At Least Twenty Deaths Reported On Russian Submarine

Russian media sources are reporting that 20 sailors and shipyard workers were killed during "testing" after a "fire extinguishing system unexpectedly went off". From a BBC report on the incident:

Russian Pacific Fleet spokesman Igor Dygalo said both sailors and shipyard workers died in the incident, which occurred during sea trials.
He said the submarine itself had not been damaged and there had been no radiation leaks...
...The submarine, whose name and class have not been revealed, has been ordered to suspend sea trials and return to port in the far eastern Primorye territory, Capt Dygalo said...
...There were 208 people on board at the time, 81 of whom were servicemen.
Twenty-one injured people have been evacuated from the submarine, sources at the fleet said.
Reports say the incident occurred in the nose of the vessel. The nuclear reactor, which is in the stern, was not affected.

The first linked article says that the sub is "now moving to a temporary base. It is being escorted by an anti-submarine ship and a rescue vessel."

The number of civilians on board indicates that the BBC report is correct that this seems to have happened during sea trials. I mentioned late last month that the Akula-II submarine RFS Nerpa, rumored to be heading to India on lease after shakedown, was out on sea trials. As I doubt that the Russians would have enough shipyard resources to have two boats out on sea trials in the Pacific simultaneously, I'd guess that this is the affected boat. This AFP article on the new incident reaches a similar conclusion.

Russian submarines operate with much smaller crews than American boats, so I would imagine that they rely more on automatic fire suppression systems than our boats do. (The Russians have lost at least one submarine to fire relatively recently, so I imagine they have a special interest in designing robust fire extinguishing systems.) Most naval fire suppression systems would probably use either CO2 or a Halon-like chemical, both of which would displace oxygen in the environment. While you have to take everything the Russians say with a grain of salt, I could imagine the fire suppression system emptying its contents into the torpedo room, and the inexperienced crew following their fire procedures and isolating all compartments; this could have resulted in the O2 concentration in the Torpedo Compartment dropping below that required to support life. In any event, this is quite a tragic accident. Our thoughts are with the families and shipmates of the fallen mariners.

Update 1951 08 Nov: This Reuters article is reporting that the Russian media is quoting a shipyard source as saying that the submarine involved is the Nerpa.

Update 2053 08 Nov: Russian Navy Blog has a translation of a Novosti report that discusses the types of fire suppression systems used on Russian submarines. Applicable excerpt:

The chemical system is designed to extinguish any type of fire in a space except for fuel and ammunition fires and consists of a fire supression station located in all compartments except the reactor compartment. The reactor compartment is covered by stations located in the 5th and 7th compartments.
The extinguishing agent is Halon 114B2. The system can deliver three shots of extinguishing agent to each space. The system can be activated remotely from the central command post or from a local control panel as well as manually from the station in the compartment.

I could imagine that if the whole Halon storage tank emptied into one compartment due to a failed valve/pipe, rather than operating in a fixed number of short bursts, that could result in a Halon concentration high enough to drive the oxygen levels too low in the breathing space --especially if the compartment was isolated so as not to spread the Halon to the remainder of the ship.

Update 0730 09 Nov: An update from the CNN website:

The victims died of poisoning from Freon gas that was released Saturday when the fire-extinguishing system accidentally turned on, said Sergei Markin, an official with Russia's top investigative agency.
His agency has launched a probe into the accident, which Markin said will focus on what activated the firefighting system. He suggested there could be possible violations of operating rules, which points to human error...
...The submarine returned to Bolshoi Kamen, a military shipyard and a navy base near Vladivostok, state-run Rossiya television said.
Dygalo said the deaths and injuries were due to the "unsanctioned activation" of the firefighting system in the two sections of the submarine closest to the bow.
Seventeen civilians and three seamen died in the accident and 21 others were hospitalized after being evacuated to a destroyer that brought them to shore, Markin said in a statement, revising earlier casualty figures.

Hopefully Sergei Markin was misquoted, or at least his investigators know the difference between Freon and Halon. And the Navy spokesman quick announcement of "unsanctioned activation" indicates that they're looking to go the scapegoat route, or anything to take blame away from bad construction or design. My guess is they'll blame one of the dead shipyard workers; it'll be especially good for Russia if one of the dead was an Indian rider, 'cause that'll give them someone non-Russian to blame.

Update 0955 09 Nov: Based on this translation at Russian Navy Blog of a commentary on the navy.ru site, I'm starting to think that the Russians don't have a separate word for "Halon", and use "Freon" to describe both the refrigerant and fire suppression haloalkanes. My Russian is a little rusty, but I picked up the word "фреона" in the Russian article ("freona" would be the English transliteration), which clearly means "Freon".

Update 1255 09 Nov: This AP article has some good updates, including the information (Russian-supplied, so evaluate accordingly) that the victims were found to have "Freon" in their lungs. This CSM article, on the other hand, confuses AFFF with chemical extinguishers, so probably isn't worth spending your time reading.

Update 1437 10 Nov: Here's an AP follow-up with some theories from some Russians about what might have happened.

Update 1551 11 Nov: Some of the survivors speak.