Thorium reactors - an idea whose time has come?

An article in the Daily Mail reminded me of recent developments in thorium reactors. It seems that a group of British scientists is making real progress in this field.

Imagine a safe, clean nuclear reactor that used a fuel that was hugely abundant, produced only minute quantities of radioactive waste and was almost impossible to adapt to make weapons. It sounds too good to be true, but this isn’t science fiction. This is what lies in store if we harness the power of a silvery metal found in river sands, soil and granite rock the world over: thorium.

One ton of thorium can produce as much energy as 200 tons of uranium, or 3.5 million tons of coal, and the thorium deposits that have already been identified would meet the entire world’s energy needs for at least 10,000 years. Unlike uranium, it’s easy and cheap to refine, and it’s far less toxic. Happily, it produces energy without producing any carbon dioxide: so an economy that ran on thorium power would have virtually no carbon footprint.

Better still, a thorium reactor would be incapable of having a meltdown, and would generate only 0.6 per cent of the radioactive waste of a conventional nuclear plant. It could even be adapted to ‘burn’ existing, stockpiled uranium waste in its core, thus enormously reducing its radioactive half-life and toxicity.

Since the Japanese earthquake and tsunami, and the consequent meltdowns and radiation leaks from the Fukushima I power plant, the future for nuclear energy worldwide has been cast into doubt: Germany has announced that all its plants are to be closed. Thorium offers the potential to revive a moribund industry – along far less dangerous lines.

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The good news is that, thanks to funding from the Research Councils UK Basic Technology Programme, we’ve taken the first, critical step to making this dream a reality – constructing an incredibly hi-tech, cutting-edge machine with a surprisingly ordinary name: Emma.

Daresbury, the science park where Emma lives in a big, bare building with solid concrete walls more than two feet thick, isn’t especially scenic – it’s overlooked by a power station and stands on the boggy Cheshire flatland between Runcorn and Warrington, at the head of the Mersey estuary.

Inside, it’s hard to talk, as the cryogenic vacuum pumps that keep the innards of Emma’s friend Alice cooled to -271°C are extremely noisy. Yet Emma – the Electron Model of Many Applications – is an object of scientific beauty, a shiny blue-and-red metallic ring bristling with cables and flat, octagonal quadrupole magnets (magnets arranged in groups of four).

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It would ... be incapable of undergoing a Chernobyl-style meltdown, as a thorium reactor would be ‘subcritical’. There’d be no ‘critical mass’ of unstable, radioactive material liable to produce a runaway chain reaction if its control mechanisms failed.

In fact, left to its own devices, nothing would happen spontaneously in a thorium reactor at all. Thorium atoms only start to undergo fissile nuclear reactions and thus to release their energy when they’re bombarded with neutrons, and these would have to be supplied by an external source – ultimately, an accelerator.

‘This means the margin of safety is far greater than with a conventional plant,’ says Cywinski. ‘If the accelerator fails, all that will happen is that the reaction will subside. To stop the reactor, all you would have to do is switch off the accelerator.’

And if hit by an earthquake, he adds, even one as powerful as the one that wrecked Fukushima, a thorium plant would be ‘intrinsically safer’.

‘There’d be some residual radioactivity heating the core, but sustained nuclear fission would simply stop. Everything would cool much faster. You’d be left not with potential catastrophe, but just a heap of molten metal and metal oxides.’

There's more at the link.

Thorium reactors have been discussed for decades. An experimental unit was built in the USA during the 1960's, but not pursued. However, India is mounting a big push in the field, and China has announced it's investing in the technology as well.

In the aftermath of the Japanese earthquake and tsunami, and the catastrophic damage to the Fukujima nuclear power plant, thorium reactors (which pose minimal radiation risk) would seem to be an idea whose time has come. Unfortunately, the only research currently under way in the US is a project involving a Texas university and the Los Alamos National Laboratory (although thorium fuels are only part of the project).

Ambrose Evans-Pritchard pointed out last year:

If Barack Obama were to marshal America’s vast scientific and strategic resources behind a new Manhattan Project, he might reasonably hope to reinvent the global energy landscape and sketch an end to our dependence on fossil fuels within three to five years.

We could then stop arguing about wind mills, deepwater drilling, IPCC hockey sticks, or strategic reliance on the Kremlin. History will move on fast.

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There is no certain bet in nuclear physics but work by Nobel laureate Carlo Rubbia at CERN (European Organization for Nuclear Research) on the use of thorium as a cheap, clean and safe alternative to uranium in reactors may be the magic bullet we have all been hoping for, though we have barely begun to crack the potential of solar power.

Dr Rubbia says a tonne of the silvery metal – named after the Norse god of thunder, who also gave us Thor’s day or Thursday - produces as much energy as 200 tonnes of uranium, or 3,500,000 tonnes of coal. A mere fistful would light London for a week.

Thorium burns the plutonium residue left by uranium reactors, acting as an eco-cleaner. "It’s the Big One," said Kirk Sorensen, a former NASA rocket engineer and now chief nuclear technologist at Teledyne Brown Engineering.

"Once you start looking more closely, it blows your mind away. You can run civilisation on thorium for hundreds of thousands of years, and it’s essentially free. You don’t have to deal with uranium cartels," he said.

Thorium is so common that miners treat it as a nuisance, a radioactive by-product if they try to dig up rare earth metals. The US and Australia are full of the stuff. So are the granite rocks of Cornwall. You do not need much: all is potentially usable as fuel, compared to just 0.7pc for uranium.

Again, more at the link. One hopes someone in the White House is listening . . .

Peter