Short essay on Nuclear hazards

The principal sources that are of environmental concern are the nuclear weapons and nuclear power reactors in the event of mishaps. Before we consider these hazards in detail we with examine the effects of the nuclear radiations on the life system.

A number of nuclear explosions have already been made during recent past in different pa of world. Irrespective of judgments about the ethics of this practice, these tests occurred, injecting substantial amounts of radioactivity into the environment. Nuclear explosions are very rapid and based on a rough estimate, in an explosion about 50 per cent of the energy goes to the blast, 33 per cent as heat and the rest 17 per cent or so to radioactivity.

The radioactive dust that falls to the earth after atomic explosion is called radioactive fallout. The estimated percept dose to world population from fallout of past nuclear explosions is 10 microsievert per year.

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.

The radioactive dust got dispersed over vast areas in Europe, affecting (in addition to USSR), France and even parts of UK. Dose values as high as 760 microsievert per year, has been reported for some European countries following the accident. In the weeks following the accident, fresh vegetables in many parts of Europe showed levels of radioactivity much above the permissible levels.

Cattle grazing on contaminated grass were soon producing milk with significant radioactivity. Large populations in the area around the reactor were evacuated. The soil samples from the farmland in the area show radioactivity 170 times the value regarded as tolerable. Some forecasts suggest that the radioactive fallout from Chernobyl could cause as many as 40,000 deaths from cancer world-wide, mainly in Europe.

The dominant source of lead in air is petrol, although significant contributions arise fro- metal works, coal combustion and waste incineration. Lead is emitted in the form of fumeof dust and is a cumulative poison acting on the nervous system.