Lecture
Radiation has always been present in nature, and living organisms have constantly been exposed to a certain amount of radiation coming both from natural sources (soil, food) and from cosmic rays.
Radio waves of various lengths, light and radiant heat from the Sun are one of the varieties of radiation, however it is not ionizing, since it is not capable of breaking the chemical bonds of the molecules of living organisms, causing biologically significant changes.
Today nuclear power plants generate 18.4% of all electricity, while in individual countries this share is considerably higher. Thus, among the developed countries, nuclear energy's share of electricity supply is 75% in France, 46.6% in Belgium, 46% in Sweden, 36% in Japan and 19.7% in the USA. In Russia, 29 power units of nuclear power plants are in operation.
The operation of nuclear power facilities is associated with a minor radiation impact, however possible accidents (as is known, more than 150 accidents have occurred in 14 countries of the world), as well as test explosions of nuclear weapons in the atmosphere, which continued from 1954 to 1963, contaminated a significant part of the planet with radioactive substances. The accident that occurred in April 1986 at the Chernobyl nuclear power plant, unprecedented in complexity and scale of consequences, led to radioactive contamination of parts of the territories of 17 regions of Russia, and radioactive fallout reached Austria, Germany, Italy, Norway, Sweden, Poland, Romania, and Finland.
NATURAL RADIATION BACKGROUND
1 - Cosmic rays
Cosmic rays mainly come from the depths of the Universe, but some part of them is born on the Sun during solar flares. Cosmic rays can be a source of primary cosmic radiation, and upon reaching the Earth's surface or interacting with its atmosphere, they give rise to secondary radiation, leading to the formation of various radionuclides.
Primary galactic radiation can change its flux density due to fluctuations in the Earth's magnetic field and the 11-year cycle of solar activity, which cause deflection of the radiation on its way to the Earth's surface and thereby weaken the radiation. The intensity of primary radiation can increase by a factor of 100 or more during solar flares.
High-energy particles of primary cosmic radiation, entering the atmosphere and interacting with the nuclei of air atoms, form
secondary cosmic radiation: neutrons, protons.
Higher levels of radiation are observed at the North and South Poles compared to the equatorial region, owing to the magnetic field which deflects charged particles (of which cosmic rays mainly consist). It must also be emphasized that the level of exposure increases with altitude, since there is less and less air remaining to serve as a protective shield. Thus, the population living in Tehran or Mexico City, located at an altitude of 4 km above sea level, receives annual effective doses due to cosmic radiation that are 2-3 times greater than for the population living at sea level. Naturally, the duration of exposure also affects the dose received. Thus, on a flight from New-York to Paris a passenger of an ordinary turbojet aircraft receives a dose of about 50 microsieverts, while a passenger of a supersonic aircraft, owing to the shorter flight time, receives a dose 20% lower, even though subjected to more intense radiation. In total, through the use of air
transport, humanity receives an effective collective dose per year of
2 - Terrestrial radiation
Radionuclides of terrestrial origin make the greatest contribution to the exposure dose from natural sources. Th ese include 32 nuclides that are part of radioactive families. Of the radionuclides representing the uranium and thorium families, the most important from an ecological-hygienic standpoint are the following. These radionuclides are distributed throughout all environmental objects. In certain quantities they are always present in the human body.
The main contribution to the radioactivity of rocks is made by radionuclides of the uranium-radium (U) and thorium (Th) families.
The natural radioactivity of soils depends, first of all, on the radioactivity of the parent rocks. Here, gray-brown soils have the highest radioactivity, while peat bogs have the lowest.
Surface and groundwater can be of substantial significance as a source of background human exposure.
A significant content of K is found in surface and underground fresh waters, however it is lower than in the water of seas and oceans. Of underground waters, those confined to acidic igneous rocks have the highest radioactivity, while those confined to sedimentary rocks have the lowest. The latter are more often used for municipal water supply purposes.
Intensive leaching of radionuclides from the thickness of rocks leads to the formation of radioactive waters in some areas.
The radioactivity of sea water is determined mainly by the content of K, and in the open seas and oceans it reaches 13 Bq/l (1300 Bq/m3). The organic part of the silt of open water bodies contains a large amount of K, which accounts for its high radioactivity compared with soils.
3 - Internal exposure
Approximately 2/3 of the effective (equivalent) exposure dose that a person receives from natural sources of radiation comes from radioactive substances that enter the body with air, water, and food. Here, the main part comes from sources of terrestrial origin, and a small part comes from radioactive isotopes such as C of carbon and tritium, which are formed under the influence of cosmic radiation.
On average, a person receives about 180 microsieverts per year owing to K, which is absorbed by the body together with non-radioactive isotopes of potassium necessary for the body's vital functions. However, a person receives a considerably larger dose of internal exposure from nuclides of the U radioactive series and, to a lesser extent, from radionuclides of the Th series.
The main contribution to the radioactivity of plant and animal organisms is made by K.
The most significant of all natural sources of radiation is the invisible, tasteless and odorless gas — radon.
Radon
A person receives the greater part of this dose from radionuclides that enter the body with inhaled air.
Rn is a radioactive gas, 7.5 times heavier than air, formed in the chain of radioactive decay of U.
A person receives the main part of the exposure dose from radon and its decay products while indoors, in an unventilated room. In an enclosed space the concentration of radon is on average 8 times greater than in outdoor air. Radon enters a room and accumulates in it by seeping through the foundation and floor from the soil, or by being released from building materials (walls, ceiling). A high radon content is observed in buildings standing on soil with a high radium content. A serious danger to humans is posed by the entry of water vapor with a high radon content into the lungs together with inhaled air, which is most often observed while in the bathroom.
TECHNOLOGICALLY MODIFIED NATURAL RADIATION BACKGROUND
The technogenic background is constantly increasing owing to the industrialization of countries, in the course of which natural radionuclides extracted from the depths of the Earth together with coal, ore, oil, gas, mineral fertilizers, thermal waters, etc. have begun to enter the natural environment in large quantities.
1. The main sources of the technogenic background are building materials, to which waste from the mining of various ores or coal ash is added, the coal fuel cycle itself, as well as the mining and agricultural use of fertilizers for soils.
2. One of the materials whose use leads to an increase in the natural radiation background is coal. During the mining and burning of coal, and the use of coal ash for building materials, radionuclides are redistributed from the depths of the earth into the biosphere, which causes an increase in the exposure of the population.
In some countries more than 1/3 of the resulting ash is used as an additive to cements, asphalts and concretes. The latter sometimes consists of 50% ash dust. The use of ash as an additive to building materials, as well as its application in large quantities to soil, leads to an increase in the radiation background.
Less coal is spent on heating homes and cooking than on power plants, but owing to the imperfection of the technology more ash dust per unit of fuel is released into the atmosphere, so that the expected effective collective exposure dose of the population from heating homes with coal is significantly greater than as a result of the operation of power plants.
The use of oil at power plants also leads to the concentration of U, Th, K radionuclides. An even smaller radiation hazard is posed by the production and use of natural gas.
The mining and use of phosphate ores also causes an increase in the technologically enhanced natural radiation background.
ARTIFICIAL RADIATION BACKGROUND
1 - Nuclear weapons
The periods of the most intensive testing of this weapon were 1954-1958 (USA, Great Britain, USSR) and 1961-1962 (USSR, USA), when weapons with a total yield of 513 megatons of TNT equivalent were detonated. After 1963, tests in the atmosphere and underwater in the USSR and USA were discontinued; several series of atmospheric tests up until 1981 were conducted by France and China. Underground testing of nuclear weapons continues to this day, but they, as a rule, take place under conditions that exclude radioactive fallout and environmental contamination.
By the mid-1980s — the peak of the nuclear arms race — the two superpowers — the USSR and the USA — had accumulated gigantic arsenals of atomic and thermonuclear weapons: about 18 billion tons in TNT equivalent (A.M. Ryabchikov, 1987), which amounted to more than 3 tons for every inhabitant of the planet. At the height of the most acute confrontation the number of nuclear warheads reached 56,400, with the yield of each one being on average 25 times greater than the bomb dropped on Hiroshima (about 13 kt). Taking into account the amount of nuclear weapons of three other powers (France, England and China), the total number of warheads amounted to about 60 thousand.
According to experts' calculations, the explosive power of the accumulated nuclear weapons exceeded the explosive power of all munitions used during the Second World War (about 7 million tons), as well as the combat operations in Korea and Vietnam (more than 10 million tons) combined, by more than 1000 times. During these wars, as is known, 44 million people died. It is now recognized that three countries (the USA, Russia and China) possess the capability of repeated mutual assured destruction.
Nuclear weapons testing: scale and environmental consequences.
From UN materials it is known that from 1945 to the end of 1987, 1741 nuclear tests were carried out on our planet, of which 899 explosions were conducted by the USA (according to other data — 919), 620 — by the USSR, 151 — by France, 41 — by England and 30 — by the PRC. By 1989, 1880 explosions had already been carried out. At the same time, the total yield of nuclear explosions produced only in the USA was equal to 11,050 atomic bombs dropped on Hiroshima (V.V. Dovgusha et al., 1995). The USSR in 1962 tested a super-powerful 52-megaton bomb at the Novaya Zemlya test site. Recall that the total amount of explosives used during the years of the Second World War amounted to about 7 megatons.
Over the course of almost 40 years of nuclear testing, an accumulation of radionuclides occurred on Earth. 12.5 tons of fission products were released into the biosphere (the explosion of the atomic bomb over Hiroshima released about 1 kg of fission products). The explosions changed the equilibrium content in the atmosphere of carbon 14C (with a half-life of 5730 years) by 2.6%, and of the radioactive isotope tritium (with a half-life of 12.3 years) — by almost 100 times.
Radioactive radiation at the Earth's surface reached 2% above the natural background by 1963.
2 - Nuclear power plants
In the Russian Federation there are 29 power units. In central Russia (the Central and Central Black Earth economic regions) there are currently four nuclear power plants. The total capacity of their nuclear power installations is about 11 MW.
It should be noted that, compared with power plants using other types of fuel, nuclear power plants have a number of environmental advantages. They preserve living space for the population, whereas around coal-fired power plants hundreds of hectares are occupied by ash dumps of harmful coal dust; for the operation of hydroelectric power plants, fertile floodplain meadows are flooded for reservoirs, and the use of wind power sources, accompanied by intense acoustic vibrations, scares away all living creatures for kilometers around.
It has been established that the influence of nuclear power plants on the radioactive contamination of soils is insignificant and incomparable with its natural level of radioactivity. It has been shown that the ash dumps of coal-fired power stations create a radiation background 5-40 times higher than the emissions of nuclear power plants.
At the same time, it must be taken into account that the thermal emissions of nuclear power plants are 1.5 times greater than at thermal power plants, and this often leads to a deterioration of the ecological situation both in cooling reservoirs and in nearby natural bodies of water and groundwater.
The atmospheric emissions of nuclear power plants contain such radionuclides as radioactive noble gases (xenon, krypton),
Accidents at radiation facilities.
No matter how advanced modern military equipment may be, no matter what control and safety systems are put in place, accidents and disasters cannot be excluded. According to sources, over the past 40 years there have been at least 130 serious accidents involving American bombers and missiles alone, in which there was a probability of a nuclear or even thermonuclear explosion. As a result of accidents and disasters involving Soviet and Russian nuclear submarines from 1968 to 2000, 7 nuclear power units ended up in the World Ocean. In total, according to the American magazine «Time», at the bottom of the World Ocean there are 7 sunken nuclear submarines of various national affiliations, 10 nuclear reactors and 50 nuclear (atomic and hydrogen) munitions.
According to Japanese research, as a result of corrosion in sea water a hydrogen bomb that the Americans lost in the Pacific Ocean has already «begun to leak». Increased radioactivity has also been detected in the area where the sunken US nuclear submarines «Thresher» and «Scorpion» lie.
To emphasize the importance of measures aimed at preventing accidents at radiation-hazardous facilities, academician V. Kotlov (1997) points out that there are 34 thousand such facilities in the Russian Federation. Of these, 29 are nuclear power units, 113 are research reactors, critical and subcritical assemblies with nuclear materials, 245 are nuclear submarines, most of which have been decommissioned, 12 are nuclear surface vessels, thousands of tons of spent nuclear fuel, and 3 billion curies of temporarily buried radioactive waste.
The Chernobyl disaster: a tragic experience and a warning. A serious warning to humanity was the disaster that occurred at the Chernobyl nuclear power plant on April 26, 1986, and caused irreparable damage both to many people and to the development of the domestic nuclear power industry.
During scheduled tests, the reactor of the fourth power unit, loaded with 180 tons of radioactive fuel, lost control, which led to an explosion and the release of about 50 tons of fuel into the atmosphere. It evaporated and formed a huge atmospheric reservoir of long-lived radionuclides. Another about 70 tons of fuel was thrown out beyond the reactor from peripheral sections of the core by the lateral rays of the explosion. In addition to the fuel, the explosion also threw out about 700 tons of radioactive reactor graphite. About 50 tons of nuclear fuel and 800 tons of graphite remained in the destroyed reactor. Owing to the high temperature in it, the graphite burned out in the following days and thereby contributed to an increase in the amount of radioactive fallout. Let us note, for comparison, that the total mass of radioactive substances formed as a result of the bomb explosion over Hiroshima was only 4.5 tons. At the same time, 600 times more long-lived and therefore especially dangerous radionuclides entered the biosphere than after the 1945 nuclear explosion.
According to available data, the consequences of the disaster turned out to be extremely severe. During the accident itself 2 people died, 29 died later from acute radiation sickness, about 150 thousand people were evacuated from the 30-kilometer zone adjacent to the power plant. Residence and economic activity are prohibited in this zone.
The fuel ejected from the reactor, in the form of finely dispersed particles of uranium dioxide and highly active radionuclides of Iodine-131, plutonium-239, neptunium-139, cesium-137, strontium-90 and other radioactive isotopes, caused contamination of many regions. The regions of Gomel, Mogilev, Bryansk, Kiev and Zhitomir were most severely affected.
Scientists believe that the consequences of the disaster, above all with respect to human health, will manifest themselves to the greatest extent 10 years after the explosion, i.e. at the end of the 20th century. Its traces in the human genetic apparatus will not disappear earlier than after forty generations, i.e. almost 1000 years. Forecasts are now being refined.
A great danger to human health is posed by the selective accumulation of radionuclides in various parts of the body. Thus, strontium-90, which readily accumulates in grasses, passes into the body of, for example, a cow, and then, with its milk, enters the human body. In the event of its accumulation in the bone marrow, leukemia or bone tumors develop. Cesium-137, being less soluble, enters the body together with plant food and accumulates in the liver or in the gonads. The latter circumstance can lead to the occurrence of hereditary changes.
The quantity and volumes of medium- and low-level radioactive waste are extremely large. It is assumed that by the year 2000, about 1.5 million m3 will have accumulated in Russia, and about 3.6 million m3 in the USA.
Almost 98.5% of the nuclear fuel of nuclear power plants goes into waste, representing radioactive fission products (plutonium, cesium, strontium, etc.), which cannot be destroyed, but can only be stored forever in special storage facilities.
Even more dangerous consequences occur in cases of disasters and accidents at nuclear facilities and enterprises.
A major accident occurred in 1957 in the Chelyabinsk region at a radiochemical plant for reprocessing nuclear fuel and extracting plutonium for nuclear bombs. This plant had been discharging radioactive waste into open bodies of water since 1949, in particular, 120 million curies (1 Ci=3.7·1010 Bq) entered Lake Karachay, which is twice as much as as a result of the Chernobyl disaster.
Subsequently, concrete containers with a stainless steel coating were made for liquid radioactive waste. However, it was precisely in these that an explosion occurred with the release of 2 million curies. The cloud passed to the north, leaving a radioactive trail 105 km long and up to 8 km wide. 17 thousand residents were resettled from the contaminated zone. Elimination of the trail is still being carried out to this day.
In the system of the Ministry of Defense of the Russian Federation, the problem of neutralizing radioactive waste, which is formed in the process of operation and repair, as well as as a result of the decommissioning of first- and second-generation nuclear submarines, has become very acute. Already now, for example, about 90 nuclear submarines with reactors that have outlived their service life have accumulated in the Northern Fleet. In total, in the five nuclear fleets of the world (USA, Russia, China, England and France), 190 reactors were expected to be decommissioned in 1990—1995. With a scheduled cooling period for reactor cores of up to 5—6 years, some installations have been in this mode for 7 to 14 years. At the same time, experts note that the Navy lacks storage facilities for radioactive waste, and the existing ones are far from being in the best condition.
Disposal and decontamination of radioactive waste:
Radioactive waste dumps in the seas, including Russian ones, arose following the appearance of a nuclear fleet in a number of countries. Discharges of radioactive waste, which began as early as 1959, continued systematically until 1992 in certain areas of the Baltic, Barents, White, Kara, Okhotsk and Japan Seas, as well as in the coastal waters of the Novaya Zemlya archipelago and the Kamchatka Peninsula.
According to summary data (V.V. Dovgusha, 1995), in the period from 1964 to 1991, 4900 containers with solid low- and medium-activity radioactive waste were sunk in the northern seas. Off the eastern shores of Russia, in the Sea of Japan and the Sea of Okhotsk, 6868 containers with medium- and low-activity solid radioactive waste were buried during 1986—2000, as well as 38 vessels and more than 100 large-sized objects. Their total activity is estimated by experts at 22.2 thousand curies. Over 30 years of operation of the nuclear fleet, about 100 thousand m3 of liquid radioactive waste with an activity of more than 24 thousand curies entered the ecosystems of the northern seas.
The total amount of radioactive waste dumped into the sea by the USA in 1946—1970 alone amounted to more than 86 thousand containers with a total radioactivity of about 95 thousand curies. In 1971—1983, radioactive waste from military and civilian nuclear industry enterprises was regularly dumped into the sea by Belgium, England, the Netherlands and Switzerland, and occasionally by France, Italy, West Germany, Sweden, Japan, and South Korea. It has been calculated that in total, over 1967—1992, 94,603 tons of radioactive waste, placed in 188,188 containers, with a total activity of more than 1 million curies, ended up in the Atlantic Ocean.
To date, the following radioactive waste disposal technologies have been developed (K.M. Sytnik et al.):
1) for large quantities of highly active radioactive waste — concentration and subsequent storage (by means of vitrification, concreting and storage in deep shafts); 2) for small quantities of highly active radioactive waste — extraction of long-lived isotopes with high toxicity before disposal of the residual activity;
3) for waste of medium activity — storage until the decay of short-lived isotopes is achieved and subsequent dispersal in one medium or another:
4) for relatively small quantities of low-activity waste — dilution (for example, with water) and subsequent dispersal.
1. Disposal in isolated form (in capsules). The technology consists of converting radioactive waste into a glass-like state (by pouring in liquid glass), mixing it with cement, or enclosing the vitrified mass in corrosion-resistant containers capable of withstanding great external pressure. After this they are dumped at great depths. The British seal the waste in barrels and dump it into the sea. In Russia, so-called water lenses are usually used for disposal. Into them, in liquid form, not only radioactive strontium and cesium are pumped, but also plutonium-239, whose half-life is 24 thousand years. If the integrity of the lens is breached over these millennia, the consequences will be catastrophic.
Disposal of low-activity radioactive waste in a pre-diluted form. In order for the radioactivity of waste entering the marine environment to decrease rapidly, its discharge is recommended to be carried out while the vessel is moving and preferably behind the propeller. Russian legislation now prohibits such disposal.
3. Long-term storage of highly active radioactive waste. Storage of highly active liquid waste (usually these are aqueous nitric acid solutions) is carried out in double-bottomed stainless steel tanks with a volume ranging from several tens to several hundred cubic meters. They are installed in concrete chambers, and in order to prevent a possible explosion of accumulating hydrogen, the tank is continuously purged with air. The exhaust air is subsequently cleaned of radioactive aerosols in special filters.
The contents of some tanks are constantly stirred, since the precipitation of solid particles, for example of plutonium or uranium, could lead to the accumulation of a critical mass and, consequently, initiate a nuclear explosion. The precipitation of radioactive salts of another nature can also contribute to a sharp rise in temperature and likewise cause an explosion, but a thermal one, with the release of radioactivity into the environment.
A modern storage facility for highly radioactive waste consists of vertical shafts, horizontal drifts (corridors) and the actual burial chambers themselves, constructed, for example, in salt formations at a depth of about 600 m. Boreholes are drilled in the floor of the chamber for storing canisters with solutions of high specific activity waste (HSAW). A distance of 10 to 50 m must be maintained between the boreholes. The reason for such spacing of the canisters from one another is their strong heat release; a disruption of the latter regime could lead to a disaster.
4. In the West (USA, France), several projects for long-term HSAW storage facilities were developed, including rather exotic ones. One of them involves launching heavy rockets loaded with highly active waste towards the Sun, with their subsequent destruction. However, it should be remembered that, according to statistics, up to 2% of rocket launches end in accidents within the atmosphere. Such a disaster would naturally result in the most severe consequences, comparable to Chernobyl. In the USA, a lengthy discussion and search for sites for two grandiose radioactive waste storage facilities for a period of up to 10 thousand years is under way. They will be located at a depth of 300—1000 m in places not subject to earthquakes. The cost of this project is estimated at 27 billion dollars.
On the territory of Russia, the total activity of unburied radioactive waste, according to some estimates, exceeds 4 billion Ci. Russia has 15 disposal sites, waste disposal centers (Chelyabinsk-65, Krasnoyarsk-26).
Accidents involving the release of radioactive substances, which occurred at the «Mayak» production association in the north of the Chelyabinsk region, led to the formation under Lake Karachay of a «lens» of radioactive brines, which is moving in the direction of the Techa River at a speed of 80 m per year. If these salts get into water bodies, a significant territory of Western Siberia and then the Arctic Ocean could be contaminated. A similar situation has developed in the Ob basin in the Tomsk region as a result of the activities of the Siberian Chemical Combine.
Radioactive waste with a moderate radioactivity of almost 2.5 MCi was dumped in the Kara Sea, which allows the Kara Sea to be considered a potentially dangerous region of the World Ocean. The published data prompted more detailed research.
According to Russian legislation, waste generated in the process of reprocessing foreign spent nuclear fuel must be sent back — to the country from which it came. This is a powerful deterrent factor for any country wishing to get rid of this type of highly active waste, as well as for commercial activity.
THE RADIATION SITUATION in our country
Radioactive contamination of the surface layer of the atmosphere
Outside the territories contaminated as a result of the Chernobyl accident, the average concentrations in the air of radionuclides such as cesium-137 and strontium-90 amounted to, respectively, 6.04·10-7
The content of radionuclides in atmospheric fallout in the contaminated territories of the European part of Russia also significantly exceeded the national average by a factor of 10.
In areas located within the zone of influence of the "Mayak" production association in the Southern Urals, fallout of cesium-137 from the atmosphere during 1994 was 50-100 times greater than the national average.
Radioactive contamination of terrain
1. In the European part of Russia — these are territories contaminated as a result of the accident at the Chernobyl nuclear power plant, where the main radionuclide is cesium-137.
2. In the Southern Urals — these are the areas adjoining the "Mayak" production association, and the East Ural Radioactive Trace, formed as a result of the accident at this enterprise in 1957 and as a result of the wind dispersal of radioactive aerosols from the dried-up technological reservoir No. 9 of the "Mayak" production association (Lake Karachay) in 1967.
3. On the territory subjected to radioactive fallout as a result of the accident at the Siberian Chemical Combine (SCC).
Radioactive contamination of water systems
1. In the waters of rivers flowing through the contaminated territories of the European part of Russia, elevated concentrations of cesium-137 and strontium-90 were observed.
2. In the Southern Urals, in the Techa River, into which liquid radioactive effluents of the "Mayak" production association were discharged in the 1940s-1950s, the concentrations of strontium-90 in the river water exceeded background levels by 100-1000 times.
3. Levels of contamination of sea water with strontium-90 also did not change compared with 1993. In the waters of the Caspian, Okhotsk, Kara and Barents Seas, as well as in the waters of the Pacific Ocean washing the shores of Kamchatka, the concentration of strontium-90 fluctuated within the range of (0.03-0.6)·10-12 Ci/l.
Radioactive waste
Enterprises of Minatom of Russia, at which radiochemical production is concentrated (the "Mayak" production association, the Siberian Chemical Combine, the Mining and Chemical Combine), continue to remain potential sources of radioactive contamination of adjacent territories. In the course of their operation, a large amount of liquid and solid radioactive waste has accumulated, whose total activity reaches 1.5 billion Ci. Of particular concern is the concentration of medium- and low-level liquid waste in open reservoirs—storage facilities for radioactive waste at these enterprises. Lake Karachay, which until recently served as a receiver for medium-level waste, contains about 120 million Ci of activity, mainly due to strontium-90 and cesium-137. In the cascade of industrial reservoirs created in the floodplain part of the upper reaches of the Techa River after the cessation of discharges of radiochemical production waste into it, 350 million m3 of contaminated water has accumulated, which is essentially low-level waste with a total activity of about 200 thousand Ci. The presence of surface reservoirs storing liquid waste leads to the penetration of radioactive substances into groundwater and underground water. Under Lake Karachay, a lens of contaminated groundwater has formed with a volume of about 4 million m3 and an area of up to 10 km2. The rate of spatial movement of the contaminated groundwater reaches 80 m/year. There is a possibility of this water penetrating into other aquifer structures and carrying radionuclides into the hydrographic network.
At present, 140 thousand m3 of liquid waste with a total activity of 29 thousand Ci, 8 thousand m3 of solidified waste with an activity of 2 thousand Ci, and 120 thousand m3 of solid waste (equipment, construction debris) are stored at the country's 29 nuclear power plant units.
To date, about 200 thousand m3 of waste with a total activity of about 2 million Ci has accumulated in the storage facilities of the sites.
To date, 121 nuclear submarines have been decommissioned (Northern Fleet - 70, Pacific Fleet - 51), and the cores have been unloaded from 42 nuclear submarines (Northern Fleet - 18, Pacific Fleet - 24). In most cases, the spent fuel has been in the reactors for 15 years or more.
Among the decommissioned nuclear submarines are 4 boats with damaged reactors, for which methods of disposal have not yet been developed.
The spent nuclear fuel storage facilities of the Murmansk Shipping Company (the floating technical bases "Lotta", "Lepse" and "Imandra"), the coastal and floating spent nuclear fuel storage facilities of the Navy — 4 coastal technical bases (CTB) and 9 floating ones (FTB) — are fully loaded.
The effect of low doses of radiation on children's health.
Exposure to various types of ionizing radiation in high doses causes somatic effects in the irradiated individual and genetic effects in offspring. Somatic effects are divided into early — non-stochastic — and late — stochastic. Non-stochastic effects include the development of acute and chronic radiation sickness, local radiation lesions (radiation cataracts, burns), and functional and morphological changes in organs and systems. Stochastic effects include the development of leukemia, neoplasms of various localization, and congenital pathology caused by the teratogenic effect of radiation on the fetus.
Non-stochastic effects. Exposure to low doses of radiation does not cause acute or chronic radiation sickness, nor local radiation lesions. The effect of subthreshold doses on the functional state and morphology of organs largely depends on the magnitude of the dose. At doses close to the threshold (50—100 rem of total exposure), the following somatic effects are possible.
1. In the musculoskeletal system there is a slowdown in growth, depending on the age at the time of exposure (sensitivity to radiation is inversely proportional to the age of the child).
2. Heart: it is also a radioresistant organ, unlike the vascular system, which reacts to radiation exposure by developing vegetative-vascular dystonia syndrome, associated with increased excitability of the higher autonomic parts of the nervous system, causing changes in the neurohumoral mechanisms of hemodynamic regulation.
3. Morphological changes in the CNS, as a rule, are not noted, but a slowdown in the maturation of the higher parts of the brain is possible, which has a negative effect on the child's mental development.
4. The gastrointestinal tract is one of the first to be affected upon exposure to a dose above 100 rem, but practically does not suffer from subthreshold radiation exposure.
5. The most radiosensitive elements of the body are hematopoietic cells. With a single exposure to a dose of 50—100 rem, mildly pronounced changes in the hemogram may occur (a decrease in the number of platelets, leukocytes, erythrocytes). With chronic exposure to a total dose of 50—100 rem, the development of increasing neutropenia, lymphocytopenia, thrombocytopenia, and less often anemia is possible.
6. Total exposure of up to 100 rem does not cause changes in the activity of the endocrine glands. Local exposure of the thyroid gland to a dose of 30—200 rem can cause functional changes, and doses above 200 rem — such diseases as nodular goiter, autoimmune thyroiditis, acquired hypothyroidism, and thyroid cancer.
At the same time, various deviations in health status are found in children. Their direct connection with radioactive exposure has not currently been established. Most children exhibit various diseases: chronic tonsillitis, chronic inflammatory diseases of the gastrointestinal tract (chronic gastroduodenitis, chronic cholecystocholangitis), multiple caries, thyroid gland hyperplasia of grade I—II without impairment of its function, and disorders of the autonomic nervous system (vegetative-vascular dystonia, asthenovegetative syndrome). Young children are characterized by the presence of rickets, paratrophy, and allergic dermatoses.
Stochastic effects. An increase in the number of oncological diseases (and, accordingly, their manifestations in clinical practice) is possible 2—4 years after exposure. Leukemias are one of the most characteristic radiation-induced stochastic effects. No clear dependence has been noted of an increase in the frequency of leukemias associated with radiation exposure among children living near nuclear production facilities and testing grounds, or among adult participants in nuclear tests. Among children irradiated during intrauterine development in Hiroshima and Nagasaki, no increased tendency to cancer has been found either. At the same time, there is a risk of an increase in cases of leukemia in children whose fathers work in nuclear production facilities. There is currently no increase in leukemias or solid tumors in children from radioactively contaminated areas.
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