21-11-2012, 02:34 PM
Nuclear hazards
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Nuclear hazards
Nuclear energy can be both beneficial and harmful, depending on the way in which it is used. We routinely use X-rays to examine bones for fractures, treat cancer with radiation, and diagnose diseases with the help of radioactive isotopes. Approximately 17% of the electrical energy generated in the world comes from nuclear power plants. However, on the other hand, it is impossible to forget the devastation that nuclear bombs caused in the cities of Hiroshima and Nagasaki. The radioactive wastes from nuclear energy have caused, and continue to cause, serious environmental damage.
Nuclear fission is the splitting of the nucleus of the atom; the resulting energy can be used for a variety of purposes. The first controlled fission of an atom was carried out in Germany in 1938. However, the United States was the first country to develop an atomic bomb, which was subsequently dropped on the Japanese cities of Hiroshima and Nagasaki. The world's first electricity-generating reactor was constructed in the United States in 1951 and the Soviet Union built its first reactor in 1954. In December 1953, President Dwight D Eisenhower in his 'Atoms for Peace' speech made the following prediction:
Biological effects of radiations
Radioactive substances are among the most toxic substances known. Radium is 25,000 times more lethal than arsenic. The cell, which is the fundamental unit of life, is the primary site of radiation damage. If too many cells are damaged, the symptoms show up in the growing tissues as in the case of loss of hair, ulceration of the mouth, the reddening and hemorrhaging of the skin and lowering of the blood count. If these symptoms grow more severe, death will result.
(i) Somatic effects
These are the direct results of action of radiation on the body cell and tissues. Uranium mineworkers, painters of radium dials and Radiologists suffer most. These effects may be' immediate or delayed. More evidence of degree and kind of damage from radiation came from studies of the Nagasaki and Hiroshima survivors. If one survives the phase of radiation illness in the 50 to 500 rad. range, the other illness one is likely to become a victim are-cardiovascular disorder, cataract, leukemia, sterility, premature ageing and shortenings of life span. All these are somatic effects.
(ii) Genetic effects
There is another more serious type of effect of ionizing radiations, known as genetic effect. This arises from the damage to the sex cells. If a sex cell is damaged and if that sex cell is one of the pair that goes into the production of a fertilized ovum, it will give rise to an offspring with various kinds of major or minor physical defects.
Radioactive Wastes from Nuclear Power Plants
The hazards of radioactive materials stem from their basic characteristic that radiation cannot be detected by sense organs except in massive doses. Further, there is no way of destroying radioactivity. The radioactive waste from nuclear plants may be in form of gases, liquids or solids.
There is no suitable and cheap method of storing the radioactive waste. At any time, radioactivity is likely to escape from the waste in water bodies, concrete cases and salt formations in high mountains. The nuclear waste is thus likely to get leached into the biosphere. Among the long-lived fission products the most hazardous are Strontium-90 (half life 28.9y) and caesium- 137 (half life 30.2y).
The gaseous fission product iodine-131 (half life 8.1 days) is of hazardous nature in the event of its leakage during reactor operation.
The highly toxic alpha-active element plutonium (half life 24,100y) is another reactor product that has to be taken care of. All these elements enter the human system and get deposited in various parts of the body causing cell damage. Some of the radio nuclides in these effluents have long half-lives. Sr-90 is produced in larger amounts than others. Radionuclides have become distributed throughout the environment and are transmitted to man via the food chain. When taken in by man, some radio nuclides become concentrated in specific organs where they become injurious to health.
Reactor Accidents (Chernobyl Accident)
A reactor is one in which fission of atomic fuel occurs. The power plants are designed in a way that there is no leakage of radioactive materials in any form. However, no nuclear plant is contamination proof. During recent years nuclear power programmes have been beset with problems. These problems have reached a climax with two accidents - Three Mile Island in US in 1979 and Chernobyl in Ukraine (erstwhile USSR) in 1986. These two major accidents have greatly shaken the public's confidence in the inherent safety of nuclear power. Significantly both the accidents were due to human error. The Chernobyl accident was relatively more serious.
The radiological impact from the routine operation of nuclear power stations (NPS) is negligible, but concern remains about the consequences of potential accidents. The concerns have increased manifold after the accident at Unit-4 of the Chernobyl NPS is USSR on 26th April, 1986.
The accident occurred during a low power engineering experiment, when safety systems were bypassed. Radioactive gases and dust particles were environmentally released, causing radioactive contamination all around the world in varying intensity. It is estimated that about 7,000 kilograms of highly radioactive material containing iodine-131, strontium-90 and caesium-137 and plutonium as well as other nuclides with a total activity of 50-100 million curies were released in the explosion.