Taylor Wilson is a 19 year-old who is developing a molten salt reactor design. Is there a more in-depth discussion of his design that what is in his TED talk?
Thanks,
XT
April 2, 2014, 9:01pm
3
I didn’t see the Ted talk, but I think China is in the process of developing a thorium based molten salt reactor. Not sure where they are on the project though.
XT
April 2, 2014, 9:04pm
4
Missed the edit window. Here is a quick article on molten salt reactors.
Molten Salt Reactors
Molten salt reactor schematic from GenIVMolten Salt Reactors (MSRs) are nuclear reactors that use a fluid fuel in the form of very hot fluoride or chloride salt instead of the solid fuel used in most reactors. Since the fuel salt is liquid, it can be both the fuel (producing the heat) and the coolant (transporting the heat to the power plant). There are many different types of MSRs, but the most talked about one is definitely the Liquid Fluoride Thorium Reactor (LFTR). This MSR has Thorium and Uranium dissolved in a fluoride salt and can get planet-scale amounts of energy out of our natural resources of Thorium minerals, much like a fast breeder can get large amounts of energy out of our Uranium minerals. There are also fast breeder fluoride MSRs that don’t use Th at all. And there are chloride salt based fast MSRs that are usually studied as nuclear waste-burners due to their extraordinary amount of very fast neutrons.
Benefits of Molten Salt Reactors
The benefits of MSRs are plentiful, hence their resilience as an interesting topic throughout reactor history. We break them down by topic here.
Sustainability is a measure of how efficiently a system can use natural resources. Most traditional reactors can only burn about 1% of the uranium on Earth. Many advanced reactors, including MSRs, can do much better. Here’s why MSRs are good in this regard.
Online fission product removal -- Since the fuel is liquid, it can be processed during operation. This means that when atoms split into the smaller atoms (fission products), those small atoms can be collected and pulled out of the core very quickly. This prevents those atoms from absorbing neutrons that would otherwise continue the chain reaction. This allows very high fuel efficiency in MSRs.
Good utilization of Thorium -- As mentioned above, the MSR chemical plant can continuously remove fission products and other actinides during operation. This means that when Thorium absorbs a neutron and becomes Pa-233, the Protactinium can be removed from the core and allowed to decay to U-233 in peace, without any risk of causing parasitic neutron losses. While this is not the only way to burn Thorium, it is perhaps the most elegant.
No neutron losses in structure -- Since there is no structure like cladding, fuel ducts, grid spacers, etc., there are no neutron losses in these. This helps fuel efficiency and therefore sustainability.
Safety
The most important aspect of a nuclear reactor is safety. Here’s the good news for MSRs:
Very low excess reactivity -- Since they can be continually refueled, there is no need to load extra fissile material to allow the reactor to operate for a long time. This means that it is difficult to have something happen (like an earthquake) that could cause a shift in geometry that inserts reactivity and causes a power spike.
Negative temperature coefficient of reactivity -- In general, if the fuel heats up, it expands and becomes less reactive, keeping things stable. Note that this is not always true in graphite-moderated MSRs.
Low pressure -- Since the fuel and coolant are at atmospheric pressure, a leak in a tube doesn’t automatically result in the expulsion of a bunch of fuel and coolant. This is a major safety advantage that enables passive decay heat removal (preventing things like what happened at Fukushima). The salts generally have extremely high heat capacity as well, so they can absorb a lot of heat themselves. On the other hand, their thermal conductivity is about 60x worse than liquid metal sodium.
No chemical reactivity with air or water -- The fuel salt is generally not violently reactive with the environment. So where LWRs have hydrogen explosions and SFRs have sodium fires, MSRs do well. Of course, MSR leaks are still serious because it’s not just coolant... it’s extremely radioactive fuel.
Drain tank failure mechanism -- If something goes wrong in a MSR and the temperature starts going up, a freeze plug can melt, pouring the entire core into subcritical drain tanks that are intimately linked to an ultimate heat sink, keeping them cool. This is an interesting accident mitigation feature that is possible only in fluid fuel reactors.
Problems with Molten Salt Reactors
All those wonderful benefits can’t possibly come without a slew of problems. Lot’s of people promote these reactors without acknowledging the issues, but not us! A reactor concept has to stand on its two feet even in the face of disadvantages (and we think the MSR can do this). Let’s go through them.
The primary concern with MSRs is that the radioactive fission products can get everywhere. They are not in fuel pins surrounded by cladding, but are just in a big, sealed vat. You can put a double-layer containment around it, sure, but it is still challenging to keep them all accounted for. Where some of these fission products and actinides are radioactive, others have chemical effects that can eat away at the containment. The implications of this are many.
Material Degredation -- with half the periodic table of the elements dissolved in salt and in contact with the containment vessel, there are lots of corrosion and related concerns. Noble metals will naturally plate out on cold metal surfaces. In a power reactor, a heat exchanger will be the coldest metal around, and so the heat transfer surfaces will need periodic replacement. At MSRE, Tellurium caused cracking of the Hastelloy-N material. This was mitigated with chemistry, but similar problems may show up in long-lived power reactors.
Tritium production If lithium is used in the salt, tritium will be produced, which is radioactive and extremely mobile (since it is small, it can go through metal like a hot knife through butter). ORNL used a special sodium fluoroborate intermediate salt to capture most of it, but a large amount still escaped to the environment.
Remote maintenance The chemical plants will need periodic maintenance, but all of the equipment will be highly radioactive. Expensive remote maintenance will be required. If graphite moderator is used, its replacement will also be remote and expensive.
Complex chemical plant -- Some of the fission product removal is simple, such as the gas sparging to remove Xe and Kr, and noble metal plateout. But to do the more serious fission product (or actinide) separation, complex processes are required, such as the liquid Bismuth reductive process, volatilization , or electoplating. These have been studied in detail, but are complex enough to be a disadvantage. Don’t make us post a process flow diagram.
While Wilson’s reactor is a molten salt reactor (I believe it’s an LFTR), he describes it as something that is sealed, relatively low power (~1MW, IIRC) and low maintenance. Is this just typical TED talk pie in the sky or has he come up with something new?
Thanks,
Moved at the request of the OP.
Bumping in hope of getting answers to unanswered questions.
http://sciradioactive.com/Taylors_Nuke_Site/My_Lab.html
and
Taylor Wilson (born May 7, 1994) is an American nuclear physicist and science advocate. Wilson achieved controlled nuclear fusion in 2008 when he was 14 years old. He has designed a compact radiation detector to enhance airport security. Wilson works to expand applications for nuclear medicine, and to design and develop modular power reactor technology.
Taylor Wilson was born in 1994 in Texarkana, Arkansas to Kenneth and Tiffany Wilson. His father is the owner of a Coca-Cola bottling plant, an...
No mention of his current life expectancy though…