Nuclear power is the fifth-largest source of electricity in India after coal, gas, hydroelectricity and wind power. As of March 2018, India has 22 nuclear reactors in operation in 7 nuclear power plants, with a total installed capacity of 6,780 MW.Nuclear power produced a total of 35 TWh and supplied 3.22% of Indian electricity in 2017.7 more reactors are under construction with a combined generation capacity of 4,300 MW.
Apsara is the oldest of India's research reactors. The reactor was designed by the Bhabha Atomic Research Center (BARC) and built with assistance from the United Kingdom (which also provided the initial fuel supply consisting of 80 percent enriched uranium). India's and Asia's first nuclear reactor, Apsara reached criticality at 3:45 p.m on 4 August 1956 and was inaugurated by Prime Minister Nehru on 20 January 1957. Apsara is a light water swimming pool-type reactor with a maximum power output of one megawatt thermal (MWt). The reactor burns enriched uranium in the form of aluminum alloyed curved plates. Fuel for the reactor is supplied under contract from the United Kingdom, provided that the fuel is safeguarded. The reactor itself is not under International Atomic Energy Agency safeguards. The Apsara reactor is utilized for various experiments including neutron activation analysis, radiation damage studies, forensic research, neutron radiography, and shielding experiments. The reactor is also used for research and the production of radioisotopes.