List of nuclear accidents
This is a list of notable accidents involving nuclear material. In some cases, these incidents involve people being injured or killed due to the release of radioactive contamination
. Most incidents involve accidental releases that have caused contamination, but had no other immediate effects. Some incidents only had the potential to release radioactive material, and are included because of the tensions such incidents caused (collisions between nuclear-powered submarines
, for instance). Due to government secrecy
, it is difficult to determine with certainty the extent of some events listed below or, occasionally, whether they happened at all.
- September 2, 1944 – A container of uranium hexafluoride exploded in the Oak Ridge National Laboratory transfer room, killing Peter N. Bragg, Jr and Douglas P. Meigs and injuring three others. A steam pipe exploded and the incoming water vapor combined with the uranium compound to form hydrogen fluoride, a dangerous acid, which was inhaled by all five. Bragg and Meigs died soon after from whole-body acid burns. 
- August 21, 1945 – Harry K. Daghlian, Jr, working at Los Alamos Omega site, accidentally created a supercritical mass when he dropped a tungsten carbide brick onto a plutonium core. He quickly removed the piece, but was fatally irradiated in the incident, dying September 15.
- May 21, 1946 – Canadian physicist Louis Slotin manually assembled a critical mass of plutonium while demonstrating his technique to visiting scientists at Los Alamos, New Mexico. The device consisted of two half-spheres of beryllium-covered plutonium, which can be moved together slowly to measure the criticality. Normally the device would be operated by machinery, but Slotin distrusted the devices and manually operated it by holding the upper sphere with his thumb inserted in a hole in the top like a bowling ball. In most experiments, a number of washers would be arranged to prevent the two hemispheres from falling together completely, but he had removed them. In order to slowly bring the two pieces together, he rested one edge on the lower sphere and rotated a slot screwdriver between the other edge to control the separation. At one point, the screwdriver slipped and the assembly went critical while he was still holding onto it. None of the seven observers received a lethal dose, but Slotin died on the 30th from massive radiation poisoning, with an estimated dose of 1000 rad, or 10 gray (Gy). This was dramatized in the movie Fat Man and Little Boy, except that the movie placed the event before the Trinity test—in reality, a device that Slotin had helped to assemble.
First notice of radioactivity in the fallout was raised seven hours after the detonation when fallout reached Rongerik atoll. A group of 28 service members working at the weather station on Rongerik, 160 miles (260 km) east of Bikini, began evacuating about 30 hours after the explosion.
- February 13, 1950 – A B-36 en route from Alaska to perform a simulated bombing run on Californian cities developed multiple engine fires due to carburetor icing in the extreme cold. The crew dumped the single Mark IV bomb (carrying the depleted uranium tamper but not its plutonium core) off British Columbia then abandoned ship. The high explosives detonated on impact.
- April 11, 1950 – A B-29 bomber crashed three minutes after takeoff from Kirtland Air Force Base in New Mexico. A nuclear bomb with no detonators installed is on board at the time of the crash; its casing was destroyed, but the weapon did not go off.
- November 10, 1950 – A B-50 returning one of several US Mark IV bombs secretly deployed in Canada had engine trouble and jettisoned the weapon at 10,500 feet. The bomb, carrying the depleted uranium tamper but not its plutonium core ("pit"), was set to self-destruct at 2500' and dropped over the St. Lawrence River off Rivière du Loup, Quebec. The explosion shook area residents and scattered nearly 100 pounds (45 kg) of uranium.
- December 12, 1952 – The first serious nuclear disaster occurred at the NRX reactor in Chalk River, Canada. A massive power excursion destroyed the core, resulting in a partial meltdown. A series of hydrogen gas explosions threw a four-ton gasholder dome four feet into the air, where it jammed in the superstructure. Thousands of curies of fission products were released into the atmosphere, and a million gallons of radioactively contaminated water was pumped out of the basement into shallow trenches not far from the Ottawa River. The core was buried. Jimmy Carter, then a nuclear engineer in the US Navy, was among the cleanup crew.
- April 26, 1953 – A class of radiochemistry students at Rensselaer Polytechnic Institute in Troy, New York observed high levels of radiation. Ground radiation averaged about 50 Ci/km² some puddles register 270 nCi/L, nearly 3000 times the United States Atomic Energy Commission limit. The radiation is traced to fallout from the Simon test, which had occurred two days previously. There is an even worse rainout in June.
- May 19, 1953 – The United States government detonated the 32-kiloton bomb "Harry" at the Nevada test site. The bomb later gained the name "Dirty Harry" because of the tremendous amount of offsite fallout generated by the bomb.  Winds carried fallout 135 miles (220 km) to St. George, Utah, where residents reported "an oddly metallic sort of taste in the air."  A 1962 AEC report found that "children living in St. George, Utah may have received doses to the thyroid of radioiodine as high as 120 to 440 rads." (1.2 to 4.4 Gy) 
- 1954 – The submarine USS Seawolf (SSN-575) scuttled an experimental sodium-cooled reactor in 9,000 ft (2,700 m) of water off the Delaware/Maryland coast. At 33 kCi it's likely the most radioactive single object ever deliberately sunk, and had not been retrieved as of 2004. The reactor had problems with corrosion from the coolant, and was replaced by a conventional light-water reactor.
- March 1, 1954 – During the early morning of March 1st, a Japanese Fishing boat, the Fukuryu Maru, or "Lucky Dragon," and its crew witnessed what they believed to be the sun rising to the west of them as they sailed in the Pacific Ocean. In fact, they were witnessing the 12 megaton detonation of the hydrogen bomb "Bravo" at the Bikini Atoll, 85 miles (140 km) away. Four hours later, white ash began to fall like snow onto the boat. Many of the crew members gather the ash into bags as souvenirs. Before the evening was over, the entire crew had become ill. The 23 crew members were hospitalized in Japan and one later died of kidney failure due to radiation exposure. The incident brought a rift in relations between Japan and the United States because the US did not warn Japan or any other country of the bomb's testing, leaving the Lucky Dragon exposed to the fallout. (In partial mitigation, the device yielded about 2½ times what was predicted because of an overlooked reaction; the US expanded its exclusion zones in later tests.) Fallout was enhanced by debris from coral dispersed by the explosion. The US issued an apology and paid 2 million US dollarss in compensation.  Additionally, in the same incident, 64 natives of Rongelap Atoll were exposed for 50 hours to fallout that produced a whole-body radiation dose of 175rem, 28 residents of Rongerik atoll were exposed to doses of about 78rem before being permanently evacuated, 18 residents of Alininae atoll were exposed to 68rem for about 50 hours, and 157 residents of Utirik atoll were exposed to 14rem for about 55 to 75 hours.
March 10, 1956 – Somewhere en route to a rendezvous with an Air Force tanker flying over the Mediterranean Sea, a B-47 from MacDill Air Force Base in Tampa, Florida disappeared without a trace. The plane was carrying two nuclear capsules at the time of the incident.
July 2, 1956 – Nine individuals were injured after two explosions destroyed a portion of Sylvania Electric Products' Metallurgy Atomic Research Center in Bayside, Queens, New York.
July 26, 1956 – A US B-47 practicing landings at Lakenheath Air Base in Suffolk, England skidded into a nuclear storage mound with three Mark VI bombs inside. The resulting fire was extinguished without sparking explosions, although a secret cable by US 7th Air Division General James Walsh in Britain remarked that the bombs were "knocked about," and, "Preliminary exam by bomb disposal officer says a miracle that one Mark Six with exposed detonators sheared didn't go." However, exposure to external heat, or even accidental ignition of explosives used to trigger nuclear reactions is widely believed to be insufficient to trigger a nuclear reaction, because nuclear bomb triggers usually require precisely synchronized detonation of an explosive lens that simultaneously forces radionuclides radially inwards into fissionable proximity. Accidental ignition of high-explosive triggers would most likely result in a blast that deflects off of the hard radioactive metal pit. An aircraft fuel fire is no more capable of igniting an nuclear explosion than a stick of dynamite is adequate as a trigger for a nuclear bomb.
March, 1957– Employees of a Houston company licensed by the Atomic Energy Commission to encapsulate sources for radiographic cameras opened a can containing 10 pellets of Iridium192. Using a jewelers lathe isolated inside a Plexiglass box and 33 inches of concrete, the two operators discovered that two of the pellets were powderized. Some of the dust escaped the containment facility. One of the workers, dressed in street clothes left the area, while another remained, working in lab clothes and wearing a respirator. The contamination was not discovered by company personnel for a month, and not by the AEC for about five weeks. The incident was reported in Look Magazine in 1961. By then, at least eight private homes and seven automobiles had been contaminated by the spreading dust. Only the two workers were found to have suffered radiation burns. The widely reported incident, in the early days of AEC civilian licensing administration, reportedly led to families of the workers being alienated from neighbors who feared contamination. Reports released by the Mayo Clinic four years after the accident found few of the radiological injuries claimed in widespread press reports, but failed to assuage public fears that followed publicity of the accident.
May 22, 1957 – Land grants of University of New Mexico, near Albuquerque, New Mexico: A bomber accidentally dropped a 10-megaton hydrogen bomb. The trigger explosive detonated, creating a 12-foot deep crater 25 feet across. Some radiation was detected.
July 28, 1957 – A C-124 Globemaster with 3 nuclear weapons and a nuclear capsule from Dover Air Force Base lost power in two engines. Two weapons were jettisoned somewhere off Rehobeth, Delaware and Cape May, New Jersey/Wildwood, New Jersey; they were reportedly never found.
1957 – Keleket Co: A capsule of radium salt burst leading to a five-month decontamination that cost US$250,000. The capsule was used to calibrate the radiation-measuring devices produced there.
September 11, 1957 – A major fire at Rocky Flats weapon mill 27 km from Denver began in a glovebox and spread through the ventilation system into the stack filters. Plutonium (among lesser evils) was released, but no one was sure how much; estimates ranged from 25 mg to 250 kg.class="external">[2class="external">[1
September 29, 1957 – Cooling system failure results in a nuclear waste storage tank steam explosion at Mayak, a spent nuclear fuel reprocessing facility near Chelyabinsk, Russia, releasing some 20 MCi and subjecting (by various estimates) 124,000 to 270,000 people to dangerously high levels of radiation. Of these, only 7,500 were evacuated, most of them too late to prevent dangerous levels of exposure. A series of less prominent accidents preceded and followed this meltdown, in addition to a polluted water supply for people remaining in the area. More than 500,000 inhabitants of the region have been exposed to radiation as a result.
October 8–12, 1957 – Windscale Pile No. 1 at Sellafield north of Liverpool, England began an annealing process to release Wigner energy from graphite portions of the reactor. The reactor that burned was one of two air-cooled graphite-moderated natural uranium reactors at the site used for production of plutonium. Technicians mistakenly overheated the reactor pile because poorly placed temperature sensors indicated the reactor was cooling rather than heating, leading to failure of a nuclear cartridge, which allowed uranium and irradiated graphite to react with air. The nuclear fire burned four days, melting and consuming a significant portion of the reactor core. About 150 burning fuel cells could not be lifted from the reactor core, but operators succeeded in creating a fire break by removing nearby fuel cells. A risky effort to cool the graphite core with water eventually quenched the fire. The air-cooled reactor had spewed radioactive gases throughout the surrounding countryside. Milk distribution was banned in a 200 mile² (520 km²) area around the reactor. Over the following years, Pile No. 1 and neighboring Pile No. 2 were shut down, although nuclear decommission work resumed in 1990 and continued at least through 1999. The incident, similar in scale to the Three Mile Island meltdown, was later blamed for dozens of cancer deaths.class="external">[2class="external">[1
January 31, 1958 – A B-47 with a fully-armed nuclear weapon crashes and burns for 7 hours at a US Air Force base, 90 miles (145 km) N.E. of Rabat, Morocco. The Air Force evacuates everyone within 1 mile (1.6 km) of the base. Many vehicles and aircraft are contaminated. However, Moroccan officials are not notified.
February 5, 1958 – A damaged B-47 off the coast of the US state of Georgia, flying near Tybee Island, jettisons a weapon lacking its nuclear core from 7200 feet after attempting to land three times at Hunter Air Force Base. The plane had suffered a collision with an F-86 during simulated combat near Savannah, Georgia, and could not land safely with the heavy bomb on board. The bomb is never recovered.
February 28, 1958 – At a US airbase at Greenham Common, England, a B-47 has a fiery crash. Scientists working for the Atomic Weapons Research Establishment in Aldermaston in 1960 discover high concentrations of radioactive contamination at the base, pointing toward the conclusion that a nuclear warhead was involved in the crash. However, the US government has never confirmed such speculation.
1958 – Unexpected wind shift drops test fallout on Los Angeles, California
1958 – Soviet military reactor near Chelyabinsk releases radioactive dust. 12 villages evacuated.
1958 – In the NRU reactor in Chalk River, Canada, several metallic uranium fuel rods overheat and rupture inside the core. One of the damaged rods catches fire and is torn in two while it is being removed from the core by a robotic crane. As the remote-controlled crane passes overhead carrying the larger portion of the damaged rod, a three-foot (1 m) length of burning uranium fuel breaks off and falls into a shallow maintenance pit. The ventilation system is jammed in the "open" position, thereby contaminating the accessible areas of the building as well as a sizable area downwind from the reactor site. A relay team of scientists and technicians eventually extinguishes the fire by running past the pit at top speed while wearing full protective gear, dumping buckets of wet sand on the burning uranium fuel.
March 11, 1958 – A B-47 from Hunter Air Force Base in Georgia en route to an overseas base drops an unarmed nuclear weapon into the yard of Walter Gregg and his family in Mars Bluff, near Florence, South Carolina. The trigger explodes and destroys Gregg's house, injuring six members of his family. The blast forms a crater 60 feet wide and 30 feet deep. Five houses and a church are also damaged. Residents carry away radioactive pieces of the bomb for souvenirs, which have to be retrieved by an Air Force cleanup crew. Five months later the Air Force pays the Greggs $54,000 of his estimated $300,000 loss.
November 4, 1958 – A B-47 bearing nuclear bombs burns in flight, crashing in Texas.
December 30, 1958 – A critical mass of plutonium solution is accidentally assembled during chemical purification at Los Alamos. The crane operator dies of acute radiation sickness. The March 1961 Journal of Occupational Medicine prints a special supplement medically analyzing this accident. Hand-manipulations of critical assemblies are abandoned as a matter of policy in U.S. federal facilities after this accident.
1959 – A sodium-cooled reactor suffers a partial core meltdown at Santa Susana Field Laboratory near Simi Valley, California.
July 1959 – A small meltdown in the San Fernando Valley releases radiation.
October 1959 – One killed and 3 seriously burned in explosion and fire of prototype reactor for the USS Triton (SSRN/SSN-586) at the United States 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 that exploded was to feed a crucial reactor-problem backup system.
October 15, 1959 – A B-52 with two nuclear bombs collides with a KC-135 tanker and crashes in Kentucky
November 20 1959: A chemical explosion occurred in the radio-chemical processing plant at Oak Ridge Laboratory in Tennessee during decontamination of processing machinery. The explosion caused extensive plutonium contamination to the building, to adjacent streets and to nearby building exteriors. The explosion was theorized to have occurred after hot nitric acid was exposed to decontamination fluids containing phenol that had been left in an evaporator after operators failed to water-wash the equipment clean of decontamination fluids. (Report ORNL-2989, Oak Ridge National Laboratory). Areas that could not be effectively cleaned in the following weeks were painted with bright warning paint or with concrete. Oak Ridge officials began using secondary containment structures for radio-chemical processing facilities following the accident, which resulted in no reported injuries to personnel. The accident resulted in the release of about 15grams of plutonium 239.
- June 7, 1960 – At McGuire Air Force Base in New Egypt, New Jersey, a helium tank explodes and ruptures the tanks of a BOMARC-A cruise missile. The fire melts the missile and plutonium released from the nuclear trigger contaminates the facility and ground water.
- 1961 – The USS Theodore Roosevelt (SSBN-600) attempts to dump the depleted resin from its demineralization system (used to remove dissolved radioactive minerals and particles from the primary coolant loops of submarines). The ship is contaminated when wind blows resin back onto the ship.
The accident was discovered by those outside the reactor building when radiation and thermal alarms alerted fire crews and health physicists, who discovered radiation levels exceeding 200 mR/h hundreds of feet from the reactor building. Emergency crews were at first unable to find either a fire or the workers, but encountered radiation levels as high as 1000 mR/h inside the reactor building. One of the three workers was removed from the building but died a few hours later. The other two bodies remained in the building for several days while hundreds of rescue workers initiated recovery operations. Of those recovery personnel, 22 received radiation exposures in the range of 3 rem to 27 rem, according to 1961 Atomic Energy Commission
- January 3, 1961 – At the National Reactor Testing Station in Idaho Falls, Idaho, the experimental SL-1 reactor had a critical incident with a steam explosion and a severe dispersal of radioactive material, killing three workers at the installation. With the exception of Iodine131, most of the radiation was contained within about a three-acre (12,000 m³) area. Vegetation was contaminated with I131 at levels as high as 100 times background levels as far as 20 miles (30 km) from the reactor. Radio-iodine contaminated vegetation at more than double background levels more than 50 miles (80 km) from the reactor, including about a 50 mile (80 km) stretch along the Snake River near Burley and American Falls. The portable reactor had manually-actuated control rods. Moving a single rod could cause the criticality incident. The rods were known to jam in the lightweight aluminum housing. Some investigators believe that a rod stuck and then suddenly released, causing the criticality incident. Investigators never concluded why the rod had been removed. One worker was found pinned to the ceiling by a control rod, apparently driven by the steam.
reports. The reactor was dismantled and the 13-ton core and pressure vessel was removed several months later.
- January 24, 1961 – A B-52 bomber explodes in mid-air 12 miles (20 km) north of Seymour Johnson Air Force Base, Goldsboro, North Carolina. The incident releases two hydrogen bombs. Five crewmen parachute to safety, but three die. One bomb parachutes down and lands intact. The second plunges into mud. Currently, the area remains fenced and is tested regularly for radiation, although the state says that no radiation above background is present. See: [Broken Arrow: Goldsboro, NC http://www.ibiblio.org/bomb/].
- March 1961 – A B-52 with nuclear weapons crash-lands near Yuba City, California. (The string of such accidents over the past few years prompts President John F. Kennedy to have the weapons' safety interlocks improved.)
- July 4, 1961 – The Soviet Hotel-class K-19 submarine experiences a major accident after a reactor cooling system fails off the coast of Norway. The incident contaminates the crew, parts of the ship, and some of the ballistic missiles carried onboard, and several fatalities result. Reactor core temperatures reach 800 °C, nearly enough to melt the fuel rods, although the crew is able to regain temperature control by using emergency procedures. 
- December 10, 1961 – An underground nuclear test explosion unexpectedly releases clouds of radioactive steam, causing several New Mexico highways to be closed.
- 1962 – Czechoslovakian study proves the uranium mill near Ceske Budejovice has caused the loss of 80% of local cattle by leukemia and deformities. Budweiser (the Czech beer, not the American beer of the same name) gets its hops from the same area.
- April 10, 1963 – The nuclear submarine USS Thresher (SSN-593) sinks east of Boston, Massachusetts with 129 men onboard during sea trials. A year earlier, just before the end of its refit interval, the boat had been abused in a munitions test where it literally tried to approach explosions as closely as possible. The boat was refitted afterward, and sank on its sea trials. In a show of poor planning, the sea trial was conducted where the bottom was below the hull's crush depth. In the yard, destructive tests of a few silver-soldered pipe connections had failed. At the time, nondestructive testing was unknown, and no test records were available. The investigators believed that the sinking was caused by the failure of a major through-hull silver-soldered connection, such as a secondary-loop cooling inlet, and that the reactor and its design was not responsible. The reactor was not recovered.
- May 1963 – Mandan, North Dakota records the highest ever recorded concentration of strontium-90 in milk in the US, as of 2003. It probably originated at the highly-secret Hanford Site.
- January 13, 1964 – A B-52 with two nuclear weapons crashes near Cumberland, Maryland.
- April 21 1964 – A US nuclear-powered navigational satellite failed to reach orbital velocity and reentered the atmosphere 150,000 feet above the Indian Ocean. The satellite's SNAP generator contained 17 kCi of Plutonium-238, which at least partially burned upon reentry. Increased levels of Pu238 was first documented in the stratosphere four months later. About 16 kCi of Pu238 was estimated to have settled into the atmosphere by 1970. The EPA estimated the abortive launch resulted in far less Pu238 contamination to human lungs (0.06 mren) compared to fallout from weapons tests in the 1950s (0.35 mren).
- July 24, 1964 – An accident at a commercial nuclear fuel fabrication facility in Charlestown, Rhode Island leaves one person dead.
- January 1965 – An accident at Lawrence Livermore National Laboratory releases 300 kCi of radioactive material.
- October 1965 – A fire at Rocky Flats exposes a crew of 25 to up to 17 times the legal limit for radiation.
- December 5, 1965 – An A-4E Skyhawk airplane with one B43 nuclear weapon onboard falls off the USS Ticonderoga into 16,200 feet (4.9 km) of water off the coast of Japan. The ship was traveling from Vietnam to Yokosuka, Japan. The plane, pilot, and weapon are never recovered. There is dispute over exactly where the incident took place—the US Defense Department originally stated it took place 500 miles (800 km) off the coast of Japan, but US Navy documents later show it happened about 80 miles (130 km) from the Ryukyu Islands and 200 miles (320 km) from Okinawa. 
- Mid-1960s (date unknown) – The Soviet nuclear-powered icebreaker Lenin experiences a nuclear accident (possibly a meltdown), requiring the ship's reactors to be dumped into the Kara Sea. 
- January 17, 1966 – Near Palomares, Spain during over-ocean in-flight refueling, a B-52 collides with a United States Air Force KC-135 jet tanker. Eight of the eleven crew members are killed. The KC-135's 40,000 gallons of jet fuel burn. Two hydrogen bombs rupture, dispersing radioactive particles over nearby farms. An intact bomb lands near Palomares. The fourth bomb was lost at sea 12 miles (20 km) off the coast. A search involving three months and 12,000 men recover it. During the ensuing cleanup, 1,500 tons of radioactive soil and tomato plants are shipped to a nuclear dump in Aiken, South Carolina. The U.S. settled claims by 522 Palomares residents for $600,000. The town also received a $200,000 desalinization plant.
- September 1966 – Plutonium fire at Livermore
- October 5, 1966 – A sodium cooling system malfunction at the Enrico Fermi demonstration nuclear breeder reactor on the shore of Lake Erie near Monroe, Michigan caused a partial core meltdown. The radiation was contained. This incident was the basis of the controversial polemic We Almost Lost Detroit by John G. Fuller. The reactor core comprised 105 uranium oxide fuel assemblies, made of pins clad with zirconium. The accident was attributed to a piece of zirconium that obstructed a flow-guide in the sodium cooling system. Automatic sensors isolated the reactor building. No personnel were inside at the time. Workers succeeded in manually shutting down the reactor. Two of the 105 fuel assemblies melted during the incident, but no contamination was recorded outside the containment vessel. The 200 mW reactor was returned to full-power operational status in October, 1970.
- 1967 – Livermore leaks plutonium into San Francisco's sewers for three weeks; the city used dried sewage as fertilizer.
- January 22, 1968 – 7 miles (11 km) south of Thule Air Force Base, Greenland, a fire breaks out in the navigator's compartment of a B-52 which crashes, scattering three hydrogen bombs on land and dropping one into the sea. During a cleanup complicated by Greenland's harsh weather, contaminated ice and airplane debris are buried in the U.S. Bomb fragments were recycled by Pantex, in Amarillo, Texas. Danes were outraged by the event because Greenland is a Danish possession, and Denmark forbids nuclear weapons on its territory. Denmark had massive demonstrations against the U.S. One warhead was recovered by Navy Seals and Seabees (U.S. naval engineers) in 1979. An August 2000 report suggests that the other bomb remains at the bottom of Baffin Bay.
- April 11, 1968 – A Soviet Golf-class submarine sinks in about 16,000 ft (4900 m) of water, approximately 750 miles (1200 km) northwest of Hawaii's Oahu island. 80 sailors are killed in the incident. Several nuclear torpedoes and three nuclear ballistic missiles were onboard. (Parts of this vessel were later raised by the CIA and Howard Hughes' Glomar Explorer in 1974.) 
- May 21, 1968 – The USS Scorpion (SSN-589), a nuclear-powered attack submarine carrying two Mark 45 ASTOR torpedoes with nuclear warheads, is lost with 99 sailors onboard. The nuclear material has not been recovered. The submarine has been photographed at the ocean bottom, and the U.S. Navy periodically monitors the location for radioactivity. Supposedly there has been no plutonium leakage to date.
- December 8, 1968 – In Nevada, the 30-kt "underground" Plowshare test Schooner leaks radiation which drifts across the Canadian border, a treaty violation
- December 9, 1968 – In Nevada, an underground test of nuclear explosives releases clouds of radioactive steam.
- January 21, 1969 – A coolant malfunction from an experimental underground nuclear reactor at Lucens, Canton of Vaud, Switzerland, released a large amount of radiation into a cavern, which was then sealed.
- May 11, 1969 – 5 kg of plutonium burns at Rocky Flats. Hundreds of railway cars are used to transport the contamination to Idaho Falls, where it is left in unlined trenches over one of the US's most significant aquifers. The Colorado Committee for Environmental Information deployed scientists with sophisticated measuring equipment, putting officials on notice that the public now had the capacity to discover and report releases of radioactive substances. The committees work in response to the fire discovered radioactive residue in areas near Rocky Flats that provided evidence of gradual build-up of radioactive compounds during the years of Rocky Flats operation.
- May 16, 1969 – In San Francisco, California, The nuclear submarine USS Guitarro sinks while being fitted because a forward compartment flooded.
- July 24, 1969 – A serious fire at the AEC's Nuclear Trigger Assembly Facility at Rocky Flats in Colorado suspends US missile production. Areas downwind are contaminated by plutonium. Several factory buildings become uninhabitable and are later dismantled and buried.
- November 15 or 16, 1969 – The USS Gato (SSN-615) reportedly collides with a Soviet submarine in the White Sea. A former crewmember later states that the Gato was struck in the protective plating around the vessel's reactor. No serious damage resulted, although the ship went on alert and prepared to arm a nuclear-tipped anti-submarine missile and nuclear torpedoes. 
- April 12, 1970 – A Soviet November-class attack submarine apparently experiences problems with its nuclear propulsion system while in the Atlantic Ocean. The crew attempts to hook a tow line to a Soviet bloc merchant marine vessel, but fails. The ship sinks, killing 52. 
- June 20, 1970 – In the northern Pacific Ocean, a Soviet Echo-class submarine collides with the USS Tautog after making a 180° crazy Ivan maneuver. American sailors believe the ship sank after the incident, but Russian Navy officers state in 1992 that the ship did not sink. 
- December 18, 1970 – The Baneberry underground test vents 6.7 MCi through a fissure in the rock. Fallout later drifts into Canada, violating the 1963 test-ban treaty.
- November 19, 1971 – At a nuclear power plant operated by Northern States Power Company in Monticello, Minnesota, a water storage facility overflows, releasing 50,000 gallons of radioactive waste water into the Mississippi River. Some radioactive substances later enter the downstream St. Paul water system.
- December 12, 1971 – In the Thames River near New London, Connecticut, radioactive coolant water is being transferred from the submarine USS Dace (SSN-607) to the submarine tender USS Fulton when five hundred gallons are spilled into the river.
- 1972 – The Nuclear Fuel Reprocessing Plant in West Valley, New York is closed after operating for six years. The plant leaves behind leaking tanks containing 600,000 gallons of high-level wastes which eventually contaminates Lake Erie and Lake Ontario.
- March 1972 – Senator Mike Gravel of Alaska submits information to the Congressional Record indicating that a routine check of a nuclear power plant showed radioactivity in the building's water—including the plant drinking fountain—which had been cross-connected with a 3,000 gallon tank of radioactive water.
- December 1972 – A major fire and two explosions at a plutonium fabrication plant in Pauling, New York cause plutonium to contaminate the plant and grounds, resulting in its permanent shutdown.
- 1974 – Workers at the Isomedix Co in New Jersey report that radioactive water was flushed down toilets, contaminating sewer pipes. Also that year in a different incident at the same company, a worker receives a dose of radiation considered lethal, but was saved by prompt hospital treatment.
- May 28, 1974 – The Atomic Energy Commission reports that 12 "abnormal events" in 1973 released radioactivity "above permissible levels" at nuclear power plants.
- 1975 – The USS Guardfish attempts to dump the depleted resin from its demineralization system (used to remove dissolved radioactive minerals and particles from the primary coolant loops of submarines). The ship is contaminated when the wind blows resin back onto the ship. This type of accident is fairly common (see 1961).
- March 22, 1975 – A fire at the Brown's Ferry nuclear reactor located in Decatur, Alabama causes a dangerous lowering of coolant water levels.
- October–November 1975 – While disabled, the submarine tender USS Proteus discharges radioactive coolant water into Apra Harbor, Guam. A Geiger counter at two of the harbor's public beaches showed 100 millirems/hour, fifty times the allowable dose.
- 1977 – The Soviet K-171 accidentally releases a nuclear warhead while off the coast of Kamchatka. After a frantic search involving dozens of ships and aircraft, the warhead is recovered. 
- January 24, 1978 – The Soviet nuclear-powered satellite Cosmos 954 crashes in the Northwest Territories, Canada. Cleanup efforts recover some material, but much remains unreclaimed.
- May 22, 1978 – Aboard the USS Puffer near Puget Sound, Washington, a valve was mistakenly opened, releasing up to 500 gallons of radioactive water.
- March 28, 1979 – Equipment failures and worker mistakes contribute to a loss of coolant and a partial core meltdown at the Three Mile Island nuclear reactor in Middletown, Pennsylvania. This is the worst commercial nuclear accident in the United States to date.
- July 16, 1979 (34th anniversary of the Trinity test) – In Church Rock, New Mexico, the earth/clay dike of a uranium mill's "temporary" settling/evaporating pond fails. The pond was past its planned and licensed life and had been filled two feet deeper than design despite evident cracking. The incident drains about 100 million gallons of radioactive liquids and 1100 tons of solid wastes, which settle out up to 70 miles (100 km) down the Rio Puerco
- September 29, 1979 – Governor Bruce Babbitt of Arizona orders the National Guard to clean up American Atomics' Tucson plant, which he believes has been leaking. (Reports of problems by the Arizona Atomic Energy Commission had been stalled by a commissioner, who was also a vice-president of American Atomics.) At the kitchen for the public school system across the street from the plant, $300,000 of food is found contaminated by radioactive tritium; chocolate cake had 56 nCi/L, 2½ times the "safe" standard. A nuclear official accuses Babbitt of "greed for publicity."class="external">[1
- September 19, 1980 – An Air Force repairman doing routine maintenance in a Titan II ICBM silo in Arkansas drops a wrench socket which rolls off a work platform and falls to the bottom of the silo. The socket strikes the missile, causing a leak from a pressurized fuel tank. The missile complex and surrounding area is evacuated and eight and a half hours later, vapors within the silo ignite and explode with enough force to blow off the two 740-ton silo doors and hurl the nine megaton warhead 600 feet (180 m). The explosion fatally injures an Air Force specialist and twenty-one other USAF personnel are injured. 
- February 11, 1981 – A new worker inadvertently opens a valve and more than 110,000 gallons of radioactive coolant liquid leaks into the containment building of the Tennessee Valley Authority Sequoyah 1 nuclear power plant in rural Tennessee. Eight workers are contaminated with radiation.
- April 25, 1981 – More than 100 workers are exposed to radiation during repairs of a nuclear power plant in Tsuruga, Japan.
- November 2, 1981 – At the US Submarine Pens in Scotland, a fully-armed Poseidon missile is accidentally dropped 17 feet from a crane while being transferred from a submarine to its tender.
- June 1981 – a 3,000 gallon leak of radioactive water occurs at the Salem 2 reactor in Salem, New Jersey.
- 1982 – International Nutronics of Dover, New Jersey completely contaminates its plant, forcing its closure. IN used radiation to treat gems for color, modify chemicals, and sterilize food and medical supplies. The incident involved a pump siphoning water from the baths to the floor. The water entered the sewer system of Dover. The Nuclear Regulatory Commission was informed of the accident ten months later by a whistleblower.
- January 25, 1982 – At Rochester Gas & Electric Company's Ginna plant in Rochester, New York, a steam generator pipe breaks, spilling fifteen thousand gallons of radioactive coolant on the plant floor. Small amounts of radioactive steam escape into the air.
- February 1982 – A 3,000 gallon leak of mildly radioactive water contaminates 16 workers at a nuclear power plant in Salem, New Jersey.
- February 25, 1983 – In Salem, New Jersey, the Salem 1 reactor fails to shut down automatically, but the operator detects the problem 90 seconds before an "incident" can occur. Automatic systems had failed to respond three days earlier. Salem 1 also experienced radioactive gas leaks in March 1981 and September 1982.
- August 1983 – 3,700 liters of tritium leaks into Lake Huron and Lake Ontario from Canadian nuclear power stations.
- August 10, 1985 – About 35 miles (55 km) from Vladivostok in Chazhma Bay, an Echo-class submarine has a reactor explosion, producing fatally high levels of radiation. Ten officers are killed, but the deadly cloud of radioactivity does not reach Vladivostok. 
- 1986 – The US Government declassifies 19,000 pages of documents indicating that between 1946 and 1986, the Hanford Site in Richland, Washington released thousands of gallons of radioactive liquids. Of 270,000 people living in the affected area, most received low doses of radiation from iodine.
- 1986 – International Nutronics of Dover, New Jersey and one of its top executives are convicted by a federal jury of conspiracy and fraud. Radiation remains in the vicinity of the plant, but the NRC says the levels aren't hazardous.
- January 6, 1986 – At the Kerr-McGee nuclear fuel reprocessing plant in Gore, Oklahoma, a cylinder of nuclear material bursts after being improperly heated. One worker dies, 100 are hospitalized.
- 1986 – The NRC revokes the license of a Radiation Technology, Inc (RTI) plant in New Jersey for worker safety violations. A safety device to prevent people from entering the irradiation chamber during operation was bypassed. A worker received a near-lethal dose of radiation. RTI was cited 32 times. Violations also included throwing radioactive garbage out with the regular trash.
- April 26, 1986 – The worst accident in the history of nuclear power occurred at the Chornobyl nuclear power plant located near Kiev, USSR (now part of the Ukraine). Fire and explosions resulting from an unauthorized experiment left 31 dead in the immediate aftermath. Radioactive nuclear material was spread over much of Europe. Over 135,000 are evacuated from the areas immediately around Chernobyl and over 800,000 from the areas of fallout in Ukraine, Belarus and Russia. About 4,000 miles² (10,000 km²) were taken out of human use for an indefinite time.
- October 3, 1986 – 480 miles (770 km) east of Bermuda, a Soviet Yankee I-class submarine experienced an explosion in one of its nuclear missile tubes and at least three crew members were killed. 34 nuclear missiles and two reactors were on board. Soviet leader Mikhail Gorbachev privately communicated news of the disaster to U.S. President Ronald Reagan before publicly acknowledging the incident on October 4. Two days later, on October 6, the ship sank in the Atlantic Ocean while under tow in 18,000 feet (5.5 km) of water. 
- 1987 – In the Goiânia accident, scavengers broke open a radiation-therapy machine in an abandoned clinic of Goiânia, Brazil. They sold the kilocurie caesium-137 source as a glowing curiosity. 400 were contaminated, four die.
- 1988 – The National Research Council released a report listing 30 "significant unreported incidents" at Savannah River production plants in Georgia over the previous 30 years. Ground water contamination occurred.
- June 6, 1988 – Radiation Sterilizers in Decatur, Georgia Reports a leak of caesium-137 at their facility. 70,000 medical supply containers and milk cartons were recalled. Ten employees were exposed, and three "had enough on them that they contaminated other surfaces" including their homes and cars. (according to Jim Setser at the Georgia Department of Natural Resources.)
- October 1988 – At the nuclear trigger assembly facility at Rocky Flats in Colorado, two employees and a Department of Energy inspector inhale radioactive particles, causing closure of the plant. Several safety violations were cited, including uncalibrated monitors, inadequate fire equipment, and groundwater contaminated with radioactivity.
- April 7, 1989 – The Soviet Komsomolets attack submarine catches fire about 300 miles (480 km) off th ecoast of Norway. 27 crew members escape, but the remaining 42 do not survive as the ship sinks. Two nuclear-armed torpedoes were on-board along with the vessel's nuclear reactor. 
- January 1989 – A fault was discovered to run under the Savannah River nuclear processing plants in Georgia to an underground aquifer providing drinking water to much of the southeast US. Nearby turtles had radioactive strontium of up to 1,000 times the background level.
- November 24, 1989 – Near-meltdown at Greifswald, East Germany 
- January 23, 1990 – 12,000 litres of heavy water are accidentally dumped into the containment vault below the Bruce A reactor in Ontario, Canada when a software failure releases the brakes on a refueling machine.
- September 27, 1991 – While testing a missile in the White Sea, the crew of a Soviet Typhoon-class submarine discovers a defect and surfaces. The missile starts burning upon contacting clear air and leaves its launch tube as a fireball is reported on deck. The ship dives to put out the fire. 
- February 11, 1992 – The Commonwealth of Independent States Sierra-class attack submarine K-239 (Barracuda) collides with the USS Baton Rouge (SSN-689) in the Barents Sea. No apparent damage results, although the incident causes the Russians to complain that the Baton Rouge was inside CIS territorial waters. American naval officers maintain that the ship was in international waters at the time. 
- November 24, 1992 – The Fuel Reprocessing Plant in Gore, Oklahoma is closed after repeated safety and environmental violations. Its record during 22 years of operation included a 1986 accident that killed one worker and injured dozens of others and contamination of the Arkansas River and groundwater. It had been shut down the previous week by the Nuclear Regulatory Commission when an accident released toxic gas, causing thirty-four people to seek medical attention. The plant had been shut down in 1991 when the water of a nearby construction pit had high concentrations of uranium. The government cited Carol Couch, the plant's environmental manager, for obstructing the investigation and falsifying documentation.
- February 15, 1993 – 18,000 litres of heavy water are spilled at the Darlington nuclear power plant in Canada.
- March 20, 1993 – The American submarine USS Grayling (SSN-646) collides with a Russian Delta III-class submarine in the Barents Sea, 105 nautical miles (120 miles, 195 km) north of the Kola Peninsula. 
- 1997 – Georgian soldiers suffer radiation poisoning and burns. They are eventually traced back to training sources abandoned, forgotten, and unlabelled after the collapse of the Soviet Union. One was a caesium-137 pellet in a pocket of a shared jacket which put out about 130,000 times background at 1 meter distance.
- May 1997 – A 400 gallon tank which contained ~3 gl. of toxic chemicals explodes at Hanford Site in Richland, Washington, causing a release of about 25,000 gallons of water from a ruptured fire sprinkler main. Fluor Daniel Hanford Inc, was cited for violations of the Department of Energy's nuclear safety rules and fined $140,625. Violations included the contractor's failure to assure that breathing devices operated effectively (although they did operate correctly), failure to make timely notifications of the emergency, and failure to conduct proper radiological surveys of workers (failure of a employee to follow established procedures), failure to assure adherence to "criticality" safety procedures,(even though the area that the flood occurred had no fissile material). These procedures prevent the waste from acting like a reactor and generating more heat and radioactivity.
- 1998 – Recycler Acerinox in Cádiz, Spain unwittingly melts scrap metal containing radioactive sources; the radioactive cloud drifts all the way to Switzerland before being detected.
- July, 1999 – A fire broke out during a waste procedure at Livermore when a technician failed to fully assess the bagged materials to be disposed, allowing bulk uranium to remain in the waste. The bag began glowing and starting to expand. The uranium had undergone spontaneous combustion and ignited other materials in the waste package.
- August 8, 1999 – The Washington Post reports that thousands of workers at the Department of Energy's Gaseous Diffusion Isotope Separation Plant in Paducah, Kentucky were unwittingly exposed to plutonium and other highly radioactive metals over a 23-year period. Workers were told they were handling uranium rather than the more toxic plutonium. They inhaled radioactive dust as part of a government experiment to recycle used nuclear reactor fuel.
- September 30, 1999 – Japan's worst nuclear accident ever takes place at a uranium reprocessing facility in Tokaimura, Ibaraki prefecture, northeast of Tokyo, Japan. The direct cause of the accident was workers putting uranyl nitrate solution containing about 16.6 kg of uranium, which exceeded the critical mass, into a precipitation tank. The tank was not designed to dissolve this type of solution and was not configured to prevent eventual criticality. The incident exposes workers and residents in the surrounding area to extremely high levels of radiation.
- February 15, 2000 – The Indian Point II nuclear power plant in New York vents a small amount of radioactive steam when a steam generator fails.
- June 2000 – United States Senator Mike DeWine (R-OH) leads a field senate hearing to discover evidence about on- and off-site contamination at the Portsmouth Gaseous Diffusion Isotope Separation Plant in Piketon, Ohio. Testimony indicates that the Piketon plant altered workers' radiation dose readings and worked with medical professionals to fight worker's compensation claims.
- July 2000 – Wildfires hit the highly radioactive "B/C" waste disposal trenches at Hanford Site in Richland, Washington. The radioactive material is not on the surface, but underground. No measurable airborne contaminants detected outside the Site boundaries. No radioactive contaminants detected in any of the surrounding cities (Richland, Pasco & Kennewick).
- August 2000 – The Russian submarine Kursk sinks in the Barents Sea after an apparent internal torpedo accident, killing 118. Russia eventually recovers the submarine's nuclear reactor and states that the submarine had carried no nuclear weapons. Greenpeace, in an effort urging Russia to recover the reactor, states there are now ten nuclear reactors and over fifty nuclear warheads on the floors of the world's oceans.
- The (supposedly successful) Japanese program to develop nuclear weapons in World War II. The story is that a prototype was exploded in the China Sea, but the factory in Japanese Korea was not yet on-line when the US began nuclear bombing of Japan. If this is true, there would be lots of radioactive waste.
- Reports of glow slaves (intentionally irradiated unwilling nuclear laborers) in the USSR, China, India, Pakistan, North Korea, and pre-World War II Japanese Korea.
- British tests of enhanced-fallout nuclear weapons in Australia.
- South African and Israeli nuclear programs and radioactive emissions.
- At-sea decommissionings (simple scuttlings) of naval nuclear reactors by the Soviet, British and French navies.
- Undocumented radiation releases in the USSR, France, India, China, Japan and Pakistan.