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Molten Salt Nuclear Reactors- so what’s there not to like?

image credit: Visual Source: Seaborg Technologies
Paul Hobcraft's picture
Innovation & Energy Knowledge Provider, Agility Innovation

I work as a transition advocate for innovation, ecosystems, within IIoT, and the energy system as my points of focus. I relate content to context to give greater knowledge and build the...

  • Member since 2020
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  • Jun 17, 2021

Let’s discuss Nuclear in different ways than the present discussion has gone. Nuclear has been not given the debate it deserves. That needs changing in my view.

This is largely from the use of salt! Well, actually, small modular reactors offer a Nuclear future as part of our clean energy requirements.

I wrote a piece recently, “the Elephant that should be in the Energy Debate,” and it is largely because of the technology, safety and reality of what Nuclear offers in new approaches and designs that make it have a real place to be at the Energy Transition table.

Firstly what is a molten salt reactor (MSR)?

It is a class of nuclear fission reactor where the primary coolant and/or the fuel is a molten salt mixture. There are several different designs, all looking to bring small modular reactors (SMR) to market.

MSR has significant advantages over traditional nuclear reactors.

First, the MSR typically operates at or close to atmospheric pressure, rather than 75 to 150 times atmospheric pressure used for LWR’s, thereby reducing the containment structures’ needs and eliminating hydrogen as a source of explosion risk.

Equally, the MSR does not produce dangerous and radioactive fission gases under pressure; these are naturally absorbed into the molten salt. This smaller reactor and these differences provide a key benefit of removing the risks of contaminating large land areas.

The MSR can also operate at higher operating temperatures providing higher electricity-generation efficiency, allowing for a greater coupling benefit of having grid-storage facilities, potentially more economical hydrogen product, and some potential for process-heat opportunities.

So why are these not the future for any debate on Nuclear?

Let’s continue with the good news. The combination of offering a low-pressure system and a high boiling point greatly limits the chance of a containment explosion. The MSR doesn’t require massive cooling in dedicated water ponds or rivers; they can be placed anywhere and air-cooled.

Visual Source: Seaborg Technologies

If the core were to overheat, the biggest and best safety feature is that a gravity-enabled passive shutdown system would send the heated, radiated salt into an underground containment chamber or drain tanks by simply gravity and turn off the reactor.

These MSR’s still face several challenges. Relevant design challenges include the corrosivity of hot salts and the changing chemical composition of the salt as it is transmuted by reactor radiation.

There are quite naturally different bodies of concern about Nuclear in general. Its need for the future is in new evolving modular solutions. There is a long list of advantages and disadvantages to working through, but I leave these out of this post.

There are different approaches to molten salt reactors, all being investigated or tested at present. I have used to illustrate MSR’s the visuals supplied by Seaborg Technologies to provide a clearer example of Molten Salt Reactors; they offer one concept of a few.

Also, Thorium-based energy is being significantly invested in still not well tested and does have some scenario’s still to be worked through in design, process and final operation.

Fusion power is in the future, a future rapidly coming into view without a doubt. It does have as much potential (or even more) to halting carbon emissions than other solutions more readily discussed? But as climate issues increase, we need to consider MSR and ones that seem to be ahead at present, the liquid fluoride thorium reactors (LFTRs)

I read up on Seaborg Technologies based in Denmark that their CMSR (compact molten salt reactor) is in design and further hypothesis validation. I have taken their excellent visuals to help describe and present Molten Salt reactors.

Without a doubt, Seaborg Technologies are motivated by the challenges of the need to address eliminating carbon dioxide and adding electricity through this solution.

Visual Source: Seaborg Technologies

The CMSR works with both fossil fuels and renewable energy sources. In either case, it generates a large amount of low-carbon energy. Another attractive feature is a novel liquid salt used as a neutron moderator: it acts as a catalyst to improve the efficiency of the fission chain reaction, reducing the size and cost of generating energy. Moreover, this moderator is not degraded by neutron irradiation – a challenge that has stalled previous attempts at commercializing the technology.

Liquid salt can be reprocessed, separating uranium and plutonium from fuel for reuse to produce waste that only needs 300 years of storage in nuclear cemeteries. So far, long-lived nuclear waste may need up to 300,000 years of storage.

The University of Idaho is looking for Nuclear Batteries.

Also, the US University of Idaho has announced they have verified a new process to speed up the development of the worlds first Molten Salt Nuclear Battery (MsNB). They claim this is a monumental step in the molten salt reactor design process. They envisage military bases, hospitals, and communities can gain reliable, secure, continuous energy from a MsNB as a small, distributed energy source, bringing autonomy to the users from reliance on more decentralised grids and energy supply.

The MsNB testing device uses ohmic heating to heat liquid via an electric current evenly. It acts as a reactor surrogate, mimicking the internal heat generation within a reactor through fission or splitting an atom’s nucleus. In the MsNB, the heat released during the ohmic heating testing process causes the molten salt fuel within the battery to rise in a central cylinder. Once at the top, the fuel moves to a heat exchanger, where it is cooled and falls back down the space between inner and outer cylinders. This natural circulation eliminates the need for valves and pumps, improving the reliability and simplicity of the reactor design.

Presently, the University of Idaho is looking for a grant to validate and compete for an MsNB design up to manufacturing by a partner, Premier Technology.

Natrium Reactors, Bill Gates and Warren Buffett

In my recent post, “The Elephant that should be in more in the Energy Debate- Nuclear.”

I picked up on a recent announcement that Warren Buffett and Bill Gates are coming together to build a nuclear Natrium reactor in Wyoming at a decommissioned coal plant. This is an advanced nuclear reactor that is suggested as safer, performs better and costs less than the traditional plants.

The project is based around a 345 MW sodium-cooled fast reactor with a molten salt-based energy storage system that will have storage technology to deliver a system’s output to 500 MW of power for more than five-and-a-half hours when needed, which is equivalent to the energy required to power around 400,000 homes and will be able to integrate with renewable resources and could lead to faster, more cost-effective decarbonization of electricity generation.

The Natrium™ technology is one of the fastest and lowest-cost paths to advanced clean energy that can change the world with their Generation IV non-light water reactors. Maybe.

What we see is that Small scale nuclear reactors are starting to be developed around the world.

We know Nuclear in its current power plant form is continuing to suffer heavy losses as renewables come online or are mostly scheduled to close. Globally, nuclear energy supplies 11% of electricity; it had come down from 17.6% back in 1996.

The cost of the building design, safety and maintenance of these traditionally designed Nuclear reactors are expensive and not flexible in their operation or management. If we move towards smaller modular, safer designs, Nuclear has the chance to become more competitive and attractive.

Are small modular reactors a new way forward for nuclear power?

There is a growing argument besides settling on a design for MSR’s they can be mass-manufactured at specialised facilities, transported more easily, and installed in remote locations where conventional power is not so feasible. They are compact and are a sound distributed energy solution. They cost significantly less than traditional large-scale reactors due to containment, leakage and environmental concerns. This becomes a way forward for many developing countries in the world.

Image and Concepts from Seaborg Technologies

Systems in design are integral, meaning the fuel, steam, and generator will be in one vessel, and the core’s own heat can drive the coolant flow, eliminating many pumps and moving parts that can fail. Each reactor will be self-contained.

Rolls-Royce in the UK are in a consortium for their Small Modular Reactor (SMR), but this is around a decade away from concept to scale.

If MSR’s can show cost and safety concerns are being addressed and can settle on limited standardised designs, mass manufacturing can give scale and cost reductions. Perhaps no different than solar& wind rapidly reduced costs, and now hydrogen is chasing that route, can MSR join them?

What is known is some of the big players of energy have attempted SMR solutions, including Westinghouse, giving up in 2014, then Babcock and Wilcox folded theirs in 2017. In Russia, state-funded MSR had construction costs ran over estimates four times this small scale nuclear pathway has had and is having obstacles to move from a hypothesis to reality. ( sources BBC future articles)

I think we need to get used to Nuclear being in the Energy Mix

At present, I am left with a great question raised in an article I was reading for this post, “How many renewables does it take to replace a nuclear plant.”

Visual Source: Seaborg Technologies

I think we will see an innovative combination of an advanced sodium fast reactor with energy storage, sited on utility sites, disused land, old coal mines to give power security and jobs.

These energy combinations can allow the reactor to operate at a high capacity while simultaneously capturing and storing electricity and plugging into supporting the increased use of hydrogen, working alongside renewables.

The future design of energy systems will be modular, not based on one fuel or power generation but 8utilizing multiple options to be optimal in energy delivery and best pricing, solution mix to customers.

We do need all the carbon-free power we can lay our hands upon.

We need carbon-free power, true zero, not clean power credits or fossil fuel and CCUS capture, giving us in the future carbon headaches or nothing but wind farms and solar farms stretching out over land and sea.

We need as many options for viable, alternative clean fuel, and that seems to be including Nuclear in my mind, sitting alongside green Hydrogen from Electrolysis, as equally primary sources of our clean energy needs, competing with the Renewables, the current green flavours of this decade.

One last visual supplied by Seaborg Technologies needs some time to study

Visual Source: Seaborg Technologies


The 2030 decade is going to be Nuclear and Hydrogens time

As we face Nuclear closures worldwide, we need to evaluate and hopefully achieve a next-generation Nuclear solution, which seems to be based on small modular reactors based on the Molten Salt design.

We are rapidly gaining a real understanding of the need for a phenomenal range of clean energy solutions to displace Gas, oil, and coal totally. In my opinion, we must include another clean energy source, Nuclear.

We need to rapidly find solutions to phase out old Nuclear Plants and not extend them even further. We need to determine a new Nuclear policy that establishes small modular reactor designs. The approach through the molten salt reactors shows real promise to accelerate as that safer Nuclear option.

It is interesting; in the past Salt was always prized as a commodity. Now it is part of a clean energy solution. It certainly adds flavor to the debate!



*Sources for initial descriptions: Wikipedia/ Molten salt reactors and for Thorium-based energy

*Thanks to Seaborg Technologies, they got me really interested and excited about the landscape of tomorrow and how Nuclear has a real fit as and when the present technologies become commercialised in or by the 2030s.

*If there are any errors in descriptions or understanding, they are mine. In this research and investigation, I do not claim a depth of knowledge. This is only a “snapshot” to raise awareness and interest.

Bob Meinetz's picture
Bob Meinetz on Jun 17, 2021

Paul, it was Thorium-Fueled Underground Power Plant Based on Molten Salt Technology, a 2004 paper by Edward Teller and Ralph Moir, that re-ignited interest the Molten Salt Reactor Experiment (MSRE), a project at Oak Ridge National Laboratory from the 1960s. 

Funding for MSRE, involving a reactor using uranium-233 mixed with molten fluoride salts as fuel, was eventually cancelled in favor of research on power reactors using prevailing pressurized-water (PWR) technology. Reasons for cancelling the project are the subject of much current debate. But two MIT engineers who launched Transatomic Power, a 2011 startup which sought to bring an MSR to market, discovered the challenges to be more daunting than anticipated, and dissolved the company in 2018.

Though the concept has developed a quasi-religious following many challenges remain. Veteran nuclear engineers believe it to be feasible, but argue the wealth of experience with PWRs and developments in "passive safety" technology make them largely unnecessary. A key consideration is availability - given current development timelines, MSRs would not be ready for commercial deployment soon enough to meet the immediate need to address climate change.

Paul Hobcraft's picture
Paul Hobcraft on Jun 19, 2021

I was wanting to get your thoughts on this Bob- thanks

My research indicates we are not so far away, deployment in the next decade, with Green Hydrogen at scale "just" ahead.

Maybe I'm wrong. Challenges remain in all these technologies we have, dismissed simply just needing scale. I find that a little simplistic.

I do feel the veteran ,might need to rethink "energy warfare". Modular, decentralized, based around communities, small, safer than we have makes for a more mobile and socially acceptable alternative perhaps? The shift from heavy bombers to nimble "attack" is my reaction when you mentioned veteran thinking.......we know what we know and often reject what can be real alternatives.

Bob Meinetz's picture
Bob Meinetz on Jun 19, 2021

You may be right, Paul. I feel waiting for "the next big thing" has become a stalling tactic, though, and is encouraged by natural gas interests to enable the continuation of  business-as-usual indefinitely.

For example: during last year's presidential campaign, advisors told Joe Biden the first step to lower carbon emissions would be to support existing nuclear plants with subsidies - that without them, reaching zero carbon by 2035 would be impossible. So in August 2020, they took heart when Biden promised his new "Clean Energy Plan" would

"continue to leverage the carbon-pollution free energy provided by existing sources like nuclear and hydropower..."

Fast forward 11 months. Biden is now president, and the budget for his proposed Clean Energy Plan includes no financial support for existing plants,  only funding for

"advanced nuclear reactors, that are smaller, safer, and more efficient at half the construction cost of today’s reactors..."

Why Biden's statement amounts to lip service:

• "Advanced nuclear" has long been a euphemism for technology that doesn't exist in the present - aka, "technology that will be ten years away for the next fifty."

• Given not a single Gen-2 reactor in U.S. nuclear plants now has melted down, released radiation to the environment, or resulted in a single casualty, it's hard to imagine how any advanced reactor could be safer.
• By taking advantage of significant economies of scale, both financial and energy efficiency is improved by making reactors larger, not smaller.

"The shift from heavy bombers to nimble 'attack' is my reaction when you mentioned veteran thinking...we know what we know and often reject what can be real alternatives."

Don't confuse scale with fission technology. Veteran nuclear engineers tend to be very excited about NuScale's Small Modular Reactor (SMR), which puts well-understood pressurized water reactor (PWR) technology in a smaller, less reactive, less expensive package. In many ways, NuScale will be the best of both worlds.

When I toured NuScale in 2017 founder/inventor José Reyes spoke to our group. During Q&A, I asked him what he would tell someone who might question whether NuScale's design would be any faster to develop than molten salt, or an integral fast reactor, or...?

Reyes answered quickly. "We've been working on our SMR since 2003. There is literally nothing standing in the way except for design certification by the NRC," he said. "We could start building one tomorrow."

Michael Keller's picture
Michael Keller on Jul 6, 2021

As a nuclear engineer, the technical, operational, safety, and licensing issues associated with molten salt reactors are legion. These problems represent significant financial risks.


Paul Hobcraft's picture
Thank Paul for the Post!
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