New Salt Cooled Nuclear Reactor Approved by NRC

[gleem]

TL;DR Summary

For the first time in 50 years, a non-water-cooled nuclear reactor has receive approval by the NRC It will be a nonpower pilot plant to be built in Oak Ridge Tennessee.

A California company Kairos has received a permit to build a non power producing salt cooled nuclear reactor at Oak Ridge Tennessee.The reactor is considered safer since it uses a low-pressure mixture of molten fluoride salts of Lithium and Beryllium called FliBe. Molten salt reactors are not new. Such a reactor was built and operational in the 1960s. The fuel is also considered safer. The fuel is in the form of encapsulated spheres of uranium called TRISO-X about the size of a tennis ball which the manufacturer says cannot melt.

https://www.chemistryworld.com/news...a-step-towards-safer-reactors/4018890.article

 

[Flyboy]

Good! Glad to see they’re actually greenlighting new designs for hardware testing. PWRs are great and all, but from my understanding, we’ve kinda hit the practical upper limit for development of them. Fresh approaches might be exactly what we need to get a new wave of commercial plants in the pipeline.

 

[gmax137]

but from my understanding, we’ve kinda hit the practical upper limit for development of them

I'm not sure what this means?

There is plenty of action in detailed fuel and cladding design, see eg "accident tolerant fuel."

The "passive" safety systems in the Westinghouse AP1000 were first developed in the 1985-1995 time frame, but are only recently deployed (four units in China and two in the US). Experience with those (I hope only in functional and surveillance testing) may lead to further development.

The South Korean descendants of the CE System 80 PWR are coming on line in the UAE, it will be interesting to see how they perform. (see https://en.wikipedia.org/wiki/Barakah_nuclear_power_plant)

 

[hutchphd]

This seems a much more reasonable design than the pressurized boiling water reactor. It is my hope that this development will also dovetail with possibilities for Thorium based reactors. I note that the submission to the NRC proposes enrichment to ~19% for the uranium fuel which is a little worrisomes. But atmospheric pressure!! I think this may mark where we turn the corner.........

 

[Flyboy]

I'm not sure what this means?

There is plenty of action in detailed fuel and cladding design, see eg "accident tolerant fuel."

The "passive" safety systems in the Westinghouse AP1000 were first developed in the 1985-1995 time frame, but are only recently deployed (four units in China and two in the US). Experience with those (I hope only in functional and surveillance testing) may lead to further development.

The South Korean descendants of the CE System 80 PWR are coming on line in the UAE, it will be interesting to see how they perform. (see https://en.wikipedia.org/wiki/Barakah_nuclear_power_plant)

There is a practical upper limit to how thermally efficient a PWR can be, mainly because of the upper limits of the primary coolant loop being, well, pressurized water. The switch to a different primary loop coolant is, imo, long overdue. You can run the coolant loop at a higher temperature, which if my understanding is correct, produces better efficiency. It certainly will reduce the risk of boiling off the coolant if you get a leak, so there’s much higher safety margin there.

On the flip side, you now have irradiated salts that you have to figure out what to do with, as well as needing to figure out what kinds of problems can crop up. You won’t have, what, 70ish years of service experience with a salt coolant loop like you do with PWRs.

 

[Algr]

I think it makes more sense to spend the money on storage for renewables, on long distance transmission lines, and on geothermal.

Nuclear reactors are so expensive and slow to come on line. This one won't even generate power. By the time we have thorium salt reactors actually generating electricity, renewables might make them obsolete. (Or the world will be flooded and in economic/political collapse.) Those new reactors might be good for edge cases like submarines, Antarctica, and maybe cargo ships. But not much else.

I once talked to a pro-nuclear guy who was obsessed with the factoid that windmill blades could not be recycled yet, but dismissed the dangers of nuclear waste. That was weird.

 

[Vanadium 50]

we’ve kinda hit the practical upper limit for development of them.

Maybe we have, but the adoption is limited not by a lack of development, but by large segments of the populace convinced that nuclear power is intrinsically evil. Worse than climate change. Worse than the deaths from the fossil extraction and refinement industries. Worse than supporting illiberal, murderous and/or just plain evil regimes.

These people don't want a better design. They don't want it at all.

 

[Algr]

I dunno, Vanadium, that kind of sounds like a strawman argument. You aren’t going to convince anyone of anything if you can’t articulate what their actual position is.

 

[Orodruin]

The actual position is deep fear. Fear of anything associated to the word ”nuclear”. Fear based on association to nuclear weapons, nuclear accidents like Chernobyl, etc. It is not a rational fear, which is why it cannot be argued against. It is ingrained in large parts of the population. The same fear that MRI is called MRI and not NMRI.

 

[Algr]

Why is that fear not rational? Chernobyl happened. Radiation leaks happen, and are hushed up. Humans will always be human, and those who don't take risks seriously are usually those who fail in the end.

And note that my argument in my first post above has nothing to do with safety. Nuclear is just too slow and expensive.

 

[Orodruin]

Why is that fear not rational? Chernobyl happened.

Look at continued fossil fuel usage for comparison. This is associated with a not insignificant amount of health issues and deaths - even taking away the climate argument. In comparison, nuclear power is significantly safer and less impactful. The difference is that the catastophical events of nuclear power seem much more dramatic than the slow and agonizing development of COPD.

And note that my argument in my first post above has nothing to do with safety. Nuclear is just too slow and expensive.

Irrelevant as it is not what I was replying to.

 

[Algr]

Look at continued fossil fuel usage for comparison.

Why? If we are talking about future development, no one thinks it is fossil fuels. The real comparison is with renewables, and they are cheaper and safer. Renewables are seeing rapid improvement, with clear paths to solve their problems. Nuclear by comparison is struggling to implement solutions that were known in the 1960s.

Fear of nuclear boils down to trust in powerful people to do the right thing when the public is distracted. That has been a problem since ancient times, and is not going to be solved by a new reactor design.

 

[Orodruin]

Why? If we are talking about future development, no one thinks it is fossil fuels. The real comparison is with renewables, and they are cheaper and safer. Renewables are seeing rapid improvement, with clear paths to solve their problems. Nuclear by comparison is struggling to implement solutions that were known in the 1960s.

Fear of nuclear boils down to trust in powerful people to do the right thing when the public is distracted. That has been a problem since ancient times, and is not going to be solved by a new reactor design.

You are completely missing the point of the comparison.

 

[Vanadium 50]

While it is a logical possibility, I doubt there are many people out there whose position is "I am opposed to nuclear power because the risk (deaths per year, or whatever other metric you like) is x. However, I would support it if it were x/2. (Or some other number)"

 

[Algr]

The risk of nuclear isn't predictable like fossil fuels, but highly dependant on the quality of regulation enforcement and honesty from industry leaders. With nuclear you have the one-idiot problem: Chernobyl, Three Mile Island, and Fukushima weren't caused by unknown physics, but because some idiot did something that others knew was wrong. We aren't going to suddenly, permanently loose a city due to fossil fuels, and certainly not due to renewables.

How many people died from Chernobyl? We'll never know, because a thousand years from now, Chernobyl will still be able to kill people. The one-idiot-rule strikes again:
https://www.cnn.com/europe/live-new...s-04-07-22/h_c7e5d7b38b80464002f7f4f98f823fb7

Statistically, fossil fuels may be worse, but we are making progress in reducing their use. Nuclear isn't really going to help us do that the way renewables are. While nuclear is less risky, building more is still adding risk. And because we don't know how to neutralize radioactive waste, it is risk that will be around for millenia.

 

[gmax137]

There is a practical upper limit to how thermally efficient a PWR can be, mainly because of the upper limits of the primary coolant loop being, well, pressurized water. The switch to a different primary loop coolant is, imo, long overdue. You can run the coolant loop at a higher temperature, which if my understanding is correct, produces better efficiency.

The fuel cost for a nuclear power plant is very low, something like 10% of the cost. So increasing thermal efficiency is a very low gain approach.

It certainly will reduce the risk of boiling off the coolant if you get a leak, so there’s much higher safety margin there.

This is a valid point - an atmospheric pressure system is much more forgiving.

For some context, the typical power generating PWR runs at ~600F and 2250 psia. The plant design must accommodate leaks or breaks in the primary piping. The regulatory approach is, assume the largest pipe breaks, with the two ends offset to allow unrestricted flow from both sides of the break (a "double-ended guillotine" break). Depending on the particulars, the largest primary pipes are in the 30 to 42 inch diameter range. Under these conditions, we find that the entire 500,000 pound water inventory will blowdown in about ten seconds. That's why the containment structures are so large and robust (and expensive to build).

An atmospheric pressure system doesn't have to worry about anything like this. It would have different "maximum hypothetical accidents" but the hope is they will be milder and easier to accommodate.

As to the risk from fossil fuel power generation, we know very well what it is, without even thinking about climate change:

https://seas.harvard.edu/news/2021/02/deaths-fossil-fuel-emissions-higher-previously-thought

More than 8 million people died in 2018 from fossil fuel pollution, significantly higher than previous research suggested, according to new research from Harvard University, in collaboration with the University of Birmingham, the University of Leicester and University College London. Researchers estimated that exposure to particulate matter from fossil fuel emissions accounted for 18 percent of total global deaths in 2018 — a little less than 1 out of 5.

And I know nobody in this thread is arguing in favor of continued use of fossil fuels, but I also don't see it going away anytime soon. There's just too much reliance on it now.

 

[Orodruin]

We aren't going to suddenly, permanently loose a city due to fossil fuels, and certainly not due to renewables.

Again, this part of the debate is not nuclear vs renewables. It is about the irrationality about nuclear per se because of the stirred emotions. Yes, Chernobyl happened, but a lot has happened since then. It was 38 years ago.

The real spectre associated with nuclear is not only the possibility of an accident, but also the horrors associated with nuclear weapons. It is an exceptionally loaded word.

The fear of nuclear power accidents are forever burned into people’s minds, much like the fear of shark attacks. They do happen, but cows kill far more people than sharks do. Yet most people can more vividly imagine the horrors of a predator from the deep blue biting them in half than a cow kicking them in the chest.

I am not particularly pro-nuclear over renewables, but this thread is about nuclear technology, not about renewables.

 

[Flyboy]

And I know nobody in this thread is arguing in favor of continued use of fossil fuels, but I also don't see it going away anytime soon. There's just too much reliance on it now.

Absolutely, especially when you are dealing with mobile or transient power requirements. It takes, what, a few minutes to spin up a natural gas fueled gas turbine plant? Perfect for dealing with unexpected power shortages. And when you’re on the go, electric power is acceptable for short range stuff, like kicking around town in a car, or hopping from a bedroom community to a big city on a plane. But the energy density of a gallon of hydrocarbon fuel like Jet-A or automotive gasoline, combined with the ease of handling and storage, is extremely difficult to compete with for remote/long distance travel. You’re not flying from New York to Miami in a single go with electric airplanes, let alone a trip across an ocean.

 

[Vanadium 50]

but cows kill far more people than sharks do.

Revenge.

 

[Vanadium 50]

We aren't going to suddenly, permanently loose a city due to fossil fuels, and certainly not due to renewables.

I was going to put in a laughing emoji, but you're not being ironic, are you? You're serious.

Renewables are not all sweetness and light. The Banqiao dam failure alone killed over a hundred thousand people (some say almost a quarter million; the exact number is still a Chinese state secret) and left 11 million people homeless - more than the entire population of Ohio. It wiped out everything in an area the size of Connecticut.

And that's just one hydroelectric dam failure. Just one.

 

[Algr]

Did I mention "dames"?

but also the horrors associated with nuclear weapons. It is an exceptionally loaded word.

This is a weirdly "4chan" thread for Physics forums with so many people putting words in their opponents' mouths. I'm kind of sorry I brought them up in that other thread. Lets just discuss the points that people here are actually making.

I find the physics and technology of these thorium salt reactors fascinating. I was enthusiastic about them until I started thinking about the timescales involved and what batteries and storage technologies would be like 20 years from now.

I know you don't mean it this way, but calling the public irrational could be misunderstood as "We are too concerned with safety, and should have less oversight." Nuclear advocates who decry the public like that are not doing their cause any favors.

 

[gmax137]

"We are too concerned with safety, and should have less oversight."

I hope you don't think that that is my view.

If I were king, the fossil plants would not be allowed to use our atmosphere as their waste management plan. Equal oversight, regardless of the technology.

 

[Algr]

I hope you don't think that that is my view.

Don't worry, I understood. But you were advocating in a way that could backfire, and offend people you need to persuade. Even if we don't agree, I think we both want conclusions based on understanding of the real issues.

 

[Astronuc]

There is a practical upper limit to how thermally efficient a PWR can be, mainly because of the upper limits of the primary coolant loop being, well, pressurized water. The switch to a different primary loop coolant is, imo, long overdue. You can run the coolant loop at a higher temperature, which if my understanding is correct, produces better efficiency. It certainly will reduce the risk of boiling off the coolant if you get a leak, so there’s much higher safety margin there.

Some of the German pre-Konvoi plants realized nearly 37.6% thermal efficiency, which was actually realized on the secondary side with improved turbine blade designs and improved sealing at the blade tips to reduce by-pass flow.

The has been consideration of supercritical LWRs, at higher temperature and pressure. Three major challenges are the internal pressure of the fuel elements (about 30% of fission products are Xe,Kr isotopes, and smaller fraction (Se, Br, Sr; Te, I, Cs) are volatile or gaseous depending on fuel temperature), the corrosion of the structural materials (fuel cladding, core support structure, and primary loop (reactor pressure vessel, piping and coolant pumps, and heat exchangers).

Increasing the primary system temperature, even if one deploys a low-vapor-pressure salt, shifts the challenges to the heat exchange and secondary side; what thermodynamic cycle will be used to spin the turbines - Brayton (gas), Rankine (water to steam to water), or ? Now the secondary side has to withstand the higher temperature corrosion environment. How often will major components (heat exchange, piping, reheaters, turbines) have to be replaced? Also, what happens if the heat exchanger tubing/plate is breached, and the secondary coolant enters the primary system.

And there are other challenges - depending on the fuel design. How to level out the burnup in the fuel? What will be the disposition of used fuel? How to handle breached (failed) fuel?

Another interesting problem is the photo-disintegration of Be from gammas above the threshold for the reaction. There are some other photonuclear reactions of concern.

On the flip side, you now have irradiated salts that you have to figure out what to do with, as well as needing to figure out what kinds of problems can crop up. You won’t have, what, 70ish years of service experience with a salt coolant loop like you do with PWRs.

There is that challenge as well. When we built the first LWRs, we did so with essentially no experience. There we small cores/reactors like Saxton, Zorita, and Shippingport. The folks went with what they knew in terms of structural alloys used in conventional power plants, e.g., type 300 stainless steels, and in some cases, Ni-based alloys, e.g., Inconels and Incoloys, some of which came from the X-aircraft programs.

It took a couple of decades to adjust the compositions and tweak the manufacturing processes to get improved performance. Zircaloys were developed in the 1950s, and because standard in the 1970s, but still it took a couple of decades to make improvements in performance, and in some cases, newer alloys were developed in the early 2000 into the 2010s. Accident tolerant fuel development is still ongoing. Since it takes 5 to 6 years to get to the design life in a reactor, with a lead time for development of 5 to 10 years, and a couple of year after irradiation to get PIE results, and perform additional testing (e.g., simulated LOCA and transient testing) not permissible in commercial power reactors, it can take up to 15 years to vet a new design. In parallel, one has to develop a suite of codes that simulate the performance of the fuel, reactor and power plant under normal, off-normal, design basis (hypothetical) accident (DBA) and now beyond-design-basis accident (BDBA) conditions.

 

[Algr]

Am I correct in understanding that these new thorium designs don't use water for anything? No cooling ponds? Or is there still (non-radioactive?) water going through the turbine?

 

[gmax137]

Am I correct in understanding that these new thorium designs don't use water for anything? No cooling ponds? Or is there still (non-radioactive?) water going through the turbine?

I think you have to check each design. Some have a regular water/steam secondary, others a gas Brayton cycle. There may be a water based decay heat removal system as well.

 

[Astronuc]

Am I correct in understanding that these new thorium designs don't use water for anything? No cooling ponds? Or is there still (non-radioactive?) water going through the turbine?

As far as I know, current designs use HALEU fuel - uranium enriched to less than 20%, i.e.,. 19.5 - 19.75% to allow for some uncertainty. The fuel is often (UCO) encapsulated in layers of PyC/SiC/PyC, which may be distributed in a prismatic block or spherical ball. FLIBE (LiF-BeF₂) would pass through the fuel matriix (through cooling channels in a block, or between a bed of spherical balls) - assuming that the fuel is separate from the coolant. Fission products ostensibly remain in the encapsulated fuel (e.g., TRISO particle). TRISO fuel was orginally proposed for a VHTR (very high temperature reactor), which used gas cooling, and was graphite moderated. Pebble bed was an oft use phrase. HTGR is acronym; AVR is another.
https://www.gen-4.org/gif/jcms/c_42153/very-high-temperature-reactor-vhtr
https://en.wikipedia.org/wiki/High-temperature_gas-cooled_reactor
https://en.wikipedia.org/wiki/AVR_reactor

There were some concepts in which the U (Pu,Th) fluoride or chloride salt is in salt solution (FLIBE) or (FLiNaK), or whatever salts mixtures one chooses. That is a greater level of complexity since one must have an onlice process to 'clean' the salts of fission products as was previously mentioned.


One still needs to have a working fluid to push through the turbine if one wishes to generate electricity. The working fluid depends on the thermodynamic cycle (e.g., water/steam Rankine cycle, or CO₂/Ar/Ne for a Brayton cycle). One could try a Stirling (piston) cycle, but those can be problematic, especially with large masses).

 

[berkeman]

A California company Kairos has received a permit to build a non power producing salt cooled nuclear reactor at Oak Ridge Tennessee.

Sorry if this has been covered already, but what do they do with the power generated by this reactor? What does it mean to be a non-power-producing reactor? Do they just drive some dummy loads of some kind?

 

[Astronuc]

Sorry if this has been covered already, but what do they do with the power generated by this reactor? What does it mean to be a non-power-producing reactor? Do they just drive some dummy loads of some kind?

It would appear to be a demonstration reactor - they can get to criticality, raise to a power, generate thermal energy. So, it's probably proof of concept - and low power. It would be a 'research reactor', which is treated differently by the NRC as compared to a power reactor.

The original MSR generated some thermal energy, which was dissipated to the atmosphere through heat exchangers.

 

[Algr]

The original MSR generated some thermal energy, which was dissipated to the atmosphere through heat exchangers.

 

[DrDu]

Nice, so you not only have to mess around with radioisotopes but also with ultra toxic beryllium compounds. Really sounds like an advance in technology!