let’s build up your Interest.(introduction)
Yes it’s true that Nuclear power plants are the gift by the man to the nature(The same man who gave the formula on how to destroy nations by the so called atomic bombs) as of the property of clean source of energy but as every gift comes with some intension every technology comes with some flaws(negative sides) and in this case it is nuclear hazards, threats of nuclear radiations, threats to humans if these radiations spread, disposal of nuclear waste . An example of one given in the next paragraph.
Chernobyl one of the most deadliest nuclear accident that happened on the 26 april 1986.The accident happened because of the blast of no 4 nuclear reactor of Chernobyl nuclear power plant as a result of large amount of heat produced inside it causing the nuclear radiation to release out of the plant resulting in the deaths of ten of thousands of people from the radiations .It is one of the example of many nuclear accidents .Let’s completely understand what are nuclear hazard, sources of nuclear pollution, types of nuclear radiation, human risks, control of nuclear hazard and disposal of nuclear waste.
Nuclear hazards And types of radiation released
Nuclear hazards are the threats posed by the invisible and odourless contamination of environment by the presence of radioactive materials such as radio-nuclides in air, water or soil .These radio-nuclides emit high energy particles( alpha and beta rays) and electromagnetic radiations (gamma rays).Radio nuclides are elements, such as uranium 235, uranium 283, thorium 232, potassium 40, radium 226, carbon 14 etc., With unstable atomic nuclei and release ionizing radiation in the form of alpha, beta, and gamma rays.The spontaneous emmision of particles and rays by unstable nucleus is called radioactivity and contamination of environment with these radiations is called as Nuclear pollution.
Nuclear radiations arises from hundreds of different kinds of unstable atoms. While many exist in nature majority are created in nuclear reactions .Ionizing radiation which can damage the living tissue is emitted as the unstable atom decays spontaneous to become different kinds of atoms.
The principle kind of ionizing radiation are:
Alpha particles: These are helium nuclei consisting of two protons and two neutrons and are emitted from naturally occurring heavy elements such as uranium and radium also from some man made transuranic elements. They are intensely ionizing but cannot penetrate the skin.
Beta particles: These are fast moving electrons emmited by the many radioactive elements. They are more penetrating than alpha particles but easily shielded -they can be stopped by a few millimeterers of wood or aluminium. They can penetrate a little way into human flesh . Exposure produces an effects like sunburn, but which is slower to heal.
Gamma rays: These are high energy beams much the same as x-rays. They are emmited in many radioactive decays and are very penetrating, so require more substantial sheilding.
Sources of nuclear hazards/ nuclear pollution
The sources of nuclear pollution/Nuclear hazards include both natural and man-made sources. The human environment has always been radioactive and account for up to 85% of annual human radiation dose. Radiation arising from human activities typically account for up to 15%of the public’s exposure every year.
Natural sources: Most radiation exposure is from natural sources. These include: Radioactivity in rocks and soil of the earth crust; radon, a radioactive gas given out by many volcanic rocks and uranium ore, cosmic radiations etc.
Man-made sources: These sources involve any process that emantes radiation in the environment. There are many causes of radiation pollution which are:
1)Nuclear waste handling and disposal: It may generate low to medium radiation over long period of times. The Radioactivity may contaminate and propogate through air, water and soil as well. The main issue with the radiation waste is that it cannot be degraded or treated chemically or biologically. Thus the only option to contain the waste is by storing it in tightly closed container shielded with radiation-protective materials ( such as Pb) or,if containing is not possible than to dilute it. The waste may also be contained by storage in remote areas. However with time, the shields may be damaged.
2) Use of radioactive materials in defense weapon production:
Nuclear weapon production may also release radiations from the handles radioactive materials( usually of high health risks).
3) Nuclear explosions and detonations of nuclear weapons: The highest amount of human induced radiation pollution have been generated probably in the mid twenty century through various experiments or combat nuclear detonations, that ended the second world war.
4) Mining and processing of radioactive ores: It involves the crushing and processing of radioactive ores and generate radioactive by products. Mining of other ores may also generate radioactive wastes( such as Mining of phosphate ores).
5) Nuclear accidents: explosion at Three Mile Island 1979 and Chernobyl 1986 nuclear power plant accidents are the classic examples of radiation pollution from these type of source.
6) Use of radioactive isotopes in medical, industrial and research applications: 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.
Human risks effects of nuclear hazards/ Pollution.
Radioactive substances when released into the environment are either dispersed or become concentrated in living organisms through food chain. Other than naturally occurring radioisotopes, significant amount are generated by human activity, including the operation of nuclear power plants, the manufacture of nuclear weapons, and atomic bomb testing. Typically these effects can be of two types:
1)Somantic effects: Somantic affects the function of cells and organs of the individual exposed. If causes damages to cell membranes, mitochondria and cell nuclei resulting in abnormal cells functions, cell division, growth and death.
2)Genetic effects: Radiation can cause mutation, which are changes in genetic makeup of cells and effects future generations also. These effects are mainly due to damages to DNA molecules. People suffer from blood cancer and bone cancer if exposed to higher doses around 100 to 1000 roentgens.
Nuclear hazard effects can either be initial or residual. Initial effects occur in the immediate area of explosion and are hazardous immediately after explosion.
The principle initial effects are blast and radiation. Blast causes damage to lungs, ruptures eardrum, collapses structure and causes immediate death or injury.
Thermal radiation is heat and light radiation, which a nuclear explosion fireball emits producing extensive fires, skin burns and flash blindness.
Nuclear radiation consists of intense gamma rays and neutrons produced during first minute after explosion. This radiation causes extensive damage to cells throughout the body. Radiation damage may cause headaches, nausea, vomiting, diarrhoea, and even death depending on the radiation dose received .
Some of the possible human health effects are listed as under:
1)Effects on DNA and mutation: Radiation may break chemical bonds such as DNA in cells and cause mutation. This effect the genetic makeup and control mechanism. The effect can be instantaneous, prolonged or delayed types and even could be carried to future generations.
2)General physiological effects: Exposure at low doses of radiation (100-250 rads), men do not die but begin to suffer from fatigue, nausea, vomiting, and loss of hair. But recovery is possible.
3) Effects on Immunity: Exposure to 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 does of infection and bleeding.
4)Effects on tissues and vital organs: Higher doses of radiation ( 10,000 rads) kill the organism by damaging the tissues of heart, brain etc. Hypothyroidism may also be a radiation cause due to the destruction of thyroid gland by radioactive accumulated iodine.
5)Occupational diseases: Few occupations that involve radioactive exposures are uranium mineworkers, radium watch dial painters, technical staff at nuclear power plant. Exposure to radioactive or Nuclear hazards has been clinically proven to cause cancer, mutation, Teratogenesis(Taratogenesis is a prenatal toxicity characterized by structural or functional defects in the developing embryo or foetus).
6)Effects through biomagnification: Through food chain also, Radioactivity effects are experienced by man. E.g. Strontium 90 behaves like calcium and is easily deposited and replaces calcium in the bone tissue. It could be passed to human beings through ingestion of Strontium contaimenated milk.
7)Cancers: Cancer generation is the most typical health effect of radiation exposure, especially when high or moderate amount of radiation is involved. Lung cancer is a typical example of exposure to radon.
Control of Nuclear hazards
Peaceful uses of radioactive materials are so wide and effective that we cannot go without them but also there is no cure for radiation damage. Thus only option to prevent or control these hazards is to check and prevent radioactive pollution.
Following are the ways to prevent or control these hazards:
1)Leakage from nuclear reactor, 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 and strengthened against nuclear accidents
3) Waste disposal must be careful, efficient, effective.
4) Appropriate steps should be taken against occupational exposure.
5) Preventive measures should be followed so that background radiation levels do not exceed the permissible limits.
6) There should be regular monitoring and quantitative analysis through frequent sampling in the risk areas.
Disposal of nuclear waste
Since nuclear waste can be extremely dangerous and, therefore, the way in which they are to disposed is strictly controlled by international agreement. Since 1931, by international agreement, the disposal in the Atlantic ocean and into the atmosphere has been banned. After processing, to recover usable materials and reducing the radioactivity of the waste, disposal is made in solid form where possible.
The nuclear wastes are usually classified into three category:
1)High level wastes(HLW): High level wastes are very high-radioactivity per unit volume. E.g. spent nuclear fuel. HLWs have to be cooled and are therefore, stored for several decades by it’s producer before disposal. Since these wastes are so dangerous to be released anywhere in the biosphere, therefore they must be contained either by converting them into inert solids(ceramics) and then hurried 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 buddies 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 is designated sites. In India, a Waste immobilization plan( WIP) was commissioned in 1985 at Tarapore. It verifies HLWs.
Precaution after disposal of nuclear waste
The careful, efficient and treatment/disposal of radio active 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.