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Emergencies at radiation hazardous facilities. Fundamentals of safe life

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Radioactive substances (RS) and sources of ionizing radiation are used in everyday life, production, and medicine. For example, nuclear reactors provide up to 13% of Russia's electricity needs. They set in motion turbines, ships; ensure the operation of a number of space objects. This is quality control of seams in casting in mechanical engineering, and medical examinations, and point irradiation, but, in addition, this is a weapon of enormous destructive power that can destroy civilization.

The nuclear fuel cycle (NFC) can be divided into stages:

• mining of uranium ore and extraction (enrichment) of uranium from it;
• use of nuclear fuel in reactors;
• RV transportation;
• chemical regeneration of spent nuclear fuel;
• purification of spent nuclear fuel from radioactive (RA) waste;
• safe ("perpetual") storage of RA waste and impurities;
• removal of uranium and plutonium from spent nuclear fuel for use in nuclear power engineering.

The result of mining and crushing of uranium ore, enrichment of uranium are mountains of production, which:

• create a dangerous ecological situation;
• take large land areas out of circulation;
• change the hydrology of the territory;
• lead to long-term RD of soil, atmosphere and water.

The low content of uranium-235 in the mined ore (0,7%) does not allow its use in nuclear energy: enrichment of this ore is required, that is, an increase in the content of uranium-235 using very complex and expensive equipment, and significant energy costs. Enrichment is possible after the separation of isotopes of uranium-233, uranium-235, uranium-238 at the atomic level.

Natural uranium is supplied to the market in the form of uranium oxide (compressed yellow-brown powder), while enriched uranium is supplied in the form of tablets of uranium oxide or gaseous uranium hexafluoride (in steel cylinders).

At uranium mining sites, the bulk of the dumps are mountains of fine sand mixed with natural radionuclides, which mainly emit RA gas radon-222 (which gives α radiation), which increases the likelihood of lung cancer. By 1982, about 175 million tons of such sand had accumulated in the United States with radiation below the standard. To date, thousands of houses, schools and other buildings made from these materials have been demolished.

The total reserves of uranium on Earth are about 15 million tons. Deposits with reserves of up to 2,7 million tons are being developed. The former USSR accounted for up to 45% of the world's uranium reserves, distributed almost evenly between Russia, Uzbekistan and Kazakhstan.

A radiation hazardous facility (RAHO) is a MA where, as a result of an accident, massive radiation releases or damage to living organisms and plants can occur.

Types of RAOO:

• NPP is an OE for the production of electricity using a nuclear reactor, equipment and trained personnel (Fig. 5.1);
• ACT (Nuclear Heat Supply Plant) is a MA for the production of thermal energy using a reactor, equipment and trained personnel;
• PNFC (Nuclear Fuel Cycle Enterprise) is an OE for the manufacture of nuclear fuel, its processing, transportation and waste disposal.

In a nuclear reaction, up to 99% of the nuclear fuel goes into the RA waste (plutonium, strontium, cesium, cobalt), which cannot be destroyed, therefore it must be stored. Contacts with nuclear fuel, its waste, energy carriers, fuel elements (TVEL) and other RA products lead to the protection of buildings, equipment, and transport. If special treatment does not reduce their level of infection below the MPC (MPC), then they also require burial.

The nuclear reactor is the main part of the nuclear power plant and nuclear engines. It is a large boiler for heating the coolant (water, gas). The heat source is a controlled nuclear reaction. It must be borne in mind that 0,5 g of nuclear fuel is equivalent to 15 wagons of coal for energy production, which, moreover, when burned, releases a huge amount of carcinogenic substances into the atmosphere.

Enriched nuclear fuel is placed in the reactor core in the form of a regular lattice of bundles of fuel elements (approximately 700 pieces). TVEL is a rod with a diameter of 10 mm, a length of 4 m, with a zirconium sheath, constantly washed by water. Water acts as a cooler and absorber of neutrons (if "heavy water" is used, then it only slows down neutrons, but does not absorb them, that is, in this case, natural uranium can be used. This type of reactor uses only 1% of the released energy).

There are nuclear reactors on slow and fast neutrons. Slow neutron reactors can be cooled with ordinary water, such as, for example, RBMK - high-power reactor, channel; VVER - pressurized water reactor, or "heavy" water or gas, such as HTGR - high-temperature helium-cooled reactor. Fast neutron reactors are called breeder reactors (R-R). If VVER uses 5% of nuclear fuel, then a fast neutron reactor, for example BN-600, uses up to 55%.

The operation of the reactor, that is, the movement of the rods in the core relative to the substance that absorbs neutrons, is controlled by an operator or an automatic system.

The reactor (Fig. 5.2) has two water circuits. In the primary circuit (where a pressure of 7 kPa is provided), water remains in a liquid state even at a temperature of 330 ° C and, passing through a heat exchanger (steam generator), gives off heat to the water of the second circuit. The first and second circuits of the reactor are reliably isolated from each other. In the second circuit of the reactor, water is in a vapor state, since the pressure here is atmospheric. This steam drives a turbine generator that generates electricity.

In a helium-cooled reactor (HTGR), graphite blocks are used to moderate neutrons, and carbon dioxide or helium at a temperature of 70 ° C is used as a coolant (these gases do not allow metal corrosion). The heat is transferred through the heat exchanger to the second circuit, where the steam temperature reaches 540°C.

Rice. 5.1. The principle of the nuclear power plant: 1 - turbine; 2 - alternator; 3 - concrete protection; 4 - capacitor; 5 - circulation pump; 6 - uranium rods; 7 - reactor; 8 - gamma radiation coming from the active zone; 9 - moderator; 10 - control rods; 11 - coolant; 12 - steam generator

Rice. 5.2. The principle of operation of a nuclear reactor

For an emergency shutdown of the reactor, its core can be filled with water with a neutron absorber (boron, or a hydrogen-containing substance other than water) from a special reservoir without operator intervention. Such water does not mix with the working coolant in the normal mode, and "suppresses" the reactor only in the event of a sharp development of the accident. (In normal mode, pipes with water are submerged to a certain depth. With the appearance of steam in them, the pipes float, which increases the productivity of the pumps. If the pumps are not able to cope with the jamming, then the reactor core is flooded with a composition from the emergency special reservoir: the reactor is "killed".) The probability of damage to the health of NPP personnel per year is 5x10-⁶ from cancer and 10'⁶ from radiation sickness.

To ensure protection, the nuclear power plant has appropriate security, mechanical obstacles, electronic burglar alarms, electrical self-sufficiency. In order to keep up with the world community, Russia must develop its nuclear power industry. Prospects for the development of nuclear power plants in Russia are shown in Table. 5.1.

Table 5.1. Planning for the commissioning of NPP units

To obtain a controlled thermonuclear reaction, scientists went in several ways. One of them led to the creation of a tokamak, the other - to the scheme of the reactor with an "open" trap. In 1968, the tokamak shocked the world with promising results, and the main funds began to be invested in this direction. But supporters of the second way consider their scheme to be preferable: it is much easier to make the core of a reactor with an open trap (its vacuum chamber can be machined on a lathe); such reactors are easier to repair (they do not require disassembly, like round tokamaks); on the basis of an open trap, it is easier to create a new generation of reactors (neutronless, radioactively safe). Scientists from Akademgorodok in Novosibirsk demonstrated the GOL-3 installations - a 12-meter trap where the plasma is heated by an electron beam, and AMBAL-M, which keeps the plasma in the longitudinal direction due to the electrostatic potential. In February 1967, the world's first orbital thermionic nuclear power plant "Topaz" ("Thermionic experimental converter in the active zone") was launched into space, in which the energy of nuclear decay is directly converted into electric current. And in July 1987, the second such installation was launched into space, which worked there for more than a year. "Topaz" was created by the work of scientists from the Physics and Energy Institute (IPPE) in Obninsk.

A feature of a fast neutron nuclear reactor (RR) is its ability to produce more nuclear fuel than it consumes. In this case, the uranium-238 rods are placed in the breeding zone (enclosing the active zone in a ring). Here, due to the impact of neutrons, some of the U-238 atoms are converted into Pu-239 atoms. If this mixture (U-238 and Pu-239) is placed in the core, then its "burning" will result in "weapon-grade" plutonium, since natural uranium will be enriched. These cycles can be repeated several times and get 40 times more electricity than in a slow neutron reactor. In addition, RR has a significantly higher efficiency compared to a slow neutron reactor. It uses nuclear fuel more efficiently, generates less RA waste, and operates at lower pressure, which means it is less likely to depressurize ("leak"). But it also has a serious drawback: the impact of fast neutrons causes a “weakening” of the metal (steel swells and becomes brittle). R-R are "omnivorous": only they are capable of processing any nuclear fuel and waste, destroying plutonium released during disarmament.

One of the main leaders in the development of fast neutron reactors is IPPE (Obninsk). His experimental reactor BR-10 has long been a serious competitor to the famous tokamak. IPPE has the world's largest stand for research in the field of nuclear energy.

The world's first industrial R-R was built in Shevchenko. It was BN-350, and since 1980 Beloyarsk NPP has been operating BN-600. Now it is the only reactor in the world capable of converting weapons-grade plutonium into electricity. In 1994, it was planned to start up the first of three planned BN-800s at the South Ural NPP.

The experience of operating nuclear power plants has shown that pressurized water bypass reactors are the most dangerous - due to "leaks" as a result of defects in the material used in construction, at the junctions, in the cooling system, due to corrosion in the steam generator, and personnel errors. The tightness of the rods can be broken, as well as their overheating, as a result of which the hydrogen released from the water can explode. The rupture of the reactor is not ruled out due to the enormous pressure of the resulting water vapor with the release of RA of the products of a nuclear reaction. The waste stored at NPPs in the liquid state of the Republic of Armenia is also a serious danger, since the guaranteed service life of concrete tanks is 40 years, and at many NPPs it is close to the end. RA waste is thousands of times more harmful than uranium ore, since it is the smallest dust that is carried by the slightest wind over vast areas, infecting them for hundreds of years and creating a high level of radiation there.

Specialized storages are used for waste storage. One reactor with a capacity of 1000 MW annually converts 30 tons of uranium fuel into RA waste. 21 tons of used fuel elements are annually removed from 300 nuclear power plants in Germany. In 1986, the United States stored more than 12 tons of spent fuel elements, and by 000, up to 2000 tons are expected.

There are many ways to dispose of RA waste, but absolutely reliable has not yet been found. Only recently they refused to pump liquid RA waste into deep wells (many artesian wells were damaged). We have to refuse their flooding in the seas of the Pacific, Atlantic and Arctic oceans. Safety is also not ensured in special storage facilities (burial grounds, special polygons), built even with a strictly defined soil horizon and representing a very complex engineering complex. Containers with RA waste are sealed. Burial grounds require the alienation of a vast territory. They also contain RA waste from organizations. Waste from VR-400 reactors is sent for processing to extract uranium or plutonium, which is returned to the nuclear fuel cycle. Residue from regeneration is stored vitrified in concrete storages.

Sending RA waste into the depths of space is also not an option: the accident of any rocket during launch into orbit will lead to the dispersal of plutonium, the lethal dose of which is 0,01 g. No less dangerous are "peaceful" nuclear explosions for the construction of gas and oil storage facilities, the creation of lakes, river turns.

In addition to fires and explosions, the main damaging factor in an accident at a radwaste is radioactive contamination. Radioactive substances are odorless, colorless, tasteless, and are not captured by the senses. Radiation is the result of a change in the structure of the atom, the property of atomic nuclei to spontaneously decay due to internal instability and cause ionization of the medium.

There are several types of radiation arising from the decay of nuclei:

α-particles - flow of helium nuclei. Their charge is +2, their mass is 4, that is, for the microcosm it is a very heavy particle that quickly finds a target. After a series of collisions, the alpha particle loses energy and is captured by some atom. Their interaction is similar to the collision of billiard balls or electric charges. External exposure from such particles is insignificant, but they are extremely dangerous if they enter the body.

β-particles - the flow of electrons (positrons), their charge is -1 (or +1), and the mass is 7,5 thousand times less than that of an α-particle. It is more difficult for a β-particle to find a target in an irradiated medium, since it affects mainly only its electric charge. In this case, external irradiation is not large ((3-particles are retained by window glass).

γ-radiation - It is high frequency electromagnetic radiation. Since it is impossible to provide complete protection against it, screens made of materials capable of attenuating the radiation flux are used. If the material attenuates the flow by a factor of 2, then it is said to have a half attenuation factor. It is this ratio that is used in practice.

Protons and proton-neutron pairs act on the irradiated medium similarly to alpha particles.

Neutrons - these particles, which do not have a charge, but, having a huge mass, are capable of causing irreparable harm when the body is irradiated. They interact only with the nuclei of atoms (the process is similar to the collision of two billiard balls). As a result of several such collisions, the neutron loses energy and is captured by one of the nuclei of the irradiated substance.

Damage to the body due to exposure to ionizing radiation depends on the energy that radioactive radiation (RAI) transfers to the body. This is taken as the basis for their measurement. Consider the most common of these units.

A rad is a dose unit of RAI at which a gram of a living organism absorbed 100 ergs of energy. The SI unit of absorbed dose is one gray (Gy), at which each kilogram of irradiated matter absorbs one joule of energy, that is, 1 Gy corresponds to 100 rads. Since it is difficult to measure the absorbed dose, another unit is often used - the roentgen.

Roentgen is an off-system unit of exposure (radiated) dose. It is determined by the action of RAI on air (it turned out to be the equivalent of living tissue in this case), which leads to ionization, that is, the appearance of an electric charge, which is recorded using measuring instruments. The exposure dose characterizes the potential danger of exposure to AI in the case of a general uniform irradiation of the human body. 1 x-ray - the dose of x-ray or gamma radiation at which 1 cm³ dry air at a temperature of 0°C and a pressure of 760 mm Hg. Art. created 2,08x10⁹ pairs of ions carrying one electrostatic unit of the amount of electricity of each sign. In the SI system, exposure dose is measured in coulombs per kilogram (C/kg). In this case, one roentgen is equal to 2,58-10^-4 C/kg.

The degree of RH of an area is characterized by the level of radiation (dose rate) at a given point in time, which is measured in R/h or rad/h. So, a radiation dose of 400 rad in 1 hour will lead to severe radiation injury, and the same dose received over several years will give a curable disease, that is, the intensity of radiation plays a huge role. Radiation damage to the body depends on the density of the radiation flux and its energy (hardness). Due to the decay of radiation products, over time, a decrease in the level of radiation occurs, which obeys the decay law RA:

P_t = P₀ (t/t₀)^-1.2

where P₀ - the level of radiation at the time of the accident or explosion t; P_t - the level of radiation at a given time t.

The amount of radioactive substances is judged not by weight, but by its activity, that is, the number of decaying nuclei of a substance per unit time. The unit of measurement is 1 act of decay per second, in the SI system it is a becquerel (Bq). The non-systemic unit of measurement of activity is 1 curie (Ci) - the activity of such an amount of RV in which 37 billion acts of decay of atomic nuclei occur per second, that is, 1 Ci \u3,7d 10 * XNUMX¹⁰ Bq. Since the number of RA atoms decreases with time, the activity of RV also decreases, that is

C_t = C₀e^-λt = C₀e^-0,693t/T

where C_t - RV activity after a given time t; C₀ - activity of the substance at the initial moment t₀; λ and T - decay constant and half-life of RS.

The considered units of RAI reflect the energy side of the issue, but do not take into account the biological impact of RAI on the body. The type of irradiation and the energy of the particles dramatically change the picture! Knowing the absorbed dose is not enough, you need to know the changes that will occur in the body due to exposure to radiation, that is, the biological consequences of radiation. Ionization of biological tissue leads to the breaking of molecular bonds and to a change in the chemical structure of its compounds. Changes in the chemical composition of many molecules lead to cell death. Radiation splits the water in the tissues into H (atomic hydrogen) and OH (hydroxyl group). As a result of the reaction, H₂O₂ (hydrogen peroxide) and a number of other products. All of them have high chemical activity, and reactions of oxidation, reduction and combination of some molecules with other tissue molecules begin to occur in the body. This leads to the formation of chemical compounds that are not characteristic of the living tissue of the body, which includes its immune system.

All this causes disturbances in the normal course of biological processes in the body. It is enough to know the coefficient of biological hazard of this type of RAI in order to determine the dose received by the body. For this, the rem unit was introduced - the biological equivalent of the rad, which differs from the dose of gamma radiation by the value of the quality factor (QC). It is sometimes referred to as the RBE (Relative Biological Efficiency) of a given type and intensity of radiation. Gamma radiation is taken as a unit of equivalent, since for this case there is a reference source and a measurement technique has been worked out. The QC value for different radiations is determined from the reference book.

Some of these ratios are:

• x-ray, gamma, beta radiation 1;
• thermal neutrons 3;
• fast neutrons, protons 10;
• alpha particles, recoil nuclei 20.

The complexity of removing RS from the body is exacerbated by the fact that different RS are absorbed differently by the body. RA sodium, potassium, cesium are almost evenly distributed over organs and tissues; radium, strontium, phosphorus accumulate in the bones; ruthenium, polonium - in the liver, kidneys, spleen, and iodine-131 accumulates exclusively in the thyroid gland - the most important organ of internal secretion, which regulates metabolism, growth and development of the body. The thyroid gland absorbs all the iodine that has entered the body until it is completely saturated. The accumulation of RA iodine in it leads to a disorder of the hormonal status of the thyroid gland. Such saturation is especially dangerous in children, since the thyroid gland plays a more important role in their lives than in adults. That is why before irradiation and during its first hours, to protect the thyroid gland, it is necessary to provide the body with an excess of neutral iodine. After receiving a dose of radiation from RA iodine, an acute hormonal disorder can develop in this gland; in extreme cases, complete destruction of the thyroid gland is observed.

Man has always been exposed to natural radiation. Its value - depending on the locality - varies from 100 mrem to 1,2 rem per year. The average value in the Russian Federation is 300 mrem per year, and in its central region the radiation background is 10...30 mkrem/h. Attenuated by the atmosphere, radiation comes from space, rises from the earth, it is emitted by granite buildings and chemical elements in the human body. The higher the flight altitude, the thinner the protective layer of the atmosphere (when flying at an altitude of 13 km, a person receives a radiation dose of 1 mR / h, and if there are spots on the sun, this dose increases). There are territories where the total dose of radiation bursting from the bowels of the earth is higher than in the Chernobyl zone, and its main share (up to 70%) is radon. It is born in the RA families of uranium and thorium, and the decay products of the elements of this series are present everywhere (in stones, concrete, soil, water). Approximate distribution of radon concentration in an apartment (Bq/m³): from building materials - 6,4; from domestic gas - 0,3; from air from the street - 5; from the soil under the building - 41,7; from water - 0,1. Several million RA atoms of radon enter our lungs every minute, causing painful symptoms. It has long been noticed that in some areas and even individual houses, the percentage of malignant diseases is much higher. If the radiation in the room air is above 200 Bq/m³, then it is necessary to take measures to seal the premises from radiation from underground.

Irradiation can lead to biological changes in the body, and this disease itself is called radiation sickness. Radiation sickness is a complex reaction of the body to the amount and intensity of absorbed energy: it is important what kind of radiation it was, what parts and organs of the body were affected, what kind of radiation occurred - internal or external, whether the bone marrow, the main hematopoietic organ, was affected.

Constant exposure to low doses (even with incomplete decontamination) can cause a chronic form of radiation sickness or negative consequences in a later period of life. The same result is caused by the ingestion of RV into the body through the respiratory organs, wounds, burns, with food, liquids. This form of radiation sickness is curable, but it is necessary to stop irradiation. The acute form of radiation sickness is characterized by the data in Table. 5.2.

The guiding documents in matters of AI standardization are the "Radiation Safety Standards NRB-96" and "Basic Sanitary Rules for Working withRV and III OSP-72/87 ". The determining factor here is the maximum permissible dose (MAD) - the annual level of exposure that does not cause adverse changes in the health status of the exposed person and his offspring with uniform exposure for 50 years.

Categories of exposed persons:

• category "A" - personnel having contact with RV or AI;
• category "B" - the rest of the population.

SDA for external and internal exposure are different for different groups of critical organs and tissues [46, 47]. Persons over 18 years of age are allowed to work with RS and IRS, while the accumulated exposure dose for persons of category "A" of a specific age is determined by the formula D \u5d 18 (N-5) (rem), where N is age in years. The genetically significant radiation dose received by the population as a whole from all sources should not exceed 30 rem per person for XNUMX years.

Table 5.2. Characteristics of the main forms of radiation sickness

The average annual allowable concentration of RS in the body, water and air is the maximum allowable amount of the RA isotope per unit volume or mass, upon receipt of which by natural means the body does not receive radiation doses exceeding the permissible limits.

When working with RVs, they may contaminate working surfaces and the bodies of workers, which can become a source of internal or external exposure. The MPC for contamination of the skin and surfaces of objects is established by sanitary norms (rules) based on the experience of working with RS and is measured by the number of particles emitted per unit area per minute. This determines the decision to take protection and evacuation measures (Tables 5.3, 5.4).

Table 5.3. Criteria for making a decision on the RA load (mSv)

Note. Temporary PDU RZ (particles/min*m²): skin, underwear - 10; outerwear, shoes, the inner surface of objects and objects - 100; internal surfaces of service premises, transport - 200; external surfaces of vehicles - 400.

The need for resettlement is dictated by the fact that it is impossible to obtain "clean" products, process them and sell them. The material accumulated to date shows that with a single irradiation of the whole body with a dose of 25 rem, no changes in the state of health and blood (which primarily responds to irradiation) are observed. When receiving a single dose of 25 ... 50 rem, temporary changes in the blood can be observed, which quickly normalize. When irradiated with a dose of 50 ... 100 rem, weak signs of radiation sickness of the first degree may appear without loss of working capacity, and 10% of those irradiated may vomit. Soon their condition will return to normal.

Based on the experimental material, it can be considered that the recovery rate after radiation injury per day reaches 2,5% of the accumulated dose, and the irreversible part of the injury is 10% (i.e., 40 days after exposure, the residual dose is 10%, not zero). Example: a person received a dose of 200 rem, then after 40 days he has a residual dose of 20 rem. After 50 days, he again received a dose of 200 rem, that is, he has 220 rem. To assess the effect of prolonged exposure, the concept of "effective dose" (which takes into account the result of the recovery effect) is introduced. It is less than the total dose received for the entire period.

It is believed that the reaction of the body to irradiation can manifest itself in the long term (after 10 ... 20 years). These are leukemias, tumors, cataracts, skin lesions, which are not always associated with radiation exposure. The same diseases can be the result of other harmful factors of a non-radiation nature. An analysis of the data (the results of the nuclear bombing of Japan, radiation therapy) shows that long-term effects are observed when exposed to a relatively large dose of radiation (at a dose of more than 70 rem, the risk of lung cancer increases, at a dose of more than 100 rem - leukemia).

Table 5.4. Criteria for making a decision on resettlement in case of RD, Ci/km²

It is impossible to detect a change in the state of health in people undergoing X-ray examinations (irradiation), in which the dose is hundreds of times greater than the natural background (with fluoroscopy of the stomach up to 3 rem, lungs - up to 0,2 rem, shoulder - up to 1 rem).

Components of the natural RA background:

• cosmic radiation (protons, alpha, beta particles);
• PA radiation from soil;
• radiation of radioactive substances that have entered the body with air, food, water.

Background from human activities:

• fluoroscopy and other medical procedures give up to 200 mR / year;
• one-time examinations - from 0,4 to 7 R;
• thermal emissions (coal combustion) - 0,2 mR/year.

Characteristics of accidents at RAOO and their prevention. Nuclear power plants are considered RAOO of the first degree of danger, and research institutes with nuclear reactors and stands - of the second degree of danger. To determine the danger of radioactive waste, a seven-point scale of the IAEA (International Atomic Energy Agency) has been developed.

Phases of the accident at the RAOO:

Early - from the beginning of the accident to the cessation of the release of radioactive substances and the end of the formation of a trace of radioactive substances on the ground (depending on specific weather conditions, it can be in the form of "spots"). The duration of the phase is up to two weeks. There is a high probability of external exposure from gamma radiation and beta particles, as well as internal exposure through food, water, air.

Medium - from the end of the early phase to the adoption of protective measures by the population. The duration of the phase is several years. In this case, the source of external irradiation are radioactive substances that have settled on the ground. It is not excluded and internal exposure through food, air.

Late - until the termination of protective measures and the lifting of all restrictions.

The degree of radiation hazard depends on many factors: the degree of hazard of radioactive waste, the type of nuclear reactor, the probable amount of products (radionuclides) in the release, the wind rose (the prevailing wind directions), the developed measures to prevent and eliminate the consequences of accidents at radioactive waste, as well as the ability of civil defense forces to timely carry out these activities. It is necessary to distinguish between the danger caused by "short-lived" radionuclides (RA iodine-131) and "long-lived" (strontium, cesium). This is taken into account whenonionization of the territory around the RAOO.

1st zone - the zone of emergency protection measures - the territory in which the dose of external exposure to the whole body does not exceed 75 rem, and internal exposure - 250 rem. This is a 30-kilometer zone around the nuclear power plant.

2nd zone - preventive measures - the territory in which the dose of external irradiation of the whole body does not exceed 25 rem, and internal (and especially the thyroid gland) - 90 rem.

3rd zone - the zone of restrictions - the territory in which the dose of external exposure to the whole body does not exceed 10 rem, and internal exposure - 30 rem.

If an external exposure dose of more than 10 rem is expected on the territory for a year, then it is necessary to introduce appropriate radiation protection regimes, and evacuate people from the 30-kilometer zone around the nuclear power plant (possibly, their subsequent return after assessing the actual situation).

Measures to prevent accidents:

• fulfillment of all requirements at the stages of design, construction and modernization of existing RAOO;
• the strictest control over the safety of operation of the RAOO by the state and international organizations;
• strict compliance with safety requirements at all stages of radwaste operation;
• high-quality training of RAOO personnel, regular professional development;
• systematic training of RAOO service personnel on special stands and simulators;
• readiness of protective equipment, security systems, RSChS, civil defense formations to work in the foci of damage within the prescribed period.

Authors: Grinin A.S., Novikov V.N.

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