- What are electromagnetic fields?
- Static and low-frequency fields
- What are static and low-frequency electric and magnetic fields?
- Direct and alternating voltage
- Effects of static and low-frequency fields
- Reports & Evaluations
- Radiation protection relating to the expansion of the national grid
- Basics transfer of electrical power
- High-frequency fields
- What are high-frequency fields?
- Applications high-frequency fields
- Radiation protection in mobile communication
- What is mobile communication?
- Reports and evaluations
- What is optical radiation?
- UV radiation
- What is UV radiation?
- Sun but safe!
- Effects of UV radiation
- Protection against UV radiation
- UV index
- Infrared radiation
- What is ionising radiation?
- Radioactivity in the environment
- Where does radioactivity occur in the environment?
- What is the level of natural radiation exposure in Germany?
- Air, soil and water
- Building materials
- Industrial residues (NORM)
- BfS laboratories
- Applications in medicine
- Radiation protection in medicine: international activities
- Applications in daily life and in technology
- Radioactive radiation sources in Germany
- Register high-level radioactive radiation sources
- Type approval procedure pursuant to RöV and StrlSchV
- Cabin luggage security checks
- Radioactive materials in watches
- Ionisation smoke detectors (ISM)
- What are the effects of radiation?
- Acute radiation damage
- Effects of selected radioactive materials
- Consequences of a radiation accident
- Cancer and leukaemia
- Genetic radiation effects
- Individual radiosensitivity
- Epidemiology of radiation-induced diseases
- Ionising radiation: positive effects?
- Risk estimation and assessment
- Radiation protection
- Basic informations
- Occupational radiation protection
- Nuclear accident management
- What happens in an emergency?
- Federal and state tasks
- In the event of an emergency
- Measuring networks
- Exercises for emergency situations
- Nuclear accidents
- Defence against nuclear hazards
- Service offers
- Radon measurements
- Incorporation monitoring
- Biological dosimetry
- Online library
- About us
- Science and research
- Research concept
- Scientific collaborations
- EU research framework programme
- BfS research programme
- Third-party funded research
- Departmental research
- Selected research projects
- Selected research results
- Professional opinions
- Laws and regulations
- BfS Topics in the Bundestag
The Chernobyl accident
- The accident occured in unit 4 of the Chernobyl nuclear power plant - a reactor type of Soviet design.
- The reactor was in the phase of slow shutdown. At the same time an experiment was planned for checking various safety features.
- Basic design failures of the plant in combination with failures and offences in operational management led to the reactor desaster.
The accident occurred on 26 April 1986 in unit 4 of the Chernobyl nuclear power plant – a reactor type of Soviet design termed RBMK. The fuel elements in this reactor type are located inside pressure tubes - surrounded by a graphite block - and cooled with water.
At the time of the accident, the reactor was in the phase of a slow shutdown according to schedule to carry out routine maintenance and test measures (revision). At the same time an experiment was planned for checking various safety features of the plant. Basic design failures of the plant in combination with failures and offences in operational management led to the reactor disaster.
The experiment was to prove that in case of a loss of coolant accident and a simultaneously assumed failure of power supply it would still be possible to control the plant. In case of such an incident the reactor would immediately be shut down automatically. The mechanical energy of the coasting-down rotor in the turbine-generator set must then be sufficient for an interim supply of the power required by the reactor coolant pumps until the supply of the emergency pumps through the emergency Diesel unit is ensured.
This experiment was seen as a purely conventional experiment in the field of electrical engineering and no interactions with the nuclear part of the plant were expected.
Course of the accident
Contrary to expectations the power increased rapidly and got out of control while the experiment in Chernobyl was carried out. This resulted in a rapid increase in energy release in the fuel elements and furthermore to the destruction of the reactor core. The heat stored in the fuel was transferred to the surrounding coolant very quickly. Thus the coolant was heated up and evaporated.
Due to the resulting high pressure the reactor exploded. The reactor building including its roof was destroyed and numerous fires broke out. The entire graphite block of the reactor core with a mass of 250 tons incinerated. This fire took the reactor’s radioactive inventory to great heights of the atmosphere and caused the long-range dispersion of radioactivity throughout Europe.
Reasons for the accident
Several reasons contributed to the reactor failure:
- Unfavourable reactor-physical properties and safety-related features of the reactor type,
- Shortcomings in the experiment programme,
- Unforeseen conditions while the experiment was carried out,
- Several offences against operating rules.
What radioactive substances were released?
A large number of radioactive substances were released into the atmosphere by the explosion and the reactor fire (cf. table). The half-lives – the time interval where half of the nuclei of a radioactive nuclide has decayed – of these radioisotopes vary a lot. They are between about three days for tellurium-132 and about 24,000 years for plutonium-239.
The released radionuclides had different effects on environment and health.
|Noble gases||Krypton and xenon isotopes|
(such as krypton-85, xenon-133)
|Readily volatile substances||Iodine, tellurium and caesium isotopes|
(such as iodine-131, tellurium-132, caesium-134, caesium-137)
|Not readily volatile substances||Ruthenium and strontium isotopes|
(such as ruthenium-103, ruthenium-106, strontium-89, strontium-90)
|Transuranic elements||Plutonium and curium isotopes|
(such as plutonium-238, plutonium-239, plutonium-240, curium-242)
State of 2018.04.13