“Small modular reactor stocks” sounds like one clean category, but it is actually a bucket holding three very different kinds of companies. The names that get lumped together, NuScale Power, Oklo, and BWX Technologies, share a nuclear theme and almost nothing else in terms of risk profile, revenue timing, or what you are actually buying. Sorting them out is the fastest way to make sense of Karim Rahemtulla’s “Energy Cube” pitch, which sits just to the side of all three.
The pure-play developers
NuScale Power (SMR) is the closest thing to a pure-play small modular reactor company, to the point that its ticker symbol is literally the category. It designed a small modular reactor that won US Nuclear Regulatory Commission design approval, a genuine milestone, but its first commercial project was cancelled in 2023 when the projected cost came in far above what municipal customers were willing to pay. The stock is a concentrated bet on one reactor design reaching commercial scale, and the track record so far shows how hard that leap is.
Oklo (OKLO) is a different animal. It is an advanced nuclear company chasing smaller micro-reactors rather than the 470-megawatt class, and it went public through a merger in 2024. Its appeal is the long-shot of a much smaller, faster reactor design; its risk is that the revenue is almost entirely in the future and the technology has to clear the same regulatory and cost hurdles as everyone else.
BWX Technologies (BWXT) is the outlier that grounds the category. It is not a startup and not really a small modular reactor play. It is a long-established maker of naval nuclear reactors and components for the US Navy, plus a nuclear services and medical isotopes business. It earns revenue today, has real cash flow, and touches the nuclear story through the supply chain rather than through a single reactor bet.
Where the Rolls-Royce and Amentum sleeve fits
The “Energy Cube” pitch does not actually point at any of these three. It points at a sleeve built around Rolls-Royce SMR and its development partner Amentum, plus a set of uranium and services names. Rolls-Royce is a diversified aerospace, defense, and power company with a 470-megawatt small modular reactor arm bolted onto its existing businesses. Amentum is an engineering and government-contracting roll-up whose nuclear work is a meaningful slice of revenue, around 20% to 25%, but which also does data-center retrofits and cybersecurity. Neither is a pure-play SMR bet the way NuScale or Oklo is.
The practical difference is the balance between today and later. Rolls-Royce and BWXT earn most of their money now, from jet engines and naval reactors respectively, so their nuclear optionality is funded by existing cash flows. NuScale and Oklo are the reverse: almost all of their value sits in future revenue that depends on designs reaching commercial scale, which no Western small modular reactor has yet done.
The revenue-today versus revenue-later split
That split is the cleanest framework for reading the whole category. If you want nuclear exposure with near-term earnings attached, the diversified names and the contractors are the natural fit. If you want a concentrated bet on the small modular reactor thesis itself, the pure-plays are where that bet lives, with all the downside that concentration carries. The “portable reactor on a flatbed truck” image in the pitch oversells the timeline either way, because no cost-effective commercial small modular reactor is expected to operate at scale until the 2030s.
What the pure-plays still have to prove
The cleanest way to separate the category is to ask one question of each name: where does the revenue come from today? BWX Technologies answers with naval reactors and services, cash flowing now. Rolls-Royce answers with jet engines and power systems, cash flowing now. NuScale and Oklo answer with a future that has not arrived, which is why their share prices swing on every piece of reactor news rather than on earnings.
That swing is the tell. A company that already earns money gets valued on the earnings it can show. A company that earns nothing yet gets valued on a story, and stories reprice fast in both directions. The small modular reactor thesis is a legitimate industrial story, and Rolls-Royce is one of the real leaders in it. But the honest distinction the pitch blurs is between owning a diversified company that happens to have a reactor division and owning a startup whose entire existence is the reactor. They carry different risks, and no amount of “Energy Cube” branding makes them the same trade.
For a deeper look at the reactor builders as a group, see our small modular reactor stocks rundown. For the whole field, including the utilities and fuel names, we map the nuclear energy stocks in play. And for why the data-center power crunch is what ties this category to the AI buildout, read our data center power demand explainer.
Ready to see the research? Click here to access Karim Rahemtulla’s report.
NewsletterVetter is an independent publication. We receive compensation from some of the services we review through affiliate links. Nothing on this site is investment advice. Always do your own research.