Back in February (OK, yes, I’m currently in catch-up mode) I read a very interesting article on resurrecting nuclear power (a) in a much safer form and (b) to solve our energy crisis. The article was Nuclear goes retro – with a much greener outlook. It is a very long read, so here is the usual tl;dr summary (edited quotes).

• If you want poor countries to become richer you need a cheap and abundant power source. But if you want to avoid spewing out enough extra carbon dioxide to fry the planet, you need to provide that power without using coal and gas.
• The standard alternatives simply wouldn’t be sufficient. Wind and solar power by themselves couldn’t offer nearly enough energy, not with billions of poor people trying to join the global middle class. Yet conventional nuclear reactors – which could meet the need, in principle – are massively expensive, potentially dangerous and anathema to much of the public (not to mention politicians).
• But, the molten salt reactor (MSR) might just turn nuclear power into the greenest energy source on the planet.
• They are basically a pot of hot nuclear soup – a mix of salts, heated until they melted, and a salt such as uranium tetrafluoride stirred in.
• The uranium will undergo nuclear fission in the melt, keeping the salts molten, and providing power generation at the same time.
• Oak Ridge National Laboratory in Tennessee successfully operated a demonstration molten salt reactor back in the 1960s.
• They demonstrated that molten salt reactors were cheap enough for poor countries to buy and compact enough to deliver on a flatbed truck.
• They’re also green as they will burn our existing stockpiles of nuclear waste, rather than generatign even more.
• And they’re safe enough to put in cities and factories.
• Even better these reactors would be proliferation resistant, because their hot, liquid contents would be very hard for rogue states or terrorists to hijack.
• Getting there isn’t going to be easy – not least because hot molten salts are just as corrosive as they sound. Every component that comes into contact with the brew will have to be made of specialized, high-tech alloy that can resist that corrosion. While you want to dissolve the uranium in the salt, you do not want to dissolve your rector as well!
• As one specialist has observed: “It will be exceedingly hard, but that is significantly better than impossible”.
• The approach that won out for commercial power production – and is still used in almost all of the 454 nuclear plants currently operating globally – is the water-cooled uranium reactor (WCUR).
• WCUR isn’t the best nuclear design, but it was one of the first. Other designs were left for later (if ever).
• Oak Ridge successfully demonstrated all this in their MSR, an 8 megawatt prototype that ran from 1965 to 1969.
• By the early 1970s, the Oak Ridge group was well into developing an even more ambitious prototype that would allow them to test materials as well as demonstrating the use of thorium fuel salts instead of uranium.



• Officials in the US nuclear program terminated the Oak Ridge programme in early 1973. However MSR started to appear less visionary in 1974, when India tested a nuclear bomb made with plutonium extracted from the spent fuel of a conventional reactor.
• Governments around the world realised global reprocessing was an invitation to rampant nuclear weapons proliferation. In 1977 US President Jimmy Carter banned commercial reprocessing in the United States; much of the rest of the world followed.
• This left a nasty disposal problem. Instead of storing spent fuel underwater for a few years, engineers were now supposed to isolate it for something like 240,000 years, thanks to the 24,100-year half-life of plutonium-239. (The rule of thumb is to wait 10 half-lives, thus reducing radiation levels over 1000-fold.)
• Developers at Oak Ridge tried to point out that the continuous purification approach could solve both the spent-fuel and proliferation problems at a stroke; but they were ignored by the nuclear planners.
• Then in 1979 came the partial meltdown at Three Mile Island, a conventional nuclear plant. In 1986 another catastrophe hit meltdown at the Chernobyl plant in Ukraine.
• The resulting backlash against nuclear power was so strong that new plant construction effectively ceased, the nuclear industry stagnated and was not in an innovative mood for 30 years.
• Then in 2011, a tsunami knocked out all the cooling systems and backups at Japan’s Fukushima Daiichi plant causing the 1970s-vintage reactors to meltdown.
• Seaborg Technologies launched in 2014 to design a molten salt Compact Used fuel BurnEr (CUBE) that would run on a combination of spent nuclear fuel and thorium.
• CUBE is also so small that it can be transported to site on the back of a truck – a major advantage especially in remote regions.
• Unfortunately none of this is going to happen tomorrow. The various MSR development companies are still refining their designs and the first prototypes won’t be running until at least the mid-2020s.
• But perhaps the biggest, and most unpredictable barrier, is the public’s ingrained fear of anything labelled “nuclear”.
• So developers have to keep stressing the why of nuclear power: to fight climate change, poverty and pollution. As well as the three big advantages of MSR: no meltdown, no proliferation and burning up nuclear waste
• Apparently people are beginning, slowly, to listen – at least in the USA.

See also Molten Salt Reactors and Wikipedia.