Chernobyl after the disaster
Encyclopedia
The Chernobyl disaster
, Chornobylʹsʹka katastrofa, was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic (then part of the Soviet Union
), now in Ukraine
.
Following the accident, questions arose about the future of the plant and its eventual fate. All work on the unfinished reactors 5 and 6 was halted three years later. However, the trouble at the Chernobyl plant did not end with the disaster in reactor
4. The damaged reactor was sealed off and 200 cubic metres (261.6 cu yd) of concrete
was placed between the disaster site and the operational buildings. The Ukrainian government continued to let the three remaining reactors operate because of an energy
shortage in the country. In 1991, a fire broke out in the turbine building of reactor 2; the authorities subsequently declared the reactor damaged beyond repair and had it taken offline. Reactor 1 was decommissioned in November 1996 as part of a deal between the Ukrainian government and international organizations such as the IAEA to end operations at the plant. On 15 December 2000, then-President Leonid Kuchma
personally turned off Reactor 3 in an official ceremony, shutting down the entire site.
, which was built quickly to allow continuing operation of the other reactors at the plant.
A New Safe Confinement
was to have been built by the end of 2005; however, it has suffered ongoing delays and , when construction finally began, is expected to be completed in 2013. The structure is being built adjacent to the existing shelter and will be slid into place on rails. It is to be a metal arch 105 metres (344.5 ft) high and spanning 257 metres (843.2 ft), to cover both unit 4 and the hastily built 1986 structure. The Chernobyl Shelter Fund
, set up in 1997, has received €
810 million from international donors and projects to cover this project and previous work. It and the Nuclear Safety Account, also applied to Chernobyl decommissioning, are managed by the European Bank for Reconstruction and Development
(EBRD).
A handful of Ukrainian scientists work inside the sarcophagus, but outsiders are rarely granted access. In 2006 an Australian 60 Minutes team led by reporter Richard Carleton and producer Stephen Rice were allowed to enter the sarcophagus for 15 minutes and film inside the control room.
, as well as some material in a small spent fuel interim storage facility pond (ISF-1).
In 1999 a contract was signed for construction of a radioactive waste
management facility to store 25,000 used fuel assemblies from units 1–3 and other operational wastes, as well as material from decommissioning units 1–3 (which will be the first RBMK units decommissioned anywhere). The contract included a processing facility able to cut the RBMK fuel assemblies and to put the material in canisters, which were to be filled with inert gas
and welded shut. The canisters were to be transported to dry storage vaults
, where the fuel containers would be enclosed for up to 100 years. This facility, treating 2500 fuel assemblies per year, would be the first of its kind for RBMK fuel. However, after a significant part of the storage structures had been built, technical deficiencies in the concept emerged, and the contract was terminated in 2007. The interim spent fuel storage facility (ISF-2) will now be completed by others by mid-2013.
Another contract has been let for a liquid radioactive waste treatment plant, to handle some 35,000 cubic meters of low- and intermediate-level liquid wastes at the site. This will need to be solidified and eventually buried along with solid wastes on site.
In January 2008, the Ukrainian government announced a 4-stage decommissioning plan that incorporates the above waste activities and progresses towards a cleared site
.
s (670 PBq
). The radioactive material consists of core
fragments, dust
, and lava
-like "fuel containing materials" (FCM, also called "corium") that flowed through the wrecked reactor building before hardening into a ceramic
form.
Three different lavas are present in the basement of the reactor building: black, brown, and a porous ceramic. They are silicate glasses with inclusion
s of other materials within them. The porous lava is brown lava that dropped into water and thus cooled rapidly.
from the wrecked reactor is only 10 kg (22 lb) per year. This low rate of uranium leaching
suggests that the lava is resisting its environment. The paper also states that when the shelter is improved, the leaching rate of the lava will decrease.
Some of the surfaces of the lava flows have started to show new uranium mineral
s such as and uranyl carbonate. However, the level of radioactivity is such that during one hundred years the self irradiation of the lava α decays per gram and 2 to of β or γ) will fall short of the level of self irradiation required to greatly change the properties of glass
(1018 α decays per gram and 108 to 109 Gy of β or γ). Also the rate of dissolution of the lava in water is very low (10−7 g-cm−2 day−1), suggesting that the lava is unlikely to dissolve in water.
and flax
plants grown inside (five kilometers from the power plant) the exclusion zone
found them to be relatively unaffected by radiation. Martin Hajduch from the Institute of Plant Genetics and Biotechnology at the Slovak Academy of Sciences
said: "We detected very low radioactivity in the seeds. In the stem or leaves there is radioactivity, but it is somehow blocked and doesn't come to the seeds."
Hajduch and his colleagues in Ukraine
conducted a proteomics
study of the plants and found that the seeds harvested inside the exclusion zone
compared favorably with ones grown in non-contaminated soil outside.http://www.cnn.com/2011/WORLD/europe/01/14/chernobyl.nature.radiation.debate/index.html
."
The present shelter is constructed over the ruins of the reactor building. The two "Mammoth Beams" that support the roof of the shelter rest partly on the structurally unsound west wall of the reactor building that was damaged by the accident. The western end of the shelter roof is supported by a wall at a point designated axis 50. This wall is reinforced concrete
, and was cracked by the accident. In December 2006 the "Designed Stabilisation Steel Structure" (DSSS) was extended until 50% of the roof load (about 400 tons) was transferred from the axis 50 wall to the DSSS. The DSSS is a yellow steel object that has been placed next to the wrecked reactor; it is 63 metres (207 ft) tall and has a series of cantilever
s that extend through the western buttress
wall, and is intended to stabilize the sarcophagus. This was done because if the wall of the reactor building or the roof of the shelter were to collapse, then large amounts of radioactive dust and particles would be released directly into the atmosphere
, resulting in a large new release of radioactivity into the environment.
A further threat to the shelter is the concrete slab that formed the "Upper Biological Shield" (UBS), situated above the reactor prior to the accident. This concrete slab was thrown upwards by the explosion
in the reactor core and now rests at approximately 15° from vertical. The position of the upper bioshield is considered inherently unsafe, as only debris supports it in its nearly upright position. A collapse of the bioshield would further exacerbate the dust conditions in the shelter, possibly spreading some quantity of radioactive materials out of the shelter, and could damage the shelter itself. The UBS is a circle 15 meters in diameter, weighing 1000 tons and consisting of 2000 cubes, each located above a fuel channel. The shield, called Pyatachok ("five kopek
coin") before the disaster, was afterwards named Component "E" and nicknamed "Elena"; the twisted fuel bundles still attached to it are called "Elena's hair."
. As humans were evacuated from the area 25 years ago, existing animal populations multiplied and rare species not seen for centuries have returned or have been reintroduced, for example lynx
, wild boar, wolf, Eurasian brown bear
, European bison, Przewalski's horse, and eagle owl. Birds even nest inside the cracked concrete sarcophagus shielding in the shattered remains of Reactor 4. The Exclusion Zone is so lush with wildlife and greenery that in 2007 the Ukrainian government designated it a wildlife sanctuary, and at 488.7 km2 it is one of the largest wildlife sanctuaries in Europe.
According to a 2005 U.N. report, wildlife has returned despite radiation levels that are presently 10 to 100 times higher than normal background radiation
. Although they were significantly higher soon after the accident, the levels have fallen because of radioactive decay
.
Biologist Anders Møller from the University of Paris
Sud in France has been examining the effects of radiation on animals around Chernobyl
for two decades.
"Areas with higher radiation have fewer animals, survival and reproduction is reduced, sperm are abnormal and have reduced swimming ability. Abnormalities are commonplace and mutations rates are much elevated," Møller said.
Last year, Møller and Tim Mousseau published the results of the largest census of animal life in the Chernobyl Exclusion Zone http://cricket.biol.sc.edu/chernobyl/Chernobyl_Research_Initiative/Introduction.html. It revealed, contrary to the Chernobyl Forum's 2005 reporthttp://www-ns.iaea.org/downloads/rw/meetings/chern-forum-3rd-meetings-statement-rev.pdf, that biodiversity in insects, birds and mammals is declining.
Not all species are affected by radiation in the same way according to Møller. Some birds -- including migrant species and long distance dispersers -- are more vulnerable to radiation than others, he said.
Martin Hajduch said animal numbers in the exclusion zone are probably higher now than before the accident. But that's because there are no humans there hunting or fishing.
"But if you look at how many species of animals are in the area, I think it would be less," Hajduch said.http://www.cnn.com/2011/WORLD/europe/01/14/chernobyl.nature.radiation.debate/index.html
Some researchers say that by halting the destruction of habitat
, the Chernobyl disaster helped wildlife flourish. Biologist Robert J. Baker of Texas Tech University
was one of the first to report that Chernobyl had become a wildlife haven and that many rodent
s he has studied at Chernobyl since the early 1990s have shown remarkable tolerance for elevated radiation levels.
Møller et al. (2005) suggested that reproductive success and annual survival rates of barn swallows
are much lower in the Chernobyl exclusion zone; 28% of barn swallows inhabiting Chernobyl return each year, while at a control area at Kanev 250 km to the southeast, the return rate is around 40%. A later study by Møller et al. (2007) furthermore claimed an elevated frequency of 11 categories of subtle physical abnormalities in barn swallows, such as bent tail feather
s, deformed air sacs, deformed beak
s, and isolated albinistic feather
s.
Smith et al. (2007) have disputed Møller's findings and instead proposed that a lack of human influence in the exclusion zone locally reduced the swallows' insect
prey and that radiation levels across the vast majority of the exclusion zone are now too low to have an observable negative effect. But the criticisms raised were responded to in Møller et al. (2008). It is possible that barn swallows are particularly vulnerable to elevated levels of ionizing radiation
because they are migratory
; they arrive in the exclusion area exhausted and with depleted reserves of radio-protective antioxidant
s after an arduous journey.
Several research groups have suggested that plant
s in the area have adapted to cope with the high radiation levels, for example by increasing the activity of DNA cellular repair
machinery and by hypermethylation
. (see Radiation Hormesis
). Given the uncertainties, further research is needed to assess the long-term health effects of elevated ionizing radiation from Chernobyl on flora and fauna.
s can make radioactivity mobile again. In particular V.I. Yoschenko et al. reported on the possibility of increased mobility of caesium
, strontium
, and plutonium
due to grass
and forest fires. As an experiment, fires were set and the levels of the radioactivity in the air downwind of these fires was measured.
Grass and forest fires have happened inside the contaminated zone, releasing radioactive fallout into the atmosphere. In 1986 a series of fires destroyed 23.36 km2 (5,772 acres) of forest, and several other fires have since burned within the 30 km (19 mi) zone. A serious fire in early May 1992 affected 5 km2 (1,240 acres) of land including 2.7 km2 (670 acres) of forest. This resulted in a great increase in the levels of caesium-137
in airborne dust.
In 2010, a series of wildfires
affected contaminated areas, specifically the surroundings of Bryansk
and border regions with Belarus
and Ukraine
. The Russian government claims that there has been no discernible increase in radiation levels, while Greenpeace
accuses the government of denial.
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...
, Chornobylʹsʹka katastrofa, was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic (then part of the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
), now in Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
.
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
4. The damaged reactor was sealed off and 200 cubic metres (261.6 cu yd) of concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
was placed between the disaster site and the operational buildings. The Ukrainian government continued to let the three remaining reactors operate because of an energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
shortage in the country. In 1991, a fire broke out in the turbine building of reactor 2; the authorities subsequently declared the reactor damaged beyond repair and had it taken offline. Reactor 1 was decommissioned in November 1996 as part of a deal between the Ukrainian government and international organizations such as the IAEA to end operations at the plant. On 15 December 2000, then-President Leonid Kuchma
Leonid Kuchma
Leonid Danylovych Kuchma was the second President of independent Ukraine from 19 July 1994, to 23 January 2005. Kuchma took office after winning the 1994 presidential election against his rival, incumbent Leonid Kravchuk...
personally turned off Reactor 3 in an official ceremony, shutting down the entire site.
Containment of the reactor
The Chernobyl reactor is now enclosed in a large concrete sarcophagusChernobyl Nuclear Power Plant sarcophagus
The Chernobyl Nuclear Power Plant sarcophagus or stone coffin is a massive concrete envelope surrounding the nuclear reactor unit 4 of the Chernobyl Nuclear Power Plant. It is designed to halt the release of radiation into the atmosphere following the Chernobyl disaster on April 26, 1986 and encase...
, which was built quickly to allow continuing operation of the other reactors at the plant.
A New Safe Confinement
New Safe Confinement
The New Safe Confinement is the structure intended to contain the nuclear reactor at Chernobyl, Ukraine, part of which was destroyed by the Chernobyl disaster in 1986. The idea is to prevent the reactor wreck from leaking radioactive material into the environment...
was to have been built by the end of 2005; however, it has suffered ongoing delays and , when construction finally began, is expected to be completed in 2013. The structure is being built adjacent to the existing shelter and will be slid into place on rails. It is to be a metal arch 105 metres (344.5 ft) high and spanning 257 metres (843.2 ft), to cover both unit 4 and the hastily built 1986 structure. The Chernobyl Shelter Fund
Chernobyl Shelter Fund
The Chernobyl Shelter Fund was set up in December 1997 with the purpose of funding the Shelter Implementation Plan . The main objective of the SIP, developed in a co-operative effort between the European Union, the United States and Ukraine, is to protect the personnel, population and environment...
, set up in 1997, has received €
Euro
The euro is the official currency of the eurozone: 17 of the 27 member states of the European Union. It is also the currency used by the Institutions of the European Union. The eurozone consists of Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg,...
810 million from international donors and projects to cover this project and previous work. It and the Nuclear Safety Account, also applied to Chernobyl decommissioning, are managed by the European Bank for Reconstruction and Development
European Bank for Reconstruction and Development
Founded in 1991, the European Bank for Reconstruction and Development uses the tools of investment to help build market economies and democracies in 30 countries from central Europe to central Asia. Its mission was to support the formerly communist countries in the process of establishing their...
(EBRD).
A handful of Ukrainian scientists work inside the sarcophagus, but outsiders are rarely granted access. In 2006 an Australian 60 Minutes team led by reporter Richard Carleton and producer Stephen Rice were allowed to enter the sarcophagus for 15 minutes and film inside the control room.
Radioactive materials and waste management
, some fuel remained in the reactors at units 1 through 3, most of it in each unit's cooling pondCooling pond
A cooling pond is a man-made body of water primarily formed for the purpose of supplying cooling water to a nearby power plant or industrial facility such as a petroleum refinery, pulp and paper mill, chemical plant, steel mill or smelter...
, as well as some material in a small spent fuel interim storage facility pond (ISF-1).
In 1999 a contract was signed for construction of a radioactive waste
Radioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
management facility to store 25,000 used fuel assemblies from units 1–3 and other operational wastes, as well as material from decommissioning units 1–3 (which will be the first RBMK units decommissioned anywhere). The contract included a processing facility able to cut the RBMK fuel assemblies and to put the material in canisters, which were to be filled with inert gas
Inert gas
An inert gas is a non-reactive gas used during chemical synthesis, chemical analysis, or preservation of reactive materials. Inert gases are selected for specific settings for which they are functionally inert since the cost of the gas and the cost of purifying the gas are usually a consideration...
and welded shut. The canisters were to be transported to dry storage vaults
Dry cask storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in the spent fuel pool for at least one year.. These casks are typically steel cylinders that are either welded or bolted closed. When inside, the fuel rods are surrounded...
, where the fuel containers would be enclosed for up to 100 years. This facility, treating 2500 fuel assemblies per year, would be the first of its kind for RBMK fuel. However, after a significant part of the storage structures had been built, technical deficiencies in the concept emerged, and the contract was terminated in 2007. The interim spent fuel storage facility (ISF-2) will now be completed by others by mid-2013.
Another contract has been let for a liquid radioactive waste treatment plant, to handle some 35,000 cubic meters of low- and intermediate-level liquid wastes at the site. This will need to be solidified and eventually buried along with solid wastes on site.
In January 2008, the Ukrainian government announced a 4-stage decommissioning plan that incorporates the above waste activities and progresses towards a cleared site
.
Lava-like fuel-containing materials (FCMs)
According to official estimates, about 95% of the fuel in the reactor at the time of the accident (about 180 metric tons) remains inside the shelter, with a total radioactivity of nearly 18 million curieCurie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
s (670 PBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
). The radioactive material consists of core
Nuclear reactor core
A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place.- Description :...
fragments, dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
, and lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
-like "fuel containing materials" (FCM, also called "corium") that flowed through the wrecked reactor building before hardening into a ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
form.
Three different lavas are present in the basement of the reactor building: black, brown, and a porous ceramic. They are silicate glasses with inclusion
Inclusion (mineral)
In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior....
s of other materials within them. The porous lava is brown lava that dropped into water and thus cooled rapidly.
Degradation of the lava
It is unclear how long the ceramic form will retard the release of radioactivity. From 1997 to 2002 a series of papers were published that suggested that the self-irradiation of the lava would convert all 1,200 metric tons into a submicrometer and mobile powder within a few weeks. But it has been reported that the degradation of the lava is likely to be a slow and gradual process rather than sudden and rapid. The same paper states that the loss of uraniumUranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
from the wrecked reactor is only 10 kg (22 lb) per year. This low rate of uranium leaching
Leaching
In general, leaching is the extraction of certain materials from a carrier into a liquid . Specifically, it may refer to:...
suggests that the lava is resisting its environment. The paper also states that when the shelter is improved, the leaching rate of the lava will decrease.
Some of the surfaces of the lava flows have started to show new uranium mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s such as and uranyl carbonate. However, the level of radioactivity is such that during one hundred years the self irradiation of the lava α decays per gram and 2 to of β or γ) will fall short of the level of self irradiation required to greatly change the properties of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
(1018 α decays per gram and 108 to 109 Gy of β or γ). Also the rate of dissolution of the lava in water is very low (10−7 g-cm−2 day−1), suggesting that the lava is unlikely to dissolve in water.
Biological phenomena
Scientists studying the seeds harvested from soybeanSoybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
and flax
Flax
Flax is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent...
plants grown inside (five kilometers from the power plant) the exclusion zone
Exclusion zone
An exclusion zone is an area that protesters are legally prohibited from protesting in.Exclusion zones often exist around seats of government and abortion clinics. As a result of protests by the Westboro Baptist Church at the funerals of soldiers killed in the Iraq War, 29 states and the US...
found them to be relatively unaffected by radiation. Martin Hajduch from the Institute of Plant Genetics and Biotechnology at the Slovak Academy of Sciences
Slovak Academy of Sciences
The Slovak Academy of Sciences SAV is the main scientific and research institution in Slovakia fostering basic and strategic basic research...
said: "We detected very low radioactivity in the seeds. In the stem or leaves there is radioactivity, but it is somehow blocked and doesn't come to the seeds."
Hajduch and his colleagues in Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
conducted a proteomics
Proteomics
Proteomics is the large-scale study of proteins, particularly their structures and functions. Proteins are vital parts of living organisms, as they are the main components of the physiological metabolic pathways of cells. The term "proteomics" was first coined in 1997 to make an analogy with...
study of the plants and found that the seeds harvested inside the exclusion zone
Exclusion zone
An exclusion zone is an area that protesters are legally prohibited from protesting in.Exclusion zones often exist around seats of government and abortion clinics. As a result of protests by the Westboro Baptist Church at the funerals of soldiers killed in the Iraq War, 29 states and the US...
compared favorably with ones grown in non-contaminated soil outside.http://www.cnn.com/2011/WORLD/europe/01/14/chernobyl.nature.radiation.debate/index.html
Possible further collapse of the sarcophagus
The protective box that was placed over the wrecked reactor was named object "Shelter" by the Soviet government, but the media and the public know it as the "sarcophagusChernobyl Nuclear Power Plant sarcophagus
The Chernobyl Nuclear Power Plant sarcophagus or stone coffin is a massive concrete envelope surrounding the nuclear reactor unit 4 of the Chernobyl Nuclear Power Plant. It is designed to halt the release of radiation into the atmosphere following the Chernobyl disaster on April 26, 1986 and encase...
."
The present shelter is constructed over the ruins of the reactor building. The two "Mammoth Beams" that support the roof of the shelter rest partly on the structurally unsound west wall of the reactor building that was damaged by the accident. The western end of the shelter roof is supported by a wall at a point designated axis 50. This wall is reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
, and was cracked by the accident. In December 2006 the "Designed Stabilisation Steel Structure" (DSSS) was extended until 50% of the roof load (about 400 tons) was transferred from the axis 50 wall to the DSSS. The DSSS is a yellow steel object that has been placed next to the wrecked reactor; it is 63 metres (207 ft) tall and has a series of cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
s that extend through the western buttress
Buttress
A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall...
wall, and is intended to stabilize the sarcophagus. This was done because if the wall of the reactor building or the roof of the shelter were to collapse, then large amounts of radioactive dust and particles would be released directly into the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, resulting in a large new release of radioactivity into the environment.
A further threat to the shelter is the concrete slab that formed the "Upper Biological Shield" (UBS), situated above the reactor prior to the accident. This concrete slab was thrown upwards by the explosion
Explosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
in the reactor core and now rests at approximately 15° from vertical. The position of the upper bioshield is considered inherently unsafe, as only debris supports it in its nearly upright position. A collapse of the bioshield would further exacerbate the dust conditions in the shelter, possibly spreading some quantity of radioactive materials out of the shelter, and could damage the shelter itself. The UBS is a circle 15 meters in diameter, weighing 1000 tons and consisting of 2000 cubes, each located above a fuel channel. The shield, called Pyatachok ("five kopek
Soviet ruble
The Soviet ruble or rouble was the currency of the Soviet Union. One ruble is divided into 100 kopeks, ....
coin") before the disaster, was afterwards named Component "E" and nicknamed "Elena"; the twisted fuel bundles still attached to it are called "Elena's hair."
Wildlife status
The Exclusion Zone around the Chernobyl nuclear power station is reportedly a haven for wildlifeWildlife
Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....
. As humans were evacuated from the area 25 years ago, existing animal populations multiplied and rare species not seen for centuries have returned or have been reintroduced, for example lynx
Lynx
A lynx is any of the four Lynx genus species of medium-sized wildcats. The name "lynx" originated in Middle English via Latin from Greek word "λύγξ", derived from the Indo-European root "*leuk-", meaning "light, brightness", in reference to the luminescence of its reflective eyes...
, wild boar, wolf, Eurasian brown bear
Eurasian Brown Bear
The Eurasian brown bear is a subspecies of brown bear, found across northern Eurasia. The Eurasian brown bear is also known as the common brown bear, European brown bear and colloquially by many other names....
, European bison, Przewalski's horse, and eagle owl. Birds even nest inside the cracked concrete sarcophagus shielding in the shattered remains of Reactor 4. The Exclusion Zone is so lush with wildlife and greenery that in 2007 the Ukrainian government designated it a wildlife sanctuary, and at 488.7 km2 it is one of the largest wildlife sanctuaries in Europe.
According to a 2005 U.N. report, wildlife has returned despite radiation levels that are presently 10 to 100 times higher than normal background radiation
Background radiation
Background radiation is the ionizing radiation constantly present in the natural environment of the Earth, which is emitted by natural and artificial sources.-Overview:Both Natural and human-made background radiation varies by location....
. Although they were significantly higher soon after the accident, the levels have fallen because of radioactive decay
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
.
Biologist Anders Møller from the University of Paris
University of Paris
The University of Paris was a university located in Paris, France and one of the earliest to be established in Europe. It was founded in the mid 12th century, and officially recognized as a university probably between 1160 and 1250...
Sud in France has been examining the effects of radiation on animals around Chernobyl
Chernobyl
Chernobyl or Chornobyl is an abandoned city in northern Ukraine, in Kiev Oblast, near the border with Belarus. The city had been the administrative centre of the Chernobyl Raion since 1932....
for two decades.
"Areas with higher radiation have fewer animals, survival and reproduction is reduced, sperm are abnormal and have reduced swimming ability. Abnormalities are commonplace and mutations rates are much elevated," Møller said.
Last year, Møller and Tim Mousseau published the results of the largest census of animal life in the Chernobyl Exclusion Zone http://cricket.biol.sc.edu/chernobyl/Chernobyl_Research_Initiative/Introduction.html. It revealed, contrary to the Chernobyl Forum's 2005 reporthttp://www-ns.iaea.org/downloads/rw/meetings/chern-forum-3rd-meetings-statement-rev.pdf, that biodiversity in insects, birds and mammals is declining.
Not all species are affected by radiation in the same way according to Møller. Some birds -- including migrant species and long distance dispersers -- are more vulnerable to radiation than others, he said.
Martin Hajduch said animal numbers in the exclusion zone are probably higher now than before the accident. But that's because there are no humans there hunting or fishing.
"But if you look at how many species of animals are in the area, I think it would be less," Hajduch said.http://www.cnn.com/2011/WORLD/europe/01/14/chernobyl.nature.radiation.debate/index.html
Some researchers say that by halting the destruction of habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
, the Chernobyl disaster helped wildlife flourish. Biologist Robert J. Baker of Texas Tech University
Texas Tech University
Texas Tech University, often referred to as Texas Tech or TTU, is a public research university in Lubbock, Texas, United States. Established on February 10, 1923, and originally known as Texas Technological College, it is the leading institution of the Texas Tech University System and has the...
was one of the first to report that Chernobyl had become a wildlife haven and that many rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s he has studied at Chernobyl since the early 1990s have shown remarkable tolerance for elevated radiation levels.
Møller et al. (2005) suggested that reproductive success and annual survival rates of barn swallows
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
are much lower in the Chernobyl exclusion zone; 28% of barn swallows inhabiting Chernobyl return each year, while at a control area at Kanev 250 km to the southeast, the return rate is around 40%. A later study by Møller et al. (2007) furthermore claimed an elevated frequency of 11 categories of subtle physical abnormalities in barn swallows, such as bent tail feather
Flight feather
Flight feathers are the long, stiff, asymmetrically shaped, but symmetrically paired feathers on the wings or tail of a bird; those on the wings are called remiges while those on the tail are called rectrices . Their primary function is to aid in the generation of both thrust and lift, thereby...
s, deformed air sacs, deformed beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
s, and isolated albinistic feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s.
Smith et al. (2007) have disputed Møller's findings and instead proposed that a lack of human influence in the exclusion zone locally reduced the swallows' insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
prey and that radiation levels across the vast majority of the exclusion zone are now too low to have an observable negative effect. But the criticisms raised were responded to in Møller et al. (2008). It is possible that barn swallows are particularly vulnerable to elevated levels of ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
because they are migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
; they arrive in the exclusion area exhausted and with depleted reserves of radio-protective antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
s after an arduous journey.
Several research groups have suggested that plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s in the area have adapted to cope with the high radiation levels, for example by increasing the activity of DNA cellular repair
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
machinery and by hypermethylation
DNA methylation
DNA methylation is a biochemical process that is important for normal development in higher organisms. It involves the addition of a methyl group to the 5 position of the cytosine pyrimidine ring or the number 6 nitrogen of the adenine purine ring...
. (see Radiation Hormesis
Radiation hormesis
Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation...
). Given the uncertainties, further research is needed to assess the long-term health effects of elevated ionizing radiation from Chernobyl on flora and fauna.
Grass and forest fires
It is known that fireFire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
s can make radioactivity mobile again. In particular V.I. Yoschenko et al. reported on the possibility of increased mobility of caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
, strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
, and plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
due to grass
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
and forest fires. As an experiment, fires were set and the levels of the radioactivity in the air downwind of these fires was measured.
Grass and forest fires have happened inside the contaminated zone, releasing radioactive fallout into the atmosphere. In 1986 a series of fires destroyed 23.36 km2 (5,772 acres) of forest, and several other fires have since burned within the 30 km (19 mi) zone. A serious fire in early May 1992 affected 5 km2 (1,240 acres) of land including 2.7 km2 (670 acres) of forest. This resulted in a great increase in the levels of caesium-137
Caesium-137
Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed...
in airborne dust.
In 2010, a series of wildfires
2010 Russian wildfires
The 2010 Russian wildfires were several hundred wildfires that broke out across Russia, primarily in the west, starting in late July 2010, due to record temperatures and drought in the region...
affected contaminated areas, specifically the surroundings of Bryansk
Bryansk
Bryansk is a city and the administrative center of Bryansk Oblast, Russia, located southwest of Moscow. Population: -History:The first written mention of Bryansk was in 1146, in the Hypatian Codex, as Debryansk...
and border regions with Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
and Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
. The Russian government claims that there has been no discernible increase in radiation levels, while Greenpeace
Greenpeace
Greenpeace is a non-governmental environmental organization with offices in over forty countries and with an international coordinating body in Amsterdam, The Netherlands...
accuses the government of denial.
See also
- Chernobyl disaster effectsChernobyl disaster effectsThe Chernobyl disaster triggered the release of substantial amounts of radiation into the atmosphere in the form of both particulate and gaseous radioisotopes. It is the most significant unintentional release of radiation into the environment to date...
- Chernobyl Shelter FundChernobyl Shelter FundThe Chernobyl Shelter Fund was set up in December 1997 with the purpose of funding the Shelter Implementation Plan . The main objective of the SIP, developed in a co-operative effort between the European Union, the United States and Ukraine, is to protect the personnel, population and environment...
- Liquidator (Chernobyl)Liquidator (Chernobyl)Liquidators , or "clean-up workers", is the name given in the former USSR to people who were called upon to work in efforts to deal with consequences of the April 26, 1986, Chernobyl disaster on the site of the event...
- List of Chernobyl-related articles
- Red ForestRed ForestThe Red Forest , formerly the Worm Wood Forest, refers to the trees in the 10 km² surrounding the Chernobyl Nuclear Power Plant. The name 'Red Forest' comes from the ginger-brown colour of the pine trees after they died following the absorption of high levels of radiation from the Chernobyl...
(Wormwood Forest) - Threat of the Dnieper reservoirsThreat of the Dnieper reservoirsThe water reservoirs of the Dnieper River in Ukraine pose a significant threat of a large-scale human-made disaster if their dams fail. Such a threat is typical for reservoir dams; however, the Dnieper reservoirs are especially dangerous because of the geographical conditions, as well as the...
- Ukrainian National Chernobyl MuseumUkrainian National Chernobyl MuseumThe Ukrainian National Chernobyl Museum is a museum dedicated to the Chernobyl disaster. The museum is located in the city of Kiev, Ukraine....
- Zone of alienationZone of alienationThe Chernobyl Nuclear Power Plant Zone, which is sometimes referred to as The Chernobyl Zone, The 30 Kilometer Zone, The Zone of Alienation, or simply The Zone The Chernobyl Nuclear Power Plant Zone, which is sometimes referred to as The Chernobyl Zone, The 30 Kilometer Zone, The Zone of...
(Exclusion Zone)