Posted by Mark Halper

The journal Nature says superior, alternative nuclear technologies such as the liquid thorium molten salt reactor that Kirk Sorensen (pictured) is developing at Flibe Energy could be the ticket to a carbon-free energy future.

Alternative nuclear technologies that are superior to and safer than conventional nuclear could play a huge role in addressing the world’s energy and climate change crises, and help rebuild nuclear’s standing post-Fukushima.

But don’t just take our word for it.

This week’s edition of the esteemed journal Nature rolls out the carpet to welcome the new approaches that we’ve been writing about here at Weinberg since we launched our blog in September – including thorium fuel as well as molten salt reactors, pebble bed reactors, fast reactors and others. None of these are new per se, but lost out some 40 years ago to an inferior technology.

In an articled entitled Nuclear energy: Radical reactors, author M. Mitchell Waldrop notes, “For decades, one design has dominated nuclear reactors while potentially better options were left by the wayside. Now, the alternatives might finally have their day.”


The “one design” that has ruled, of course, has been the solid uranium fuelled, water-cooled reactor that today can cost $10 billion to $15 billion to build. Those reactors have prevailed “not because they were best, but because they were first,” says Waldrop in a comprehensive story that reads in places like a retelling of Richard Martin’s thorium homage, SuperFuel.

Now that’s set to change, Waldrop asserts, as alternative designs reduce and even eliminate meltdown risks; leave less long lived waste and in some cases turn waste into fuel; reduce costs; and just as key, provide a valuable clean heat source that can help fuel high temperature industrial processes that today spew CO2.

The meltdown-proof liquid thorium molten salt reactor (MSR) that Kirk Sorensen is developing at Flibe Energy, for example, includes a “freeze plug” that thaws and allows fuel to drain into a safety tank in the event of an emergency.

MSRs also operate at much higher temperatures than conventional reactors, as do other alternative “high temperature” designs such as  we’ve been writing at Weinberg – including Steenkampskraal Thorium Ltd’s thorium fueld pebble bed reactor and several initiatives in China.

Higher operating temperatures – as high as 1,000 degrees C – offer several advantages over 300 degree C conventional reactors, notes Nature. Among them: they make more efficient use of fuel, and industry can tap them not just for electricity, but also for process heat.


“They could slash carbon emissions by supplying heat for industrial processes,” writes Waldrop. “In the United States, roughly 23% of all energy is used in industrial applications such as petroleum cracking and plastics manufacture,many of which need temperatures of at least 700 °C. Currently, those temperatures tend to be generated by burning natural gas; high-temperature reactors could provide a zero-carbon alternative.”

The story notes that Dow Chemical Company is keeping a close eye on the Antares high temperature reactor that France’s Areva is developing.

“If all goes to plan, high-temperature systems will be among the first advanced reactors to be deployed, starting in the 2020s,” Nature states.

Nature also points to a revival in “fast” reactors – a concept popular in the 1970s that failed to catch on- that would use nuclear waste as fuel. As we noted here, Russia has recently scaled up its plans to build fast reactors.

Another encouraging sign in the article is that – as Weinberg wrote earlier this week – the U.S. is funding small “modular” reactors that will lower the upfront costs of nuclear.


Per Peterson, the University of California Berkeley nuclear engineering head who is a big supporter of alternative nuclear, noted that the U.S. Department of Energy’s funding of Babcock & Wilcox’s SMR indicates a changing mindset to alternative designs in general.

“If we can generate a market for light-water small modular reactors,” Peterson says, “that makes it much easier to develop a market for prototype advanced reactors.”

All of these technologies will come with their own technological challenges and criticisms.

A companion piece in Nature raises concerns that someone could irradiate raw thorium into uranium 233 to make a bomb. That prospect strikes us as unlikely since the process would entail exposure to instantly lethal uranium 232 (the opinion essay says the amount would be “minimal” – but a little bit of a lethal thing like U232 is still lethal). A U.S. attempt to make a bomb from U233 in the 1955 Operation Teapot essentially fizzled. Also, the enriched uranium that powers today’s reactors can be fashioned into a bomb, so it seems that the same strict regulations that govern its handling should also govern thorium’s.

Aside from weapons proliferation issues, as Nature’s main story points out, “Reviving the technologies will not be quick or easy. Although the basic designs were worked out decades ago, engineers hoping to put them into practice must develop things such as radiation-resistant materials, more-efficient heat exchangers and improved safety systems — and must then prove to regulators that all these systems will work.”

Momentum is slowly building. Peterson – the UC Berkeley developer of alternatives – chaired the annual American Nuclear Society gathering in San Diego, which was full of sessions on high temperature and other unconventional designs.

With publications like Nature – the world’s most cited interdisciplinary science publication – on board, the alternatives movement has just come a little closer to the new normal.

Photo from Thorium Energy Forum.


  1. Robert Hargraves says:

    The book, THORIUM: energy cheaper than coal, has a lengthy discussion of the difficulties of perverting commercial liquid fluoride thorium reactors to make weapons. It concludes that a nation intent on becoming a nuclear power would not bear the cost and technical risk of inventing and manufacturing a new weapon but choose the well-known technology route trod by North Korea, India, and Pakistan — centrifuge uranium enrichment or plutonium production with frequent fuel changes in a graphite or heavy water reactor. In fact the single fluid denatured molten salt reactor version is more proliferation resistant than today’s light water reactors. Note that Iran has just removed fuel rods from its new LWR after only 2 months instead of 18, sacrificing power generation to harvest high purity weapons-grade plutonium before it is degraded to reactor-grade plutonium. The world needs to look at the big picture of energy demands, environmental degradation, and conflict risks; highlighting small risks is counterproductive. Thorium provides affordable, safe, universal energy security for all nations and so will reduce resource contention that leads to conflicts requiring weapons.

  2. Martin Kral says:

    Mark, if you know any of the people in this report, I think you have the creditable background to talk to them. It would be great to get the thorium solution into the series. Just thinkering again.

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