Автор работы: Пользователь скрыл имя, 16 Мая 2014 в 08:47, реферат
Ecology is a science, which studies the relationship between all forms of life on our planet and our environment. This word came from the Greek «oikos» which means «home». All living things are related to their environment. The Earth is our common home and we must take care of it.
Since ancient times Nature has provided Man with everything he needed: food to eat, water to drink, wood for building and fuel for heating and cooking. For hundreds of years Man used Nature’s sources and it seemed to people that the resources of Nature had no end.
With the industrial revolution our negative influence on Nature began to increase. Big smoky cities with thousands of people, polluting plants and factories can be found nowadays all over the world.
Introduction……………………………………….Page 1
Main Part (2 - 20):
Air pollution………………………………..….Page 2 - 9
Water pollution…..…………………………..Page 9 - 11
Deforestation..………………………...……Page 12 – 13
Nuclear energy……………………………...Page 13 - 20
Conclusion……………………………………….Page 20
New words and phrases…………...………..Page 21 – 23
My sources……………………………...……….Page 24
Radiation treatments are widely used in medicine to help cure patients with some kinds of cancer. Doses of 5,000 rems are common. Much smaller doses of radioactive materials are used as diagnostic tools. The health effects of these levels of radiation help us more than they hurt us.
From all sources, a usual person receives an average exposure to radiation of about 360 millirems per year. Most of this comes from the natural radiation in soil, water, rocks, building materials, and food. For example, potassium is a common, naturally occurring radioactive element found in many foods.
Radiation exposure from all commercial nuclear energy power plants has averaged 0.01 millirem per person annually. Those who live near a nuclear power plant receive less than 5 millirems per year. The federal limit for people who work in nuclear power plants is a maximum of 5,000 millirems per year. Utilities themselves normally have set their own limits even lower than that.
The guiding principle for releases from nuclear power plants is ALARA, As Low As Reasonably Achievable. Plant operators pay continuous, careful attention to assure themselves and the public that any radiation releases are well below the levels of significant environmental or human health effects. These levels are set by law and are based on data collected for more than 50 years. The current exposure level is 5 millirems per year at the plant boundary.
It is impossible to operate a nuclear plant with absolutely no release of radioactivity. The releases are normally not critical as far as human health is concerned, and, in fact, contain fewer radioactivities than the releases from comparable coal-fired plants.
The amount of radioactivity released by a nuclear power plant is monitored continuously to be sure it doesn't go above allowed levels. This same monitoring equipment provides exact information about any accidental release. More monitoring equipment and personnel are on hand for emergency use. Teams practice environmental/radiation monitoring several times a year in emergency drills with independent governmental agency personnel, who also practice and participate.
The greatest potential hazard from an operating nuclear power plant is from the radioactive products created in the fuel. These come from the fission process that generates the heat to make electricity. Plants are designed to keep these fission products inside the plant.
Every operating plant has plans in place to alert and advise the residents as necessary in and emergency. These are local government plans and are practiced each year with local civil authorities. These plans often have been used for emergencies that have had nothing to do with a nuclear plant. Such plans have never had to be used to evacuate the public in a nuclear plant emergency.
Before any nuclear plant can be built and go into service, the utility must obtain many different licenses and operating permits from federal, state and local agencies. The Nuclear Regulatory Commission requires that its conditions be met and allows for public hearings to be held before the Commission issues a construction permit. After construction is done, the NRC issues an operating license, again after a public hearing. During and after construction, the Commission stations full-time inspectors at the plant. Other visiting inspectors are sent to do on-site inspections. This assures that the plant is operated according to its license.
Each utility checks its plants for radioactive releases. The records are sent to and examined by the Nuclear Regulatory Commission and the Environmental Protection Agency. Abnormal conditions or operations are reported to these agencies.
Nuclear waste
Since the first commercial nuclear power plant began producing electricity in 1957, the total amount of accumulated spent fuel (classified as high-level waste) is 9000 tons. For comparison, the Environmental Protection Agency reported that in 1982, 46 million tons of poisonous waste (that is, not nuclear) were disposed of. In comparison the amount of nuclear waste is very small.
Nuclear wastes are, for the same power output, some 3.5 million times smaller in volume than the wastes from coal plants. High-level nuclear wastes can be disposed of by diluting them with twice their own volume of neutral materials as they are changed into glass or ceramic form. The reprocessed waste volume form a 1,000 megawatt nuclear power plant would fit easily under a typical dining room table. A coal plant of the same capacity (1,000 megawatts) produces some 10 tons of waste per minute.
After changing it to stable form, the volume of all nuclear waste produced until the year 2000 (including low-level waste from the entire U.S nuclear power industry) would fit into a cube 250 feet on each side. The high-level waste portion would fit into a cube 50 feet on each side within the 250-foot block.
Most low-level wastes are solidified, put into drums and buried at a commercial disposal site. There they are placed at the bottom of trenches (about 20 feet deep). At the Barnwell, SC, site, for example, trenches are back filled with sand and covered in clay each day to keep moisture from getting in. When full, trenches are mounded and capped with clay, and finished off with a foot of topsoil. Grass is planted to help prevent erosion. The collection, transportation and burial of low-level radioactive wastes are all closely monitored and controlled by the Department of Transportation and the Nuclear Regulatory Commission.
When properly managed, these low-level wastes do not pose a hazard. The industry now has 30 years of experience in handling and shipping these materials. There never has been an accident with these wastes that had serious health results due to radioactivity.
The 1980 Low-Level Waste Policy Act makes each state responsible for providing he disposal of its own waste. Also encouraged are joint efforts among several states for a shared site.
Conclusion
In this report I tried to show how does the activity of a Man influences on our common home. I have shown different kinds of pollution (I mean water and air pollutions) and the consequences of wasting our environment (for example, global warming, acid rains, greenhouse effect and etc.).
I suppose that our main problem is the following: we try to solve ecological problems because it became hard to live with poisoned air and water, but not because of their respect to the planet they live on and to the birds and animals they live with. People try to take care of the planet just because of their egoism.
If we want to live on the clean Earth at least we should remember about ecological culture. Ecological culture means respect of the nature not only as our home, but also as a home of millions of species of insects, animals and birds.
Sites in Internet, which I have visited to write this report:
Books:
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