Nuclear Weapons 331 - The Soviets Blew Up A Reactor While Refueling A Nuclear Submarine
In my last blog post, I talked about an accident that sank a Soviet nuclear submarine in the Bay of Biscay which is north of Spain in1970. Today I am going to talk about another accident involving a Soviet nuclear submarine in 1985.
By 1985, the U.S. had stationed nuclear missiles in countries around the Soviet Union. The Soviet Union had not such option in their desire to threaten the U.S. so they turned to nuclear cruise missile submarines. The Echo I class carried six P-5 Pyatyorka nuclear land attack cruise missiles while the Echo II class carried eight of the cruise missiles. The P-5s could be equipped with either a two hundred or a three hundred and fifty kiloton nuclear warhead. They had a range of three hundred and ten miles. They had a circular error probability of 1.86 miles meaning that at least half of the missiles aimed at a particular target would land within a circle around the target that was 1.86 miles in diameter.
The P-5 missiles were kept in big horizontal silos attached to the sides of the deck of the submarine. When a P-5 was going to be launched, the submarine had to surface and deploy a tracking radar systems before launching the P-5. The missile depended on the targeting information being relayed in real time from the targeting radar system. There were problems with the system such as the vulnerability of the command system to jamming. The fact that the submarine had to remain on the surface until the missile reached its target also made it vulnerable to detection. Eventually, the P-5 missiles were replaced with the P-6 version which had its own radar targeting system.
The arrival of the P-6 extended the life of the Echo II class of Soviet submarines. In 1985, the Echo II class K-431 was twenty years old but was still in use. It was powered by two pressurized water reactors that provided sixty thousand shipboard horsepower. In early August, refueling of the K-431 reactors began at Chazhma Bay Soviet Naval facility.
On August 10th, the reactor lid with new fuel rods installed was lifted into the air. A beam was placed on the lid to prevent it from being lifted beyond the safe position. Unfortunately, the beam was not placed correctly, and the reactor lid was lifted too high. This caused the starboard reactor to achieve critical mass followed by a chain reaction and then an explosion.
The explosion blew out the twelve-ton reactor lid with the attached fuel rods and ripped open the pressure hull of the reactor. This totally destroyed the core of the reactor and killed ten men standing near the reactor. A plume of radioactive fallout two thousand feet wide and two miles long moved downwind along the Dunay Peninsula. Debris and Cobalt 60 was thrown over the docks nearby.
The scene of the accident was seriously contaminated with radioactivity. There was some gamma radiation, but the main danger came from the iodine-131, an isotope known to cause cancer. Forty-nine members of the emergency crew showed symptoms of radiation sickness.
Fortunately, the fuel rods being loaded into the K-431 reactor core were a new type, created especially for the naval engine. If they had been loaded with the old type of fuel rod used in land based nuclear power reactors, the fallout would have contained high levels of other dangerous radioactive isotopes including strontium-90 and cesium-137. The K-431 was towed to Pavlovsk Bay and operations soon resumed at the Naval facilities at Chazhma Bay which is still contaminated with radioactive materials to this day.
K-431 Soviet Submarine:
