Poor India. Another major accident on INS Chakra "II"ex-Nerpa, the Russian SSN 10 year leased to India.
For the latest, 2020 accident see this Indian source:
"...The 'early' return of the INS Chakra [for complete repairs] had triggered a buzz as she was the only nuclear-powered attack submarine in the Indian Navy. Attack submarines are meant primarily to destroy enemy surface ships and submarines. The Chakra was from a Russian class of submarines that NATO codenamed the Akula (shark in Russian). Before being handed over to the Indian Navy, the Chakra was known as the Nerpa in Russian service.
The INS Chakra was also used to train personnel who would work on the indigenously built nuclear submarines of the Indian Navy.
On [June 9, 2021], Russian state news agency TASS reported the early return of the INS Chakra was necessitated due to an explosion on board the vessel in the spring of 2020, which damaged both its hulls. The Chakra, like many other Russian-designed submarines of its era, is a 'double-hulled' submarine, with a pressure inner hull and a lighter outer hull to allow for more buoyancy and capacity to absorb damage in the event of being hit by a torpedo or mine.
The Russian language website of TASS quoted a source in the Russian "military-industrial complex" as saying, "The explosion of a high-pressure air cylinder on the Chakra submarine... occurred in the spring of 2020." The report claimed the high-pressure air cylinder was located between the two hulls. In addition to damage to the hulls, the explosion also damaged "electronic weapons and hydro-acoustic equipment"...."