As it became known to “Kommersant”, as one of the causes of the tragedy at the nuclear deep-water station (ACS) of the AC-31 is considered a short circuit in one of the switchboards. This could cause the cable braid or transformer oil to ignite, and the ventilation carried smoke through the compartments. Most of the hydronauts, according to the source of “Kommersant”, rested at this time and did not have time to use personal protective equipment. As a result, only a five-person watch of the last of a day survived — they were able to localize the spread of fire and raise the station.
According to a source close to the Hydronauts detachment, “Kommersant”, the emergency at the AS-31 occurred at about 9 pm on Monday. The station at that time was carrying out combat missions in the Northern Fleet test range located in the area of the exit from the Kola Bay to the Barents Sea. At the same time, the sailors were serving according to the routine routine: at 19 o'clock Moscow time, the third shift of hydronauts was supposed to have supper, and at 20:00, the watch was replaced at the central post AS-31: their place is taken by the last shift in the day, which is supposed to manage the station until midnight. Thus, most of the personnel of the AS-31 on Monday evening was supposed to be in the so-called “residential” compartment of the station, separated from the service compartments and the central post by special bulkheads.
At that moment, according to another source of “Kommersant”, a short circuit allegedly occurred in one of the numerous AS-31 electrical distribution panels located in the compartments. The boat uses a standard voltage of 380 volts, but some devices use currents of up to 1000 amperes (for comparison, the current in a city apartment is limited to 32 or even 25 amps).
With a large current, a short circuit in the shields, according to sources of “Kommersant”, causes not just a flash with a flash, but rather resembles a small explosion, capable of destroying the shield itself and even contusion of the nearby specialists.
According to experts, as a result of the circuit, the cable sheathing or transformer oil could have ignited, and the station's ventilation system smoke that appeared in connection with this, apparently, smashed into compartments.
Because of the incident, poisonous products of combustion began to enter other compartments, and the hydronauts, as their colleagues believe, could react to the danger too late.
The duty watch may be a little late with the sealing of the compartment, and the rest of the shift - with the inclusion of portable breathing apparatus. According to the charter, every submariner is obliged to keep this device at all times, allowing him to stay in a smoke-filled room for about 20 minutes, with himself. During this time, the hydronaut, as conceived by the manufacturer, even in the most difficult situation, will be able to find one of the fittings of a stationary respiratory system that supplies fresh air from balloon stocks and connect to it. However, the sailors for some reason did not take advantage of either system.
According to the Kommersant source, over the 45 years of the existence of the Hydronauts Detachment (military unit 45707), not a single serious accident that led to human casualties and accidents occurred with their stations, therefore, the depth researchers had no real experience in fighting fires.
Meanwhile, in his opinion, the smoke from the burning cable sheath is able to put a person out of action in literally seconds. “For a loss of consciousness in a closed room, just a few breaths are enough,” the submariner is convinced.
Thus, within a few minutes after the beginning of the smoke, only the duty shift at the central post continued to struggle for the survivability of the boat. These four officers and one civilian specialist organized the lifting of the AU-31, which in the current situation was difficult to do. According to Kommersant’s sources, the depth of the Barents Sea in the area of the landfill for stations like АС-31 is quite small - within 200 m. However, the ascent procedure with all operations takes about ten minutes. These minutes, obviously, turned out to be fatal for 14 hydronauts who received severe poisonings from the combustion products.
The remaining five survived and even saved the station entrusted to them. The duty watch was able to safely lift the AS-31 to the surface, after which the station was brought to the dock at the hydronaut base in the Deer Guba.
On Wednesday, July 3, in Severomorsk, Defense Minister Sergei Shoigu reported that the crew had fought for the survival of the deep-water apparatus to the last, and it was thanks to one of the hydronauts, 2nd rank captain Dmitry Solovyov, who himself was killed, a civilian specialist was rescued. Mr. Shoigu promised to present all the dead sailors to state awards (two of them, captains of the 1st rank, Denis Dolonsky and Nikolay Filin, were already Heroes of Russia), as well as assist their families.