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A model of a molten salt reactor that could use thorium to generate electricity and offer an alternative to space-based solar energy. |
by Ajay Kothari
Monday, September 13, 2021
Space-based solar energy (SBSP) is being touted as a solution to the climate change problem currently preoccupying humankind around the world, and will keep that administration even more preoccupied in the future. When developing this technology, one should also consider another potential solution that may be easier, cheaper, and faster to implement, and that could be used faster while we wait for other solutions like SBSP and controlled fusion. It could also find application as a distributed source of energy on the lunar surface and later on Mars. Its possible application to rocket engines should also be determined, but is not the focus of this comment.
That potential solution is the Thorium Molten Salt Reactor (TMSR) or, more precisely, perhaps the Liquid Fluoride Thorium Reactor (LFTR), where the important denominator is thorium dissolved in hot molten salt, which is used as an energy source rather than a coolant.
advantages and disadvantages
Thorium (Th232) is abundant. It is three to four times more abundant than mined uranium, which contains 0.7% U235 and 99.3% U238. Since only U235 is fissile, while the entire degraded Th232 is fertile, the ratio then becomes much larger: almost 500 times more frequently.
Thorium is fertile but not fissile, so it is not radioactive either.
It goes without saying that the carbon dioxide emissions from this energy production would be zero, which is politically highly desirable in today’s environment. But as Andrew McAfee of the MIT Sloan School put it, “We are not using our best weapons to fight global warming.”
| It could also find application as a distributed source of energy on the lunar surface and later on Mars. Their possible application to rocket engines should also be determined. |
In addition to carbon dioxide, there is a threat to many poorer countries: pollution. Pollution in China, and especially India, is already cutting healthy lives for millions of people as fossil fuels, including lots of coal, are burned. It really is a terrible situation right now. TMSR can go a long way towards providing relief. China has just announced plans to build 30 such reactors. However, India, with the greatest reserves of nearly a million tons, has not published any such plans, which is amazing and even terrifying.
In contrast to the light water reactors (LWR), which are most reactors worldwide, no 200 to 300 atmospheres pressure are required to keep the cooling water in liquid form. Instead, it works with a couple of atmospheres. This means that there is no need for a high pressure dome with the associated threatening malfunctions such as in Fukushima or Chernobyl. This is a big plus.
The big positive above comes with a negative factor. The temperature of liquid salt is now much higher at 600 to 700 degrees Celsius. which would lead to a corrosive effect on the containment. However, it also has the advantage that the steam and power generation from turbines is done with a higher efficiency of almost 45%, in contrast to LWR, where it is about half as high.
If the temperature of the liquid rises higher than planned due to an unexpected circumstance, the distance between the nuclei will increase, reducing the impact of these thermal neutrons, thereby reducing the fission of U233. More on that later.
If that doesn’t happen quickly enough, a freeze valve installed below melts, floods the safety containers below and automatically cools the fissile fuel. Frozen TMS cannot cause a split. This is also a huge accident insurance.
The lack of the required pressure containment, resulting in a thick, heavy structure for LWRs, also results in much lighter and smaller equipment, making them portable. It may also lend itself to use in missiles and aircraft, which changes the paradigm compared to the 1960s when similar nuclear applications were last studied.
MSRT will burn approximately 99% of the thorium fuel into safe and even medically useful by-products. This would even mean reducing the existing nuclear waste by more than 90%, some of which forms the seed for the start of the first neutron source.
Since this reaction requires neutrons to start the process, what better way than to use up (albeit slowly) the residue that remains in places like Yucca Mountain? Yes, it will also help reduce those horribly long half-lives that we can’t do anything with. Now we can.
Granted, there is another disadvantage. Terrorists or opponents could break in and break the freezer valve, causing all of the ingredients to fall into the drainage container. However, the mixture would solidify at lower temperatures and become unusable as a solid. There is also a poison pill. The U233 will contain traces of U232 with its accompanying gamma rays, enough to disable the handler. To make a U233 bomb, it would also have to be separated from the molten salt and enriched.
| This vision will solve the global energy problem thousands of times (for thousands of years) without any carbon dioxide emissions during operation. |
We have been on this train with U235 enrichment control before and could do the same. We have not banned countries from producing their own nuclear power. They do it: 36 of them with almost 440 nuclear power plants in operation worldwide. And whether we move as a country to implement this technology or not, many poorer countries will build it to get cheaper electricity for their people and to hedge their bets against the availability of oil and the reduction of air pollution. China has a large program of TMSR technology development and will likely overtake us in a few years. Our fate could then also consist of simply being left behind here as well as possibly in cislunar space. We may need another Elon Musk or many Kirk Sorensens to accept the “Thor” badge, but a better solution would be if the political class woke up and the knee-jerk anti-nuclear activists at least saw their vehemence against these technologies Pollution harms millions of people of color, blacks and browns, worldwide.
How thorium can be used to generate electricity. (Credit: Credit: Kirk Sorensen, Flibe Energy) |
How does it work?
One of the forces that physicists have long tried to unite in the United Field Theory is of course the strong nuclear force, which is sufficient to overcome the repulsive electrostatic force of the protons bound in a nucleus. This binding energy contained in a nucleus is the blessing of nuclear power, in this case nuclear fission. During the fission, about 200.1 MeV of energy are released per atom of U233. This is a million times higher per unit mass than chemical sources such as those produced by burning fossil fuels or coal.
A thorium atom, Th232, when bombarded by a neutron from an external source, absorbs that neutron and creates Th233, increasing the atomic weight by one but not the atomic number. Since it is unstable, beta decay transforms it more or less immediately into Protactinium Pa233 with a half-life of 22 minutes. It continues to break down over 27 days to form U233, which is fissile. This atom splits into strontium and cenon atoms, releasing almost the same energy per atom as U235, 200.1 MeV.
How much do we need
One ton of thorium is roughly equivalent to five million barrels of oil. As a result, the world’s total thorium reserves of around six million tons are equivalent to 30 trillion barrels of oil reserves, while the world’s total oil reserves are around 1.8 trillion barrels.
Worldwide electricity demand is around 55 billion gigajoules per year. This means that 667 tons of thorium per year can meet this demand. Given the efficiency of energy conversion, it may be two to three times that, but with 6.3 million tons of thorium reserves worldwide, we have enough for several thousand years. With almost 600,000 tons of thorium reserves in the USA alone and our electrical energy requirements of around 21 billion gigajoules per year (or 666 one-GW systems), we have enough for many hundreds of years without oil or gas imports. Within this timeframe, it is obviously plausible to assume that we would have solved the controlled merger problem.
| We don’t have to build tens of thousands of one-gigawatt SBSP systems in GEO with the associated rectenna on earth and ongoing maintenance work in orbit. |
This vision will solve the global energy problem thousands of times (for thousands of years) without any carbon dioxide emissions during operation. Because the size and pressure requirements are significantly reduced, it can be the cheapest form of power generation for many of the poorer countries. It would not be fair to deny these countries a future.
Moon LFTR?
Thorium from Chang’e 2 has also been detected on the moon. One kilogram of thorium that was initially taken from the earth can provide 2.6 megawatts of thermal output for one year. Imagine ten such plants in ten different locations with ten kilograms of thorium from the earth and the associated salt, which will eventually become self-sufficient with lunar thorium. Only the first such facility needed neutron-producing radioactive material to start the chain reaction. The U233 produced in this way can provide additional neutrons for additional reactors and thus becomes self-sufficient. For electricity on the lunar surface, however, this is only one of the promising possibilities. Different locations may require different solutions, such as B. Beam power from SBSP.
This solution is available to mankind on earth today. We don’t have to build tens of thousands of one-gigawatt SBSP systems in GEO, with the associated rectenna on earth and ongoing maintenance work in orbit! That solution has to be developed here in America. It is now time for us and the rest of the polluted countries to take advantage of this technological marvel. It is to be hoped that this administration will pay attention to this and find a sensible path for us all. Soon.
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