Inside the Bhabha Atomic Research Centre’s sprawling campus at Trombay, three parallel design teams are working on three fundamentally different reactor concepts — each one an answer to a different question India is asking about its energy future. Understanding each design is to understand how sophisticated India’s nuclear thinking has become: not one solution deployed at scale, but a differentiated portfolio addressing distinct segments of a complex national energy demand.
The BSMR-200, a 200 megawatt-electric Small Modular Reactor, is the grid-power candidate. It is designed as a pressurised water reactor operating on low-enriched uranium fuel, compact enough for factory-fabricated module manufacture yet powerful enough to anchor a regional grid node. Its target application is the retirement of ageing coal plants in Tier-2 industrial clusters where large nuclear plants cannot be sited but where baseload reliability is non-negotiable. A single BSMR-200 unit, paired with renewables, could replace a 250 MW coal plant with a capacity factor exceeding 90 percent.
Three SMR designs simultaneously in active development is not redundancy — it is the recognition that India’s energy challenge is not a single problem but a constellation of distinct demands requiring purpose-engineered answers.
The design philosophy of the BSMR-200 reflects hard lessons from India’s existing PHWR fleet. The reactor incorporates passive safety systems — natural circulation cooling loops, gravity-driven emergency water injection — that eliminate the need for active pump operation during loss-of-coolant scenarios. The post-Fukushima global consensus that passive safety is non-negotiable in new reactor design has been absorbed fully into the BSMR-200 architecture.
The SMR-55, at 55 MWe, addresses a different challenge entirely. India has extensive remote industrial infrastructure — mining operations, defence installations, island territories, remote research stations — where grid connectivity is either absent or unreliable, and where diesel generation carries both cost and logistics burdens that become prohibitive at scale. The SMR-55 is designed for disaggregated deployment: a reactor small enough to be transported in modular segments, with a refuelling cycle long enough to minimise on-site nuclear expertise requirements, and with security and containment systems engineered for environments without large exclusion zones.
This design draws on the conceptual heritage of naval reactor technology — where the premium on compactness, autonomy of operation, and long refuelling intervals has driven nuclear engineering to its most elegant miniaturised forms. BARC engineers working on the SMR-55 are explicit about the influence of submarine propulsion reactor design thinking on the architecture, though the civilian application introduces constraints of cost and public licensing that military programmes do not face.
The third concept — a 5 megawatt-thermal High Temperature Gas Cooled Reactor — is the most technologically ambitious and the most forward-looking. It is not primarily a power reactor. It is a hydrogen reactor. Using helium as coolant at outlet temperatures approaching 950 degrees Celsius, it provides the sustained high-temperature process heat that thermochemical hydrogen production cycles require. The sulphur-iodine cycle, which BARC has been researching for over a decade, uses heat rather than electricity to split water into hydrogen and oxygen — achieving efficiencies that electrolysis cannot match.
Hydrogen sits at the centre of India’s decarbonisation calculus for industrial sectors — steelmaking, fertiliser production, heavy transport — that cannot be directly electrified. The National Green Hydrogen Mission targets 5 million metric tonnes of annual green hydrogen production by 2030. If the HTGCR-based thermochemical route achieves its projected conversion efficiencies, nuclear hydrogen could complement electrolytic hydrogen at the scale India requires, particularly for co-location with steel mills where high-temperature process heat is simultaneously valuable.
The three designs are not competing for a single budget line. Each addresses a distinct market segment, and the DAE’s SMR strategy envisions a mixed deployment depending on demand geography and application. The BSMR-200 for industrial grid anchors, the SMR-55 for remote and defence applications, and the HTGCR for hydrogen corridors — this is portfolio thinking applied to national energy infrastructure.
Timelines remain the honest constraint. BARC’s design programmes are advanced but pre-licensing. The regulatory pathway through the Atomic Energy Regulatory Board for novel reactor designs is thorough and appropriately cautious. Optimistic projections place the first SMR-200 construction start no earlier than 2029-30. First power from an SMR unit before 2034 would represent strong execution. These are not criticisms — they are the physics and engineering of what responsible nuclear development requires.
– Ravindranath P
