The Moscow-based Rosatom State Corporation Engineering Division had installed a core melt localization device (CMLD) or “core catcher” at Unit 3 of Tamil Nadu’s Kudankulam Nuclear Power Plant (KKNPP).
About the Kudankulam Nuclear Power Project (KKNPP)-
- KKNPP is being implemented at Kudankulam situated in Thirunelveli district, Tamil Nadu.
- Under the KKNPP project, it was planned to set up six nuclear power plants each of 1,000 MW, in phases with Pressurized Water Reactor (Voda Voda Energo Reactor) technology.
- In the first phase, it was planned to construct Units I and II.
- The project is being implemented in technical collaboration with the Government of the Russian Federation (Russian Federation).
- An Inter-Governmental Agreement (IGA) was signed between the GoI and the erstwhile Union of Soviet Socialist Republics (USSR) in the year 1988 to implement the project.
- KKNPP is based on the technology of pressurized water reactor, cooled and moderated by light water.
- Its core containing nuclear fuel is located inside a pressure vessel.
- The reactor is located inside an airtight primary containment building which is surrounded by a secondary containment. The reactor has steam generators in each loop.
- Each Unit of KKNPP i.e. Unit I (1,000 MW) and Unit II (1,000 MW) consists of four Primary Coolant System loops transferring the heat energy from the reactor to the Steam Generators (SGs). The steam produced in the SGs is fed to the Turbine Generator to generate electricity.
About Core Catcher-
- The core catcher is a cone-shaped metal structure that weighs about 800 tonnes.
- The structure is double-walled, with the gap between the two walls filled with FAOG (ferric and aluminum oxide granules).
- The device is designed to localize and cool the molten core material in case of a meltdown accident.
- The core catcher is filled with a ceramic mixture also including ferric oxide and aluminum oxide, called ‘sacrificial material’.
- The sacrificial material prevents the corium from trickling through and also acts as a cooling mechanism.
- The core catcher device is installed at the bottom of the nuclear station’s protective shell and is designed to save the latter as well as exude radioactive emission in the environment in case of a serious accident.
- The device has improved seismic resistance, hydro-dynamic, and shock strength as well as equipped with flood protection and simplified installation and assembly technology.
- In 2011, the device was first installed at the Tianwan nuclear power plant in China, which is of Russian design.
- In 2018, a 200-tonne core catcher was installed Rooppur 1 Nuclear Power Plant in Bangladesh.
- At Kudankulam, it has been installed in the design position under the reactor pit of Unit 3 and has been adapted to the relevant site conditions and safety requirements.
Therefore, Core Catcher will prevent meltdown accident. Molten core material, or corium, is lava-like material that gets formed in the core of a nuclear reactor in the event of a meltdown accident. Such an accident occurs when the nuclear fission reaction taking place inside a reactor is not sufficiently cooled, and the buildup of heat causes fuel rods to meltdown. The corium so formed can remain radioactive for several decades, even centuries. In the past, meltdown accidents have occurred at Chernobyl in Russia in 1986 and at Fukushima in Japan in 2011.