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October 02, 2005

Comments

Joseph Somsel

As the author of the referenced article, I'd say that the above is a pretty good summary. Using geologic isolation is a policy that is almost 30 years old and was a default position for the Carter Administration's non-poliferation policy. Times change.

Looking at the problem today, I see the State of Nevada and the Department of Energy locked in what seems like a very bad marriage. They seem to enjoy fighting but little progress is being made.

In summary, it is a LOT cheaper to recycle spent nuclear fuel than to bury it, given the current program. Plus, we'd have a decade's worth of reactor fuel for our current reactor fleet. In the long run, burying it just makes a very attractive, very expensive plutonium ore body.

I welcome constructive discussion.

JesseJenkins

How much of the original nuclear waste remains after being recycled and in what form (what element/isotope) and what is the half-life of the remaining waste? (I haven't read the article, I apoligize).

Joseph Somsel

In the classic proces, the spent fuel is cut up and dissolved in acid. The chemical processing that follows would split the materials into three main streams. The uranium and plutonium is the good stuff; it can be further seperated or used with blending into new reactor fuel to make more juice.

The second stream is a mess of stuff called fission products. These are the fragments of uranium and plutonium after they've split. These decay relatively rapidly and are maybe 1 to 3% of the original tonnage. 100 to 500 years is all you need for these.

The stuff that is the real headache are the actinides (formally, minor actinides), stuff like americium and californium, where uranium absorbs a neutron and doesn't fission - they can just keep piling on. This stuff drives the long retention times at Yucca Mountain. There is not much of this from fresh fuel but the longer you keep the fuel in the reactor (economy drives this, now about 5 years) and the more you recycle, the higher the content of minor actinides. Let's call it 1% but it is sensitive to the total fuel cycle design. In any case, there is not much of it, physically.

The key plan is to take the minor actinides, separate them from the spent fuel, turn them into special fuel for special reactors called "actinide burners". Poof! They turn into fission fragments too and make a little electricity on the side.

My core point is that Yucca Mountain costs have gotten so high that a complete recycle system is much cheaper and uses much less yellowcake.

Read the article.

JesseJenkins

Thanks Joseph, and I will (read the article). Cheers...

Leslie

The analysis of data on uranium resources leads to the assessment that discovered reserves are not sufficient to guarantee the uranium supply for more than thirty years.

Uranium Resources and Nuclear Energy
From the Energy Watch Group

Mac McCarthy

I am somewhat baffled by the nuclear waste issue. There is byproduct of nuclear power plants; the byproduct is "hot" -- literally, as well as radioactively.

Something that is hot is giving off energy; why do we bury this material? If it IS hot, can it not be used in power production too?

If it's not hot enough to boil water in its form as wastes, it can certainly warm the water entering the power plant, creating efficiencies. As long as it is above ambient temperature, it should have some use warming something. Only if it were giving off no heat but only radioactivity would it no longer be of use in power production.

Then, one presumes, it might be mined to concentrate the radioactive material to produce heat-generating fuels, the way we do with raw earth containing uranium. If we can process the tiny amount of appropriate isotopes from dirt dug from the earth at uranium mines, then we can do the same for nuclear wastes. For some reason I don't follow, it's supposed to be much more expensive. Weird.

Finally, when we elect to bury the wastes, I don't quite grasp that problem either. We have nuclear materials buried in the earth already -- every uranium mine on earth is, by definition, filled with radioactive material. Doesn't seem to be a problem.

So we could take the wastes to uranium mines, dilute it with leftover earth from the mining process until it is reduced in concentration to something similar to the level of the uranium-mine area, then bury it back into depleted areas of the uranium mine. We've then restored things to where they were before we showed up. There shouldn't be any more risk to the area or its water supply than is already present by the fact that this was uranium-filled earth to begin with.

It's not that I believe my thoughts so clever; it's just that the above seem to be natural questions, and I can't understand why nobody ever acknowledges them and explains why these seemingly obvious solutions won't solve the problems. Well, *I'd* like to know why you must dispose of things that are so dangerously hot and radioactive as to threaten civilization but isn't hot enough to be a fuel; why we can dig radioactive materials out of the earth but can't rebury sufficiently diluted radioactive material back into the earth, and how the heck you can define nuclear materials as "waste" when they are so interestingly active?

I appreciate the patience of anyone who takes the time to fill me in.

mac.mccarthy@gmail.com

Cyril R.

This article is not correct. Recycling waste is not possible since we are not talking about a mass-mass transfer here, but mass-energy transfer (E=MC2). There is no cycle; it would not make commercial sense for us to use insane amounts of energy to make a tiny amount of matter.

Reprocessing spent oxide fuels is a real option. Unfortunately, this is difficult because the fuel is so stable - it has to be in the demanding reactor environment. The difficulty makes it much more expensive than using virgin uranium fuel. Since the latter is not in short supply, reprocessing LWR spent fuel is a non-starter. However, the added levelised cost of reprocessing is quite low since fuel costs are only a small portion of total nuclear cost.

So, reprocessing would be interesting if it yielded a large amount of additional net energy and mitigated the costs long term spent fuel storage.

Unfortunately, reprocessing oxide fuel methods in use today do not offer such advantages. Perhaps 10-20% extra energy becomes available through reprocessing, and spent fuel storage costs are not reduced significantly, and it doesn't matter much even if it did, since the levelised cost of dry cask spent fuel storage is tiny. Since the spent reprocessed fuel is nastier than regular once through spent fuel, storage costs are unlikely to be reduced. Reprocessing spent LWR fuel is an incredibly marginal technology, while it substantially increases the total radiactive emissions into the environment, compared to not reprocessing with dry cask storage.

Reprocessing could be attractive in a reactor that uses metallic fuel (not ceramic oxides) like the hydride reactor, and is mandatory for the integral fast reactor.

Kit P

Mac

You may have a case of compulsive waste disorder (CWD). When one with CWD hears the word waste, they feel compelled to do something about it. Let me give you an example. When you return to your house after driving, you could hook your car up to your hot water heater in your house and get enough 'free' hot water thus saving you about 25 cents.

I sure Mac can explain that in his busy day saving 25 cents is not very practical.

So here is the deal Mac. When a uranium atom fissions a large amount of energy is released but radioactive decay of one of the two atoms produced by releases a releases a relatively small amount of energy. A commercial nuclear reactor producing 1000 MWe could produce 10 MWe a day or so after the reactor is shut down for refueling. However, decay of spent fuel is exponential. Six months later maybe only 10 kWe would be possible.

While the amount of energy from decay is too small to be a practical energy source, if the energy is absorbed in the cell of a human cell it would be harmful to health. So people should not stand next to spent nuclear fuel without shielding. Fear of radiation trumps CWD.

Cyril R.

Kit P is spot on here. The heat generated from the spent fuel is tiny compared to the heat generated to active fuel elements in the reactor.

Further problems are related to safety and practical matters, for example generating efficiently requires high temperatures (to get high temperature differences for an efficient heat engine) while the spent fuel must ideally be kept at lower temperatures to make storage safe and controllable. The colder the cheaper and safer it is to store the spent fuel. Clearly these requirements are opposite to each other.

Storing nuclear spent fuel is not a big problem, although it is perceived to be a big problem. Far more serious is the high and escalating costs of nuclear technology, especially in the US. New plants are not cheap.

I think the $ 20 billion for $ 1000 billion in electricity is misleading; reprocessing is more expensive than non-reprocessing once through, so reprocessing costs money rather than saving it compared to the base case. Since uranium is not in short supply this is a relevant argument.

A more accurate wording would be "20 billion extra for the same amount of kWhs" - and that's assuming the 20 billion is correct/won't inflate etc.

Kit P

Cyril

I would have no problem safely and efficiently making electricity with spent fuel. Controlling is not difficult and nuclear fuel rod are designed to operated under these conditions it is just that the amount of U-235 can no longer maintain a chain reaction. However, the amount of electricity would be too small to bother with.

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I'm working on a green house project. I'm really interested by this Recycle Nuclear Waste.
thanks a lot!
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vaughn nebeker

why should there be nuclear wast. put solar cell next to it an use the wast as a power scorce. 250,000 year's of power in a solad nuclear state. a magnisuem wire to inshore 100% burn up at satalight rentery.
left over nuclear wast equeal=zero.

vaughn nebeker

radio active carben from nuclear wast,between two layers of perix glass.with two solar cell's 7.0 volt's. Add a coyeal get 3.5 watt's. a magnisuem wire next to it insoures 100% burn up at rentery. left over nuclear wast=zero. but the satalight play in darkness for 14 year's.
why should nuclear wast be a wast. why not put the wast to work in getting it to perduce power.
vaughn nebeker the scintest who technology put out chernobyl & three mile island.

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