Sources said the nuclear reactor on Arihant was made critical Friday night and the submarine was on its own power now.
They said activation of nuclear reactor was "a major landmark" in making the submarine operational.
Sources added the submarine would undergo extensive sea trials before being made operational.
INS Arihant has been undergoing trials at navy's submarine base in Visakhapatnam, Andhra Pradesh.
--IANS (Posted on 10-08-2013)