Climate change is a challenging topic for the green movement. Environmentalists can take the credit for being amongst the first to sound the alarm when the rest of the world chose to ignore the gloomy pronouncements being made by the scientific community.
However, the range of people now concerned about the threat we face has grown hugely in recent years and so too has the range of solutions being put forward. Not all of them have found favour with the green lobby. It is easy to find reasons to object to things but if we are going to successfully decarbonise the global economy then we cannot afford to rule out too many technologies before properly exploring and assessing their pros and cons.
It is tempting to think that all nuclear reactors are the same, and by extension, to place liquid-fluoride thorium reactors (LFTRs) in the same category as existing solid-fueled uranium and plutonium reactors.
However, just as it is possible to abhor nuclear weapons but support the use of radioactive isotopes in lifesaving medicine it is necessary to differentiate between different forms of nuclear power. Most of the problems currently associated with today's solid-uranium-fuelled reactors simply do not apply to LFTRs powered by thorium.
We worry about a "meltdown" in a solid-uranium reactor because it can lead to the release of radioactivity. But many features of a LFTR make it inherently safer. A liquid fuel is the normal mode of operation, which means the reactor can be designed to automatically drain itself into a walk-away safe configuration in the event of a problem.
A well-designed LFTR won't require emergency power or human intervention to shut down safely. The fluoride fuel form doesn't react with air and water and traps potentially dangerous elements like strontium and cesium as chemically-stable salts. LFTRs achieve high temperatures at normal pressure, unlike water-cooled reactors which require operating at high-pressures leading to safety concerns.
We are right to be concerned about the risk of military proliferation, but thorium was rejected early in the nuclear age because it is vastly more difficult to weaponise. There are 70,000 nuclear weapons in the world and none are based on thorium or its derivatives.
Another long-lasting concern is the waste generated in today's reactors because they use less than one per cent of the energy in their fuel and generate plutonium as a waste product. But a LFTR uses thorium and burns it up nearly completely.
Even the miniscule amount of waste has beneficial uses in medicine and exploration. The fluoride fuel used in a LFTR is impervious to radiation damage, allowing us to recycle the fuel into another reactor when the current one finishes its useful life. We can also use LFTRs to destroy existing stocks of separated plutonium rather than waiting tens of thousands of years for it to decay away. LFTRs can use up plutonium or highly-enriched uranium from decommissioned weapons to get the fission reaction started and thereafter run only on thorium.
Yet another problem is that today's reactors need to be built big and only produce one product—electricity. But LFTRs can be built small and they can be distributed geographically – even to generate combined heat and power. They can also be operated in a responsive and flexible manner – thus complementing rather than competing with intermittent renewables.
We worry about the environmental effects of mining and processing uranium. But thorium is far more abundant than uranium and is being mined already in the search for rare-earth minerals for renewable energy generators. Thus we don't need new mining for LFTRs—actually much less—and we can use thorium highly efficiently.
Despite the many potential benefits, as things stand, generating energy from thorium remains unproven although R&D projects are being pursued in France, China and India.
In the UK eight sites for potential new nuclear reactors have recently been announced. We are poised to go down the same road pursued by the Conservative Government in the 1980’s when they announced a programme to build 10 new reactors.
In the end only one was built – late and massively over budget. But it cannot be denied that even that one station helped to reduce the UK’s output of carbon dioxide from electricity generation. This fact has lead to a reversal in fortunes for the existing nuclear industry but the problems with uranium-based technologies have not gone away.
To successfully reduce the risk of climate change we need to commericalise affordable, safe, flexible, long-lasting, low carbon sources of energy. We do not know yet if LFTRs fit the bill but they look extremely promising. It would be irresponsible to dismiss them out of hand before finding out. If the UK is serious about pursuing nuclear power, and it appears that it is, then we must include the pursuit of thorium power in this endeavour. On paper it looks like it may just save us.
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