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.