Pressurised Heavy Water Reactors

Source: BS

Context: The Atomic Energy Regulatory Board (AERB) has granted operational licences to NPCIL for two indigenous 700 MWe Pressurised Heavy Water Reactors (PHWRs) at Kakrapar Atomic Power Station (Units 3 & 4) in Gujarat.

About Pressurised Heavy Water Reactors:

• What is a PHWR?

• A nuclear fission reactor that uses natural uranium as fuel and heavy water (D₂O) as both coolant and neutron moderator. Designed to operate with online refuelling, allowing continuous energy production.

• A nuclear fission reactor that uses natural uranium as fuel and heavy water (D₂O) as both coolant and neutron moderator.

• Designed to operate with online refuelling, allowing continuous energy production.

• Developed By:

• Initially with Canadian support (Rajasthan-1), later fully indigenised by BARC (Bhabha Atomic Research Centre) and NPCIL (Nuclear Power Corporation of India Ltd) under the Department of Atomic Energy.

• Historical Evolution:

• RAPS-1 (1973): With Canadian collaboration. RAPS-2 onwards: Entirely developed by Indian scientists post-AECL withdrawal. Progression from 220 MWe → 540 MWe → 700 MWe with full domestic R&D and manufacturing.

• RAPS-1 (1973): With Canadian collaboration.

• RAPS-2 onwards: Entirely developed by Indian scientists post-AECL withdrawal.

• Progression from 220 MWe → 540 MWe → 700 MWe with full domestic R&D and manufacturing.

• How Does It Work?

• Uses heavy water as moderator to slow down neutrons and maintain a sustained chain reaction. Fuel rods (natural uranium) are inserted into pressure tubes within a calandria vessel. Hot pressurised heavy water carries heat to steam generators → drives turbines → generates electricity. Control rods and ECCS systems regulate power output and enhance safety.

• Uses heavy water as moderator to slow down neutrons and maintain a sustained chain reaction.

• Fuel rods (natural uranium) are inserted into pressure tubes within a calandria vessel.

• Hot pressurised heavy water carries heat to steam generators → drives turbines → generates electricity.

• Control rods and ECCS systems regulate power output and enhance safety.

• Key Features of 700 MWe PHWRs:

• Fully indigenous design and operation, including construction, fuel fabrication, and control systems. Online refuelling system improves efficiency and reduces downtime. Equipped with twin fast-acting shutdown systems, double containment, and passive heat removal. Digital Instrumentation and Control Systems enhance real-time safety and automation. On-site heavy water moderation and cooling reduces external dependency and enriches neutron economy.

• Fully indigenous design and operation, including construction, fuel fabrication, and control systems.

• Online refuelling system improves efficiency and reduces downtime.

• Equipped with twin fast-acting shutdown systems, double containment, and passive heat removal.

• Digital Instrumentation and Control Systems enhance real-time safety and automation.

• On-site heavy water moderation and cooling reduces external dependency and enriches neutron economy.

• Significance of Recent Licence:

• Boosts India’s 10-reactor PHWR fleet mode rollout, part of its strategy to add 7000 MWe capacity indigenously. Confirms that India has mastered end-to-end nuclear tech from design to decommissioning.

• Boosts India’s 10-reactor PHWR fleet mode rollout, part of its strategy to add 7000 MWe capacity indigenously.

• Confirms that India has mastered end-to-end nuclear tech from design to decommissioning.