Mass-produced floating nuclear reactors use ultra-safe molten salt fuel
Copenhagen-based startup Seaborg Technologies raised eight-figure dollars to start building a fascinating new type of cheap, portable, flexible and super-safe nuclear reactor. The size of a shipping container, these compact molten salt reactors will quickly be mass produced in the thousands, then placed on floating barges for deployment around the world – in a timeframe that will shatter industry paradigms. energetic.
Like other molten salt reactors, which have been around since the 1950s, they are designed to minimize the consequences of accidents, with a pair of very careful passive safety measures that the company says can dramatically change the equation of life. safety at the heart of any nuclear power plant. investment.
First, they use nuclear fuel mixed with fluoride salts. The suit is liquid above 500 ° C (932 ° F), which allows it to flow through the reactor, which operates at pressures close to atmosphere. This liquid salt functions as a coolant for nuclear fuel, replacing high pressure water cooling in older reactor designs. But if this fuel is exposed to air, instead of explosively venting off as a vapor, it acts like lava and solidifies into rock.
Yes, the rock is radioactive, and you shouldn’t go picnicking on it, but it’s not a cloud of radioactive gas that can blow across the continent; it is solid rock that can be cleaned by security teams with Geiger counters. It also has very low solubility in water, so it is relatively safe even if it falls into the sea.
Second, if the temperature starts to get out of hand for some reason, a plug of “frozen salt” at the bottom of the reactor is the first thing that will melt, and this will immediately drain the reactor core into a series of cooled drain tanks below. . .
This pair of simple measures, says Troels Schönefeldt, co-founder and CEO of Seaborg Technologies, radically refocuses the issue of nuclear safety away from total accident prevention with four levels of redundancy at each point of failure, towards much more mitigation of consequences. simple, and it’s “This will have a huge impact on the cost of nuclear power.
“We take a different approach,” he told Radio Spectrum in an interview. “We are not reducing the probability of an accident to zero, there will be accidents. We should avoid them as much as possible, but there will be accidents. Hopefully there will be a lot of accidents because we will have them. a lot of these reactors. What we’re doing, instead of reducing the probability, is reducing the consequences of the worst disasters. Or even acts of war where you actually bomb the reactor. The consequence is that this fluoride salt s ‘will flow out of the reactor, or explode out of the reactor and lie down on the ground. It will solidify. And now you shouldn’t be going on that ground. You should actually keep 10 or 20 feet away. But you can go there. go with a Geiger counter and clean it. It’s extremely expensive, but you can do it. And it changes the fundamental safety profile of the technology. And in doing so, we change the cost, which in turn changes the model. commercial.
But perhaps the most impactful change in the business model is Seaborg’s proposal to put these reactors on barges and float them offshore rather than buying land to develop nuclear power plants. There are several advantages here. For starters, you can bulk make them in one facility. Seaborg examines Korean shipyards, which are already tightly and efficiently connected to supply chains with enormous production capacity. “If you want us to build not a reactor to start, but a thousand, we could start by building a thousand,” Schönefeldt told Radio Spectrum. “It’ll take, like, three or four years at these shipyards. So the speed at which you can scale it is basically roofless.”
These barges can be moved just about anywhere on the planet, whether they are moored offshore or on large or small rivers, depending on the size of the reactor. There is virtually no site preparation required; it is fully autonomous and very easy to connect to an electrical network. Seaborg estimates that it can serve 95% of the world’s population this way, requiring virtually no land for a basic or load-following power plant of up to 600 MW, which could power nearly 100,000 homes.
The challenge here, as with all molten salt reactors, is corrosion. Hot molten salt itself is highly corrosive, and it will be a serious challenge to design for every component that comes in contact with the fuel salt. Float the reactors on barges in salty sea water and you also expose the whole exterior to a strong corrosive agent; Freighters are generally designed with a lifespan of 25 years in mind through the effects of living in salt water.
And it doesn’t stop there for Seaborg. Other molten salt reactors use graphite as a moderator, slowing down the neutrons produced by each fission reaction to maintain the chain reaction. But graphite has a tendency to fracture and weaken when exposed to intense radiation with repeated heating and cooling, which ultimately resulted in what Seaborg co-founder and CTO Eirik Eide Pettersen describes at Thomas Thor Associates as “unacceptable hot spots”.
Seaborg’s solution involves using another molten salt – sodium hydroxide – as a liquid moderator. Thus, the core design places the tube of combustible salt inside a larger tube filled with sodium hydroxide, creating a unique all-liquid reactor that is remarkably compact. But sodium hydroxide itself is a powerfully caustic base, often used as an oven cleaner or as a drain cleaner; the Seaborg design must also deal with this added corrosive agent.
And on top of all that, there is the bizarre phenomenon of “grain boundary corrosion” to start, caused by the presence of tellurium as a fission byproduct in the combustible salt stream. Tellurium atoms can happily penetrate through metals and swap positions with other elements, causing metals to weaken at their weakest points.
The company is well aware of its main challenges here. “Seaborg’s core intellectual property is based on controlling corrosion in moderating salt and applying lessons learned since the 1950s,” Pettersen explains. “But it’s not just about corrosion, it’s also how easy it is to put these things together. Practical experience is important. They need to be welded, tested, inspected, maintained. have maybe 20 or 30 test loops in Copenhagen, with the experiments designed, set up and executed. Conceptual design is already done; we are now working on the basic design and in this way we are working on a prototype to large scale.
This large-scale prototype is currently expected to go live in 2025, when it will likely be sent to work on an island in Southeast Asia. Having raised reasonably substantial capital, Seaborg is hiring like crazy to work towards this goal. It hopes to get regulatory type approval for its design by 2026, and commercial mass production could follow as early as 2027.
These delays are “almost insane” in the energy market, Schönefeldt told the Switch 2020 audience in a presentation earlier this year, and a validation of the mass production strategy and floating barge approaches. Investors in the energy sector, accustomed to extremely long planning and construction phases, as well as decades of payback periods of several decades, can now invest their money in something that is online incredibly quickly and which pays for itself in 6 to 10 years.
The Seaborg Reactor is small enough to fit in a shipping container, making it remarkably easy to move, even for ground installations. It will operate for approximately 12 years without refueling. Its fuel cannot be used in nuclear weapons. It is capable of operating with refined and recycled nuclear waste from older reactors – although there are some regulatory hurdles there, Schönefeldt says. You can draw heat directly from the reactor even more efficiently than draw electricity, so it will be useful for other purposes than just being a power plant.
Next-generation advanced nuclear power is a hot topic right now. With the global determination hardening around the goal of zero carbon emissions by 2050, coal and gas-fired power plants are quickly being phased out. Renewable resources like solar and wind power will provide most of the energy we need to move forward, but nuclear offers a reliable, cheap, and environmentally friendly way to boost baseload and fill the shortcomings when renewables do not produce.
Despite some high-profile disasters, nuclear is already by far the safest method of generating electricity, with a “lethal footprint” 330 times smaller than that of coal-fired electricity. The new generation of advanced nuclear reactors promise to be even safer, and molten salt designs like Seaborg’s can also significantly reduce the consequences of these extremely rare incidents. If this company can solve corrosion problems as effectively as its investors think, it could be a game-changer.
Source: Seaborg Technologies via IEEE Spectrum, Thomas Thor Associates and Switch 2020