Radiation dose unit. Doses of ionizing radiation

Absorbed radiation dose D is determined by the ratio of the average energy dW transferred by ionizing radiation to a substance in a volume element to the mass dm of a substance in this volume:

D= dW / dm;

The unit of absorbed dose in SI is joule per kilogram (J / kg), which corresponds to the absorption of 1 J of energy of any type of ionizing radiation in 1 kg of the irradiated substance. This unit of dose is commonly referred to as gray (Gy). The off-system unit of the absorbed radiation dose is rad; 1 rad corresponds to the absorption of 100 erg of energy of any kind of ionizing radiation in 1 g of the irradiated substance. That. 1 J / kg = 1 Gy = 100 rad.

The energy W, transferred to a substance by ionizing radiation in some of its volume, is equal to the difference between the sum of energies (ΣЕ in) of all directly or indirectly ionizing particles entering the volume (excluding the rest energy of particles) and the sum of energies (ΣЕ out) of all leaving the volume directly or indirectly ionizing particles (excluding the rest energy of particles) plus
- the sum of all released energies in any nuclear reactions, transformations and processes with elementary particles that took place inside the volume, minus the sum of all energies spent in these reactions, transformations and processes in the same volume.

If the rest mass changes in the elementary volume due to the transformation of nuclei or elementary particles, then this effect is taken into account by the corresponding energy equivalent in the term
, and is taken with a plus sign when the rest mass decreases and with a minus sign when it increases. That.,

Absorbed dose rate
in the SI system has the dimension
... Non-system unit - .
.

The energy absorbed in 1 g of tissue under conditions of equilibrium of charged particles at
is
... In air, under conditions of equilibrium of charged particles, the energy corresponding to an exposure dose of 1 r corresponds to an absorbed dose of 0.877 rad.

Such a state of interaction of photon radiation with matter, in which the energy of electrons released by photons into a certain volume is equal to the energy carried away by electrons from the same volume, is called electronic equilibrium. Electronic equilibrium condition:

,

where - vector of radiation energy, depending on coordinates. Under this condition, according to the formula
, wherein B- energy of bremsstrahlung, - density, K- kerma (the ratio of the sum of the initial kinetic energy
of all charged particles created indirectly by ionizing radiation in an elementary volume of a substance, to the mass of a substance
in this volume:
, measured in SI in grays), D- absorbed dose, the condition of absolute electronic equilibrium is determined
, if
... In general
, where
Is the fraction of electron energy converted into bremsstrahlung energy.

4. Equivalent dose. Relative biological effectiveness (OBE). Radiation quality factor. Equivalent dose units.

To assess the biological effect of exposure to radiation of arbitrary composition, it was necessary to introduce a new dose characteristic. In the problems of radiation safety under irradiation in low doses (less than ~ 0.1 Gy), this is the equivalent dose with a SI unit of measurement - sievert (Sv). Sievert is a unit of an equivalent dose of any kind of radiation in biological tissue, which creates the same biological effect as an absorbed dose of 1 Gy of reference X-ray radiation (radiation with a boundary energy of 200 keV). The non-systemic unit of the equivalent dose is rem (biological equivalent is glad). Rem is a unit of an equivalent dose of any kind of radiation in biological tissue, which creates the same biological effect as an absorbed dose of 1 rad of exemplary X-ray radiation. Thus, 1 Sv = 100 rem.

To compare the biological effects produced by the same absorbed dose of different types of radiation, the term "relative biological effectiveness" (RBE) is used. RBE of radiation is understood as the ratio of the absorbed dose of the reference X-ray radiation to the absorbed dose of the given type of radiation under consideration, provided that these doses cause the same biological effect. The regulated RBE values ​​established to control the degree of radiation hazard during chronic exposure are called the radiation quality factor K... This dimensionless coefficient determines the dependence of the unfavorable biological consequences of human exposure in low doses on the total linear energy transfer (LET) of radiation (Table No. 10)

Tab. 10... Dependence of the quality factor on the LET.

	3,5				175

For - quanta, electrons and positrons K=1 .

If the spectral composition of the radiation is unknown, it is recommended to use the values K, given in table. eleven.

Tab. eleven... The values K for radiation of various types with unknown spectral composition.

Type of radiation
X-ray, -radiation, -radiation
Neutrons with energies less than 20 keV
Neutrons with energies 0.1 - 10 MeV
Protons with energies less than 10 MeV
- radiation with energy less than 10 MeV
Heavy recoil kernels

For neutrons and protons of different energies, the values ​​of the quality factor are given in table. 12.

Tab. 12... The values K for protons and neutrons.

Neutron energy, MeV		Neutron energy, MeV		Energy of protons, MeV		Energy of protons, MeV

Equivalent dose of radiation ( H) is determined by the product of the absorbed dose ( D) radiation in tissue by the quality factor ( K) of this radiation:

.

If D is measured in Gr, then H- in sieverts, if D- in Rada, then H- in rem.

So the quality factor K radiation is a coefficient that depends on the LET, by which the absorbed dose must be multiplied so that the biological effect of irradiation of people is expressed in the same measure, regardless of the type of radiation.

For mixed radiation H define as

where D i are the absorbed doses of certain types of radiation, K i are the corresponding quality factors of these radiations.

In connection with the last remarks, the unit of equivalent dose - Sievert can be determined in this way: Sievert is equal to such an equivalent dose at which the product of the absorbed dose in biological tissue of standard composition by the average radiation quality factor is equal to 1 J / kg.

In a biological object, the radiation dose is distributed unevenly. Its distribution is determined by the accumulation of secondary ionizing particles and the attenuation of the primary radiation of the source in the object. Competition between these two processes can lead to the appearance of a noticeable maximum in the dose distribution. For example, for thermal neutrons, it is observed at a depth of about 3 mm. At an energy of 5–20 keV, the dose maximum shifts into the body (by several centimeters). With a further increase in energy, the maximum dose approaches the surface and with about E = 100 keV is localized on it. Further, at energy Е≥ (2.5-5) MeV, the maximum dose is again shifted into the interior of the body (research on phantoms).

The action of ionizing radiation is a complex process. The effect of irradiation depends on the magnitude of the absorbed dose, its power, type of radiation, and the volume of irradiation of tissues and organs. For its quantitative assessment, special units have been introduced, which are divided into non-systemic and units in the SI system. Currently, SI units are used predominantly. Below (in table 1.) a list of units of measurement of radiological quantities is given and a comparison of SI units and non-SI units is made.

Table 1.

Basic radiological quantities and units
The magnitude	Name and designation of the unit of measure	Relationships between units
Non-systemic
Nuclide activity, А	Curie (Ki, Ci)	Becquerel (Bq, Bq)	1 Ki = 3.7 * 1010Bq1 Bq = 1 dec / s 1 Bq = 2.7 * 10-11Ci
Exposure dose, X	X-ray (P, R)	Pendant / kg (C / kg, C / kg)	1 R = 2.58 * 10-4 C / kg 1 C / kg = 3.88 * 103 R
Absorbed dose, D	Rad (glad, rad)	Gray (Gr, Gy)	1 rad-10-2 Gy 1 Gy = 1 J / kg
Equivalent dose, N	Rem (rem, rem)	Sievert (Sv, Sv)	1 rem = 10-2 Sv 1 Sv = 100 rem
Integral dose of radiation	Rad-gram (rad * g, rad * g)	Gray kg (Gr * kg, Gy * kg)	1 rad * g = 10-5 Gy * kg 1 Gy * kg = 105 rad * g

The following concepts and units of measurement are used to describe the effect of ionizing radiation on a substance:

Radionuclide activity in the source (A). The activity is equal to the ratio of the number of spontaneous nuclear transformations in this source over a short time interval (dN) to the value of this interval (dt):

The SI unit of activity is Becquerel (Bq).

Non-systemic unit - Curie (Ki).

The number of radioactive nuclei N (t) of a given isotope decreases with time according to the law:

N (t) = N0 exp (-tln2 / T1 / 2) = N0 exp (-0.693t / T1 / 2)

where No is the number of radioactive nuclei at time t = 0, T1 / 2 half-life is the time during which half of the radioactive nuclei decays.

The mass m of the radionuclide with activity A can be calculated by the formula:

m = 2.4 * 10-24 M T1 / 2 A

where M is the mass number of the radionuclide, A is the activity in Becquerels, and T1 / 2 is the half-life in seconds. The mass is obtained in grams. Exposure dose (X). As a quantitative measure of X-ray and γ-radiation, it is customary to use the exposure dose in off-system units, which is determined by the charge of secondary particles (dQ) formed in the mass of the substance (dm) upon complete deceleration of all charged particles:

The exposure dose unit is Roentgen (R). X-ray is an exposure dose of X-ray and γ-radiation, which creates 1 cubic cm of air at a temperature of O ° C and a pressure of 760 mm Hg. the total charge of ions of the same sign in one electrostatic unit of the amount of electricity.

An exposure dose of 1 R corresponds to 2.08 * 109 pairs of ions (2.08 * 109 = 1 / (4.8 * 10-10)). If we take the average energy of formation of 1 pair of ions in air equal to 33.85 eV, then at an exposure dose of 1 P, one cubic centimeter of air is transferred energy equal to:

(2.08 * 109) * 33.85 * (1.6 * 10-12) = 0.113 erg,

and one gram of air:

0.113 / air = 0.113 / 0.001293 = 87.3 erg.

The absorption of the energy of ionizing radiation is the primary process that gives rise to a sequence of physicochemical transformations in the irradiated tissue, leading to the observed radiation effect. Therefore, it is natural to compare the observed effect with the amount of absorbed energy or absorbed dose.

The absorbed dose (D) is the main dosimetric quantity. It is equal to the ratio of the average energy dE transferred by ionizing radiation to a substance in an elementary volume to the mass dm of a substance in this volume:

The unit of the absorbed dose is Gray (Gy). The off-system unit Rad was defined as the absorbed dose of any ionizing radiation equal to 100 erg per 1 gram of the irradiated substance.

Equivalent dose (N). To assess the possible damage to human health under conditions of chronic exposure in the field of radiation safety, the concept of an equivalent dose H was introduced, which is equal to the product of the absorbed dose Dr created by irradiation - r and averaged over the analyzed organ or throughout the body by the weight factor wr (also called the quality factor radiation) (table 2).

The unit of measure for equivalent dose is Joule per kilogram. It has the special name Sievert (Sv).

Table 2.

Radiation weighting factors
Type of radiation and energy range	Weight factor
Photons of all energies
Electrons and muons of all energies
Neutrons with energy< 10 КэВ
Neutrons from 10 to 100 keV
Neutrons from 100 keV to 2 MeV
Neutrons from 2 MeV to 20 MeV
Neutrons> 20 MeV
Protons with energies> 2 MeV (except for recoil protons)
Particles, fission fragments and other heavy nuclei

The effect of radiation is uneven. To assess the damage to human health due to the different nature of the effect of radiation on different organs (under conditions of uniform irradiation of the whole body), the concept of an effective equivalent dose E eff is introduced, which is used to assess possible stochastic effects - malignant neoplasms.

The effective dose is equal to the sum of the weighted equivalent doses in all organs and tissues:

where w t - tissue weight factor (table 3), and H t - equivalent dose absorbed in tissue - t. The unit of the effective equivalent dose is Sievert.

Table 3

Collective effective equivalent dose. To assess the damage to the health of personnel and the population from stochastic effects caused by the action of ionizing radiation, the collective effective equivalent dose S is used, defined as:

where N (E) is the number of persons who received an individual effective equivalent dose E. The unit of S is man-Sievert (man-Sv).

Radionuclides - radioactive atoms with a given mass number and atomic number, and for isomeric atoms - and with a given specific energy state of the atomic nucleus. Radionuclides (and non-radioactive nuclides) of an element are otherwise called isotopes.

In addition to the above values, to compare the degree of radiation damage to a substance when it is exposed to various ionizing particles with different energies, the value of linear energy transfer (LET) is also used, determined by the ratio:

where is the average energy locally transferred to the medium by the ionizing particle due to collisions on the elementary path dl. Threshold energy usually refers to the energy of an electron. If, in the collision event, the primary charged particle forms an -electron with an energy greater, then this energy is not included in the value of dE, and -electrons with energy are considered more as independent primary particles.

The choice of the threshold energy is arbitrary and depends on specific conditions.

It follows from the definition that the linear transfer of energy is a kind of analogue of the stopping power of a substance. However, there is a difference between these values. It consists in the following:

• 1. LET does not include energy converted to photons, i.e. radiation losses.
• 2. For a given threshold, the LET does not include the kinetic energy of particles exceeding.

The values ​​of the LET and the stopping power coincide if the losses due to bremsstrahlung and

ionizing radiation dosimeter

Table 4

The value of the linear energy transfer can be used to determine the weighting factor of this type of radiation (table 5)

Table 5

Maximum permissible radiation doses according to NRB-99

In relation to exposure, the population is divided into 3 categories:

Category B of exposed persons or a limited part of the population - persons who do not work directly with sources of ionizing radiation, but due to the living conditions or placement of workplaces may be exposed to ionizing radiation.

• - the main dose limits (PD), given in table 6;
• - permissible levels of mono-factor exposure (for one radionuclide, route of entry or one type of external exposure), which are derived from the main dose limits: annual intake limits (GWP), permissible average annual volumetric activities (DOA), average annual specific activities (ARS), and others;
• - control levels (doses, levels, activity, flux density, etc.). Their values ​​should take into account the level of radiation safety achieved in the organization and ensure the conditions under which the radiation exposure will be below the permissible level.

Table 6 Main dose limits

Notes:

• * Allowed simultaneous irradiation up to the specified limits for all standardized values.
• ** The main dose limits, like all other permissible exposure levels for personnel in group B, are equal to 1/4 of the values ​​for personnel in group A. Further in the text, all standard values ​​for the category of personnel are given only for group A.
• *** Refers to a dose at a depth of 300 mg / cm2.
• **** Refers to the average value over the area in I cm2 in the basal layer of the skin with a thickness of 5 mg / cm2 under the integumentary layer of 5 mg / cm2. On the palms, the thickness of the casing layer is 40 mg / cm2. The specified limit is allowed to irradiate all human skin, provided that within the limits of the average exposure of any 1 cm2 of skin area, this limit is not exceeded. The dose limit for irradiation of the facial skin ensures that the dose limit for the lens from beta particles is not exceeded.

The main limits for radiation doses do not include doses from natural and medical exposure, as well as doses due to radiation accidents. These types of exposure are subject to special restrictions.

The effective dose for personnel should not exceed 1000 mSv for the period of labor activity (50 years), and for the population for the period of life (70 years) - 70 mSv. The beginning of the periods is introduced from January 1, 2000.

With the simultaneous exposure of a person to sources of external and internal radiation, the annual effective dose should not exceed the dose limits established in table. 6.

Three groups of critical organs are established:

• Group 1 - the whole body, gonads and red bone marrow;
• Group 2 - muscles, thyroid gland, adipose tissue, liver, kidneys, spleen, gastrointestinal tract, lungs, lenses of the eyes and other organs, except for those belonging to groups 1 and 3;
• Group 3 - skin, bone tissue, hands, forearms, legs and feet.

Dose limits of exposure for different categories of persons are given in Table 7.

Table 7

In addition to the basic dose limits, derivative standards and reference levels are used to assess the effect of radiation. The standards are calculated taking into account the non-exceeding of the dose limits of the PDD (maximum permissible dose) and PD (dose limit). The calculation of the permissible content of a radionuclide in the body is carried out taking into account its radiotoxicity and non-exceeding of the SDA in the critical organ. The reference levels should provide such low levels of exposure as can be achieved by adhering to the basic dose limits.

• - the maximum permissible annual intake of the RAP radionuclide through the respiratory system;
• - the permissible content of the radionuclide in the critical organ of the DSA;
• - permissible dose rate of DMDA radiation;
• - admissible flow density of DPPA particles;
• - permissible volumetric activity (concentration) of the radionuclide in the air of the DSC working area;
• - permissible contamination of the skin, overalls and working surfaces of the DZA.

• - the limit of the annual intake of the GWP radionuclide through the respiratory or digestive organs;
• - permissible volumetric activity (concentration) of the DKB radionuclide in atmospheric air and water;
• - permissible dose rate of DMDB;
• - permissible particle flux density DPPB;
• - permissible contamination of the skin, clothing and surfaces of the DZB.

Numerical values ​​of permissible levels are contained in full in the "Radiation Safety Standards".

2Characteristics of the DKS-101 measuring device

The universal dosimeter (hereinafter referred to as the dosimeter) is intended for absolute measurements of the absorbed and equivalent dose and the absorbed and equivalent dose rate for a wide range of energies of photon and electron radiation, precision measurement of ionizing radiation dose fields of medical and industrial devices and devices.

The device can be used to conduct dosimetric and physical studies in laboratory and industrial conditions, incl. for verification of dosimetry equipment, certification of X-ray rooms and industrial X-ray and electronic installations, etc.

The dosimeter can be certified as a working standard of the 1st or 2nd category.

The dosimeter works steadily when the ambient temperature changes from + 10C to + 40C and in conditions of ambient relative humidity up to 80% at a temperature of + 30C without moisture condensation, atmospheric pressure from 84 to 106.7 kPa (from 630 to 800 mm Hg). Art.).

It is completed with ionization chambers, control sources and a water phantom at the request of the customer.

Consists of an electrometric unit with a built-in controlled high-voltage source and a personal computer.

Built-in self-diagnostics systems, a set of functions for mathematical processing and recording of measurement results, software in the Windows98 environment provide ease of use and a wide range of service functions.

Technical details

The dosimeter provides the following types of measurements: absorbed dose in water (Gy), equivalent dose (Sv), corresponding dose rates, charge (C), current (A) (current and charge measurement errors are not standardized). The dosimeter has an automatic stop of measurements when the set thresholds for dose and time are reached. Measurement of air kerma (Gy), exposure dose (P) and corresponding dose rates can be performed at the request of the customer.

Digital resolution, zero stability, high-voltage source voltage range and maximum measurement time of the dosimeter are shown in Table 2.1.

Table 2.1

The dosimeter has the measurement ranges shown in Table 2.2.

Table 2.2

The level of the dosimeter's own background.

After the time of establishing the operating mode (without connecting the ionization chamber) no more than 510-15 A.

For 8 hours of continuous operation after the time of establishing the operating mode (without connecting the ionization chamber) no more than 110-14 A.

From readings under normal conditions (without connecting an ionization chamber) when the temperature changes in the operating temperature range from +10 to + 40C, no more than 210-14 A.

From readings under normal conditions (without connecting an ionization chamber) when the relative air humidity changes to 80% at a temperature of 30 C, no more than 110-14 A.

The instability of the dosimeter readings for 8 hours of continuous operation after the time of setting the operating mode is not more than 0.2% on the sensitive measurement range of the MPD (integral of MPD and PD).

Time to establish indications no more:

• 100 s - in the sensitive range;
• 10 s - on other bands.

The limits of the permissible additional measurement error are:

from readings under normal conditions when the temperature changes in the operating temperature range from +10 to + 40C when measuring the MPD (integral of MPD and PD) - 0.2%.

from readings under normal conditions when the relative humidity of the air changes up to 80% at a temperature of 30C when measuring the MPD (integral of MPD and PD) - 0.2%.

from the readings under normal operating conditions in a constant magnetic field with a strength of not more than 400 A / m when measuring the MPD (integral of MPD and PD) - 0.2%.

The dosimeter is powered from a single-phase AC network with a frequency of 50 Hz 1 Hz, harmonic content up to 5% and rated voltage of 220 V with a permissible deviation of -15% to + 10%.

The power consumed from the mains by the electrometric unit at a rated supply voltage is not more than 4 VA.

The insulation between the body of the electrometric unit and the contacts of the mains power cable plug withstands for 1 minute without breakdown the action of the 4000 V DC test voltage. The insulation resistance of the above circuits is not less than 20 MΩ under normal conditions.

MTBF is at least 3000 hours.

Average service life is not less than 6 years.

Execution of the electrometric unit IP30C (in accordance with GOST 14254-96).

The overall dimensions and weight of the unit are given in table. 2.3.

Table 2.3

Climatic version of the dosimeter B1 GOST 12997-84.

The dosimeter works steadily when the ambient temperature changes from + 10C to 40C and in conditions of ambient relative humidity up to 80% at a temperature of + 30C without moisture condensation, atmospheric pressure from 84 to 106.7 kPa (from 630 to 800 mm Hg .).

The electrometric unit has mechanical strength in accordance with the requirements for products of group L1 GOST 12997-84.

Handbook for citizens "Caution! Radiation"

Basic units of measurement of ionizing radiation

Exposure dose(two units)

X-ray (P) - off-system unit of exposure dose. This is the amount of gamma or X-ray radiation that in 1 cm ^ 3 of dry air (having a weight of 0.001293 g under normal conditions) forms 2.082 x 10 ^ 9 pairs of ions. These ions carry a charge of 1 e-static unit of each sign (in the CGSE system), which in units of work and energy (in the CGS system) will amount to about 0, 114 erg of energy absorbed by air (6.77 x 10 ^ 4 MeV). (1 erg = 10 ^ -7 J = 2.39 x 10 ^ -8 cal). When recalculated for 1 g of air, this will be 1.610 x 10 ^ 12 pairs of ions or 85 erg / g of dry air. Thus, the physical energy equivalent of an X-ray is 85 erg / g for air. (According to some sources it is equal to 83.8, according to others - 88.0 erg / g).

1 Cl / kg - the unit of the exposure dose in the SI system. This is such an amount of gamma or X-ray radiation, which in 1 kg of dry air forms 6.24 x 10 ^ 18 pairs of ions, which carry a charge of 1 coulomb of each sign. (1 pendant = 3 x 10 ^ 9 CGSE units = 0.1 CGSM units). The physical equivalent of 1 C / kg is 33 J / kg (for air).

The ratios between X-ray and C / kg are as follows:

1 P = 2.58 x 10 ^ -4 C / kg - exactly.

1 C / kg = 3.88 x 10 ^ 3 R - approx.

Absorbed dose(two units)

Glad is a non-systemic unit of the absorbed dose. Corresponds to the radiation energy of 100 erg, absorbed by a substance weighing 1 gram (one hundredth part of "Gray" - see).

1 rad = 100 erg / g = 0.01 J / kg = 0.01 Gy = 2.388 x 10 ^ -6 cal / g

With an exposure dose of 1 X-ray, the absorbed dose in the air will be 0.85 rad (85 erg / g).

Gray (Gr.) - the unit of the absorbed dose in the SI system of units. Corresponds to the radiation energy of 1 J, absorbed by 1 kg of matter.

1 Gr. = 1 J / kg = 10 ^ 4 erg / g = 100 rad.

Equivalent dose(two units)

Baer - the biological equivalent of X-rays (in some books - glad). Non-systemic unit of equivalent dose measurement. In general:

1 rem = 1 rad * K = 100 erg / g * K = 0.01 Gy * K = 0.01 J / kg * K = 0.01 Sievert

With the radiation quality factor K = 1, that is, for X-ray, gamma, beta radiation, electrons and positrons, 1 rem corresponds to an absorbed dose of 1 rad.

1 rem = 1 rad = 100 erg / g = 0.01 Gy = 0.01 J / kg = 0.01 Sievert

It is especially necessary to note the following fact. Back in the 50s, it was found that if at an exposure dose of 1 X-ray air absorbs 83.8 × 88.0 erg / g (the physical equivalent of an X-ray), then the biological tissue absorbs 93 × 95 erg / g (the biological equivalent of an X-ray) ... Therefore, it turns out that when assessing doses, it can be assumed (with a minimum error) that an exposure dose of 1 X-ray for biological tissue corresponds (is equivalent) to an absorbed dose of 1 rad and an equivalent dose of 1 rem (at K = 1), that is, roughly saying that 1 R, 1 rad and 1 rem are the same thing.

Sievert (Sv) is the SI unit of equivalent and effective equivalent doses. 1 Sv is equal to the equivalent dose at which the product of the absorbed dose in Grays (in biological tissue) by the coefficient K will be equal to 1 J / kg. In other words, this is such an absorbed dose at which 1 J of energy is released in 1 kg of a substance.

In general:

1 Sv = 1 Gr. K = 1 J / kg. K = 100 glad. K = 100 rem

At K = 1 (for X-ray, gamma, beta radiation, electrons and positrons) 1 Sv corresponds to an absorbed dose of 1 Gy:

1 Sv = 1 Gy = 1 J / kg = 100 rad = 100 rem.

In conclusion, we recall once again that for X-ray, gamma, beta radiation, electrons and positrons, the values ​​of X-ray, rad and rem, as well as (separately) the values ​​of Gray and Sievert, turn out to be equivalent in assessing human exposure.

Example.

If a background (from gamma radiation) of 25 μR / hour (25 μR / hour; 0.25 μGy / hour; 0.25 μSv / hour) is recorded in any place, then for 1 hour of stay in this place a person will receive an equivalent dose (ED) of 25 μrem (0.25 μSv). For a week, respectively:

ED = 25 μR / hour * 168 h = 4200 μrem = 4.2 mrem = 42 μSv or 0.042 mSv,

and for the year:

ED = 25 μR / h * 8760 h = 219000 μrem = 219 mrem = 2.19 mSv.

But if the same absorbed dose is created by alpha radiation (for example, with internal irradiation), then, taking into account the quality factor (20), the equivalent dose in 1 hour will be:

ED = 25 μR / hour * 20 * 1 hour = 500 μR = 500 μrem = 0.5 mrem = 5 μSv,

that is, it will be equivalent to the absorbed dose from X-rays, gamma, beta radiation, 500 mrad (5 mcGy).

But I would like to draw the reader's special attention to the sharp discrepancy between the dose received, that is, the energy released in the body, and the biological effect. So long ago it became obvious that the same doses received by a person from external and internal irradiation, as well as doses received from different types of ionizing radiation, from different radionuclides (when they enter the body) cause different effects! And an absolutely lethal dose of 1000 roentgens in units of thermal energy for a person is only 0.0024 calories. This amount of thermal energy can only heat about 0.0024 ml of water by 1 C (0.0024 cm ^ 3 0.0024 g), that is, only 2.4 mg of water. With a glass of hot tea, we get thousands of times more. At the same time, doctors, scientists, atomic scientists operate with doses of milli- and even micro-X-rays. That is, they indicate such accuracy, which in fact does not exist.

The effect of radiation on the human body. Radiation effects

Radioactive radiation is called ionizing radiation and radioactive particles are called ionizing particles.

As already mentioned, radioactive particles, possessing tremendous energy, tremendous speeds, when passing through any substance, collide with atoms and molecules of this substance and lead to their destruction, ionization, to the formation of "hot" (high-energy) and extremely reactive particles - fragments of molecules : ions and free radicals.

The same thing happens in the tissues of biological objects. At the same time, since the biological tissues of a person are 70% water, it is primarily water molecules that are subjected to ionization to a large extent. From fragments of water molecules - from ions and free radicals - extremely harmful and reactive peroxide compounds are formed, which trigger a whole chain of sequential biochemical reactions and gradually lead to the destruction of cell membranes (cell walls and other structures).

In general, the impact of radiation on biological objects and, first of all, on the human body causes three different negative effects.

First - This is a genetic effect for the hereditary (reproductive) cells of the body. It can and does manifest itself only in offspring. This is the birth of children with various deviations from the norm (deformities of varying degrees, dementia, etc.), or the birth of a completely unviable fetus - with deviations that are incompatible with life.

To a large extent, the "suppliers" of such children to the respective hospitals are nuclear energy enterprises and their zones of influence.

Second - this is also a genetic effect, but for the hereditary apparatus of somatic cells - body cells. It manifests itself during the life of a particular person in the form of various (mainly cancer) diseases. The "suppliers" of cancer patients are also, to a large extent, atomic energy enterprises and their zones of influence.

Third the effect is the somatic effect, or rather the immune one. This is a weakening of the defenses, the immune system of the body due to the destruction of cell membranes and other structures. It manifests itself in the form of the most diverse, including, it would seem, completely unrelated to radiation exposure, diseases, in an increase in the number and severity of the course of diseases, in complications, as well as in the weakening of memory, intellectual abilities, etc. Weakening of immunity provokes the occurrence of any diseases, including cancer.

It should be especially noted that all visible physical deviations from the norm, all diseases are accompanied by a weakening of mental abilities, memory, intelligence.

A retrospective analysis and study of the current state of health of the population in the zone of influence of the Krasnoyarsk Mining and Chemical Complex showed that the increase in various diseases of both children and adults is several times greater than in the control regions. A similar picture is typical for the zones of influence of all nuclear facilities around the world.

It should always be borne in mind that the best protection against radiation, against any radiation, is distance and time:

- the shorter the time spent in the irradiation zone, the better.

Radiation affects people in different ways, depending on gender and age, the state of the body, its immune system, etc., but especially strongly - on infants, children and adolescents.

When exposed to radiation (especially low-background radiation), the latent (incubation, latency) period, that is, the delay time before the onset of a visible effect, can last for years and even decades. (from Ralph Greib's book "The Petko Effect: The Impact of Low Doses of Radiation on People, Animals and Trees")

The Petko Effect: A New Dimension of Radiation Threat?

In 1972, Abram Petko of the Weitshell nuclear research facility of the Canadian Atomic Energy Commission in Manitoba made an accidental discovery that earned (according to Ralph Greib) the Nobel Prize. He found that with prolonged irradiation, cell membranes broke at a significantly lower total dose than if this dose was given by a short flash, as in an X-ray study.

So, irradiation with an intensity of 26 rad / min destroyed the cell membrane in 130 minutes with a total dose of 3500 rad. When irradiated with an intensity of 0.001 rad / min (26000 times less), 0.7 rad was sufficient (time about 700 min). That is, 5000 times less dose was enough for the same effect.

It was concluded that the longer the irradiation period was, the lower the total dose required.

It was a discovery. Low doses of chronic exposure turned out to be more dangerous in terms of consequences than large doses of short-term (acute) exposure. This revolutionary new discovery is in sharp contrast to the genetic effect of radiation on the cell nucleus. In all such studies, there was no difference in effect between the total dose received over a short period of time or over a long period. An almost constant effect of 1 rad was observed for a whole spectrum of dose intensities, ranging from the smallest to the largest. For a long time it was believed that the DNA molecule, which carries genetic information, is directly destroyed in the nuclei of cells under the influence of radiation. Petko discovered that in the case of cell membranes, a different mechanism operates, producing indirect destruction.

How small doses can be more dangerous than large ones?

There is a lot of water in the cells. Under the influence of radiation, highly toxic unstable oxygen forms - free radicals, peroxide compounds - appear. They react with the cell membrane, where they start a chain reaction of chemical transformations - oxidation of membrane molecules, as a result of which it is destroyed. That is, it is not the direct effect of radiation that is observed, but the consequences.

Quotes

"Serious damage from small long-term or chronic doses of radiation: the fewer free radicals in the cell plasma, the higher their effectiveness in causing damage. This is because free radicals can deactivate each other to form a normal oxygen molecule or others (recombination). The less free radicals are created by radiation in a given volume per unit of time (at lower radiation intensities), the less chance they have to reach the cell wall. "

"Less damage from high short-term radiation doses: the more free radicals are formed in a given volume (at high doses per unit time), the faster they recombine and become ineffective before reaching and hitting the membrane."

In addition, there is a long-range effect. Cell membranes create an electric field in the cell's plasma that attracts negatively charged molecules such as a highly toxic free radical. Computer calculations have shown that the higher the concentration of free radicals, the weaker the attraction by the electric field. Therefore, if the concentration of radicals is high, they are less likely to reach the membrane than if there are few of them.

Thus, in contrast to cell nuclei, the cell membrane is less severely damaged (per unit of absorbed dose) with a short-term but powerful dose (alpha radiation, intense X-ray irradiation, etc.) than with prolonged or chronic exposure from a radiation background of low level, from radioactive fallout, emissions from nuclear power plants.

Radiation background

Sources of ionizing radiation (IRS) are divided into natural (natural) and artificial (man-made, technogenic).

Natural radiation sources include various types of cosmic radiation and natural radionuclides contained in the earth's crust, in the environment, in plants and animals, including the human body.

According to the UN, the contribution of various radiation sources to the average annual effective equivalent dose of radiation to an average person is as follows. Natural radiation sources account for 2 mSv (or 82.61%), and man-made ones - 0.421 mSv (17.39%); in the amount of 2.421 mSv.

In this case, natural (natural) exposure consists of "earthly" and "cosmic". The share of "terrestrial" is 1.675 mSv (69.186%), including the share of internal irradiation - 1.325 mSv (54.729%), the share of external - 0.35 mSv (14.457%). And the share of space - 0.315 mSv (13.011%). All% are given from the total amount of 2.421 mSv.

Technogenic exposure consists of radiation during medical examinations and treatment (0.4 mSv; 16.522%), radiation from radioactive fallout (0.02 mSv; 0.826%) and from nuclear power (0.001 mSv; 0.041%).

The natural background of external radiation on the territory of the USSR fluctuates widely, but it is believed that on average it creates an exposure dose rate of 4.20 μR / hour (40.200 mR / year). The equivalent dose from natural sources of ionizing radiation is also 40-200 mrem / year (0.05-0.2 μSv / hour; 0.4-2.0 mSv / year) and is considered absolutely safe.

But all this is averaged, average statistical data. Therefore (for illustrative purposes only) we will provide some more specific facts and figures.

Thus, a passenger of a jet aircraft receives an average dose of 0.027 mSv (2.7 mrem) for 4 hours of flight, because the level (or background) of cosmic radiation in the aircraft cabin reaches 200 μR / hour and higher, depending on the flight altitude. At an altitude of 12 thousand meters above sea level, the level of cosmic radiation reaches 5 μSv / h (500 μR / h). People living at an altitude of 2000 m above sea level receive a dose 3-4 times greater than those living at sea level (excluding "earth" radiation), since at sea level the "cosmic" background is 0.03 μSv / h (3 μR / hour), and at the indicated height - 0.1 μSv / hour (10 μR / hour). Those living on the equator receive a lower dose than northerners, etc.

The picture of purely "terrestrial" radiation is also varied. 95% of the population of France, Germany, Italy, Japan and the United States (according to the UN) lives in places where the annual dose rate of radiation varies from 0.3 to 0.6 mSv (background from 3-5 to 8-10 μR / hour) ; 3% of the population receive an average of 1 mSv (11-15 μR / hour); 1.5% - more than 1.4 mSv (18-20 μR / hour). But there are areas of land (including resorts) with permanent residence of the population, where the level of "terrestrial" radiation is 600-800 times higher than the average. Some groups of people receive more than 17 mSv per year only from external exposure to "terrestrial" radiation, which is 50 times more than the average annual dose of external exposure; often reside (temporarily reside) in areas where the radiation level reaches 175 mSv / year (227 μR / hour), etc.

Granite rocks, for example, can give background up to 30-40 and more microR / hour.

Waste (slag, ash, soot, coal dust) of coal-fired thermal power plants, state district power stations, boiler houses, etc. have increased radioactivity.

Assessment of the amount of radium and thorium in some building materials (carried out in a number of countries) gives the following picture (in Bq / kg):

As you can see, ordinary sand and gravel have tenfold activity, while brick, granite, and ash are hundreds of times more active than wood.

• wood (Finland) - 1.1
• sand and gravel (FRG) - 30
• brick (Germany) - 126
• granite (UK) - 170
• fly ash (FRG) - 341
• alumina (Sweden) - 500-1400
• calcium silicate slag (USA) - 2140
• waste from uranium enrichment factories (USA) - 4625

Internal exposure of a person is greater than external exposure and on average is 2/3 of the effective equivalent dose that a person receives from natural sources of radiation. It is created by radionuclides that enter the body with food, water, air.

These include the potassium-40 radioisotope and the nuclides of the radioactive decay series of uranium-238 and thorium-232. These are, first of all, lead-210, polonium-210 and, most importantly, radon-222 and 220.

Lead and polonium are concentrated in fish and shellfish, as well as in the meat of reindeer (which obtain them by feeding on lichens). But the main contribution to the internal exposure of humans is made by radon. It accounts for 3/4 of the dose from "terrestrial" sources of radiation and about half of all natural ones.

The main part of the "radon" radiation dose, paradoxically, is received by a person in closed, unventilated rooms. In areas with a temperate climate, the concentration of radon in such rooms is on average 8 times higher than in the outside air. But this is on average. And if the room is heavily sealed (for example, for the purpose of insulation) and is rarely ventilated, then the radon concentration can be tens and hundreds of times higher, which is observed in some northern countries. Sources of radon are foundations of buildings, building materials (especially those prepared using waste from thermal power plants, boiler houses, slag, ash, waste rock and heaps of some mines, mines, processing plants, etc.), as well as water, natural gas, soil. Being an inert gas, it easily penetrates into the room through all cracks, pores from the ground, basements (especially in winter), walls, as well as with dust, soot, ash from coal thermal power plants, etc.

In general, "terrestrial" radiation sources add up to about 5/6 of the annual effective equivalent dose from all natural sources.

Now for a few examples regarding artificial sources of AI. As already shown, their contribution to the total dose is, according to UN estimates, 0.421 mSv (17.39%), with the main share accounted for by radiation during medical examinations and treatment - 0.4 mSv (or 95% of this figure). Naturally, for a specific person who has never visited the X-ray room, etc., there can be no question of any doses "from medicine". On the other hand, the dose received by a person as a result of an accident at a nuclear power plant, nuclear weapons tests, etc., may turn out to be hundreds and thousands of times greater than during any medical examination. Therefore, the exposure of individual groups of people in accidents, tests, etc. is taken into account in the above figures only in the form averaged for the entire population of the Earth.

Radiometers - designed to measure the flux density of radiation sources and the activity of radionuclides.

Spectrometers - to study the distribution of radiation by energies, charge, and masses of IR particles (that is, to analyze samples of any materials, IR sources).

Dosimeters - to measure doses, dose rates and intensity of ionizing radiation.

Among the listed there are universal devices that combine certain functions. There are instruments for measuring the activity of a substance (that is, the number of times / sec), instruments for registering alpha, beta and other radiation, etc. These are, as a rule, stationary installations.

There are special field, or search, instruments designed for searching, detecting radiation sources, assessing the background, etc., capable of recording gamma and beta radiation and assessing its level (roentgenometers, radiometers, etc.).

There are indicator devices designed only to get an answer to the question of whether or not there is radiation in a given place, often working on the "more - less" principle.

But, unfortunately, few devices are produced that belong to the class of dosimeters, that is, those that are specifically designed to measure the dose or dose rate.

There are even fewer universal dosimeters with which you can measure different types of radiation - alpha, beta, gamma.

The main domestic dosimeters have in their name the abbreviation "DRG" ​​- "X-ray-gamma dosimeter", can be portable or small-sized (pocket) and are designed to measure the dose rate of X-ray and gamma radiation. Therefore, detecting with their help and measuring the power of gamma radiation does not mean at all that there is alpha and beta radiation in this place. Conversely, the absence of X-ray and gamma radiation does not mean at all that there are no alpha and beta emitters.

The Ministry of Health of the USSR, by letter dated 01.09.87, No. 129-4 / 428-6, prohibited the use of geological prospecting devices of the SRP-68-01 type and other similar devices as dosimetric devices for measuring the exposure dose rate. To measure the magnitude of the exposure dose of gamma and X-ray radiation, only dosimeters of the DRG-3-01 (0.2; 03) type should be used; DRG-05; DRG-01; DRG-01T and their analogues.

But in any case, before using any device to measure the power or exposure dose, you should study the instructions and find out for what purpose it is intended. It may turn out that it is not suitable for dosimetric measurements. You should always pay attention to the units in which the device is calibrated.

In addition to these devices, there are also devices (devices, cassettes, sensors, etc.) for individual dosimetric control of persons directly working with sources of ionizing radiation.

The word "radiation" is more often understood as ionizing radiation associated with radioactive decay. In this case, a person experiences the action of non-ionizing types of radiation: electromagnetic and ultraviolet.

The main sources of radiation are:

• natural radioactive substances around and inside us - 73%;
• medical procedures (fluoroscopy and others) - 13%;
• cosmic radiation - 14%.

Of course, there are technogenic sources of pollution resulting from major accidents. These are the most dangerous events for humanity, because, as in a nuclear explosion, iodine (J-131), cesium (Cs-137) and strontium (mainly Sr-90) can be released. Weapon-grade plutonium (Pu-241) and its decay products are no less dangerous.

Also, do not forget that over the past 40 years the Earth's atmosphere has been very heavily contaminated with radioactive products of atomic and hydrogen bombs. Of course, at the moment, radioactive fallout falls only in connection with natural disasters, for example, during volcanic eruptions. But, on the other hand, the fission of a nuclear charge at the time of the explosion produces a radioactive isotope carbon-14 with a half-life of 5,730 years. The explosions changed the equilibrium content of carbon-14 in the atmosphere by 2.6%. At present, the average effective equivalent dose rate due to explosion products is about 1 mrem / year, which is approximately 1% of the dose rate due to the natural background radiation.

mos-rep.ru

Energy is another reason for the serious accumulation of radionuclides in humans and animals. The bituminous coals used in CHP plants contain naturally occurring radioactive elements such as potassium-40, uranium-238 and thorium-232. The annual dose in the area of ​​coal-fired CHP is 0.5–5 mrem / year. By the way, nuclear power plants are characterized by significantly lower emissions.

Almost all inhabitants of the Earth undergo medical procedures using sources of ionizing radiation. But this is a more difficult question, which we will return to a little later.

In what units is radiation measured

Different units are used to measure the amount of radiation energy. In medicine, sievert is the main one - an effective equivalent dose received in one procedure by the whole body. It is in sieverts per unit time that the background radiation level is measured. Becquerel serves as a unit for measuring the radioactivity of water, soil, and so on, per unit volume.

Other units of measurement can be found in the table.

Term	Units		Unit ratio	Definition
	SI	In the old system
Activity	Becquerel, Bq		1 Ci = 3.7 × 10 10 Bq	The number of radioactive decays per unit of time
Dose rate	Sievert per hour, Sv / h	X-ray per hour, R / h	1 μR / h = 0.01 μSv / h	Radiation level per unit of time
Absorbed dose		Radian, glad	1 rad = 0.01 Gy	The amount of ionizing radiation energy transferred to a specific object
Effective dose	Sievert, Sv		1 rem = 0.01 Sv	Radiation dose, taking into account different sensitivity of organs to radiation

Radiation consequences

Exposure to radiation on a person is called radiation. Its main manifestation is acute radiation sickness, which has varying degrees of severity. Radiation sickness can manifest itself with exposure to a dose equal to 1 sievert. A dose of 0.2 sievert increases the risk of cancer, and a dose of 3 sievert threatens the life of the exposed person.

Radiation sickness manifests itself in the following symptoms: loss of strength, diarrhea, nausea and vomiting; dry, hacking cough; cardiac disorders.

In addition, radiation causes radiation burns. Very large doses lead to the death of the skin, up to damage to muscles and bones, which heals much worse than chemical or thermal burns. Along with burns, metabolic disorders, infectious complications, radiation infertility, and radiation cataracts may appear.

The consequences of radiation can manifest themselves over a long time - this is the so-called stochastic effect. It is expressed in the fact that the frequency of certain cancers may increase among exposed people. In theory, genetic effects are also possible, but even among 78 thousand Japanese children who survived the atomic bombings of Hiroshima and Nagasaki, no increase in the number of hereditary diseases was found. And this is despite the fact that the effects of radiation have a stronger effect on dividing cells, therefore, radiation is much more dangerous for children than for adults.

Short-term low-dose irradiation, used for examinations and treatment of certain diseases, has an interesting effect called hormesis. This is the stimulation of any system of the body by external influences that are insufficient for the manifestation of harmful factors. This effect allows the body to mobilize strength.

Statistically, radiation can increase the level of oncology, but it is very difficult to identify the direct effect of radiation, separating it from the action of chemically harmful substances, viruses and others. It is known that after the bombing of Hiroshima, the first effects in the form of an increase in the incidence of diseases began to appear only after 10 years or more. Cancer of the thyroid gland, breast and certain parts is directly related to radiation.

chornobyl.in.ua

The natural background radiation is about 0.1–0.2 μSv / h. It is believed that a constant background level above 1.2 μSv / h is dangerous for humans (it is necessary to distinguish between an instantly absorbed radiation dose and a constant background). Is this a lot? For comparison: the radiation level at a distance of 20 km from the Japanese nuclear power plant "Fukushima-1" at the time of the accident exceeded the norm by 1,600 times. The maximum recorded radiation level at this distance is 161 μSv / h. After the explosion, the radiation level reached several thousand microsieverts per hour.

During a 2–3-hour flight over an ecologically clean area, a person receives radiation of 20–30 µSv. The same dose of radiation threatens if a person is made 10-15 pictures in one day with a modern X-ray apparatus - a visiograph. A couple of hours in front of a cathode ray monitor or TV gives the same dose of radiation as one such picture. The annual dose from smoking, one cigarette per day, is 2.7 mSv. One fluorography - 0.6 mSv, one radiography - 1.3 mSv, one fluoroscopy - 5 mSv. Radiation from concrete walls - up to 3 mSv per year.

When irradiating the whole body and for the first group of critical organs (heart, lungs, brain, pancreas and others), regulatory documents establish the maximum dose of 50,000 μSv (5 rem) per year.

Acute radiation sickness develops at a single exposure dose of 1,000,000 μSv (25,000 digital fluorographs, 1,000 x-ray images of the spine in one day). Large doses have an even stronger effect:

• 750,000 μSv - short-term insignificant change in blood composition;
• 1,000,000 μSv - mild radiation sickness;
• 4,500,000 μSv - severe radiation sickness (50% of those exposed to death die);
• about 7,000,000 μSv - death.

Are X-ray examinations dangerous?

Most often, we encounter radiation during medical research. However, the doses that we receive in the process are so small that we should not be afraid of them. The exposure time with an old X-ray apparatus is 0.5-1.2 seconds. And with a modern visiograph, everything happens 10 times faster: in 0.05–0.3 seconds.

According to the medical requirements set out in SanPiN 2.6.1.1192-03, during preventive medical X-ray procedures, the radiation dose should not exceed 1,000 μSv per year. How much is it in the pictures? Quite a bit of:

• 500 sighting images (2–3 µSv) obtained with a radiovisiograph;
• 100 of the same images, but using good X-ray film (10-15 µSv);
• 80 digital orthopantomograms (13-17 µSv);
• 40 film orthopantomograms (25-30 µSv);
• 20 computed tomograms (45-60 µSv).

That is, if every day, throughout the year, we take one picture on a visiograph, add to this a couple of computer tomograms and the same number of orthopantomograms, then even in this case we will not go beyond the permitted doses.

Who should not be irradiated

However, there are people for whom even such types of radiation are strictly prohibited. According to the standards approved in Russia (SanPiN 2.6.1.1192-03), radiation in the form of X-ray can be performed only in the second half of pregnancy, except for cases when the issue of abortion or the need for emergency or emergency care must be resolved.

Clause 7.18 of the document states: “X-ray examinations of pregnant women are carried out using all possible means and methods of protection so that the dose received by the fetus does not exceed 1 mSv in two months of undetected pregnancy. If the fetus receives a dose exceeding 100 mSv, the doctor is obliged to warn the patient about the possible consequences and recommend to terminate the pregnancy. "

Young people who are to become parents in the future need to close the abdominal region and genitals from radiation. X-ray radiation has the most negative effect on blood cells and germ cells. In children, in general, the whole body should be screened, except for the area under study, and studies should be carried out only if necessary and as prescribed by a doctor.

Sergei Nelyubin, head of the X-ray diagnostics department of the N.N. B. V. Petrovsky, Candidate of Medical Sciences, Associate Professor

How to protect yourself

There are three main methods of protection against X-rays: time protection, distance protection and shielding. That is, the less you are in the X-ray range and the farther you are from the radiation source, the lower the radiation dose.

Although a safe dose of radiation exposure is calculated for a year, it is still not worth doing several X-ray examinations on the same day, for example, fluorography, etc. Well, each patient must have a radiation passport (it is embedded in the medical card): in it, the radiologist enters information about the dose received during each examination.

Radiography primarily affects the endocrine glands, lungs. The same applies to small doses of radiation in accidents and releases of active substances. Therefore, as a preventive measure, doctors recommend breathing exercises. They will help cleanse the lungs and activate the body's reserves.

To normalize the internal processes of the body and remove harmful substances, it is worth consuming more antioxidants: vitamins A, C, E (red wine, grapes). Sour cream, cottage cheese, milk, grain bread, bran, unprocessed rice, and prunes are useful.

In the event that food products inspire certain concerns, you can use the recommendations for residents of the regions affected by the Chernobyl accident.

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With actual exposure due to an accident or in an infected area, quite a lot needs to be done. First you need to carry out decontamination: quickly and accurately remove clothes and shoes with carriers of radiation, properly dispose of it, or at least remove radioactive dust from your belongings and surrounding surfaces. It is enough to wash the body and clothes (separately) under running water using detergents.

Food supplements and anti-radiation drugs are used before or after exposure to radiation. The best known drugs are high in iodine, which helps to effectively fight the negative effects of its radioactive isotope, which is localized in the thyroid gland. To block the accumulation of radioactive cesium and prevent secondary damage, use "Potassium orotat". Calcium supplements deactivate the radioactive strontium preparation by 90%. Dimethyl sulfide is shown to protect cellular structures.

By the way, the well-known activated carbon can neutralize the effects of radiation. And the benefits of drinking vodka immediately after irradiation are not a myth at all. It really helps to remove radioactive isotopes from the body in the simplest cases.

Just do not forget: self-treatment should be carried out only if it is impossible to consult a doctor in a timely manner and only in the case of real, and not fictitious, radiation. X-ray diagnostics, watching TV or flying on an airplane do not affect the health of the average inhabitant of the Earth.

Modern man is constantly exposed to radiation. It is published by household appliances, fancy gadgets, power lines and other objects. Radiation is usually divided into two groups: non-ionizing and ionizing... The first group is considered safe for humans. It includes radio waves, heat, ultraviolet light. The danger is represented by the second group, to which radiation belongs. Why is this radiation so dangerous and what are the lethal doses of radiation for humans?

Where can you face radiation

Radiation pursues a person everywhere. The earth itself has a natural background radiation. It may differ depending on the region. The highest level of radiation in our country is observed in the Altai Territory... But even it is so small that it is considered completely safe. Much more dangerous are artificially created sources of ionizing radiation, which we encounter quite often:

1. X-ray equipment in hospitals. Every year we undergo fluorographic examination and are exposed to radiation. The dose of radiation in X-rays is small and with a single passage of such a procedure, no harm is caused to health.
2. Scanning devices at airports. They act in a similar way to a medical x-ray. The rays pass through the human body, so the radiation dose is extremely small.
3. Screens of old televisions equipped with cathode ray tubes.
4. Nuclear power plant reactors. This is the most powerful source. While he is in integrity, he is not particularly dangerous. But any damage to it threatens a global catastrophe.
5. Radioactive waste. If they are disposed of incorrectly, the environment can be contaminated with potential hazards.

The normal dose of radiation does not pose a great danger to human life or health.... If it is slightly exceeded, radiation sickness develops. If a person is exposed to a large dose of radiation, instant death occurs.

Radiation unit

Since 1979, a new unit for measuring the level of radiation has been introduced - sievert.... It can be designated Sv or Sv. One sievert is equivalent to the amount of energy absorbed by one kilogram of biological tissue. Earlier, the unit of measurement of radiation was considered to be rem. 1 sievert is equal to 100 rem.

Small doses of radiation are usually measured in millisieverts. One sievert equals one thousand millisieverts.

How is radiation measured

The radioactivity of the surrounding space directly affects the state of health. Even being at home, a person can be negatively affected. Apartments are especially dangerous if they contain dishes made of crane glass, finishing materials with the addition of granite, or old radiation paint. Under such circumstances, it is important to periodically measure the background radiation.

Special devices - radiometers or dosimeters - will help to identify the dangerous background. A dosimeter is used for operation in a residential area. With a radiometer, you can easily determine the background of food.

Today there are special organizations that provide services for the determination of radiation contamination. Experts will help identify and dispose of background sources.

You can also purchase a home dosimeter. But you cannot be 100% sure of the readings of such a device. When using it, you must strictly follow the instructions and avoid contact of the device with the objects under investigation. If indoor radiation levels are found to be unacceptable, you should seek professional help as soon as possible.

Human exposure to radiation

To understand the question of what dose of radiation is dangerous to humans, the table will help.

Radiation dose, Sv	Human exposure
Up to 0.05	Permissible radiation doses. With such an impact, negative consequences for human health are not observed.
0.05 to 0.2	The symptoms of radiation sickness do not appear. In the future, the likelihood of developing cancer, as well as genetic mutations in offspring, increases.
0.2 to 0.5	No negative symptoms are observed. The concentration of leukocytes in the blood decreases.
0.5 to 1	The first signs of radiation sickness appear. In men, the likelihood of infertility increases many times over.
1 to 2	Severe form of radiation sickness. Based on statistical data, 10% of people who received such a dose of radiation live no more than a month. In the first 10 days, the victim's condition is stable, after which there is a sharp deterioration in health.
2 to 3	The probability of death during the first month rises to 35%. The concentration of blood leukocytes drops to critical values.
3 to 6	The possibility of healing remains. About 60% of those injured die. The cause of death is the development of infectious diseases and internal bleeding.
6 to 10	The probability of death is 100%. It is impossible to recover in this case. Modern medicine manages to postpone death for a maximum of a year.
10 to 80	The person falls into a deep coma. Death occurs after half an hour.
Over 80	Death from radiation occurs instantly.

Radiation is considered safe if its power does not exceed 0.2 microsievert per hour.... The permissible dose of radiation for humans does not exceed 0.05 Sv. Exposure above this level leads to serious health consequences. An annual X-ray dose of 0.05 Sv is typical for people working at nuclear power plants in the absence of any emergency situations.

When carrying out local medical procedures, the maximum permissible human exposure dose is 0.3 Sv. The rate of X-ray exposure per year does not exceed two procedures.

The role is played not only by the radiation power, but also by the duration of exposure. An exposure that is low in strength and has an effect for a long time will be more detrimental to health than a short-term, strong exposure. But this is true only if we are not talking about lethal doses of radiation.

Radiation accumulation effect

Throughout life, the human body can accumulate from 100 to 700 microsieverts of radiation... Such an indicator is considered normal and does not threaten human health or life. At the same time, about 3 to 4 microsieverts can accumulate in the body per year.

The amount of accumulated radiation will largely depend on external circumstances. So, each X-ray in the dentist's office brings 0.2 microsievert, passage through the airport scanner - 0.001 mSv, fluorographic examination - 3 mSv.

When radiation sickness develops

The consequence of exposure to a critical dose of radiation on a person is the development of radiation sickness. It affects almost all body systems.... Depending on the dose, the radiation can be treatable or fatal.

According to recent studies, for the appearance of radiation sickness, the dangerous dose of radiation per year is 1.5 Sv. The maximum permissible dose of a single exposure is 0.5 Sv. After this mark, signs of defeat begin to appear.

The following forms of radiation sickness are distinguished:

1. Radiation injury. Appears if the dosage of a single radiation did not exceed 1 Sv.
2. Bone marrow form. Dangerous norms - from 1 to 6 Sv. In half of the cases, this form of the disease is fatal.
3. The gastrointestinal form is observed at a radiation dosage of 10 to 20 Sv. It is accompanied by internal bleeding, fever, the development of infectious lesions.
4. Vascular form. It develops after irradiation in the range from 20 to 80 Sv. Severe hemodynamic disturbances occur.
5. Cerebral form. Observed at irradiation above 80 Sv. Instant cerebral edema and death of the victim occurs.

In some cases, radiation sickness can develop into a chronic form. The period of its formation can take up to three years.... After this, the body is restored, which lasts another three years. With the right therapy, the result is a cure. But in some cases it is not possible to save the patient.

Symptoms of radiation sickness

If the normal dose of radiation was not exceeded critically, then symptoms of radiation injury appear. Among them are:

• Attacks of nausea and vomiting.
• Dry mucous surfaces of the nasopharynx.
• The taste of bitterness is felt in the mouth.
• Severe headaches appear.
• The victim quickly gets tired, his vitality leaves him.
• Blood pressure decreases.

In case of exceeding the radiation dose of 10 Sv, the following signs are observed:

• Redness of certain areas of the skin. Over time, they take on a blue tint.
• The frequency of contraction of the heart muscle changes.
• Reduced muscle tone.
• Tremors appear in the fingers.
• The tendon reflex disappears.

After four days, the pronounced symptoms disappear. The disease becomes latent. Its duration will depend on the degree of damage to the body. At the same time, all reflexes of the body are significantly reduced, symptoms of a neuralgic nature appear.

If the radiation dose exceeded 3 pollutants, then two weeks later, intense baldness begins.... At a dose above 10 Sv, the disease immediately enters the third phase. There is a serious change in the composition of the blood, infectious diseases develop. In the shortest possible time, cerebral edema sets in, muscle tone completely disappears. In the overwhelming majority of cases, a person dies.

At the first suspicious symptoms, you need to seek help from a doctor. Only with timely therapy is there a chance for a successful cure for radiation sickness.

Diagnostics

The onset of radiation sickness is detected on the basis of primary signs. Close attention is paid to patients who have been in a situation where the safe dose of radiation is exceeded.

The severity of the lesion is determined by examining the victim's blood samples. The presence of anemia, reticulocytopenia, leukopenia, ESR is determined. The presence of radiation sickness is indicated by signs of bleeding in the myelogram..

In addition to the study of blood, the following diagnostic measures are carried out:

1. Collection of scrapings of skin ulcers and microscopy.
2. Ultrasound of the abdominal cavity.
3. Ultrasound of the pelvic organs.

At the same time, consultations are held with narrow specialists: hematologist, endocrinologist, neuropathologist and gastroenterologist. They carefully study the clinical picture of the disease and the results of all examinations.

Radiation sickness therapy

The disease is successfully treated if the dose threshold of infection is slightly exceeded... Among the main therapeutic techniques are:

1. Timely first aid. This is especially important for people who have been in a place of strong radiation contamination. All clothing is removed from the victim, as it accumulates radiation in itself. Thoroughly wash the body and stomach.
2. Drug therapy. It includes the use of sedatives, antihistamines, antibiotics, remedies for the restoration of the gastrointestinal tract. In addition, treatment is carried out aimed at restoring the immune system. In the third stage of the disease, antihemorrhagic drugs are prescribed, among other things.
3. Blood transfusion.
4. Physiotherapy. The most commonly used breathing is with an oxygen mask.
5. In some cases, specialists perform a bone marrow transplant.
6. Proper nutrition. First of all, an optimal drinking regime is organized. The victim should drink at least two liters of water per day. His diet should also include juices and tea. At the same time, you cannot drink at the same time with meals. The use of fatty, fried and overly salty foods is minimized. There should be at least five meals a day. The use of alcoholic beverages is strictly prohibited.

Preventive actions

In order not to become a victim of radiation cure, you must adhere to the following recommendations:

1. Avoid Potentially Hazardous Areas... At the slightest suspicion that the maximum dose of radiation is on the territory, you should immediately leave this place and contact a specialist.
2. People employed in hazardous industries are advised to use vitamin and mineral complexes, as well as other drugs that support the immune system. The choice of specific medications should be made in conjunction with the attending physician.
3. In contact with radioactive objects, it is necessary to use specialized protective equipment: suits, respirators, and so on.
4. Drink as much water as possible. Fluid helps flush radioactive substances out of the body.

The lethal dose of radiation in sieverts is only 6 units. Therefore, at the first suspicion of an increased background, it is necessary to conduct a study using a dosimeter.