Chernobyl compared to other radioactivity releases
Encyclopedia
This article compares the radioactivity release and decay from the Chernobyl disaster
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...

 with various other events which involved a release of uncontrolled radioactivity.

Chernobyl compared to background radiation

Natural sources of radiation are very prevalent in the environment, and come from cosmic rays, food sources (bananas have a particular high source), radon gas, granite and other dense rocks, and others. The collective radiation background dose for natural sources in Europe is about 500,000 man Sieverts per year. The total dose from Chernobyl is estimated at 80,000 man sieverts, or roughly 1/6 as much. However, some individuals, particular in areas adjacent the reactor, received significantly higher doses.

Chernobyl's radiation was detectable across Western Europe. Average doses received ranged from 0.02 mrem (Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

) to 38 mrem (portions of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

).

Chernobyl compared with an atomic bomb

Far fewer people died as an immediate result of the Chernobyl event than died of radiation at Hiroshima
Atomic bombings of Hiroshima and Nagasaki
During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan, the first on August 6, 1945, and the second on August 9, 1945. These two events are the only use of nuclear weapons in war to date.For six months...

, and the eventual total is also significantly less when including those predicted by the WHO
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 to die in the future . Due to the differences in half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 the different radioactive fission products undergo exponential decay at different rates. Hence the isotopic signature of an event where more than one radioisotope is involved will change with time.

Some comments have been made in which the radioactive release of the Chernobyl event is claimed to be 300 or 400 times that of the bomb dropped on Hiroshima
Hiroshima
is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshu, the largest island of Japan. It became best known as the first city in history to be destroyed by a nuclear weapon when the United States Army Air Forces dropped an atomic bomb on it at 8:15 A.M...

. The work of SCOPE suggests that the two events can not be simply compared with a number suggesting that one was XX times larger than the other.

The radioactivity released at Chernobyl tended to be more long lived than that released by a bomb detonation hence it is not possible to draw a simple comparison between the two events. Also, a dose of radiation spread over many years (as is the case with Chernobyl) is much less harmful than the same dose received over a short period.
The relative size of the Chernobyl release when compared with the release due to a hypothetical ground burst
Ground burst
A groundburst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb that explodes upon hitting the ground...

 of a bomb similar to the Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...

 device dropped on Nagasaki. A ground burst creates considerably more fallout than the air burst
Air burst
An air burst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target or a delayed armor piercing explosion....

s used at Hiroshima or Nagasaki .
Isotope Ratio between the release due to the bomb and the Chernobyl accident
90Sr 1:87
137Cs 1:890
131I 1:25
133Xe 1:31


A comparison of the gamma dose rates due to the Chernobyl accident and the hypothetical nuclear weapon.



The graph of dose rate as a function of time for the bomb fallout was done using a method similar to that of T. Imanaka, S. Fukutani, M. Yamamoto, A. Sakaguchi and M. Hoshi, J. Radiation Research, 2006, 47, Suppl A121-A127. Our graph exhibits the same shape as that obtained in the paper. The bomb fallout graph is for a ground burst
Ground burst
A groundburst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb that explodes upon hitting the ground...

 of an implosion-based 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...

 bomb which has a depleted uranium
Depleted uranium
Depleted uranium is uranium with a lower content of the fissile isotope U-235 than natural uranium . Uses of DU take advantage of its very high density of 19.1 g/cm3...

 tamper
Tamper
Tamper can mean:*Tamp, a device used to compact or flatten an aggregate or other powdered or granular material, like ground coffee or gravel*A tool used to pack tobacco into a smoking pipe, as well as to flatten or scoop the ash; usually nail-shaped and sometimes combined into a pipe tool*Ballast...

. The fission was assumed to have been caused by 1 MeV neutrons and 20% occurred in the 238U tamper of the bomb. It is assumed that no separation of the isotopes occurred between the detonation and the deposit of radioactivity. The following gamma-emitting isotopes are modeled 131I, 133I, 132Te, 133I, 135I, 140Ba, 95Zr, 97Zr, 99Mo, 99mTc, 103Ru, 105Ru, 106Ru, 142La, 143Ce, 137Cs, 91Y, 91Sr, 92Sr, 128Sb and 129Sb. The graph ignores the effects of beta emission and shielding. The data for the isotopes was obtained from the Korean table of the isotopes. The graphs for the Chernobyl accident were computed by an analogous method.

Chernobyl compared with Tomsk-7

The release of radioactivity which occurred at Tomsk-7 (an industrial nuclear complex located in Seversk
Seversk
Seversk is a closed city in Tomsk Oblast, Russia, located northwest of Tomsk on the right bank of the Tom River. Population: Founded in 1949, it was known as Pyaty Pochtovy until 1954 and as Tomsk-7 until 1992. Town status was granted to it in 1956.The current Chair of the City Duma and Mayor...

 rather than the city of Tomsk) is another comparison with the Chernobyl release. During reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...

 activities, some of the feed for the second cycle (medium active part) of the PUREX
PUREX
PUREX is an acronym standing for Plutonium - URanium EXtraction — de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange.The PUREX process was invented by Herbert H. Anderson and...

 process escaped in an accident involving red oil
Red oil
Red oil is defined as a substance of varying composition formed when an organic solution, typically tri-n-butyl phosphate and its diluent, comes in contact with concentrated nitric acid at a temperature above 120 °C.Red oil is relatively stable below 130 °C, but it can decompose explosively when its...

. According to the IAEA
International Atomic Energy Agency
The International Atomic Energy Agency is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons. The IAEA was established as an autonomous organization on 29 July 1957...

 it was estimated that the following isotopes were released from the reaction vessel:
  • 106Ru 7.9 TBq
  • 103Ru 340 GBq
  • 95Nb 11.2 TBq
  • 95Zr 5.1 TBq
  • 137Cs 505 GBq (estimated from the IAEA data)
  • 141Ce 370 GBq
  • 144Ce 240 GBq
  • 125Sb 100 GBq
  • 239Pu 5.2 GBq


It is important to note that the very short lived isotopes such as 140Ba and 131I were absent from this mixture, and the long lived 137Cs was only at a small concentration. This is because it is not able to enter the tributyl phosphate
Tributyl phosphate
Tributyl phosphate, known commonly as TBP, is an organophosphorus compound with the formula 3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of orthophosphoric acid with n-butanol.- Production :Tributyl phosphate is manufactured by...

/hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

 organic phase used in the first liquid-liquid extraction
Liquid-liquid extraction
Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid phase into another liquid...

 cycle of the PUREX process. The second cycle is normally to clean up the uranium
Uranium
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...

 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...

 product. In the PUREX process some zirconium
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...

, technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...

 and other elements are extracted by the tributyl phosphate. Due to the radiation induced degradation of tributyl phosphate the first cycle organic phase is always contaminated with ruthenium
Ruthenium
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The Russian scientist Karl Ernst Claus discovered the element...

 (later extracted by dibutyl hydrogen phosphate). Because the very short lived radioisotopes and the relatively long lived caesium isotopes are either absent or in low concentrations the shape of the dose rate vs. time graph is different from Chernobyl both for short times and long times after the accident.

The size of the radioactive release at Tomsk-7 was much smaller, and while it caused moderate environmental contamination it did not cause any early death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

s.

Chernobyl compared with the Goiânia accident

While both events released 137Cs, the isotopic signature for the Goiânia accident
Goiânia accident
The Goiânia accident was a radioactive contamination accident that occurred on September 13, 1987, at Goiânia, in the Brazilian State of Goiás after an old radiotherapy source was taken from an abandoned hospital site in the city...

 was much simpler. It was a single isotope which has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of about 30 years. To show how the activity vs. time graph for a single isotope differs from the dose rate due to Chernobyl (in the open air) the following chart is shown with calculated data for a hypothetical release of 106Ru.

Chernobyl compared with the Three Mile Island accident

Three Mile Island-2 was an accident of a completely different type from Chernobyl. Chernobyl was a human-caused power excursion causing a steam explosion resulting in a graphite fire, uncontained, which lofted radioactive smoke high into the atmosphere; TMI was a slow, undetected leak that lowered the water level around the nuclear fuel, resulting in over a third of it melting. Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material. Containment
Containment building
A containment building, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi...

 at TMI did not fail. A small quantity of radioactive gases from the leak were vented into the atmosphere through specially designed filters under operator control. A government report concluded that the accident caused no increase in cancer rates for local residents.

Chernobyl compared with criticality accidents

During the time between the start of the Manhattan project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

 and the present day, a series of accidents have occurred in which nuclear criticality has played a central role. The criticality accidents may be divided into two classes. For more details see nuclear and radiation accidents. A good review of the topic was published in 2000, "A Review of Criticality Accidents" by Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...

 (Report LA-13638), May 2000. Coverage includes United States, Russia, United Kingdom, and Japan. Also available at this page, which also tries to track down documents referenced in the report.

Process accidents

In the first class (process accidents) during the processing of fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...

 material, accidents have occurred when a critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...

 has been created by accident. For instance at Charlestown
Charlestown, Rhode Island
Charlestown is a town in Washington County, Rhode Island, United States. The population was 7,827 at the 2010 census.-History:Charlestown is named after King Charles II, and was incorporated in 1738. The area was formerly part of the town of Westerly...

, Rhode Island
Rhode Island
The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...

, United States on July 24, 1964 one death occurred and at Tokaimura, Japan, nuclear fuel reprocessing plant, on September 30, 1999 two deaths and one non fatal overexposure occurred as result of accidents where too much fissile matter was placed in a vessel. These accidents tend to lead to very high doses due to direct irradiation
Irradiation
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to...

 of the workers within the site, but due to the inverse square law the dose suffered by members of the general public tends to be very small. Also very little environmental contamination normally occurs as a result of these accidents. A release of radioactivity occurred as a result of the Tokaimura event. The building in which the accident occurred was not designed as a containment building, yet it was able to retard the spread of radioactivity. Because the temperature rise in the nuclear reaction vessel was small, the majority of the fission products remained in the vessel.

Reactor accidents

In this type of accident a reactor or other critical assembly releases far more fission power than was expected, or it becomes critical at the wrong moment in time. The series of examples of such events include one in an experimental facility in Buenos Aires
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...

, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

, on September 23, 1983 (one death) and during the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

 several people were irradiated (two, Harry K. Daghlian and Louis Slotin
Louis Slotin
Louis Alexander Slotin was a Canadian physicist and chemist who took part in the Manhattan Project, the secret US program during World War II that developed the atomic bomb....

, fatally) during "tickling the dragon's tail
Demon core
The Demon core was the nickname given to a subcritical mass of plutonium that accidentally went briefly critical in two separate accidents at the Los Alamos laboratory in 1945 and 1946. Each incident resulted in the acute radiation poisoning and subsequent death of a scientist...

" experiments. These accidents tend to lead to very high doses due to direct irradiation
Irradiation
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to...

 of the workers within the site, but due to the inverse square law the dose suffered by members of the general public
General Public
General Public were a band formed by The Beat vocalists, Dave Wakeling and Ranking Roger, and which included former members of Dexy's Midnight Runners, The Specials and The Clash...

 tends to be very small. Also very little environmental contamination normally occurs as a result of these accidents. For instance at Sarov
Sarov
Sarov is a closed town in Nizhny Novgorod Oblast, Russia. Until 1995 it was known as Kremlyov ., while from 1946 to 1991 it was called Arzamas-16 . The town is off limits to foreigners as it is the Russian center for nuclear research. Population: -History:The history of the town can be divided...

 according to the IAEA report (2001) the radioactivity remained confined to within the actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...

 metal objects which were part of the experimental system. Even the SL-1
SL-1
The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the central control rod, responsible for...

 accident failed to release much radioactivity outside the building in which it occurred.

See also

  • 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....

  • Chernobyl Children's Project International
    Chernobyl Children's Project International
    Chernobyl Children's Project International is a United Nations-accredited international development, medical, and humanitarian organization that works with children, families and communities that continue to be affected by the Chernobyl nuclear disaster of 1986.- Purpose :The organization was...

  • Chernobyl disaster effects
    Chernobyl disaster effects
    The 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 Heart
    Chernobyl Heart
    Chernobyl Heart is a 2003 documentary film by Maryann DeLeo. The film won the Best Documentary Short Subject award at the 2004 Academy Awards....

  • 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...

  • 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
  • Nuclear power debate
    Nuclear power debate
    The nuclear power debate is about the controversy which has surrounded the deployment and use of nuclear fission reactors to generate electricity from nuclear fuel for civilian purposes...

  • International Nuclear Event Scale
    International Nuclear Event Scale
    The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....

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