Accidents Involving Nuclear Energy

Taking off from Fairfield-Suisun AFB, a USAF Boeing B-29-NR loses power in its number two engine. In accord with precautionary measures of the time, the nuclear weapon it carries lacks a fissile core. The plane lifts off, but the landing gear cannot be raised, increasing drag. The pilot circles back for an emergency landing, but the heavily laden bomber does not reach the runway.

Twelve occupants are killed in the crash; the other eight receive minor injuries. Twenty minutes after the crash, during firefighting efforts, the 10,000 pounds of high explosive in the bomb detonate. Another 180 people are killed or injured. Although the bomb is destroyed, radiological contamination of the site is negligible.

In the sixth year of operation of Canada's NRX research reactor in Chalk River, a complicated series of operator errors and safety system malfunctions leads to a massive power excursion which causes partial meltdown of the core. The accident floods the basement with a million gallons of cooling water carrying 10,000 Curies of long-lived radioisotopes. Despite a total estimated yield of 1.2x10²⁰ fissions, worker exposures are apparently low.

A subsequent hydrogen explosion throws the four-ton gas-holder dome to its maximum height, 1.2m. The containment vessel is not breached. But since air is being used to cool some of the fuel rods, thousands of curies of fission products are released into the atmosphere, making this the first major reactor disaster. Lt. Jimmy Carter, then a nuclear engineer in the U.S. Navy, takes part in the cleanup. That involves pumping a million gallons of contaminated water out of the reactor building into shallow trenches near the Ottawa River, removing and burying the core, and installing a replacement. The NRX is back in service in one or two years.

Plutonium is being recovered from spent fuel rods at the Mayak Production Association in the Soviet Union. This operation involves many processing steps on the plutonium nitrate solution. On Sunday, 15 March, operators ignore several established procedures. The most significant violations are using vessels next to each other (which allows neutronic interactions) and exceeding the limit of 500 grams of solution per vessel. The operators transfer the contents of two vessels (#2 & #4) into a third (#18). Another factor is that vessel 18 already holds 5 liters of solution at the beginning of the shift — a transfer for which there is no log entry. Noticing vapor from the solution in vessel 18, and feeling its warmth, the operator there immediately reconnects the transfer hose. Some of the solution is pulled into a vacuum trap, ending the fission reaction.

The two operators, untrained in criticality safety, elect not to report the event. (Also, the facility has no criticality alarm systems.) The accident is not discovered until two days later, when the operator near vessel 18 gets sick. His dose is estimated as 1,000 rads. He loses both legs, but lives 35 more years.

The criticality measurement table at the Sarov (Arzamas-16) facility in the southern Urals is designated FKBN. Its vertical piston is hydraulically operated and incorporates no fast-acting scram mechanism.

On 9 April, during the lunch hour, a single operator is working the apparatus alone in violation of buddy-system rules. He also places steel separators half as thick as called for by the experiment plan (5mm vs. 10 mm) on the lower half of the fissile mass. As the table raises this lower half to the upper, criticality occurs. The resulting heat melts a portion of the plutonium. The excursion sets off an alarm.

About 2 hours later, the operator and a supervisor examine the apparatus closely, receiving low doses of 1-2 rads. The yield of the excursion is about 10¹⁶ fissions. The active portion of the apparatus is shipped to the Mayak facility for further analysis and disposition. The remaining parts are clean enough for immediate re-use. However, the FKBN is replaced by a model with better safety features.

During the early morning, the crew of the Lucky Dragon, a Japanese fishing boat in mid-Pacific, think they see the sun rising to the west of them. It is instead "Castle Bravo" — a 6-MT hydrogen bomb fired at Bikini Atoll, 85 miles away. Four hours later, white ash begins to fall like snow on the boat. Many crew members scoop it off the decks and into bags as souvenirs. By evening, all 23 crew members are sick. They are hospitalized in Japan, where one dies due to radiation-induced kidney failure.

The white flakes also fall on the 86 residents of Rongelap Atoll, closer to the test site, soon piling up half an inch deep. Similar fates befall the residents of progressively more distant atolls named Rongerik, Alininae, and Utirik. By the time they are evacuated 50 to 75 hours later, many are sickened. The first warning of radiation in the fallout is raised seven hours after the blast, when the ash reaches the U.S. personnel at the weather station on Rongerik. They are moved out within 30 hours. These atolls are part of the Marshall Islands, a trust territory for which the U.S. is responsible.

The incident causes a rift between Japan and the U.S., which has not warned other nations about the test. (A mitigating factor is that an overlooked reaction boosted the bomb's yield to about 15 MT and thus expanded the danger area.) The U.S. issued an apology and paid $2 million in compensation. The exclusion was widened for later tests.

At the National Reactor Testing Station near Idaho Falls, ID, the BORAX-I has been well-studied and is about to be dismantled. Its operators decide to run one more transient test: an overload which will melt about 4% of its fuel plates.

In the event, the power excursion and subsequent steam explosion completely destroy the core and rupture the tank surrounding it. Pieces of the tank are found 200 feet away. Because of the remote location, nothing else is damaged and no one is exposed to radiation.

EBR-1, the experimental reeder reactor at the National Reactor Testing Station, has operated for three years and met its objectives. A final study of "prompt positive power coefficient without coolant flow" is conducted. When power reaches 1 MW, the scram signal is given. Unfortunately the slow motor-driven system is activated by error instead of the fast-acting gravity-driven system. Later examination shows that half the core has melted and vaporized sodium-potassium eutectic has forced some of the highly reactive coolant into the reflector.

The source concludes its report with this optimistic note: "During this accident no one received more than trivial radiation from airborne fission products, and direct exposure was essentially zero." Public Citizen reports that "The public is not made aware of this meltdown until Lewis Strauss, head of the Atomic Energy Commission, is confronted by the Wall Street Journal and has to admit his ignorance of the accident."

Two explosions destroy a portion of Sylvania Electric Products' Metallurgy Atomic Research Center in Bayside, Queens, NY. Nine workers are injured.

A CDC document indicates that this facility was engaged in research on uranium and thorium powder metallurgy, and also investigated the health effects of beryllium and uranium powders in its main building until the AEC Medical Division required it to construct a separate laboratory for health studies. According to the CDC document, referenced below, the facility operated from 1947 through 1962 or 1965, the State of New York declared the site decontaminated of radioactivity in 1985, and condominiums were subsequently built on the site.

A U.S. B-47 practising landings at Lakenheath Air Base in Suffolk, England, skids into a bunker holding three Mark VI bombs. A secret cable to SAC commander Gen. Curtis LeMay from Gen. James Walsh, commander of U.S. 7th Airborne Division, reports that "The B-47 tore apart the igloo and knocked about three Mark Sixes. Aircraft then exploded, showering burning fuel over all. Crew perished. ... Preliminary exam by bomb disposal officer says a miracle that one Mark Six with exposed detonators sheared didn't go." Gen. Walsh refers to the risk of the bombs' high-explosive charges being set off by the fire, spreading radioactivity over the area.

A Defense Department description of the accident says "no capsules of nuclear materials were in the weapons or ... the building."

Using remote-control handling equipment in an isolation box, H. E. Northway, manager of the Houston plant of M. W. Kellogg Co., opens a can containing ten pellets of Iridium-192. He and another employee are in the room. They discover that two of the pellets are "powderized" but apparently do not report this fact to the AEC. Some of the dust escapes the box and at least one of the two employees becomes contaminated. Although the company is licensed by the AEC to encapsulate sources for radiographic cameras, the agency does not learn of the problem for five weeks.

The event is reported in the 13 May 1956 issue of Time (and reportedly by Look Magazine in 1961.) By then, at least eight private homes and seven automobiles have been contaminated. Only the two employees suffer radiation injuries, but press coverage leads to ostracism of plant workers in their community and widespread public fears of radioactivity.

At the Rocky Flats weapons facility 27 km from Denver, CO, finely-divided plutonium powder in a glove box begins to spontaneously combust about 10 PM. The fire is not immediately noticed, and soon the plastic glove box ignites. The ventilation system pulls burning fragments through the building's air ducts to the paper stack filters that keep contamination inside. The filters are damaged, allowing plutonium and other contaminants to escape the plant. Firefighting efforts begin at the glove box at 10:38. The filter fire is detected later and put out by 2 AM on 12 September.

Research done in 1999 finds that approximately 63 kilograms (kg) of plutonium were in the room where the fire occurred and that 13-21 kg were actually involved in the fire. This leads to an estimate that between 40 and 500 grams of plutonium were carried off the site by wind currents. (Another source reports the amount of plutonium lost as 25,618 micrograms, but this seems suspiciously precise.)

Cooling system failure causes an explosion in a waste storage tank at the Mayak nuclear fuel complex near Chelyabinsk, Russia. The force of the explosion is estimated to equal that of 75 tons of TNT. It releases approximately 20 MCi (700 PBq) of waste, exposing (by various estimates) 124,000 to 270,000 people to dangerous levels of radiation.

This event, known as the "Kyshtym Disaster", is merely the best known of a series of releases that both precede and follow it. More than 500,000 inhabitants of the region are affected, both by direct exposure and through contaminated water supplies. It is known to the U.S. government but withheld from the public until 1977, when a Freedom of Information Act (FOIA) request breaks it free. Russia does not admit it until 1992, when Glasnost (openness) takes hold.

During an operation to release Wigner Energy from the graphite portions of Windscale Pile No.1 at Sellafield, north of Liverpool, England, technicians mistakenly overheat the reactor pile because poorly placed temperature sensors indicate it is cooling rather than heating. The resulting fire burns four days in the air-cooled pile, consuming a significant portion of it. A deluge of water finally cools the pile and quenches the blaze.

Radiation levels in the area are comparable to those from the 1979 meltdown at Three Mile Island in the U.S. Milk distribution is banned in the 200 square miles surrounding the plant. Both Pile No. 1 and No. 2 are later shut down and decommissioned in an effort that lasts until 1999.

A B-47 carrying a nuclear weapon, with its fissile core in a separate container for safety, crashes just after takeoff into an inhabited area 3,800 feet from the end of the runway at Homestead AFB, Florida. Enveloping the weapon and its core, the fire burns and smolders for four hours.

Afterward the fissile core is recovered intact in its shipping container. Just half the nuclear weapon remains, but all its major components are recovered in damaged condition. Nothing is reported about radiation levels in the area.

Near Savannah, Georgia, a B-47 collides with an F-86 fighter during simulated combat. The damaged bomber attempts three landings at Hunter Air Force Base, but cannot land safely with its cargo: a nuclear weapon with no plutonium core. The crew jettisons the bomb from 7,200 feet over water near Tybee Island; it is never recovered.

Note: Lutins puts the date of this accident at 25 May 1958.

Shortly after taking off from the U.S. air base at Greenham Common, England, a B-47E of the 310^th Bomb Wing develops problems and jettisons its two external 1,700-gallon fuel tanks. Both tanks miss their designated safe impact area. One hits a hangar; the other strikes the ground 65 feet behind another B-47E parked on the tarmac. The parked B-47E, carrying a B28 1.1-MT hydrogen bomb and with a pilot aboard, is engulfed by burning jet fuel. The fire ignites parts of the parked aircraft's magnesium fuselage and sets off the B28's high explosive charges. Two men are killed and eight injured. Convection currents distribute plutonium and uranium oxides over a wide area. Sixteen hours and a million gallons of water are needed to put out the fire.

The American and British governments throw a blanket of secrecy over the event. As late as 1985, the U.K. claims that a taxiing aircraft struck a parked one, and that no fire was involved. However two scientists with the Atomic Weapons Research Establishment at Aldermaston, F. H. Cripps and A. Stimson, working independently, discover high levels of radioactivity around the base in 1960. Their report on the accident remains under wraps until 1996.

In the reactor at the Boris Kidrich Institute in Vilna, Yugoslavia, a subcritical foil counting experiment is in progress. The operators desire the maximum foil activation, so the reactor is run as close to critical as possible. After about 5 minutes, one of the operators smells ozone and realizes that the reactor has gone critical. Of the three neutron flux sensors, two are indicating steady power level. The third is disconnected after behaving erratically. It is later found that the two working sensors have reached saturation, while the power level is ramping up.

The reactor reportedly withstands the burst energy of about 2.6x10¹⁸ fissions (80 MJ), but the six operators present are strongly irradiated, receiving estimated doses of 200 to 433 rem. One dies; the other five recover after severe bouts of radiation sickness.

The cause turns out to be control instrumentation failure. A newly added noise filter in the high voltage line to the ion chamber is sensitive to high neutron flux, dropping the chamber's voltage as the flux increases and thus mis-leading the servosystem. In the excursion, of about 2.5x10¹⁹ fissions, all core fuel elements experience some melting. Some fission products escape the building, but operator personnel exposures apparently are negligible.

At the Santa Susana Field Laboratory 30 miles northwest of Los Angeles, Rocketdyne operates the 20-MW Sodium Reactor Experiment (SRE) for the AEC. SRE is a prototype of a high-temperature liquid-metal-cooled reactor for civilian applications. A cooling channel becomes blocked. This causes 30% of the fuel elements in the core to melt. Most radionuclides are contained in the reactor building; only some krypton and other noble gases are released, after being held for a time to allow their activity to diminish. Of the nine radiological incidents at SSFL, this is the only one from which detectable radioactivity is observed off-site.

The Santa Susana Field Laboratory opened in 1948 and operated to circa 1989. Rocketdyne Corporation used it primarily to test rocket motors; but ten research reactors (all but SRE under 1 MW output) and seven criticality test setups were operated in Area IV. Over the years, the site became contaminated not only with radionuclides but with trichloroethylene, mercury and hydrazine. Workers were also irradiated at the site, and studies done in the 1990s document a statistical correlation between cumulative doses and cancer rates among these workers. It should be noted that weather and topographic factors limit the spread of contaminants into surrounding populated areas.

A chemical explosion occurs during decontamination of processing equipment at the radiochemical processing plant at Oak Ridge. The cause is thought to be hot nitric acid mixing with phenol left in an evaporator which, contrary to procedures, has not been flushed with water. No injuries result, but the building is extensively contaminated, and radiation escapes it to wind up on surrounding streets and the exteriors of nearby buildings. An estimated 15g quantity of plutonium-239 is lost.

Areas that cannot be decontaminated are covered with concrete or bright warning paint. Subsequently, all radiochemical processing apparatus is fitted with secondary containment.

Falsification of log entries leads to an unusual criticality accident at the Mayak Production Association. During plutonium purification operations, a technician working alone begins transferring plutonium carbonate solution into a holding vessel. He notices a criticality alarm sounding intermittently and exits the room but leaves the transfer going. Soon, the alarm is sounding continuously.

A radiation protection crew arrives. Their instruments measure a flux of 18 R/hour in a corridor near the room. Continued monitoring reveals an average level of 1.5 to 1.8 R/hour with oscillations to tenfold higher levels. It is thought that the oscillations are caused by the transfer pump periodically delivering just enough solution to induce criticality in the holding tank, whereupon a buildup of heat and pressure overcomes the pump and forces some solution back out. Attempts to distribute the solution into separate vessels and stop the oscillating criticality do not succeed until the following day.

Subsequent investigation reveals that a supervisor on a previous shift under-reported the amount of plutonium left in the holding vessel. During the accident and cleanup, five individuals receive doses of between 0.24 and 2.0 rem. Although the task of cleanup and recovery of plutonium from the apparatus is arduous, no contamination results and the equipment suffers no damage.

After operating for two years, the 3-MW SL-1 reactor at the National Reactor Testing Station in Idaho has been down for routine maintenance over the Christmas 1960 holidays. The three-man crew on duty the night of 3 January is preparing it for full-power operation the following day. Apparently, for reasons unclear, one operator withdraws the central control rod from the core as rapidly as possible. The excursion reaches a peak power of 20,000 MW and produces 130 Megajoules of energy. The resulting steam explosion destroys the reactor, lifting the entire core 9 feet before dropping it back in place. Two of the operators are killed instantly; the third is critically injured. Cooling water spreads intensely radioactive fission products throughout the building. Some contamination escapes into the local environment. Most of it settles within a 3-acre zone outside the building, but iodine-131 levels 100 times normal are found in vegetation 20 miles from the site.

Entering the building is extremely hazardous due to radiation levels of 500 to 1,000 R/hour. Search for the three victims is done by site personnel working in relays. The survivor is removed promptly; he dies a few hours later of massive head injuries. Due to higher priorities, the other two bodies are left in place for a few days. (One of those two is found on the ceiling of the reactor room, impaled there by the control rod.) Investigation and cleanup are similarly hampered; but within a few months the reactor is dismantled and its pieces safely buried on site.

A B-52 develops a leak in an in-wing fuel tank. A fire erupts, causing the plane to break up in midair and crash 12 miles north of Seymour Johnson AFB in Goldsboro, NC. The bomber's two 24-MT Mark 39 hydrogen bombs are released. One of the bombs deploys its parachute and lands relatively undamaged. The other plunges into a muddy field and disintegrates. Three of the plane's 8 crewmen are killed in the initial explosion; the other five parachute to safety.

Investigators find three of the intact bomb's four arming devices have activated. Only the pilot's safe/arm switch has prevented a detonation. Much of the other bomb is recovered, but the thermonuclear stage has penetrated to an estimated depth of 180 feet, and groundwater flooding prevents excavation. The Air Force purchases the plot of land and fences it off, monitoring periodically for contamination. None is reported.

CPP-601, the Idaho Chemical Processing Plant's main building, is five days into renewed operations following a year-long shutdown. In an evaporator system, a concentrated solution of enriched uranium is forced back up into the reservoir from which it flowed. The reason is unclear; a bubble of high-pressure air is suspected. The resulting criticality sets off alarms and all personnel evacuate the facility, with exposures of only 60 mrem or less. The criticality ends a few minutes after it began at 0950. Work is allowed to resume at 1445.

Continuous air monitors are the only instruments from which any data can be obtained, and their data are not of much use for determining either intensity history or total energy. Thus the parameters of the event are poorly known; but yield is estimated as 6x10¹⁷ fissions. Evaluation suggests that causes of the accident include unfamiliarity of personnel with equipment after the long shutdown, and the poor operating condition of some equipment.

K-19, a Soviet Hotel-class submarine, suffers a major accident off Norway after a leak in a pipe causes its reactor cooling system to fail. Reactor core temperatures reach 800°C, nearly hot enough to melt the fuel elements. But the crew, working in a dangerously radioactive compartment, is able to prevent this by rigging an emergency cooling system. The accident contaminates the crew, parts of the ship, and some of the ballistic missiles it carries. Eight of the crew die from acute radiation sickness before help can arrive. When it does arrive, the surviving crew transfer to another submarine and the K-19 is towed back to the Kola Peninsula.

Through a complex sequence of events, a significant quantity of U-235 (in the form of UF6) accumulates in the oil reservoir of a vacuum pump driving the gas purifier of the number 6 desublimation-sublimation stage (DSS-6) of the gaseous diffusion plant at the Siberian Chemical Combine. The oil is normally changed each 15 days because the UF6 lowers the efficiency of the vacuum pump. On this date, equipment breakdowns elsewhere in the diffusion cascade cause DSS-6 to work harder than normal. A high-radiation alarm activates at 0445. Per procedure, the operator shuts the pump down and summons the radiation control officer. The RCO cannot locate the source of radiation. He does not check the pump room, basically because he dismisses it as a possibility. Radiation flux in the control room measures about 9 mR/h and decreasing. He authorizes resumption of operations.

At 0730 the operator turns on the pump. The criticality alarm sounds almost immediately and the operator sees a flash of Cerenkov radiation. He turns off the pump and runs to a telephone to report. This time, the RCO finds 36 mR/h at the exterior of the DSS-6 building, He sends the operator to the hospital, where his exposure is estimated as 200 rad. He suffers mild radiation sickness and recovers. Investigation discloses the causes of the first and the much larger second excursion. They are too complex to describe here.

In mid-October, a USAF Jupiter mobile intermediate-range ballistic missile (IRBM) is struck by lightning at its launch site near the Gioia del Colle Air Base in Italy. Three other nearby missiles are struck on different dates through August 1962. In each case, the missile's thermal batteries are activated, and on two occasions tritium-deuterium gas is injected into the "pits' of the 1.4-MT warheads, partially arming them.

After the fourth strike, the Air Force places lightning diversion towers at all Jupiter missile sites in Italy and Turkey. (It is noteworthy that the deployment of these IRBMs prompts the USSR to place similar missiles in Cuba, bringing on the "Cuban Missile Crisis" of October 1962.)

The fission yield is between 10¹⁵ and 10¹⁶ fissions. This range is confirmed by the fact that the paraffin does not melt and the surface of the uranium is unmarred. No significant personnel exposures result, and the laboratory returns to normal use within 1.5 hours.

Sometime in 1961, a Soviet nuclear ballistic-missile submarine of early design (probably a Hotel class) is operating near the coast of England when a coolant pipe breaks. The level of radiation is reportedly 5R/h at the break. The flooding coolant spreads radiation to several parts of the ship, including its missile tubes. Crew members are seriously contaminated. The ship is able to return to port where, after a two-month ventilation, its missiles are transferred to two diesel-powered submarines for their test launches.

Though it is not credited, this is clearly a CIA report. The date is indicative.

In the Recuplex system process plant at the Hanford Works, operator error apparently contributes to a later excursion in a plutonium solution. The solution overflows a receiver tank and winds up on the floor of a solvent extraction hood and in the sump. The operator, contrary to orders, opens a valve that allows this spilled material to be lifted into a transfer tank. Later addition of more plutonium solution and subsequent moderation following mixing or de-aeration of the tank cause the excursion. An initial spike of 10¹⁶ fissions is followed by 37.5 hours of steadily decreasing emission, for a total yield of 8x10¹⁷ fissions. As it is a Saturday morning, only 22 people are in the plant. They all evacuate promptly when the criticality alarm sounds. Three receive significant doses of 110, 43 and 19 rem.

Witness testimony does not fully jibe with the technical findings about this accident, so the above reconstruction should be regarded as the best plausible explanation. The accident causes no damage to equipment and no contamination release. However, it does bring about the final shutdown of the plant. (This has already been planned, since a new production facility is approved.) The first use of an instrumented and television-equipped remotely-controlled vehicle occurs during the investigation of this accident.

The second Thor launch in Operation Dominic is called Starfish. It ends like the first Bluegill test. The missile malfunctions and is destroyed by the RSO at 65 seconds. Its nuclear warhead, a W-49 type rated at 1.45 MT, does not detonate but is destroyed by its high-explosive triggers. Debris including plutonium contaminates both Johnston Island and Sand Atoll.

Note: The Starfish Prime test on 9 July is successful. However, this detonation at 248 miles altitude is notorious for EMP effects which cause electrical outages on Oahu.

This accident occurs at the Mayak Production Association in a facility where plutonium feedstocks are purified and cast into ingots. The residues from this operation include slag that contains recoverable quantities of plutonium. Recovery involves using nitric acid to dissolve the plutonium metal in the residue and performing other chemical processing.

The cause is the usual one of inadvertently allowing too much solution in a single container. The criticality triggers an alarm and all personnel evacuate. Operating valves, heaters and stirrers remotely from the shift supervisor's control room, operators bring the situation under control in about an hour. During this time two other excursions occur, the third being the largest. It is discovered that 1,324 grams of plutonium, both solution and precipitate, have accumulated in the vessel. Dose rates measured at the glove box containing this vessel average 2R/h. Total yield is estimated as 2x10¹⁷ fissions. Worker exposures are negligible. Some solution is forced onto the floor of the glove box, but no equipment damage occurs and cleanup takes only a short time.

Bluegill Double Prime is the third failure of a Bluegill test and the fourth malfunction of a Thor IRBM in Operation Dominic. In this case, the RSO destroys the missile at 156 seconds. Its nuclear warhead does not detonate but is destroyed by its high-explosive triggers. Some plutonium contamination of Johnston Island occurs.

Note: Bluegill Triple Prime is a success on 26 October. The missile carries its warhead to 31 miles altitude, where it detonates.

A train of the Louisville & Nashville Railroad derails near Marietta, GA while carrying nuclear weapons components. These are not damaged, but three couriers are injured in the derailment.

Note: At a December 1962 AEC symposium in Germantown, MD, a report is presented that lists 47 accidents involving nuclear materials. The report calls 17 of them "serious".

Mistakes by two different operators on different shifts are the cause of this accident in a uranium metal production building at the Siberian Chemical Combine. The process involved is similar to that cited in Incident 095 for plutonium recovery: dissolving the waste in nitric acid, followed by further chemical processing.

The first error is made because the facility uses two different formats for recording uranium mass per batch: as a mass fraction (that is, the uranium-to-precipitate mass ratio) or as grams of uranium per kilogram of precipitate. The latter is the format used where the accident occurs. Two waste containers are received for processing. The attached analysis forms record the uranium mass fraction of 0.18. The shift supervisor transcribes this as 18g/kg on his work orders, instead of 180. Referring to these work orders, an operator loads 2 kg from one container and 5kg from the other into a processing tank. Thus he is processing ten times more uranium than he thinks he has in his tubes and tanks. The actual amount is 1,260 grams of Uranium. He begins dissolving the precipitate with acid. Then a shift change occurs.

The oncoming operator completes the dissolution. Per normal procedures, he takes a sample and sends it to the lab for a concentration check. Later he telephones for the result. This should reveal the original error. Unfortunately, by coincidence, he's given the result for another sample — one with a ten times lower concentration.

Next, the supervisor for that shift decides to recycle the solution for the next batch of precipitate. This too is normal procedure. The same transcription error is in effect, and another 1,225g of uranium are added. Thus the vessel holds over 2.5kg of uranium, an amount close to critical mass for its geometry.

Ultimately, criticality does occur. Four people standing 10m from the vessel receive doses of 6 to 17 rad before they evacuate in response to the alarm. Over the next ten hours, eight more excursions take place in the vessel. The cycle is broken on 31 January by draining part of the solution to another container. No damage to the vessel occurs and there is no contamination of the area. Based on lanthanum-140 in samples taken afterward, the total yield is 7.9x10¹⁷ fissions.

Researchers at Lawrence Livermore Laboratory are doing multiplication measurements on various configurations of uranium and reflectors. As is common, the reflector is mounted to a stationary support and a lift table is used to raise the uranium sample into proximity with it. The apparatus is located in a heavily shield vault.

This particular experiment involves moving the uranium closer in steps, making a measurement each time. Seven steps have been done with complete safety. On the eighth, the system unexpectedly goes highly supercritical. An explosive sound is heard, the scram activates, and alarms sound. After a few seconds, the uranium can be seen melting and burning. About 15kg of uranium burn. Another 10kg melt and spread over the floor. The reactor room is heavily contaminated.

No dose to anyone in the building exceeds 0.12rem. The yield is later measured as 3.67x10¹⁷ fissions. The cause of the excursion is thought to be a mechanical misalignment: The central cylinder is slightly off-center. When raised into the reflector, it carries the rings upward with it — until the eighth step, when the cylinder shifts back toward centerline and the rings fall down around it.

The nuclear attack submarine USS Thresher (SSN-593) has just been refitted and is undergoing sea trials in the Atlantic about 220 miles east of Boston. During a deep dive, the vessel sinks in 2,600 meters of water with loss of all 129 hands. It is thought that the silver-solder joint of a pipe fails, resulting in uncontrollable flooding of the vessel's interior. Such joints have failed during destructive testing in the shipyard.

Six pieces of the Thresher are later photographed on the sea bottom. The reactor compartment remains intact and no radiation leakage from it has been detected.

A vacuum system in a facility at the Siberian Chemical Combine is protected by traps. Operations inevitably introduce droplets of solutions into the system. The corrosive chemicals involved in reprocessing can attack the components of the vacuum system, and any solutions that collect within it represent loss of product. To prevent large accumulations within the traps, they are fitted with level sensors that trigger drain valves as needed. These sensors operate when the solutions touch pairs of electrodes, allowing a current to flow. They are designed for processes that use water solutions, which always conduct electrical current. Unfortunately, the facility is doing a mix of processes: some use water solutions, while others use organic solutions which are at best weakly conductive.

First-stage traps in this particular setup typically fill to the trigger point four times per day. They then drain some liquid into a larger, second-stage trap. When that fills to the preset level, it is drained back into the processing stream. The first-stage traps contain some aqueous solution, but also an organic solution of lower density, which floats on top of the aqueous. Thus, draining is triggered only when the level of aqueous rises high enough.

The criticality occurs in the large trap, which has not drained in 8 days. An alarm sounds and employees are evacuated from the area. The trap is found to hold a large quantity of organic solution containing enriched uranium. Over the next 16 hours, a series of relatively weak excursions takes place at intervals. Total yield is 6x10¹⁶ fissions. The accident is ended by manually siphoning the liquids into smaller reservoirs. Fortunately, this vessel is located in a corridor not frequented by employees. The largest dose to anyone is under 5 rem. The accident results in replacement of the traps by an improved system and in redesign of some processes.

A B-52D is carrying two nuclear weapons from Westover AFB in Chicopee Falls, MA to its home base at Turner AFB in Albany, GA. This is a tactical ferry flight, meaning that the weapons are merely stored aboard the aircraft for transport; they are not mounted and connected as droppable bombs.

About halfway through its flight, the bomber encounters violent turbulence at 29,500 feet. It attempts to climb to better conditions at 33,000 feet, but encounters worse turbulence and suffers structural failure. It crashes 17 miles southwest of Cumberland, MD. The two bombs are recovered "relatively intact".

A chemical plant at Wood River Junction, RI is designed to recover highly enriched uranium from scrap material left over from reactor fuel element production. This is the United Nuclear Fuels Recovery Plant. It begins operations on 16 March 1964. The plant receives the scrap as uranyl nitrate solution, concentrates it, purifies it, and finally bubbles it through a tank of the solvent trichloroethane (TCE) to remove other organic solvents used in processing. A single charge of TCE is expected to last 6 months or more; but experience shows that the limit is one week, due to the rate at which it picks up uranium.

A procedure is developed to reclaim the uranium (still a very low concentration of 400 to 800 ppm) from the TCE before discarding it by washing it with sodium carbonate solution. Originally this is done manually by shaking the mixture in 11-liter bottles. On 16 July, though, a large amount of TCE has accumulated. An operator is given permission to begin washing it in a large stationary vessel. This variation is taught to an operator on a different shift, and by 24 July the two operators have washed 10 to 12 bottles each. The sodium carbonate solution remains in the large vessel, its uranium concentration slowly rising.

Concurrently, someone else dissolves a plug of uranium nitrate crystals out of an evaporator hose, putting the concentrated solution in bottles identical to those used in the TCE wash. These bottles ARE labeled as highly concentrated. Nevertheless, one of the wash operators mistakes one for a bottle of contaminated TCE and pours it into the large vessel to wash it. Immediately there is a flash, the radiation alarm sounds, and about 20% of the solution splashes onto the walls, the ceiling and the operator. He gets up and runs to an emergency building.

Ninety minutes later, the plant superintendent and a shift supervisor enter the building. The superintendent removes the bottle, still upended over the tank, and turns off the tank stirrer. Unknown to these men, since the radiation alarm is still sounding, a second excursion occurs when the tank's liquid slumps into a new geometry. This is discovered when their doses, 100 rem and 60 rem respectively, are found to be much higher than expected. The original excursion imparts a 10,000 rad dose to the operator; he dies 49 hours later. Total yield is 1.30±0.25x10¹⁷ fissions. The equipment is undamaged; the room is decontaminated.

The staff at Building 242 of the Electrostal Machine Building Plant are changing over their uranium oxide production process from 2% to 6.5% enriched uranium. The line shuts down on 19 October and everything is thoroughly cleaned over the next three days. The accident occurs when flakes of uranium oxide enter the vacuum system and collect in a vacuum supply vessel. The alarm sounds at 11:10 and Building 242 is immediately evacuated. The facility's chief physicist enters 50 minutes later and measures a gamma exposure rate of 3.6R/h at 1.5m from the vacuum supply vessel. Fission yield falls between 5x10¹⁵ and 10¹⁶. One person may have received a dose of 3.4 rads.

Careful recovery operations are taken to divide up the mass of uranium. It is determined to hold 4.6kg of U-235. Investigators determine that sometime after production resumes on 22 October, the primary filter goes missing from the vacuum duct, and the secondary filter is improperly fastened. These filters are supposed to be checked once per shift. Also, each shift is required to take a water sample from the vacuum system and have it checked for uranium concentration. This has not been done since production resumed.

The aircraft carrier USS Ticonderoga is traveling from station off Viet Nam to its base at Yokosura, Japan. Somewhere between these two locations, an A4-E Skyhawk strike fighter carrying a B-43 hydrogen bomb rolls off the carrier's elevator and plunges into the sea at a point where it is 16,200 feet deep. Neither the bomb, the plane, nor its pilot is ever recovered.

One source claims there is concern at the Pentagon that water pressure at that extreme depth will cause the bomb to detonate, and adds that whether or not an explosion did occur is unknown. Neither seems very likely.

More substantial concerns drive the dispute over exactly where this incident occurs. Japan's law forbids nuclear weapons on its territory, including U.S. bases on that territory, so admitting the Ticonderoga carries such weapons would underscore a violation of U.S. military agreements. It would also be an admission that we deployed nukes to Viet Nam.

Lackadaisical record keeping is the cause of a criticality accident at the Mayak Production Facility It occurs in the residue recovery area of a metal and fissile solution processing building. On the day before the accident, a supervisor directs an operator to process batch 1726 in equipment intended for material with less than 1% uranium content. This is a rules violation, since 1726 contains more than 1%. After the process completes, 1726 is transferred to another glovebox which already holds multiple batches of residue. It is analyzed and its 44% by-weight concentration is noted in the log but not conveyed to the central data registry.

Another operator, set to begin the next processing step, notices that the figure for batch 1726 is missing from its accountability card and calls the laboratory to obtain it. He is given by mistake the result for batch 1826: a concentration 138 times smaller. The second operator properly records this on the card attached to batch 1726.

The next day, during dissolution of the residue, these errors result in a criticality alarm. The operator leaves the area and goes to the central control room. There, alarms begin sounding for progressively distant sensors. The vessel responsible is soon identified; it is supporting multiple excursions and emitting an average level of 8R/h at a distance of 2m. The usual recovery procedures are judged too time-consuming for this case. Emergency personnel develop an alternate plan, each step of which will be done by a different person and take no more than 30 or 60 seconds:

1. Remove two gloves from the glovebox to gain access.
2. Unlock and open the feed hopper lid.
3. Drop a crumpled-up ball of cadmium foil into the solution to poison the fission reaction.

This plan works. No one receives a dose greater than 0.3 rad. The next day, the solution is transferred into safe containers and sent to a special facility. It is later reprocessed after the cadmium is removed. Total yield of the event is 5.5x10¹⁷ fissions, from 11 excursions. The facility is back in operation several days later.

The VENUS reactor is a tank-type, water-moderated, critical assembly machine in a laboratory at Mol, Belgium. It is fueled by 1,200kg of uranium oxide with an enrichment of 7%. Fission regulation is done by 2 control rods and 8 safety rods, all remotely controlled by an operator. An additional 8 rods are provided; these must be manually adjusted and locked down.

On this date the operator decides to change over to a new rod pattern. By means of written instructions, he directs a technician to insert a new manual rod and remove another. The rod configuration is such that the reactor should be subcritical by 1 safety rod, 2 control rods and 1 manual rod. (The last control rod is being inserted into the core by its mechanism.) The operator overlooks the requirement that the water should be drained before any manual rods are adjusted. The technician does not wait for the slow insertion of the final control rod; he also reverses the sequence in his instructions, removing one manual rod before inserting the other. The reactor goes critical at this point. He leaves the room immediately on seeing the flash, but already has received a severe dose, primarily of gamma rays. The energy release is 4.3x10¹⁷ fissions — not enough to cause damage or even a steam explosion in this particular reactor. Because of his position leaning over the assembly, the technician's exposure is highly uneven. Estimates are that his head receives 300 to 400 rem, his chest 500, his left ankle 1,750, and the end of his left foot 4,000. He is treated in hospital and survives, but his left foot does not.

During in-flight refueling near Palomares, Spain, a B-52 collides with a KC-135 tanker aircraft. Eight of the 11 crewmen aboard the two planes are killed. The B-52 splits in two, and the KC-135 goes down in flames, its 40,000 gallons of extra fuel contributing to the blaze. Wreckage rains down on an area of land and water 100 square miles in extent. One of the B-52's four hydrogen bombs, having deployed its parachute, lands intact near Palomares. Two others fall freely; their HE charges explode on impact, scattering radioactivity over nearby farms. The fourth bomb plunges into the Mediterranean Sea 12 miles off the coast.

During the ensuing cleanup, 1,400 tons of lightly contaminated soil and vegetation are dug up and shipped to a nuclear waste dump at Aiken, South Carolina for disposal. The U.S. settles claims by 522 Palomares residents for $600,000, and gives the town a $200,000 desalination plant.

The weapon lost in the Mediterranean sets off one of the largest search and recovery operations in history. It involves 3,000 Navy personnel and 33 vessels, not counting the ships, planes and people providing logistics and other support. (One source reports a total of 12,000 people.) The submersible Alvin locates the bomb after two weeks, but it is not recovered until 7 April. The whole effort takes 80 days, and is later fictionalized in the film Men of Honor.

A B-52 from Plattsburgh AFB in New York is flying the Arctic Circle Route as part of the Strategic Air Command's continuous airborne alert program, code named "Chrome Dome". When fire breaks out in the navigator's compartment, the pilot attempts an emergency landing at Thule Air Base in Greenland. The plane crashes 7 miles south of Thule, becoming completely engulfed in flames on impact. The fire detonates the HE triggers on at least one of the plane's four nuclear bombs, spreading radioactive debris 300 yards to either side of the plane's path.

The government of Denmark, which owns Greenland and prohibits nuclear weapons on or over its territory, issues a strong protest following large demonstrations in that country. A few days later, U.S. Secretary of Defense McNamara orders the removal of nuclear weapons from airborne alert. The alerts themselves are later curtailed and then suspended altogether.

During a cleanup complicated by Greenland's harsh weather, tons of contaminated ice and crash debris are shipped to the U.S. and buried. Bomb fragments are recycled at the Pantex plant in Amarillo, TX. Navy Seals and Seabees recover one warhead in 1979. An August 2000 report suggests that another lies on the bottom of Baffin Bay.

Using a very highly enriched solution of uranyl nitrate (97.6% U-235), researchers at Oak Ridge are conducting experiments to determine the critical concentration of solution in a thin aluminum sphere with a thick water reflector. The sphere is connected by a flexible hose to a cylindrical reservoir. Solution height in the sphere is adjusted by raising or lowering the cylinder.

After a measurement, an attempt to pull the sphere back subcritical by lowering the cylinder is ineffective. Upon inspection, an air bubble is seen in the hose. Enough solution is drained into a third container to bring the shpere subcritical. Then the cylinder is jostled in an attempt to remove the bubble. The system suddenly goes critical again. It is thought that the air bubble broke free after the jostling ended, pushing enough solution into the sphere to drive it critical.

The excursion expels approximately 90 ml of solution out of the sphere and onto nearby equipment. The yield is found to be 1.1x10¹⁶ fissions. The modest cleanup required is accomplished promptly. A simple modification fixes the problem of air bubbles in the connecting hose.

Chelyabinsk-70 is part of the Russian Federal Nuclear Center (VNIITF), located in the southern Ural mountains between the cities of Etakarinberg and Chelyabinsk. Intensive work is under way there to develop powerful reactor-based neutron sources for radiation-tolerance studies.

Two nuclear criticality specialists are working overtime on a Friday evening to complete a second assembly on a FKBN lift mechanism. This is to be a duplicate of one constructed during the day — with one exception: a polyethylene sphere is to fill the central space which in the earlier assembly is empty. While the senior specialist uses a handheld control to lower the upper half of the reflector, the junior specialist stands by to guide it into place. The accident occurs as the reflector is about to make contact with the core. There are no criticality alarms installed at this time, but a scram system immediately drops the core, terminating the reaction.

Both men remain conscious and retain their self-control. They are able to report the accident and to call for an ambulance. The senior specialist carries out dose estimates for himself and his assistant and writes the details of the event in his personal log. The senior specialist's dose is in the 5-10 Sv range; the junior gets 20-40 Sv. Both are taken to the local hospital and immediately flown to the Bio-Physics Institute in Moscow. The junior specialist dies three days later; the senior specialist survives for 54 days.

Investigators conclude that, in addition to underestimating the effect of the polyethylene sphere, the senior specialist violated several rules, and that both men were guilty of overconfidence and excessive haste.

K-129, a diesel-powered Soviet submarine of the Golf-II class, sinks in 16,000 feet of water 750 miles northwest of Oahu. The vessel takes 80 sailors with it to the bottom, as well as three SS-N-5 ballistic missiles and (probably) two nuclear torpedoes. The cause of the sinking is thought to be an internal explosion, perhaps due to hydrogen from the ship's storage batteries. (The Soviets asserted that the USS Swordfish (SSN-579) was the cause; some Russians still believe this. The Swordfish was shadowing K-129, and it did undergo secret nighttime repairs at Okinawa shortly after K-129's loss.)

The U.S. Navy's SOSUS underwater listening system gives them the area where K-129 sank. In 1969, the exact location of the wreck is discovered by the USS Mizar (T-AK-272). It is then surveyed by USS Halibut (SSGN-587) and the bathyscape Trieste II. The CIA begins Project Jennifer to recover the submarine for analysis, and commissions a mining company owned by Howard Hughes to build a vessel that can raise it. On 12 August 1974, Hughes' Glomar Explorer brings the hulk halfway home, but it breaks apart. The engine room and torpedo rooms are lost, and only the center section is recovered. The ballistic missiles too reportedly fall back to the seabed.

Thus, the CIA missed out on the "good parts"; but what was retained is still classified. Indeed, much mystery remains. High-level sources hint at an informal agreement not to tell the full story of the sinking, or that of the USS Scorpion (SSN-589) in May 1968.

Note: The date of this event is somewhat ambiguous. Sources claim 8 March or 11 April 1968, and a Russian Web page says 1967.

The nuclear-powered attack submarine USS Scorpion (SSN-589) is returning from a three-month training exercise in the Mediterranean Sea to its base at Norfolk, VA. It sinks 400 to 500 miles southwest of the Azores, taking with it 99 sailors and two Mark 45 ASTOR nuclear torpedoes.

The wreckage is later photographed at its 10,000-foot depth by the research vessel Mizar (T-AK-272). No evidence of sabotage or foul play is found, laying to rest suspicions that the Soviets are somehow involved in the sinking. The Navy continues to monitor the wreck for leakage from its reactor. None has been found to date.

The Soviet submarine K-27, a modified November-class equipped with two VT-1 type reactors, is undergoing sea trials. Reactor power suddenly drops, and the crew are unable to restore normal power output. At the same time, gamma radiation levels in the reactor compartment rise to 150R/h and radioactive gases vent into it from the safety buffer tank. The reactor is shut down and the crew are taken off the boat.

Investigation shows that 20% of the core has melted due to a problem in the reactor's liquid-metal cooling loop. The heavily contaminated submarine is deemed beyond economical repair. It is scuttled in a shallow area of the Kara Sea in 1981.

A fire in a glove box at Rocky Flats consumes 5kg of plutonium, releasing significant contamination onto the grounds of the facility. Hundreds of railway cars are used to transport the contaminated soil to Idaho Falls, where it is left in unlined trenches.

The Colorado Committee for Environmental Information deploys a team of scientists with sophisticated instruments, putting officials on notice that the public now has the capability to discover and report releases of radiological contamination. The Committee's work in response to the fire provides evidence of a years-long buildup of wastes on the grounds of Rocky Flats.

Cruising roughly 300 miles northwest of Spain, the November-class nuclear submarine K-8 (see 13 Oct 1960) is taking part in a large Soviet naval exercise known as "Okean 70".

On 8 April, fires break out in compartments 8 & 9, asphyxiating 19 men. The sub surfaces so the crew can fight the fires. Automatic systems have shut down the reactor, so radiation is not a problem. However, the emergency generators cannot be started, so there is no electrical power to pump air into the ballast tanks. The stored compressed air that is keeping K-8 afloat runs out on 10 April. By this time, surface ships are standing by. U.S. Navy P3 antisubmarine patrol planes observe the K-8 lying dead in the water, with crew members on deck trying to rig a tow line to one of the ships. Late in the day, most of the crew transfers to these ships. But Moscow orders them back aboard to save K-8.

K-8 is taken under tow, but the tow cable snaps in heavy seas. At 0620 the next day, the stricken submarine sinks in 4,680 meters of water. Her captain and 22 crewmen go to the bottom with her. When the P3s arrive during full daylight, they find nothing but an oil slick at the location.

Soviet vessels stand sentinel duty over the K-8 for at least 6 months, and regular patrols visit the site until 1979. It is presumed this is to keep western military forces from attempting salvage.

At Cumbria in the north of England, the Windscale plant is used to recover plutonium from scrap. Windscale is thought to be a well-run operation, with effective safety features. One of these is a deep trap: a loop of hose that drops 25 feet from the transfer vessel, then comes back up to feed solution to the next stage of the process. Its purpose is to prevent backflow. The differential is achieved by having the transfer vessel 8 feet above the top of the trap.

When a brief, relatively small excursion is detected in a transfer vessel, it presents a mystery. It is known that the amount of plutonium in the batch is too small for critical mass, so the theory is that precipitate must have somehow collected in the vessel. Disturbing any such sediments might precipitate another and greater excursion.

A 6-inch hole is drilled in the ceiling and used as access to open the vacuum line going into the transfer vessel. Inspection is done with a fiber-optic probe developed especially for this problem. The vessel is found to contain just liquid, but both aqueous and organic solutions are present. The trap is found to hold 39 liters of organic solution that has been there for several months and perhaps as long as 2 years. Through that time it has been leaching plutonium from the aqueous solutions that passed through; it now contains a total of 2.15kg. Although the source does not provide every detail, it is clear that this is just a "red herring": the true answer to the puzzle is that when some aqueous solution has poured into the transfer vessel, it forms an emulsion with the organic — much like the oil & vinegar you shake for your salad dressing. When the pouring stops, the emulsion spreads out in a layer, making a favorable geometry that is just above critical. Then, over 10 seconds or so, the immiscible liquids separate and the reaction stops.

Two people are in the plant at the time of the excursion. They receive doses of 2 rads and less than 1 rad.

A fire breaks out on the stern of the submarine tender USS Canopus at Holy Loch, Scotland. This vessel carries several nuclear weapons and is moored alongside two nuclear submarines: the USS Francis Scott Key (SSBN-657) and the USS James K. Polk (SSBN-645). The Francis Scott Key casts off, but the Polk remains alongside.

U.S. naval authorities in Holy Loch and London reassure the public: "We have drills and precautions which rule out any danger whatsoever." It takes four hours to bring the fire under control; its cause is never determined. Three men are killed. U.S. Navy documents record extensive damage in the area of the fire.

A series of reflector-evaluation experiments at the Kurchatov Institute uses fuel rods enriched to about 20% U-235 (a value typical of icebreaker reactors.) Conducted at the critical experiment facility, SF-7, these experiments involve comparing iron and beryllium as reflectors. Fuel-rod configurations are variable, with a fixed lattice of boron carbide safety rods. Criticality is achieved by flooding the core with light water and regulating the neutron flux with the safety rods.

On the day of the accident, a new core configuration has been assembled and left overnight in the dry tank. The beryllium reflector is left in place because it was used in the previous phase of testing. However, calculations for this configuration have been done only for an iron reflector. Without waiting for the supervising physicist or the control console operator, the supervisor switches on the pump to begin filling the tank with water. Some instrumentation is powered on, but not all. In particular, the safety rods are not inserted.

As the tank fills, the supervisor begins talking with a scientist from Gorky who just arrived. Standing by the tank, they see a blue glow reflected from the ceiling and hear an audible neutron alarm. They think the trouble is elsewhere and race from the room. Other workers also leave. Later, a manager is informed and tries to enter the room. But radiation levels and steam from the tank make it impossible to approach the control console. After 5 to 7 minutes, power to the pump is shut off at a substation.

Later assessment shows about 50 pulses of neutrons have occurred, each with a yield of 5x10¹⁷ fissions. Total yield is estimated as 2x10¹⁹. The scientist and the supervisor each receive roughly 1,500 rem on their feet. Other personnel are behind heavy shielding and receive much smaller doses. Because the rate of criticality insertion is low, no fuel rods are damaged and the room is not contaminated.

After the final experiment concludes, the supervisor orders all control and safety rods inserted. The neutron source is removed from the core. Four staff members (including the supervisor) enter the room to examine the experiment. The supervisor then orders a fast dump of the water. The slow drain has been used in all previous experiments. Water pressure causes the plexiglas baseplate to deform; the fuel rods, unsupported, fall into a highly supercritical arrangement. The energy release, estimated as 5x10¹⁸ fissions, destroys some of the fuel rods and splashes water out of the tank.

Despite this, radioactive contamination of the room is minimal, and none escapes to the outer premises. However, all four personnel are severely exposed. A technician beside the tank receives 6,000 rem and dies in 5 days. The supervisor gets 2,000 rem and dies within 15 days. Doctors are able to save the other two, who receive doses of 700-800 rem, but both suffer long-term health impairment.

Karen Silkwood is a metallography laboratory technician at the Cimarron River plutonium plant of Kerr-McGee Nuclear Corporation in Crescent, OK. She joins the Oil, Chemical & Atomic Workers Union local at the plant and participates in a strike. That strike reduces the number of union members from 150 to 20, and Kerr-McGee schedules a decertification election. Silkwood is elected to the union bargaining committee with the assignment to investigate health and safety issues. In the summer of 1974, she testifies to the AEC that the company is careless with the plutonium it is building into reactor fuel rods. Safety standards allegedly have slipped because of a production speedup, which results in employees being given tasks for which they are poorly trained. Silkwood also alleges that Kerr-McGee welds the fuel rods improperly and falsifies inspection records.

In October or November of 1974, Silkwood is discovered to be significantly contaminated with plutonium. Strangely, though the gloves in the glovebox she uses to make the plutonium pellets are in good shape, there is contamination on their outside surfaces. Silkwood is decontaminated at the plant, but the next day is found to show alpha activity again, although she does not work at the glovebox that morning. Her locker and automobile show no activity. Her apartment, however, shows higher levels of alpha emission than the areas where she works. The worst is 400,000 dpm (disintegrations per minute) on a package of bologna and cheese in the refrigerator. Kerr-McGee arranges for her to be examined at Los Alamos, where a doctor assures her that the amount of plutonium in her body is not dangerous. The situation causes her some stress nevertheless. Under prescription, she begins using Methaqualone to calm her nerves.

Silkwood says she has documents to prove her allegations. Shortly after six o'clock on 13 November she leaves a union meeting at the Hub Cafe in Crescent. Another attendee of that meeting later testifies that she does have a binder and a packet of documents at the cafe. She gets into her car and heads alone for Oklahoma City, about 30 miles away, to meet with New York Times reporter David Burnham and Steve Wodka, an official of her union's national. She never gets to the meeting. Later that evening, her body is found in her car, which has run off the road and struck a culvert. The car contains no documents. There is no firm evidence of foul play, and the coroner finds 0.35 milligrams of methaqualone (Quaalude) per 100 milliliters of blood at the time of her death. That amount is almost twice the recommended dosage for inducing drowsiness.

Kerr-McGee closes its nuclear fuel plants in 1975. The grounds of the Cimarron plant are still being decontaminated 25 years later. In 1979, Silkwood's estate is awarded $10.5 million for personal injury and punitive damages, but this judgement is reversed on appeal. In 1986, the Supreme Court restores the original verdict. The suit is headed for retrial when Kerr-McGee settles out of court for $1.38 million, admitting no liability. Many aspects of the case are controversial. There are those who think Karen Silkwood was murdered on Kerr-McGee's orders. Others believe she stole some plutonium and deliberately contaminated herself, seeking to discredit the company. The BBC (which has the best summary) says "That controversy continues to this day. It seems likely that the facts will never be publicly known."

At the Radiation Technology, Inc. facility in Rockaway, New Jersey, Michael Pierson is exposed to 150-300 rems when a safety interlock system designed to protect workers from a cobalt-60 source fails.

In 1986, the NRC cites company executives for intentionally disabling the system. In 1988, after more than 30 NRC violations, company president Martin Welt and nuclear engineer William Jouris are charged in federal court with 11 counts of conspiracy to defraud the NRC, making false statements and violating the Atomic Energy Act. Welt, who threatened to fire workers who didn't lie to NRC investigators, is also charged with obstruction of justice. Both men are convicted. Joris is sentenced to probation; Welt is sentenced to two years in prison, placed on three years probation, and fined $50,000.

While workers are draining a piping system aboard the USS Puffer (SSN-562), radioactive water spills on the drydock surface at the Puget Sound Naval Shipyard in Bremerton, WA. A Navy spokesman says that "less than 5 gallons" of slightly radioactive water from the ship's secondary cooling system were lost, and that it spilled as the workers were draining the water into two 5-gallon containers, a routine procedure. According to the Navy, no workers were contaminated and the drydock drain was closed before any spillage escaped into the sea.

Shipyard employees reportedly dispute the Navy's account, saying that the spill was much bigger, about 100 gallons, that response to the spill was slow, and that several workers suffered skin contamination. A 15- by 20-foot section of drydock is jackhammered up, sealed in drums and shipped to a nuclear waste site in Hanford, WA.

The accident has multiple causes. A leaky valve causes unnoticed dilution of a buffer solution, so that it takes up more uranium than expected. The tank density alarm that should indicate this is inoperative, and another tank has not had its density alarm installed. A chart recorder shows the departure from constant liquid level, but the leak is so slow that this would not be noticed unless specifically looked for. (In any case, the chart paper runs out weeks before the accident and is not replaced until afterward.) Finally, procedures requiring sample analysis are not being followed.

The effect of all these factors is to allow a gradual closed-loop concentration of uranium nitrate in two of the process columns. When radiation alarms begin sounding, the supervisor goes outside the plant and measures dose rates of 100 mRem/hour. He orders the building evacuated. This is accomplished in three minutes. No significant exposures result, and the estimated yield of 2.7x10¹⁸ fissions does not damage any equipment or contaminate the facility. The incident leads to an extensive review of procedures, better training and documentation, and installation of more instrumentation.

On this occasion, production pressure apparently causes two workers to violate procedures by assisting each other. The end result is that one attempts to place a fourth ingot into a container already holding three. This fourth ingot is either violently ejected by the prompt heat of the criticality, or withdrawn by the operator when he sees the flash. In any case, the reaction is ended after triggering radiation alarms to cause evacuation of two buildings.

Later analysis of the ingots involved leads to a yield estimate of 3x10¹⁵ fissions. The equipment is not damaged and no contamination results. However, the operator who held the fourth ingot gets a whole-body dose of 250 rad and more than 2,000 rad on his hands. His arms are amputated up to the elbows, and he later has eye trouble as well. Seven others receive doses of 5 to 60 rad, mostly from fast neutrons.

Metropolitan Edison, the operator of the plant, is indicted in 1983 for falsifying leak rate data at TMI-2 and for destroying documents before the accident. In 1984, it pleads guilty to one count and no contest to six counts of the 11-count indictment.

Investigation of the wreckage is done by remote control, and very cautiously. By 1985, robotic cameras show much greater damage to the core than expected. Temperatures reached 5,000 degrees; half the fuel elements melted and slumped down to the bottom of the containment, leaving a great void. The cleanup takes ten years and costs over a billion dollars. Based on this cost, and the amount of radiation released, TMI is the worst commercial nuclear reactor accident in the United States. It brings about wrenching changes in the way nuclear plants are built and operated, and it essentially stops any such plants being built in the U.S.

Still, health impacts of the radiation release remain controversial. The Rogovin Report is quoted as stating that "approximately 2.5 million curies of radioactive noble gases and 15 curies of radioiodines were released. These releases resulted in an average dose of 1.4 mrem to the approximately two million people in the site area." The majority of epidemiological studies performed since the accident show no correlation between this release and cancer or other adverse health impacts in the Susquehanna Valley. A study by Dr. Ernest J. Sternglass, professor of radiation physics at the University of Pittsburgh, claims that the accident leads to a minimum of 430 infant deaths. There is considerable justification for the industry's position that "no one died at Three Mile Island". In a lawsuit by 2,000 neighbors of the plant alleging radiation-induced injuries, a court finds no substantial proof of any damages. A 1994 survey by the Union of Concerned Scientists notes a paucity of investigation of this question, and predicts that solid answers may never be known.

Failure to close a valve at the Tsuruga processing plant allows over 4,000 gallons of highly radioactive water to leak from a storage tank onto the floor of the waste reprocessing building. The water escapes the building through a manhole cover and a crack in the floor to wind up in Urazoko Bay, where high levels of cobalt-60 and manganese-54 are later found in the bay's edible seaweed. The leak is not noticed for three hours. During that time, 56 plant workers are exposed, receiving an average dose of 10 mRem.

The accident is not disclosed to the public until 18 April. Shortly afterward, six officials of Japan Atomic Power Corporation, including the Tsuruga plant's director, are replaced because of their roles in the cover-up. It is also found that serious incidents have occurred previously at the plant.

Located in Buenos Aires, Argentina, the RA-2 Facility houses a low-power (the source says "essentially zero power") experimental reactor assembly. This can hold 19 fuel-element plates, but four of them are normally removed and two cadmium plates inserted for reaction-rate control. There is also a graphite reflector. The reactor vessel is filled with de-mineralized water for tests and is supposed to be drained during changes in fuel-plate configuration, or whenever people are in the room.

The reactor technician, a qualified operator with 14 years experience, is alone in the room making such a configuration change. The tank has not been drained. He inserts two new fuel-element plates while the cadmium plates are not installed. Criticality is apparently achieved during insertion of the second plate, since it is found partially inserted. The excursion yields approximately 4.5x10¹⁷ fissions. The operator's exposure, mostly on the upper right side of his body, is 2,000 rad from gamma rays and 1,700 from neutrons. He dies two days later. Two people in the control room receive doses of about 15 rad from neutrons and 20 from gamma rays. Six others receive smaller doses, down to 1 rad, and nine receive less than one rad.

El Señor Vicénte Soledo Alardín is a scrap dealer in Juarez, Mexico. Unfamiliar with the dangers of radioactive materials, he removes the source from a radiation therapy machine he has acquired. The source consists of 6,010 pellets of cobalt-60 encased in a tungsten shell. This shell is damaged during the dismantling process. When Sr. Alardín drives to the salvage yard Jonke Fénix to sell his prize, some of the pellets spill in the bed of his truck and onto the roads. Each of them reportedly contains 70 microcuries of isotope and can deliver a dose of 25 R/h at close range.

The junkyard operator is equally unfamiliar with radioisotopes. During processing, more pellets are scattered throughout the yard, contaminating 60 employees and most of the metal at the facility. Meanwhile, Sr. Alardín's truck is parked elsewhere for two months with a flat tire. It contaminates another 200 people who live and work nearby. Some of their exposures are the largest ever recorded in Mexico. The truck is later found to emit 50R/h at a distance of one meter.

Scrap from the junkyard is sold to a smelting facility, contaminating 5,000 tons of steel with an estimated 300 curies of activity. The steel is made into building materials and legs for kitchen tables. Some of it winds up in the U.S. and Canada. The situation is only discovered months later when a truck delivering building materials to Los Alamos National Laboratory takes a wrong turn and drives through a radiation monitor, setting off an alarm.

Using special airborne detection equipment loaned by the U.S. Department of Energy, the Mexican government locates hot spots along the roads used to transport the original source. In some cases the highways have to be torn up to recover pellets embedded in the road surface. Mexico also condemns 109 houses in the state of Sinaloa due to contaminated building materials. The incident prompts the U.S. Customs Service and the NRC to install radiation detection equipment at all major border crossings.

Note: If the rating and quantity for the pellets are correct, there's no way they can add up to 300 Curies. My guess is the rating for each pellet should be 7,000 µCuries. This allows for a loss of about one-quarter of the pellets on the way to Jonke Fénix.

At a fossil-fueled power plant under construction in Mohammedia, Morocco, iridium-192 sources are being used to radiograph welds. One of these sources, containing approximately 30 curies of iridium-192, apparently becomes disconnected from its drive cable and is not properly returned to its shielded container. Subsequently, a passing laborer notices the tiny metal cylinder on the ground and takes it home. During May and June of 1984, a total of eight persons, including the laborer and his entire family and some relatives, die with the clinical diagnosis of "lung hemorrhages." Other individuals also receive significant doses of radiation that require medical attention. Three severely exposed individuals are hospitalized at the Curie Institute in Paris and later released in apparently satisfactory condition.

It is initially assumed that the deaths are the result of poisoning. Only after the last family member has died is it suspected that the deaths might be due to radiation. The source is recovered in June 1984. Although the source container is marked by the internationally recognized radiation caution symbol, the source itself bears no markings.

There is no information available on the precautionary radiation surveys that may have been performed at the time of the incident. However, it is apparent from the stated facts that radiation surveys of the type described in the NRC regulations, if performed, would have disclosed the problem and may have prevented the incident.

The USS Kitty Hawk (CV-63) is struck during night operations by a surfacing Soviet Victor-I class nuclear-powered attack submarine in the southern Sea of Japan, approximately 100 miles west of mainline Japan, while en route to the Yellow Sea. The Kitty Hawk sustains a minor hole below the water line in an aircraft fuel tank on her starboard side and continues normal operations. The Soviet vessel is observed dead in the water with a dent across its aft deck. It is aided by the Soviet Kara class cruiser Petropavlovsk and later towed by a Soviet salvage vessel to the naval base at Vladivostok. U.S. Navy officers say there is no evidence of leakage from the submarine.

The Kitty Hawk and her carrier group are taking part in joint U.S.-Korean "Team Spirit 84" exercises. The submarine, along with Soviet surface ships, has been follwoing these exercises for several days. Navy officials report that, after simulating its destruction 15 times, carrier group ships break contact with the submarine to enter a new phase of maneuvers in which the Kitty Hawk attempts to evade the trailing Soviet surface ships. The submarine apparently loses track of the Kitty Hawk during this phase and surfaces in order to locate her, causing the collision.

A Soviet Victor-I class nuclear-powered attack submarine is badly damaged when it collides with a Soviet tanker in the Strait of Gibraltar. The collision rips off the twin-hulled submarine's bow section, exposing the sonar and torpedo-tube compartments. It proceeds to the Soviet anchorage at Hammament, Tunisia for emergency repairs, and returns to its home port on the Kola Peninsula in early October.

Reports are that the submarine was travelling in the "noise shadow" of the tanker to avoid detection while exiting the Mediterranean Sea. Jane's Defense Weekly notes that the alternating layers of cold and warm water in the narrow Strait make it likely for a submarine "to encounter sudden thermal gradients which make her porpoise upwards," and this is thought to be the cause of the accident.

The Fernald Uranium Plant, a 1,050-acre uranium fuel production complex 20 miles northwest of Cincinnati, Ohio is temporarily shut down after the Department of Energy discovers that excessive amounts of radioactive materials have been released through ventilation systems. Subsequent reports document the following discharges into the valley of the Greater Miami River over the previous thirty years:

• 39 tons of uranium dust released into the atmosphere;
• 83 tons of uranium dust released into surface water;
• 230 tons of radioactive substances released into pits and swamps;
• 5,300 tons of hazardous chemicals released into pits and swamps.

Significant quantities of the radioactives and other hazardous materials in those pits and swamps find their way into local groundwater.

In addition, 337 tons of uranium hexafluoride are found to be unaccounted for, their whereabouts completely unknown. Residents of the valley sue in 1988 and are granted a $73 million settlement by the government. Plant operations are not shut down permanently until 1989.