The Thorium Cycle, Part Three

Guardian Council, Going Postal

As we’ve seen in the last chapter, there are two significant advantages of a molten salt reactor over the water boiling reactor range we have today: their fuel mix makes them inherently safer than water-cooled systems and they lend themselves to easy miniaturisation, which conventional systems do not.

Remember those futuristic looking ads in the 1950s for the atomic car? Or the nuclear reactor that would heat, chill and light your home? We used to laugh about them because we’ve grown up in a world where there was supposedly “no alternative” to the Uranium-235 cycle with light or heavy water as coolant and/or moderator and its resultant vast containment vessels.

This is down to the fact that with pressure remaining equal, water increases its volume by a factor 1,000 in case it evaporates, which it rather would once a light or heavy water reactor’s core went into meltdown (see Three Mile Island or Fukushima for reference).

Containment buildings for a molten salt reactor tend to be very, very small – they’re basically the size of the reactor itself. This appeared to make MSRs suitable for submarines and airplanes. In effect, the first proof of concept for this innovative technology was called the Aircraft experiment and it was initiated in 1946 by the US Air Force.

The ANP (Aircraft Nuclear Propulsion) project operated a 2.5 MW nuclear reactor small enough to fit on a strategic bomber and achieved 1,000 hours in service (although on the ground) in 1954. The military benefit of this technology during the Cold War was obvious: the elimination of any need for refueling intervals meant a strategic bomber fleet could be continuously airborne.

The reactor was joined to two General Electric J47 engines and the project ran the three prototypes HTRE (Heat Transfer Reactor) 1, 2, and 3 until being abandoned in 1957.

This same year, Pratt and Whitney started their Aircraft Reactor-1 at the Oak Ridge facility in Tennessee, but this was mainly an engineering test to see whether their product could withstand operating temperatures of around 680°C, which it did.

The first flight with an operating 3 MW nuclear reactor on board was the NB 36-H Nuclear Test Aircraft (NTA) in 1951. The main purpose of its then 47 sorties over Southern Texas and New Mexico was shield testing; the reactor couldn’t supply the aircraft with power for propulsion because any such technology was still years away.

The NTA spent 215 hours airborne, during which the reactor was operating for 89 hours. To shield the crew from radiation, the original flight deck was replaced by a lead-and-rubber-lined nose section that weighed 11 tons. Even the standard windows had to be replaced with ten-inch-thick lead glass.

The result of this testing and engineering effort was the USAF deeming it very dubious indeed whether any crew could be sufficiently shielded from radiation, ever. Along with all projects for nuclear aircraft propulsion, the ads for atomic cars and kitchens were quietly discontinued when JFK came into office.

All was not lost, because parallel to the USAF’s project, the National Laboratory at Oak Ridge, Tennessee, started its research in the new and innovative field of molten salt reactor technology.

Oak Ridge had already built the first practical light water reactor by the late 1940s (for use on US Navy ships and subs) and had designed portable reactors for the US Army in 1953, for use during deployment to remote locations were electricity, or indeed any energy supply was not a given.

All this rather changed with Kennedy, as all nuclear research was now to be presented as a gift to the world and the whole of mankind, in a rather ostentatious display of US leadership in all things moral. This early bout of virtue signalling led to the “Water for Peace” programme, and the molten salt reactor experiment was subsumed under this newer, kinder policy.

Research in light- and heavy-water U-235 technology continued apace, of course. This must have been down to the fact that the Thorium cycle rather doesn’t lend itself to the easy production of weapon grade Uranium or Plutonium because it produces large amounts of U-232, which is not fissile and must be chemically removed during enrichment in rather time consuming, complicated and inherently dangerous procedures.

In the eyes of the US military industrial complex, this killed the Thorium cycle stone dead. It became to be considered as of no practical use to the strategic defence efforts of the US and indeed the Western world, which by then ended a few short miles behind Brunswick, Germany.

I suppose it’s fair to assume that the battle against Communism had to be won at all costs, and could only be won with Plutonium production from U-235. If JFK’s bleeding-heard liberal propaganda effort could win it with “Water for Peace”, the US military wouldn’t stand in his way, as long as they could have enough Plutonium to wipe out mankind twice over.

This is probably the line of thinking that led to the molten salt experiment being subsumed under Kennedy’s propaganda efforts of presenting the USA as a gift to the world via “Water for Peace”.

The MSR was now meant to be a practical application that could power desalination plants in the Third World; and a very rational idea it was too, because desalination requires vast amounts of cheap energy, while in many parts of the world, clean and safe drinking water is much more of an urgent necessity than enough electricity to keep as many household appliances as possible running at once.

Besides, the need for running and maintaining the technology would draw its host nations into ever closer partnership with the US, which cannot have been an altogether undesirable effect.

Guardian Council, Going Postal

Enter Alvin Weinberg, Director of Research of Oak Ridge National Laboratory, the brains behind the whole molten salt operation. Under his leadership, a 7.5 MW prototype was set up, run successfully for about three years on a mix of Lithium, Beryllium and Zirconium Fluorides, with the odd bit of Uranium Tetrafluoride as a source of nuclear energy thrown in.

The reactor went critical on U-235, but later its salt mix was partially shifted towards U-233 to prove that breeding Thorium-232 into U-233 would indeed produce a viable nuclear fuel source. The MSR at Oak Ridge had no facilities to breed U-233 from Thorium-232 on site. The piping and the reactor core were made from Hastelloy-N, a steel alloy especially produced for the nuclear industry.

The prototype operated for the net worth of 1.5 years during 1965 and 1969, while its liquid salt circulated in a continuous loop from the reactor to the coolant pump, to a heat exchanger, to the fuel pump and back to the reactor. In case of an emergency due to overheating, a Fluoride plug at the bottom of the reactor vessel would have molten, releasing all the liquid salt in to five separate underground storage tanks, where the chain reaction would have broken down instantly and the salt would have cooled off.

The MSR experiment got disbanded and Weinberg got fired during the Nixon years. Apparently, funding was already reduced towards the end of the 60s, with ORNL’s budget now going into particle acceleration, fusion research and of course the Apollo program, which promised much more bang for the buck propaganda wise than “Water for Peace” ever could, obviously.

No commercial application of the MSR was built, though in hindsight this would have been the next step towards introducing this novel kind of technology. So, in many regards, it is fair to say that Alvin Weinberg became a victim of his own success as well as a victim of the US military and industrial complex, which had partly enabled Weinberg’s success in the first place.

The other thought leader in the field besides Weinberg was an Indian gentleman named Homi J. Bhabha. In 1930, Bhabha got a first-class Mathematics degree at Cambridge where he studied under Paul Dirac, among other leading experts in their field. After the war, Bhabha returned to his native country and led the effort to supply the subcontinent with nuclear power.

This was an obvious aim, but in the case of India it meant making do with what you’ve got, and making the most out of it, too. Because India is rather poor in Uranium ore, yet rather rich in Thorium, the latter appeared to be the nuclear fuel of choice.

In a first phase, India would enter the field of nuclear power with reactors that ran on U-235, to later make the shift to fast breeder reactors which could also provide for the nation’s military needs. Once this was achieved, India would establish nuclear power generation based on the Thorium cycle, which Bhabha considered the obvious choice for all civilian applications of atomic power.

This “Three Stage Plan” previsioned a generation of 8,000 MW by the year 1980; current energy generation from nuclear sources is at around 3,300 MW p.a. in India.

Bhabha’s vision was far-fetched, overly optimistic and a bit too aspirational considering the realities on the ground, but it was vindicated nevertheless: India is currently operating the world’s only fast breeder reactor in Kalpakkam, near Madras (after the US, France, Britain and Germany have long given up on this technology), and India is ready to build a 300 MW reactor that will use Thorium as its main source of nuclear fuel, though not in an MSR but in an advanced heavy-water system based on a pressurised heavy-water design.

There are significant development efforts in the field of the MSR and/or Thorium breeding underway in China and Japan, while all European nations and the US have taken pretty much of a back-seat position towards the whole thing; they are after all heavily invested in “renewables”, and too sudden a change of tack might upset a few private and/or public finances.

Therefore, although its feasibility and practicality has been shown fifty years ago, and its practical benefits are about as convincing as they ever were, the MSR died at the hands of military planning during the Cold War, which considered the U-235 reactor a much better asset because it would breed enough Plutonium to produce all the bombs we would need to wipe out mankind twice over. The MSR became a lost case for the West. Other nations will reap its rewards, and rightly so.

© Guardian Council 2018