Can the Natural Decay of Nuclear Waste Be Used to Generate Electricity?

Disclaimer…
I'm not to sure if I'm the first to have thought of this or not. If I aren’t I would be very interested to know whether it’s being used; or why not?
But if this idea is my own then I claim it as my own and therefore this publication is not a donation to anyone.

Idea Publication…

Hypotheses…
It’s a well known fact that if (hypothetically) you had a 100% efficient heat insulating material, and if you covered a radioactive material in it; then that material would heat up indefinitely to almost infinity (until the decay had stopped).
We don’t have a 100% efficient heat insulating material but we do have large quantities of nuclear waste which are hot due to the radioactive decay occurring within them. Currently most of this waste is put into metal lined concrete barrels and the heat within them escapes into the area around them.

My Idea…

Part 1
Component…

1. The Decay Room: Construct a well (heat insulated) tank-room. To increase its insulation it should as a useable volume and as low surface area as possible. Therefore a large sphere could be best suited.
2. The Nuclear Waste Put a large quantity of high level nuclear waste together inside this room. This does not mean that ether much (or any) nuclear fission can occur. This is because the waste itself (and its radiation) could be properly contained in the standard concrete barrels or other containment techniques typically used.
3. Water: Having (mostly) filled up The Decay Room with heat producing nuclear waste, fill any remaining space inside it with water. Due to the design requirement that The Decay Room be well heat insulated; and that it contains nuclear waste which is continuously producing its own heat; I predict that (if the right waste is used) it will not be too long until the water inside itself is boiling and suitable for producing steam for electricity generation.
4. Steam Powered Electricity Generation Apparatus (i.e. a generator, cooling circuit linked to cooling towers, whose water outflow is linked to the water inside the decay room as well as other (fairly obvious) requirements such as appropriate piping to link all).

Part 2

(Part 2 and 3 are Additional Design Notes)
1. Safety: For reasons of public and national acceptance it may be advisable to design The Decay Room so that in the event that all the water within it leaked out The Decay Room could not leak nuclear waste into the surrounding environment.
This can be achieved by Option…
a. Designing the nuclear waste containment to be able to cope with the high temperatures that would result from it being in well insulated environment that is no longer being cooled with water.
b. Building shafts of different depths (and possibly also filled with water) directly below the floor of the decay room. And creating the floor of Decay Room out a suitably relatively low melting point material such as tin, lead or aluminium. A property of these examples (or any other similar material that may be used for this purpose) is that they should not melt when The Decay Room is operating at normal temperatures (somewhat but not massively above the boiling point of water).
The intention of the above “option b” is that should The Decay Room no longer be cooled down its floor will melt and this will cause the nuclear inside The Decay Room to safely fall into the shafts of different depths beneath its floor. And because they are of different depths, and because they may even be filled with water the heat of the nuclear waste would be safely distributed over a large area.
c. Designing the heat insulation of The Decay Room to cease functioning before the nuclear waste containment does the same. One way of doing this would be to use a (as in “option b”) relatively low melting point material such as tin, lead or aluminium could be used in the Decay Rooms Design to block a potential air flow route (and if this material blockage is also the area of the Decay Room least able to cope with high pressure the air route behind it could double up as a pressure safety valve).
The logic behind “option c.” is that the melting of air routes blockage and subsequent activation would let heat out (hence helping cooling the decay room down).
d. Another (somewhat ironic) way of cooling The Decay Room down would be to use a burnable material such as plastic as the primary form of heat insulation. (As in “option c”) a suitably relatively low melting point material such as tin, lead or aluminium could be used in the Decay Rooms Design to block a potential air flow route (and as in option c) if this material blockage is also the area of the Decay Room least able to cope with high pressure the air route behind it could double up as a pressure safety valve).
Part of the logic behind “option d” is the assumption that the plastic heat insulating material will never become radioactive because the waste containment is sufficient to prevent this.
The logic is that the nuclear waste containment will be designed to able to withstand the temperatures that can be expected from a fire caused by the burning of the containments heat insulation; but would not need to be able to withstand the greater temperatures that can be expected if it was left without cooling, and with heat insulation that had not been greatly reduced in efficiency by its burning.

Part 3
The level of Waste Containment…
Although it may not be desirable for much (or any nuclear) fusion to occur between different quantise of nuclear waste (for cost reasons; as well as because of the increased radioactivity this will incur and indeed cause) it will probably not be necessary to contain the nuclear waste to the same degree as it would need to be contained if it was going to be abandoned or stored over long periods of time within a nuclear waste dump-site.
Therefore the design of the nuclear waste containment can be minimised. Options…
a. To the degree that virtually no radiation can escape
b. To the degree where radiation can escape within the decay room but no significant nuclear fission can occur between different quantities of waste.
c. To the degree where a small amount of safe nuclear fusion can occur

Comments: Perhaps the biggest problem with “option part 3 c” is the issue of public acceptance (particularly in the West). This is because it does make The Decay Room a nuclear reactor as far as nuclear fission is occurring between different quantities of waste.
Furthermore this option would also (almost inevitably) contaminate the interior of The Decay Room with radioactive nuclei, and perhaps also the water within it. This will lead to larger decommission costs resulting from nuclear waste creation. Furthermore it makes the use of option d of part 2 a hazard because if the interior of The Decay Room was irradiated its burning would surely release this radiation into the surrounding environment.

Conclusion…
A working model of mine would include: All of Part 1. (At least) the requirements for the safety mechanism of option Part 2 b, and the degree of nuclear waste radiation shielding described in option Part 3 b (providing the radiation insulation is sufficient to prevent any dangerous level of radiation escaping from radioactive nuclei escaping from the waste therefore and irradiating the interior of ether The Decay Room or its water.
In addition a user of this idea may be required to protect The Decay Room from the dangers of intrusion and terrorism. If so it would be advisable to build The Decay Room underground as well providing it adequate security features (and of course also staff).

END OF PUBLICATION

So ATS what do you think of this idea publication? Would it be practical? And has somebody come up with it before me? If they have what do reckon are the great barriers to its wider use?

en.wikipedia.org...'

Several spacecraft use this for power. Very similar to what you propose but I don't know about using waste. It'd have to be purified to get the highest yield in the smallest package.

Yes that’s true but they use a thermocouple(s) which are extremely inefficient. Therefore this is different to the somewhat more conventional steam powered electricity generation apparatus approach I am suggesting for nuclear waste.

As for purification it wouldn’t make that much difference how bulky the radioactive material (plus its casing) was if the heat insulation (ether around or inside) The Decay Room was good enough. Only it might not be (because of construction cost considerations) and so I take your point wherever the construction costs of heat insulation are too prohibitive.
However because processing nuclear waste is also extremely expensive I believe the need to process it for The Decay Room can be bypassed altogether as long as mankind has plenty of surplus stockpiles of naturally hot radioactive materials like e.g. plutonium
www.google.co.uk...

[edit on 090705 by Liberal1984]

That's exactly what nuclear reprocessing does, and it's used in most of Europe right now. Of course, the energy isn't exactly infinite, like you might think it is, partly because the process of collecting energy and reprocessing fuel rods isn't perfect, and it's impossible to collect infinite energy from anything. Eventually, the only energy left is so minute and diffuse that's its just not worth the time and effort to obtain it because it would require more energy to get it than to use it. That diffused energy is then emitted as black-body radiation.

Also, nuclear reprocessing is illegal in the US because idiot politicians think that reprocessing creates weapons-grade nuclear material. That was partially true during Carter's administration, but modern reprocessing techniques prevent that.

Well supercheeter nuclear reprocessing concentrates usable products contained within nuclear waste for reuse. But that’s not the issue I'm trying to address.

Mankind has a surplus of materials like plutonium but the issue behind the surplus isn’t really to do with how pure the plutonium is; rather that there is simply more of it than we need for things like specialist reactors or indeed nuclear bombs. So instead a lot of hot radioactive material is sitting in storage doing absolutely nothing useful (other than decay).
And even if the surplus of suitable radioactive materials did become an issue of purity there is still little reason why it could not sit in my decay room (at temporarily) until there is a specific and fast approaching time to reprocess it.

My idea evolves around storing high level radioactive material (which has to be stored somewhere anyway) inside a “Decay Room” as explained in my publication my objective is to insulate this room; allow it to heat up to water boiling point (or slightly beyond) for electricity generation.

One of the key features of my Decay Room is that it is not a nuclear reactor. This avoids a host of safety, public relations and cost issues. Instead it is simply an insulated room in which (shielded) nuclear waste decays naturally.
It’s occurred to me that a power company running the set up described in my idea publication would not need to own the nuclear waste it uses (and hence also it’s the long term liability). Instead it could merely lease the stuff over a number of years; and because there is plenty of hot high level nuclear waste which would not normally be used for anything; I would imagine that the cost leasing nuclear would be very low.

So I know what you mean supercheetah about reprocessing being a way of concentrating waste.
I agree 100% about U.S reprocessing laws being completely outdated; and to my surprise it looks as though Bush is going to leave the White House without addressing this issue.
It’s a little known fact but using technologies already in existence we could burn up almost all of our nuclear waste within 300 years: www.npl.washington.edu...
(Trouble is the best approaches require reprocessing).

The problem with nuclear waste is that it has a very long half-life. However this can be overcome by putting the waste in a neutron beam, the subsequent nuclear reactions then create isotopes with shorter half lives allowing the waste to transmute into other elements and also generate energy.

See:

www.npl.washington.edu...

I just figured out that you're not the first to come up with this idea. Sorry.

China is going to (or already have?) build a 200 MWt nuclear reactor that uses spent fuel to generate heat and desalinate water: www.uic.com.au...

Other people are doing research on reusing spent fuel: aiche.confex.com...

And for some reason, the US just wants to bury it all under the Yucca Mountain instead of actually reusing it like the Chinese. They fear the security problems over the enormous energy benefits of reusing the fuel. Idiots.