Influence of radioactive substances on flora and fauna. OBZhD

BASICS OF SAFE LIFE
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Influence of radioactive substances on flora and fauna. Basics of safe life

Fundamentals of Safe Life Activities (OBZhD)

Some chemical elements radioactive: the process of their spontaneous decay with transformation into elements with other serial numbers is accompanied by radiation. As a radioactive substance decays, its mass decreases over time. Theoretically, the entire mass of a radioactive element disappears in an infinitely long time. The half-life is the time after which the mass is halved. Varying over a wide range, the half-life is, for different radioactive substances, from several hours to billions of years.

The fight against radioactive contamination of the environment can only be of a preventive nature, since there are no methods of biological decomposition and other mechanisms that can neutralize this type of contamination of the natural environment. The greatest danger is posed by radioactive substances with a half-life of several weeks to several years: this time is sufficient for the penetration of such substances into the body of plants and animals.

Spreading along the food chain (from plants to animals), radioactive substances enter the body along with food and can accumulate in quantities that can harm human health.

The most dangerous among radioactive substances - 90Sr and 137Cs - are formed during nuclear explosions in the atmosphere, and also enter the environment with waste from the nuclear industry. Due to its chemical similarity with calcium, 90Sr easily penetrates into the bone tissue of vertebrates, while 137Cs accumulates in muscles.

The radiation of radioactive substances has a detrimental effect on the body due to a weakening of the immune system, a decrease in resistance to infections. The result is a decrease in life expectancy, a reduction in natural population growth rates due to temporary or complete sterilization. Damage to genes was noted, while the consequences appear only in subsequent - second or third - generations.

The severity of the consequences of exposure depends on the amount of energy absorbed by the body, emitted by the radioactive substance (radiation). The unit of this energy is 1 rad - this is the radiation dose at which 1 g of living matter absorbs 10-5 J of energy.

It has been established that at a dose exceeding 1000 rad, death occurs; in the case of a dose of 100 rad, a person survives, but the likelihood of oncological disease, as well as complete sterilization, increases significantly.

The greatest pollution due to radioactive decay was caused by explosions of atomic and hydrogen bombs, the testing of which was especially widely carried out in 1954-1962.

The second source of radioactive impurities is the nuclear industry. Impurities enter the environment during the extraction and enrichment of fossil raw materials, their use in reactors, and the processing of nuclear fuel in installations.

The most serious pollution of the environment is associated with the operation of plants for the enrichment and processing of nuclear raw materials. For the decontamination of radioactive waste to its complete safety, a time equal to about 20 half-lives is required (this is about 640 years for 137Cs and 490 thousand years for 239Ru). It is hardly possible to vouch for the tightness of containers in which waste is stored for such a long time.

Thus, the storage of nuclear waste is the most acute problem of protecting the environment from radioactive contamination. Theoretically, however, it is possible to create nuclear power plants with practically zero emissions of radioactive impurities. But in this case, the production of energy at a nuclear power plant is significantly more expensive than at a thermal power plant.

Since the production of energy based on fossil fuels (coal, oil, gas) is also accompanied by environmental pollution, and the reserves of such fuels are limited, most researchers involved in energy and environmental issues have come to the conclusion that nuclear energy can not only meet the growing needs of society in energy, but also to ensure the protection of the natural environment and humans better than can be done by producing the same amount of energy based on chemical sources (burning hydrocarbons). At the same time, special attention should be paid to measures that eliminate the risk of radioactive contamination of the environment (including in the distant future), in particular, it is necessary to ensure the independence of emission control authorities from the departments responsible for the production of atomic energy.

Maximum allowable doses of ionizing radiation have been established based on the following requirement: the dose should not exceed twice the average dose of radiation to which a person is exposed under natural conditions. It is assumed that people have adapted well to the natural radioactivity of the environment. The total dose of ionizing radiation that comes to each person on average, created by the radioactive background, is approximately 3-5 rad over 30 years.

Groups of people are known who live in areas with high radioactivity, much higher than the average on our planet (for example, in one of the regions of Brazil, residents receive about 1600 mrad per year, which is 10-20 times more than the average radiation dose).

On average, the dose of ionizing radiation received per year by each inhabitant of the planet ranges between 50 and 200 mrad. The consequences of the Chernobyl accident still affect the lives of millions of citizens of Russia, Ukraine and Belarus, and international assistance in solving the long-term problems caused by it remains urgently needed. This was stated in the UN report "Consequences of the nuclear accident at the Chernobyl nuclear power plant for human life - a recovery strategy."

As a result of the Chernobyl accident, 23% of the territory of Belarus, 5% of the territory of Ukraine and 1,5% of the territory of Russia were exposed to radioactive contamination. The level of radioactive contamination of these territories in some places significantly exceeds the natural radioactivity of the environment. At least 8000 people died from radiation-related illnesses in these countries. Approximately 2 cases of thyroid cancer have been diagnosed. About 000 people continue to live in areas with high levels of radioactive contamination. At the same time, focality of zones of radioactive contamination is noted, i.e., areas with a high level of radioactivity are adjacent to uncontaminated areas.

Authors: Aizman R.I., Krivoshchekov S.G.

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