Brief description of radiation accidents. Damaging factors during a nuclear power plant accident and their impact on the human body Radiation protection - a system of measures that make exposure to radiation safe

Radiation accident- this is an accident at a radiation hazardous facility (RHO), in which there was a release of radioactive products or ionizing radiation beyond the limits of their safe operation provided for by the design, causing irradiation of the population and environmental pollution. A radiation accident can occur for several reasons: design errors, equipment wear, operator errors, and operational violations.

As a result of accidents at radioactive waste facilities, radioactive substances (RS) are released into the atmosphere, spreading under the influence of wind over significant distances. Falling out of the clouds, RVs form a zone radioactive contamination. At certain concentrations of pollution in an area, living there becomes life-threatening.

One of the features of radioactive contamination is that it cannot be detected without the help of special dosimetric instruments, since Radiation has no color, no smell, no taste.

Radioactive radiation are capable of penetrating through various thicknesses of material and causing disruption of all vital processes in the human body (mainly hematopoiesis, the functioning of the gastrointestinal tract, gonads and thyroid gland). At the time of exposure to radiation, a person does not receive bodily harm and does not experience pain, but as a result of exposure to radiation, the affected person may later develop radiation sickness.

The main damaging factors of a radiation accident:

· exposure to external radiation (gamma, beta and x-ray radiation);

· internal radiation from radionuclides entering the human body (alpha and beta radiation);

· mechanical and thermal injuries, chemical burns, intoxication.

After an accident, the greatest danger is from external radiation, which enters the body through the skin and respiratory organs. In 2-3 months. After an accident, internal radiation poses a danger, which enters the body through the gastrointestinal tract with food and water. Internal radiation is the most dangerous for humans, since it is impossible to protect internal organs.

Ionizing radiation

Ionizing radiation(II) is radiation that has the ability to tear electrons out of the orbits of atoms and molecules, turning them into positively charged ions and releasing electrons, i.e. ionize (excite) them.

α -Radiation is a stream of particles that are the nuclei of a helium atom. This radiation propagates straight through media at a speed of 20,000 km/s. Alpha particles have a large mass, quickly lose their energy and therefore have a small range: in air - up to 11 cm, in biological tissues - 30-130 microns, in aluminum - 16-67 microns. Although alpha particles have the least penetrating power, they have the greatest lethality.

β- Radiation is a stream of electrons that have greater penetrating power and less damaging power than alpha radiation. They arise in the nuclei of atoms during radioactive decay and are immediately emitted from there at a speed close to the speed of light. The penetrating power of beta radiation in air is several meters, in biological tissues - several centimeters, in aluminum - several millimeters.

X-ray radiation- electromagnetic radiation of high frequency and short wavelength, occurs when substances are bombarded with a stream of electrons. Has great penetrating power.

γ -Radiation is a stream of quantum energy propagating at the speed of light. They have greater penetrating power and less damaging power than x-rays.

Radiation accident- an event that could lead or led to unplanned exposure of people or to radioactive contamination of the environment exceeding the values ​​​​regulated by regulatory documents for controlled conditions, which occurred as a result of loss of control of a source of ionizing radiation, caused by equipment malfunction, incorrect actions of personnel, natural disasters or other reasons.

When locating a radiation hazardous facility, safety factors must be taken into account. The distance from the nuclear power plant to cities with a population of 500 thousand-1 million people is 30 km; 1-2 million 50 km; with a population of more than 2 million 100 km. The wind rose, seismicity of the zone, its geological, hydrological, and landscape features are also taken into account.

On the scale of radioactive substances spread and radiation consequences Radiation accidents are divided into three types:

· local accident- is an accident, the radiation consequences of which are limited to one building or structure and in which there is a possibility of exposure of personnel and contamination of the building or structure above the levels provided for normal operation;

· local accident- this is an accident, the radiation consequences of which are limited to the buildings and territory of the nuclear power plant and in which exposure of personnel and contamination of buildings and structures located on the territory of the nuclear power plant are possible above the levels established for normal operation;

· general average is an accident, the radiation consequences of which spread beyond the border of the nuclear power plant territory and leads to irradiation of the population and environmental pollution above established levels.

The source of the accident- the area of ​​scattering of structural materials of emergency facilities and the action of α-, β- and γ-radiation.

Radioactive contamination zone- the area where radioactive substances fell out.

In the first hours and days after the accident, the effect on people is determined by external exposure from the radioactive cloud (fission products of nuclear fuel mixed with air), radioactive fallout on the ground (fission products falling from the cloud), internal exposure from inhalation of radioactive substances from the cloud, as well as due to contamination of the surface of the human body with these substances.

In the future, over many years, the accumulation of radiation dose will occur due to the consumption of contaminated food and water.

With a one-time release of radioactive substances from an emergency reactor and a steady wind, the movement of the radioactive cloud occurs in one direction. The resulting radiation situation is not as complex as in the case of multiple or prolonged release of radioactive substances and sharply changing weather conditions. A trace of a radioactive cloud formed as a result of radioactive substances falling out of the cloud onto the earth's surface during disposable emission, has ellipse view; at multiple - mosaic pollution.

When a radiation accident occurs at a nuclear power plant with the release of radionuclides, it occurs in three phases.

Early phase The course of the accident continues from the moment the accident begins until the release of nuclear fission products into the atmosphere ceases and the end of the formation of a radioactive trace on the ground. The radiation dose to people in this phase is formed due to the g- and b-radiation of radioactive substances contained in the radioactive air, as well as due to the inhalation of radioactive substances contained in the cloud into the body.

Middle phase flow - lasts from the moment the formation of a radioactive trace is completed until all measures are taken to protect the population. The duration of this phase can be from several days to a year after the accident occurs. In the middle phase, the source of irradiation is radioactive substances that have fallen from the cloud and are located on the soil, buildings, etc. They enter the body mainly with contaminated food and water.

Late phase The course of the accident lasts until the implementation of protective measures is stopped and all restrictions on the life of the population are lifted. In this phase, the usual sanitary and dosimetric monitoring of the radiation situation is carried out, and the sources of external and internal radiation are the same as in the middle phase.

Radioactivity- spontaneous transformation of atomic nuclei with the emission of ionizing radiation.

To measure the activity of a radioactive substance, the International System of Units (SI) uses the unit becquerel (Bq); 1 Bq = 1 decay/s.

Extrasystemic unit of activity - curie (Ci); 1 Ci = 3.7-10 10 Bq.

Half-life (Ti /2). - the time during which half of the atoms of a radioactive substance decay.

The main terms that characterize radioactivity are penetrating radiation, ionizing radiation and irradiation.

Penetrating radiation- a stream of γ-rays and neutrons released from the zone of a nuclear explosion and spreading in the air in all directions for many hundreds of meters and causing ionization of atoms of the medium through which they penetrate (gas, liquid, solid, biological tissue).

Ionizing radiation- radiation that forms positive and negative ions when interacting with the environment. The main parameters of ionizing radiation are radiation dose and radiation dose rate.

There are:

a-radiation - ionizing radiation consisting of positively charged α particles (nuclei helium), emitted during nuclear transformations;

β-radiation- a stream of β-particles (negatively charged electrons or positively charged positrons) with a continuous energy spectrum;

γ radiation- electromagnetic (photon) ionizing radiation emitted during nuclear transformations or annihilation of particles.

Neutron radiation- a flow of uncharged particles (neutrons) with high penetrating ability.

When biological tissue is exposed to ionizing radiation, molecules are destroyed with the formation of chemically active free radicals, which are the trigger for damage to intracellular structures and the cells themselves. Damage to a cell leads either to its death or to disruption of its functions while maintaining the ability to reproduce.

Damaged body cells that have retained the ability to reproduce can, in the long term, lead to the development of various diseases, including those of a tumor nature, and damaged germ cells can lead to genetic diseases in the descendants of irradiated individuals. When assessing the long-term consequences of radiation, it is necessary to keep in mind that not only ionizing radiation can lead to such effects. There are a number of unfavorable factors (smoking, alcohol, chemical exposure, solar radiation, etc.) that also lead to spontaneously occurring tumor and hereditary diseases.

Absorbed dose (D)- dosimetric quantity measured by the amount of energy absorbed per unit mass of the irradiated substance (biological tissue).

The SI unit of absorbed dose is the gray (Gy); 1 Gy = 1 J/kg of substance.

Non-systemic unit - rad; 1 rad = 1 10 -2 Gy.

But the absorbed dose does not take into account the fact that, at the same value, the biological effect from a-radiation will be significantly greater than from g- and b-radiation. The damaging effect of a-particles is higher than that of other types of ionizing radiation.

Equivalent dose (N)- absorbed dose, averaged over an organ or tissue, weighted by quality in terms of the characteristics of the biological effect of this radiation. The weighting factor used for this purpose is called the radiation weighting factor (formerly the quality factor). The equivalent dose of a specific tissue is calculated as the sum of the products of absorbed doses (averaged over a given tissue from each type of radiation) by the corresponding radiation weighting factor.

The SI unit of equivalent dose is the sievert (Sv); 1 Sv = 1 J/kg.

Off-system unit of equivalent dose - 1 rem = 0.01 Sv (1 Sv = 100 rem).

Effective dose (E)- equivalent dose, weighted by the relative contribution of a given organ or tissue to the total damage from stochastic (oncological and hereditary diseases) effects during total body irradiation. The weight multiplier used for this purpose is called tissue weight multiplier. The effective dose is the sum of the product of equivalent doses in various organs and tissues by the corresponding tissue weighting factor for these organs and tissues.

The unit of effective dose is sievert (Sv).

The effective dose is used only to assess the likelihood of stochastic effects occurring and only when the absorbed dose is significantly below the threshold dose to cause clinically apparent injury.

General exposure- relatively uniform irradiation (external or internal) of the entire body. Exposure lasting no more than 3 days is called acute or short-term; more than 2 days - prolonged or chronic; in cases where the full dose is dispensed with breaks between individual fractions - fractionated or fractionated irradiation.

Radiation effects:

· deterministic(previously called non-stochastic) - biological effects of radiation for which there is a dose threshold, above which the severity of this effect increases with increasing dose;

· stochastic- biological effects of radiation, for which it is assumed that there is no dose threshold for their occurrence. It is accepted that the probability of occurrence of these effects is proportional to the magnitude of the acting dose, and the severity of their manifestation does not depend on the dose. When a person is irradiated, stochastic effects include malignant tumors and hereditary diseases;

· somatic- deterministic and stochastic biological effects of radiation occurring in the exposed individual;

· hereditary- stochastic effects manifested in the offspring of an irradiated individual.

Features of the biological effect of ionizing radiation:

· absence of subjective sensations at the moment of contact with radiation

· presence of a hidden validity period

· discrepancy between the severity of ARS and the insignificant number of primarily affected cells

· summation of small doses

· genetic effect (effect on offspring)

· different radiosensitivity of organs

· high efficiency of absorbed energy

The severity of radiation depends on the time of receiving the total dose

· influence of metabolic factors on the development of radiation damage (with a decrease in metabolic processes before or during irradiation, its biological effect decreases).

Radiation sickness- a general disease of the body that develops as a result of exposure to ionizing radiation. There are acute radiation sickness (ARS) and chronic radiation sickness (CRS) of varying severity.

Acute radiation sickness(ARS) develops after short-term (minutes, hours, up to 2-3 days) external relatively uniform irradiation at doses exceeding the threshold value (more than 1 Gy); is expressed in a combination of damage to organs and tissues (specific syndromes). The modern classification of ARS is based on the dose dependence of damage to individual critical organs, firmly established in experiment and clinically, the violation of the functional state of which determines the form of ARS. With external relatively uniform irradiation, the following are distinguished:

· Bone-brain shape develops with irradiation at a dose of 1-10 Gy; Depending on the dose, it is divided into:

Mild ARS (1-2 Gy),

Medium (2-4 Gy),

Severe (4-6 Gy),

Extremely severe (6-10 Gy).

The clinical picture of this form of ARS is determined by hemorrhagic syndrome and the syndrome of infectious-necrotic complications. The frequency of deaths in the dose range of 2-10 Gy increases from 5 to 100%; they usually occur within 5 to 8 weeks.

· Intestinal form ARS occurs after exposure to a dose of 10-20 Gy. The clinical picture is dominated by signs of enteritis and toxemia; death - on 8-10 days.

· Toxic (vascular-toxic) form ARS occurs after irradiation at a dose of 20-80 Gy. The clinical picture is characterized by increasing manifestations of asthenohypodynamic syndrome and acute cardiovascular failure; death - on 4-7 days.

· Cerebral form ARS occurs after exposure to radiation doses greater than 90 Gy. Immediately after irradiation, single or repeated vomiting, loose stools, temporary (20-30 minutes) loss of consciousness, prostration, and later psychomotor agitation, disorientation, ataxia, convulsions, hypertension, respiratory distress, collapse, stupor, coma appear; death occurs on days 1-3 of injury.

Chronic radiation sickness(CLB) from external radiation occurs with prolonged exposure to doses of more than 1 Gy per year. During the course, 4 vaguely demarcated periods are distinguished: initial functional disorders, the disease itself, recovery and consequences.

Radiation reaction- reversible changes in tissues, organs or the whole organism and their functions caused by uniform general irradiation in doses of 0.5-1 Gy.

In case of a radiation accident, the following ways of human exposure are distinguished: external exposure from a radioactive cloud; external exposure from radioactive fallout on the soil; internal exposure from radionuclides entering the human body (incorporation of radionuclides). The distribution of incorporated radionuclides in the human body depends on their chemical properties and routes of entry into the body: through the respiratory system (inhalation intake), through the digestive tract (oral intake), through intact and damaged skin (percutaneous intake).

Structure of radiation emergency injuries are presented:

· acute radiation sickness from combined external and internal irradiation;

· acute radiation sickness from extremely uneven exposure to y-radiation;

· local radiation injuries;

· radiation reactions

· radiation sickness from internal exposure;

· chronic radiation sickness from combined exposure;

Dose ionizing radiation, not leading to acute radiation injuries, to decreased ability to work:

single dose (one-time) – 50 rad (0.5 Gy)

· multiple: monthly - 100 rad (1 Gy), annual 300 rad (3 Gy).

IN conclusions, which are formulated by the RSChS forces as a result of radiation situation assessments, for MK service d.b. stated:

· number of people affected by ionizing radiation; required health care forces and equipment;

· the most appropriate actions of NPP personnel, liquidators, personnel of MK service units;

· additional measures to protect various groups of people.

Damaging factors of radiation accidents.

Parameter name	Meaning
Article topic:	Damaging factors of radiation accidents.
Rubric (thematic category)	Warfare

Medical and sanitary support during the liquidation of the consequences of radiation accidents.

2.1. Characteristics of radiation accidents.

Radiation accident- release of radioactive substances beyond the boundaries of a radiation-hazardous object, which can create an increased radiation hazard to human life and health.

The source of the accident -source of dispersion of structural materials of emergency facilities and the effects of alpha, beta and gamma radiation.

Radioactive contamination zone – the area where radioactive substances (fallout) fell out.

In case of accidents at radiation-hazardous facilities, destruction of structures, technological lines, fire, release of radioactive substances into the environment, exposure of people to a mixed gamma-neutron flux and the entry of radioactive substances into the respiratory and digestive tract, contact with the skin and mucous membranes may occur.

Radioactive contamination of the external environment occurs, seriously disrupting the ecological situation. Taking into account the dependence of the boundaries of the spread of radioactive substances and radiation consequences, the following are distinguished:

· local accidents(radiation consequences are limited to one building, structure with possible exposure of personnel),

· local accidents(radiation consequences are limited to the territory of the nuclear power plant);

· general accidents(radiation consequences extend beyond the border of the NPP territory).

Phases of an accident at a radiation-hazardous facility:

· In the early phase As the accident progresses, the radiation dose to people is formed due to gamma and beta radiation, radioactive substances contained in the radioactive cloud, as well as due to the inhalation of radioactive products into the body. This phase continues from the moment the accident begins until the release of nuclear fission products into the atmosphere ceases and the formation of a radioactive trace on the ground ends. Lasts hours - days.

· In the intermediate phase The source of external radiation is radioactive substances that have fallen from the cloud and are in the environment. They enter the body mainly with contaminated food and water. The middle phase lasts from the moment the formation of the radioactive trace is completed until all measures to protect the population are taken. The duration of this phase should be from several days to a year.

· Late phase lasts until the cessation of protective measures and the lifting of all restrictions on the life of the population in the contaminated area. In this phase, the usual sanitary and dosimetric monitoring of the radiation situation is carried out, and the sources of external and internal radiation are the same as in the middle phase.

In case of accidents at radiation hazardous facilities, the following damaging radiation factors may occur::

· penetrating radiation;

· radioactive contamination of the area.

Penetrating radiation(ionizing radiation) poses a great danger to human health and life .

Ionizing radiation includes:

· alpha radiation, consisting of alpha particles;

· beta radiation - a flow of electrons or positrons;

· gamma radiation, photon (electromagnetic) radiation, which in its nature and properties does not differ from x-rays.

Alpha radiation has the greatest ionizing ability, but its energy quickly decreases, and therefore it does not pose a danger to humans until the substances emitting alpha particles enter the body.

Beta radiation has less ionizing and greater penetrating ability. When radioactive substances come into contact with the skin or inside the body, beta radiation is dangerous for humans.

Gamma radiation with its relatively low ionizing activity, it poses a great danger due to its very high penetrating ability.

The most characteristic of radiation situations arising during accidents at nuclear power plants is the combined radiation impact caused by external (uniform or uneven) beta, gamma irradiation and internal radioactive contamination.

A measure of the damaging effect of ionizing radiation is the dose of this radiation. The degree of adverse effects of radiation is measured in rem. The absorbed dose of radiation is measured in warm, glad.

The assessment of ionizing radiation levels in radioactively contaminated areas is carried out based on the exposure dose rate and is measured in roentgens (milliroentgens) per hour.

Radioactive contamination of the area occurs when radioactive elements fall onto the earth's surface and surrounding objects.

In addition to the above listed radiation damaging factors affecting the human body in the accident zone, it is affected by non-radiation damaging factors:

· shock wave;

· light radiation;

· powerful electromagnetic pulse;

Acute or chronic psycho-emotional overload;

· radiophobia;

· violation of the usual pattern of life, regime and nature of nutrition during long-term forced stay (residence) in a radioactively contaminated area.

As a result of the explosion of a nuclear reactor, shock wave, which can throw a person and hit him against hard objects. Collapsing buildings and flying debris of buildings cause mechanical injuries (bone fractures, bruises, cuts).

An explosion releases a huge amount light and thermal energy, which causes skin burns in humans

integument and respiratory tract of varying degrees of severity.

Electromagnetic pulse can damage various electrical appliances and other equipment.

Non-radiation factors always affect the body in an emergency situation to some extent.

The lower the radiation dose, the more the effects of non-radiation factors appear in the disease picture.

They cause changes in the functional state of various organs and systems, which ultimately determine the body's response, manifested by a symptom complex of a particular disease.

Οʜᴎ reduce the body's resistance to radiation (mutual burden syndrome).

Non-radiation exposures are of particular importance as an etiological factor for a number of pathological conditions in people forced to live for a long time in territories contaminated with radioactive substances (even within acceptable levels).

Such a non-radiation factor in these cases is chronic psychotraumatic effects , caused by the loss of social connections, awareness of the uncertainty of consequences, and economic dependence.

Chronic psychotrauma causes a number of very stable and pronounced disorders in the body, primarily the functional state of general regulatory systems, which predetermine the development of asthenia, autonomic instability, neurocirculatory dystonia, and shifts in the immune system.

These changes are recorded and intensified if they are assessed incorrectly, especially by medical personnel.

Damaging factors of radiation accidents. - concept and types. Classification and features of the category "Damaging factors of radiation accidents." 2017, 2018.

As a result of an accident at a radioactive waste facility, the greatest danger to the population is the radioactive release. As a result of the release, irradiation of people and animals, as well as radioactive contamination of the area, is possible.

In this regard, the main damaging factors during radiation accidents are:

• * exposure to external radiation (beta, gamma, x-ray, neutron radiation, etc.);
• * internal radiation from radionuclides entering the human body (alpha radiation is added to those listed);
• * combined effects due to both external radiation sources and internal radiation;
• * combined effects of both radiation and non-radiation factors (mechanical or thermal injury, chemical burn, etc.)

Routes of entry of radioactive substances into the body:

• * inhalation route;
• * nutritional;
• * through damaged skin;
• * through mucous membranes.

In the formed radioactive trace, the main source of radiation exposure is external irradiation. Inhalation intake of radionuclides is practically excluded if respiratory protection measures are taken in a timely manner. Radioactive substances can enter the body mainly through food and water.

The main nuclides that form internal exposure in the first days after the accident are radioactive isotopes of iodine, which are accumulated by the thyroid gland. The highest concentration of radioactive iodine is found in milk.

Taking into account the distance from the moment of the accident, there are practically two ways for radioactive substances to enter the body: nutritional and inhalation. The toxicity of radioactive substances through inhalation is 2-3 times higher than through the alimentary route, since the route of entry, the mucous membrane of the upper respiratory tract, is located near the lymphoid tissue. After 2-3 months after the accident, the main source of internal radiation becomes radioactive cesium, strontium and plutonium, which can be ingested with food.

Metabolism of radioactive substances in the body:

• Stage 1 - formation of a primary depot (in the mucous membrane of the gastrointestinal tract, upper respiratory tract);
• Stage 2 - absorption into the blood;
• Stage 3 - incorporation in critical organs, depending on the tropism of the substance to the tissues of the body;
• Stage 4 - excretion (80% of all those entering the body). Radioactive substances are excreted by the kidneys (90% of isotopes), the gastrointestinal tract is in second place, and the skin and sweat glands are in third place.

Based on the nature of their distribution in the human body, radioactive substances can be divided into 4 groups:

• 1. localized mainly in the skeleton (calcium, strontium, radium, plutonium);
• 2. concentrated in the liver (cerium, lanthanum, plutonium, etc.);
• 5. evenly distributed among organs and systems (tritium, carbon, inert gases, cesium, etc.);
• 6. Radioactive iodine selectively accumulates in the thyroid gland.

Medical characteristics. Early effects of radiation - acute radiation sickness, local radiation injuries (radiation burns of the skin and mucous membranes) - are most likely in people located near the emergency facility. The possibility of combined injuries to this group of the population due to fires and explosions accompanying the accident cannot be ruled out. Acute or chronic exposure of the population to low doses (less than 0.5 Sv) can lead to long-term radiation effects. These include: cataracts, premature aging, malignant tumors, genetic defects.

The likelihood of oncological and genetic consequences exists even with low doses of radiation. These effects are called stochastic (probable, random). The severity of stochastic effects does not depend on the dose; with increasing dose, only the probability of their occurrence increases. Harmful effects for which there is a threshold dose and severity increase with its increase and are called non-stochastic (radiation cataracts, impaired fertility, etc.).

The consequences of fetal irradiation (teratogenic effects) occupy a special position. The fetus is especially sensitive to radiation at 4-12 weeks of pregnancy.

Based on the foregoing, the main efforts to prevent the pathogenic effects of radioactive substances must be directed to preventing their entry into the body, reducing the degree of exposure of the body to radioactive substances ingested and their rapid removal from the body.

For this purpose, it is necessary to organize the use of personal protective equipment and medical protective equipment by everyone in the outbreak, as well as evacuation in accordance with the “Concept for the protection of the population during accidents at nuclear power plants.”

Characteristics of radiation accidents.

Radiation emergency zone refers to the territory within which, as a result of an accident at a radiation hazardous facility (RHO), radioactive contamination (RC) occurs, causing exposure of people above permissible standards.

The main sources of radioactive contamination are nuclear power plants, nuclear cycle enterprises (uranium enrichment enterprises, nuclear fuel reprocessing enterprises, radioactive waste storage sites), ships with nuclear power plants and spacecraft. There are currently about 400 radiation hazardous facilities operating on Russian territory.

Radiation accident- an event that occurred as a result of loss of control over a source of ionizing radiation, leading to unplanned exposure of people and radioactive contamination of the environment.

Several types of classifications of radiation accidents have been adopted. The most common classification is according to the IAEA (International Atomic Energy Agency) depending on the overall emission activity:

Levels 1-3 (incidents);

4-accident within the nuclear power plant;

5 - accident with risk to the environment;

6 - severe accident (Windscale, England, 1957);

7 - global accident (Chernobyl Nuclear Power Plant, USSR, 1986).

Classes of radiation accidents (according to their scale and consequences):

Local - radiation consequences are limited to one building or structure with possible exposure of personnel.

Local - radiation consequences are limited to the territory of the nuclear power plant, a radiation hazardous facility.

General - radiation consequences extend beyond the border of the territory of the nuclear power plant, a radiation hazardous facility.

As a result of radiation accidents and the use of weapons of mass destruction in conflict situations, damaging factors, causing damage to people, farm animals, vegetation, destruction of buildings, structures, and environmental pollution.

There are two groups of factors that cause injury to people during nuclear explosions and radiation accidents:

Group I – radiation damaging factors :

Penetrating radiation

Radioactive contamination of the area.

Group II – non-radiation damaging factors :

shock wave,

Light radiation,

Electromagnetic pulse,

Acute or chronic psycho-emotional overload,

Radiophobia,

Violations of the usual pattern of life, diet and diet during prolonged forced stay in a radioactively contaminated area.

Penetrating radiation is a stream of neutrons and gamma rays that exert their effect at the moment of explosion and during the subsequent short period of time.

Neutron radiation occurs mainly during nuclear fission and fusion reactions. These reactions occur over a very short period of time (about 10 -6 s), so neutron radiation affects objects located in its propagation zone instantly.

The main sources of gamma radiation are fission fragments of uranium and plutonium nuclei, as well as nitrogen atoms of the air surrounding the explosion zone, which, capturing neutrons, become unstable and emit gamma quanta as excess energy. Due to the decay of short-lived fission products and the rapid rise of the radioactive cloud, the effect of gamma radiation on ground objects after the explosion gradually weakens and completely stops within one minute after the explosion.

Radioactive contamination of the area (REM) is the main and long-lasting radiation damaging factor of radiation accidents and nuclear explosions.

Sources of radioactive contamination of the area are:

· fission products of nuclear fuel (uranium, plutonium);

· undivided part of the fuel.

Radioactive contamination of an area occurs as a result of the fall of radioactive substances (RS) onto the surface of the earth from a radioactive cloud along with precipitation. In extreme situations, an area is considered contaminated if the level of radioactive radiation is at a height of 70 cm from the surface of the earth not less than 0.5 R/h.

Approximately 10 minutes after nuclear explosion the radioactive cloud rises to its maximum height and then moves in the direction of the wind. At the same time, radioactive particles gradually fall out of it and settle on the ground. The radioactive particles that fall out have different sizes and isotopic compositions. At close distances from the explosion site, large particles containing isotopes in a more complete composition (both short-lived and long-lived) settle. At long distances from the explosion site, smaller particles containing only long-lived isotopes settle.

As the cloud moves, its ground trail is formed, which is usually divided into zones of radioactive contamination. The formation of zones of radioactive contamination in the wake of a cloud of a nuclear explosion ends, as a rule, by the end of the day.

In a later period - several weeks after the explosion - radioactive particles go deep into the soil. Volumetric contamination of the top layer of soil is created. The danger of a person staying in a radioactively contaminated area during this period decreases (the intensity of exposure to gamma radiation decreases, the content of radioactive particles in dust raised from the ground decreases).

Feature radiation accidents at nuclear power plants and nuclear reactors is that the process of fission of nuclear fuel used in nuclear reactors continues for a long time. Therefore, in the event of a reactor destruction, radioactive substances (RS) may enter the atmosphere for a long time. The rise of the radioactive substance is carried out to a small height (800–1000 m), which is explained by the low power of the thermal explosion of a nuclear reactor (about 0.04 kt). At this altitude and over a long period of time, the wind changes its direction many times, and therefore there is no clearly visible trace of a radioactive cloud, as in a nuclear explosion. The RV connects with the rain clouds and moves with them. From rain clouds, radioactive substances fall together with precipitation. As a result, contaminated areas can be significant in size and located at very large distances from the accident site, as was the case as a result of the accident at the Chernobyl nuclear power plant.

In case of an accident, destruction of a nuclear power plant, nuclear reactors, the contaminated area is divided into 5 zones based on radiation levels:

M - zone of weak contamination with radiation level 1 hour after the accident = 0.025–0.1 R/h;

A - zone of moderate pollution with radiation levels at the zone boundaries = 0.1–1.0 R/h;

B - medium pollution zone with radiation levels at the zone boundaries = 1.0–3.0 R/h;

B - zone of dangerous contamination with radiation levels at the zone boundaries = 3.0–10.0 R/h;

G - zone of excessively dangerous pollution with radiation levels at the outer boundary of the zone = 10.0 R/h.

Over time, due to the natural decay of radioactive substances, the radiation levels in the trace of a radioactive cloud decrease. For a nuclear explosion, the radiation level decreases 10 times 7 hours after the explosion, 100 times after 2 days, and 1000 times after 7 weeks.