SYLLABUS

GS 2: Bilateral, regional and global agreements involving India (civil nuclear cooperation);

GS 3: Science and Technology – developments and their applications and effects in everyday life; Indigenisation of technology and developing new technology; Infrastructure: Energy sector; Conservation, environmental pollution and degradation (clean energy aspect).

Context: According to a recent statement by the Chairman of NTPC Parmanu Urja Nigam Ltd (NPUNL), NTPC is in talks with the United States, Russia, and France regarding import of Pressurised Water Reactor (PWR) technology for its planned nuclear fleet.

More on the News

• NTPC plans to develop 30 GWe of capacity using a mix of indigenous Pressurised Heavy Water Reactors (PHWRs) and imported Pressurised Water Reactors (PWRs).
  o For this purpose, NTPC has formed NPUNL in January 2025 and plans to build 30 GWe of nuclear power by 2047.
• Under the Union Government’s target of 100 GWe nuclear capacity by 2047, about 70–75% is expected to come from the public sector, with the remaining share contributed by private players.

About Pressurised Water Reactors (PWR) Technology

Basic Concept

• A Pressurised Water Reactor (PWR) is a type of light water nuclear reactor in which ordinary water is used both as a coolant and as a moderator. 
• The defining feature of this technology is that the reactor core's water is maintained at very high pressure, preventing boiling even at high temperatures.
• PWRs use enriched uranium as fuel and are the most widely deployed nuclear reactors globally due to their reliability and proven design.

Working Principle

• The operation of a PWR is based on a two-loop system:
  o In the primary circuit, water maintained at very high pressure absorbs heat produced by nuclear fission in the reactor core and reaches temperatures of about 300–325°C without boiling. This heated water is then directed to a steam generator, where it transfers its heat to a separate secondary circuit.
  o In the secondary circuit, the heat received converts water into steam, which drives turbines to generate electricity.
  o The physical separation between the two circuits ensures that radioactive substances remain restricted to the primary loop, thereby improving safety.

Key Components

• Reactor core: Contains fuel rods made of enriched uranium and control rods to regulate the fission reaction.
• Pressure vessel: Encloses the core and maintains high-pressure conditions
• Pressurizer: Controls the pressure of the primary loop to prevent boiling.
• Steam generator: Transfers heat between loops.
• Coolant pumps: Ensure continuous water circulation in the primary loop.

Salient Features

• Two-loop design minimises the risk of radioactive contamination outside the reactor core.
• The operation of the reactor at high pressure ensures the liquidity of water even at elevated temperatures.
• Negative temperature coefficient enhances safety by automatically reducing the rate of nuclear reactions as the temperature rises.
• PWRs are also known for their operational stability and high-power output.

Significance of PWRs

• PWRs are considered safe due to stable design, inherent safety features, and multiple containment systems  
• The secondary loop remains non-radioactive, ensuring turbine safety and easier maintenance 
• Use of ordinary water in coolant and moderator, makes PWRs economically and operationally viable
• Most proven and widely used reactor (about 60-65% globally) 
• PWRs have high power density, enabling compact reactor design with significant output 

Challenges

• Requires very high pressure, making the technology expensive and a complex design.
• The need for enriched uranium (U-235) raises fuel costs. 
• Thermal efficiency is slightly lower compared to some advanced reactor types due to indirect heat transfer via two-loop systems 
• PWRs require periodic shutdowns for refuelling, unlike PHWRs which allow online refuelling 

Relevance for India

• Crucial for expanding nuclear power capacity and achieving long-term energy security. 
• While India has traditionally relied on Pressurised Heavy Water Reactors (PHWRs), plans include a mix of indigenous and imported PWRs to meet ambitious nuclear energy targets. 
• The adoption of PWRs will support India’s transition towards clean energy and help in meeting climate commitments, including the goal of achieving net-zero emissions.