Chernobyl information sheet

An unparalleled nuclear disaster

In 80 years of civilian nuclear power, Chernobyl is the most serious accident ever to have occurred at a nuclear power plant and to have resulted in radiation casualties

An explosion and then a fire in the open air.
Sudden emission of radioactive products into the atmosphere.
Radioactive elements in most European countries.
Health consequences have long been confined, but are still under study.

A major event for the nuclear industry, public opinion, and the global energy landscape

Source of lessons for safety: human factor, safety culture, management of a serious accident, crisis management. But also =>
Source of major questioning of nuclear energy around the world: moratoriums, nuclear exit policy, interruption of research efforts
Source of confusion between archives, memories, instrumentalization and integration into pop culture.
It remains the industrial event that people around the world cite as the most frightening, despite being not even close to the most serious

The nuclear accident at a glance

Chernobyl is classified (after the fact) INES 7 [TMI classified INES 5 (1979), Blayais classified INES 2 (1999), Fukushima classified INES 7 (2011)].
April 26, 1986: accident on the RBMK No.4 reactor of the Chernobyl nuclear power plant in the USSR (Ukraine).
2 days later: detection of an abnormal level of radioactivity at the Forsmark nuclear power plant in Sweden.
Following a test that led to a power excursion (reactor out of control), the reactor was destroyed by a steam explosion, followed by a hydrogen explosion. The building and overpressure protection were destroyed. A fire, particularly a graphite fire, took days to be totally controlled.
The radioactive plume from Chernobyl spread radioactive elements over most of Europe.
An exclusion zone was declared in a 30 km radius around the damaged reactor. People living in this area were evacuated and agricultural activity was prohibited. Access to this area is still controlled today.

Consequences for the population

Radiological health impact

Deaths directly caused by the accident

The initial steam explosion caused the death of 2 workers.
Of the 600 workers present at the site on the day of the accident, 134 personnel and emergency responders were affected by acute radiation syndrome due to the high doses of radiation received:
- 29 died within 4 months of the accident,
- 19 died within the next 20 years.
In 2005 there were 15 deaths from thyroid cancers attributed to radiation exposure.

Other health impacts

Exposure
- of workers (~600,000) who participated in the decontamination operation on the site between 1986 and 1990: doses of 120 mSv on average (between 20 and 500 mSv, 10% received > 250 mSv).
- of the most exposed populations: total average effective doses accumulated over 20 years between 33 and 50 mSv.
- According to the UNSCEAR Committee of the UN, 100 mSv is the threshold below which the dose is considered low, and below which cancer cases cannot be reliably attributed to irradiation.

Consequences recorded since the accident and to date
- ~5000 cases of non-lethal thyroid cancer identified (in non-evacuated adults who were children, or adolescents in 1986) in the 30 years following, attributable to radiation exposure of non-evacuated populations
- 4,000 deaths among the 600,000 most exposed people (0.67%)
- 5,000 deaths among the 6 million people nearby (0.08%)
- International Agency for Research on Cancer: The number of deaths attributable to accidental exposure between 1986 and 2065 would not exceed ~16,000 based on maximalist, non-threshold linear dose-effect models for low doses and collective dose.

Evacuation

Characteristics of the evacuation

Same day: decision to evacuate Prypiat (3 km from the plant), only implemented 36 hours after the accident.
Next day: evacuation zone extended to 10 km around the plant,
10 days later: evacuation zone extended to 30 km, now an “exclusion zone” of ~2,600 km²_.
Between 1986 and 2000, ~350,000 people permanently resettled from the most severely contaminated areas
For these people, average effective dose due to external irradiation was estimated at 17 mSv (between 0.1 and 380 mSv)
100 mSv is the threshold below which cancer cases cannot be reliably attributed to irradiation.

Long-term socio-economic impacts

Failure to anticipate the negative effects of post-accident management: in a context of mistrust of public action, inhabitants of contaminated territories developed a strong sense of resignation, loss of control, and powerlessness.
Evacuation and resettlement trauma: severing of social ties, inability to return home, stigma related to the status of “exposed person”.
Lasting distrust of official discourse due to the lack of reliable information after the accident, which also led to the erroneous attribution of many health problems to radiation from the accident.
Loss of economic stability and lasting deterioration of physical and emotional well-being due to mass displacement, in a climate of worry and confusion.
Excessive concern with regard to radiation and insufficient concern with reckless behavior, such as excessive consumption of alcohol and tobacco, or that of products from areas still contaminated with radioactive cesium, both extreme behaviors being accentuated by the confrontation with an objectively worrying radiological situation and a phenomenon of real contamination.
Aggravating factor of the disorganization and then break-up of the Soviet Union, adding to general anxiety.
Several tens to several hundreds of billions of euro spent by the USSR, then after 1991 by Russia, Ukraine, and Belarus (for example, in Belarus up to 22% of the state budget in the early years, and 1% still today) to support liquidators and evacuated populations.

Waste

~2 million m³ of plants, soil, building materials, miscellaneous equipment, etc. generated by the decontamination work and placed in the exclusion zone around the reactor.
~10-12 m³ of intermediate and high level waste mostly stored under adequate conditions; however, a few thousand cubic meters are awaiting treatment and stored in a dedicated facility.
Gradual migration of radionuclides in groundwater detected since 1990, for which several actions are underway.

Consequences of Russia’s invasion of Ukraine

International mobilization

IAEA, ASNR (ex-IRSN) and European Radiation Protection Authorities (including EURDEP) have been mobilized to monitor the situation and condition of Ukrainian nuclear facilities, including the Chernobyl site
April 26, 2022: IAEA mission to the Chernobyl site after the withdrawal of Russian troops.
Continuous and detailed monitoring of the radiological status thanks to the Ukrainian national radiological monitoring network, the Ukrainian state agency for management of the Chernobyl exclusion zone, the operator of Ukrainian nuclear power plants, as well as the EURDEP network for monitoring radiological data, managed by the European Commission.

Events

February 25, 2022: Intrusion into the Chernobyl exclusion zone. Takeover of the site occupied for 35 days by the Russian army.
- Ambient gamma dose equivalent rate peaks well above the levels (background noise) usually found in the Chernobyl exclusion zone.
- Most likely explanation according to ASNR is a technical malfunction of the beacons, reinforced by the IAEA and other international partners and observers.

March 9, 2022: Loss of external power supplies to all Chernobyl power plant facilities.
- Emergency generators on site:
  - No dewatering of the assemblies and therefore no radioactive release into the environment according to studies carried out after the accident at the Fukushima Daiichi power plant on the consequences of a total loss of cooling of the spent fuel pool (ISF1) which show a slow rise in water temperature up to around 60°C max.
  - Passive removal of the heat from spent fuel assemblies into the dry storage pool (ISF2).
  - In addition, the ventilation system of the arch and the safety system of the spent fuel storage pool are backed up.

From March 11 to 21, 2022: Forest fires in the Chernobyl exclusion zone resulting in an increase in measured radioactivity.
- Forest fires have occurred before. They generally result in very low increases in activity in the air.
- Regarding this specific fire in time of war, the beacon of the Ukrainian national radiological monitoring network, located in the city of Chernobyl, although supplied irregularly, did not detect any abnormal increase in radioactivity.
- No significant increase in dose equivalent rate over the period of March 11 to 18, 2022.
- Very slight increases in the levels of cesium-137 in the air detected in Kiev and at the Rivne and Khmelnytskyi nuclear power plants, not posing a health problem.

February 14, 2025: The containment arch of Reactor No.4 was damaged by a drone and lost its containment capability, but without permanent damage to load-bearing structures or monitoring systems. The dismantling operations of the “sarcophagus” were suspended pending the repair of the containment structures.

Institutional handling of the accident by the USSR – 1986

April 26, 1986 (day of the accident)
- Confinement order communicated to the inhabitants of Prypiat, 3 km from the plant, in the hours following the explosion of reactor No. 4
- Distribution of stable iodine tablets
April 27, 1986
- Evacuation of Prypiat (~36 hours after the accident)
- ~116,000 people evacuated in the first few days
April 29, 1986
- Soviet news agency TASS spoke of an “accident of medium severity at Chernobyl”
Early May 1986
- 1st restriction measures established in Ukraine for food contaminated with iodine-131 (iodine-131 contamination of milk and water > 3,700 Bq/kg, fish > 37,000 Bq/kg)
May 09, 1986
- Visit of the Director General of the IAEA to Moscow: the USSR committed to providing detailed information on the accident
- Control of the main plant fire
End of May 1986
- End of radioactive discharges from the reactor
From May to November 1986
- Construction of the concrete sarcophagus confining reactor No 4

Institutional handling of the accident in France – 1986

Government response and media coverage

From April 29th (1 day after detection by Sweden) to May 6, 1986, the French authorities, including the Ministry of Agriculture, and the Radiation Protection Authority (at the time SCPRI)
- Communicated, on the 1:00pm news broadcast on the TF1 television channel starting April 29th, and daily to AFP, the measurements of radioactivity, their composition, the movement of the cloud
- announced the arrival of the radioactive plume over France on April 30th
- estimated the health impacts due to the passage of the cloud
- indicated that it passed over France!
  - Radioactivity measurements on French territory were on the rise “without any impact on public health” (AFP, May 1, 1986 – republished by the French newspaper, Libération, the next day)
    “Neither the current situation nor its subsequent development justify any health countermeasures in our country, whatsoever.”  (May 2, 1986)
  - “The transient elevation of radioactivity in the atmosphere that occurred starting April 30th has now disappeared.”  (May 5, 1986)
  - National territory “totally spared”, “the observed increases in radioactivity did not pose the slightest problem to public health” (May 6, 1986)

International institutional handling of the accident

First 10 years

April 28, 1986 – international awareness, 2 days after the accident
1986 – 1st detailed information
- “Post-Accident Review Meeting on the Chernobyl accident”
  - August 1986, Vienna (4 months after the accident)
  - Soviet delegation led by Valeri Legasov, Deputy Director of the Kurchatov Institute (USSR)
  - presentation to 500 experts, from 45 countries
- INSAG-1 report of the International Nuclear Safety Advisory Group
  - September 1986 (5 months after the accident)
  - Combination of unprecedented violations of procedures and a failed reactor concept
  - Introduction of the concept of “safety culture”
1988
- 1st report on the effects of atomic radiation from the accident on liquidators and the nearby population
  - published by UNSCEAR (United Nations Scientific Committee)
- Policy for long-term post-accident management
  - established by the Soviet Ministry of Health
  - Radiological exposure limit: 5 mSv/year (350 mSv lifetime dose)
1990
- Abandonment of the limit of 5 mSv/year by the Soviets for 1 mSv/year recommended by the International Commission on Radiological Protection in normal and non-accidental situations
1991
- Collapse of the USSR.
  - The institutional response to the Chernobyl accident is now managed by three separate republics.
  - the effects of the collapse are added to the repercussions of the accident.
- International Program on the Health Effects of the Chernobyl Accident (IPHECA) under the aegis of the United Nations (report published in 1995)
1992
- Publication of INSAG-7, revision of the 1986 report
  - mitigated the liability of the operators in the accident
  - new elements on: the chronology of the accident, the design of the RBMK reactors, the malfunctions of the Soviet system
1992-94
- JSP-2 (Joint Study Project 2) to conduct field surveys of populations in Ukraine

1996 to the present (40 years later)

1996
- Definitive shutdown of reactor No. 1 of the Chernobyl power plant (10 years after the accident on reactor No. 4)
1997
- “Shelter Implementation Plan” (SIP), an international program of actions to sustainably cover the damaged reactor
1999 – 2000
- Definitive shutdown of reactors No. 2 and 3 of the Chernobyl power plant.
2000
- New detailed assessment by UNSCEAR of Chernobyl radiation levels and effects
2005-06
- “The Legacy of Chernobyl: health, environmental and socio-economic consequences”
- report published jointly by several UN agencies
- IAEA, WHO, UNDP, FAO, UNEP, OCHA and UNSCEAR
2008
- Stabilization of sarcophagus structures (SIP step 1).
2008
- Update of the UNSCEAR report “Health Effects Due to Chernobyl”
- no major development, but!
- continuous rise in cases of thyroid cancer in irradiated children and in psychological effects due to evacuation and rumors.
2017
- Completed construction of the New Safe Confinement (SIP step 2), “arch” covering the sarcophagus.
2017
- “Evaluation of data on thyroid cancer in regions affected by the Chernobyl accident”
- new publication by UNSCEAR
2021
- Comparison of key data from Fukushima and Chernobyl accidents in “Sources, effects and risks of ionizing radiation” report
- New publication by UNSCEAR

International support

The international community mobilized several billion euro to support the response to the Chernobyl accident, during two separate periods:

1986–1991

Majority of cost borne by the USSR: ~ $12-14 billion
Little direct international aid besides technical and humanitarian aid (WHO, IAEA)

Post-1991 (collapse of the USSR)

Financial support from European governments
- ~ €730 million managed by the EBRD
- dedicated to safety and industrial support programs (construction of a new containment for destroyed Reactor No. 4).

Overall support from the international community;
- ~ €2.15 billion

Establishment of the World Association of Nuclear Operators (WANO) by and for operators of nuclear facilities worldwide
- Objective: conduct inspection missions on operator sites to promote a higher level of safety through “peer pressure”.