Radioactivity Flashcards
Radioactivity
Discovered by AH Becquerel in 1886
It is the phenomena of self disintegration by emitting certain invisible raus by naturally occurring substances, elements and its compounds
Radioactive emissions
Alpha particle:
Positively charged helium atom
Has very less penetrating power
Can be absorbed by a sheet of paper or stopped by Aluminium foil
Beta particles:
A negatively charged particle
Penetrating power greater than Alpha Ray
Gamma rays:
These are electromagnetic radiations of low wavelength, high frequency and high energy
Their penetrating power is very great and can pass through several centimetres of lead
Radioactive isotopes
Isotopes that are unstable due to the presence of extra neutrons in their nuclei
Emit various types of radiations
For example: carbon (14), arsenic (74), sodium iodine (131), Cobalt (60), Uranium (235)
X-rays
These are a form of penetrating electromagnetic radiation similar to light
It has a shorter wavelength
Capable of penetrating solids
X-rays are produced when cathode ray falls on anti cathodes (a metal of high atomic mass like tungsten)
Its uses are: dense material like metal and bone absorb x-ray more strongly than material like wood or flash. Responsible to produce X-ray photographs for the use of medical diagnosis.
Nuclear reaction
First nuclear reaction was discovered by Rutherford in 1919
In which a nucleus is bombarded with an elementary particle like neutron, proton etc. orbit another nucleus to produce other products in a very short time span.
Nuclear fission is the fragmentation of a large nucleus into two smaller nuclei and the liberation of large amounts of energy.
Nuclear fusion is a nuclear reaction in which lighter nuclei fuses to form a nucleus of greater mass. In this reaction an enormous amount of heat is produced.
Atomic energy (nuclear energy)
Energy produced by nuclear fission on nuclear fusion
Isotopes are elements having same atomic number but different atomic mass (for example, 8¹⁶, 8¹⁷, 8¹⁸, IH¹, IH², IH³)
Isobars are elements having same atomic mass but different atomic number. (For example ,18Ar⁴⁰, 19K⁴⁰, 20Ca⁴⁰, 6C¹⁴, 7N¹⁴)
Isotones are elements having the same number of neutrons, (For example, 1H³, 2He⁴, 4Si³²)
Isosters are molecules and ions having the same number of atoms and electrons (for example, N2O, CO2)
Radioactive pollution
It is this spontaneous emission of proton (Alpha particles), electrons (beta particles) and gamma rays (short wave electromagnetic waves) due to disintegration of atomic nuclei of some elements.
Types of radiations:
Non ionizing radiations effect only those components that absorb them and have low penetrability
Ionizing radiations have high penetration power and cause breakage of macro molecules
Types of radiation particles:
Alpha particles, can be blocked by pieces of paper and human skin
Beta particles can penetrate through skin, can be blocked by some pieces of glass and metal
Gamma rays can penetrate easily to human skin and damage cell on its way through, reaching far and can be blocked only by very thick, strong and massive pieces of concrete.
Sources:
Natural: cosmic rays from space and terrestrial radiations from radio nuclides present in Earth’s crust like (radium 224, uranium 238, thorium 232, potassium 40 and carbon 14, etc)
Man made: atomic explosion or nuclear fallout
Nuclear arms use uranium 235 and plutonium 239 for fission and hydrogen or lithium as fusion material
Atomic explosions produce radioactive particles that are thrown up high into the air as huge clouds
These particles are carried to long distances by the wind and gradually settle over the earth as fall out or are brought down by rain
Fallout contains radioactive substances like strontium 90, cesium 137, iodine 131 etc.
Nuclear power plants, Nuclear weapon, transportation of nuclear material, disposal of nuclear waste, uranium mining, radiation therapy.
Effects of radioactive pollutants depend on:
Half Life, energy releasing capacity, rate of diffusion, rate of effusion, rate of deposition of pollutant, various environmental factors like wind, temperature, rainfall and influence effects.
Period of radioactivity:
Each radioactive nuclide has constant decay rate
Half life time needed for half atoms to decay
Half life of radio nuclide refers to period of radioactivity
Half life varies from fraction of second to thousands of years, radio nuclides with long half time, chief source of environment radioactive pollution.
Radiations are of two types (in regard to mode of action on cell): non ionizing and ionizing radiations
Non ionizing radiations in short wave radiations like ultraviolet rays from solar radiation. These have a low penetrating power and affect cells and molecules that absorb them. They damage eyes caused by reflections from coastal sand snow (snow blindness) and by directly looking towards the sun during eclipse. They also injured skin cells and blood capillaries producing blisters and reddening call sunburns
Ionizing radiations include x-rays, cosmic rays and atomic radiations emitted from radioactive elements.
They have a high penetration power and cause breakage of macro molecules.
The molecular damage produces short range (immediate) or long range (delayed) effects
Short range effects include burns, impaired metabolism, dead issues and death for organisms
Long range effects are mutations, increased incidences of tumors and cancer, shortening of lifespan and developmental changes
Actively dividing cells of embryo, foetus, cells of skin, intestinal lining, bone marrow and forming cells are more sensitive to radiations.
Control measures
Prevention is best control
No cure is available for radiation damage
All safety measures strictly enforced, leakage of radioactive elements to be checked
Safe disposal of radioactive waste
Regular monitoring through frequent sampling and quantitative analysis
Safety measures against nuclear accidents
Nuclear explosions and use of nuclear weapons should be completely banned
Appropriate steps should be taken to protect from occupational exposure
Government initiative to control radioactive pollution
India generate around 4 tonnes nuclear waste per year
This waste is similar to the amount of waste generated Internationally by other countries
In India any radioactive waste is disposed by following the atomic energy (safe disposal of radioactive) rules 1987
Rules are promulgated under atomic energy act of 1962
Major sources of nuclear waste are nuclear power plants and spent fuel processing facilities
In India, pant fuel is not considered as a waste as it has adopted close fuel cycle option, which involves reprocessing and cycling of spent fuel. Thus it is not disposed
SFPF is cooled for a minimum period of 5 years before taking it up for reprocessing.
