Cherenkov radiation glowing in the core of the advancedTest Reactor. 

        Cherenkov radiation is electromagnetic radiation emitted when a charged particle such as an electron passes through an insulator at a constant speed greater than the speed of light in that medium. The characteristic "blue glow" of nuclear reactors is due to Cherenkov radiation.It is named after Russian scientist Pavel Alekseyevich Cherenkov,the 1958 Nobel prize winner. The name" Apsara" is given to the first nuclear reactor of India by Jawaharlal Nehru when he likened the blue Cerenkov radiation to the beauty of the Apsaras