India built N-sub in Kalpakkam under codename 'PRP'

The secrecy attached to the development of the indigenous nuclear submarine project is almost legendary.
What’s little known is the extent to which the Indian N-establishment went to conceal the research not only from the public but also large sections of the scientific community within the Department of Atomic Energy (DAE).
For almost nine years, most staff working at the Indira Gandhi Centre for Atomic Research (IGCAR) in Kalpakkam believed the Plutonium Recycle Project (PRP) in the complex was used only for that purpose, that is recycling plutonium.
But with the launch of INS Arihant on July 25, top DAE officials have finally begun to lift the veil and reveal that they were actually building the core (nuclear reactor and propulsion systems) of the submarine as well as the land-based version of the hull of the indigenous vessel, which served as the technology demonstrator of the main vessel, within the PRP unit. For those in the know, even the term ‘PRP’ denoted the N-sub.
Sunday marked the commemoration of the fifth year since the project attained criticality at the PRP site with a controlled N-chain reaction. Ahead of a briefing by Atomic Energy Commission (AEC) chairman Anil Kakodkar, a team of scientists escorted journalists around a gigantic, dark grey-coloured hull of a submarine, which was the land-based version of the hull of Arihant. ‘‘It is a 1:1 model of the submersible. Everything was simulated here before being built on the main submarine at Vishakapatnam,’’ a scientist explained.
Although the idea of an indigenous nuke sub was conceived by Raja Ramanna over two decades back and research undertaken at Barc in Trombay, work on the PRP site in Kalpakkam began in 1999.
Criticality was attained on November 11, 2003, with the land-based version running on a light water reactor, scientists revealed. But Arihant remained shrouded in mystery. Three years later, on September 22, 2006, when the reactor was operational there was still silence.
In fact, going by dates provided now, the first hints of the project’s success came only a year later on September 11, 2007, when former AEC chief P K Iyengar said at a public meeting, ‘‘Indian scientists are capable of making light water reactors. We are constructing one at Kalpakkam for a submarine.’’
Defending the need for stealth, an IGCAR official explianed, “We had to maintain secrecy as this was a project of high national secrecy and security and we did not want other nations to know about this.’’