12 June 2011

An Energy Revolution Goes Sub-Critical


Somewhere in Cheshire an energy revolution is brewing. Modern nuclear researchers are developing new approaches to safe subcritical reactors, using fertile thorium as fuel. The new reactor designs will be incredibly safe, proliferation resistant, and will produce only miniscule and easily stored amounts of long-lived nuclear waste.
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...

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.

...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.

...Emma is a particle accelerator, the first of an entirely new type. Since the first such machines were built nearly 80 years ago, accelerators – devices that propel beams of electrons, protons or other particles to high speeds – have played a vital role in experimental physics, opening up fresh insights into the origins of the universe and the nature of matter. But most are big and expensive. The best known and biggest of all is the Large Hadron Collider operated by CERN in Switzerland, an underground ring 17 miles in circumference, which cost billions to construct.

Emma is different. She is the world’s first ‘non- scaling, fixed-field, alternating-gradient’ (NS-FFAG) accelerator. In layman’s terms, says Bliss, this means she is a ‘pocket-sized’ machine, the prototype of a new generation that will be significantly smaller and cheaper than its predecessors.

And this is Emma’s special significance. Making particle accelerators affordable means they could be built and used in practical, everyday settings – such as thorium power stations. The key to thorium energy is likely to be the further development of ‘pocket-sized’ machines – precisely the kind of accelerator that looks and behaves like Emma.

... 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 – [for example] 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.’

This type of plant – dubbed the Energy Amplifier by the Nobel Prize-winning physicist Carlo Rubbia in 1993, when he patented the basic design – wouldn’t be simple. Because neutrons carry no electrical charge, the magnets in a particle accelerator have no effect on them.

Hence, the way to generate the neutrons necessary to trigger nuclear reactions in thorium would be to build a ‘spallation source’ in the middle of the reactor core. This is a substance – molten lead, for example – which produces neutrons when you fire a beam of protons at it. That beam, in turn, would come from a particle accelerator.

...Last year, ThorEA published a report, Towards An Alternative Nuclear Future, which concluded it should be possible to build the first 600MW power plant fuelled by thorium with three attached ‘pocket-sized’ NS-FFAG accelerators within 15 years, at a cost of about £2 billion – making it highly competitive in relation to fossil-fuel or conventional nuclear alternatives. _GWPF_from_MailOnline
Using "pocket-sized" accelerators to generate spallation neutrons to breed fissile U233 from fertile Th232 might allow for highly scalable and versatile reactor designs, which would certainly be safer than any nuclear reactors currently generating power. And nuclear is by far the safest form of power generation currently in existence.

Below, you can see researcher Rachael Buckley standing inside the EMMA device.
Thorium itself is plentiful, and will be quite cheap once the infrastructure is developed. The cost for subcritical reactor designs depends mainly on the cost of the accelerators and reactor vessels, and containment. The fuel itself is a negligible expense. And by reducing the quantity of waste to be stored and lowering the proliferation potential of the reactor dramatically, those costs would also plummet.

This technology will also be useful in the perpetual fight against cancer:
‘I’m optimistic we can build a machine that overcomes the technical challenges and would be applicable for cancer therapy straight away,’ he says. ‘I think Pamela can be built for an overall cost of £10-15 million, and would take about five years. And that would be a crucial stepping stone towards a thorium power station. It wouldn’t be cheap. But it would be highly competitive.’

It will take time to put the pieces together, but the writing is on the wall, if modern humans will only take the time to read it and take action.

Adapted from a posting on Al Fin Energy

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Blogger horos22 said...

I agree with lots of what you say - but this is not one of them.

It perhaps points to the correct solution - namely molten salt reactors based on thorium - but it isn't the solution itself.

Accelerators are *complicated*, *expensive* things. Tons of parts, materials - hard to scale, hard to implement.

In addition, the fuel in question is a solid, which would lead to neutron poisons like xenon being trapped inside the fuel.

So yeah, I'm glad that thorium is getting attention as a fuel, but my hopes are that either the south african or chinese efforts will spur the required revolution.

Sunday, 12 June, 2011  
Blogger al fin said...

Molten salt reactors using thorium may prove to be the simplest fission solution. If so, I hope someone puts them into production soon.

The story in Cheshire is all about the new type of reactor which is meant to get around many of the problems you mention.

The applications for the newer reactor technology -- once perfected -- are likely to be many. Sub-critical reactors may well be one of them.

Monday, 13 June, 2011  

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