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The Russian Northern Fleet Nuclear submarine accidents.

8.2 Reactor Accidents

The most serious accident in which radioactivity is released is the meltdown of the reactor core on board the submarine.  This is called a nuclear accident.  There have been a number of both major and more minor incidents involving naval reactors.  These accidents can be grouped into three categories according to the degree of severity:

1. Nuclear accidents
2. Reactor accidents
8.2 Nuclear accidents

Nuclear accidents are classified either as "loss of control" (loss of regulation) accidents in which an uncontrolled chain reaction may occur, or as "loss of coolant accidents".  There have been ten nuclear accidents in the entire period that Soviet nuclear submarines have been in operation, one of which occurred in 1970 during the construction of K-329, a vessel of the Charlie-I class.  There were two incidents during refueling operations on K-11 and K-431, another during repairs of a naval reactor at the shipyard (K-140), one during modifications of the submarine (K-222), four during operations at sea, and one during reactor shut down (K-314).  Two of the accidents occurred on Pacific Fleet submarines, seven at the Northern Fleet, and one shipbuilding yard in Nizhny Novogorod.
Once again, the control rods had not been secured, and when the reactor lid was raised, there were releases of steam and a fire broke out.  There are no data on radioactive contamination levels or radiation exposure of the personnel.  The reactor was finally retired and replaced.

K-27
On May 24, 1968, the nuclear submarine K-27 was out at sea.  During sea trials, the nuclear reactor had operated at reduced power, and on May 24, power inexplicably suddenly dropped.  Attempts by the crew to restore power levels failed.  Simultaneously, gamma radiation in the reactor compartment increased to 150 R/h.  Radioactive gases were released to the reactor compartment from the safety buffertank, and radiation on board the submarine increased.  The reactor was shut down, and approximately 20% of the fuel assemblies were damaged.  The incident was caused by problems in the cooling of the reactor core.  The entire submarine was scuttled in the Kara Sea in 1981.

K-140
In August 1968, - Yankee-class nuclear submarine K-140 was in the naval yard in Severodvinsk for repairs.  On August 27, an uncontrolled increase of the reactor's power occurred following work to upgrade the vessel.  One of the reactors started up automatically when the control rods were raised to a higher position.  Power increased to 18 times its normal amount, while pressure and temperature levels in the reactor increased to four times the normal amount.  The automatic start-up of the reactor was caused by the incorrect installation of the control rod electrical cables and by operator error.  Radiation levels aboard the vessel deteriorated.

K-429
In 1970, while the brand new - Charlie class submarine K-329 lay in harbour at the shipbuilding yard Krasnoe Sormovo in Nizhny Novgorod, there was an uncontolled start up of the ship's reactor.  This led to a fire and the release of radioactivity.

K-19
The first nuclear accident to occur on a Russian submarine was on the Northern Fleet's ballistic missile submarine K-19(Project 658-Hotel class).  On July 4, 1961, during exercises in the North Atlantic, a leak developed in an inaccessible part of the submarine K-19's primary cooling circuit.  The leak was specifically located to a pipe regulating the pressure within the primary cooling circuit.  The leak caused a sudden drop in pressure, setting off the reactor emergency systems.

To prevent overheating of the reactor, superfluous heat must be removed, and this is done by continually circulating coolant through the reactor.  There was no built-in system for supplying coolant to the primary circuit, and it was feared that an uncontrolled chain reaction might start.  An improvised system to supply coolant to the reactor was devised.  This required officers and midshipmen to work for extended periods under radioactive onditions in the more remote areas of the reactorcompartment as they attended to the leak in the primary circuit.  The radiation in this case came from noxious gases and steam.  All of the crew were exposed to substantial doses of radiation, and eight men died of acute radiation sickness after having undergone doses of 50 to 60 Sv (5000 - 6000 rem).  The crew was evacuated to a diesel submarine, and K-19 was towed home to base on the Kola Peninsula.

K-11
The second nuclear accident to occur was in February 1965 aboard the November class submarine K-11.  The submarine lay in dock at the naval yard in Severodvinsk and work was underway to remove reactor core (Operation No. 1)  On February 6, the reactor lid was opened, and the following day, the lid was lifted without havng first secured the control rods.  Releases of radioactive steam were detected with an abrupt deterioration of conditions.  Radiation monitors were going off scale, and all personnel were withdrawn.  No work was done on the submarine over the course of the next five days while the specialists tried todiscover the reason for the problem.

On September 30, 1980, the submarine K-222 wasat the factory in Severodvinsk due for a thorough reactor check.  During the course of work, the submarine;s crew left forlunch leaving the factory personnel on oard the vessel.  As a result of a breach in the pertinent procedural instructions, power was sent through the safety rod mechanisms without the controls also being engaged.  Following a failure in the automatic equipment, there was an uncontrolled raising of the control rods with a subsequent uncontrolled start up of the reactor.  As a result of this, the reactor core was damaged.

K-123

On August 8, 1982, while on duty in the Barents Sea, there was a release of liquid metal coolant from the reactor of the Project 705 - Alfa class submarine K-123.  The accident was caused by a leak in the steam generator.  Approximately two tons of metal alloy leaked into the reactor compartment, irreparably damaging the reactor such that it had to be replaced.  It took nine years to repair the submarine.

 

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