Relevance: Mains: G.S paper III: Science and tech
Why in news?
- The Moscow-based Rosatom State Corporation Engineering Division announced that it had installed a core melt localisation device (CMLD) or “core catcher” at Unit 3 of Tamil Nadu’s Kudankulam Nuclear Power Plant (KKNPP).
Corium:
- 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. The corium so formed can remain radioactive for several decades, even centuries.
- 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.
- In the past, meltdown accidents have occurred at Chernobyl in Russia in 1986 and at Fukushima in Japan in 2011.
Core Catcher:
- Core melt localisation device (CMLD) or a core catcher device is designed to localise and cool the molten core material in case of a meltdown accident.
- According to the Rosatom website, 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.
- 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, according to the press release.