Prof. Prabhat Ranjan CEO and Co-founder of a nuclear fusion company called ASPL Fusion. He is former Vice Chancellor of D Y Patil International University, Akurdi, Pune
On 19 June 2026 Realta Fusion drew real current straight from a fusion plasma, no turbine involved. Prof. Prabhat Ranjan on direct energy conversion versus the steam turbine — what it changes for deuterium–tritium, why it is a magnetic-mirror story, and where it points for advanced, low-neutron fuels.
On 19 June 2026, Realta Fusion, working with the University of Wisconsin–Madison, drew a few amperes of current at around a hundred volts from charged particles streaming out of the ends of their WHAM mirror device — enough, in their own words, to light a few bulbs. It is worth pausing on how modest that sounds, and how significant it actually is.
This was the first time a private fusion company has converted the kinetic energy of a fusion-relevant plasma directly into electricity, without first turning it into heat. The team has been careful to say what it is not: it is neither net-electric production nor large-scale conversion of fusion-born power. That restraint is exactly why the result deserves attention. A real current in a real circuit is a physical fact, not a press release.
I want to use the occasion to discuss something the fusion community does not talk about often enough — the rather nineteenth-century machine sitting at the heart of almost every twenty-first-century power plant we propose to build.
In June 2026 the US Department of Energy published a fusion roadmap that quietly hands the lead to its private sector. Prof. Ranjan draws the real lessons for India — the public-to-private shift, the partnership mechanisms worth copying, the lanes where India can genuinely lead, and the case for a roadmap of our own.
In June 2026, the United States Department of Energy published its Fusion Science and Technology Roadmap. It is, on the surface, a domestic planning document — a list of facilities, milestones, and gaps that one nation intends to close over the next decade. But read carefully, it is something more interesting: the clearest articulation yet of how a great scientific power intends to hand the lead in an emerging energy technology to its private sector, while keeping its public institutions firmly in the game.
For those of us trying to build a credible private fusion enterprise on Indian soil, this document repays close study. Not because we should copy it — our circumstances are different — but because it surfaces, in plain language, the choices every nation now faces. I want to set down what I take to be the real lessons for India, and where I think our own path must diverge.
The strategic shift hidden in three words
The Roadmap organises everything around three verbs: Build, Innovate, Grow. Underneath the alliteration sits a genuine change of posture. For seventy years, the American public programme — like every national fusion programme, including our own — assumed that the state would design and construct the first power plant. The 2021 National Academies report said as much.
The DOE strategy in one line: the state builds shared capability so that companies can build reactors.
The new Roadmap quietly retires that assumption. It now treats the private sector as the builder of first-of-a-kind machines, with the public programme repositioned to do something narrower and arguably more valuable: close the common scientific and technical gaps that no single company can justify paying for on its own. To make this concrete, DOE created a stand-alone Office of Fusion in late 2025 and restructured its science programme around it.
This is the lesson India should absorb first. The question is no longer “when will the Department of Atomic Energy build a fusion reactor?” It is “what must our public institutions build so that Indian companies can build reactors?” That is a different — and in my view, far more answerable — question.
Public money belongs where private money cannot go
The most useful part of the American document is its honesty about where public investment is decisive. It identifies six challenge areas — structural materials, plasma-facing components, confinement, the fuel cycle, breeder blankets, and whole-plant engineering — and is candid that several of these are bounded by physics and metallurgy, not by money. Materials qualification under fusion neutrons, and closing the tritium fuel cycle, take wall-clock time that capital cannot compress. No amount of venture funding shortens an irradiation campaign.
The American answer is to pool these burdens. Shared neutron sources, blanket and tritium test platforms, and a network of test stands are to be funded publicly and made accessible to all developers, because the cost of duplicating them is ruinous and the knowledge they generate is largely non-proprietary.
India already has the raw ingredients for exactly this model — and, in some respects, a head start. The Institute for Plasma Research, BARC’s irradiation and tritium-handling facilities, and our materials laboratories are national assets that took decades to build. The strategic act now is to deliberately open a defined slice of that capability to qualified private players, with clear rules of access. This is precisely the logic behind incubating a private company within IPR’s ecosystem — a path our own work is pursuing, and which I believe should become routine rather than exceptional. The American roadmap gives that instinct an external endorsement.
Learn the mechanisms, not just the intent
Good intentions about public–private partnership are common; workable instruments are rare. Here the Americans have done the hard design work, and we should study their toolkit rather than reinvent it.
Four instruments, four bargains — the same rupee deployed against four different kinds of risk.
They run four distinct instruments side by side, each with a different bargain. The Milestone Program pays private companies only for achieving defined technical and business milestones — a model borrowed deliberately from NASA’s commercial cargo programme. INFUSE issues small vouchers that buy private companies access to national-laboratory expertise. The FIRE Collaboratives fund universities and laboratories to close specific gaps that industry has flagged. A newer instrument, Fusion BRIDGE, co-finances the construction of shared facilities with state governments, philanthropy, and industry together.
India does not lack funding vehicles — between the Anusandhan National Research Foundation, the Technology Development Board, and the architecture now being enabled by recent legislation, the pieces exist. What we lack is the discipline of differentiated instruments matched to differentiated risks: one for milestone-based capital, one for expertise access, one for shared infrastructure. The American experience suggests this differentiation is not bureaucratic neatness; it is what allows the same rupee to be used four different ways for four different problems.
At INEF 2026 I realised how little the fission and fusion communities still talk to each other. Yet a fusion device is, before it is ever a power plant, an intense source of fast neutrons — and that surplus can breed U-233 from India’s thorium, burn long-lived waste, and drive a sub-critical hybrid that never goes critical. Fission problems with a fusion answer.
The Neutron Bridge — Part 1 | Prof. Prabhat Ranjan
I spent two days at the India Nuclear Energy Forum at IIT Bombay this May, and I came away with one impression more strongly than any other. The people who build and run our fission plants — some of the most capable nuclear engineers anywhere — have, for entirely understandable reasons, not been watching what has happened in fusion over the last five or six years. And the fusion community, equally guilty, has rarely bothered to explain itself in terms a reactor physicist would find useful.
That is a shame, because the two fields are closer to needing each other than either side seems to realise. I want to use this note to close a little of that gap, written deliberately for colleagues who think in cross-sections and neutron budgets rather than press releases.
What changed in fusion while you were busy keeping the grid running
For most of our careers, “fusion” meant one thing: a very large tokamak, decades away, funded by governments. ITER is real and important, but it shaped a perception that fusion is monolithic and remote. That perception is now out of date in two specific ways.
First, the magnet problem has largely been solved by materials, not by scale. High-temperature superconductors — REBCO tapes in particular — let us reach the field strengths that used to require enormous low-temperature magnets, in machines a fraction of the size. A high field at a small radius changes the entire economic argument, because confinement and reaction rate scale steeply with field. This is why the credible new private programmes are an order of magnitude smaller than ITER and still expect meaningful performance.
Second, and more relevant to this audience, the field has rediscovered configurations the fission community would find refreshingly simple. I work on the axisymmetric magnetic mirror — the Gas Dynamic Trap lineage from Budker Institute in Novosibirsk, recently validated by the WHAM experiment at Wisconsin and its commercial successor. A linear mirror is not a closed toroidal device. It is, conceptually, a long straight magnetic bottle. It is easier to build, easier to maintain, and — crucially — it is an excellent neutron source even when its energy gain is modest. Hold that last point; it is the whole argument.
The deeper shift is one of intent. A generation of fusion programmes asked only one question: when do we put electricity on the grid? The newer programmes ask a different one first: what is fusion good for before it is a power plant? And the honest answer is that a fusion device is, first and foremost, a controllable, intense source of fast neutrons. That reframing is what should interest you.
Why a fusion neutron is different
A deuterium–tritium reaction releases 17.6 MeV, of which 14.1 MeV leaves as a neutron. Compare that with the roughly 2 MeV average of a fission neutron. The factor of seven in energy is not a curiosity — it opens reaction channels that are simply closed to a thermal or even a fast fission spectrum.
The fusion neutron is born about seven times more energetic than a fission neutron, clearing the thresholds for neutron multiplication and hard-spectrum fission that a reactor spectrum cannot.
At 14 MeV you get neutron multiplication almost for free. Inelastic and (n,2n) channels in beryllium and lead mean a blanket can return more neutrons than it receives. That surplus is the resource. In a critical reactor every neutron is spoken for — you live or die by the six-factor formula and you have almost no margin to spend neutrons on anything that does not sustain the chain. A fusion source hands you a neutron budget you do not have to balance against criticality.
What you choose to do with that surplus — breed fuel that has eluded our thorium programme for decades, burn the waste that fills our repositories, and generate power without the assembly ever going critical — is exactly where our two fields meet.
