‘Core catcher’ in a nuclear plant

The Moscow-based Rosatom State Corporation Engineering Division has installed a core melt localisation device (CMLD) or “core catcher” at Tamil Nadu’s Kudankulam Nuclear Power Plant (KKNPP).

What is the protective “core catcher” device?

• 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 melt down.
• 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.
• The device has improved seismic resistance, hydro-dynamic and shock strength as well as equipped with flood protection and simplified installation and assembly technology.

Its construct

• 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 aluminium oxide granules).
• The core catcher is filled with a ceramic mixture also including ferric oxide and aluminium oxide, called ‘sacrificial material’.
• The sacrificial material prevents the corium from trickling through and also acts as a cooling mechanism.

Installation

• The core catcher device is installed at the bottom of the nuclear station’s protective shell.
• It is designed to save the latter as well as exude radioactive emission in the environment in case of a serious accident.