Fifth unit of Kudankulam nuclear power project likely to be operational by year-end

The Nuclear Power Corporation of India Limited (NPCIL) has successfully completed erection of the Reactor Pressure Vessel (RPV) inside the reactor building o...

What Happened

The Nuclear Power Corporation of India Limited (NPCIL) has successfully completed erection of the Reactor Pressure Vessel (RPV) inside the reactor building of Unit 5 at the Kudankulam Nuclear Power Project (KKNPP) in Tamil Nadu — a critical milestone in the unit's commissioning sequence.
The RPV, weighing approximately 320 tonnes, houses the reactor core where nuclear fission takes place; its installation marks the beginning of Nuclear Steam Supply System (NSSS) equipment erection for Unit 5.
NPCIL has indicated that Unit 5 is expected to become operational by the end of 2026 (December 2026 is the targeted commissioning date), which would advance India's installed nuclear capacity.
The Atomic Energy Regulatory Board (AERB) granted clearance for major equipment erection at Units 5 and 6 on April 30, 2026, enabling installation to proceed at both units simultaneously.
The Kudankulam site comprises six VVER-1000 units, each of 1,000 MW capacity; Units 1 and 2 are already operational, while Units 3–6 are under various stages of construction. Full site capacity of 6,000 MW is expected by 2027.

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Kudankulam Nuclear Power Plant (KKNPP)

KKNPP is located in the Tirunelveli district of Tamil Nadu on India's southern tip. It is the largest nuclear power station in India by installed capacity and is being developed jointly by NPCIL and Russia's Rosatom State Atomic Energy Corporation (through its subsidiary Atomstroyexport) under an Inter-Governmental Agreement (IGA).

Location: Kudankulam, Tirunelveli district, Tamil Nadu
Reactor type: VVER-1000 (Vodo-Vodyanoi Energetichesky Reaktor) — a pressurised water reactor of Russian design
Capacity per unit: 1,000 MW gross electrical (917 MW net); thermal capacity 3,000 MW per unit
Total planned capacity: 6,000 MW across 6 units
Units 1 & 2: Operational (Unit 1 commercial operation from 2013; Unit 2 from 2016)
Units 3 & 4: Under construction
Units 5 & 6: Unit 5 concrete pour began 2020; Unit 6 construction began 2021; Unit 6 commissioning expected September 2027
Operator: Nuclear Power Corporation of India Limited (NPCIL) under the Department of Atomic Energy (DAE)
Russian partner: Rosatom / Atomstroyexport; Russia also provides nuclear fuel for Units 1 and 2
Regulatory body: Atomic Energy Regulatory Board (AERB) — India's independent nuclear safety regulator

Connection to this news: Unit 5's RPV erection is the first major equipment installation in the reactor building, putting the commissioning timeline on track.

India's Three-Stage Nuclear Power Programme

Conceived by physicist Homi J. Bhabha in the 1950s, India's three-stage programme is designed to exploit the country's vast thorium reserves — India holds approximately 25% of global thorium reserves but only 1–2% of global uranium reserves.

The Three Stages: - Stage I: Pressurised Heavy Water Reactors (PHWRs) fuelled by natural uranium produce electricity and generate plutonium as a by-product. Most of India's existing reactors (PHWR design, domestically built at Rawatbhata, Kakrapar, Kaiga, etc.) are in this stage. VVER-1000 reactors at Kudankulam, though light-water reactors, supplement Stage I capacity. - Stage II: Fast Breeder Reactors (FBRs) fuelled by plutonium from Stage I breed more fissile material (uranium-233) from thorium. India's first commercial FBR at Kalpakkam (PFBR — 500 MW) is under final commissioning stages. - Stage III: Advanced thorium-based reactors using uranium-233 breed in Stage II for sustained, large-scale power generation using India's thorium reserves.

Governed by: Department of Atomic Energy (DAE); statutory basis — Atomic Energy Act, 1962
Nodal agency for power generation: NPCIL (Nuclear Power Corporation of India Limited)
Research arm: BARC (Bhabha Atomic Research Centre) for fuel cycle and reactor R&D
India's current nuclear installed capacity: approximately 7,480 MW (from 23 operational reactors as of 2025–26)

Connection to this news: VVER-1000 units at Kudankulam augment Stage I capacity, freeing domestically produced plutonium for Stage II FBRs and advancing India's long-term energy independence strategy.

Nuclear Energy and India's Clean Energy Transition

India has committed under its Nationally Determined Contributions (NDCs) to achieve 500 GW of non-fossil fuel-based electricity capacity by 2030 and net-zero carbon emissions by 2070. Nuclear power, as a near-zero-carbon baseload source, is central to this transition.

Nuclear power produces approximately 10–50 grams of CO₂-equivalent per kWh over its lifecycle — lower than solar PV (~40–50 g/kWh) and far below coal (~820 g/kWh)
India targets raising nuclear capacity to 22,480 MW by 2031–32 (as per the Department of Atomic Energy's planning)
The Union Cabinet approved ten new PHWRs (7,000 MW total) in fleet mode in 2017 under the NPCIL programme
The Electricity Act 2003 and Atomic Energy Act 1962 together govern nuclear power's role in India's grid

Connection to this news: Each new Kudankulam unit adds 917 MW net to the grid without CO₂ emissions, directly contributing toward India's clean energy targets.

VVER-1000 Reactor Technology

The VVER (Vodo-Vodyanoi Energetichesky Reaktor) is a series of pressurised water reactors designed in the Soviet Union/Russia. The VVER-1000 (also designated as AES-92 in its export configuration at Kudankulam) is a Generation III design.

Coolant/Moderator: Light water (H₂O) for both
Fuel: Low-enriched uranium dioxide (UO₂) pellets in zirconium alloy cladding
Design safety features: Double containment, passive safety systems, emergency core cooling
Thermal efficiency: ~32–33%
Operating countries: Russia, China, India, Iran, Czech Republic, Hungary, Finland (Loviisa), Bulgaria, Slovakia
Reactor Pressure Vessel (RPV): The central component — a thick-walled steel vessel housing the reactor core, control rods, and coolant; its installation is the landmark structural milestone in reactor construction

Connection to this news: The RPV erection at Unit 5 is the structural centrepiece of nuclear island assembly and signifies that civil construction is complete enough to install reactor-grade components.

Key Facts & Data

Reactor type at Kudankulam: VVER-1000 (pressurised water reactor, Russian design)
Capacity per unit: 1,000 MW gross / 917 MW net
Total KKNPP capacity: 6,000 MW (6 units)
RPV weight (Unit 5): ~320 tonnes
AERB equipment clearance date: April 30, 2026
Unit 5 commissioning target: December 2026
Unit 6 commissioning target: September 2027
Indo-Russian IGA: First signed in 1988; technology cooperation agreement updated multiple times
NPCIL mandate: Statutory body under DAE; operates all civilian nuclear power plants in India
India's nuclear installed capacity (2025–26): ~7,480 MW across 23 reactors
India's thorium reserves: ~25% of global known reserves (~593,000 tonnes)
Atomic Energy Act: 1962 — provides statutory basis for DAE, NPCIL, and AERB