Chennai: A significant milestone has been achieved in the 1000 MW Unit-3 of the Kudankulam Nuclear Power Project (KKNPP) in Tamil Nadu with the successful commencement of ‘Spillage to Open Reactor”, signifying the start of individual functional testing of primary system equipment, marking a critical step towards commissioning of the plant.
The Nuclear Power Corporation of India Limited (NPCIL) in an update said this significant commissioning milestone in KKNPP Unit-3 was achieved on Aril 25, 2026.
With the first two units already commissioned, it said the Light Water Reactors (LWRs) project, comprising the remaining four units, including 2 x 1000 MW Unit-3 and was being constructed in the southern coastal Tirunelveli district of Tamil Nadu in technical cooperation with Russian Federation under the framework of the Inter-Governmental Agreement (IGA) signed between Russian Federation and India.
The NPCIL said the “Spillage to Open Reactor”, an important phase in Nuclear Power Plant (NPP) commissioning, involved flushing of safety system and Main Coolant Pipelines (MCP) using light water to ensure cleanliness of the systems for further commissoning activities.
The flushing operation was carried out by operating the safety system pumps from the Main Control Room, in a controlled, sequential manner to maintain system integrity and to achieve the required technical parameters towards clean condtions as per design requirements.
The milestone signifies the start of individual functional testing of primary system equipment and piping in accordance with design requirements, marking a critical step towards commissioning of the plant.
NPCIL Chairman and Managing Director B C Pathak inaugurated the commence of “Spillage to Open Reactor” in the presence of N.Novikov, Director for Indian Projects, Atomstroyexport (ASE) and other senior officials.
It said presently, the KKNPP Units 1 and 2 (2 x 1000 MW) are operating at the site and have so far generated about 121 Billion Units (BUs) of clean electricity, thereby avoiding release of about 104 Million Tonnes of CO2 (Carbon di-oxide) equivalent into the envrionment.
While the first Unit of 1000 MW (VVER model) attained the first criticality on July 13, 2013 and was connected to the grid on October 22, 2013, leading to commencement of commercial operation on December 31, 2014, the Unit-2 attaned criticality on July 10, 2016 and was connected to the grid on August 29, 2016 and the commercial operations began on March 31, 2017.
The ground-breaking ceremony for construction of third and fourth units was performed on February 17, 2016 and the Atomic Energy Regulatory Board (AERB) authorised the first pour of concrete on June 19, 2017.
The construction of the third and fourth units started on June 29, 2017 and the AERB granted excavation permit for Unit 5 and 6 in November 14, 2018 and concerete pour begun in 2020. Construction of Units-5 and 6 commenced onJune 29, 2021.
In Unit-3, some of the major milestones like construction of Inner Containment (IC) dome, Concreting of Outer Containment (OC) dome, Main Coolant Pipeline welding, charging of 230 KV Gas Insulated Switchgear etc. are completed. In December 2025, Rosatom delivered the first batches of fuel to the plant, to be loaded into the core of the third power unit of the site. The TVS-2M fuel gas been designed for a 18 month fuel cycle and the pre-commissioning activities also began at the Unit-3 site in late 2025.
The Unit-4 (1000 MW) was at an advanced stage of construction and the construction of Inner Containment Dome and erection of Nuclear Steam Supply system (NSSS) was completed.
Further Units -5 and 6 (2 x 1000 MW) are at different stages of cosntruction and are planned to be commissioned progressively.
Upon completion of these projects, the Kudankulam site would have a total installed capacity of 6000 MW.
The NPCIL reiterates its commitment to maintaining the highest standards of nuclear safety, qualityand environmental protection, while advancing towards achieving India’s clean enrgy goals in line with Nuclear Energy Mission for Viksit Bharat.
