Used fuel is hot because only about 55 of the energy available in it has actually been used, the other 95% is still available for use, if it is reprocessed to reduce the waste products of fission from it. then you can get to around 60% of the energy out, and can blend it with depleted uranium and burn that as well. just needs to be reprocessed, which is a politically hot potato, and is not done anywhere other than Japan.

Kind of like buying a new car, and throwing it on the junkheap when the fuel tank is empty, as opening it and pouring in petrol is too much of a hassle. SeanB, Tue, 1st Nov 2011



Hi there,

I've heard that somewhere. What is the reason anyway? By recycling surely we can reduce its lethal waste. Nuclear Proliferation? I don't this is a justifiable nor logical excuse, compared to the dangers of too much nuclear waste dumpsites which could also lead to unconventional nuclear terrorism such as dirty bombs.

Btw, you mean 5%, isn't it, not 55?

Thanks, nice to meet you all. aku82, Fri, 4th Nov 2011



It would indeed give a new dimension to the word 'radiator' :p Nizzle, Fri, 4th Nov 2011

It doesn't have to be boiling hot to be a usable heat source. It just has to be accumulated into an uncomfortably big source of invading atoms and ionizing radiation to take advantage of that part of that part of it's electromagnetic emission. willyp00, Fri, 4th Nov 2011

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