The reactor, designed by the Bhabha Atomic Research Centre (BARC) and built with assistance from the United Kingdom at Trombay, first went critical on August 4, 1956.
Subsequently, it was then shut down after almost 54 years in 2010.
"Apsara is one of the oldest research reactors of BARC and we wanted to recommission it. We were working on revamping the entire reactor and we hope that in 2018, it will be completely operational," Associate Director, Reactor Group at BARC, Sujay Bhattacharya told PTI here.
It was also used for research and production of radio-isotopes.
"This light water swimming pool-type reactor with a maximum power output of 1 MW is now being upgraded to 2 MW with low-enriched uranium fuel," he said.