This article compares the radioactivity release and decay from the

Chernobyl disaster The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. It is one of only two nuc ...

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 due to

potassium-40 Potassium-40 (40K) is a radioactive isotope of potassium which has a long half-life of 1.25 billion years. It makes up about 0.012% (120 ppm) of the total amount of potassium found in nature. Potassium-40 undergoes three types of radioactive de ...

but all foods contain carbon and thereby

carbon-14 Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...

), radon gas, granite and other dense rocks, and others. The

banana equivalent dose Banana equivalent dose (BED) is an informal unit of measurement of ionizing radiation exposure, intended as a general educational example to compare a dose of radioactivity to the dose one is exposed to by eating one average-sized banana. Bananas ...

is sometimes used in

science communication Science communication is the practice of informing, educating, raising awareness of science-related topics, and increasing the sense of wonder about scientific discoveries and arguments. Science communicators and audiences are ambiguously def ...

to visualize different levels of ionizing radiation. 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, particularly 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 The roentgen equivalent man (rem) is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body. Quantities measur ...

(

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

) to 38 mrem (portions of

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

Chernobyl compared with an atomic bomb

Far fewer people died as an immediate result of the Chernobyl event than the immediate deaths from radiation at Hiroshima. Chernobyl is eventually predicted to result in up to 4,000 total

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

s from cancer, sometime in the future, according to the

WHO Who or WHO may refer to: * Who (pronoun), an interrogative or relative pronoun * Who?, one of the Five Ws in journalism * World Health Organization Arts and entertainment Fictional characters * Who, a creature in the Dr. Seuss book ''Horton Hear ...

and create around 41,000 excess cancer according to the

International Journal of Cancer The ''International Journal of Cancer'' is a biweekly peer-reviewed medical journal covering experimental and clinical cancer research. It publishes original research articles, mini reviews, short reports, and letters to the editor. The journal was ...

, with, depending on treatment, not all cancers resulting in death. Due to the differences in

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

, the different

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...

fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

undergo

exponential decay A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the following differential equation, where is the quantity and (lambda) is a positive rate ...

at different rates. Hence the isotopic signature of an event where more than one radioisotope is involved will change with time. "Compared with other nuclear events: The Chernobyl explosion put 400 times more radioactive material into the Earth's atmosphere than the atomic bomb dropped on Hiroshima; atomic weapons tests conducted in the 1950s and 1960s all together are estimated to have put some 100 to 1,000 times more radioactive material into the atmosphere than the Chernobyl accident." 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 A ground burst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb that explodes at ground level. These weapons are set off by fuses that are activated when the weapon strikes the ground or some ...

of a bomb similar to the

Fat Man "Fat Man" (also known as Mark III) is the codename for the type of nuclear bomb the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the fir ...

device dropped on Nagasaki. 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

of an implosion-based

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...

bomb which has a

depleted uranium Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy or D-38) is uranium with a lower content of the fissile isotope than natural uranium.: "Depleted uranium possesses only 60% of the radioactivity of natural uranium, hav ...

tamper. The fission was assumed to have been caused by 1 MeV neutrons and 20% occurred in the ²³⁸U tamper of the bomb. It was assumed, for the sake of simplicity, that no plume separation of the

isotopes Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

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. Note that in the event of a low altitude or ground bursted nuclear detonation that fractionation of the volatile and non volatile radionuclides occurs, also during the Chernobyl accident the ratio between the different elements released by the accident did change as a function of time. A

of a nuclear weapon creates considerably more local deposited fallout than the

air burst An air burst or airburst 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. The principal military advantage of an air burst over ...

s used at Hiroshima or Nagasaki. This is due in part to

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emittin ...

of ground soil and greater amounts of soil being sucked into the nuclear fireball in a ground burst than in a high air burst. In the above

is neglected, and only the

fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

fraction of the total activity resulting from the ground burst is shown.

Chernobyl compared with Tomsk-7

The release of radioactivity which occurred at

Tomsk-7 Seversk ( rus, Се́верск, p=ˈsʲevʲɪrsk) is a closed city in Tomsk Oblast, Russia, located northwest of Tomsk on the right bank of the Tom River. Population: It was previously known as ''Pyaty Pochtovy'' (until 1949) and ''Tomsk-7'' ...

(an industrial nuclear complex located in

Seversk Seversk ( rus, Се́верск, p=ˈsʲevʲɪrsk) is a closed city in Tomsk Oblast, Russia, located northwest of Tomsk on the right bank of the Tom River. Population: It was previously known as ''Pyaty Pochtovy'' (until 1949) and ''Tomsk-7'' ...

rather than the city of Tomsk) in 1993 is another comparison with the Chernobyl release. During reprocessing activities, some of the feed for the second cycle (medium active part) of the

PUREX PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons. PUREX is the ''de facto'' standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium fr ...

process escaped in an accident involving

red oil {{See also, PUREX Red oil is defined as a substance of varying composition formed when an organic solution, typically tri-n-butyl phosphate (TBP, an agent used for extracting heavy metals in nuclear reprocessing plants) and its diluent, comes in c ...

. According to the

IAEA The International Atomic Energy Agency (IAEA) is an intergovernmental organization that seeks to promote the peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. It was established in 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 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, known commonly as TBP, is an organophosphorus compound with the chemical formula (CH3CH2CH2CH2O)3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of phosphoric aci ...

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

organic phase used in the first liquid-liquid extraction cycle of the PUREX process. The second cycle is normally to clean up the

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

and

product. In the PUREX process some

zirconium Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...

technetium Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous ...

, 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 is a chemical element with the Symbol (chemistry), 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 ...

(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

Chernobyl compared to Fukushima Daiichi

Chernobyl compared with the Goiânia accident

While both events released ¹³⁷Cs, the isotopic signature for the

Goiânia accident The Goiânia accident was a radioactive contamination accident that occurred on September 13, 1987, in Goiânia, Goiás, Brazil, after a forgotten radiotherapy source was stolen from an abandoned hospital site in the city. It was subsequent ...

was much simpler. It was a single isotope which has a

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. Chernobylvsru106

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 design flaw-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 shattering when refilled rapidly with coolant. Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material.

Containment Containment was a geopolitical strategic foreign policy pursued by the United States during the Cold War to prevent the spread of communism after the end of World War II. The name was loosely related to the term ''cordon sanitaire'', which was ...

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 The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...

and the present day, a series of accidents have occurred in which nuclear criticality has played a central role. The

criticality accident A criticality accident is an accidental uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, or divergent chain reaction. Any such event involves the unintended accumulation ...

s may be divided into two classes. For more details see nuclear and radiation accidents. A review of the topic was published in 2000
"A Review of Criticality Accidents"
by

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...

(Report LA-13638), May 2000. Coverage includes United States, Russia, United Kingdom, and Japan. Also available a
this page
which also tries to track down documents referenced in the report.
Press release on a report on criticality accidents from Los Alamos National Laboratory

Process accidents

In the first class (process accidents) during the processing of

fissile In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. The predominant neutron energy may be typ ...

material, accidents have occurred when a

critical mass In nuclear engineering, 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 (specifically, its nuclear fissi ...

has been created by accident. For instance at

Charlestown, Rhode Island Charlestown is a town in Washington County, Rhode Island, United States. The population was 7,997 at the 2020 census. History Charlestown is named after King Charles II, and was incorporated in 1738. The area was formerly part of the town ...

, United States, on July 24, 1964, one death occurred. 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. Radioactivity was released as a result of the Tokaimura accident. 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

remained in the vessel. These accidents tend to lead to very high doses due to direct

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 ...

of the workers within the site, but due to the

inverse square law In science, an inverse-square law is any scientific law stating that a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity. The fundamental cause for this can be understoo ...

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.

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 ( or ; ), officially the Autonomous City of Buenos Aires ( es, link=no, Ciudad Autónoma de Buenos Aires), is the capital and primate city of Argentina. The city is located on the western shore of the Río de la Plata, on South ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

, on September 23, 1983 (one death), and during the

Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...

several people were irradiated (two,

Harry Daghlian Haroutune Krikor Daghlian Jr. (May 4, 1921 – September 15, 1945) was an American physicist with the Manhattan Project, which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 2 ...

and

Louis Slotin Louis Alexander Slotin (1 December 1910 – 30 May 1946) was a Canadian physicist and chemist who took part in the Manhattan Project. Born and raised in the North End of Winnipeg, Manitoba, Slotin earned both his Bachelor of Science and M ...

, were irradiated fatally) during "tickling the dragon's tail" experiments. These accidents tend to lead to very high doses due to direct

of the workers within the site, but due to the

the dose suffered by members of the

general public In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of such groupings. This is a different concept to the sociological concept of the ''Öffentlichkei ...

tends to be very small. Also, very little environmental contamination normally occurs as a result of these accidents. For instance, at

Sarov Sarov (russian: Саро́в) is a closed town in Nizhny Novgorod Oblast, Russia. It was known as Gorkiy-130 (Горький-130) and Arzamas-16 (), after a (somewhat) nearby town of Arzamas,SarovLabsCreation of Nuclear Center Arzamas-16/ref ...

the radioactivity remained confined to within the

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 first element in the series, actinium. The inform ...

metal objects which were part of the experimental system, according to the

report (2001).The criticality accident in Sarov
/ref> Even the

SL-1 Stationary Low-Power Reactor Number One, also known as SL-1 or the Argonne Low Power Reactor (ALPR), was a United States Army experimental nuclear reactor in the western United States at the National Reactor Testing Station (NRTS), later the ...

accident (RIA, power surge in an experimental nuclear reactor in Idaho, 1961) failed to release much radioactivity outside the building in which it occurred.

References

{{Chernobyl disaster * Environmental impact of nuclear power *