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 and business secrecy, it is difficult to determine with certainty the extent of some events listed below or, occasionally, whether they happened at all.

An accidental detonation of a nuclear weapon has never happened. For an implosion assembly weapon this risk is lower, because it would require the precisely synchronized simultaneous detonation of its numerous explosive lenses. For a gun-assembly weapon the risk is higher.

Before 1950

• 1904 – Menlo Park New Jersey During the early years of X-ray experimentation Thomas Edison’s work on the fluorescence of different materials under X-ray bombardment led to his invention of a practical fluoroscope in 1896. A glassblower by the name of Clarence Madison Dally worked for Edison forming X-ray tubes, he was known to test many of the tubes on his bare hands. In 1896 Dally received a severe X-ray burn yet he seemed to recover and continued to work for another two years in the X-ray lab. Soon after he developed skin cancer in both hands that spread quickly requiring the eventual amputation of both of his arms. Dally died of skin cancer in 1904 he is the first person known to die from X-ray exposure. In 1903 Edison made the decision to stop his research on high energy ionizing radiation, he also refused to patent the fluoroscope so it could freely benefit mankind.[1]  (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7998548&dopt=Abstract)[2] (http://www.karlloren.com/ultrasound/p51.htm)[3] (http://www.uihealthcare.com/depts/medmuseum/galleryexhibits/trailoflight/03xraymartyrs.html)

• December, 1941 – Germany While conducting an experiment in fast fission Werner Heisenberg and his colleague Robert Doepel were to learn first hand the pyrophoric nature of powdered uranium metal. An assistant causes a uranium fire while transferring uranium powder to a reaction vessel. The fire spread to other uranium stored close by. The fire was eventually smothered but the next morning smoldering uranium was uncovered during clean up. This accident outlined the need to perform future powdered uranium transfers in an inert atmosphere. [4] (http://www.fpp.co.uk/books/VirusHouse/index.html) pg 130[5] (http://www.haigerloch.de/stadt/keller_englisch/INT.HTM)

• June 24, 1942 – Leipzig Germany Heisenberg and Doepel had an explosion in the Leipzig L-IV atomic pile, which resulted in a major fire. This occurred shortly after L-IV demonstrated Germany’s first signs of neutron propagation. The nearly one ton device was in the process of being checked for a possible heavy water leak to the core. During the investigation air was accidentally introduced into the reactor's uranium powder core which in turn burst into flames. Despite all attempts to extinguish the crude reactor, the fire caused the heavy water jacket to boil, eventually generating enough steam pressure to blow the reactor apart. A spray of burning uranium particles were scattered throughout the lab, igniting a major facility fire. [6] (http://www.fpp.co.uk/books/VirusHouse/index.html) pg 137-132[7] (http://www.haigerloch.de/stadt/keller_englisch/INT.HTM)

• 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 (hydrofluoric acid), a dangerous acid, which was inhaled by all five. Bragg and Meigs died soon after from whole-body acid burns. [8] (http://www.childrenofthemanhattanproject.org/FH/PH/Article_04_1.htm)

• 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. [9] (http://members.tripod.com/~Arnold_Dion/Daghlian/)

• May 21, 1946 – Canadian physicist Louis Slotin manually assembled a critical mass of plutonium while demonstrating his technique to visiting scientists at Los Alamos and suffered a fatal criticality accident. 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. Slotin died on May 30 from massive radiation poisoning, with an estimated dose of 1000 rads (rad), or 10 grays (Gy). While none of the seven observers received a lethal dose, two died suffering symptoms of radiation poisoning a few years later. In the movie Fat Man and Little Boy, John Cusack played a combination of Harry K. Daghlian and Louis Slotin. [10] (http://web.ncf.ca/lavitt/louisslotin/2trnt10.html)

1950s

• February 13, 1950 – B-36 2075, 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.[11] (http://www.lutins.org/nukes.html)

• 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 was on board at the time of the crash; its casing was destroyed, but the weapon did not go off.[12] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/intro.html)

• August 5, 1950 – A nuclear-armed B-29 Superfortress had problems during take off from Fairfield-Suisun Air Force Base in California. The emergency landing ended in a fiery crash. A fire fighting team was dispatched in an attempt to rescue the crew. In the midst of the rescue effort the intense fire detonated over 10,000-pounds of high explosive used in the primary portion of the nuclear weapon killing 19 people. The explosion formed a twenty-yard crater across in the runway. One of the people killed in the rescue attempt was Gen. Robert F. Travis for whom the base is now named.

• 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 (3,200 m). The bomb, carrying the depleted uranium tamper but not its plutonium core ("pit"), was set to self-destruct at 2500' (750 m) and dropped over the St. Lawrence River off RiviËre du Loup, Quebec. The explosion shook area residents and scattered nearly 100 pounds (45 kg) of depleted uranium.[13] (http://www.bullatomsci.org/issues/1999/nd99/nd99norris.html)

• 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 (1.2 m) into the air, where it jammed in the superstructure. Thousands of curies (several terabecquerels) of fission products were released into the atmosphere, and a million US gallons (3,800 m≥) 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/km≤ (2 kBq/km≤); some puddles registered 270 nCi/L (10 Bq/m≥), nearly 3000 times the United States Atomic Energy Commission limit. The radiation was traced to fallout from the Simon test, which had occurred two days previously.[14] (http://ratical.org/radiation/SecretFallout/SFchp1.html) An even worse rainout followed in June. [15] (http://ratical.org/radiation/SecretFallout/SFchp4.html)

• May 19, 1953 – The United States government detonated the 32-kiloton of TNT (130 TJ) 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. [16] (http://www.commondreams.org/views03/0526-05.htm) Winds carried fallout 135 miles (220 km) to St. George, Utah, where residents reported "an oddly metallic sort of taste in the air." [17] (http://www.ratical.org/radiation/KillingOurOwn/KOO3.html) 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). [18] (http://www.thebulletin.org/issues/1997/nd97/nd96ortmeyer.html)

• March 1, 1954 – During the early morning of March 1st, a Japanese Fishing boat, the Daigo Fukuryu Maru, or "Number 5 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 15 megaton of TNT (63 PJ) detonation of the hydrogen bomb "Castle 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 gathered 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 2Ω 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 dollars in compensation. [19] (http://www.ratical.org/radiation/KillingOurOwn/KOO4.html) 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 1.75 Sv, 28 residents of Rongerik atoll were exposed to doses of about 780 mSv before being permanently evacuated, 18 residents of Alininae atoll were exposed to 680 mSv for about 50 hours, and 157 residents of Utirik atoll were exposed to 140 mSv for about 55 to 75 hours.

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.

• 1955 – Unexpected wind shift dropped test fallout on Las Vegas, Nevada [20] (http://www.ratical.org/radiation/KillingOurOwn/KOO3.html)

• November 22, 1955 – The Soviet Union tested the first weaponized fusion device, 1.6 Mt. The Third Idea bomb was the first hydrogen bomb to be dropped from an aircraft. Atmospheric refraction of the shock wave caused unexpected blast damage, killing three. [21] (http://gawain.membrane.com/hew/Nwfaq/Nfaq8.html)

• November 29, 1955 – An operator's error destroyed a three-year-old experimental breeder reactor EBR-I. [22] (http://mt.sopris.net/mpc/industrial/nuclear.operations.html) [23] (http://www.citizen.org/cmep/foodsafety/food_irradiation/articles.cfm?ID=1461)

• 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 practising 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 U.S. 7th Airborne 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." He was presumably referring to the possibility of a high explosive detonation and possible radiological contamination of the area, rather than a nuclear explosion. Accidental ignition of the explosives in a nuclear weapon is insufficient to trigger the nuclear explosion of an implosion assembly weapon, such as those involved in the accident, because this requires the precisely synchronised simultaneous detonation of its numerous explosive lenses (although it could detonate a gun-assembly weapon).

• 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 jeweler's lathe isolated inside a Plexiglas box and 33 inches (840 mm) 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 of TNT (40 PJ) hydrogen bomb. The trigger explosive detonated, creating a 12 foot (4 m) deep crater 25 feet (8 m) 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 glove box 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. [24] (http://www.energy-net.org/00NUKE/nhistory.htm) [25] (http://www.cdphe.state.co.us/rf/1957fire.htm) [26] (http://www.racteam.com/Experience/Publications/RF_1957_Fire_Risk.htm) [27] (http://www.ratical.org/radiation/KillingOurOwn/KOO8.html)

• 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. The explosion, estimated to have the same energy as 75 tons of TNT (310 GJ), releases some 20 MCi (700 PBq) and subjecting (by various estimates) 124,000 to 270,000 people to dangerously high levels of radiation. [28] (http://www.american.edu/projects/mandala/TED/ural.htm) Of these, only 7,500 were evacuated, most of them too late to prevent dangerous levels of exposure. Inadequate medical records mean that number of people that died as a result is unknown, but probably numbers hundreds. 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. Approximately 41,000 acres (166 km≤) of the worst contamination region has been designated a 'nature reserve', where scientists study the effects of it on wildlife. The US government learnt of the accident but kept it secret to avoid turning public opinion against the fledgling US nuclear industry. The accident was revealed by the US government in 1977 as a result of the Freedom of Information Act, and only admitted by the Russian government in 1992.

• 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 mile≤ (520 km≤) 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. [29] (http://www.nucleartourist.com/events/windscal.htm) [30] (http://www.lakestay.co.uk/1957.htm) [31] (http://www.british-energy.com/media/factfiles/mn_item57.html) [32] (http://www.bellona.no/en/energy/nuclear/sellafield/wp_5-2001/21663.html)

• 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 (2,200 m) 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. See Tybee Bomb for further information.

• February 28, 1958 – At the US airbase at Greenham Common, 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 whilst the other struck the ground 65 feet (20 m) behind a parked B-47E. The parked B-47E, which was fuelled with a pilot onboard and carrying a 1.1 megaton of TNT (4.6 PJ) B28 thermonuclear free fall 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. The fire detonated the high explosives in the nuclear weapon and convection spread plutonium and uranium oxides over a wide area — foliage up to 13 kilometres away was contaminated with uranium-235. 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. However two scientists, F.H. Cripps and A. Stimson, working for the Atomic Weapons Research Establishment at Aldermaston, independently discovered high concentrations of radioactive contamination around the base in 1960. Their secret report referring to the accident was declassified in 1996.

• 1958 – Unexpected wind shift drops test fallout on Los Angeles, California [33] (http://www.ratical.org/radiation/KillingOurOwn/KOO3.html)

• 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 (20 m) wide and 30 feet (10 m) 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.

• June 16, 1958 – A prompt neutron criticality accident occurred in the C-1 wing of building 9212 at the Oak Ridge Tennessee Y-12 complex. This accident was partially due to a lack of supervision during a transfer of material that was thought to be water from a safe geometry container into a 55-gallon drum of unsafe geometry. A supercritical portion of highly enriched uranyl nitrate was allowed to collect in the drum It is estimated that the criticality produced 1.3 x 10*18 fissions. Eight employees were in close proximity to the drum during the accident, one was within three to six feet the other seven ranged fifteen to fifty feet. Afterwards the plant employees indium foil badge dosimeters pointed to thirty-one people with a potential significant neutron dose. [34] (http://www.cdc.gov/niosh/ocas/pdfs/tbd/y1221b.pdf)

• 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 National 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 15 grams of plutonium 239.

1960s

• 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.

• October 13, 1960 – One of the most serious accidents involving a naval reactor occurred on a USSR Northern Fleet vessel. The incident was caused by a loss of coolant to the reactor, and is classified accordingly. The Project 627 – November class submarine K-8 was on exercise in the Barents Sea when a leak developed in the steam generators and in a pipe leading to the compensator reception. The equipment for blocking these leaks was also damaged such that the crew itself began the work of stopping the leak. They mounted a provisional system for supplying water to the reactor to ensure cooling of the reactor and thereby avoid the risk of a core melt in the reactor. Large amounts of radioactive gases leaked out which contaminated the entire vessel. The true activity of the gases could not be determined because the instrumentation only went to a certain level. Three of the crew suffered visible radiation injuries, and according to radiological experts in Moscow, certain crew members had been exposed to doses of up to 1.8 - 2 Sv (180 - 200 rem). [35] (http://www.bellona.no/imaker?id=11084&sub=1)

• 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.

SL-1 reactor being removed from the National Reactor Testing Station

• January 3, 1961 – Critical SL-1 reactor.

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 m≤) 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 actuate-able 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. 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 mrad/h (2 mSv/h) hundreds of feet or meters 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 mrad/h (10 mSv/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 30 to 270 mSv, according to 1961 Atomic Energy Commission reports. The reactor was dismantled and the 13 short ton (12 metric ton) core and pressure vessel was removed several months later.

• January 24, 1961 – A B-52 bomber suffered a fire caused by a major leak in a wing fuel cell and exploded in mid-air 12 miles (20 km) north of Seymour Johnson Air Force Base, Goldsboro, North Carolina. The incident released the bomber's two Mark 39 hydrogen bombs. Five crewmen parachuted to safety, but three died—two in the aircraft and one on landing. Three of the four arming devices on one of the bombs activated, causing it to carry out many of the steps needed to arm itself, such as the charging of the firing capacitors and critically the deployment of a 100-foot (30 m) diameter retardation parachute. The parachute allowed the bomb to hit the ground with little damage. The fourth arming device — the pilot's safe/arm switch — was not activated and so the weapon did not detonate. The other bomb plunged into a muddy field at around 700 miles per hour (300 m/s) and disintegrated. Its tail was discovered about 20 feet (7 m) down and much of the bomb recovered, including the tritium bottle and the plutonium. However, excavation was abandoned because of uncontrollable flooding by ground water, and most of the thermonuclear stage, containing uranium, was left in situ. It was estimated to lie at around 180 feet (55 m). The Air Force purchased the land and fenced it off to prevent its disturbance, and it is tested regularly for contamination, although none has so far been found. 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. The movie K-19: The Widowmaker, starring Harrison Ford and Liam Neeson, tells a controversially fictionalized story of these events.

• October, 1961 – On four occasions between mid-October 1961 and August 1962, United States Air Force Jupiter IRBM mobile missiles carrying 1.4 megaton (5.9 PJ) nuclear warheads were struck by lightning at their launch sites near the Gioia Del Colle Air Base, Italy. In each case, thermal batteries were activated, and on two occasions, tritium-deuterium "boost" gas was injected into the warhead pits, partially arming them. After the fourth lightning strike on a Jupiter IRBM, the U.S. Air Force placed protective lightning strike-diversion tower arrays at all of the Italian and Turkish Jupiter IRBM missiles sites. These Jupiter missiles are sometimes called "The Other Missiles Of October". Their deployment in Italy and Turkey prompted the Soviet Union to place its missiles in Cuba in 1962, causing the Cuban Missile Crisis.

• 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.

• July 26, 1962 – Nuclear Test attempt Bluegill Prime from Johnston Island in the Pacific Ocean. Second failure to launch a nuclear weapon using the Thor IRBM missile. The payload consisted of two re-entry vehicles, one with an instrument pod, the other with the warhead. The missile engine malfunctioned immediately on ignition. Range safety fired the destruct system while the missile was still on the launch pad. The Johnston Island launch complex was heavily damaged and contaminated with plutonium. Three months of repairs and decontamination were necessary before tests could resume.

• April 10, 1963 – The nuclear submarine USS Thresher (SSN-593) sinks east of Boston, Massachusetts, with 129 men onboard. 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 during 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 tertiary-loop cooling inlet, and that the reactor and its design were 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 12, 1964 – The nuclear-powered navigation satellite Transit 5BN-3 fails to achieve orbit and burns up in the Earth's atmosphere.

• April 21, 1964 – A US nuclear-powered navigational satellite failed to reach orbital velocity and reentered the atmosphere 150,000 feet (46 km) above the Indian Ocean. The satellite's SNAP generator contained 17 kCi (630 TBq) of plutonium-238, which at least partially burned upon reentry. Increased levels of Pu₂₃₈ were first documented in the stratosphere four months later. About 16 kCi (600 TBq) 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 mrem or 0.6 µSv) compared to fallout from weapons tests in the 1950s (0.35 mrem or 3.5 µSv).

• July 24, 1964 – A criticality accident occurred at a plant designed to recover uranium from scrap material left over from fuel element production. The Wood River Junction facility was located in Charlestown Rhode Island. An operator (Robert D. Peabody) was in the process of precipitating low concentrations of uranium out of contaminated trichloroethane solvent. This process was carried out in containers of safe geometry (5-inch diameter, 11-liter volume). Due to the large amount of contaminated solvent being processed this operation was moved to an 18 inch diameter by 25 inch deep container that is an unsafe geometry for high concentration solutions. Since the process involved solutions of low concentration this lapse in safety was overlooked. Unfortunately a bottle of high concentration material was mistakenly added to the unsafe container causing a flash of Cherenkov radiation. The criticality resulted in a reaction of 1 x 10^17th fissions and an exposure of 10,000 rad which killed Mr. Peabody within 49 hours. Ninety minutes later a second excursion happened when the container’s stirring unit was shut off exposing a two man clean up crew to a reaction of 2 x 10^16th fissions. This was not discovered until later when their dosimeters were checked because the radiation alarm was still blaring from the first excursion. Their dose was estimated to be 60 rad for one of the men and 100 rad for the other, neither man showed an adverse effect to their exposure.[36] (http://www.fas.org/sgp/othergov/doe/lanl/la-3611.pdf) pg27[37] (http://www.bazley.net/archives/UNCdeath.html)

• December 5, 1964 – A Minuteman 1B missile was on strategic alert at Launch Facility (LF) L-02, Ellsworth AFB, South Dakota. Two airmen were dispatched to the LF to repair inner zone (IZ) security system. In the midst of their checkout of the IZ system, one retrorocket in the spacer below the Reentry Vehicle (RV) fired, causing the RV/nuclear warhead to fall about 75 feet (23 m) to the floor of the silo. When the RV/nuclear warhead struck the bottom of the silo, the arming and fusing/altitude control subsystem containing the batteries was torn loose, thus removing all sources of power from the RV/nuclear warhead. The RV structure received considerable damage. All safety devices operated properly in that they did not sense the proper sequence of events to allow arming the warhead. There was no detonation or radioactive contamination.

• January 1965 – An accident at Lawrence Livermore National Laboratory releases 300 kCi (11 PBq) 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. [38] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/content/1960e.html)

• 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 US gallons (150,000 L) 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 metric 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. The motion picture Men of Honor (2000), starring Cuba Gooding, Jr. as USN Diver Carl Brashear, and Robert De Niro as USN Diver Billy Sunday, contained an account of the fourth bomb's recovery.

• 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.

• Winter 1966-1967 (date unknown) – The icebreaker Lenin, the USSR's first nuclear-powered ship, suffers a major accident (possibly a meltdown) in one of its three reactors. It was rumoured that around 30 of the crew were killed. The ship was abandoned for a year to allow radiation levels to drop before the three reactors were removed, to be dumped into the Tsivolko Fjord on the Kara Sea, along with 60% of the fuel elements packed in a separate container. The reactors were replaced with two new ones, and she re-entered service in 1970.

• April 1967 – A drought dries up Lake Karachay near Chelyabinsk, Russia. From 1951 onwards, the swampy 0.5 square kilometre lake was used as a dump for medium and high level nuclear waste from Chelyabinsk-40, part of the Mayak facility. Whirlwinds spread around 5 MCi (190 PBq) of contaminated lake sediment over approximately 1,800 square kilometres.

• 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.) [39] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/content/1960h.html)

• 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.

• May 24, 1968 – The nuclear submarine K-27 (Project 645) was out at sea. During sea trials, the nuclear reactor had operated at reduced power, and on May 24, power inexplicably suddenly dropped. Attempts by the crew to restore power levels failed. Simultaneously, gamma radiation in the reactor compartment increased to 150 R/h. Radioactive gases were released to the reactor compartment from the safety buffer tank, and radiation on board the submarine increased. The reactor was shut down, and approximately 20% of the fuel assemblies were damaged. The incident was caused by problems in the cooling of the reactor core The entire submarine was scuttled in the Kara Seain 1981. [40] (http://www.bellona.no/imaker?id=11084&sub=1)

• August 27, 1968 – The Project 667 A Yankee class nuclear submarine K-140 was in the naval yard at Severodvinsk for repairs. On August 27, an uncontrolled increase of the reactor's power occurred following work to upgrade the vessel. One of the reactors started up automatically when the control rods were raised to a higher position. Power increased to 18 times its normal amount, while pressure and temperature levels in the reactor increased to four times the normal amount. The automatic start-up of the reactor was caused by the incorrect installation of the control rod electrical cables and by operator error. Radiation levels aboard the vessel deteriorated. [41] (http://www.bellona.no/imaker?id=11084&sub=1)

• December 8, 1968 – In Nevada, the 30-kt of TNT (125 TJ) "underground" Plowshare test Schooner leaks radiation which drifts across the Canadian border, a treaty violation. [42] (http://www.ratical.org/radiation/KillingOurOwn/KOO5.html)

• 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 committee's 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. [43] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/content/1960j.html)

1970s

• 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. [44] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/content/1970a.html)

• April 18, 1970 – The Lunar Module of the Apollo 13 mission reenters the Earth's atmosphere after the aborted lunar landing. The Lunar Module contained a radioisotope thermoelectric generator powered science station. The Lunar Module was directed to reenter so that any surviving pieces would impact near the Tonga Trench in the Pacific Ocean

• 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. [45] (http://www.cnn.com/SPECIALS/cold.war/experience/the.bomb/broken.arrows/content/1970b.html)

• December 18, 1970 – The Baneberry underground test vents 6.7 MCi (250 PBq) through a fissure in the rock.[46] (http://www.shundahai.org/area_8_nts.htm) Fallout later drifts into Canada, violating the 1963 test-ban treaty.[47] (http://www.ratical.org/radiation/SecretFallout/SFchp16.html)

• 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 US gallons (190 m≥) 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 500 US gallons (1,900 L) 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 US gallons (2,300 m≥) 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 US gallon (11 m≥) tank of radioactive water.

• September 1972 – The PM-3A - 1250 KW nuclear reactor that had been in operation since March 1962 at the U.S. base at McMurdo Station, Antarctica, was shut down due to radioactive leaks. Throughout its 10-years of operations, it had repeated shutdowns and radiation leaks. The reactor was later shipped back to the United Sates, along with 101 drums of radioactive contaminated earth. A further 11,000 cubic metres of contaminated rock were also later removed. It was May 1988 before the site was decontaminated enough for unrestricted use.

• 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, on the Tennessee River 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.

• August 1976 – An explosion at a Hanford, Washington, Plutonium Finishing Plant contaminated several workers. Th