Radioactivity is a physical type of pollution or nuclear hazards, it is appropriate to think about radioactivity as independent because of the appearance of man-made radioactive materials in nature and the economy as an offshoot of industrialization, and the nature of pollution and the consequence are notably different from other types of pollution.
Environmental radiation divides into two types: naturally occurring and man-made radiation. Naturally occurring radiation is:
- Cosmic radiations from outer space reading the earth’s surface.
- Terrestrial radiation from natural radio-isotopes is present in the earth’s court.
Nuclear Hazards
Cosmic-ray bombardment of the atmosphere continuously produces a few radioactive materials of short half-life. Among them, the important nuclides are carbon-14 and hydrogen-3 (tritium). Both these are oxidized to carbon dioxide and water as they enter the biosphere and hydrosphere. Carbon-14 is formed by the action of cosmic-ray neutrons on atmospheric nitrogen, and hydrogen- 3 by splitting atoms when high-energy cosmic-ray particles strike them.
The primary sources of natural radiation or nuclear hazards are the ores of uranium and thorium, which contain a wide variety of radioactive nuclides. They differ in chemical nature, half-life, and type, and energy of radiation.
The other radionuclides found in nature are potassium-40 and rubidium-87. Potassium-40 constitutes about 0.012 percent of natural and rubidium-87 forms about 28 percent of natural rubidium. Potassium-40 is responsible for about 20 to 76 percent of the natural radioactivity of soil. Since potassium-40 contributes radioactivity to all potassium-containing systems, there will be two radioactive disintegrations per minute for each milligram of potassium. Therefore, an environmental part will be radioactive in proportion to its potassium content, including an additional contribution from biological materials. Due to its less abundance in the earth’s crust rubidium-87 consider relatively unimportant.
There are numerous possibilities for water to get contaminated with the above-mentioned radioactive nuclides when the water runs through soils and rocks. Radon-222 and its immediate daughters, radium-A through radium-C, are the common nuclides in radioactive springs.
Overview on Man-Made Radiation
Man-made radiation originates from man’s activities involving using radioactive materials. It uses for the production of nuclear weapons, nuclear fuel, and electric power. One of the most harmful uses of radioactive material is nuclear weapons, especially atom bombs. The world had already seen the nature of destruction and the impact of radioactivity on man and the environment during the second world war through the atomic bombs of Hiroshima and Nagasaki. During the last fifty years, several nuclear weapons have been tested, increasing the level of radiation in the environment.
Nuclear fuels used in the operation of reactors also contribute to pollution in nuclear reactors. The heat liberated during the fission and activation process is converted into electricity. During this process, two types of waste are developed:
- The fission products remaining in both the primary and secondary fuels.
- Extraneous activation products in the coolant. The disposal of radioactive or nuclear wastes is a great problem and causes serious marine pollution.
Major Factors to Increase Background Radiation
Two major activities behind the increase in background radiation are ore processing, operation of reactors, Nuclear Weapon Testing, Use of Radio tracers, Mobile phones, etc.
1. Ore Processing
The primary natural materials used in nuclear processes are uranium and thorium. Uranium-238 and thorium-232 are use as artificial fission materials. The only element in which natural fission occurs is uranium-235. Mining these materials is the first step in nuclear technology, and their processing contributes to background radiation.
2. Operation of Reactors
The processed nuclear fuel introduce into the reactor to perform fission activation and thermal processes. A partial transformation of primary fuel into secondary occurs in the fission process with the simultaneous appearance of fission products. Two types of wastes in these processes: fission products, remaining in the primary and secondary fuels, and extraneous activation products in the coolant. Thus, the fuel elements and coolants constitute the sources of radioactive pollution. Fission releases radioactive gases, such as xenon and Crypton, into the atmosphere.
3. Nuclear Weapon Testing
Nuclear explosion tests threaten the world since the natural background radiation of the environment is increased. The tests, including fission and fusion processes, employ uranium-235 and plutonium-239 as fission materials and hydrogen or lithium as fusion materials. Explosion, a non-moderate chain reaction, in due course results in the appearance of a very large neutron flux, which makes the surrounding matter radioactive.
Due to the force of the explosion and accompanying high temperature, radioactive products are transformed into gases. Also, it is ejected high into the atmosphere as fine particles, resulting in atmospheric pollution. This primary pollution follows by secondary pollution through radioactive fallout. These particles are subsequently carried out or otherwise settle down on soil and water due to rains and get dispersed over the surface. Thus radioactive pollution occurs not only at the test sites but also in the remote corners.
When a stream receives radioactivity from fission products through rain, the aquatic flora and fauna absorb and accumulate radioactivity. As radioactivity in the soil is available to plants, it en rs the food- chain, resulting in the possibility of eventual ingestion by humans. Thus, once again, aquatic flora and fauna used as food by man could contain dangerous amounts of radioisotopes.
4. Radio Tracers
Radio tracers are extensively used in medicine, industry, agriculture, and biology to determine the course of chemical and biochemical reactions. Among them, C14 and 1125 are the most important tracers. They are used to determine the rate and direction of groundwater low.
When wastewater containing radiotracers discharges into sewers and rivers, some isotopes, such as radioactive iodine and phosphorus, accumulate in biological slimes and sludge.