Welcome to Nuclear Update, the newsletter that's so energized, we had to contain it in a pressure vessel.

This is what I’ve got for you this week:

• 🚀 The White House Putting Reactors in Space (With Actual Deadlines)

• 🇯🇵 Japan Turns the Key After 14 Years

• ⚛️ UK Signs Contract for Three SMRs at Wylfa

• 💰 X-energy Goes Public — Raising Up to $814M

• 🧪 The Dutch Are Building Europe's First Commercial Molten Salt Reactor

But first, this week’s trivia question:

Last week, I asked: 

What is the most abundant gas in Earth's atmosphere?

You said:

🟨🟨⬜️⬜️⬜️⬜️ Oxygen (8.4%)

🟨🟨🟨⬜️⬜️⬜️ Carbon Dioxide (13.3%)

🟩🟩🟩🟩🟩🟩 Nitrogen (77.8%)

🟨⬜️⬜️⬜️⬜️⬜️ Argon (0.5%)

Now, let’s dive into the good stuff! 💥

🚀 The White House Putting Nuclear Reactors in Space (With Actual Deadlines)

For 70 years, America has been trying to fly a reactor in space. Programs got funded, timelines slipped, budgets evaporated, and the hardware stayed on the ground.

The U.S. has reportedly spent more than $20 billion on space nuclear programs that never launched.

Last week, the White House decided to actually put some deadlines in place.

On April 14^th, the Office of Science and Technology Policy released National Science and Technology Memorandum 3, launching the National Initiative for American Space Nuclear Power.

Here is the directive:

• A minimum 20 kW fission reactor in orbit by 2028 (Space Reactor-1 Freedom)

• A variant on the lunar surface by 2030 (Lunar Reactor-1)

• High-power reactors (100 kW+) ready for the 2030s

NASA already has the first mission on the pad. Space Reactor-1 Freedom (minimum 20 kW fission reactor) targeting a December 2028 launch to Mars.

The payload includes three Ingenuity-class helicopters designed to scout for subsurface ice. Within 48 hours of leaving Earth's gravity, the reactor fires up and powers the thrusters.

The Lunar Surface Variant, called Lunar Reactor-1, is a power system designed for a permanent base at the Moon's south pole. It is part of NASA's plan to not just visit the Moon, but to live there.

By 2030, it needs to be set up at the lunar south pole to supply at least 20 kW of continuous power, during the 14-day lunar night, to support survival and operations.

The last directive, the High-Power Reactors, will see the government develop scalable reactor designs capable of exceeding 100 kW to support industrial-scale lunar mining and rapid crewed transport to Mars throughout the 2030s.

T. Folse Nuclear does a fantastic job explaining nuclear reactors on the moon.

So what makes this different from every previous announcement?

Hard launch dates.

The White House has put its name on a deadline. Now we wait to see if the hardware follows.

🇯🇵 Japan Turns the Key After 14 Years

On April 16, Tokyo Electric Power Company’s (TEPCO) Kashiwazaki-Kariwa Unit 6 officially resumed commercial operation. The first time a TEPCO reactor has generated power commercially since the Fukushima triple meltdown in March 2011.

The reactor is a 1,356 MWe Advanced Boiling Water Reactor in Niigata Prefecture. It’s the world’s largest nuclear power station.

Seven reactors and 8,212 MW total when fully operational.

Workers first attempted restart in January 2026. It was suspended hours later after a control rod alarm. It came back in February, went offline for inspections, was suspended again in March when a cracked conductor tripped an electricity leak alarm.

But on April 16 at 4:00 p.m., Japan's Nuclear Regulation Authority finally handed over the final certification. Commercial operation was confirmed.

Right now only Unit 6 is running. Unit 7 is next.

Units 1 through 5 are being evaluated for decommissioning.

Japan has now restarted a total of 15 reactors since Fukushima. Each one chips away at the country's dependence on expensive LNG imports. A dependency that has cost Japan an estimated $200 billion in extra fuel costs since 2011.

Amazing to see the world's biggest nuclear reactor finally waking up.

⚛️ UK Signs Contract for Three SMRs at Wylfa

On April 13, Rolls-Royce SMR and Great British Energy-Nuclear signed a formal contract to deliver three small modular reactors at Wylfa, on the island of Anglesey in North Wales.

The three-unit project delivers at least 1,400 MW. Each unit is a 470 MWe pressurized water reactor. These are modular and built in a factory before being transported on site.

The government has put $3.4 billion behind the contract. On top of that, the National Wealth Fund approved a loan of up to $810 million to complete the Generic Design Assessment (the regulatory sign-off), that once granted, covers every Rolls-Royce SMR built in Britain.

GBE-N has already pushed $473 million in supply chain contracts out to British industry this year.

Rolls-Royce has plans for 16 SMRs at sites across the UK and Wylfa will be the first.

The Generic Design Assessment wraps up by December 2026. After that, the design is approved for national deployment.

The site has capacity for up to eight units. Three are confirmed. The other five depend on future funding decisions.

For a country that spent years debating whether to build new nuclear at all, the future looks promising.

💰 X-energy Goes Public

On April 15, X-energy launched its IPO roadshow. 42.85 million shares at $16 to $19 per share. At the top of that range, the raise hits $814 million.

The underwriters are J.P. Morgan, Morgan Stanley, Jefferies, and Moelis & Company.

X-energy builds high-temperature gas-cooled reactors fueled by TRISO. These are uranium pellets in ceramic and carbon layers, cooled by helium.

Each uranium pellet is its own tiny containment vessel, meaning even if every cooling system fails and operators do everything wrong, the fuel physically cannot melt and release radiation.

Here’s how TRISO is made.

Their anchor customer is Amazon, which led a $500M funding round and has committed to buying up to 5 gigawatts of X-energy power by 2039.

Total capital X-energy has raised to date is $1.8 billion. Even on the low end of their IPO their total funding will greatly exceed $2 billion.

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🧪 The Dutch Are Building Europe's First Commercial Molten Salt Reactor

Molten salt reactors (MSR) have been "five years away" for about sixty years. The Dutch just made it considerably more real.

Unlike conventional reactors, which use solid fuel rods, an MSR dissolves its fuel directly into liquid salt, which acts as both fuel and coolant.

The result is a reactor that operates at low pressure, can run on nuclear waste as fuel, and shuts itself down passively if something goes wrong.

On April 16, eight organizations signed an Memorandum of Understanding to build Europe's first commercial MSR in the Netherlands.

Here’s the roadmap:

• 2027: Non-nuclear molten salt test facility operational

• 2030: Thorizon Pioneer nuclear demonstrator running at Petten

• 2034: Thorizon One, 100 MWe commercial MSR, on the European grid

The reactor runs partly on long-lived waste from existing nuclear plants, combined with thorium. The core uses replaceable cartridges swapped every five to ten years. A design that sidesteps one of the trickiest operational challenges of traditional MSR concepts.

2034 is eight years away. But this is the most concrete commitment to commercial MSR technology Europe has ever made.

Turns out the future of energy doesn't just run on uranium. Sometimes it runs on salt too.

💪Review of the Week

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