## Has SM-1, the U.S. Army's First Nuclear Reactor, Been Fully Decommissioned?

Yes. The U.S. Army Corps of Engineers, Baltimore District announced last week that it has completed all field activities associated with the decommissioning and dismantlement of SM-1 at Fort Belvoir, Virginia — closing the book on a project that began in 2020 and a nuclear lifecycle that, from initial design work in 1954 through final dismantlement in 2026, spanned approximately 72 years.

SM-1 holds a specific place in U.S. nuclear history: it was the Army's first reactor and, according to both the Army Corps of Engineers and contemporaneous reporting in *Nuclear News*, the first facility to provide nuclear-generated power to the commercial grid for a sustained period. The reactor entered operation in 1957 and was deactivated in 1973, after which it sat in a partially decommissioned state for decades before final field activities commenced in 2021.

The completion marks the end of a decommissioning project that field teams described as focused primarily on activated metals and components rather than fuel — the nuclear fuel and control rods having been removed in the 1970s. For the broader advanced nuclear industry, SM-1's full lifecycle offers a concrete data point on what "cradle to grave" nuclear program management actually looks like at government scale.

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## The Army Nuclear Power Program and SM-1's Origins

SM-1 did not emerge in isolation. It was the first reactor deployed under the Army Nuclear Power Program (ANPP), which the secretary of defense authorized into existence two years after Maj. Gen. Kenneth Nichols — former deputy commander of the Manhattan Project — became chief of the Army Office of Research and Development in 1952 and commissioned two feasibility studies on nuclear power, both of which returned positive findings.

The ANPP's stated mission was the development and application of land-based nuclear power plants for the Army, Air Force, and Navy. But the program's technical ambitions, as documented in the October–November 1960 issue of *Nuclear News*, extended well beyond simply generating electricity. Objectives included increasing reactor core power and life, simplifying and ruggedizing components, reducing operating staff requirements, improving transportability and relocatability, cutting on-site construction time and costs, and achieving standardization — all while driving down both initial and operating costs.

Those objectives will read as strikingly familiar to anyone following today's SMR development pipeline. The economic logic articulated in that 1960 *Nuclear News* article — that even remote and military applications must ultimately "bear the scrutiny of the hard cold facts of economic life" — is precisely the argument utility executives and DOE program managers are having about [First of a Kind (FOAK)](https://smrintel.com/glossary/foak) reactor deployments in 2026.

The logistical case for nuclear that the ANPP made then is equally resonant now. *Nuclear News* noted at the time that a single core loading for an SM-1 type plant was equivalent to 60,000 barrels of fuel oil — roughly the capacity of a medium tanker — while the nuclear fuel core itself weighed approximately 800 pounds and could be carried in a single C-47 aircraft. That is the same supply-chain argument being made today for microreactors and mobile nuclear units targeting forward operating bases and remote industrial sites.

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## Decommissioning: A Long Road From Shutdown to Site Release

SM-1's decommissioning timeline illustrates a pattern familiar to anyone tracking nuclear plant end-of-life costs and schedules. The reactor was deactivated in 1973. During the 1970s, nuclear fuel and control rods were removed, the reactor pressure vessel was sealed, and monitoring devices were installed. The plant then sat in that condition for decades.

Planning for final decommissioning began in 2014. Field activities did not actually start until 2021 — a seven-year gap between planning initiation and boots-on-ground work that reflects the regulatory, logistical, and funding complexity of nuclear decommissioning even when the heaviest radiological work (fuel removal) is already complete.

Rebecca Yahiel, project manager for SM-1's decommissioning, described the nature of the remaining work in a 2021 *Nuclear News* feature on the Army's Deactivated Nuclear Power Plant Program: "With the fuel and radioactive waste all removed in the 1970s, at this point our team will be dismantling and removing activated metals and components, so this is likely not what people think of when they think of radiological work."

The Army Corps of Engineers framed the completed decommissioning as serving an institutional learning function, stating that it "helps the Army understand the full life cycle of nuclear power."

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## Why This Matters for the Current Nuclear Build Cycle

The SM-1 closure is not merely a historical footnote. At a moment when the DOE is funding advanced reactor demonstrations, the Pentagon is pursuing microreactor deployments under Project Pele successors, and the NRC is processing design certifications for multiple SMR concepts, SM-1's full lifecycle provides a grounding reference.

Several dimensions are worth noting for industry stakeholders:

**Decommissioning liability is real and long.** From SM-1's 1973 shutdown to 2026 site completion is 53 years. Even with fuel removed early, activated structural components and the complexity of radiological characterization extend timelines — and costs — far beyond what early project economics typically model. Developers and utilities pricing SMR [levelized cost of energy](https://smrintel.com/glossary/lcoe) today should be building decommissioning trust fund requirements into their financial models with full seriousness.

**The military-nuclear interface has deep precedent.** Today's conversation about nuclear for data centers and remote industrial sites is new in some respects, but the ANPP was solving the same core problem — reliable, energy-dense power for installations that cannot depend on conventional fuel supply chains — in the 1950s. The program's emphasis on modularization, reduced operating staff, and transportability maps directly onto what companies like Oklo, Radiant Industries, and others are pitching to DoD today.

**The ANPP's economic discipline is instructive.** The program's insistence that even mission-critical applications must ultimately compete on economics is a useful corrective to the tendency in advanced nuclear circles to assume that national security or climate premiums will indefinitely subsidize above-market LCOE. SM-1's history suggests the military understood that constraint clearly from the beginning.

The Baltimore District of the Army Corps of Engineers, which houses the North Atlantic Division's Radiological Health Physics Regional Center of Expertise, led the SM-1 decommissioning work.

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## Key Takeaways

- The U.S. Army Corps of Engineers, Baltimore District completed all field decommissioning activities at SM-1, Fort Belvoir, Virginia, announced the week of September 14, 2026.
- SM-1 was the Army's first reactor and, per Army Corps of Engineers and *Nuclear News* records, the first facility to provide nuclear-generated power to the commercial grid for a sustained period.
- SM-1 operated from 1957 to 1973; final decommissioning field work ran from 2021 to 2026, with planning beginning in 2014.
- The full SM-1 lifecycle — from initial 1954 design through 2026 dismantlement — spanned approximately 72 years.
- The Army Nuclear Power Program's 1950s–60s technical objectives (modularization, reduced staffing, transportability, cost reduction) closely parallel the design priorities of today's SMR and microreactor developers.
- From deactivation in 1973 to site completion in 2026 represents a 53-year decommissioning tail — a critical data point for current SMR financial modeling.

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## Frequently Asked Questions

**What was SM-1 and where was it located?**
SM-1 was the first nuclear reactor deployed under the U.S. Army Nuclear Power Program, located at Fort Belvoir, Virginia. It entered operation in 1957 and was deactivated in 1973. It is recognized as the Army's first reactor and the first facility to provide nuclear-generated electricity to the commercial grid for a sustained period.

**When did SM-1 decommissioning begin and end?**
Planning for SM-1's final decommissioning began in 2014. Field activities commenced in 2021. The U.S. Army Corps of Engineers, Baltimore District announced completion of all field decommissioning activities in September 2026, with the overall decommissioning project having kicked off in 2020.

**Who was responsible for decommissioning SM-1?**
The U.S. Army Corps of Engineers, Baltimore District — home to the North Atlantic Division's Radiological Health Physics Regional Center of Expertise — led the decommissioning. Rebecca Yahiel served as project manager.

**Why did SM-1 decommissioning take so long after the reactor shut down?**
SM-1 was deactivated in 1973 and partially decommissioned in the 1970s, with fuel and control rods removed and the reactor pressure vessel sealed. Full decommissioning planning did not begin until 2014, with field work starting in 2021 — reflecting the regulatory, logistical, and funding complexity typical of nuclear end-of-life projects even when fuel has already been removed.

**What does the SM-1 closure mean for today's SMR developers?**
SM-1's approximately 53-year span from shutdown to site completion is a concrete data point for decommissioning liability modeling. It also demonstrates that the military's core requirements for nuclear — energy density, supply chain independence, modular deployment — have remained consistent since the 1950s, validating the market thesis behind current DoD-focused microreactor programs.