Third Indigenous Pressurised Heavy Water Reactor Attains Criticality: NPCIL

India’s third home-built 700 MWe nuclear power reactor has achieved criticality and is expected to start commercial electricity generation soon.

Nuclear Power Corporation of India Limited (NPCIL)

Mission: To generate safe, environmentally friendly, and economical nuclear power.
Establishment: Founded in 1987 under the Companies Act of 1956.
Currently operates 22 commercial nuclear power reactors, with 9 more under construction.

Pressurised Heavy Water Reactor (PHWR):A pressurised heavy water reactor (PHWR) is a nuclear power reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water (deuterium oxide D2O) as its coolant and moderator
PHWR Development in India: India’s first PHWR was constructed in the late 1960s at the Rajasthan Atomic Power Station (RAPS-1), built through Indo-Canadian collaboration.

NPCIL

Criticality is the point where a nuclear reactor achieves a self-sustaining chain reaction, with nuclear fission occurring at a steady rate.

Natural uranium: Contains 99.27% uranium-238 (U-238) and 0.711% uranium-235 (U-235). It’s mined from the ground and can be used to fuel nuclear reactors.
Enriched uranium: Contains more than 0.73% U-235, which is the energy source for reactors and weapons. There are different levels of enrichment:
- Low enriched uranium: Contains 0.711% to 20% U-235. It’s used in civilian reactors.
- Highly enriched uranium: Contains more than 20% U-235. It’s used in naval reactors and weapons production

Significance: Achieving criticality marks the reactor’s readiness to generate power, as it indicates stable, controlled nuclear reactions. For India, this represents the progression of its nuclear energy capacity.
The successful achievement of criticality of RAPP-7 is third after the smooth operation of Kakrapar Atomic Power Station(KAPS) Reactor 3 and 4, the first two 700 MWe PHWRs.

Energy Independence: PHWRs can use natural uranium, avoiding reliance on enriched uranium imports.
Alternate Fuel Cycles: The technology allows the efficient use of alternate fuel cycles, making it versatile and sustainable for long-term energy generation.
India’s first PHWR, RAPS-1, began the nation’s journey in nuclear power, which continues with advancements like the recent 700 MWe reactor.

Light Water Reactors (LWR): Use ordinary water as both coolant and moderator, typically fueled by low-enriched uranium. LWRs come in two types:
- Pressurised Water Reactor (PWR): Water circulates in a closed loop and transfers heat to a steam generator.
- Boiling Water Reactor (BWR): Water boils in the reactor core, and the resulting steam directly drives turbines.
Fast Breeder Reactor (FBR):
- Fuel: Mixed Oxide (MOX) fuel, made from plutonium and depleted uranium.
- Coolant: Liquid sodium, with no moderator.
- Example: The Prototype Fast Breeder Reactor (PFBR) at Kalpakkam is part of India’s second stage in its three-stage nuclear program.

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