Radioactive (nuclear) pollution is a special form of physical pollution related to all major life-supporting systems – air, water and soil. It is always convenient to discuss radioactive pollution separately because its nature of contamination is different from other types of pollution. Its effects are also of special kinds.
Radioactivity is the phenomenon of emission of energy from radioactive isotopes (i.e., unstable isotopes), such as Carbon-14, Uranium-235, Uranium-238, Uranium-239, Radium-226, etc. The emission of energy from radioactive substances in the environment is often called as 'Radioactive Pollution'.
Sources/causes of nuclear hazards
The sources of radioactivity are both natural and man-made. The natural sources include:
1) Cosmic rays from outer space. The quantity depends on altitude and latitude; it is more at higher latitudes and high altitudes.
2) Emissions from radioactive materials from the Earth's crust.
People have been exposed to low levels of radiation from these natural sources for several millenia. But it is the man-made sources which are posing a threat to mankind. The man-made sources of radioactivity are nuclear wastes (i.e., waste material that contains radioactive nuclei) produced during the:
1) Mining and processing of radioactive ores;
2) Use of radioactive material in nuclear power plants;
3) Use of radioactive isotopes in medical, industrial and research applications; and
4) Use of radioactive materials in nuclear weapons.
The greatest exposure to human beings comes from the diagnostic use of X-rays, radioactive isotopes used as tracers and treatment of cancer and other ailments.
Effects of nuclear hazards
The effects of radioactive pollutants depend upon half-life, energy releasing capacity, rate of diffusion and rate of deposition of the contaminant. Various atmospheric conditions and climatic conditions such as wind, temperature and rainfall also determine their effects.
All organisms are affected from radiation pollution, and the effects are extremely dangerous. The effects may be somatic (individual exposed is affected) or genetic (future generations) damage. The effects are cancer, shortening of life span and genetic effects or mutations. Some of the possible effects are listed as under:
1) Radiations may break chemical bonds, such as DNA in cells. This affects the genetic make-up and control mechanisms. The effects can be instantaneous, prolonged or delayed types. Even it could be carried to future generations.
2) Exposure at low doses of radiations (100-250 rads), men do not die but begin to suffer from fatigue, nausea, vomiting and loss of hair. But recovery is possible.
3) Exposure at higher doses (400-500 rads), the bone marrow is affected, blood cells are reduced, natural resistance and fighting capacity against germs is reduced, blood fails to clot, and the irradiated person soon dies of infection and bleeding.
4) Higher irradiation doses (10,000 rads) kill the organisms by damaging the tissues of heart, brain, etc.
5) Workers handling radioactive wastes get slow but continuous irradiation and in course of time develop cancer of different types.
6) Through food chain also, radioactivity effects are experienced by man.
But the most significant effect of radioactivity is that it causes long range effects, affecting the future of man and hence the future of our civilization.
Control of nuclear hazards
On one hand, the peaceful uses of radioactive materials are so wide and effective that modern civilization cannot go without them; on the other hand, there is no cure for radiation damage. Thus the only option against nuclear hazards is to check and prevent radioactive pollution. For this:
1) Leakages from nuclear reactors, careless handling, transport and use of radioactive fuels, fission products and radioactive isotopes have to be totally stopped;
2) Safety measures should be enforced strictly;
3) Waste disposal must be careful, efficient and effective;
4) There should be regular monitoring and quantitative analysis through frequent sampling in the risk areas;
5) Preventive measures should be followed so that background radiation levels do not exceed the permissible limits;
6) Appropriate steps should be taken against occupational exposure; and
7) Safety measures should be strengthened against nuclear accidents.
Disposal of nuclear wastes
Since nuclear waste can be extremely dangerous and, therefore, the way in which they are to be disposed of is strictly controlled by international agreement. Since 1983, by international agreement, the disposal in the Atlantic Ocean and into the atmosphere have been banned.
After processing, to recover usable material and reducing the radioactivity of the waste, disposal is made in solid form where possible. The nuclear wastes are usually classified into three categories:
1) High Level Wastes (HLW): High level wastes have a very high-radioactivity per unit volume. For example, spent nuclear fuel. HLWs have to be cooled and are, therefore, stored for several decades by its producer before disposal. Since these wastes are too dangerous to be released anywhere in the biosphere, therefore, they must be contained either by converting them into inert solids (ceramics) and then buried deep into earth or are stored in deep salt mines.
2) Medium level wastes (MLW): Medium level wastes (e.g., filters, reactor components, etc.,) are solidified and are mixed with concrete in steel drums before being buried in deep mines or below the sea bed in concrete chambers.
3) Low liquid wastes (LLW): Low liquid wastes (e.g., solids or liquids contaminated with traces of radioactivity) are disposed of in steel drums in concrete-lined trenches in designated sites.
In India, a Waste Immobilization Plant (WIP) was commissioned in 1985 at Tarapore. It verifies HLWs.
Precautions after the disposal of nuclear waste
The careful, efficient and effective treatment/disposal of radioactive waste, just do not complete the task. A regular supervision of the disposal sites is must. The essential precautions, at the disposal sites, that have to be taken include:
1) Monitoring radioactivity around the disposal sites.
2) Prevention of erosion of radioactive waste disposal sites.
3) Prevention of any drilling activity in and around the waste disposal site.
4) Periodic and long-term monitoring of such disposal sites and areas of naturally occurring uranium rich rocks.
My appreciation to the author for brining out alert article on Radioactive pollution and nuclear hazards. In Hyderabad we are having the problem with both. Many cell phone towers are constructed in the ground itself , thereby exposing the radioactive element to the people in the vicinity. Normally such towers must be above the multi story apartments. Moreover in Hyderabad, the Nuclear Fuel Complex facility is amidst residential colony and if there are any nuclear hazards in future, we are going to be affected first. Still we are living with a hope that nothing will happen.