7. SL-1 Experimental Power Station, Idaho USA 1961 – Level 4
On 3rd January, 1961 a USA army experimental nuclear power reactor underwent a steam explosion and meltdown killing its three operators. The cause of this was because of improper removal of the control rod, responsible for absorbing neutrons in the reactor core. This event is the only known fatal reactor accident in the USA. The accident released about 80 curies of iodine -131.
5. Three Mile Island Accident, Pennsylvania USA 1979 – Level 5
28th March saw two nuclear reactors meltdown. It was subsequently the worst disaster in commercial nuclear power plant history. Small amounts of radioactive gases and radioactive iodine were released into the environment. Luckily, epidemiology studies have not linked a single cancer with the accident.
https://www.processindustryforum.com/hot-topics/nucleardisasters
- 26 July 1959 — INES Level 4[8] – Santa Susana Field Laboratory, California, United States – Partial meltdown
- A partial core meltdown took place when the Sodium Reactor Experiment (SRE) experienced a power excursion that caused severe overheating of the reactor core, resulting in the melting of one-third of the nuclear fuel and significant release of radioactive gases. The amount of radioactivity released is disputed, with it ranging from 28 Curies [13]to as much as 240 to 260 times worse than Three Mile Island. Over the succeeding years, the site was cleaned up and all buildings and contamination removed. The soil was removed and other soil[14] brought in and now forms a portion of an area near the Simi Valley Adventist Hospital.[15]
- 7 December 1975 — INES Level 3 – Greifswald, Germany (then East Germany) – Station blackout
- A fire in a cable duct after a short circuit disabled the electrical power supply for all feedwater and emergency core cooling pumps. A power supply was improvised by the operating personnel after several hours.
- 21 January 1969 — INES Level 4 – Lucens, Canton of Vaud, Switzerland – Explosion
- A loss of coolant led to meltdown of one fuel element and a steam explosion in the Lucens reactor, an experimental reactor in a large rock cavern at Lucens. The underground location of this reactor acted like a containment building and prevented any outside contamination. The cavern was contaminated and temporary sealed. No injuries or fatalities resulted.[21][22]
- Defueling and partial dismantling occurred from 1969 to 1973. In 1988, the lowest caverns were filled with concrete, and a regulatory permit was issued in December 1990. Currently, the archives of the Canton of Vaud are located in the caverns.[23]
- 26 April 1986 — INES Level 7 – Pripyat, Ukraine (then Ukrainian Soviet Socialist Republic, Union of Soviet Socialist Republics) – Power excursion, explosion, complete meltdown
- An inadequate reactor safety system test[32] led to an uncontrolled power excursion, causing a severe steam explosion, meltdown, and release of radioactive materials at the Chernobyl nuclear power plant located approximately 100 kilometers (60 miles) north-northwest of Kiev. Approximately 50 fatalities (mostly cleanup personnel) resulted from the accident and the immediate aftermath. An additional nine fatal cases of thyroid cancer in children in the Chernobyl area have been attributed to the accident. The explosion and combustion of the graphite reactor core spread radioactive material over much of Europe. 100,000 people were evacuated from the areas immediately surrounding Chernobyl; in addition, 300,000 were touched from heavy fallout in Belarus, Ukraine and Russia. An "Exclusion Zone" was created surrounding the site encompassing approximately 3,000 km2 (1,200 sq mi) and deemed off-limits for human habitation for an indefinite period. Several studies by governments, U.N. agencies and environmental groups have estimated the consequences and eventual number of casualties. Their findings are subject to controversy.
- 4 May 1986 — no INES Level – Hamm-Uentrop, Germany (then West Germany) – Fuel damaged
- Spherical fuel pebbles became lodged in the pipe used to deliver fuel elements to the reactor at an experimental 300-megawatt THTR-300 HTGR. Attempts by an operator to dislodge the fuel pebble damaged the pipe, releasing activated coolant gas which was detectable up to two kilometers from the reactor.[33]
- A pressure buildup led to an explosive mechanical failure in a 34 m3 (1,200 cu ft) stainless steel reaction vessel buried in a concrete bunker under building 201 of the radiochemical works at the Tomsk-7 Siberian Chemical Enterprise plutonium reprocessing facility. The vessel contained a mixture of concentrated nitric acid, 8,757 kg (19,306 lb) uranium, 449 g (15.8 oz) plutonium along with a mixture of radioactive and organic waste from a prior extraction cycle. The explosion dislodged the concrete lid of the bunker and blew a large hole in the roof of the building, releasing approximately 6 GBq (160 mCi) of Pu 239 and 30 TBq (810 Ci) of other radionuclides into the environment. The contamination plume extended 28 km (17 mi) NE of building 201, 20 km (12 mi) beyond the facility property. The small village of Georgievka (pop. 200) was at the end of the fallout plume, but no fatalities, illnesses or injuries were reported. The accident exposed 160 on-site workers and almost two thousand cleanup workers to total doses of up to 50 mSv (the threshold limit for radiation workers is 20 mSv/yr).[34][35][36]
2000s[edit]
- Partially spent fuel rods undergoing cleaning in a tank of heavy water ruptured and spilled fuel pellets at Paks Nuclear Power Plant. It is suspected that inadequate cooling of the rods during the cleaning process combined with a sudden influx of cold water thermally shocked fuel rods causing them to split. Boric acid was added to the tank to prevent the loose fuel pellets from achieving criticality. Ammonia and hydrazine were also added to absorb 131I.[43]
- 19 April 2005 — INES Level 3 – Sellafield, England, United Kingdom – Nuclear material leak
- 20 t (20 long tons; 22 short tons) of uranium and 160 kg (350 lb) of plutonium dissolved in 83 kl (2,900 cu ft) of nitric acid leaked over several months from a cracked pipe into a stainless steel sump chamber at the Thorp nuclear fuel reprocessing plant. The partially processed spent fuel was drained into holding tanks outside the plant.[44][45]
- https://en.wikipedia.org/wiki/List_of_civilian_nuclear_accidents
In listing military nuclear accidents, the following criteria have been adopted:
- There must be well-attested and substantial health damage, property damage or contamination.
- The damage must be related directly to radioactive material, not merely (for example) at a nuclear power plant.
- To qualify as "military", the nuclear operation/material must be principally for military purposes.
- To qualify as "accident", the damage should not be intentional, unlike in nuclear warfare.
This list may be incomplete due to military secrecy in the Soviet Union.
- https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
March 1, 1954 Bikini Atoll, Republic of the Marshall Islands (then Trust Territory of the Pacific Islands) Nuclear test accident During the Castle Bravo test of the first deployable hydrogen bomb, a miscalculation resulted in the explosion being over twice as large as predicted, with a total explosive force of 15 megatons of TNT (63 PJ). Of the total yield, 10 Mt (42 PJ) were from fission of the natural uranium tamper, but those fission reactions were quite dirty, producing a large amount of fallout. Combined with the much larger than expected yield and an unanticipated wind shift, radioactive fallout spread into unexpected areas. A Japanese fishing boat, the Daigo Fukuryu Maru/Lucky Dragon, came into contact with the fallout, which caused many of the crew to become ill, with one fatality. The fallout spread eastward onto the inhabited Rongelap and Rongerik Atolls. These islands were not evacuated before the explosion due to the unanticipated fallout zone and the financial cost involved, but many of the Marshall Islands natives have since suffered from radiation burns and radioactive dusting and also similar fates as the Japanese fishermen and have received little, if any, compensation from the federal government.[11] The test resulted in an international uproar and reignited Japanese concerns about radiation, especially with regard to the possible contamination of fish. Personal accounts of the Rongelap people can be seen in the documentary Children of Armageddon.- https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
- How United States was Planed
May 22, 1957 Kirtland AFBin New Mexico, US Non-nuclear detonation of a Mark 17thermonuclear bomb[18] A B-36 ferrying a nuclear weapon from Biggs AFB to Kirtland AFB dropped a nuclear weapon on approach to Kirtland. The weapon struck the ground 4.5 miles south of the Kirtland control tower and 0.3 miles west of the Sandia Base reservation. The weapon was completely destroyed by the detonation of its high explosive material, creating a crater 12 feet (3.7 m) deep and 25 feet (7.62 m) in diameter. Radioactive contamination at the crater lip amounted to 0.5 milliroentgen.[16] - https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
October 8–12, 1957 Sellafield, Cumbria, UK Reactor core fire See Windscale fire. Technicians mistakenly overheated Windscale Pile No. 1 during an annealing process to release Wigner energy from graphite portions of the reactor. Poorly placed temperature sensors indicated the reactor was cooling rather than heating. The excess heat led to the failure of a nuclear cartridge, which in turn allowed uranium and irradiated graphite to react with air. The resulting fire burned for days, damaging a significant portion of the reactor core. About 150 burning fuel cells could not be removed from the core, but operators succeeded in creating a firebreak by removing nearby fuel cells. An effort to cool the graphite core with water and the switching off of the air cooling system eventually quenched the fire. The reactor had released radioactive gases into the surrounding countryside, primarily in the form of iodine-131 (131I). Milk distribution was banned in a 200-square-mile (520 km2) area around the reactor for several weeks. A 1987 report by the National Radiological Protection Board predicted the accident would cause as many as 100 long-term cancer deaths, although the Medical Research Council Committee concluded that "it is in the highest degree unlikely that any harm has been done to the health of anybody, whether a worker in the Windscale plant or a member of the general public." The reactor that burned was one of two air-cooled, graphite-moderated natural uranium reactors at the site used for production of plutonium.[24][25][26] A 2007 study concluded that because the actual amount of radiation released in the fire could be double the previous estimates, and that the radioactive plume actually travelled further east, there were 100 to 240 cancer fatalities in the long term as a result of the fire.[27][28][29] - https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
- A criticality accident occurred on December 30, 1958, at the Los Alamos National Laboratory in Los Alamos, New Mexico, in the United States. It is one of 60 known criticality events that have occurred outside the controlled conditions of a nuclear reactor or test, though it was the third such event that took place in 1958 after events on 16 June[1] at the Y-12 Plant in Oak Ridge, Tennessee, and on 15 October at the Vinča Nuclear Institute in Vinča, Yugoslavia. The accident involved plutonium compounds dissolved in liquid chemical reagents; within 35 hours, it killed chemical operator Cecil Kelley by severe radiation poisoning.
- https://en.wikipedia.org/wiki/Cecil_Kelley_criticality_accident
- A breeder reactor is a nuclear reactor that generates more fissile material than it consumes.[1] Breeder reactors achieve this because their neutron economy is high enough to create more fissile fuel than they use, by irradiation of a fertile material, such as uranium-238 or thorium-232, that is loaded into the reactor along with fissile fuel. Breeders were at first found attractive because they made more complete use of uranium fuel than light water reactors, but interest declined after the 1960s as more uranium reserves were found,[2] and new methods of uranium enrichment reduced fuel costs.
- https://en.wikipedia.org/wiki/Breeder_reactor
A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation atomic bombs, a more compact size, a lower mass or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 (235
U
) or plutonium-239 (239
Pu
).Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by 235
U
or 239
Pu
) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs.[note 1]A fusion explosion begins with the detonation of the fission primary stage. Its temperature soars past approximately 100 million Kelvin, causing it to glow intensely with thermal X-radiation. These X-rays flood the void (the "radiation channel" often filled with polystyrene foam) between the primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating the two assemblies ensures that debris fragments from the fission primary (which move much slower than X-ray photons) cannot disassemble the secondary before the fusion explosion runs to completion.
The secondary fusion stage—consisting of outer pusher/tamper, fusion fuel filler and central plutonium spark plug—is imploded by the X-ray energy impinging on its pusher/tamper. This compresses the entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction. The fission products of this chain reaction heat the highly compressed, and thus super dense, thermonuclear fuel surrounding the spark plug to around 300 million Kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride, the fissioning plutonium spark plug also emits free neutrons which collide with lithium nuclei and supply the tritium component of the thermonuclear fuel.
https://en.wikipedia.org/wiki/Thermonuclear_weapon
This is a list of major hydroelectric power station failures due to damage to a hydroelectric power station or its connections. Every generating station trips from time to time due to minor defects and can usually be restarted when the defect has been remedied. Various protections are built into the stations to cause shutdown before major damage is caused. Some hydroelectric power station failures may go beyond the immediate loss of generation capacity, including destruction of the turbine itself, reservoir breach and significant destruction of national grid infrastructure downstream. These can take years to remedy in some cases.
Where a generating station is large compared to the connected grid capacity, any failure can cause extensive disruption within the network. A serious failure in a proportionally large hydroelectric generating station or its associated transmission line will remove a large block of power from the grid that may lead to widespread disturbances.
https://en.wikipedia.org/wiki/List_of_hydroelectric_power_station_failures
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of Operation Castle. Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon.[1][2] Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving lithium-7,[3] which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll. At the time, it was the most powerful artificial explosion in history.
Fallout, the heaviest of which was in the form of pulverized surface coral from the detonation, fell on residents of Rongelap and Utirik atolls, while the more particulate and gaseous fallout spread around the world. The inhabitants of the islands were not evacuated until three days later and suffered radiation sickness. Twenty-three crew members of the Japanese fishing vessel Daigo Fukuryū Maru ("Lucky Dragon No. 5") were also contaminated by the heavy fallout, experiencing acute radiation syndrome. The blast incited international reaction over atmospheric thermonuclear testing.[4]
The Bravo Crater is located at 11°41′50″N 165°16′19″E. The remains of the Castle Bravo causeway are at 11°42′6″N 165°17′7″E.
https://en.wikipedia.org/wiki/Castle_Bravo
Thermal shock is a type of rapidly transient mechanical load. By definition, it is a mechanical load caused by a rapid change of temperature of a certain point. It can be also extended to the case of a thermal gradient, which makes different parts of an object expand by different amounts. This differential expansion can be more directly understood in terms of strain, than in terms of stress, as it is shown in the following. At some point, this stress can exceed the tensile strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.
Failure due to thermal shock can be prevented by:[1]
- Reducing the thermal gradient seen by the object, by changing its temperature more slowly or increasing the material's thermal conductivity
- Reducing the material's coefficient of thermal expansion
- Increasing its strength
- Introducing built-in compressive stress, as for example in tempered glass
- Decreasing its Young's modulus
- Increasing its toughness, by crack tip blunting (i.e., plasticity or phase transformation) or crack deflection
https://en.wikipedia.org/wiki/Thermal_shock
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