Converting Energy from Nuclear waste into useful energy (rendering waste harmless)?

[Icefire]

Because nuclear waste produces a fairly powerful ionizing affect, could it be possible to create a generator of some sort that will absorb the ionizing energy and convert it into something useful such as electricity or matter which has energy potential that is easier to convert?

 

We can detect that Nuclear waste has a significant amount of energy, so we should be able to convert it into something useful in a large enough amount to power even a city (with enough waste).

this could also cause the waste to lose it's radioactivity, making it easier to recycle.

[swansont]

The ionizing radiation that actually escapes from a pile of radioactive waste is actually a small fraction of the energy released.

[Icefire]

or whatever is the majority of the energy, I really don't know. But if we can measure it and it's influences we should be able to convert it with the right technology.

[swansont]

You would need a certain amount of it to have it be hot enough to boil water and turn a turbine. But you couldn't easily shut it down, so that's not safe. If you have less material and it's cooler, then your efficiency is lower; you would have to rely on a technology like a thermoelectric generator. It's probably not economically viable.

[Externet]

Interesting subject, but am ignorant in this matters, please shine some light.

 

For sure there is a bunch of brains dealing with the disposal of spent nuclear material, because of health and political and other reasons, but swansont triggers my curiousity.

 

..." would need a certain amount of it to have it be hot enough to boil water and"...

 

What does less than a certain amount of spent material does ? Just warms up to say 60C instead of being capable of boiling water ?

 

If such spent material is encapsulated in glass, concrete, shielded in a whatever metal box that fully blocks all harmful radiation; what does it do? Gets warm by itself for a buuuunch of years?

 

I would not mind having such safe hot box instead of my fireplace, or place it in a water filled vessel to make hot water. Just move it out to the backyard in summer.

 

Ok, spank me now...

[swansont]

The drawback of that hot box that's generating a few tens of watts is the fraction of a percent of high-energy photon energy that escapes.

 

If they are MeV-ish photons, a few milliWatts is 1 Curie of radiation, which is going to give you a dose rate measured in rem/hour inside a meter away.

 

http://web.princeton.edu/sites/ehs/radsafeguide/rsg_app_f.htm

[Mr Skeptic]

A major problem with the waste is that it has all kinds of different isotopes of different elements. It's pretty much a pile of random chemicals that emit various types of radiation. You get gases, solids, and water soluble junk which makes containment difficult. A bit of neutron generation can make materials in your machine brittle and radioactive, and various of the chemicals in the waste will be corrosive.

 

The easiest way to use it would be as swansont said, put it all in a big box and use it to boil water for a turbine. However, if you are generating enough heat to boil water, you also are almost guaranteed to be generating too much heat for air cooling and the whole thing could melt into a molten pile of lawsuits. Remember, there is no shutoff switch, nor will it somehow stop producing heat when it gets too hot.

[Externet]

Thanks, swansont, skeptic.

 

How does the canisters to store spent fuel prevent the personnel/environment handling them from becoming ill/contaminated/suffer health problems ?

I assume their well designed and very tested casks fully shield/contain the harmful radiation but not its heat. Whatever isotopes or chemicals mixture is inside, is kept very confined

If so, the heat could be used.

 

And when recently removed from service, spent fuel rods rest in water a while to "prevent radiation from harming nuclear plant personnel"

A water jacket added in the "fireplace-replacing hot box" could work too, could it?

 

From reading on the net, they emit heat for years. There has to be a way, setting aside current security matters, to implement its use.

 

Or centralized sites pumping hot water to dwellings ?

 

http://phobos.vscht.cz/konference_matlab/MATLAB06/prispevky/pultarova/pultarova.pdf

http://www.ocrwm.doe.gov/factsheets/doeymp0338.shtml

 

WANTED : "Safe hot box containing spent nuclear material"

( A couple of kilowatts heat for 20 years will do it, fireplace size preferred )

[insane_alien]

and then there is the lifetime of the isotopes. the short lived ones don't hang around long enough for constant power production and the long lived ones would need tonnes per milliwatt. there are a few medium life times that are suitible but still not a very good way of doing it.

 

eitherway, to generate a reasonable amount of power you'll need to shield against an unreasonable amount of radiation. and then there are scale issues and fuel production issues and disposal issues and maintenance issues.

 

if you just dump it all down a mineshaft and hope to generate power off it then its going to go horribly horribly wrong.

[Externet]

OK, I will settle for 300Kg; 10 years. Got any spent fuel behind your spider webs ?

 

"After one year, typical spent nuclear fuel generates about 10 kW of decay heat per tonne, decreasing to about 1 kW/t after ten years.[2] Hence effective passive cooling for spent nuclear fuel is required for a number of years."

( from ---> http://en.wikipedia.org/wiki/Decay_heat )

 

http://en.wikipedia.org/wiki/Radioisotope_heater_unit

[insane_alien]

exactly look at that, 10kW a tonne. that means for a decent sized station you need 1000000 tonnes of waste. thats more waste than we actually produce. and even then thats fresh waste to produce the same power with 10 year old waste you need 1000000 tonnes.

 

we simply don't produce enough waste for this to be viable even on a materials basis discounting shielding which will need to be excessive.

[Externet]

I do not care for a decent sized station nor making electricity.

I just want to know if could heat one home in winters, and I will not charge anyone for 10 years storage of the spent fuel. Then they can have it back.

Edited March 1, 2010 by Externet

[Icefire]

i was thinking also that if the waste is ground up into dust, it would release the energy quicker.

a refinery would have a shielded tank where the stuff is kept, then there would be a metering system that would release packets of the dust at a constant rate to control the rate of the heating/whatever.

also, would a generator relying on the thermoelectric effect instead of boiling water be more efficient? (assuming it works in real life)

[Mr Skeptic]

i was thinking also that if the waste is ground up into dust, it would release the energy quicker.

 

Nope, this would only help if it were a chemical reaction. Surface area is irrelevant to radioactive decay.

[Radical Edward]

Nope, this would only help if it were a chemical reaction. Surface area is irrelevant to radioactive decay.

 

it can be. That's why things blow up; because there is too little surface area (in the case of nuclear bombs, intentionally so. In the case of chernobyl or the Demon Core, not so much.

 

One possibility is the use of Radioisotope Thermoelectric Generators:

 

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator.

 

 

The problem with nuclear waste is the often very complicated series of waste products. Some are metals, some are metals, some are not, some are solids, liquids or gasses at room temperature (or whatever your operating temperature would be).

 

Then there is the issue of moderation. You do not want to be outputting the same amount of power all the time, and so you can moderate the reaction with control rods (or lower the fuel rods in and out of a moderator), but then as impurities build up, the rates of fission can change dramatically if your initial fuel source is not in equilibrium with all its daugther products.

 

here enters my speculation; I'm not a nuclear physicist. I do not represent any nuclear regulation bodies. Any experiments that you perform on my speculative ideas are your responsibility, and I will not be held liable for any accidental nuclear meltdowns/radiation incidents that you might cause....

 

Coming up with an "equilibrium source" and using that to just heat things that power a generator (mineral oils are usually used instead of water) might be a possibility - remember boiling temperature is just a function of pressure, so if your system pressure is low enough, then the boiling temperature is lower and you can drive turbines without requiring your source to be hundreds of degrees in temperature.

[swansont]

it can be. That's why things blow up; because there is too little surface area (in the case of nuclear bombs, intentionally so. In the case of chernobyl or the Demon Core, not so much.

 

Fusion and neutron-induced fission are not spontaneous reactions, i.e. they do not fall under the same category as decay.

 

One possibility is the use of Radioisotope Thermoelectric Generators:

 

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator.

I mentioned these earlier. One big problem, which is why I said they are probably not economically viable, is

 

efficiencies above 10% have never been achieved and most RTGs have efficiencies between 3-7%

 

So at least a kiloWatt of thermal energy is going to be needed to run a 100W light bulb.

[Icefire]

Fusion and neutron-induced fission are not spontaneous reactions, i.e. they do not fall under the same category as decay.

 

 

I mentioned these earlier. One big problem, which is why I said they are probably not economically viable, is

 

efficiencies above 10% have never been achieved and most RTGs have efficiencies between 3-7%

 

So at least a kiloWatt of thermal energy is going to be needed to run a 100W light bulb.

 

But it works, and the process can be refined with more research.

[swansont]

But it works, and the process can be refined with more research.

 

FYI, the Seebeck effect was discovered in 1821. It's not like there hasn't been research and refinement already.

[Radical Edward]

Fusion and neutron-induced fission are not spontaneous reactions, i.e. they do not fall under the same category as decay.

 

what has fusion got to do with this? And yes, I know it is not the same thing as decay, but my point was to illustrate that the amount of energy released can be adjusted by appropriate shaping of the nuclear material in some cases.

[swansont]

what has fusion got to do with this? And yes, I know it is not the same thing as decay, but my point was to illustrate that the amount of energy released can be adjusted by appropriate shaping of the nuclear material in some cases.

 

You mentioned nuclear bombs and Chernobyl. Fusion and fission, not spontaneous decay.