India’s first indigenous nuclear submarine may not ensure deterrence, to be available for patrol for one-fifth of lifespan.

India’s first indigenous nuclear submarine, INS Arihant (S2), which made its first foray into the sea on Monday for mandatory trials ahead of induction into the Navy, may in effect be a limited utility submarine, if not just a technology demonstrator.

The ballistic missile nuclear submarine (SSBN), said to add the third dimension of the nuclear triad by giving India the vital survivable second-strike capability, falls short of ensuring credible minimum deterrence, sources said.

Worse, the capacity of the reactor suggests that Arihant will hardly be available for operational patrol even for one-fifth of its lifespan, having to spend great amounts of time on transit to patrol areas.

“The effective fuel inventory of the submarine reactor is insufficient for longer duration deployment of the vessel far away from Indian shores, as it will necessitate frequent fuel changes that are time-consuming,” said a Navy veteran, who was previously associated with the project.

Fuel change in a submarine reactor, he said is a protracted and cumbersome process requiring the hull of the submarine to be cut open. The nuclear attack submarine (SSN) that India operates on a 10-year lease from Russia, INS Chakra (S1), for instance, is said to have reactor with a longer effective core life, granting it more time on patrol.”

The Arihant project — the first of the three SSBNs built by India under its ATV [Advanced Technology Vessel] programme under the supervision the Prime Minister’s Office and involving agencies and establishments such as the DRDO, the Department of Atomic Energy, the Submarine Design Group of the Directorate of Naval Design, besides companies such as L&T — had been under wraps for decades until its high-voltage launch in 2009.

The 83-MW uranium reactor, developed by the Bhabha Atomic Research Centre (BARC) with generous support from Russia, went critical in August last year. The submarine should have entered service in 2012, as originally planned. As the sea-acceptance trials that have just begun are slated to take at least nine months if everything goes as planned and without hiccups, Arihant will at best be inducted in 2016.

“This is our first home-made submarine reactor, so the Nuclear Safety Regulatory Authority was cautious in its approach and didn’t want to give the go-ahead for sea trials without a thorough check,” said an official explaining the delay.

The submarine arm of the Navy had previously expressed its reservations over the long “turnaround time” and frequent “fuel change cycles” of the Arihant class of submarines.

Official sources told The Hindu that the sea-acceptance trials would last at least nine months, if not more. “As the submarine with its onboard crew has to remain submerged for about 90 days at a stretch during deployments, there will be a lot of environment checks carried out during the sea trials.”

Meanwhile, work on the second Arihant-class submarine, INS Aridhaman (S3), is already behind schedule and nowhere near launch.

Arihant is said to have been built at a cost of $2.9 billion. “But that is not the unit cost of the submarine. The material cost apart, it includes the money spent on setting up facilities such as the submarine reactor complex in Kalpakkam, the Defence Machinery and Design Establishment in Hyderabad and the Ship Building Centre in Vizag. However, to amortise the amount, India should be building a series of nuclear submarines,” a source said.