RADIOACTIVITY
Science
• Radioactivity is the tendency of unstable atomic nuclei to emit particles or energy to achieve stability.
• A substance containing unstable nuclei is called radioactive.
• Radioactive emissions are spontaneous and cannot be controlled externally.
• There are four main types of radioactive radiations.
TYPES OF RADIATION
Alpha Radiation
• Consists of emission of an alpha particle (helium nucleus: 2 protons + 2 neutrons).
• Emitted by heavy nuclei with large atomic mass.
• Has low penetration power and can be stopped by paper or skin.
• Causes severe damage if ingested or inhaled.
• Reduces atomic number by 2 and mass number by 4.
Beta Radiation
• Consists of high-speed electrons or positrons.
• Beta minus decay:
– A neutron converts into a proton, electron, and antineutrino.
– Atomic number increases by 1.
• Beta plus decay (positron decay):
– A proton converts into a neutron, positron, and neutrino.
– Atomic number decreases by 1.
• Moderate penetration power; stopped by thin metal sheets.
Gamma Radiation
• High-energy electromagnetic radiation.
• Emitted when nucleus shifts from higher to lower energy state.
• Has very high penetration power.
• Requires thick lead or concrete shielding.
• Highly biologically hazardous.
Neutron Radiation
• Consists of free neutrons.
• Produced during nuclear fission and fusion reactions.
• Highly penetrating and biologically dangerous.
• Requires hydrogen-rich materials like water or concrete for shielding.
IONIZING AND NON-IONIZING RADIATION
Non-Ionizing Radiation
• Includes visible light, infrared, microwaves, radar, and radio waves.
• Does not have enough energy to ionize atoms.
• Causes heating effects but does not break molecular bonds.
Ionizing Radiation
• Includes alpha, beta, gamma rays, X-rays, and cosmic rays.
• Has sufficient energy to remove electrons from atoms.
• Can cause genetic mutations and cell damage.
• Used beneficially in medicine, industry, and research.
SOURCES OF RADIOACTIVITY
• Naturally occurring radioactive minerals (uranium, thorium, radium, potassium).
• Cosmic rays from outer space.
• Solar radiation.
• Radon gas from soil and rocks.
• Nuclear power plants and fuel cycle facilities.
• Nuclear laboratories.
• Old luminous watches and clocks (radium, tritium).
• Radioactive waste.
• Nuclear medicine.
• Nuclear weapons testing.
RADIOACTIVE DECAY
• Radioactive decay is the spontaneous transformation of unstable nuclei.
• It follows a definite statistical law.
• Activity decreases with time.
Law of Radioactive Decay
• The rate of decay is proportional to the number of undecayed nuclei.
• ΔN/Δt = λN
• λ is the decay constant.
Half-Life
• Time required for half of radioactive nuclei to decay.
• Independent of external factors like temperature and pressure.
• Half-life values range from fractions of seconds to millions of years.
• Half-life of Carbon-14 is 5730 years.
• Half-life of Thorium-232 is several billion years.
APPLICATIONS OF RADIOACTIVITY
Health and Medicine
• Nuclear medicine uses radioactive substances for diagnosis and therapy.
• Radio-pharmaceuticals are administered through injection, inhalation, or oral routes.
• Gamma scintigraphy helps detect tumors and organ dysfunction.
• Targeted radionuclide therapy destroys cancer cells with minimal damage.
• Radiation therapy is used for cancer treatment.
Food Security and Agriculture
• Radiation-induced mutation breeding improves crop varieties.
• BARC has released more than 40 crop varieties using nuclear techniques.
• Crops include groundnut, mung bean, black gram, pigeon pea, mustard.
• Radiation processing preserves food by killing microbes.
• Extends shelf life without chemical preservatives.
Hydrogel Technology
• Developed by BARC for wound healing.
• Used for burns and injury dressings.
• Prepared using gamma or electron beam irradiation.
• Provides sterilization and gel formation simultaneously.
• Retains large amount of water and accelerates healing.
Industrial Applications
• Radiation sterilization of medical equipment.
• Industrial radiography for weld inspection.
• Used in oil and gas pipelines.
• Measurement of thickness and density of materials.
• Non-destructive testing of structures.
ENVIRONMENTAL AND SAFETY ASPECTS
• Excess exposure causes radiation sickness.
• Long-term exposure leads to cancer and genetic mutations.
• Proper shielding and safety protocols are essential.
• International regulations govern radioactive waste disposal.
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Subject: Science
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