Nuclear reactor (Atomic pile) : In nuclear reactor, fission is performed in in a controlled fashion to release energy. Fuels like U 235 & Pu 239 ar fissioned and with the help of moderators, a sustained chain reaction is achieved. First nuclear reactor is at Calder Hall in UK by Fermi in 1956.

Moderators are used to slowdown fast neutrons released in U 235 fission. eg - Graphite, Heavy water (Plants in Talchar in Orissa and Punjab), Beryllium etc.

First nuclear reactor in India - 1 MW Apsara reactor. First power reactor in India - Tarapur, Maharashtra, 1972. 2.7 % of the total power in India comes from nuclear reactors (3000 MW). India's power reactors are at Narrora (UP), Kota (440 MW, Rajastan), Kalpakkam (440 MW), Tarapur (1000 MW).

CIR (Cirus) : Reactor with Canadian collaboration at BARC (Bhabha Atomic Research Centre - India's prime nuclear research establishment), Mumbai. It is a 40 MW research reactor producing U 233 & Pu 239.

Chernobyl reactor in Russia leaked by accident in 26 April 1986.