Nuclear submarine was damaged after water entered its propulsion chamber

Indigenous nuclear submarine INS Arihant has suffered major damage due to ''human error'' and has not sailed now for more than 10 months, say sources in the Navy.

Arihant is the most important platform within India’s nuclear triad covering land-air-sea modes.

Arihant’s propulsion compartment was damaged after water entered it, according to details available with The Hindu. A naval source said water rushed in as a hatch on the rear side was left open by mistake while it was at harbour.

The Ministry of Defence did not respond to questions from The Hindu.

The accident

Since the accident, the submarine, built under the Advanced Technology Vessel project (ATV), has been undergoing repairs and clean up, the sources said.

Besides other repair work, many pipes had to be cut open and replaced. “Cleaning up” is a laborious task in a nuclear submarine, the naval source said.

The Arihant issue rose soon after INS Chakra, the Nerpa class nuclear submarine leased from Russia, was reported to have suffered damage to its sonar domes while entering the Visakhapatnam harbour in early October. However, INS Chakra has only a peripheral role in the nuclear triad, for both training and escorting, and Arihant is the one that will carry nuclear missiles.

The absence of Arihant from operations came to the political leadership’s attention during the India-China military standoff at Doklam. Whenever such faceoff takes place, countries carry out precautionary advance deployment of submarine assets. Arihant (Code name S2) came into the limelight on July 26, 2009, when Gursharan Kaur, wife of Prime Minister Manmohan Singh, broke a coconut to mark its launch in Visakhapatnam.

After that, the submarine was towed to an enclosed pier for extensive harbour trials from the dry docks at Ship Building Centre, away from public view. Arihant was quietly commissioned into service in August 2016 and its induction is still not officially acknowledged. It is powered by an 83 MW pressurised light-water reactor with enriched uranium.

Senior naval sources maintain that Arihant has faced problems from the start. Initial delays could be just teething trouble, glitches at various stages of getting the reactor to go critical and during harbour trials; major differences between the Russian-supplied design and indigenous fabrication are said to have left many issues unaddressed satisfactorily.

Top gun for second strike

Arihant , the country's only operational Ship Submersible Ballistic Nuclear (SSBN) asset, can stay undetected deep underwater for long periods, range far and wide. It is the most dependable platform for a second strike, given the country's “no first use” on nuclear weapons. The other options, land-based and air-launched, are easier to detect.

The submarine is manned by 100 men with extensive training from the School for Advanced Underwater Warfare in Visakhapatnam and further hands-on training on INS Chakra.

The second ballistic missile submarine, Arighat, was launched on November 19 for sea trials. The launch was kept a low-profile event, attended by Defence Minister Nirmala Sitharaman and senior Navy officers.

A high-profile launch, to be attended by the Prime Minister, was put off.

Key to nuclear triad

Arihant and other nuclear launch platforms are operationally handled by the Strategic Forces Command, and report to the Nuclear Command Authority chaired by the Prime Minister.

However, the over 100 nuclear warheads are not mated with missiles or bombs and remain in civilian custody of the Atomic Energy Department and the Defence Research and Development Organisation.

Ambitious plan to build SSBN fleet

India has an ambitious plan to build a SSBN fleet, comprising five Arihant class vessels.

The naval sources say the plan hinges on Arihant’s success. It has taken 30 years to build it, at a high cost. “It was initially estimated to cost about ₹3000 crore for three boats — now the cost of Arihant itself seems to have gone over ₹14,000 crore,” a former high-ranking naval officer said.

The Eastern Naval Command plans to operate its nuclear sub fleet from an independent Naval Operational Alternative Base (NOAB) being constructed on 5,000 acres at Rambilli, for direct access to the sea. The base is located about 50 km from Visakhapatnam, and jetties are under construction.

(With Sumit Bhattacharjee in Visakhapatnam)