Nuclear reactors running on thorium are widely held to be inherently safer than the awful pressurized-water reactors we have today. So why don’t we have thorium reactors? A new TV documentary also available online answers the question quite well. Craig Morris sums up the evidence.
The documentary in French and German (but available with English subtitles) aired in October on the Franco-German TV station Arte. The film clearly calls for tremendous investments in thorium nuclear, with a prototype reactor costing “a billion euros.” Proponents of the idea quoted in the film put this amount into perspective: Goldman Sachs paid 16 billion dollars in bonuses in 2010 alone. The documentary thus is an ad for thorium and cleverly begins with one in order to appear more objective; a comic strip version of the late nuclear expert Alvin Weinberg tells viewers he is sick of ads and asks whether we are ready to take a deep dive into the technology.
The documentary’s sales pitch is convincing, and I do recommend the movie to anyone who wishes to know what thorium nuclear reactors are (or would be) and why we don’t have them. The benefits are clearly explained:
- Radioactive waste would be reduced by around 80%, much of which would only have a half-life of seven years.
- During operation, the reactors would probably be inherently safe. The problem with the reactors we currently have is that they need cooling even when they are shut down or break, as happened in Fukushima. When a thorium reactor cooled with molten salt has an emergency shutdown, the liquid salt can be dumped into a reservoir under the reactor, where it would quickly cool down enough to harden so that leaks would not even be a problem.
So why don’t we have such reactors? The reason given in the film is the one we also give in our book, Energy Democracy, in telling the history of nuclear in Germany. Basically, the first nuclear reactors were actually built to produce material for nuclear weapons. The nuclear power plants we have today were derived from this design. In fact, the one that blew up in Chernobyl was technically a military reactor repurposed for power production.
Once this reactor type had become the utility favorite, other competing designs were discouraged. Utilities and the government did not want potentially safer reactors to succeed, lest the public demand the immediate shutdown of the reactors already built, which have the worst possible design of all the options originally on the table.
The Germans also played around with thorium. Strangely, the documentary does not tell the story of Germany’s thorium reactor in Hamm from the 1980s, probably because it is not exactly the kind proposed (for instance, the German one used helium, not molten salt, for cooling). But Germany also had a reactor with sodium as the coolant in Kalkar.
The thorium reactor ran for just over a year and was closed because of rising costs (basically, it broke). The other was also closed based on cost, but it never had time to break. With the molten sodium flowing through the cooling system and the reactor ready to be loaded with fuel rods, the state government refused to give the go-ahead, and the plant operator eventually gave up because keeping the sodium heated up as a liquid was costing millions of deutsche marks every day.
Do either of these German examples provide any lessons?
The Chinese have also tried their hand at the kind of thorium reactor described in the movie, and they could not quite get the technology to work either. But the problems could be manageable; the reactor design does not pose any obstacles that might not be solved through trial and error. The big one – and the one that plagued the Chinese – is corrosion from the molten salt. But this challenge is well understood today and already managed in other industry facilities, including concentrated solar power plants with molten salt storage. For what it’s worth, the IAEA claims that “no technological breakthroughs are required” for the corrosion issue (PDF).
So should we go ahead with thorium? As the Chinese and German examples show, more than one prototype will be needed. If each one comes at a price tag of 1 billion euros, we are talking about a lot of money. Maybe Goldman Sachs could pay for all of this out of the kitty, but that doesn’t mean thorium is the best option.
Even if they work as touted, thorium reactors would still produce some nuclear waste – and frankly, it’s not completely certain they would be inherently safe if there were an accident. Finding that out would cost billions. By the time we figured that out, the falling cost of solar + wind + storage would, no doubt, make thorium uninteresting. And we already know for certain that renewables are inherently safe.