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For SpaceNut ... we did not appear to have a topic devoted to small modular reactors.
This topic is offered for NewMars members who might wish to contribute links, images and text about the growth of this important industry. We will open with a report of Canada (Ontario) planning to build four SMR systems.
https://www.msn.com/en-us/news/world/of … 4e65&ei=49
Canada is leading the Group of Seven in developing new nuclear energy technology with the construction of the first of four small modular reactors in Ontario, the Associated Press reported.
The government's Ontario Power Generation will proceed with its plan to construct the first of four SMRs at its Darlington nuclear site. It will be North America's first commercial, grid-scale reactor and is expected to be in service by the end of 2030, supplying low-carbon power to about 300,000 homes.
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This post is reserved for an index to posts that may be contributed by NewMars members over time.
Index:
Post #3: Calliban re reactor type
https://newmars.com/forums/viewtopic.ph … 91#p232091
Also see: https://www.gevernova.com/nuclear/carbo … ar-reactor
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Although the article doesn't mention them by name, the SMRs are BWR-300X units. So far, I have seen only limited concept design information on this reactor type. But it does appear to be very compact for the amount of power it produces. This reactor could be useful for powering a Martian base. Unlike PWRs, the BWR does not require bulky heat exchangers. That is a significant weight saving.
All LWRs have comparable thermodynamic efficiency: 30-35%. The remainder is waste heat, which is warm water at 30°C. This could have uses for district heating on Earth. It could have uses on Mars as well.
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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SMRs would be a great capability to have, and absolutely necessary for powering colonies on Mars. Unfortunately, every one of these designs has ultimately gone nowhere in about 5 to 10 years time. A bunch of money is spent to construct a scale prototype, and then for reasons unknown to me we never drag the finalized design across the finish line where the first commercial units are certified to start producing electric power. That's a shame because a number of innovative designs, arguably safer / easier to use / easier to maintain, have been on offer. The closest thing to a SMR we have are the nuclear submarine reactors, and all of those seem to work quite well, decade after decade.
I don't know if the hurdle is a regulatory issue or because the companies involved in SMR design lack the depth of engineering talent or financing talent or something else like institutional bias against smaller reactors. I'd be quite pleased if this time is different and we end up with real tangible hardware, ready to deploy to remote locations around the world and on other planets. I know that many of the engineering challenges are the same regardless of reactor power level, but SMRs must also have some unique challenges of their own.
Maybe someone can speak to the engineering issues unique to SMRs. I listened to a YouTube podcast on Decouple Media where a US DoE expert was talking about working with various reactor designers to evaluate the technical merits / demerits of SMR designs. He talked a lot about cooling the reactor and operations, especially maintaining the balance-of-plant for SMRs, which is apparently a bit of an issue due to close proximity to the operating reactor. My gut-feel on this is that maintaining the power turbine and electrical equipment is something of an afterthought in these highly integrated reactor designs, and that the inability for a human worker to go physically tweak components makes them unreliable from the standpoint of having to shut down the reactor to work on everything else that is not the reactor itself.
The gist of the conversation on Decouple Media is that when you design a SMR, even if the reactor core itself is readily truck-transportable, we're going to stuff that reactor into a subsurface concrete containment structure with a bunch of infrastructure built on top of it, just like a conventional power plant. The net-net is that the reactor core and electric generating equipment is transportable by truck or rail, but the facility that will operate the reactor is not transportable in any sense of the word. It's a fixed site that involves excavation and must be fabricated over multiple months. The upside is that following fuel depletion the reactor itself can then be returned to the "reactor factory" for refueling and refurbishment, so there's no pile of fuel rods that accumulates onsite the way they would with a traditional GW-class PWR or BWR. This approach is "cleaner" in the sense that the fuel stays inside the reactor core and will never leave the core while the reactor is on onsite.
I think the key to making these reactors profitable is operating them at elevated temperatures and using sCO2 turbines so that the balance-of-plant is tiny and doesn't require a fresh water supply. I don't think most people recognize how great a technological windfall it is to have "steam turbine equivalents" that are 10 times smaller than steam turbine equipment and don't need a water supply. So long as you can deliver the materials to fabricate the power plant facility, to include the power transformers / switching yard / power lines, all the rest of the equipment can be trucked into and out of the facility. That is simply not feasible using steam turbines and traditional GW-class reactors, which must be fabricated onsite over 5 to 10 years. It should be possible to get a SMR facility up and running over 2 years.
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This post is about a research reactor at Purdue University. The innovative concept reported is a digital model of the physical small reactor that allows digital control of the reactor with 99% accuracy. The concept sounds (to me) a bit like fly-by-wire control of an air or space craft. The reactor itself is described as small enough for use at a remote site.
https://www.msn.com/en-us/money/other/u … 3631&ei=16
This breakthrough is already making waves.
A closet-sized nuclear reactor buried beneath Purdue University's campus may hold the key to revolutionizing the future of clean energy, according to a report by Power Engineering. Known as PUR-1, this tiny but mighty reactor is the first in the U.S. licensed to operate with fully digital controls. It's now serving as a live test bed for innovations such as artificial intelligence, quantum encryption, and remote operation technologies.
What makes this development so exciting is its potential to transform how nuclear power is managed, especially for the next generation of compact and autonomous reactors. These small modular reactors could one day bring clean, affordable energy to remote communities, industrial sites, and disaster zones — all with lower operational costs and fewer staff.
Expand article logo Continue reading
At the heart of the work is what Purdue University calls a digital twin: a real-time, AI-powered replica of the reactor that receives live data and can predict performance changes with 99% accuracy, according to a study published in Scientific Reports. "Having a digital twin connected to a live reactor is something no other university has," said Seungjin Kim, facility director of PUR-1 and head of Purdue's School of Nuclear Engineering, to Power Engineering.
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we have many posts about this size of reactor that puts out to much power
AI Overview
What Are SMRs: What Small Modular Reactors Are And Why They ...
Small modular reactors (SMRs) are advanced nuclear reactors with a power output of up to 300 megawatts that are designed to be factory-built as modules and then transported to a site for assembly. They offer potential benefits like streamlined construction, greater scalability, flexibility in siting, and enhanced safety features that often rely on passive cooling systems. SMRs are envisioned as a way to provide carbon-free energy for various applications, including powering communities, industrial facilities, and data centers, and can be deployed in configurations to match energy demand.
Functionality and technology
Power output: SMRs have a capacity of up to 300 MWe, about one-third of a traditional nuclear reactor, with some designs as small as 1-10 MWe.
Nuclear fission: Like traditional reactors, SMRs use nuclear fission to generate heat, which can then be used to produce electricity or for other industrial applications like desalination.
Modular construction: Components are manufactured in a factory and then shipped to the site, which is intended to reduce construction costs and time compared to large, custom-built plants.
Scalability: SMRs can be deployed in single or multi-module configurations to meet varying energy needs, a concept called "economy of multiples".
Advantages and benefits
Flexibility: The smaller size allows for siting in a wider range of locations where large plants might not be feasible.
Safety: Many designs incorporate passive safety systems that rely on natural processes, like convection, for cooling, which reduces the reliance on active mechanical components.
Cost and time: The goal is to achieve lower initial capital costs and faster deployment timelines through factory production and standardization.
Versatility: Beyond electricity generation, SMRs can be used for process heat, water desalinization, and other industrial applications.
Carbon-free energy: As a nuclear technology, SMRs provide a source of reliable, carbon-free power.
Challenges and considerations
Economic viability: While proponents aim for cost savings, some projects have faced significant cost overruns, and it is unclear if the "economy of multiples" will be cheaper than economies of scale for large plants.
Deployment: As of mid-2025, only a few operational SMRs exist, primarily in Russia and China, and many proposed designs are still years away from deployment.
Safety claims: The effectiveness of passive cooling systems is dependent on proper manufacturing and could be affected by environmental factors or defects.
Regulatory hurdles: SMRs face the same regulatory processes as traditional reactors, which can be a complex and lengthy challenge
but it seems that the miltary wants to cut the fuel strings that bind setting up bases.
Nuclear microreactors are smaller, factory-built power systems that use the same basic principles as traditional nuclear plants but at a fraction of the size. Most produce between one and 20 megawatts of electricity — enough to power a small town or a military installation — and can operate for years without refueling.
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Here is another update about SMR reactors ... This one is about a permit issued in Tennessee:
The bottom line is that this is just a construction permit. The actual reactor is years away. It appears that investors are putting money into this in hopes it pays off years from now with cookie cutter duplicates after the first unit goes online.
https://www.yahoo.com/news/science/arti … 21628.html
America’s First Small Modular Reactor Just Got Permission to Break Ground
Annemarije de Boer
Thu, October 1, 2026 at 1:03 PM EDT
1
America's First Small Modular Reactor Just Got Permission to Break Ground
Image: GE VernovaThe U.S. Nuclear Regulatory Commission issued a construction permit for a GE Vernova Hitachi BWRX-300 small modular reactor at TVA’s Clinch River site in Tennessee, marking the nation’s first commercial small modular reactor.
On September 29, 2026, the U.S. Nuclear Regulatory Commission issued the Tennessee Valley Authority a construction permit for a GE Vernova Hitachi BWRX-300 small modular reactor at TVA's Clinch River site in Roane County, near Oak Ridge, Tennessee. The NRC described the approval as clearing the way for "the nation's first commercial small modular reactor." One qualifier matters immediately: this permit authorizes
construction, not fuel loading, not generation.What the Permit Actually Means
A green light to build, with a separate operating license still required before the reactor runs.
The NRC completed its safety review in 14 months, four months ahead of its own schedule. TVA must still obtain a separate operating license before the reactor can generate power.
No construction start date has been announced. No final project cost has been disclosed. TVA is evaluating up to four BWRX-300 units at Clinch River, but the current permit covers only the first.
TVA interim president Mike Skaggs called the approval "foundational for America's nuclear future," according to The New York Times. A primary-source TVA transcript was not available in the sourced materials. The NRC's own release confirmed GE Vernova Hitachi's description of this as the first U.S. construction permit issued for the BWRX-300 design.
The reactor itself is built on established technology. Key specifications include:
300-megawatt output, roughly one-quarter the capacity of each of Vogtle's newest large reactors, per The New York Times
Boiling-water design based on decades of commercial nuclear operation
Passive safety systems using gravity, pressure, and stored water
Natural circulation cooling that reduces dependence on powered backup equipment
The AI Power Equation and the Unanswered Cost Question
Nuclear fits the data-center load profile, but Clinch River is years away from delivering anything.
Many AI data-center operations require continuous, firm electricity. Solar and wind generation is weather-dependent; firming that output may require storage or backup generation. Nuclear plants can provide steady output regardless of conditions, which is why utilities and technology companies are watching this permit closely.
Clinch River is not close to an answer for today's power crunch. The gap between a construction permit and electricity on the grid could span years of site work, equipment manufacturing, further licensing, and commissioning.
Repetition is the commercial bet behind the BWRX-300. If TVA and Ontario Power Generation, which is preparing to build the same design at its Darlington site in Canada, can establish a reliable construction playbook, procurement and manufacturing costs could fall with each subsequent unit.
That is the industry's rationale. It remains largely untested at U.S. commercial scale.
The cautionary benchmark is Georgia's Vogtle plant. Its two newest reactors cost roughly $35 billion combined and arrived years behind schedule, according to The New York Times. The SMR industry argues that smaller, standardized units built more like manufactured products than one-off construction projects could avoid that outcome. Clinch River is where that argument meets reality.
A separate project from Blue Energy proposes pairing up to five BWRX-300 reactors with GE Vernova gas turbines to supply a Texas data-center campus directly, with a final investment decision targeted for 2027, per Blue Energy's project announcement. Five units at full output would total 1,500 megawatts, comparable to a large conventional power plant.
The construction permit sets a regulatory precedent that no U.S. utility has reached before with this design. The test that actually matters is whether Clinch River can establish a credible cost and schedule benchmark. The project could influence how utilities and data-center developers assess similar reactors for years to come.
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