Investors Beware: 2 Nuclear Energy Stocks That May Be Radioactive to Your Portfolio

Nuclear power stocks went on a tear in 2025, with the Global X Uranium ETF (NYSEMKT: URA), for example, rising an incredible 72% year to date, crushing the return of the S&P 500.

Much of the credit for this performance goes to President Trump, who signed four executive orders in May promoting American nuclear power as a means of supplying artificial intelligence (AI) data centers with the electricity they need to operate. Of particular note was the president's encouragement of the development of small modular reactors (SMRs), which has helped spur market-beating returns among SMR nuclear startups, including Nano Nuclear Energy (NASDAQ: NNE) and Oklo (NYSE: OKLO).

Of the two, investors clearly favor Oklo stock, which is up more than 247% over the past 12 months, over Nano Nuclear -- which has gained only 15%. Yet once you dig into the numbers, a sneaking suspicion arises: Neither of these stocks may be able to keep their gains for long.

Image source: Getty Images.

Get to know Oklo

Let's start with the investor favorite, Oklo.

Oklo is designing what it calls a microreactor. This Aurora powerhouse will use High-Assay Low-Enriched Uranium (HALEU) fuel to produce anywhere from 1.5 to 75 megawatts of usable electrical power. The company will build Auroras in a factory and then transport them to their permanent site for installation.

As the company regularly reminds us, it's the first SMR to have received a "site use permit from the U.S. Department of Energy for a commercial advanced fission plant," and it was also the first to submit a "custom combined license application for an advanced reactor to the U.S. Nuclear Regulatory Commission." The company also aims to develop fuel recycling technologies to lessen U.S. reliance on foreign suppliers of uranium for the advanced nuclear plants that Oklo hopes to build.

The company has won multiple contracts from the Department of Energy, both to help develop its technology into working reactors and to build and operate three fuel fabrication plants.

Oklo's issues

Oklo expects its first reactor to go online and begin generating revenue in 2027, with the first GAAP profit to arrive in 2030, and a forecast for positive free cash flow in 2033. But here's where the problem arises.

Oklo has amassed more than $920 million in cash to fund its work and is currently burning less than $40 million a year. So far, so good? Yet the nearer Oklo gets to completion, the more money it's going to have to spend to set up fabs and actually build its reactors -- more than $580 million total over the next three years, and then close to $1 billion each year for the next four years, according to analyst estimates from S&P Global Market Intelligence.

At that rate, Oklo's going to run out of cash long before it turns free cash flow positive in 2033. It will need to either take on significant debt or sell substantial quantities of stock, diluting shareholders -- and perhaps both.

Suffice it to say that's not going to be good news for investors in the stock when it happens.

Nano Nuclear Energy

Nano Nuclear Energy's similar in many respects. Like Oklo, it's placing its nuclear bets in a scattershot manner, not focusing on just one aspect of the business -- building microreactors for data centers -- but also working to produce reactors for spacecraft, enrich and transport nuclear fuel, and provide "nuclear industry consulting services."

An optimist might look at all this activity and commend Nano for trying to diversify its revenue streams. A pessimist may look at the same activities and see "diworsification" instead.

The more so when you consider Nano Nuclear's financial situation. Like Oklo in having neither revenue nor profit today, Nano's similarly expected to begin generating revenue only in 2027 -- and profit not before 2033. Analysts aren't even making the effort to calculate operating cash flow, capital spending, or free cash flow for Nano Nuclear more than a couple of years out, perhaps because they're not convinced the company has the cash to go much further than that. (Nano has only about $200 million in the bank.)

Of the two, I suspect Nano's in the weakest financial shape, and likely to fold soonest. But to be perfectly blunt, I doubt either of these nuclear stocks will end up making money for investors in the long run.

Rich Smith has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.