A detailed PIB Backgrounder lays out India's nuclear energy architecture — from reactor types and fuel cycles to the three-stage programme — against the backdrop of the Nuclear Energy Mission (2025–26) and the government's 100 GW target by 2047.

• Nuclear fission: A neutron strikes a uranium or plutonium nucleus, splitting it and releasing heat plus more neutrons, which sustain a chain reaction.
• Heat-to-electricity: The heat converts water to high-pressure steam → steam drives a turbine → turbine turns a generator.
• Fuels used: Natural Uranium (India's PHWRs), Low-Enriched Uranium (most global reactors), Plutonium-239 and Mixed Oxide (MOX) fuel (India's PFBR).
• Fissile vs fertile: Fissile materials (U-235, Pu-239, U-233) directly sustain a chain reaction; fertile materials (Th-232, U-238) must first be converted inside a reactor.

• Pressurised Heavy Water Reactors (PHWRs): India's primary reactor type; use natural uranium as fuel (no enrichment needed) and heavy water as moderator and coolant. Ten fleet-mode PHWRs approved.
• Boiling Water Reactors (BWRs) / Pressurised Water Reactors (PWRs): Also in operation in India.
• Fast Breeder Reactors (FBRs): Use plutonium as fuel; breed more fissile material than they consume; critical for Stage 2 of the three-stage programme. Pre-project activities underway for two 500 MW FBRs.
• Small Modular Reactors (SMRs): Next-generation technology under development; output up to 300 MW(e); suited for distributed deployment.

Figure 1 — Nuclear Reactor Classification (Source: IAEA, PIB)

Reactor classification by capacity: conventional large reactors power cities; SMRs serve industrial clusters; microreactors can be mobile or deployed in remote areas. Image courtesy Press Information Bureau (PIB), Government of India; reproduced for educational use.

• Stage 1 — PHWRs: Use natural uranium to generate power and produce plutonium as a by-product.
• Stage 2 — FBRs: Use Stage-1 plutonium as fuel; breed additional plutonium and U-233 from thorium blankets, creating more fuel than consumed.
• Stage 3 — Advanced Heavy Water Reactors (AHWRs): Use U-233 bred from thorium; thorium becomes the primary fuel — leveraging India's vast Th reserves for long-term energy self-sufficiency.

• High-level waste (3% by volume, 95% of radioactivity): Spent nuclear fuel; immobilised in glass (vitrification) and stored.
• Intermediate-level waste (7% volume, 4% radioactivity): Used filters, steel reactor components, reprocessing effluents.
• Low-level waste (90% volume, 1% radioactivity): Lightly contaminated tools, clothing; managed under standard safety protocols.
• Closed fuel cycle: India reprocesses spent fuel to recover usable plutonium and U-233, reducing waste volume and supporting Stage 2 and 3.

Figure 2 — Types of Nuclear Waste (Source: World Nuclear Association, PIB)

Although high-level waste is a tiny fraction by volume, it accounts for the overwhelming share of radioactivity — underlining why safe storage and reprocessing matter. Image courtesy Press Information Bureau (PIB), Government of India; reproduced for educational use.

• Nuclear Energy Mission (2025–26): Targets accelerated capacity expansion and indigenisation of the nuclear supply chain.
• SHANTI Act, 2025: Enables greater private-sector participation in nuclear power — a significant departure from the earlier exclusively public-sector model; aimed at mobilising additional investment to reach the 100 GW target.
• Predecessor context: India's Atomic Energy Act, 1962 had long restricted nuclear activities to government entities; SHANTI represents a structural shift.

• Energy security: Nuclear provides baseload (round-the-clock) power unlike most renewables — reducing dependence on imported fossil fuels.
• Climate commitments: Low-carbon output supports India's NDC targets under the Paris Agreement.
• Indigenisation (Aatmanirbhar Bharat): Development of indigenous reactor design, fuel fabrication, reprocessing and waste management is a stated policy goal.
• Thorium advantage: India's thorium reserves give it a long-term fuel security edge unavailable to most nuclear powers.

• Cost and delay: Nuclear projects historically face significant cost overruns and construction delays in India and globally.
• Waste and safety: High-level radioactive waste requires geological-timescale management; public acceptance near proposed sites remains a challenge.
• Uranium import dependence: Stage 1 relies on imported uranium; geopolitical disruptions could affect supply until Stage 2 (FBRs) scales up.
• Private sector readiness: SHANTI enables private entry but regulatory capacity and liability frameworks need strengthening before meaningful private investment flows.
• Prototype PFBR delays: The 500 MW Prototype Fast Breeder Reactor at Kalpakkam has faced repeated commissioning delays, slowing the Stage 2 transition.

The Department of Telecommunications (DoT) and C-DOT have formalised a five-year agreement to set up a state-of-the-art End-to-End Optical Network Testbed — a shared national facility aimed at bridging the gap between lab-stage innovation and commercial deployment in optical communications.

• Gap being bridged: Most Indian telecom startups and researchers can prototype solutions in labs but lack access to a real-world network environment for validation — the testbed provides this.
• Shared national resource: Open to startups, industry players, students and researchers for innovation, testing and skill development.
• Quantum security component: Inclusion of quantum security technologies signals focus on future-proofing communications against quantum-computing threats.
• Commercialisation support: The facility is designed to help home-grown products reach market readiness — a key bottleneck in India's technology transition from imported to indigenous gear.

• C-DOT: Established under DoT; known for indigenous CDMA-based rural telephony solutions in the 1990s; now developing 5G, optical and quantum communication technologies.
• DoT: Apex regulatory and policy body for telecommunications in India.
• Linkage to national programmes: Consistent with the Aatmanirbhar Bharat push in critical digital infrastructure and with Production Linked Incentive (PLI) schemes for telecom equipment.

• Utilisation risk: Government-funded testbeds in India have historically suffered from under-utilisation by private startups due to complex access processes; sustained outreach and simplified onboarding will be essential.
• Market linkage gap: Testing and validation facilities help, but without parallel demand creation (e.g., government procurement preferences for indigenous optical equipment), commercial scale-up remains uncertain.
• Human resource constraint: India's pipeline of optical communication engineers is thin; the testbed's skill-development component must actively draw students from engineering institutions to be transformative.