Hybrid fusion-fission reactors to run on nuclear 'sludge'
Most nuke waste actually useful fuel, say boffins
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Texas-based boffins say they have figured out a cunning new method of dealing with America's nuclear waste, using fusion technology - which at the moment can't produce power - to turn 99 per cent of fission reactors' waste into useful energy.
"Most people cite nuclear waste as the main reason they oppose nuclear fission as a source of power," says Swadesh Mahajan, nuke scientist at Texas Uni. He might be wrong there - the roots of the antinuclear movement very frequently lie in opposition to nuclear weapons - but there's no doubt that waste is a major concern.
In particular, the cost of long-term waste storage accounts for a major proportion of the price of fission-generated electricity.
Power from burning rubbish, fusion style.
But the Texas Uni boffins reckon that high-level nuclear waste is actually a major resource, handled in the right way. Countries such as France and Japan already reprocess and re-use some of their waste, but America doesn't: which is one reason why the US has such a large waste stockpile.
The first step, according to Mahajan and his colleague Mike Kotschenreuther, is to use the waste again in America's 100 light water reactors (LWRs), so generating large amounts more energy. This will reduce the waste volume by three-quarters, leaving a final 25 per cent of transuranic high-level waste which can't be made to fission by the level of neutron radiation found inside a normal reactor* - rather as the heaviest fractions of crude oil are very difficult to burn. The Texas boffins refer to these wastes as "sludge".
But highly radioactive waste can't be used for road tar as heavy hydrocarbon fractions are - it needs to be expensively stored or ideally got rid of, by breaking it down through fission into smaller atoms.
To do this, it needs to be blasted with neutrons, even more vigorously than it already has been in the LWRs.
"To burn this really hard to burn sludge, you really need to hit it with a sledgehammer, and that's what we have invented here," says Kotschenreuther.
That's where the fusion tech comes in. Tokamak fusion reactors are excellent for emitting lots of neutrons - their downside, so far, is that sustaining the ring of neutron-spraying plasma inside the tokamak doughnut requires more energy than the fusion reaction gives out. As a result, such reactors are currently only used for research.
Kotschenreuther and Mahajan, however, propose putting heavy transuranic "sludge" around a specially-pimped tokamak, fitted with a "Super X Divertor" allowing the neutron emissions to be cranked right up without destroying the containing doughnut. The neutron blitz would hit the surrounding heavy wastes, fissioning them and yielding energy, though the tokamak would be using energy up.
The scientists aren't yet going firm on whether the hybrid fusion/fission reactor would be a net user or generator of power, but seem sure that if it does draw juice overall it won't be much compared to that generated at the LWR stage of the process. Also, it would be cheaper than storing the wastes.
COMMENTS
I object to nuclear power.
I object to nuclear power.
Why? It's simple: People.
People make mistakes, all of us do, it's a simple fact of life; even the best of us gets tired occasionally. Now that private companies are running the reactors, there's a reasonable chance that we're looking at minimum wage people. Minimum wage people with minimum training, operating a nuclear power station. Are you getting a warm fuzzy feeling yet?
Before anyone suggests computer control, may I remind you that we also design computer systems, so computer control could well have similar fallibilities. That's assuming the functional specification was any good to begin with. Did I mention that developement is probably going to be outsourced to a ghetto in a country no-one's heard of? Where they don't really care if *we* get blown up or not; since they're several thousand miles away.
Then there's the slight matter of who's building these reactors. Again, these are being built for profit; so this means it's likely someone will be cutting corners when no-one's looking. Regulators you say? Well bribery's cheap compared to doing it properly, and then there's good old fashioned oversight.
Even when there was no particular emphasis on cost, and trained scientists were involved bad things have happened. When cost becomes the key motivating factor; do the odds improve or get worse?
Then there's decommissioning. When private companies are responsible for operation and clean up I have a guarantee for you. When the reactor is operating at a profit, those profits will go to the shareholders. When the reactor becomes loss making; during decommissioning, or after an accident; I'm prepared to bet that the company operating the reactor will file for bankruptcy. So, who gets to pay the bills then? That'll be us, the taxpayer.
So, what we have is something that'll be a potential hazard throughout it's lifecycle; and then will cost us billions to tidy up. Those billions will come from our taxes.
Still sounding like a great idea? Ahh, you're a shareholder; sorry ;)
RE: I love it when people say...
Ah, the irony.
Someone spouting off about what they know not and kidding on they're one of the cognoscenti.
Tritium. Even rarer, but still a lot of it.
Fusion reactor, with Lithium shell around. Lithium is so easy to get that we make batteries out of it.
Tritium gives excellent energy conversion with the temperatures we can manage in a tokamak (much lower than the solar core) and releases neutrons.
Neutrons hit lithium and the product is.... tritium!
There *are* engineering problems but your four points are neutered badly if you consider the above real-life example.
Fusion fanboy
"fusion, the same process that powers the sun, involves no carbon emissions, no troublesome wastes and no finite resources. The only fuel needed would be isotopes of hydrogen, the most common element in the universe, easily extracted from water."
Since you're obviously talking about Deuterium fusion, you're wrong. This generates neutrons which make the reactor radioactive. Radioactive reactor stuff is troublesome waste. IIRC there will also be some radioactive and highly toxic Tritium produced.
Deuterium is also a finite resource.
These problems are greatly less than they are for fission power, but your fanboyish claim that they go away entirely is just wrong.
You're spot on about the lack of carbon emissions though.
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