This article compares the radioactivity release and decay from the

Chernobyl disaster On 26 April 1986, the no. 4 reactor of the Chernobyl Nuclear Power Plant, located near Pripyat, Ukrainian Soviet Socialist Republic, Ukrainian SSR, Soviet Union (now Ukraine), exploded. With dozens of direct casualties, it is one of only ...

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

Chernobyl compared to background radiation

Natural sources of radiation are prevalent in the environment, and come from cosmic rays, food sources (bananas have a particularly high source due to

potassium-40 Potassium-40 (K) is a long lived and the main naturally occurring radioactive isotope of potassium. Its half-life is 1.25 billion years. It makes up about 0.012% (120 parts-per notation, ppm) of natural potassium. Potassium-40 undergoes four dif ...

but all foods contain carbon and thereby

carbon-14 Carbon-14, C-14, C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter 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 encompasses a wide range of activities that connect science and society. Common goals of science communication include informing non-experts about scientific findings, raising the Public awareness of science, public awar ...

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 massively higher doses. Chernobyl's radiation was detectable across Western Europe. Average doses received ranged from 0.02 mrem (

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

) to 38 mrem (portions of

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

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 end of life; the irreversible cessation of all biological functions that sustain a living organism. Death eventually and inevitably occurs in all organisms. The remains of a former organism normally begin to decompose sh ...

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

WHO The World Health Organization (WHO) is a specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 15 ...

and create around 41,000 excess cancer according to the International Journal of Cancer, with, depending on treatment, not all cancers resulting in death. Due to the differences in

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

, 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 conside ...

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 releas ...

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 Lambda (; uppe ...

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 so ...

of a bomb similar to the

Fat Man "Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare. A Fat Man ...

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 created 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. The 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 chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...

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 Uranium-235, 235U than natural uranium. The less radioactive and non-fissile Uranium-238, 238U is the m ...

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 distinct nuclear species (or ''nuclides'') of the same chemical element. They 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), but ...

occurred between the detonation and the deposit of

radioactivity 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 conside ...

. 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 burst 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 changed 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 emi ...

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 releas ...

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 (an industrial nuclear complex located in

Seversk Seversk (, ) is a closed city in Tomsk Oblast, Russia, located northwest of Tomsk on the right bank of the Tom River. The population was 108,590 at the 2010 census and 109,106 at the 2002 census. It was previously known as ''Pyaty Pochtovy' ...

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. It is based on liquid–liquid extraction ion-exchange. PUREX is the '' de facto'' standard aqueous nuclear reproc ...

process escaped in an accident involving red oil. 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: Chernobylvstomsk

*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 at a small concentration. This is because it is not able to enter the tributyl phosphate/

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 Hydrophobe, hydrophobic; their odor is usually fain ...

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; it has chemical symbol, 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. Ura ...

and

product. In the PUREX process, some

zirconium Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...

technetium Technetium is a chemical element; it has Symbol (chemistry), symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense ...

, 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; it has 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 unreactive to most chem ...

(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 an unsecured radiation therapy, radiotherapy source was stolen from an abandoned hospital site in the city. ...

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 adjacent 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. However, both accidents have vague similarities. 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 – caused by the technical malfunction of a pilot-operated relief valve – which lowered the water level around the nuclear fuel, resulting in over a third of it shattering when refilled rapidly with coolant. Similar to Chernobyl, operator error played a role but did not directly cause the accident. Both accidents had grueling and costly cleanup efforts. Chernobyl and TMI's unaffected reactors were restarted and continued operation until 2000 and 2019, respectively. Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material.

Containment Containment was a Geopolitics, 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 ...

at TMI was not breached. On the day of the accident, a small "hydrogen burn" occurred inside the reactor building, but it was not enough to affect normal operation of the reactor. Following the accident, an estimated 44,000 curies of radioactive gases – particularly

Krypton-85 Krypton-85 (85Kr) is a radioisotope of krypton. Krypton-85 has a half-life of 10.756 years and a maximum decay energy of 687 keV. It decays into stable rubidium-85. Its most common decay (99.57%) is by beta particle emission with a maximum ene ...

– 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 program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the ...

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, divergent chain reaction, or simply critical. Any such event involves the uninten ...

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 Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...

(Report LA-13638), May 2000. Coverage includes United States, Russia, United Kingdom, and Japan. Also available at , 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 that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal Nuclear chain reaction#Fission chain reaction, chain reaction can only be achieved with fissil ...

material, accidents have occurred when a

critical mass In nuclear engineering, critical mass is the minimum mass of the fissile material needed for a sustained nuclear chain reaction in a particular setup. The critical mass of a fissionable material depends upon its nuclear properties (specific ...

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. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...

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 the observed "intensity" of a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity. The fundamental cau ...

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, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

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

Manhattan Project The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. From 1942 to 1946, the ...

several people were irradiated (two, Harry Daghlian and Louis Slotin, 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 () is a closed city, 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> from 194 ...

the radioactivity remained confined to within the

actinide The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...

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

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

SL-1 Stationary Low-Power Reactor Number One, also known as SL-1, initially the Argonne Low Power Reactor (ALPR), was a United States Army experimental nuclear reactor in the Western United States, western United States at the Idaho National Laborato ...

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 *