Thorium reactors powered on nuclear waste

Too bad this wasn’t started back in 1970 — time is running out now, and what are the odds that there won’t be a financial crash before 2023 preventing this pilot project from being built?  There is no thorium mining industry, and the electric grid is not being maintained, and is rusting apart, requiring additional trillions. Finally, 97% of our transportation, like tractors and trucks and trains run on OIL, so generating electricity does nothing to stave off the crisis, and the mining, construction, and maintenance of thorium reactors all depends on fossil fuels throughout the supply chain.  Once oil is short, it’s likely to be rationed to agriculture and other essential services, not building thorium reactors.

Thorium has many many issues and is unlikely to ever be a source of nuclear power, what’s interesting about this article is that it exposes how insanely dangerous Uranium waste is from nuclear reactors.

30 May 2012. James Mitchell. Nuclear alchemy: Thorium promises power from waste. NewScientist.

Highly radioactive nuclear waste is the not-so-secret filthy secret of the nuclear industry. Global stockpiles grow by more than 10,000 tonnes each year. In the US, nearly 65,000 tonnes or about 26,000 cubic metres of spent fuel sits in interim facilities at 75 sites across the country while political wrangling about its ultimate fate continues. That contentious legacy is expected to double by 2050 – and is dwarfed by high-level waste left over from America’s nuclear weapons program (see “Toxic legacy”).

The problems start when fission doesn’t happen. About 95% of spent nuclear fuel is still in the form of uranium-238, a non-fissionable but radioactive isotope that dominates mined ore. Uranium can be extracted and reprocessed into fuel at facilities like La Hague, but this is an expensive business. Freshly mined uranium is much cheaper, so most countries leave the spent fuel as it is.

And reprocessed or not, spent fuel contains other, less tractable, nasties. Occasionally when a uranium atom is hit by a neutron within a reactor, it simply absorbs it. That can happen to any one atom several times, and a series of heavier elements results, including plutonium, americium and neptunium. These “heavy actinides” are the real sting in the nuclear tail. Their typical half-lives of thousands of years mean they will remain dangerously radioactive for tens or even hundreds of thousands of years, long after most of the other components of nuclear waste have decayed away (see “No quick fix”).

In theory these actinides could be broken down into shorter-lived, less harmful compounds. to test this construction is due to begin in 2015 on a reactor that the European Union hopes to finish by 2023, powered by Thorium.

Thorium is a nuclear fuel with a long list of potential advantages over uranium. It is three to four times more abundant, and all of it can be used as a fuel, whereas natural uranium deposits contain only 0.7 per cent uranium-235. Thorium was extensively used in early prototype fission reactors. When nuclear power really took off in the 1970s, however, new deposits of uranium were being discovered all the time, and thorium reactors suffered from a further disadvantage: unlike uranium reactors, they don’t generate much plutonium, the raw material for nuclear bombs. “I am convinced that uranium won out because there is no military application of thorium,” says Roger Barlow, a particle physicist at the University of Huddersfield, UK, who researches thorium as a fuel. “Nuclear power and nuclear weapons were developed hand in glove.”

Thorium is not itself fissile. Its atoms first soak up neutrons to form uranium-233, which is fissile and falls apart in a burst of energy when the next neutron hits. Sustaining this two-step process requires more neutrons than are generated, so an outside neutron source is needed – exactly what an accelerator would supply. And although running an accelerator requires an awful lot of electricity, that energy demand would be dwarfed by the reactor’s output: you would only need a 20 megawatt accelerator to generate 600 MW, says Parks, and potentially one even smaller than that. The set-up has another benefit too: the fission reaction can be switched on and off at the flick of a switch. “The chain reaction would die out if it wasn’t for the accelerator producing neutrons, which means that a Chernobyl-style accident is impossible,” says Parks.

The crucial point, though, is that thorium atoms have a smaller number of neutrons – 142 in thorium-232 against 146 in uranium-238 – and that makes a huge difference to the waste it produces. A thorium atom has to capture more neutrons to make the troublesome heavy actinides, so the reactor makes less of them. “It manages its own waste while it’s operating, but it’s got the capacity to deal with more than its own waste,” says Parks. “So you have a device that is simultaneously generating power, exploiting an available resource and getting rid of problem waste.”

Even if any variant of a transmutation reactor can be shown to work at a reasonable cost, it will still have big hurdles to jump. A conventional nuclear reactor core is kept cool by pumping water through it, but collisions with water molecules slow neutrons down. To keep neutrons whizzing about with the energies needed to fission heavy actinides, a reactor needs heavier coolant molecules that neutrons ping off while retaining most of their energy. For MYRRHA, that coolant will be liquid lead: a nasty, corrosive material that is difficult to contain within a reactor core.

Establishing any energy-generating technology using thorium will also take time. The small amounts of the element currently produced as a by-product of mining valuable rare earth elements are enough to keep research reactors ticking over, but not to supply an industry. A whole new infrastructure would be needed, from mining to refining. That is not fundamentally difficult, says Parks – but it won’t come for free.

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4 Responses to Thorium reactors powered on nuclear waste

  1. Ed Pheil says:

    This is a trash talk advertisement to denigrate all nuclear research but his pet. What BS diatribe.

    The largest nuclear producing country only produces one football field worth of reusable fuel needing temporary storage, not waste, 5 meters deep (26,000 cu. meters) using LWRs. That is a phenominay GOOD record for waste minimization.

    Both uranium and thorium and any uranium transuranics can be completely consumed so that is not really a discriminator ultimately and Th is NOT 300x as efficient as uranium. Maybe 300x as efficient as current LWRs, but that is only a matter of changing the reactor and/or reprocessing the fuel, which the article does with adding the accelerator. And uranium-238 can be used to denature both 235U and 233U from Th with regard to proliferation resistance.

    Claiming every reactor can be a Chernobyl to justify an unreliable waste of energy accelerator is ludicrous. Plus most of the damage/radiation release was caused by decay heat, not criticality problems. Accelerator reactors have the same decay heat. An accelerator does not solve Fukushima Daiichi’s or TMIs decay heat type problems either. Changing the coolant to high temperature capable low pressure non-reactive fluid, a higher temperature capable fuel or liquid fuel. and a passive decay heat removal system does that.

    Converting Th to 233U and fissioning it only takes 2 neutrons, and fissioning 233U produces an average of 2.5 neutrons per fission. Last I checked 2.5 > 2.0, so accelerator neutrons are NOT required to convert and fission thorium or 238U for that matter. A neutron efficient reactor does help, but the Shippingport reactor bred more 233U from thorium than it consumed (1.06x) using the first commercial light water PWR in the country back in the 1970s.

    I could go on, but you get the point. What an embarassing article. Yes thorium is another fuel and is more common.

  2. Jim Corey says:

    I generally agree with Ed. When I read in the original article the phrase, “uranium-238, a non-fissionable but radioactive isotope,” I knew I had to be careful about what I read in the rest of the article. Uranium-238 is of course fissionable, it is just not fissile. Also, it made the statement that plutonium (239Pu) is the fuel for nuclear weapons; I believe that most nuclear proliferants began with weapons using 235U as fuel. There are large programs in France (EU), Russia, and India to develop thorium reactors, and India (and I believe Iran) has large deposits of thorium.

    I have one disagreement with Ed. I don’t believe excess 233U needs to be “denatured” with 238U, as 233U is generally considered not to be suitable as fuel for nuclear weapons.

  3. Ed Pheil says:

    I did not say that you had to denature 233U with 238U, but that you could. Technically you can make a weapon out of 233U and that will be produced in large quantities in a thorium reactor. The thing inhibiting that is more a cost issue of having to periodically clean the 233U of 232U decay products to while handling it to make the weapon. That extra cost is of course a factor in enhancing proliferation resistance, as is the ability to detect the high energy gamma from 232U decay products after the cleaning is stopped and the weapon has been manufactured. So, I mentioned that possibility of denaturing as a option for those that want to reach even more sophisticated proliferation resistance…or want to argue against thorium as a fuel. I do not agree that the denaturing is needed. Although denaturing of a liquid fueled thorium reactor is possible in an emergency, but would not need to be in there for normal operation.