Date
|
Location
|
Type
|
Description
|
February 13, 1950
|
British Columbia
|
Loss of nuclear bomb/non-nuclear detonation of nuclear bomb
|
A simulated nuclear bomb containing TNT and uranium, but without the
fissile core
needed to create a nuclear explosion, was proactively dumped in the Pacific Ocean after a
Convair B-36
bomber's engines caught fire during a test of its ability to carry nuclear payloads. The crew reported releasing the weapon out of concern for the amount of TNT inside, alone, before they bailed out of the aircraft. The bomber eventually crashed at an unknown location in Canada. Four years later the wreckage was found and searched, but no bomb was found. The weapon was briefly thought to have been located by a civilian diver in 2016 near
Pitt Island
but this was subsequently found not to be the case.
[5]
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 conventional explosives and natural uranium but lacked the
fissile core
of an actual weapon. 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 with a bright flash visible. 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
.
[6]
The accident was categorized as a
Broken Arrow
, that is an accident involving a nuclear weapon but which does not present a risk of war.
[7]
|
April 11, 1950
|
Albuquerque, New Mexico
, US
|
Loss and recovery of nuclear materials
|
Three minutes after departure from
Kirtland Air Force Base
in Albuquerque a USAF
Boeing B-29 Superfortress
carrying a nuclear weapon (without a
fissile core
), four spare detonators, and a crew of thirteen crashed into a mountain near
Manzano Base
. The crash resulted in a fire that
The New York Times
reported as being visible from 15 miles (24 km). The bomb's casing was 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. All thirteen crew members died.
[6]
|
July 13, 1950
|
Lebanon
, Ohio, US
|
Non-nuclear detonation of an atomic bomb
|
A USAF
B-50
aircraft on a training mission from
Biggs Air Force Base
with a nuclear weapon (without a
nuclear core
) flew into the ground resulting in a high-explosive detonation, but no nuclear explosion.
[8]
|
August 5, 1950
|
Fairfield-Suisun AFB
, California, US
|
Non-nuclear detonation of an atomic bomb
|
A USAF B-29 bomber AF Ser. No. 44-87651 with a
Mark 4 nuclear bomb
(without a
fissile core
) on board, flying to
Guam
experienced malfunctions with two propellers and with landing gear retraction during take-off and crashed while attempting an emergency landing at Fairfield Suisun-AFB. In the resulting fire, the bomb's high-explosive material exploded, killing nineteen people from the crew and rescue personnel.
Brigadier General
Robert F. Travis
, command pilot of the bomber, was among the dead.
[9]
|
November 10, 1950
|
Riviere-du-Loup
,
Quebec
, 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. No
fissile core
was installed in the bomb.
[10]
|
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 spread into unexpected areas. A Japanese
fishing boat
, the
Daigo Fukuryu Maru/Lucky Dragon
, came into contact with the fallout, which caused many of the crew to become ill, with one fatality. The fallout spread eastward onto the inhabited
Rongelap
and
Rongerik Atolls
. These islands were not evacuated before the explosion due to the unanticipated fallout zone and 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 have received little, if any, compensation from the
federal government
.
[11]
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
, US
|
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.
[12]
[13]
|
March 10, 1956
|
Over the
Mediterranean Sea
|
Two capsules of nuclear weapons material in carrying cases
|
A USAF
B-47 Stratojet
,
AF Ser. No. 52-534
, on a non-stop mission from
MacDill Air Force Base
, Florida, to an overseas base descended into a cloud formation at 14,000 feet over the Mediterranean in preparation for an in-air refueling and vanished while transporting two capsules of
nuclear weapons
material in carrying cases; a nuclear detonation was not possible.
[14]
A French news agency reported that the plane had exploded in the air Northeast of
Saidia
, in French Morocco in the same general location of its last known position. The plane was lost while flying through dense clouds, and the cores and other wreckage were never located.
[15]
[16]
[17]
|
July 27, 1956
|
RAF 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.
[18]
|
May 22, 1957
|
Kirtland AFB
in
New Mexico
, US
|
Non-nuclear detonation of a
Mark 17
thermonuclear bomb
[19]
|
A B-36 ferrying a nuclear weapon from
Biggs AFB
to
Kirtland AFB
dropped a nuclear weapon on approach to Kirtland. The weapon struck 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 (3.7 m) deep and 25 feet (7.62 m) in diameter. Radioactive contamination at the crater lip amounted to 0.5
milliroentgen
.
[17]
|
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 weapons and one nuclear capsule aboard the aircraft at the time. Nuclear components were not installed in the weapons. While flying over the Atlantic Ocean, the aircraft experienced a loss of power. For their own safety, the crew jettisoned two bombs which were never recovered.
[8]
|
September 11, 1957
|
Rocky Flats Plant
,
Golden
, Colorado, US
|
Fire, release of nuclear materials
|
A fire began in a theoretically fireproof area inside the
plutonium
processing building, in a
glovebox
used to handle radioactive materials, igniting the combustible rubber gloves and
plexiglas
windows of the box. The fire quickly spread to the plutonium as various safety features failed. The fire spread through the ventilation system as the containment ability of the facility became compromised, with plumes of radioactive smoke sent high into the outside air. The fire raged inside the building for 13 hours over the night of the 11th & 12th before firefighters could finally extinguish it. In the aftermath,
Department of Energy
officials, and the
Dow Chemical
officials who ran the facility, did not admit the extent of the catastrophe, or the radiation danger, to local officials or the media. Knowledge of the extent of the damage and contamination was kept from the public for years. After the fire, plutonium was detected near a school 12 miles (19 km) away and around
Denver
17 miles (27 km) away. An independent group of scientists conducting off-site testing 13 years later found plutonium contamination in areas in nearby
Rocky Flats
to be 400 to 1,500 times higher than normal, higher than any ever recorded near any urban area, including
Nagasaki
. The
Atomic Energy Commission
then conducted its own off-site study, and that study confirmed plutonium contamination as far as 30 miles (48 km) from the plant.
[20]
[21]
[22]
[23]
|
September 29, 1957
|
Kyshtym
,
Chelyabinsk Oblast
,
Russian Soviet Federative Socialist Republic
,
USSR
(now
Russian Federation
)
|
Explosion, release of nuclear materials
|
A
cooling system
failure
at the
Mayak
nuclear processing plant resulted in a major explosion and release of radioactive materials. A large area was subjected to
radioactive contamination
and thousands of local inhabitants were evacuated.
[24]
|
October 8?12, 1957
|
Sellafield
, Cumbria, UK
|
Reactor core 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 removed from the core, but operators succeeded in creating a
firebreak
by removing nearby fuel cells. An effort to cool the graphite core with water and the switching off of the air cooling system eventually quenched the fire. The reactor had released radioactive gases into the surrounding countryside, primarily in the form of
iodine-131
(
131
I). Milk distribution was banned in a 200-square-mile (520 km
2
) area around the reactor for several weeks. A 1987 report by the
National Radiological Protection Board
predicted the accident would cause as many as 100 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
.
[25]
[26]
[27]
A 2007 study concluded that because the actual amount of radiation released in the fire could be double the previous estimates, and that the radioactive plume actually travelled further east, there were 100 to 240 cancer fatalities in the long term as a result of the fire.
[28]
[29]
[30]
|
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.
[31]
|
January 31, 1958
|
Sidi Slimane Air Base
, Morocco
|
Nuclear bomb damaged in crash
[31]
|
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.
[31]
[32]
[33]
|
February 5, 1958
|
Savannah
, Georgia, US
|
Unarmed nuclear bomb lost
|
A USAF B-47 bomber jettisoned a
Mark 15 Mod 0 nuclear bomb
(the nuclear capsule was not aboard the aircraft; the bomb contained a simulated 150-pound (68 kg) cap made of lead)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.
[34]
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 km
2
) area near
Wassaw Sound
was searched for nine weeks before the search was called off.
|
February 28, 1958
|
Greenham Common US Base
,
Newbury
, England
|
|
A
B-47E
of the
310th Bomb Wing
developed problems shortly after takeoff and jettisoned its two 1,700 gallon external fuel tanks. They missed their designated safe impact area, and one hit a hangar while the other struck the ground 65 feet (20 m) behind a parked B-47E. The parked plane, which was fuelled, had a pilot on board, and was carrying a 1.1 megaton (4.6 PJ)
B28 nuclear bomb
, was engulfed by flames. The conflagration took sixteen hours and over a million gallons of water to extinguish, partly because of the magnesium alloys used in the aircraft. Although two men were killed and eight injured, the US and UK governments kept the accident secret: as late as 1985, the British government claimed that a taxiing aircraft had struck a parked one and that no fire was involved.
|
March 11, 1958
|
Mars Bluff
, South Carolina
|
Non-nuclear detonation of a nuclear bomb
|
A USAF
B-47E bomber
, number 53-1876A, was flying from
Hunter Air Force Base
in
Savannah
, Georgia, to England in a formation of four B-47s on a top-secret mission called
Operation Snow Flurry
to perform a mock bombing exercise. The flight navigator/bombardier was checking the locking harness on the massive (7,600 pounds (3,447 kg))
Mark 6 nuclear bomb
when he accidentally pushed the emergency release lever. The bomb fell on the bomb-bay doors, smashing them open and going into a 15,000 feet (4,572 m) free fall. The high-explosive detonator went off after it hit the ground 6.5
miles
east
of
Florence
, South Carolina, in
Mars Bluff
, creating a 70 feet (21 m) wide crater, 30 feet (9 m) deep.
[35]
A nearby house was destroyed and several people were injured.
[34]
: 136?137
[36]
A nuclear detonation was not possible because, while on board, the weapon's
core
was not in the weapon for safety reasons.
|
June 16, 1958
|
Oak Ridge, Tennessee
, US
|
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
Y-12
complex. It is estimated that the reaction produced 1.3 × 10
18
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.
[37]
|
November 4, 1958
|
Dyess Air Force Base
, Texas, US
|
Non-nuclear detonation of a nuclear bomb
|
A USAF
B-47 bomber
developed a fire shortly after take-off and went down with a nuclear weapon on board from an altitude of 1,500 ft (460 m). The detonation of the high explosive material in the bomb created a crater 6 feet (1.8 m) deep and 35 feet (10.7 m) in diameter. Three crew members escaped, and one was killed.
[38]
|
November 26, 1958
|
Chennault Air Force Base
,
Louisiana
, US
|
Non-nuclear detonation of a nuclear bomb
|
A USAF
B-47 bomber
with a nuclear weapon on board developed a fire while on the ground. The aircraft wreckage and the site of the accident were contaminated after a limited explosion of non-nuclear material.
[39]
|
December 30, 1958
|
Los Alamos, New Mexico
, US
|
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 E. Kelley
died of
acute radiation sickness
. The March 1961
Journal of Occupational and Environmental Medicine
printed a special supplement medically analyzing this accident. Hand manipulation of critical assemblies was abandoned as a matter of policy in U.S. federal facilities after this accident.
[37]
|
January 18, 1959
|
Osan Air Base
, South Korea
|
Nuclear weapon on fire
|
A parked USAF
F-100C Super Sabre
, loaded with a nuclear weapon, developed a fire after its external fuel tanks were dropped and exploded during a practice alert. The resulting fire was put out in seven minutes and there was no nuclear explosion.
[40]
When originally disclosed in 1980, the location was originally identified as at a base in the Pacific region. In 2016, the newspaper
Asahi Shimbun
reported that the location of the accident was
Osan Air Base
.
[41]
|
July 6, 1959
|
Barksdale AFB
, Louisiana, US
|
Limited contamination
|
A USAF
C-124
transporting three
Mark 39 Mod 2
sealed-pit nuclear weapons crashed and burned down during take-off. The high explosives did not detonate, but one weapon was completely destroyed by the fire, and the other two suffered heat damage and
tritium
leakage. The wreckage area experienced limited contamination.
[42]
|
September 25, 1959
|
Off
Whidbey Island
,
Washington
, US
|
Lost nuclear weapon casing
|
A U.S. Navy
P5M
antisubmarine
aircraft patrolling out of NAS Whidbey Island with an unarmed Mark 90
nuclear depth charge
casing on board
crash-landed
in the Pacific Ocean, about 100 miles (160 km) west of the Washington-Oregon border.
[43]
The casing was not recovered.
[44]
|
October 15, 1959
|
Hardinsburg, Kentucky
, US
|
Nuclear weapon partially damaged
|
After both planes took off from
Columbus Air Force Base
in
Mississippi
, a USAF
B-52F-100-BO
(No. 57-036), with two nuclear weapons
collided
at 32,000 feet (9,754 m) with a
KC-135
refueling aircraft
(No. 57-1513), during a
refueling procedure
near Hardinsburg, Kentucky. Both planes crashed killing eight crew members. One unarmed nuclear weapon was partially damaged, but no contamination resulted.
[45]
|
November 20, 1959
|
Oak Ridge, Tennessee
, US
|
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
239
Pu
.
|