Penetration performance of alpha, beta and gamma radiation

Radioactive substances can decay in different ways and, in the process, emit differing quantities of alpha, beta or gamma radiation, which have different biological effects.

Alpha radiation only damages tissue at a short distance, but it is very effective within its range of action. It is particularly harmful if the substances emitting alpha radiation are inhaled, remain in the lungs and decay there.

Radiation doses due to external radiation exposure are predominantly due to gamma radiation, which has a longer range but less “destructive potential” at the same time. Given its short range, alpha radiation does not contribute to radiation doses from external radiation exposure (e.g. due to contaminated soil).

During each half-life, the number of radioactive atoms in a radionuclide halves.

Radioactive substances have different half-lives. After the half-life has elapsed, half of the radionuclides have decayed and can therefore no longer contribute to radiation exposure. If radionuclides have a long half-life, they contaminate the environment for a long time – and therefore cause people to be exposed to radiation for a corresponding period.

This is why radioactive caesium-137, for example, with a half-life of 30 years, is still relevant long after an accident at a nuclear power plant. On the other hand, radioactive iodine-131, with a half-life of 8 days, has practically disappeared from the environment altogether after just a few weeks.

In the event of contaminated air masses (a "radioactive cloud") following a radiological emergency, the radiation dose for an individual is lower the less time they spend in these air masses and breathe the contaminated air.

A similar rule applies to time spent on contaminated ground: here, the radiation dose for a person is lower the less time they spend in the contaminated area and are exposed to radiation acting externally on the body.

If foodstuffs are contaminated following a radiological emergency, the radiation dose a person receives is lower the less contaminated foodstuffs they eat.

Children are generally more sensitive to radiation. Lower radiation doses therefore pose a greater risk to them than to adults.

The radioactive substances released in a serious accident at a nuclear power plant

• in Germany or
• in a neighbouring country

can be distributed across the entire territory of Germany by wind and weather to varying extents. They can be absorbed by people via inhalation and/or food. In addition, the radiation emitted by the radioactive substances may result in external radiation exposure.

The radiological consequences for people depend strongly on which radioactive substances were released, how far the accident site is from the people, and how long the people spend in the affected area. It is also relevant whether and to what extent people inhale, eat or drink radioactive substances:

• In very unlikely cases, the population in the immediate vicinity of the nuclear power plant (up to a distance of 3–5 kilometres) can be affected by acute (deterministic) radiation damage if they are exposed to the radiation without protection.
• Long-term (stochastic) damage such as cancer, for example, is also possible in Germany.
• Psychosocial consequences are highly likely: the fear of radioactive material and the lack of knowledge regarding not only the dispersion and effects of radioactivity but also the means of protection can lead to feelings of uncertainty and contribute to psychological stress.

Example: Radiological consequences of the 2011 accident in Fukushima, Japan, for the local population

Fukushima Daiichi nuclear power plant Source: Taro Hama @ e-kamakura/Moment/Getty Images

Following the accident at the nuclear power plant in Fukushima, Japan, in 2011, work was carried out in Japan in order to estimate the effective dose that people in unevacuated municipalities or parts of municipalities in Fukushima Prefecture had received due to radioactive substances released in the accident. In such areas, which had the highest contamination outside of the evacuated areas, an effective dose of some 3 to 5.3 millisieverts was determined for the resident population. This value is around 100 times lower than the threshold for acute (deterministic) radiation damage and corresponds to about 1.5–2.5 times the amount of natural radiation to which people in Germany are exposed each year.

• Acute radiation damage (deterministic effects) did not occur either in the Japanese population or in the emergency service personnel working in the immediate vicinity of the reactor that suffered the accident – partly thanks to adherence to the relevant safety guidelines for the emergency service personnel.
• According to current dose and risk estimations, long-term (stochastic) effects, such as a discernible increase in radiation-related thyroid cancers, are highly unlikely to occur in any of the considered age groups in the future. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) assumes that an increase in thyroid cancers observed in children and adolescents as part of a new screening programme in Japan (the Fukushima Health Management Survey) is not connected to radiation exposure and is instead a consequence of the particularly sensitive diagnostic procedure.
• There was no credible evidence of an excess incidence of birth defects, stillbirths, premature births or low birth weights in connection with radiation exposure. Nor are such effects to be expected given the radiation doses that occurred.
• However, there was and continues to be a higher incidence of non-radiological pathologies due to anxiety or stress in the affected Japanese population. Such pathologies clearly predominate in comparison with diseases caused by radiation. For example, psychosocial consequences included suicide, depression, alcoholism, gambling, domestic violence, obesity (especially in children) and relationship breakdown.

The radioactive substances released in a serious accident at a nuclear power plant

• in another European country far from Germany's borders or
• outside Europe

may be transported to Germany by wind and weather to a small extent. Once there, they could be absorbed into the body via inhalation and/or food. In addition, the radiation emitted by the radioactive substances may result in external radiation exposure.

The further Germany is from an accident at a nuclear power plant, the more the quantity of radioactive particles decreases over the long transport route. This means that the quantity may ultimately be so low in Germany that it can only be measured using highly sensitive equipment for trace analysis. In this regard, the half-life of the released radioactive substances is a particularly important factor: for example, it is practically impossible for radioactive iodine released in Japan to be transported all the way to Germany by wind and weather, because most of it would have decayed on the way due to the short half-lives of iodine isotopes. Similar applies to noble gases such as radioactive krypton or xenon that are released far away.

For people in Germany, accidents at a nuclear power plant in more distant regions of Europe or outside Europe are therefore far less momentous from a radiological perspective than accidents at nuclear power plants in Germany or in a neighbouring country:

• In particular, accidents outside Europe are likely to have virtually no radiological consequences – either acute (deterministic) or long-term stochastic damage – for people in Germany, given the large distance from the accident site.
• People can, however, experience psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding the dispersion and effects of radioactivity can lead to feelings of uncertainty and contribute to psychological stress.

Example 1: Radiological consequences of the 1986 accident in Chornobyl, Ukraine, for the local population

A sign in the exclusion zone warning people about the “Red Forest”, an area that received the highest levels of contamination following the accident in Chernobyl.

One example of a serious accident at a nuclear power plant in a distant region of Europe is the accident in Chornobyl in 1986. Germany was also affected by the radioactive cloud produced by the accident. Due to the large distance from the accident site in Ukraine, the radiation doses in Germany were very low. For adults, for example, they were less than 1 millisievert (0.56 millisieverts for external radiation exposure and 0.25 millisieverts for internal radiation exposure due to absorption via food) in the worst-affected area of Germany, Berchtesgadener Land, in the first year after the accident.

In highly contaminated areas of southern Bavaria such as this, where certain species of mushroom and game have been contaminated with radioactive caesium since the accident in Chernobyl, the total effective dose expected over a period of 50 years from 1986 to 2036 as a result of the accident is about the same as the radiation exposure that we constantly experience due to natural radioactive substances over the course of a year, according to an estimate by the German Commission on Radiological Protection.

No scientifically sound evidence has been obtained of radiation-related health effects in Germany since 1986. Health consequences are also unlikely to be identified in the future.

Example 2: Radiological consequences of the 2011 accident in Fukushima, Japan, for the German population

Trace analysis air-borne particle collector on the roof of the BfS office in Freiburg

One example of a serious accident outside Europe is the accident in Fukushima, Japan, in 2011. In Germany, the slightest traces of radioactivity could be detected using highly sensitive instruments for trace analysis. These trace levels of radiation did not lead to any radiation exposure for the population living in Germany.

At no point was there a risk to human health in Germany.

Nuclear facilities such as intermediate storage facilities for nuclear waste or research reactors, for example, contain smaller quantities of radioactive material than a nuclear power plant. If an accident occurs at such facilities, the radioactive substances released can be distributed by wind and weather to varying extents. People can absorb these substances via inhalation and/or food. In addition, the radiation from radioactive substances can also act on people externally.

The radiological consequences for people depend strongly on which radioactive substances were released, how far the accident site is from the people, and how long the people spend in the affected area. Another factor is whether and to what extent people inhale radioactive substances or absorb them with food. Given the smaller quantities of radioactive substances that can be released, the health effects of an accident at a nuclear facility are much smaller than in the case of an accident at a nuclear power plant in Germany or in a neighbouring country:

• For people in Germany, no acute (deterministic) radiation damage is to be expected following accidents even at nuclear facilities in Germany or close to the border.
• Long-term (stochastic) damage is conceivable to a lesser extent than is the case for an accident at a nuclear power plant in Germany or in a neighbouring country. This depends on how people come into contact with radioactive substances – and in what quantity.
• There is a possibility of psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding not only the dispersion and effects of radioactivity but also the means of protection can lead to feelings of uncertainty and contribute to psychological stress.

Example: Radiological consequences of the 1993 accident in Seversk (Tomsk), Russia, for the local population

One example of an accident at a nuclear facility that is not a nuclear power plant is the accident that took place at a reprocessing plant for uranium and plutonium in Seversk (Tomsk), Russia, in April 1993. As part of the accident, an explosion resulted in the release of radioactive substances into the environment. According to the International Atomic Energy Agency (IAEA), these substances included above all ruthenium, niobium and zirconium, as well as small quantities of plutonium. The dispersion of radioactive materials into the environment extended beyond the plant site to a distance of some 20 kilometres to the north-east. No measurable contamination was detected in neighbouring areas.

There was no need for early measures to protect the local population. The area affected by contamination quickly decreased over time due to the half-lives of the radionuclides that were present, and fell to a negligible level by the start of 1994.
The accident resulted in radiation exposure of the staff of the reprocessing plant and of the firefighters deployed following the accident, but did not lead to any acute (deterministic) health effects. In a small area in the immediate vicinity of the facility where the accident took place, the additional radiation dose for the local population was less than 0.4 millisieverts per year.

In terrorist or other attacks involving a "dirty bomb", for example, the extent to which released radioactive substances can spread and affect human health depends above all on the quantity of explosive used – and therefore the explosive effect – as well as on the type and quantity of radioactive material included. Usually, such attacks result in a relatively small-scale, localised dispersion of the released radioactive substances. These substances can then be absorbed by people via inhalation and/or food. In addition, the radiation from radioactive substances can also act on people externally.

In the case of a "dirty bomb", there is no immediate mortal danger due to the radioactive material, but the power of the detonation does pose such a danger to people in the immediate vicinity. Whether and to what extent acute (deterministic) radiation damage and/or possible long-term (stochastic) damage can occur depends strongly on the type of radiation emitted by the radioactive substances used. For example, inhaled alpha emitters generally have a greater effect than inhaled beta or gamma emitters.

The radiological dangers of a "dirty bomb" are commonly overestimated. It is above all the psychosocial consequences that are of significance to the population: the fear of radioactive material and the lack of knowledge regarding not only the dispersion and effects of radioactivity but also the means of protection can lead to feelings of uncertainty and contribute to psychological stress.

Thankfully, an attack involving a "dirty bomb" has never taken place. In terrorist or other attacks, radioactive substances can also be used directly to harm individuals or groups of people, e.g. by poisoning food.

Example: Attack with radioactive polonium on Alexander Litvinenko in 2006

In November 2006, Russian exile Alexander Litvinenko was fatally poisoned in London with radioactive polonium-210.

Polonium-210 emits alpha radiation, but this radiation is only effective over a range of a few centimetres and can even be shielded by a sheet of paper. The isotope becomes dangerous to humans if it enters the body. Absorption of as little as 0.1 micrograms leads to death within a few days due to radiation exposure.

If radioactive substances with higher activities (e.g. spent fuel elements from nuclear power plants) are to be transported, the transport containers must be designed so that they remain leak-tight even in the event of the most severe accidents.

If an accident occurs during the rail or road transport of radioactive substances, such as radioactive hospital waste or fuel rods for nuclear power plants ("castor transports"), the radiological impact is generally very small and depends on which radioactive substances are being transported and are released in an accident. If the transport container is damaged, radioactivity can escape in a relatively small area around the accident site and enter the body via inhalation or, where applicable, via contaminated wounds. External radiation exposure of the human body can also take place.

At a sufficient distance from the damaged transport containers and vehicles, there is no risk to the population. People can, however, experience psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding the dispersion and effects of radioactivity can lead to feelings of uncertainty and contribute to psychological stress.

In reality, (traffic) accidents also occasionally occur during the transport of radioactive material in Germany. However, these accidents usually have little or no radiological impact and are generally localised.

If orphan (unregistered) radioactive sources are found, or if accidents occur during the handling of radioactive material or such material is accidentally melted down, radiological consequences due to the released radioactive substances are usually only to be expected in a small area.

• If a radioactive source is encased in shielding, it is not possible for radioactive material to escape from it, to contaminate the environment, or to be inhaled or absorbed with food by humans. However, direct radiation can emanate from the enclosed radioactive source in the form of gamma and neutron radiation and can pose a risk to people within a radius of up to several metres of the object.
• If a radioactive source is open – in other words, if its shielding has been unintentionally or deliberately damaged or opened – there is also a risk of contamination of the immediate environment in addition to the hazard due to direct radiation. Moreover, it is possible for the open radioactive substances to be absorbed into the human body via inhalation or food or, where applicable, via contaminated wounds. The hazard potential is highly dependent on the released radioactive substances and the type of radiation they emit. If the opened and contaminated radioactive source is passed on, it can contaminate and endanger a greater number of places and people.

At a sufficient distance from orphan radioactive sources and open radioactive material, there is generally no risk to the population. People can, however, experience psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding the dispersion and effects of radioactivity can lead to feelings of uncertainty and contribute to psychological stress.

Example: Radiological consequences of open orphan radioactive substances in Goiânia, Brazil, in 1987

One example of the radiological consequences of an orphan source and open radioactive material is an incident that took place in the city of Goiânia, Brazil, in September 1987.

During a break-in at a disused hospital, thieves stole a medical instrument used for radiotherapy. The lead shielding container was subsequently opened, and the material it contained was distributed to family and friends by a scrap dealer because of the beautiful glow it emitted in the dark – but, unbeknown to those involved, the substance contained radioactive caesium-137.

Hundreds of people were contaminated, some of them seriously, due to contact with the radioactive material. The accident led to four confirmed deaths within a few weeks and is also linked to further fatalities. Parts of the city of Goiânia are still radioactively contaminated to this day.

If one of the approximately 50 satellites that use nuclear or radiologically relevant material as an energy supply crashes over land, it is unlikely that a large number of people will be exposed to increased levels of radiation. This also applies if, when satellites with nuclear batteries fall to earth, the radioactive substances used in the batteries are dispersed over a large area as the satellites burn up on entering the atmosphere. These satellites are continually monitored by ground stations so that, in the event of a crash, the predicted area of impact can be delimited fairly accurately and the local population can be warned of the crash in good time.

Fragments of a crashed satellite with a small nuclear reactor or a nuclear battery on board can emit radiation, leading to radiation exposure for people who are in the vicinity immediately following the crash. The same applies in the case of direct physical contact with fragments of the crashed satellite. However, it is almost impossible for radioactive substances released due to the crash to be absorbed into the human body via inhalation, because most of the particles are not respirable due to their size.

Crashes of satellites with a small nuclear reactor or a nuclear battery on board generally do not pose a radiological risk to the general public: the radiological health effects are very minor.

Likewise, there is only a very small chance of a non-radiological hazard due to falling debris if the satellite does not burn up completely on entering the atmosphere: since the Space Age began in 1957, there have been no confirmed reports anywhere in the world of personal injuries in connection with the reentry of a space object into the earth’s atmosphere.

People can, however, experience psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding the dispersion and effects of radioactivity can lead to feelings of uncertainty and contribute to psychological stress.

Example: crash of a reactor-powered satellite over Canada in 1978

Satellite (illustration) Source: Sasa Kadrijevic/stock.adobe.com

One example of the radiological consequences of a satellite crash is the impact of a Russian reactor-powered satellite (Kosmos 954) over Canada in 1978. The crash scattered small radioactive particles over an area measuring some 100,000 square kilometres. These particles did not pose a risk to the health of the general public, because they were tiny, sparsely distributed over a very large area and chemically insoluble, such that, even if they were absorbed into the body with food, for example, they were quickly excreted again.

In the impact path – which was several kilometres wide and several hundred kilometres long – around 100 larger fragments of the satellite with a higher level of contamination were found and recovered by experts. The local dose rate (gamma radiation) measured at a distance of 1 metre from these debris fragments was up to several millisieverts per hour. The maximum dose received by the recovery personnel (who were closely monitored using dosimetry) was 4.7 millisieverts and therefore approximately twice the dose that a person receives in a year due to natural radiation in Germany.

If reports or rumours point to a release of radioactive materials – for example due to an accident at a nuclear facility – without the possibility of confirming the information, the radiological consequences for humans are also difficult to predict.

In general, an "unclear situation" becomes clearer over time and can then be assigned to one of the other emergency scenarios.

There is a possibility of psychosocial consequences: the fear of radioactive material and the lack of knowledge regarding not only the dispersion and effects of radioactivity but also the means of protection can lead to feelings of uncertainty and contribute to psychological stress.

Example: Unclear situation due to measurement of ruthenium-106 in 2017

Measuring points at which ruthenium-106 was detected in the air between the end of September and the beginning of October 2017

One example of an unclear situation took place in early October 2017, when ruthenium-106 was detected at numerous measuring stations in Europe. The location of the isotope's release was unknown.

At no point was there a radiological hazard for people in Germany, because the measured values were too low to cause health effects. The concentration in Germany was within a very low range – between a few microbecquerels and a few millibecquerels per cubic metre. Not only acute (deterministic) damage but also long-term (stochastic) damage is ruled out as a consequence of

In the event of a nuclear blast, a huge amount of energy is released in the form of an explosive effect. This consists of a flash of light and a subsequent wave of pressure and heat of such power that it has fatal consequences, as well as a nuclear electromagnetic pulse that can disrupt or destroy electronic devices.

People can also suffer radiological consequences due to radioactive substances – specifically, due to high-energy ionising radiation:

• In the event of a nuclear blast, initial radiation spreads out in all directions at the speed of light. This radiation dies out within a few seconds and is generally fatal for people who are present within a radius of a few kilometres of the explosion site without protection.
• The blast also leads to the formation of radioactive substances that produce residual radiation and are dispersed over different distances depending on the design of the nuclear weapon, the altitude of the explosion, and the weather conditions. These substances are gradually deposited on the ground (fallout). The resulting radiation dose (or, more precisely, the dose rate) for people is higher immediately after the blast than following an accident at a nuclear power plant, but it then decreases much faster in all locations: given the high level of short-lived radionuclides, only some 1% of the radioactive substances originally released are still present in the environment 48 hours after a nuclear blast. This includes some longer-lived radionuclides that can contribute to longer-term contamination of the environment and corresponding exposure of humans.

For people in Germany, nuclear blasts in more distant regions of Europe or outside Europe are much less serious from a purely radiological perspective than nuclear blasts in Germany or in a neighbouring country:

• In the event of a nuclear blast in Germany or in a neighbouring country, the radiological consequences for people would depend strongly on which radioactive substances were released, how far away the explosion site was, how long they spent in the affected area, and whether and to what extent they absorbed radioactive substances into their bodies via inhalation or food: in extreme cases, acute (deterministic) radiation damage could affect the population up to a distance of approximately 140 kilometres from the explosion site, depending on the power of the nuclear weapon and on weather conditions, in the event that the population was exposed to the radiation without protection. Long-term "stochastic damage", such as cases of cancer, cannot be ruled out in Germany in the event of a nuclear blast in Germany or in a neighbouring country, even at a greater distance from the explosion site.
• Nuclear blasts in more distant regions of Europe and outside Europe would have almost no radiological consequences for people in Germany due to the large distance from the explosion site: a very large proportion of the radioactive substances would already have decayed in the atmosphere during transport, such that only a very small proportion of the radioactive substances would reach Germany. Accordingly, neither acute (deterministic) nor long-term stochastic damage would be expected.
• Psychosocial effects could occur in all cases: the fear of radioactive material and the lack of knowledge regarding the dispersion and effects of radioactivity can lead to feelings of uncertainty and contribute to psychological stress.

Example: Hiroshima 1945

Peace memorial in Hiroshima: monument for the first military use of the atomic bomb

On 6 August 1945, 80% of Hiroshima, Japan, was destroyed when an atomic bomb was dropped on the city. Some 20 minutes after the blast, radioactive fallout fell on the surrounding area.

Up to 80,000 of the city’s approximately 345,000 inhabitants were killed immediately by the blast. As all important records and registers in the cities were destroyed, the precise number of people killed by the explosion remains unclear to this day. It was not possible to clearly differentiate the causes of death according to burns, injuries or radiation, for the pressure and thermal waves also played a significant role.

It is estimated that 90,000–166,000 people died in Hiroshima due to the direct consequences of the blast and in the four months afterwards as a result of burns, injuries and acute radiation damage. Years or decades later, long-term damage appeared in survivors in the form of, among other things, leukaemia and tumours in various organs (stochastic radiation effects). In a group of 120,000 survivors of the atomic bombs dropped on Hiroshima and Nagasaki who are still being followed as part of a scientific study, disease development is attributed to radiation exposure in

• approximately 10% of people suffering from a malignant tumour
• almost 50% of people suffering from leukaemia.

Almost 80 years after the bombs were dropped, survivors still have a greater risk of developing cancer.

Recommendations for protection in the event of a nuclear blast

The International Commission on Radiological Protection (ICRP) publishes recommendations on what to do in the event of a nuclear weapons explosion in various languages:

Advice for the Public on Protection in Case of a Nuclear Detonation

Hinweise für die Öffentlichkeit zum Schutz im Falle einer nuklearen Explosion