List of Military Nuclear Accidents - 1950s

1950s

• February 13, 1950 – British Columbia, Canada – 1950 British Columbia B-36 crash—non-nuclear detonation of a simulated atomic bomb
  • A USAF B-36 bomber, AF Ser. No. 44-92075, was flying a simulated combat mission from Eielson Air Force Base, near Fairbanks, Alaska, to Carswell Air Force Base in Fort Worth, Texas, carrying one weapon containing a dummy warhead. The warhead contained uranium instead of plutonium. After six hours of flight, the bomber experienced mechanical problems and was forced to shut down three of its six engines at an altitude of 12,000 feet (3,700 m). Fearing that severe weather and icing would jeopardize a safe emergency landing, the weapon was jettisoned over the Pacific Ocean from a height of 8,000 ft (2,400 m). The weapon's high explosives detonated upon impact. All of the sixteen crew members and one passenger were able to parachute from the plane and twelve were subsequently rescued from Princess Royal Island. The Pentagon's summary report does not mention if the weapon was later recovered.
• April 11, 1950 – Albuquerque, New Mexico, USA – Loss and recovery of nuclear materials
  • Three minutes after departure from Kirtland Air Force Base in Albuquerque a USAF B-29 bomber carrying a nuclear weapon, four spare detonators, and a crew of thirteen crashed into a mountain near Manzano Base. The crash resulted in a fire which the New York Times reported as being visible from 15 miles (24 km). The bomb's casing was completely demolished and its high explosives ignited upon contact with the plane's burning fuel. However, according to the Department of Defense, the four spare detonators and all nuclear components were recovered. A nuclear detonation was not possible because, while on board, the weapon's core was not in the weapon for safety reasons. All thirteen crew members died.
• July 13, 1950 – Lebanon, Ohio, USA – Non-nuclear detonation of an atomic bomb
  • USAF B-50 aircraft on a training mission from Biggs Air Force Base with a nuclear weapon flew into the ground resulting in a high explosive detonation, but no nuclear explosion.
• November 10, 1950 – Rivière-du-Loup, Québec, Canada – Non-nuclear detonation of an atomic bomb
  • Returning one of several U.S. Mark 4 nuclear bombs secretly deployed in Canada, a USAF B-50 had engine trouble and jettisoned the weapon at 10,500 feet (3,200 m). The crew set the bomb to self-destruct at 2,500 ft (760 m) and dropped over the St. Lawrence River. The explosion shook area residents and scattered nearly 100 pounds (45 kg) of uranium (U-238) used in the weapon's tamper. The plutonium core ("pit") was not in the bomb at the time.

• March 1, 1954 – Bikini Atoll, Republic of the Marshall Islands (then Trust Territory of the Pacific Islands) – Nuclear test accident
  • During the Castle Bravo test of the first deployable hydrogen bomb, a miscalculation resulted in the explosion being over twice as large as predicted, with a total explosive force of 15 megatons of TNT (63 PJ). Of the total yield, 10 Mt (42 PJ) were from fission of the natural uranium tamper, but those fission reactions were quite dirty, producing a large amount of fallout. Combined with the much larger than expected yield and an unanticipated wind shift radioactive fallout was spread eastward onto the inhabited Rongelap and Rongerik Atolls. These islands were not evacuated before the explosion due to the financial cost involved, but many of the Marshall Islands natives have since suffered from radiation burns and radioactive dusting and also similar fates as the Japanese fishermen and their children and grandchildren have suffered from birth defects and have received little if any compensation from the federal government. A Japanese fishing boat, Daigo Fukuryu Maru/Lucky Dragon, also came into contact with the fallout, which caused many of the crew to take ill with one fatality. The test resulted in an international uproar and reignited Japanese concerns about radiation, especially with regard to the possible contamination of fish. Personal accounts of the Rongelap people can be seen in the documentary Children of Armageddon.
• November 29, 1955 – Idaho, USA – Partial meltdown
  • Operator error led to a partial core meltdown in the experimental EBR-I breeder reactor, resulting in temporarily elevated radioactivity levels in the reactor building and necessitating significant repair.
• March 10, 1956 – Over the Mediterranean Sea – Nuclear weapons lost
  • A USAF B-47 Stratojet, AF Ser. No. 52-534, on a non-stop mission from MacDill Air Force Base to an overseas base descended into a cloud formation at 14,000 feet over the Mediterranean in preparation for an in-air refuelling and vanished while carrying two nuclear weapon cores. The plane was lost while flying through dense clouds, and the cores and other wreckage were never located.
• July 27, 1956 – Lakenheath in Suffolk, UK – Nuclear weapons damaged
  • A USAF B-47 crashed into a storage igloo spreading burning fuel over three Mark 6 nuclear bombs at RAF Lakenheath. A bomb disposal expert stated it was a miracle exposed detonators on one bomb did not fire, which presumably would have released nuclear material into the environment.
• May 22, 1957 – Kirtland AFB in New Mexico, USA – Non-nuclear detonation of an atomic weapon
  • A B-36 ferrying a nuclear weapon from Biggs AFB to Kirtland AFB dropped a nuclear weapon on approach to Kirtland AFB. The weapon impacted the ground 4.5 miles south of the Kirtland control tower and 0.3 miles west of the Sandia Base reservation. The weapon was completely destroyed by the detonation of its high explosive material, creating a crater 12 feet deep and 25 feet in diameter. Radioactive contamination at the crater lip amounted to 0.5 milliroentgen.
• July 28, 1957 – Atlantic Ocean – Two weapons jettisoned and not recovered
  • A USAF C-124 aircraft from Dover Air Force Base, Delaware was carrying three nuclear bombs over the Atlantic Ocean when it experienced a loss of power. The crew jettisoned two nuclear bombs to protect their safety, which were never recovered.
• September 11, 1957 – Rocky Flats Plant, Golden, Colorado, USA – Fire, release of nuclear materials
  • A fire began in a materials handling glove box and spread through the ventilation system into the stack filters at the Rocky Flats weapons mill 27 kilometres (17 mi) from Denver, Colorado. Plutonium and other contaminants were released, but the exact amount of which contaminants is unknown; estimates range from 25 mg to 250 kg.
• 29 September 1957 – Kyshtym, Chelyabinsk Oblast, Russia (then USSR) – Explosion, release of nuclear materials
  • See Kyshtym disaster. A cooling system failure at the Mayak nuclear processing plant resulted in a major explosion and release of radioactive materials. Hundreds of people died and hundreds of thousands were evacuated.
• October 8–12, 1957 – Sellafield, Cumbria, UK – Reactor core fire
  • See Windscale fire. Technicians mistakenly overheated Windscale Pile No. 1 during an annealing process to release Wigner energy from graphite portions of the reactor. Poorly placed temperature sensors indicated the reactor was cooling rather than heating. The excess heat led to the failure of a nuclear cartridge, which in turn allowed uranium and irradiated graphite to react with air. The resulting fire burned for days, damaging a significant portion of the reactor core. About 150 burning fuel cells could not be lifted from the core, but operators succeeded in creating a firebreak by removing nearby fuel cells. An effort to cool the graphite core with water eventually quenched the fire. The reactor had released radioactive gases into the surrounding countryside, primarily in the form of iodine-131 (131I). Milk distribution was banned in a 200-square-mile (520 km2) area around the reactor for several weeks. A 1987 report by the National Radiological Protection Board predicted the accident would cause as many as 33 long-term cancer deaths, although the Medical Research Council Committee concluded that "it is in the highest degree unlikely that any harm has been done to the health of anybody, whether a worker in the Windscale plant or a member of the general public." The reactor that burned was one of two air-cooled graphite-moderated natural uranium reactors at the site used for production of plutonium.

• October 11, 1957 – Homestead Air Force Base, Florida – Nuclear bomb burned after B-47 aircraft accident
  • B-47 aircraft crashed during take-off after a wheel exploded; one nuclear bomb burned in the resulting fire.
• January 31, 1958 – Morocco – Nuclear bomb damaged in crash
  • During a simulated takeoff a wheel casting failure caused the tail of a USAF B-47 carrying an armed nuclear weapon to hit the runway, rupturing a fuel tank and sparking a fire. Some contamination was detected immediately following the accident.
• February 5, 1958 – Savannah, Georgia, USA – Nuclear bomb lost
  • See 1958 Tybee Island mid-air collision. A USAF B-47 bomber jettisoned a Mark 15 Mod 0 nuclear bomb over the Atlantic Ocean after a midair collision with a USAF F-86 Sabre during a simulated combat mission from Homestead Air Force Base, Florida. The F-86's pilot ejected and parachuted to safety. The USAF claimed the B-47 tried landing at Hunter Air Force Base, Georgia three times before the bomb was jettisoned at 7,200 ft (2,200 m) near Tybee Island, Georgia. The B-47 pilot successfully landed in one attempt only after he first jettisoned the bomb. A 3-square-mile (7.8 km2) area near Wassaw Sound was searched for 9 weeks before the search was called off. The bomb was searched for in 2001 and not found. A group of investigators in 2004 claim to have found an underwater object which they think is the bomb.
• March 11, 1958 – Mars Bluff, South Carolina, USA – Non-nuclear detonation of a nuclear bomb
  • A USAF B-47 bomber flying from Hunter Air Force Base in Savannah, Georgia accidentally released an atomic bomb. A home was destroyed and several people injured but the bomb's plutonium core did not explode.
• June 16, 1958 – Oak Ridge, Tennessee, USA – Accidental criticality
  • A supercritical portion of highly enriched uranyl nitrate was allowed to collect in the drum causing a prompt neutron criticality in the C-1 wing of building 9212 at the Oak Ridge National Laboratory Y-12 complex. It is estimated that the reaction produced fissions. Eight employees were in close proximity to the drum during the accident, receiving neutron doses ranging from 30 to 477 rems. No fatalities were reported.
• December 30, 1958 – Los Alamos, New Mexico, USA – Accidental criticality
  • During chemical purification a critical mass of a plutonium solution was accidentally assembled at Los Alamos National Laboratory. A chemical operator named Cecil Kelley died of acute radiation sickness. The March, 1961 Journal of Occupational and Environmental Medicine printed a special supplement medically analyzing this accident. Hand-manipulations of critical assemblies were abandoned as a matter of policy in U.S. federal facilities after this accident.
• July, 1959 – Simi Valley, California, USA – Explosion
  • The Sodium Reactor Experiment was a pioneering nuclear power plant built by Atomics International at the Santa Susana Field Laboratory, nearby Simi Valley, California. The reactor operated from 1957 to 1964. In July 1959, the reactor suffered a serious incident in which the reactor core was damaged causing the controlled release of radioactive gas to the atmosphere.
• November 20, 1959 – Oak Ridge, Tennessee, USA – Explosion
  • A chemical explosion occurred during decontamination of processing machinery in the radiochemical processing plant at Oak Ridge National Laboratory in Tennessee . (Report ORNL-2989, Oak Ridge National Laboratory). The accident resulted in the release of about 15 grams (0.53 oz) of 239Pu.