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Regulating Fusion for What It Is

The SHANTI Act ended a six-decade monopoly and opened India’s nuclear sector to private enterprise — but its framework was written for fission. Drawing on how the United States, the United Kingdom and Japan now regulate fusion for its actual hazard, here is what India should change next, and where the lighter touch must not apply.

When the SHANTI Act took effect in December 2025, it ended a monopoly that had defined Indian nuclear policy since 1962. For the first time, an Indian private company can hold a licence to build and operate facilities that involve nuclear materials and ionising radiation, under the oversight of a regulator — the Atomic Energy Regulatory Board — that the same Act finally placed on a statutory footing. This is a structural reset, and it deserves the praise it has received.

But a law written principally for fission power generation cannot, on its own, settle how fusion should be governed. That is the next question, and it is a narrower and more technical one than the debate that produced SHANTI. It is also one the rest of the world has spent the last three years answering. India now has the rare advantage of being able to learn from settled precedent rather than improvise.

The argument begins with the physics

Those of us who have spent careers operating India’s experimental tokamaks know that a fusion device and a fission reactor are not variants of the same hazard. A fission reactor sustains a chain reaction in a large inventory of fissile material; its central safety problems are criticality control, the management of decay heat after shutdown, and a very large radioactive source term that must be contained in any conceivable accident. None of these apply to a magnetic-confinement fusion machine. There is no chain reaction to run away. The fuel present in the plasma at any instant is measured in fractions of a gram, and any disturbance — a loss of heating, a loss of vacuum, a magnet trip — causes the reaction to stop within seconds. The plasma cannot melt down because there is nothing sustaining it once conditions are lost.

This does not make fusion free of radiological concern, and no serious person claims it does. There are two real hazards, and they are bounded and well understood: the handling of tritium, a low-energy beta emitter used as fuel; and the neutron activation of the structure surrounding the plasma, which produces radioactive materials in the machine’s own components. These are radiation-safety problems. They are the kind of problem a regulator manages every day for medical accelerators, industrial radiography, and radioisotope production. They are not reactor-safety problems, and a regime designed for reactor safety is the wrong instrument for them.

Comparison of nuclear fission and magnetic-confinement fusion hazard profiles — Fission and fusion present fundamentally different safety problems.

Real hazards, of a different kind

To say that fusion is not a reactor is not to say it is benign. A fusion device is a large and demanding industrial plant, and several of its hazards are serious — they are simply the hazards that an occupational- and industrial-safety regime exists to manage, not nuclear-accident hazards. Its superconducting magnets store very large amounts of magnetic energy, and an unplanned quench — a sudden loss of superconductivity — must be engineered against so that the energy is released safely. Those magnets are held near absolute zero by substantial inventories of liquid helium and nitrogen, which in an enclosed space are asphyxiation hazards before they are anything else. The plasma heating and current-drive systems operate at extreme high voltages. None of this is unfamiliar to a competent regulator, but all of it is dangerous if managed poorly.

There is a materials hazard as well, and it is chemical rather than radiological. Many magnetic-confinement designs face the plasma with beryllium or tungsten, and the intense plasma–surface interaction generates fine dust inside the vacuum vessel. Beryllium dust is highly toxic: inhaled during maintenance, it can cause berylliosis, a chronic and irreversible lung disease. Controlling it — containment, ventilation, respiratory protection and disciplined access during maintenance — is an industrial-hygiene problem in its own right, entirely separate from radiation protection.

This is precisely why regulating fusion “for what it is” is not the same as regulating it lightly. What it calls for is the right combination: radiation safety for tritium and activated material, conventional industrial and occupational safety for the magnets, cryogenics and high-voltage plant, and hazardous-materials controls for beryllium and tungsten dust. The United Kingdom’s decision to place fusion under the Health and Safety Executive and the environmental regulators is, seen in this light, a choice to govern it through the industrial-safety system — not a choice to go easy on it. For India, the practical implication is that a workable regime must align AERB’s radiation oversight with the country’s conventional industrial-safety authorities, so that an operator meets one coherent set of expectations rather than a fragmented patchwork. The error the world’s leading jurisdictions have now moved to correct is the narrower one: applying the rulebook written for a reactor’s nuclear-accident hazards to a machine that has none of them.

What the rest of the world decided

The pattern across countries is strikingly consistent, and it amounts to a single principle: regulate fusion in proportion to the hazard it actually presents, which is the hazard of radioactive materials, and keep it legally distinct from fission.

In the United States, the Nuclear Regulatory Commission decided in 2023 to regulate fusion machines not as power reactors but under its byproduct-material framework — the same regime that governs radioisotopes and particle accelerators. The reasoning was explicit: fusion does not generate the decay heat that requires engineered emergency cooling, so the regulatory focus should sit on tritium, activation products, and activated dust, which existing materials licensing already handles well. Congress wrote that choice into law in the 2024 ADVANCE Act, and the NRC issued its proposed rule in February 2026. The resulting framework is described, in the agency’s own terms, as performance-based, technology-inclusive and risk-informed — deliberately less prescriptive than the rules for fission plants.

The United Kingdom went further in statute. Its Energy Act 2023 confirmed that fusion energy facilities fall outside the Nuclear Installations Act 1965, so they do not require a nuclear site licence and are not overseen by the Office for Nuclear Regulation. Instead they are regulated by the Health and Safety Executive and the environmental regulators, under rules judged proportionate to fusion’s lower hazard. The government’s stated motive was as much economic as scientific: early regulatory clarity, it found, was a decisive factor in where private fusion companies chose to locate.

Japan is moving the same way, with its expert bodies recommending that fusion be regulated under the radioisotope law rather than the law governing fission reactors, expressly to avoid over-regulation. China oversees fusion devices through its radiation-protection and radioisotope-device regulations rather than its reactor regime. Four very different systems, four different legal mechanisms, one shared conclusion.

How the United States, United Kingdom, Japan and China each regulate fusion energy — Four very different legal systems have reached the same conclusion.

What none of these countries did is lower their safety standards. They removed a category error. A technology whose dominant risk is contained radioactive material should be regulated as such — rigorously, but not under a rulebook written for runaway chain reactions and molten cores.

What India should do next

India does not need to repeat this debate from first principles. It needs to make a small number of specific, well-precedented choices within the framework SHANTI has already given it.

First, define fusion machines and accelerator-based neutron sources distinctly in AERB’s subordinate regulations, and place them on the radiation-safety licensing track rather than the power-reactor track. AERB already operates a mature apparatus for licensing medical accelerators, industrial sources and isotope facilities. The earliest commercial fusion-adjacent devices in India — accelerator-driven neutron sources for medical and industrial use — belong on that track by their physics. The Board should say so explicitly, so that applicants are not left guessing which regime applies.

Second, adopt a graded, risk-informed pathway that scales requirements to the device. A research-scale machine, a demonstration plant, and an eventual power plant present escalating but still bounded hazards. The licensing burden should escalate with them rather than being fixed at the level appropriate to a gigawatt fission station. This is the performance-based logic the United States has now codified, and it is the right fit for a sector that will move through several device generations.

Third, provide predictability. Investors fund certainty at least as much as they fund physics. Published licensing pathways, structured pre-application engagement with AERB, and defined timelines for review do more to enable a private sector than any subsidy. The UK experience is unambiguous on this point: clarity itself was the incentive.

Fourth, make liability proportionate. SHANTI already replaced a single statutory cap with a graded liability framework linked to plant capacity, and it gives the Central Government power to relieve facilities of liability obligations where the risk is judged insignificant. Fusion’s small source term is exactly the case that provision was written for. A fusion liability tier set well below that of a fission station would reflect the real risk and remove a needless barrier to insurance and finance.

Fifth, align with the emerging international consensus. As AERB develops fusion-specific guidance, it should draw on the IAEA’s work and on the converging US, UK and Japanese frameworks, so that a design licensed in India can be recognised abroad and Indian regulators can benefit from the operating experience accumulating elsewhere. For a country that hopes to export this technology, harmonisation is not a courtesy — it is market access.

A graded, proportionate fusion licensing pathway for India, with fusion-fission hybrids held to the full nuclear regime — A graded track for fusion — and a deliberate carve-out for the hybrid.

The honest boundary: where the lighter touch must not apply

A credible case for proportionate regulation has to be equally clear about where proportion runs the other way. Not everything that travels under the banner of “fusion” carries fusion’s benign hazard profile.

The clearest example is the fusion–fission hybrid: a device that surrounds a fusion neutron source with a sub-critical fission blanket. Whatever its merits as a route to early net power, such a machine holds bulk fissionable material and breeds fission products. Its hazards are genuinely fission-grade, and it should be regulated as such. The United Kingdom recognised this and deliberately kept hybrids inside its nuclear site licensing regime even as it freed pure fusion from it. India should do the same. SHANTI already reserves the most sensitive parts of the fuel cycle — enrichment, reprocessing, heavy-water production and the management of spent fuel beyond on-site storage — to the Central Government. Any hybrid programme therefore belongs inside the national framework operated by the Department of Atomic Energy and its institutions, in partnership with them, not as a freelance enterprise around them.

This is not a concession reluctantly made. It is the discipline that makes the rest of the argument credible. A sector that asks for proportionate treatment of its low-hazard activities must visibly accept full treatment of its high-hazard ones. That is how a regulator, and a public, come to trust a new industry.

A proportionate, not a permissive, ask

None of this is a request to regulate fusion lightly. It is a request to regulate it accurately. The countries that have separated fusion from fission did not weaken their safety standards; they matched the standard to the science and removed a mismatch that would otherwise have strangled a low-hazard technology under rules built for a high-hazard one.

India has just taken the hardest step. Repealing a six-decade monopoly and giving its nuclear regulator statutory independence was the difficult, structural reform. What remains for fusion is smaller, more technical, and extensively precedented: a clear definition, a proportionate licensing track, predictable timelines, fair liability, and an honest line drawn at the hybrid. Get these right, and India can grow a private fusion sector that does not compete with the national programme that DAE, BARC and IPR have built since the 1950s, but complements it — adding a commercial route, on Indian soil, to capabilities the country has spent two generations learning to master.

Building on What We Have: How India’s Atomic Energy Establishment Can Launch a Private Fusion Industry

In his previous blog, Prof. Ranjan argued that America’s new fusion roadmap marks a change of posture — the state stepping back from building the first power plant and instead building the shared infrastructure that lets private companies build it. Here he asks the natural follow-up for India: not what our public institutions should build, but what they should open. A surprising share of what a private fusion industry needs already sits inside the Department of Atomic Energy.

Building on What We Have — Prof. Prabhat Ranjan

A companion essay. This piece continues an argument begun in “Build, Innovate, Grow: What America’s New Fusion Roadmap Means for India.”

In my last essay I argued that the deepest lesson of America’s new fusion roadmap is a change of posture — the state stepping back from building the first power plant, and instead building the shared infrastructure that lets private companies build it. That argument invites an obvious question for India: if our public institutions are to enable a private fusion industry, what exactly should they build?

After some months of looking closely, I think the more urgent question is what they should open. A great deal of what India needs already exists, scattered across the units of the Department of Atomic Energy. The fastest and cheapest way to accelerate fusion here is not a greenfield campaign of new institutes; it is to upgrade, repurpose, and — above all — open a defined slice of the capability the DAE has spent six decades building.

I do not write this from the outside. I carried out my own doctoral fusion research at Berkeley; spent nine years as a scientist at the Saha Institute of Nuclear Physics, where I worked on India’s first tokamak, commissioned in 1987; and later led the ADITYA tokamak at the Institute for Plasma Research, along with the operation and control group of its SST-1 superconducting tokamak. Several of the units I describe below I have worked inside, and I have watched this establishment’s plasma capability grow from a single small tokamak into a national programme. What follows is, in part, an argument that India underestimates what it already owns.

A platform, not a building

The American roadmap calls its shared infrastructure the Tritium-Blanket Development Platform — a distributed network of test stands and loops, public and private, that any developer can draw on because no single company can justify building them alone. India can assemble an equivalent almost entirely from assets it already holds. The right unit of thinking is not a new national laboratory but a platform — a coordinated set of shared user facilities, each anchored in an existing DAE unit and opened, under clear rules, to vetted private developers. Let me walk through fusion’s hardest gaps and where, in the DAE, each could be addressed.

Build, Innovate, Grow: What America’s New Fusion Roadmap Means for India

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.

The Neutron Bridge

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.

Energy comparison of a fission neutron at about 2 MeV and a D–T fusion neutron at 14.1 MeV, showing the high-energy reaction channels — (n,2n) multiplication and fast fission of minor actinides — that only the fusion neutron reaches. — 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.

Unlocking India’s Thorium Age : How ASPL Fusion Can Accelerate India’s Three-Stage Nuclear Programme

On 6 April 2026, India’s PFBR at Kalpakkam achieved first criticality — entering Stage 2 of the three-stage nuclear programme. But Stage 3, the thorium endgame, remains 45–65 years away. The bottleneck is ²³³U, which must be bred from thorium and currently depends entirely on the slow FBR build-out. Fusion-fission hybrid technology offers a parallel route: fusion neutrons driving a subcritical thorium blanket, independently of the FBR fleet, potentially compressing the wait by 20–30 years.

📣 Breaking — 6 April 2026 India’s Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu achieved first criticality at 20:25 IST — marking India’s formal entry into Stage 2 of the three-stage nuclear programme. This historic milestone, coming just as this article goes to press, makes the question of accelerating Stage 3 more urgent and more actionable than ever. ASPL Fusion’s Project PRABHA is designed to be exactly that accelerant.

India sits atop the world’s largest thorium reserves — enough to power the country for centuries. Yet the gateway to this abundance, Stage 3 of the three-stage nuclear programme, remains decades away under the current trajectory. ASPL Fusion’s fusion-fission hybrid technology offers a credible, privately-funded shortcut: producing ²³³U directly from thorium using fusion neutrons, bypassing the central bottleneck of the Fast Breeder Reactor fleet, and potentially compressing a 40-year wait into 20.

1. India’s Three-Stage Vision: Brilliant Design, Slow Execution

When Dr. Homi Bhabha conceived India’s three-stage nuclear programme in the 1950s, it was a work of strategic genius. India had almost no uranium but enormous thorium deposits — estimated at ~25% of the world’s total reserves. The plan was to harness fission step by step, each stage feeding the next, culminating in a self-sustaining thorium-uranium fuel cycle that could power India essentially forever.

Stage	Reactor Type	Fuel In / Out	Strategic Purpose
Stage 1	PHWRs (Pressurised Heavy Water)	Natural U-238 → Pu-239	Exploit domestic uranium; breed plutonium
Stage 2	Fast Breeder Reactors (FBRs)	Pu-239 + Th-232 → ²³³U	Multiply fissile inventory; introduce thorium
Stage 3	Advanced Heavy Water Reactors (AHWRs)	²³³U + Th-232 → Power	Exploit vast thorium reserves at scale

The logic is elegant. The execution has been painfully slow. Stage 1 is mature — 22 PHWRs now operate across India. Stage 2 is inching forward: the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam achieved first criticality on 6 April 2026 after decades of delays. Stage 3, the thorium endgame, remains a distant prospect. At current rates, meaningful Stage 3 deployment may not arrive until 2070–2090 — over half a century away.

The central bottleneck is fissile material inventory. Stage 3 reactors require an initial loading of ²³³U — a material that does not occur in nature. It must be bred from thorium by bombarding it with neutrons. Under the classical pathway, the only source of those neutrons at scale is the FBR fleet. But FBRs take decades to build, and their early fuel is precious Pu-239 from Stage 1 — itself in limited supply. It is a slow compound-interest problem, and India is impatient.

2. The Missing Accelerant: An External Neutron Source

To understand the bottleneck, it helps to understand the breeding reaction itself. When a thorium-232 nucleus absorbs a neutron, it does not immediately fission. Instead, it undergoes a two-step transmutation: first to protactinium-233, then to uranium-233 — a fissile material that can sustain a chain reaction just as uranium-235 or plutonium-239 can. This is the nuclear alchemy at the heart of Stage 3. The challenge is neutrons: you need a sustained, high-intensity neutron flux to irradiate thorium at scale, in sufficient quantity to produce meaningful amounts of ²³³U. Classically, only a working fission reactor can supply that flux — which is why Stage 3 has always depended on Stage 2 FBRs. But what if India could breed ²³³U without waiting for the FBR fleet? What if a neutron source powerful enough to drive a thorium blanket could be built faster, cheaper, and with private capital?

This is precisely the proposition at the heart of fusion-fission hybrid technology — and it is the core strategic value of ASPL Fusion’s Project PRABHA.

What is a fusion-fission hybrid?

A fusion-fission hybrid marries two nuclear processes. Fusion — the joining of light nuclei (deuterium and tritium, or deuterium alone) — releases vast energy and, crucially, a flood of energetic neutrons. Fission — the splitting of heavy nuclei like thorium or uranium when struck by neutrons — releases further energy and breeds new fissile material. In a conventional fission reactor, a precise critical mass of fissile fuel must be maintained to keep the chain reaction going, demanding expensive enrichment and creating inherent safety challenges.

In a fusion-fission hybrid, the fusion core acts as a powerful, controllable neutron gun, firing neutrons into a surrounding “blanket” of thorium. The blanket undergoes breeding reactions, but it never reaches criticality on its own: its neutron multiplication factor k_eff is kept below 1.0 by design. This means the reaction halts the instant the fusion source is switched off — an intrinsic safety property no conventional reactor can match, since no self-sustained runaway chain reaction is physically possible. However, subcritical systems still accumulate decay heat from fission products after shutdown, requiring continued cooling; they are not free from thermal-hydraulic safety requirements. Yet the neutron economy within the blanket can be made substantial. The neutron multiplication factor M = 1/(1−k_eff) = 33 means that one source neutron ultimately produces approximately 33 neutrons across all cascade generations — not 33 breeding reactions. Of these, a fraction (typically 10–30%, depending on blanket design and spectrum) are usefully absorbed in Th-232 to initiate the transmutation chain to ²³³U. The remainder sustain the multiplication, compensate for parasitic absorption in structural materials, and manage leakage. This neutron amplification, combined with a carefully optimised multi-zone blanket, is what enables meaningful ²³³U production from a modest fusion source.

ASPL Fusion’s PRABHA-Hybrid is a subcritical fusion-fission hybrid with the following design parameters:

k_eff = 0.97 — deeply subcritical, inherently safe
Neutron multiplication M = 33× — one source neutron produces ~33 neutrons in cascade across all generations (M = 1/(1−k_eff)); a fraction of these are usefully absorbed in Th-232 for ²³³U breeding
Thorium breeding zone: TBR ≥ 1.05 — tritium self-sufficient
~80 kg of ²³³U per unit per year from the thorium zone — a design-target based on internal neutronics calculations at ~53 MWth blanket power; subject to detailed validation accounting for Pa-233 capture losses, spectrum effects, and geometric efficiency
33 MWe net electrical output at 87.5% capacity factor (253 GWh/yr)

The neutron source is a Gas Dynamic Trap (GDT) driven system, with possible collaboration with BINP Novosibirsk — the world leader in tandem mirror devices. This is not speculative physics; GDT devices have operated for decades. ASPL is the first Indian private company to access this technology for a commercial fusion application.

Viksit Bharat Needs Firm Power: Why Fusion Must Be in India’s Energy Plan Now

India’s electricity demand will nearly quadruple by 2047. Solar and wind cannot carry that load alone. The time to build the next generation of baseload is not 2040 — it is today and why fusion must be a strong part of it.

India’s electricity demand will nearly quadruple by 2047. Solar and wind cannot carry that load alone. The time to build the next generation of baseload is not 2040 — it is today.

Disclosure: The author is co-founder of ASPL Fusion, a private Indian fusion company. This article presents an industry perspective on national energy policy. The policy arguments are grounded in publicly available data; the ASPL programme description in Section 5 is provided as a concrete illustration of what a domestic fusion development path can look like in practice.

At a Glance — For Decision-Makers

708 GW peak demand and 2,100 GW total capacity needed by 2047 — the equivalent of building a new US power grid from scratch.

Intermittent renewables alone cannot provide firm power — grid stability requires large-scale dispatchable baseload even with abundant storage.

Fusion now has serious private capital behind it: Microsoft, Google, and OpenAI are structuring power purchase agreements with fusion companies. India risks being a technology importer.

Three budget-cycle asks for 2026: fusion in National Energy Plan · dedicated component development fund · AERB regulatory engagement mandate.

Key Number

India’s Central Electricity Authority projects peak power demand reaching 708 GW by 2047 — four times today’s installed capacity. Meeting it requires 2,100 GW of generation: close to the entire current installed capacity of the US and EU combined. That is the scale of infrastructure build India must manage across the next two decades.

The Silent Contamination : What Nuclear Waste Does to Our Water

A young mother in Knightdale, North Carolina recently learned that her tap water contained uranium at twelve times the safe limit — and that her infant son had been drinking it for a year. The uranium was natural. But it points to a much deeper problem: the millions of tonnes of spent nuclear fuel buried in geological repositories worldwide, isolated by engineered barriers designed to last thousands of years while the waste inside remains hazardous for hundreds of thousands. Does fusion technology offer the only real solution?

And why fusion technology may hold the key to breaking its millennia-long grip on our environment

📰 What sparked this post Earlier this month, a young mother in Knightdale, North Carolina, received two letters in her mailbox from Carolina Water Service informing her that uranium levels in her tap water had tested at 250 picocuries per litre — twelve times the US federal safety standard. Her one-year-old son had been drinking that water, mixed into his formula, for the entirety of his short life. The well had been testing clean for five consecutive years. Nobody had any warning. The utility, WRAL News reported on 20 February 2026, tests for uranium only once a year.

I read that report and felt the familiar, uncomfortable weight of a problem I have spent decades worrying. The uranium in that Knightdale well was almost certainly natural — leached from granite bedrock by groundwater as it has been doing since long before human civilisation. But the story it tells becomes far more urgent when you consider what we have deliberately added to the geological environment over the past eighty years: millions of tonnes of radioactive material, far more concentrated and persistent than anything nature placed there, buried across hundreds of sites worldwide. If natural uranium can contaminate a neighbourhood well quietly, over years, undetected — what does that tell us about the long-term safety of the radioactive legacy we are choosing to leave underground?

There is a kind of danger that does not announce itself. It moves silently through cracks in bedrock and channels of groundwater, carrying with it some of the most persistent poisons humanity has ever created — thousands of tonnes of spent nuclear fuel and high-level waste from decades of fission power generation, stored in temporary facilities and deep geological repositories, with the quiet hope that they will remain isolated for the ten thousand years or more that their radioactivity demands. That hope, I am afraid, rests on a geological optimism that the story from Knightdale does not entirely justify.

The Burial Problem: Out of Sight Is Not Out of Mind

The logic behind deep geological disposal is sound in principle. Take the waste deep enough — typically 300 to 1,000 metres underground — into stable rock formations of granite, clay, or salt, and isolate it from the biosphere for geological timescales. Countries including Finland, Sweden, and Canada have invested heavily in this approach. India, too, through its Department of Atomic Energy, manages vitrified high-level waste in stainless steel canisters awaiting eventual deep burial.

The problem is the word eventually. Spent nuclear fuel contains a cocktail of long-lived radionuclides. Plutonium-239 has a half-life of 24,100 years. Technetium-99 has a half-life of 211,000 years. Iodine-129 decays over 15.7 million years. The engineered barriers — steel canisters, bentonite clay buffers, concrete vaults — are designed to last centuries, perhaps a few thousand years. But the radioactive material inside them demands isolation for hundreds of thousands of years. No engineered structure in human history has lasted that long. The Egyptian pyramids are 4,500 years old and already substantially degraded.

⚠ Critical Context

The Timescale Mismatch

The engineered barriers in deep geological repositories are designed to last at most a few thousand years. The long-lived actinides inside them — plutonium, americium, neptunium — remain radiologically hazardous for hundreds of thousands to millions of years. No engineered containment system in history has bridged this gap.

When Water Meets Radioactivity

Water is the great dissolver. Given enough time, groundwater will find every crack, every imperfection, every microscopic flaw in the engineered barriers of a repository. When it does, it will begin to leach radionuclides and carry them outward through the rock, toward aquifers, rivers, and ultimately the food chain.

This is not a hypothetical case. At the Hanford Site in Washington State, USA — the largest nuclear waste site in the Western Hemisphere — radioactive contamination has migrated into the Columbia River through groundwater. Tritium, strontium-90, and technetium-99 have all been detected in monitoring wells between the site and the river. The US government has spent over $20 billion on cleanup, and the problem remains unresolved. In the Marshall Islands, the Runit Dome — a concrete cap built over nuclear test debris — sits at sea level, and rising ocean waters are already infiltrating its base, mobilising radioactive material into the Pacific.

The mechanisms are well understood by hydrogeologists. Radionuclides differ dramatically in their mobility through soil and rock. Cesium-137 and strontium-90 tend to adsorb onto mineral surfaces and migrate slowly. Tritium (radioactive hydrogen) and iodine-129 behave like water itself and can travel enormous distances rapidly. Technetium-99, in its pertechnetate form, is highly mobile and poorly retained by most geological materials. Once these isotopes enter an aquifer, remediation is extraordinarily difficult.

24,100 Years Half-life of Plutonium-239, the dominant actinide in spent fuel

~250k Tonnes Spent nuclear fuel in storage worldwide, growing ~10,000 t/year

10⁶ Years Isolation time needed for Iodine-129 to reach background levels

The Indian Context: A Growing Inventory

India operates 24 nuclear reactors with more under construction, and the DAE’s vision for a three-stage fuel cycle — natural uranium pressurised heavy water reactors, fast breeder reactors, and eventually thorium-fuelled reactors — will produce substantial quantities of spent fuel and radioactive waste for decades. The Bhabha Atomic Research Centre manages this waste responsibly by global standards, with vitrification plants at Tarapur and Trombay converting liquid high-level waste into borosilicate glass, and interim storage in air-cooled vaults. But interim is not permanent. The waste continues to accumulate, and the long-term disposal solution remains to be finalised.

India’s geology presents both opportunities and challenges for deep disposal. The Deccan Traps basalts, Precambrian granites of Rajasthan and Karnataka, and Gondwana sedimentary formations are all under investigation. However, India is seismically active, and the hydrological connectivity of hard-rock aquifers in peninsular India is not fully characterised. The consequences of a repository breach — even a slow, diffusive one — for communities dependent on groundwater in rural India would be severe and essentially irreversible. This is why India needs a two-pronged strategy: continued, well-funded site characterisation to identify the safest possible repository locations, pursued in parallel with fusion-driven transmutation research that progressively reduces the volume and longevity of the material that must be stored. ASPL Fusion sees itself as a partner in that national strategy — not as a replacement for rigorous geological work, but as the scientific complement to it.

“The question we must ask is not only where to store nuclear waste safely — but whether we can transform it from a millennial burden into a resource. That is the question fusion science must answer.”

— Prof. Prabhat Ranjan, Co-founder & Nuclear Fusion Scientist, ASPL Fusion

Transmutation: Changing the Problem at Its Root

What if the answer to radioactive waste is not better burial, but transformation? This is the principle of nuclear transmutation — using neutrons to convert long-lived radioisotopes into shorter-lived or even stable nuclides. The physics is straightforward: a neutron capture event can convert a problematic long-lived nucleus into one that decays much faster, or even into a stable, non-radioactive element. Transmutation does not eliminate radioactivity immediately, but it can dramatically reduce the required isolation time from hundreds of thousands of years to hundreds — a difference of three orders of magnitude that makes engineered containment genuinely feasible.

The challenge has always been producing neutrons in sufficient intensity and at the right energies to drive transmutation efficiently. Fast neutrons — those with energies in the MeV range — are particularly effective at inducing fission in transuranic actinides, the most radiologically hazardous long-lived components of spent nuclear fuel. This is precisely where fusion technology enters the picture.

It is worth being precise about what we are actually trying to destroy. Of the spent fuel discharged from a fission reactor, roughly 95% is uranium — material that can be recycled into new fuel in a closed fuel cycle. Another 4% or so is fission products, most of which decay to benign levels within a few hundred years. The true long-term problem is the remaining fraction: the minor actinides — americium, neptunium, and curium — which constitute barely 0.1% of spent fuel by mass but are responsible for the overwhelming majority of the radiological hazard beyond 1,000 years. Remove that 0.1% through transmutation, and the isolation time required for the remainder drops from hundreds of thousands of years to roughly 300 years — a timescale within the credible reach of engineered barriers and, crucially, within human institutional memory.

The Fusion-Fission Hybrid: How It Works

A fusion-fission hybrid couples a fusion neutron source to a sub-critical fission blanket loaded with spent nuclear fuel or separated minor actinides. The fusion device — in ASPL Fusion’s case, a Gas Dynamic Trap (GDT) operating on deuterium-tritium fuel — produces intense fluxes of 14.1 MeV neutrons directed into the surrounding blanket, driving fission of the actinide inventory without the blanket ever sustaining a chain reaction on its own.

The choice of the GDT as the neutron source is deliberate. Unlike toroidal devices such as tokamaks, a GDT is a linear magnetic mirror machine: its open, cylindrical geometry makes it inherently well suited for surrounding with a concentric fission blanket, since there is no toroidal geometry to work around. The GDT also operates in steady state rather than producing pulsed neutron bursts, which matters enormously for the thermal and mechanical engineering of the blanket and for achieving sustained transmutation rates.

This sub-criticality is the system’s defining safety feature. Unlike a conventional fission reactor, the assembly cannot run away: switch off the fusion source and all fission reactions stop immediately. There is no possibility of a Chernobyl or Fukushima-type criticality event. The physics simply does not permit it.

Inside the blanket, the fast neutrons accomplish two things simultaneously. First, they fission transuranic actinides — plutonium, americium, neptunium, curium — converting them into shorter-lived fission products. A nuclide requiring 24,000 years of isolation becomes one requiring roughly 300 years. Second, neutron capture in a lithium layer breeds tritium, replenishing the fusion fuel. The system can in principle be self-sustaining in tritium and generate net electrical power while consuming the most hazardous fraction of the waste inventory.

Figure 1: The fusion-fission hybrid closed loop. D-T fusion drives a sub-critical fission blanket; fission heat generates electricity; lithium breeds tritium to replenish fusion fuel.

🔬 Science Note

Why 14 MeV Neutrons Matter for Transmutation

Fast neutrons from D-T fusion carry 14.1 MeV of energy — far above the fission thresholds of minor actinides like americium-241 and curium-244, which are very difficult to fission with the lower-energy neutrons available in a conventional thermal reactor. D-T fusion neutron sources can therefore access and destroy actinides that conventional reactors largely cannot.

What Transmutation Can — and Cannot — Do

Transmutation is not a silver bullet. The global inventory of spent nuclear fuel — approximately 250,000 tonnes and growing by around 10,000 tonnes each year — is enormous, and no single device will process all of it. Critics rightly raise the economics: transmutation is energy-intensive, and the costs are significant. But the fusion-fission hybrid addresses this directly. The fission reactions in the sub-critical blanket generate substantial heat, which can be converted to electricity. In a mature system, this electricity generation partially or fully offsets the cost of waste processing — turning a pure liability into a partial energy asset. Regulatorily, sub-critical systems present new challenges; most existing nuclear frameworks were designed around critical reactors. Updated regulatory pathways for driven sub-critical assemblies will need to be developed in dialogue with AERB in India and equivalent bodies internationally. This is work that needs to begin now, in parallel with the physics.

ASPL Fusion is advancing this programme in India, working toward a GDT-based fusion neutron device capable of driving a sub-critical blanket — a system that addresses the waste hazard at its root rather than managing its symptoms indefinitely underground.

Comparison: Deep Burial vs. Fusion-Driven Transmutation

Feature	Conventional Burial	Fusion-Driven Transmutation
Isolation Time Required	100,000+ Years	~300 Years
Primary Barrier	Geological Formations	Engineered Containment
Actinide Hazard	Passively Decaying	Actively Fissioned
Economic Value	Pure Liability	Partial Energy Asset
Safety Basis	Geological Stability	Sub-critical Physics

The radioactive waste buried under our mountains and stored in our cooling ponds will not simply go away. The water will, eventually, find it. The question is whether we act now, with the best science available, to transform the problem before it transforms our groundwater. Fusion technology — specifically the intense fast-neutron fluxes that only fusion can produce — offers a path that fission alone cannot. I have spent my career in this field, from the plasma physics laboratories of UC Berkeley to leading India’s Technology Vision 2035 as Head of TIFAC, and I have never been more confident that this path is real, achievable, and urgently necessary.

We owe it to the generations who will inherit this planet to do more than bury the problem deeper. We owe them a solution.

Learn More About ASPL Fusion’s Work

Fusion-driven transmutation research, the Gas Dynamic Trap programme, and India’s path to closing the nuclear waste cycle.

Visit asplfusion.com →