Nuclear mishaps

Submarines and Ships

Some of the following incidents involve the discharge of radioactive coolant water by ships and submarines. While water from the primary coolant system stays radioactive for only a few seconds, it picks up bits of cobalt, chromium and other elements (from rusting pipes and the reactor) which remain radioactive for years. In realization of this fact, the U.S. Navy has curtailed its previously frequent practice of dumping coolant at sea.

18 April 1959
An experimental sodium-cooled reactor utilized aboard the USS Seawolf, the U.S.’s second nuclear submarine, was scuttled in 9,000 feet of water off the Delaware/Maryland coast in a stainless steel containment vessel. The reactor was plagued by persistent leaks in its steam system (caused by the corrosive nature of the sodium) and was later replaced with a more conventional model. The reactor is estimated to have contained 33,000 curies of radioactivity and is likely the largest single radioactive object ever dumped deliberately into the ocean. Subsequent attempts to locate the reactor proved to be futile.

October 1959
One man was killed and another three were seriously burned in the explosion and fire of a prototype reactor for the USS Triton at the Navy’s training center in West Milton, New York. The Navy stated, “The explosion…was completely unrelated to the reactor or any of its principal auxiliary systems,” but sources familiar with the operation claim that the high-pressure air flask which exploded was utilized to operate a critical back-up system in the event of a reactor emergency.

The USS Theodore Roosvelt was contaminated when radioactive waste from its demineralization system, blew back onton the ship after an attempt to dispose of the material at sea. This happened on other occasions as well with other ships (for example, the USS Guardfish in 1975).

10 April 1963
The nuclear submarine Thresher imploded during a test dive east of Boston, killing all 129 men aboard.

5 December 1965
This write-up is drawn from the US Nuclear Weapons Accidents page at
An A-4E Skyhawk strike aircraft carrying a nuclear weapon rolled off an elevator on the U.S. aircraft carrier Ticonderoga and fell into the sea. Because the bomb was lost at a depth of approximately 16,000 feet, Pentagon officials feared that intense water pressure could have caused the B-43 hydrogen bomb to explode. It is still unknown whether an explosion did occur. The pilot, aircraft, and weapon were lost.
The Pentagon claimed that the bomb was lost “500 miles away from land.” However, it was later revealed that the aircraft and nuclear weapon sank only miles from the Japanese island chain of Ryukyu. Several factors contributed to the Pentagon’s secretiveness. The USS Ticonderoga was returning from a mission off North Vietnam; confirming that the carrier had nuclear weapons aboard would document their introduction into the Vietnam War. Furthermore, Japan’s anti-nuclear law prohibited the introduction of atomic weapons into its territory, and U.S. military bases in Japan are not exempt from this law. Thus, confirming that the USS Ticonderoga carried nuclear weapons would signify U.S. violation of its military agreements with Japan. The carrier was headed to Yokosuka, Japan, and disclosure of the accident in the mid-1980s caused a strain in U.S.-Japanese relations.

Radioactive coolant water may have been released by the USS Swordfish, which was moored at the time in Sasebo Harbor in Japan. According to one source, the incident was alleged by activists but a nearby Japanese government vessel failed to detect any such radiation leak. The purported incident was protested bitterly by the Japanese, with Premier Eisaku Sate warning that U.S. nuclear ships would no longer be allowed to call at Japanese ports unless their safety could be guaranteed.

22 May 1968
The U.S.S. Scorpion, a nuclear-powered attack submarine carrying two Mark 45 ASTOR torpedoes with nuclear warheads, sank mysteriously on this day. It was eventually photographed lying on the bottom of the ocean, where all ninety-nine of its crew were lost. Details of the accident remained classified until November 1993, when a Navy report detailing the incident was made public. The report suggested that a malfunction in one of Scorpion’s torpedoes could have caused the sinking, but evidence from subsequent dives to the location suggest that this was not the culprit.

14 January 1969
A series of explosions aboard the nuclear aircraft carrier Enterprise left 17 dead and 85 injured.

16 May 1969
The U.S.S. Guitarro, a $50 million nuclear submarine undergoing final fitting in San Francisco Bay, sank to the bottom as water poured into a forward compartment. A House Armed Services subcommittee later found the Navy guilty of “inexcusable carelessness” in connection with the event.

12 December 1971
Five hundred gallons of radioactive coolant water spilled into the Thames River near New London, Connecticut as it was being transferred from the submarine Dace to the sub tender Fulton.

October-November 1975
The USS Proteus, a disabled submarine tender, discharged significant amounts of radioactive coolant water into Guam’s Apra Harbor. A geiger counter check of the harbor water near two public beaches measured 100 millirems/hour, fifty times the allowable dose.

22 May 1978
Up to 500 gallons of radioactive water was released when a valve was mistakenly opened aboard the USS Puffer near Puget Sound in Washington.

November 1992
Due to a valve failure, the nuclear-powered USS Long Beach leaked 109 gallons of radioactive cooling water over a 44-day period while docked at San Diego Naval Station. An additional 50 gallons had leaked out there the previous April and May. The San Diego Union reported that coolant had also been released at Pearl Harbor (Hawaii) and Indian Island (Washington). U.S. Navy officials insist that the level of radiation posed no threat, and that a “very small amount of valve leakage that is unavoidable and occurs on all ships is well understood, controlled and accounted for.”


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