a bonobo humanity?

So what about thorium as part of our clean energy future? Are there any thorium reactors operating? How do they work? How do they compare to uranium-based reactors?

Well, there appear to be a lot of plans on drawing boards, for good reason, it seems. Thorium is about three times more abundant than uranium, and is potentially a safer source of nuclear energy, which, ironically, is largely why it was overlooked early on, due to uranium’s far greater weapons potential. To quote Wikipedia,

The Thorium Energy Alliance estimates “there is enough thorium in the United States alone to power the country at its current energy level for over 1,000 years.”

When used in a liquid fluoride thorium reactor (LFTR), a type of molten salt reactor (MSR), far less nuclear waste results. And there are many other positives. An estimate by Nobel Prize-winning physicist Carlo Rubbia, for example, that a ton of thorium can produce the energy of 200 tons of uranium and three and a half million tons of coal.

And there’s more stuff about thorium’s advantages that sound just too good to be true. Wikipedia lists nine positives in bullet points. However, there are substantial start-up costs, and there are problems with ‘breeder reactors’ and proliferation, which I’ll try to understand later.

Reading the story of uranium v thorium from the late forties into the seventies, you can clearly see that the military side of the military-industrial complex, especially in the USA, won out at the expense of safe commercial and domestic energy use. But what with the recent urgency about alternatives to fossil fuels, and the concern (methinks largely unwarranted) about uranium-based nuclear, thorium is inching its way back into favour. Sabine Hossenfelder reports on its soon-to-be-arrival in Europe while castigating the German state’s pulling the plug on nuclear in general (Steve Novella of the Skeptics’ Guide is also bemused). I reckon they’re gonna change their changed mind eventually.

Anyway, the news is that the Netherlands and France, two countries that embrace nuclear power, have teamed up to bring small thorium reactors to Europe. NAAREA, a French alternative energy company, and Thorizon of the Netherlands, have combined their smarts and funds, and I’ll quote Sabine:

NAAREA is already working on small nuclear reactors, and they want to combine their technology with the thorium cores from the Dutch.

This is the concept of small, transportable nuclear reactors that I first read about in Steven Pinker’s Enlightenment Now some years ago. The fact is, though, that progress seems to be slow in this field, in spite of all the global warming concerns. NIMBYism is still a problem, as well as whole of government negativity, as in Germany. Nations that are more keen are India, which has the world’s largest thorium reserves, China, Canada and the USA.

So what about here in Australia? We have actually banned nuclear energy, both federally and in every state and territory, and there appears to be no appetite for changing the situation. This also means there’s no avenue for those interested in nuclear energy and its engineering and technical requirements to gain expertise in the field here. I suspect the only factor that will change our governmental (and popular) mindset will be the proven success of new thorium-based reactors elsewhere. Of course, Australia has the perfect climate for solar and storage, so there’s little appetite for changing direction – though it should be noted that Australia ranks with the USA as having the third largest reserves of thorium, behind India and Brazil.

So how does thorium work as a nuclear fuel? I’ve no idea, so here goes with another particle of my lifelong learning. First, to the World Nuclear Association. Three points:

• [Thorium] is fertile rather than fissile, and can only be used as a fuel in conjunction with a fissile material such as recycled plutonium.
• Thorium fuels can breed fissile uranium-233 to be used in various kinds of nuclear reactors.
• Molten salt reactors are well suited to thorium fuel, as normal fuel fabrication is avoided.

The first point is sort of self-explanatory – thorium nuclei (232) can’t be split apart by ‘thermal neutrons’ (neutrons travelling above a certain velocity), but they can be converted into fissile material via ionising radiation. The nuclei may then capture neutrons and be converted to fissile material (uranium-233, in the case of thorium).

The third point obviously needs some explaining. The reactors used to generate thorium-based energy are called liquid fluoride thorium reactors (LFTRs), which are:

a molten salt type of reactor [MSR], meaning that the fuel inside the core is actually in a liquid form in a salt formation that circulates inside the core. It is hot and acts as a fuel and coolant at the same time, meaning that the heat from this liquid fuel that is circulating inside the core is being transferred to the heat exchanger and to the rest of the components and electricity is produced similarly to any other type of reactor.

Elina Charatsidou (see references)

That’s a start. The differences between this type of liquid fuel and the highly structured solid fuel rods create both advantages and disadvantages…

So, as mentioned, thorium-232 is quite abundant and, unlike uranium-235, it isn’t fissile (which makes it similar to uranium-238), but its ‘fertility’ allows it to capture neutrons, so transmuting into protactinium-233 which then decays into uranium-233, which is fissile. This, I think, is the important point. It’s the splitting of the uranium-233 that produces the efficient energy, not thorium itself. And Elina points out something I don’t quite understand as yet – ‘there are 2 ways that can be produced – uranium-233 can be produced inside the core, or outside and then placed inside the core as a fuel for the thorium reactors’.

Ultimately, though Elina Charatsidou and other informed commentators aren’t quite buying into the hype of some about a thorium future. It should be developed, and it’s needed as our population continues to grow and, more importantly, become more prosperous. We need to get behind it as part of a multi-faceted approach to our energy future.

For a more positive spin on thorium and new developments in nuclear energy, especially regarding storage, re-use, corrosion and cost factors, as well as issues around public-private ownership, the Copenhagen Atomics video, linked below, is well worth a look.

References

https://en.wikipedia.org/wiki/Thorium-based_nuclear_power

Good News: Small Nuclear Thorium Reactors are Coming to Europe (Sabine Hossenfelder video)

Steven Pinker, Enlightenment Now, 2018 (pp146-9)

https://world-nuclear.org/information-library/current-and-future-generation/thorium.aspx

Nuclear Physicist Explains – What are Thorium Reactors?, Elina Charatsidou video

THORIUM: World’s CHEAPEST Energy! [Science Unveiled] (Copenhagen Atomics video)