Micro Reactors: A Critical Look at “Going Critical”

I’m able to believe that the newest small reactors are much safer than previous designs.
What I continue to do is calibrate expectations on what these reactors will do, how much they cost, and when they will be available.

Duke Energy:

Given the substantial upfront capital investment required for deployment of new nuclear generation (relative to other types of generation), support will be required in the form of cost overrun protection, which currently does not exist, or other cost mitigation measures. Units 3 and 4 at Plant Vogtle were the first advanced reactor LLWR projects in the U.S. with two AP1000® units constructed and placed into commercial operation. 

The Vogtle project experienced significant delays and cost overrun, with the total cost more than double the original projected cost. Though some issues were unique to that project, the first and second movers for the next advanced reactor projects will be assuming construction risks and therefore will need some form of insurance to protect customers.

It is essential that the current tax credits that incentivize new nuclear generation remain in place, as they provide critical financial support for these investments and decrease investment risk, which will lead to lower overall costs for customers. In addition, the current tax credits that incentivize the efficientoperation of the existing nuclear fleet are also essential, as they help keep energy prices low, with every dollar going back to customers. Further, the federal loan guarantee program, federal grant opportunities, and other mechanisms like public-private partnerships could provide crucial support.

Given the risks and long-lead time associated with constructing new nuclear, cost overrun protection would further decrease investment risk in a manner that would benefit customers.

In sum, without continued federal support, the financial risk of nuclear construction could deter development, slowing, delaying, or eliminating progress despite the substantial potential benefits of new nuclear generation for customers. Importantly, because Duke Energy is a regulated utility, federal support directly benefits customers in the form of lower rates and lower overall financing costs.

Barrons:

The top federal official in charge of giving loans to nuclear plants had some harsh words this week for nuclear industry officials who want the government to invest more taxpayer funds into building reactors.

“At a certain point, it’s just greedy,” said Julie Kozeracki, the acting chief investment officer for President Donald Trump’s Office of Energy Dominance Financing.

Kozeracki was speaking in front of hundreds of nuclear industry CEOs and financiers on a panel at the Nuclear Energy Institute’s finance conference in New York on Tuesday. She told them the industry needs to stop asking for new funding streams from the government and start building reactors. “The tools are there, and it’s time to deliver,” she said.

Trump has called for the U.S. to start construction on 10 large nuclear reactors by 2030, to produce enough electricity to meet growing American energy demands, including the power needed by artificial intelligence data centers. That goal is likely to cost well over $100 billion, almost all of it paid by private companies.

Duke Energy is one of the largest operators of nuclear plants in the US. Above is their deployment plan for their first Small Modular Reactor, Belews Creek, from the 2025 Integrated Resource plan. The first planned reactor would go online in the 2036-37 time frame, a total of 300 MW capacity.
Meanwhile, the plan also envisions at least 4000 MW of solar by 2034.

Energy Secretary and Fracking Baron Chris Wright keeps saying that nuclear plants will be “going critical” this summer, as if this means that some nuclear renaissance is fully underway, but there is less here than meets the eye.
I asked two AIs for a fact check.

Google Gemini:

Energy Secretary Chris Wright’s announcement refers to microreactors and advanced small modular reactors (SMRs) that are hitting critical milestones ahead of the July 4th deadline mandated by President Trump’s Executive Order 14301.

The exact reactors, their sizes, and their power-generation timelines are detailed below.

  1. What Reactors Are They?
    The Energy Department is tracking up to four distinct, privately developed “non-light-water” test reactors hitting criticality under the DOE Reactor Pilot Program:
  • Antares Nuclear “Mark-0”: This reactor officially became the first to achieve “zero-power” criticality at the Idaho National Laboratory (INL) on June 4, 2026. It uses a sodium heat-pipe-cooled system and high-assay low-enriched uranium (HALEU) TRISO fuel.
  • Aalo Atomics “Aalo-X”: A sodium-cooled test unit currently targeting first criticality.
  • Radiant Nuclear “Kaleidos”: A helium-cooled microreactor preparing for testing inside INL’s renovated dome facility.
  • Valar Atomics: Another selected pilot reactor design that received preliminary safety design approval to test.
  1. How Large Are They?
    These are not massive traditional power plants; they are ultra-compact microreactors and miniature SMRs designed to fit on trucks and inside shipping containers.
  • The Test Units: The immediate prototypes (like the Mark-0) are “zero-power” or thermal-only units. They generate heat for physical validation rather than electricity.
  • The Commercial Scale: When these models scale up to commercial production, they will remain small. For example, Radiant’s Kaleidos targets 1.2 Megawatts (MW) of output, while Aalo’s subsequent commercial design (the Aalo-1) targets 50 Megawatts-electric (MWe).
  1. When Will They Generate Significant Power?
    While reaching criticality means the nuclear chain reaction is self-sustaining, none of the reactors turning on this summer will generate immediate grid power.
  • Late 2027: Antares Nuclear expects its subsequent iterations to begin producing initial electricity by late 2027.
  • 2028: Commercial site deployments and field operations for microreactors like Antares and Radiant are slated to begin.
  • 2029–2030: Commercial grid-scale versions, such as Aalo Atomics’ 50 MWe

ChatGPT:

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