Science & TechnologyPriority2025-12-04

Kudankulam Unit-3 Receives First Nuclear Fuel

Why focus: Tests GS3 Sci/Tech. VVER-1000 pressurized water reactor mechanics and nuclear criticality concepts are perennial UPSC Sci/Tech targets.

In News

What Happened

On December 4, 2025, the Russian State Atomic Energy Corporation (ROSATOM) delivered the first batch of nuclear fuel for Unit-3 of the Kudankulam Nuclear Power Plant in Tamil Nadu. The fuel, comprising advanced TVS-2M assemblies, was transported via air cargo. This delivery enables the VVER-1000 reactor to begin its initial core loading.

Why It Matters

This delivery marks a critical step toward achieving reactor criticality and synchronizing Unit-3 with India's southern power grid. It also pioneers the use of an 18-month refueling cycle from launch, significantly reducing reactor downtime and boosting India's transition to stable, zero-emission baseload power.

Background

History & Context

The Kudankulam project was born from an Inter-Governmental Agreement (IGA) signed in November 1988 between Indian Prime Minister Rajiv Gandhi and Soviet leader Mikhail Gorbachev. Progress stalled for a decade due to the collapse of the Soviet Union and objections from the United States regarding the 1992 guidelines of the Nuclear Suppliers Group (NSG). The project was revived via a supplementary agreement in June 1998, with construction on Units 1 and 2 beginning in 2002. A subsequent IGA in December 2008 cleared the path for additional reactors, including Unit-3. Progress faced legal hurdles, notably a 2012 Supreme Court petition regarding the Civil Liability for Nuclear Damage (CLND) Act, 2010, but the court upheld the project. Construction of Unit-3 finally began in June 2017.

What Changed

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Fuel Cycle Duration: BEFORE, earlier VVER-1000 reactors operated on a standard 12-month refueling cycle. NOW, Unit-3 will be the first VVER-1000 globally to commence operations with an extended 18-month cycle from its initial launch.
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Fuel Assembly Technology: BEFORE, standard fuel assemblies were utilized in early VVER reactors. NOW, advanced TVS-2M fuel assemblies are loaded, featuring a more rigid structure, higher uranium mass, and next-generation anti-debris filters.
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Commissioning Status: BEFORE, Unit-3 was restricted to civil construction, pipeline laying, and equipment installation. NOW, the arrival of nuclear fuel initiates the pre-commissioning phase, allowing for open-reactor safety testing and eventual criticality.
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Liability Resolution: BEFORE, foreign reactor construction faced delays due to ambiguities in supplier liability under Section 17 of the CLND Act. NOW, the operationalization of the India Nuclear Insurance Pool (INIP) and bilateral protocols signed in December 2024 have streamlined cooperation.

What Did NOT Change

Despite the advanced fuel design, the core reactor technology remains the AES-92 VVER-1000 pressurized water reactor, rather than the newer VVER-1200 model planned for future phases. Additionally, the plant remains completely dependent on imported Low Enriched Uranium (LEU) from Russia, as India's domestic natural uranium is reserved for its indigenous heavy water reactors.

Prelims Angle

NCERT Connection

In Class 12 Physics, Chapter 13 (Nuclei), the concept of 'Nuclear Fission' and the 'multiplication factor' (K) in controlled chain reactions is explained. The loading of TVS-2M fuel is the physical precursor to achieving 'reactor criticality' (where K = 1). Because VVER-1000 is a light water reactor, it requires Low Enriched Uranium (LEU) with a higher percentage of Uranium-235 than natural uranium. This enrichment compensates for neutron absorption by the light water moderator, sustaining the chain reaction over an extended 18-month cycle.

Common Misconceptions

✗ All nuclear reactors in India, including those at Kudankulam, run on domestically sourced natural uranium.

✓ While India's indigenous Pressurized Heavy Water Reactors (PHWRs) use natural uranium, the Russian-built VVER-1000 reactors at Kudankulam are Light Water Reactors (LWRs) that strictly require imported Low Enriched Uranium (LEU).

Students often generalize India's three-stage nuclear program, which is heavily based on natural uranium and heavy water, to every reactor operating within the country.

✗ Kudankulam Unit-3 represents an upgrade to the latest VVER-1200 reactor technology.

✓ Unit-3 utilizes the exact same VVER-1000 (AES-92) reactor design as Units 1 and 2. The VVER-1200 technology is only proposed for the unbuilt Phase 4 (Units 7 and 8).

Recent media discussions about Rosatom exporting newer VVER-1200s globally often blur with the ongoing, legacy construction phases in Tamil Nadu.

Practice Questions

Q1

How Many Correct

Consider the following statements regarding the Kudankulam Nuclear Power Plant (KNPP): 1. The VVER-1000 reactors at KNPP utilize natural uranium as fuel and light water as both coolant and moderator. 2. Unit-3 of KNPP will be the first VVER-1000 reactor globally to commence operations with an 18-month refueling cycle from its initial launch. 3. The TVS-2M fuel assemblies supplied by Rosatom enable an extended operational cycle due to a higher uranium mass and advanced anti-debris filters. How many of the statements given above are correct?

Q2

Match the Following

Match List I (Nuclear Technology/Fuel Concept) with List II (Application/Characteristic): List I: A. PHWR B. VVER-1000 C. TVS-2M D. LEU List II: 1. Light water acts as both coolant and moderator 2. Advanced fuel assembly featuring a rigid structure 3. Heavy water acts as both coolant and moderator 4. Enriched U-235 fraction typically required for LWRs Select the correct answer using the code below:

Q3

Assertion & Reason

Assertion (A): The delivery of TVS-2M nuclear fuel assemblies allows Kudankulam Unit-3 to operate on an extended 18-month refueling cycle rather than the standard 12-month cycle. Reason (R): The TVS-2M fuel assemblies utilize Highly Enriched Uranium (HEU) which takes longer to undergo complete fission. Select the correct answer using the code given below:

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