AHC/WI: More Support for Molten Salt Reactors in the United States

Delta Force

Banned
Historically, molten salt reactor technology had little support from politicians, the scientific community, and industry in the United States. Alvin Weinberg and other scientists at Oak Ridge National Laboratory were the only major proponents of the technology, although they managed to secure prominent contracts for nuclear powered aircraft and rockets from the USAF (Aircraft Nuclear Propulsion) and NASA (Nuclear Engine for Rocket Vehicle Application. The Molten Salt Reactor Experiment was also built and operated successfully for a few years with no major incidents, remarkable for a prototype reactor and in contrast to the significant problems experienced by prototype sodium cooled reactors, which enjoyed much greater support. The S2G sodium cooled reactor on the USS Seawolf was so problematic that Admiral Rickover went out of his way to ensure that only conservatively design light water reactors would power nuclear Navy ships.

What if molten salt reactor technology had received support from top politicians instead of sodium cooled reactors? Could molten salt reactors have met the strict safety requirements of Admiral Rickover? Could they have become a mainstream design for second and later generation nuclear reactors?
 
Paging Asnys- he's forgotten more about AEC politics and nuclear development than I could learn in three years going flat-out.

Essentially you answered your own question, Rickover convinced Congress and successive presidents that LWR's were the only "safe" reactor design if you ignore the Thresher incident in 1963 (attack sub lost with all hands, leaking water both forced a SCRAM of the reactor and caused the emegrency ballast dump system to fail).

Give AEC more political savvy, more powerful patrons, and a more serious push for US energy independence in the 1980's, seriously trying LFTR's, breeders, and other alternative fission technologies...and nuclear power is a much more viable, profitable proposition.
 

Delta Force

Banned
I wonder if some of it might have been due to the molten salt reactor being one of the few nuclear reactor concepts not originally studied by the Chicago Metallurgical Laboratory during World War II. From what I've been able to determine, the concept was developed sometime in the mid-1950s for either a ballistic missile or the Aircraft Nuclear Propulsion Program. Perhaps the concept could have emerged earlier?
 
Paging Asnys- he's forgotten more about AEC politics and nuclear development than I could learn in three years going flat-out.

You flatter me. :eek:

This actually brings up my personal favorite potential PoD of all time: in the late '50s, Alvin Weinberg was offered a seat on the Atomic Energy Commission - that is, the five guys who are the actual Commission. Not the chairmanship, but who knows what that could lead to in years to come? IOTL, he turned it down because he wanted to remain as director of ORNL.

It's not a perfect PoD - a perfect PoD would prevent the Great Bandwagon Market in LWR's, which this probably won't - but it's the best I've got.
 

Delta Force

Banned
You flatter me. :eek:

This actually brings up my personal favorite potential PoD of all time: in the late '50s, Alvin Weinberg was offered a seat on the Atomic Energy Commission - that is, the five guys who are the actual Commission. Not the chairmanship, but who knows what that could lead to in years to come? IOTL, he turned it down because he wanted to remain as director of ORNL.

It's not a perfect PoD - a perfect PoD would prevent the Great Bandwagon Market in LWR's, which this probably won't - but it's the best I've got.

I've been doing some research for a paper and also for my timeline, and many authors point to Rickover having an undue influence on the course of nuclear power development. One even claims that Rickover had decided in favor of light water reactors as early as 1946. Even if he was only leaning that way or truly neutral, the problems with the S1G and S2G reactors and Seawolf definitely didn't endear the Navy to alternative reactor technologies.

When the United States decided to start developing commercial nuclear reactors in the 1950s, the Navy aircraft carrier reactors were used as a starting point. In 1958 the European market apart from France and the United Kingdom opened up to American PWR technology through the EURATOM Cooperation Act. That preceded the Bandwagon Market in the United States, but certainly contributed to it, as many experts thought European gas cooled reactors were superior to American PWR designs. By the 1970s Canadian heavy water technology was the only alternative to American PWR designs, apart from those developed by the Soviets. General Atomics sold a few high temperature reactors prior to the 1973 Energy Crisis (I think they were gas cooled), but ironically they were canceled afterwards due to a decline in energy demand, despite concern over the use of fossil fuels.

One paper argues that a lock in was inevitable, and that PWR won out because of its early advantages, but it also argues that in the early development of a technology the decision to pursue technologies can be essentially random. A small advantage or advancement along the curve of a technology can lead to something that works better early in development beating out a technology that is superior at a later stage of development.

I think there might still have been a chance for an alternative design to have become popular for the second generation nuclear reactors onwards, but the United States made mistakes in the development of technologies and in forecasting resource demands. Specifically, sodium cooling was developed for too long after major questions were raised about cost and reliability, and breeder reactors turned out not to be required.

Having read into it more, I'm wondering if gas cooled designs might have been able to take the place of PWR in the early history of nuclear power (Chicago Pile 1 was itself graphite moderated, although not with a gas). It was essentially a toss-up between the two technologies in the 1950s, but gas cooled designs can potentially achieve thermal efficiencies of 40% to 50%. They can even use pressure chambers built out of concrete with stringers, allowing them to be built with less specialized industry while having a reduced probability of sudden catastrophic failure.

Heavy water reactors would have been another interesting route, although they don't have potential power densities as high as gas cooled designs. They were less expensive then PWR designs in the 1970s, although I think they had to undergo expensive repairs in the 1980s. I'm not that familiar with gas cooled reactors, but I know the heavy water designs produce significant quantities of plutonium, as well as tritium, critical for the construction of thermonuclear weapons. Perhaps the British could have taken advantage of the heavy water facilities in Canada and Europe for a heavy water reactor program?

That gets to molten salt reactors. They were projected to be cost competitive with PWR designs in the 1970s, after several test reactors had been built and operated without incident. One fluid designs were successfully operated, and a two fluid design would have been usable as a breeder reactor, if developed. MSR designs can do online refueling and chemical processing of their fuel to allow for long term operation, and there was even a design for a one-through MSR capable of operating for thirty years without refueling. The technology seems to have had promise for both conventional and breeder operation (it was also multi-fuel capable), and could have been part of the second generation of commercial reactors had it been pursued or even alongside of the breeder reactor design favored by the Atomic Energy Commission.

Essentially, I'm wondering if gas cooled reactors (perhaps with heavy water reactors as a niche, similar to today) and MSR reactors could have become an industry standard instead of the PWR, and what effect that might have had on nuclear power. Also, would a gas cooled design (or even a heavy water design) be useful for a nuclear powered warship?
 
Last edited:
Any suggestions on the feasibility of some of these alternate nuclear power developments?

Well, I should say that a gas-cooled reactor ought to be practical for naval use; it would essentially be a gas turbine with a nuclear heat source instead of a combustion heat source, and of course gas turbines have been widely used in naval vessels since then. Gas-cooled reactors (termed "Brayton-cycle" designs in the documents, so literally nuclear gas turbines) were favored by NASA as nuclear power sources for advanced space stations and interplanetary spacecraft in the late 1960s and early 1970s, which strongly suggests that they could have been made small and light enough for naval use, as well (though possibly at a high cost).

One problem might be the very fact that it is basically a gas turbine with a nuclear heat source instead of a combustion heat source. At the critical time, in the 1940s and 1950s, gas turbines weren't nearly as mature and developed as they are today, which may have played a role in why gas-cooled reactors were disfavored in the United States. I've long thought that one of the key advantages of PWR and BWR designs, in terms of getting accepted, was the fact that outside of the nuclear components they were very similar to the technology used in existing power plants. They still relied on superpressure water and steam for heat transfer; they still used steam turbines; it was just that they didn't use coal or oil or gas for heat, but a nuclear source. The Navy had relied on steam turbines for decades by then, and power companies for about as long. It was...the easy choice.
 

Delta Force

Banned
Well, I should say that a gas-cooled reactor ought to be practical for naval use; it would essentially be a gas turbine with a nuclear heat source instead of a combustion heat source, and of course gas turbines have been widely used in naval vessels since then. Gas-cooled reactors (termed "Brayton-cycle" designs in the documents, so literally nuclear gas turbines) were favored by NASA as nuclear power sources for advanced space stations and interplanetary spacecraft in the late 1960s and early 1970s, which strongly suggests that they could have been made small and light enough for naval use, as well (though possibly at a high cost).

Doing a quick search, I did find some allusions to gas cooled nuclear reactor proposals for warships. I also found an academic paper on the use of molten salt reactors, but I don't think it was government sponsored and it was unclear on if it was focused on military or commercial use.

Also, since the Brayton cycle is mostly brought up with regards to gas turbines, including jet engines, could it have been a contender for the Aircraft Nuclear Propulsion Program as a directly air cooled design? That would pose some obvious safety risks due to the coolant and open cycle, but would create a small and compact reactor.

I'm also wondering if it could share some components with a system using petroleum or natural gas, avoiding the duplication of some systems, especially turbines. For example, an aircraft could use conventional fuel for takeoff and landing, or to further increase power with the afterburner, avoiding problems with overheating reactor components. A ship could do something similar, using the reactor for cruising, conventional fuels when entering or exiting ports where nuclear power isn't as welcome, and using both for high speed. Lastly, perhaps a utility could use a similar system to allow a reactor to operate at peak efficiency, using conventional fuel to respond to changes in power demand instead of adjusting the reactor.

One problem might be the very fact that it is basically a gas turbine with a nuclear heat source instead of a combustion heat source. At the critical time, in the 1940s and 1950s, gas turbines weren't nearly as mature and developed as they are today, which may have played a role in why gas-cooled reactors were disfavored in the United States. I've long thought that one of the key advantages of PWR and BWR designs, in terms of getting accepted, was the fact that outside of the nuclear components they were very similar to the technology used in existing power plants. They still relied on superpressure water and steam for heat transfer; they still used steam turbines; it was just that they didn't use coal or oil or gas for heat, but a nuclear source. The Navy had relied on steam turbines for decades by then, and power companies for about as long. It was...the easy choice.

It is interesting to note that Babcock & Wilcox, a major boiler producer for the Navy and utilities, went on to play a major role in the development of nuclear reactors for both roles.
 

Delta Force

Banned
Alvin Weinberg was offered a seat on the Atomic Energy Commission in the late 1950s. If Weinberg had accepted, could he have ensured continued development of the molten salt reactor? Could the MSR have been developed alongside the sodium cooled fast breeder reactor as an advanced power reactor, or perhaps have become the breeder reactor option, later expanding into power reactors with simplified designs?
 
Paging Asnys- he's forgotten more about AEC politics and nuclear development than I could learn in three years going flat-out.

Essentially you answered your own question, Rickover convinced Congress and successive presidents that LWR's were the only "safe" reactor design if you ignore the Thresher incident in 1963 (attack sub lost with all hands, leaking water both forced a SCRAM of the reactor and caused the emegrency ballast dump system to fail).

Give AEC more political savvy, more powerful patrons, and a more serious push for US energy independence in the 1980's, seriously trying LFTR's, breeders, and other alternative fission technologies...and nuclear power is a much more viable, profitable proposition.

There is no such thing as a "emergency ballast dump system." Flooding caused an electrical short. The reactor scrammed. Back then the policy was to shut the main engine throttles to conserve heat/energy in the primary. By shutting the main engine throttles, they could not drive to the surface. In Control, the Emergency Main Ballast Tank Blow system was activated. This allows high pressure air to enter the fore and aft main ballast tanks and force the water out of the open grating at the bottom. That class of sub did not have dehumidifiers on the high pressure air compressors. This allowed moisture to enter the high pressure air storage tanks. When the air was released into the ballast tanks, this moisture froze in the air lines stopping the "Emergency Blow." The sub came up to around 50-100 feet and then started sinking again. If you have ever served on a sub and heard the recording of this you would find it one of the most chilling things that you would ever hear.

The design of the reactor on the USS Thresher had nothing to do with the accident.
 

Archibald

Banned
to Asnys and Delta Force

This actually brings up my personal favorite potential PoD of all time: in the late '50s, Alvin Weinberg was offered a seat on the Atomic Energy Commission - that is, the five guys who are the actual Commission. Not the chairmanship, but who knows what that could lead to in years to come? IOTL, he turned it down because he wanted to remain as director of ORNL.

It's not a perfect PoD - a perfect PoD would prevent the Great Bandwagon Market in LWR's, which this probably won't - but it's the best I've got.

The POD in my space TL (Explorers, see my signature) is set in 1971, too late for that. Yet Weinberg was still director of ORNL. I plan a different fate for him and the MSRE, courtesy of the space program.
 
One of the reasons the US went with light water reactors is that they are a kind of twofer. You can use the same reactor to build nuclear weapons to generate power. Molten salt reactors can't be used that way, Since the US developed nuclear weapons first it was the easy way for nuclear power. It was already built before and had all the bugs worked out.

A potential solution is that the government worries about nuclear proliferation earlier. As molten salt reactors can't be used to build nuclear weapons you would have less people out there with a working knowledge of the nuclear technology that can be used to build nukes. If you get the government worried about that in the late forties and early fifties it might require molten salt for civilian reactors.
 
One of the reasons the US went with light water reactors is that they are a kind of twofer. You can use the same reactor to build nuclear weapons to generate power. Molten salt reactors can't be used that way, Since the US developed nuclear weapons first it was the easy way for nuclear power. It was already built before and had all the bugs worked out.

I'm sorry, but this is just flat-out not true. The US never used light water reactors to produce plutonium; we used a mixture of graphite-moderated, water-cooled reactors (at Hanford) and heavy water reactors (at Savannah River). Light water reactors were initially developed to power submarines, and they were used for civil nuclear power because a) a lot of development work had already been done, and b) they were relatively simple compared to more exotic concepts like the MSR.

And Molten Salt Reactors can be used to make plutonium. You can run an MSR on the same uranium fuel cycle a light water reactor uses. What Kirk Sorenson and his group want to do is to develop an MSR using the thorium/U-233 fuel cycle. While thorium/U-233 is proliferation-resistant, it's not proliferation-proof, and it's not at all clear how big a barrier U-232 contamination really is to building nuclear weapons. You would probably need to modify the fuel cycle for a thorium MSR to produce relatively U-232-free U-233 for weapons, which could be detected - but you have a similar problem if you want to use a uranium reactor to make weapons plutonium, due to contamination with Pu-240, which causes pre-initiation in weapons.

So the anti-proliferation argument for these machines is not at all clear-cut... And it derives from the thorium fuel cycle, not the MSR. And the thorium fuel cycle can be used in other types of reactors, including light water reactors - the famous Shippingport PWR was turned into a thorium breeder, in fact. The MSR has a much higher breeding ratio then an LWR, so it works with thorium much better, but it's also a lot harder to develop into a working reactor.

In short: the real advantages of the MSR are improved safety, and maybe lower cost. The anti-proliferation argument is very arguable.
 
I'm sorry, but this is just flat-out not true. The US never used light water reactors to produce plutonium; we used a mixture of graphite-moderated, water-cooled reactors (at Hanford) and heavy water reactors (at Savannah River). Light water reactors were initially developed to power submarines, and they were used for civil nuclear power because a) a lot of development work had already been done, and b) they were relatively simple compared to more exotic concepts like the MSR.

And Molten Salt Reactors can be used to make plutonium. You can run an MSR on the same uranium fuel cycle a light water reactor uses. What Kirk Sorenson and his group want to do is to develop an MSR using the thorium/U-233 fuel cycle. While thorium/U-233 is proliferation-resistant, it's not proliferation-proof, and it's not at all clear how big a barrier U-232 contamination really is to building nuclear weapons. You would probably need to modify the fuel cycle for a thorium MSR to produce relatively U-232-free U-233 for weapons, which could be detected - but you have a similar problem if you want to use a uranium reactor to make weapons plutonium, due to contamination with Pu-240, which causes pre-initiation in weapons.

So the anti-proliferation argument for these machines is not at all clear-cut... And it derives from the thorium fuel cycle, not the MSR. And the thorium fuel cycle can be used in other types of reactors, including light water reactors - the famous Shippingport PWR was turned into a thorium breeder, in fact. The MSR has a much higher breeding ratio then an LWR, so it works with thorium much better, but it's also a lot harder to develop into a working reactor.

In short: the real advantages of the MSR are improved safety, and maybe lower cost. The anti-proliferation argument is very arguable.


You are right I mixed up the technologies of nuclear weapon production and nuclear sub power. :eek: I don't know how did that.

IIRC it is simply easier to modify the fuel mix to prevent contamination by Pu -240 than U-232 but I could have read it wrong. Of course you can turn Thorium 232 to U233 using any kind of reactor as all it needs is a neutron source but unless I mistaken it is easier in a MSR due to its fuel being in a liquid state rather than a solid state and liquids are easier to work with. This should make the separation easier and quicker if I am not mistaken.
 
You are right I mixed up the technologies of nuclear weapon production and nuclear sub power. :eek: I don't know how did that.

No worries.

IIRC it is simply easier to modify the fuel mix to prevent contamination by Pu -240 than U-232 but I could have read it wrong. Of course you can turn Thorium 232 to U233 using any kind of reactor as all it needs is a neutron source but unless I mistaken it is easier in a MSR due to its fuel being in a liquid state rather than a solid state and liquids are easier to work with. This should make the separation easier and quicker if I am not mistaken.

It makes the separation easier once you've developed the technology - a lot easier - but it makes developing the technology in the first place a lot harder. The physics of liquid fuel reactors is still not as well understood as solid fuel reactors, the chemistry of FLiBe is not well understood - even today, this is still relatively exotic technology that will require a fair amount of development to turn into a working power reactor.

Don't get me wrong, I like MSRs. I don't like them as much as some people, because I'm rather suspicious of the cost estimates. But they're on my short list of where we might be getting our electricity in the year 2100. But these are not simple pieces of technology, and they will require a lot of time and money to develop.
 
No worries.



It makes the separation easier once you've developed the technology - a lot easier - but it makes developing the technology in the first place a lot harder. The physics of liquid fuel reactors is still not as well understood as solid fuel reactors, the chemistry of FLiBe is not well understood - even today, this is still relatively exotic technology that will require a fair amount of development to turn into a working power reactor.

Don't get me wrong, I like MSRs. I don't like them as much as some people, because I'm rather suspicious of the cost estimates. But they're on my short list of where we might be getting our electricity in the year 2100. But these are not simple pieces of technology, and they will require a lot of time and money to develop.


I doubt that long. They had a working reactor in the early to late 60s IIRC although it was an experimental one. It needs to be scaled up but I doubt it would take more than a few tens of billions and a decade or so if focused on.
 
Top