Why the molten salt reactor should be our next big thing for terrestrial and extra-planetary needs

A new type of nuclear reactor could help advance efforts to develop space nuclear power and propulsion systems (credit: NASA)

by Ajay Kothari
Monday, August 1, 2022

Addressing climate change, especially reducing carbon dioxide emissions while also producing the necessary energy, is engaging humanity around the world and is likely to further engage the Biden Administration and its successors. When developing various technologies, one must also consider another potential solution that is much simpler, cheaper and faster to implement, while waiting for other solutions such as controlled fusion. In the last year France Y some EU countries announced their intention to switch to nuclear power for their energy needs. China also prepared to test a thorium fueled nuclear reactor in September 2021, although no information on test results has been available since then.

“Nuke” has become a four-letter word due to earlier designs using uranium-235 as a solid fuel – an incorrect reactor design due to the need for plutonium for nuclear bombs in the 1960s. We don’t need them to the same extent. They should be phased out: surely not good news for today’s nuclear industry, but frankly, it shouldn’t matter. That was then, this is now. We are in a different situation now, and with different priorities related to climate and energy. We need a rethink.

Nuclear power was touted as an incredible source of nearly infinite energy for mankind in the 1950s. But even in a controlled form like nuclear reactors, it seemed dangerous with an almost constant threat of explosion due to 200 to 300 volt pressure. atmospheres needed to keep the coolant water in liquid form, which required a high degree of monitoring and double to triple redundancy, increasing the cost is enormous, as it still is in most reactors around the world, as the vast majority of them are light (or heavy) water reactors (LWRs). Those dangers were correctly foreseen with the events of Three Mile Island, Chernobyl, and Fukushima. What if this threat can be removed?

What if we can find a solution that doesn’t need those high pressures? We may have. More specifically, it is the thorium molten salt reactor (TMSR) or the Liquid Fluoride Thorium Reactor (LFTR), the important denominator being thorium dissolved in hot molten salt which is not used as a refrigerant, but as a source of energy, operating at nearly sea level pressure. And thorium leaves behind only 1% radioactive isotopes, as opposed to 95% for U235. What more do we want?

Why can’t we conclude that the way we did it was wrong instead of the act? Now is the time to implement it. Give engineers the ability to design it.

Thorium, 232Th, is 500 times more abundant than 235U and offers a significantly different and better solution. It is no longer the nuclear of our grandparents. It’s very different. We as a country have to investigate it.

The binding energy of the strong nuclear force offers almost a million times more energy per kilogram than the chemical release of fossil fuels, which is based on electrons. We were unable to tap into this potential until now. Now we can. In the last 50 years, consequently and unfortunately, we had to go the fossil fuel route, adding not only carbon dioxide but also deadly pollutants to the air. We don’t need coal, oil or fracking. With this solution, offering 24/7 power, combined with even intermittent terrestrial solar and perhaps wind power, we can solve our problem of needing power for a thousand years with zero addition of carbon dioxide.

One ton of thorium is roughly equivalent to five million barrels of oil. It will operate a 2.6-gigawatt thermal plant for a full year. With 50% efficiency built in for conversion, it will provide 1.3 gigawatts of electrical power. About 600 to 800 such plants will provide all the energy we need in this country, so about a thousand tons of thorium will be needed per year, without adding carbon dioxide or other pollutants to the air. With US reserves of 595,000 tons of thorium, we have enough to last us 600 years at current rates. By then, there is little doubt that we will have cracked the riddle of controlled fusion, giving us a long shot at life.

This vision will solve the world energy problem a thousand times with zero carbon dioxide emissions during operation, and may be the cheapest form of energy production for us. The time has come to take advantage of this technological marvel. It would not be fair to deny ourselves, and perhaps other countries, a future. One hopes that this administration will heed it and find a reasonable path for all of us.

And this promise extends into space. With the molten salt carried through the pipes to where it’s needed (unlike NERVA), we can now first transfer heat (Heat Exchanger 1 in the image below) to a non-radioactive molten salt and then use it to heat hydrogen. via Heat Exchanger 2 Rocket nozzle exhaust will then be non-radioactive hydrogen gas with ~700 seconds specific impulse and much lighter as no high pressure containments are needed, making the combination attractive at the system level. While not used for the booster stage of the rocket, the upper stages could become viable candidates for propulsion.

Almost more importantly, having reached an off-planet destination (the Moon or Mars, for example), this upper-stage reactor can be reused to provide thermal power or electricity using a closed-loop carbon dioxide turbine cycle for habitats. or teams.

It is possible to fly a rover on Mars using the heat generated via TMSR at subsonic speeds without the need for combustible fuel. This may promise immense potential for access to anywhere on Mars without chemical propellant extracted from Earth. Just 10 grams of Th232 will fly the rover through a full orbit around Mars! This could be very useful for future Martian colonies for experimentation, mapping, and transportation.

Thorium has also been detected on the Moon by Chang’e-2. For starters, a kilogram of thorium taken from Earth can support a 2.6-megawatt thermal plant for a year. Imagine ten such plants in ten different locations with ten kilograms of thorium taken from Earth and associated salt, eventually becoming self-sufficient with lunar thorium.

A necessary solution would be for the political class to lead and the anti-nuclear antagonism (against the word “nuclear”) at least dissipate and realize that the vehemence against it is hurting billions of people of color around the world. through pollution while keeping us away. of a carbon-free future.

Let’s start small. A few small, even university-level plants can help fix the problems to begin with, and then slowly expand over the next decade to provide our country with fossil-free energy to begin with. Sharing this technology, or not, with other countries is above my pay grade and would be left to management to decide.

Dr. Ajay Kothari is president and founder of Astrox Corporation, an aerospace research and development company located in suburban Washington, DC. His PhD and MS in aerospace engineering with a concentration in physics are from the University of Maryland and his BS in physics is from the University of Bombay.

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