As of now, “nuclear energy” in practical contexts refers to fission, or splitting heavy particles to generate massive loads of energy. The goal is to eventually transition to fusion, which combines two light particles, also to produce enormous power but at a lower environmental cost.
Each fossil fuel alternative generally has its own share of detractors and ongoing issues, but the debate over nuclear power is among the most prominent, at least from a publicity standpoint. That said, nuclear energy is undoubtedly a robust, high-stakes industry with rapid developments. Governments often get involved, and the balance between innovation and safety is always a significant problem.
Meanwhile, the current administration seems keen on ramping up America’s nuclear power capacity, including initiatives to bring microreactors—small, transportable nuclear reactors—to U.S. grids in remote locations, military bases, and commercial operations. Microreactors aren’t necessarily new; they were conceived in 1939 for military use, and NASA demonstrated a small, lightweight nuclear system for spacecraft in 2018.
But the push to bring them to civilian settings gained traction last year with the Department of Energy (DOE)’s DOME initiative, whose pilot projects are slated to start as soon as spring 2026. So we’ll surely hear more about microreactors soon.
In this Giz Asks, we asked various experts and stakeholders to help us understand the state of microreactors. Will their benefits truly outweigh their costs? What are some real advantages of microreactors? Or perhaps more importantly, what are the risks? Should we be hyped—or freaked out?
The following responses may have been lightly edited and condensed for clarity.
Ralf Kaiser
Experimental nuclear physicist, International Centre for Theoretical Physics; former head of physics research at the International Atomic Energy Agency.
Nuclear reactors have not seen much technological progress for quite some time. Small modular reactors (SMRs) offer a way for safer and more modern technologies to get to the market. So that’s a good thing. The original idea for SMRs was also to mass-produce them and deliver them sealed, run them for some decades and then simply exchange the entire reactor. While most current, getting closer to application, SMR concepts do not follow this idea any longer. I still think it was a good idea.
SMRs can also be used for other applications than the production of electricity, e.g. for process heat in industry. Smaller reactors can also be used for maritime propulsion—replacing diesel engines for large container ships. Microreactors are also crucial for space, i.e., future bases on the Moon or Mars.
Edwin Lyman
Director of nuclear power safety, Union of Concerned Scientists.
We should all, without question, be freaked out about microreactors. Why? Because, like so many other worthless or dangerous products being foisted on the public by an out-of-control tech industry, this is an “innovation” that no one asked for and no one needs. Microreactors are wildly uneconomic, and if deployed anywhere near the scale their boosters are hoping for, they will raise power prices for everyone.
Even worse, because microreactors will be so expensive, their developers are looking to cut corners every way they can—at the expense of public health, safety, and environmental protection. If approved by compliant regulators, these reactors would lack the backup cooling systems, radiation shielding, and containment structures of conventional reactors. They could be located closer to populated areas and would be staffed by skeleton crews of operators and security officers—if any at all. And with little or no protection, in the wrong hands, a microreactor could become a potent terrorist weapon.
Fortunately, there is no need to panic: the likelihood that microreactors will be coming to your neighborhood any time soon is not high. The unrealistic development timelines that microreactor companies are trying to meet will virtually guarantee that the first generation will be balky and unreliable at best and too dangerous to operate at worst. Any microreactors that are deployed are likely to remain curiosities—more of a hindrance than a help to any customer needing dependable and affordable power.
John Jackson
National technical director, U.S. Department of Energy’s Office of Nuclear Energy Microreactor Program.
What’s really compelling about microreactors is their relative simplicity and versatility. You can transport one by truck or rail car, so you can bring reliable power to places that have historically had high energy costs or have been too difficult to access, such as military installations, remote rural communities, natural disaster recovery bases, or industrial sites. They’re being designed to operate for several years without refueling, to self-regulate, and to be fully factory-built and installed on-site. That’s a very different value proposition than traditional nuclear, and it opens energy access pathways we haven’t had before.
That said, there are real hurdles to work through. Upfront costs are somewhat high, but as more units are built, manufacturing processes will mature and should bring those down significantly. With Idaho National Laboratory actively testing and validating new designs, strong federal backing, and demonstrations expected within the next year, I think there’s genuine reason to be excited about where this technology is headed.
Carlos Romero Talamas
Founder and CEO, Terra Fusion, a Maryland-based nuclear energy startup.
The answer depends on whether you are talking about fission or fusion microreactors. Fission has serious safety challenges in its entire life cycle, from mining and refining to waste disposal. Radioactive waste from fission can be highly toxic for thousands of years, and the same equipment used to refine the fuel can be used to make weapons-grade material. Additionally, fission cores have enough fuel to last for months or even years.
Even if they are designed such that the core cannot become supercritical (i.e., have a meltdown), the stored potential energy is enormous, and in a serious accident scenario there is a chance of radioactive contamination that could affect large areas. Secure end-of-life disposal for fission systems continues to be an unresolved issue, regardless of the system size.
Fusion energy microreactors, in contrast, are not yet available but will be extremely safe. The reactors will only hold a few seconds worth of fuel in the core during operation, such that the stored potential energy is many orders of magnitude less than in the fission case. Even if these systems carry enough fuel for years of operation, the fuel can be easily isolated in tanks with safety redundancy.
The first-generation systems will use deuterium and tritium, both of which are isotopes of hydrogen, but only tritium is radioactive (and deuterium is naturally present in water… we drink it every day!). Lithium can be used to produce tritium in the microreactor, so the primary fuel supplies are non-radioactive and can be transported with conventional freight (no need for armed guards!). The byproduct from the fusion of deuterium and tritium is helium, which is harmless and not a greenhouse gas.
The decay energy of tritium is low enough that, once inside a container (e.g., an industrial gas bottle), you wouldn’t even know the contents are radioactive. Some components from fusion systems could become radioactive during operation, but their decay is relatively fast: after a couple of years to at most a few decades of ‘cooling,’ these components could be safely recycled.
In either case, fission or fusion, we need to have a proper regulatory framework and oversight for the entire life of the systems, but fusion will definitely be safer and easier to manage. You can be cautiously optimistic about fission systems but definitely enthusiastic about fusion microreactors!
