I didn’t expect to walk into a room full of teenagers debating neutron economy and thorium cycles, but that’s exactly what happened. Even months later, the energy from that event stays with me. Students from Tokyo and Osaka came together with a seriousness that felt different from typical science outreach. They weren’t memorizing answers; they were trying to understand where Japan stands in a world where nuclear technology is rapidly evolving. Watching them made me realize that the next generation isn’t afraid of nuclear; they’re ready to take responsibility for it.
The first speaker opened with something small but surprisingly powerful: a fusion demonstration device that lights up and vibrates when two parts meet. Kyoto Fusioneering uses it to teach the basics of fusion, and it became a minor sensation after Princess Aiko tried it. Seeing the students gather around it reminded me how a simple hands-on moment can make even the most advanced technology feel human and accessible.
From there, the speaker took us into Kyoto Fusioneering’s world, a startup founded in 2019 that has grown to around 160 employees, secured about twenty-one billion yen in financing, and reached a valuation of roughly seventy billion yen. Instead of competing to build the first fusion power plant, they focus on building the hardware every reactor will need. Their approach fits Japan’s strengths: precision engineering and high-end manufacturing.
One example is their gyrotron, a microwave source used to heat plasma. Each one costs hundreds of millions of yen, and they’re already exporting them to partners in the U.K., U.S., and South Korea. They’ve also built liquid-metal test loops that recreate fusion-level heat flows. Their Tokyo office focuses on fuel-cycle research, while in Kyoto, UNITY-1 is taking shape as a mock power loop to demonstrate electricity generation under fusion conditions. Alongside UNITY-1, two programs AT-1 for heat extraction and MT-2 for fuel handling are building toward an integrated facility called FAST, intended to be complete around 2035. The goal is to push fusion forward step by step, working toward realistic electricity generation around 2040.
What struck me most was how the speaker framed this moment. He said breakthroughs rarely happen through dramatic, once-in-a-century events. Instead, they come when a small demonstration finally proves something that was doubted for years. You could see the students absorbing that idea. It made fusion feel achievable, not abstract.
The tone shifted when the next speaker began talking about molten-salt reactors. If fusion is the long-term goal, molten-salt fission feels like a near-term opportunity. The core difference still surprises people: in an MSR, the fuel is liquid. That one fact changes how the reactor behaves. With molten fuel instead of solid rods, the system can operate near a thousand degrees Celsius, producing highly efficient electricity and industrial heat. It also avoids the high-pressure environment of today’s reactors.
The speaker described the Oak Ridge experiments from the 1960s, where the molten fuel could drain by gravity into a cooled tank in emergencies. The chain reaction stopped on its own, not because of clever phrasing, but because the physics demanded it. Of course, modern MSRs still require robust drain valves, passive cooling, and materials that can handle high temperatures, but hearing this helped students rethink what nuclear safety can mean.
He also addressed waste. Some MSR designs can burn transuranics, the long-lived elements that drive today’s waste storage challenges. It’s not a perfect answer, but it changes the conversation from “waste is fixed” to “waste can be engineered.”
Globally, molten-salt work is accelerating. China built a facility in the desert near Wuwei after major development in Shanghai, though public information has tightened. In North America, research groups are exploring both land-based and floating MSR designs, while projects in Texas aim for commercial builds. Japan remains cautious, preferring technologies fully demonstrated under modern safety rules. The speaker suggested that with stepwise testing, Japan could reenter the field.
The third session broadened the picture even more, starting with thorium systems and Germany’s pebble-bed reactor work from the 1980s, which used TRISO fuel spheres, tiny, incredibly durable balls containing thorium and uranium oxides. That program ended, but China revived it. Hearing this history made it clear how nuclear innovation often stops not because of failed science, but because priorities shift.
From thorium, the speaker moved back to fusion and explained something most people never think about: neutrons. In fusion, fast neutrons fly out in all directions. Some are useful, like those hitting lithium blankets to make tritium. But many damage the reactor itself. He pointed to ITER in France to show how much of fusion engineering involves managing these neutrons controlling how they hit structures, how they activate materials, and how they influence the reactor’s geometry.
Then came one of the most surprising technologies of the entire event: an accelerator-driven system small enough to fit in a standard forty-foot shipping container. In an ADS, a particle accelerator drives a subcritical core. If you turn off the accelerator, the reaction stops immediately. The nuclear module sits underground, with the accelerator above, and the system uses liquid sodium and molten salt to move heat. They’re building pumps and heat exchangers capable of withstanding temperatures up to around nine hundred degrees Celsius.
Despite its size, the ADS can produce around twenty-five megawatts of thermal power, running steadily while a molten-salt storage tank smooths out fluctuations. It’s designed for remote islands, industrial heat, district heating, and hydrogen production. The main engineering challenge is the accelerator, which must be powerful yet compact. The team is even exploring wakefield acceleration to shrink it further. The program began serious lab work in late 2023 and already has around fifty core staff and more than a hundred people including partners. Their aim is to demonstrate net nuclear power Q>1 around 2029. They’re also developing medical neutron sources and molten-salt thermal storage, but they’re realistic about regulation being the biggest hurdle. Licensing a reactor, no matter how small, requires meeting strict safety cases, which is why they’re engaging with groups in Japan, Malaysia, Sydney, Abu Dhabi, and the U.S. to map out approval paths.
The final session focused on international cooperation. The speaker described molten-salt reactors as cousins of today’s light-water reactors, just with molten salt replacing water. He explained how shrinking reactors creates neutron-economy challenges due to geometry, often requiring enrichment near twenty percent. Fuel availability is becoming a design constraint now that Russian enrichment shipments to the U.S. have declined.
When he turned to fusion culture, the atmosphere shifted again. For decades, fusion was one of the most open scientific fields. ITER itself was built as a symbol of cooperation. But in the past five years, fusion has become strategically sensitive. The U.S. now treats it as a national-security technology. China is building major, largely non-public fusion facilities expected to achieve deuterium-tritium burning within about five years. Cybersecurity has become a central concern across fusion labs worldwide.
Even with this competitive atmosphere, he argued that cooperation is still essential, just in a different shape. Instead of fully open global collaboration, he advocated “friend-shoring,” where trusted countries share supply chains and expertise while protecting critical knowledge. He also reminded us that many leading Chinese fusion researchers trained in Japan, showing that personal connections continue to matter even when politics shift.
By the end of the event, the theme tying everything together was clear. The future of nuclear, fusion, molten-salt fission, thorium systems, ADS micro-plants will be shaped by careful engineering, international relationships, and a younger generation willing to learn the details rather than rely on slogans. Watching the students debate these ideas reminded me that Japan’s nuclear future isn’t only a technical matter. It’s a cultural moment. As Japan reconsiders its energy mix after the Fukushima accident, these young voices will matter more than ever.
They are the ones who will carry the story forward.