रेडियोधर्मिता का परिचय

Introduction to Radioactivity

• Radioactivity is the spontaneous emission of particles or energy from the nucleus of an unstable atom.
• This process occurs naturally in some elements and can be induced artificially through nuclear reactions.
• Unstable atoms, or radioisotopes, attempt to achieve a more stable nuclear configuration by emitting energy as radiation.

Types of Radioactive Decay

• Alpha decay: The nucleus emits an alpha particle, a helium nucleus (2 protons and 2 neutrons). This decreases the atomic number by 2 and the mass number by 4.
• Beta decay: A neutron transforms into a proton, emitting a beta particle (an electron) and an antineutrino. This increases the atomic number by 1, while the mass number remains the same.
• Gamma decay: The nucleus releases high-energy photons (gamma rays). This doesn't affect the atomic number or mass number.
• Positron emission: A proton transforms into a neutron, emitting a positron (a positively charged electron) and a neutrino. This decreases the atomic number by 1 but keeps the mass number unchanged.
• Electron capture: The nucleus captures an inner electron, converting a proton into a neutron. This releases a neutrino and decreases the atomic number by 1, while the mass number stays the same.

Radioactive Decay Laws

• Radioactive decay is a first-order process, its rate depends solely on the number of unstable nuclei present.
• The decay rate is proportional to the number of radioactive nuclei.
• Half-life is the time it takes for half a sample to decay.
• The decay constant (λ) relates decay rate to radioactive nuclei. Decay rate formula: dN/dt = -λN

Radioactive Decay Series

• Radioactive isotopes decay into other unstable isotopes, forming a decay series or chain.
• Each isotope in the series has a distinct half-life.
• The decay series ends with a stable, non-radioactive isotope.

Uses of Radioactive Isotopes

• Medical imaging: Radioisotopes help diagnose and treat diseases. Tracers highlight specific organs/tissues in scans (e.g., PET, SPECT).
• Cancer therapy: Targeted radioisotopes destroy cancer cells, minimizing harm to healthy tissues.
• Industrial applications: Radioisotopes are used in gauging material thickness, detecting leaks and monitoring equipment.
• Dating: Radioactive isotopes determine the age of artifacts and geological formations.
• Food preservation: Irradiation with radioisotopes eliminates harmful microorganisms, extending shelf life and preserving nutrition.

Radioactive Waste Management

• Handling and storing radioactive materials ensures public safety and environmental protection.
• Different radioactive waste types require specific storage methods, considering intensity and half-life.
• Methods for disposal vary, aiming to reduce hazards and prevent contamination.

Biological Effects of Radiation

• Ionizing radiation damages biological molecules, especially DNA.
• Radioisotopes emit ionizing radiation with varying penetrating power and energy levels, affecting tissues differently.
• High radiation doses cause acute radiation sickness; chronic low-dose exposure may lead to long-term health problems, including cancer.
• Damage depends on dose, radiation type and tissue affected.

Nuclear Reactions

• Nuclear reactions alter atomic nuclei.
• Fission: A heavy nucleus splits into two or more lighter nuclei, releasing vast energy.
• Fusion: Two light nuclei combine into a heavier nucleus, also releasing significant energy.
• Nuclear reactors exploit controlled fission reactions to generate energy.

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