CIRUS is a 40 MW-thermal heavy-water-moderated, light-water-cooled, natural-uranium fueled reactor of the same design as the Canadian NRX reactor. Canada provided financial assistance for the construction of the reactor; heavy water was supplied by the United States. The reactor first became critical in July 1960 and fully operational - in 1963. In 1997-2003 it underwent an extended refurbishment. The reactor was used to produce plutonium for the first India's nuclear test in 1974. IPFM estimates that CIRUS produced from 165 to 270 kg of plutonium (this includes plutonium in the fuel still to be reprocessed).
India shuts down CIRUS reactor
A few minutes before the end of the year 2010, India shut down its CIRUS reactor located at the Bhabha Atomic Research Center in Mumbay. The reactor was reported to have been shut down by 24:00 (18:30 UTC) on December 31, 2010.