Railway Science (Physics-Radioactivity)

The unit is named for the famed scientist Marie Curie, or the SI unit Becquerel (Bq). SI Units: Watt (Power), Pascal (Pressure), Ampere (Current). Other Units - meter (m, length), kilograms (kg, mass), second (s, time), kelvin (K, temperature), mole (mol, amount of substance).

Heavy water is an isotope of hydrogen called deuterium oxide (D₂O). It is used in Nuclear power plants where it acts as a neutron moderator to slow down neutrons. It was discovered by Harold C. Urey (1931). Nuclear power Plants in India: Kakrapar – (1993, Gujarat); Tarapur – (1969, Maharashtra); Narora - (1991, Uttar Pradesh); Kaiga - (2000, Karnataka).

𝑈²³⁵ (Uranium) is processed into small ceramic pellets and stacked together into sealed metal tubes called fuel rods. Inside the reactor vessel, the fuel rods are immersed in water which acts as both a coolant and moderator. The main fuels used in nuclear fusion are deuterium and tritium, both are heavy isotopes of hydrogen.

Nuclear fusion is possible only at high temperature and pressure. In a fusion reaction, two lighter nuclei combine to form a heavier nucleus. It is the fundamental process that powers the sun and other stars, where hydrogen nuclei (protons) fuse to form helium. Nuclear fission - A process in which the nucleus of an atom is split into two or more smaller nuclei, along with the release of a large amount of energy. It is the process used in nuclear power plants and nuclear weapons.

When it explodes, it results in a chain reaction in which isotopes of hydrogen combine to form helium. Thermonuclear fusion is achieved by raising the temperature of the system so that particles have enough kinetic energy to overcome the Coulomb repulsive behaviour. Thermonuclear fusion is the source of energy output in the interior of stars.

Process in which lighter atomic nuclei, such as hydrogen, combine to form heavier nuclei, such as helium. This process releases a tremendous amount of energy. Example - Hydrogen bomb. Nuclear Fission (process used in nuclear power plants) - Involves the splitting of heavy atomic nuclei into lighter nuclei. Example - Atomic bomb.

Nuclear fission produces free neutrons, photons and releases a large amount of energy. Uranium and Plutonium are most commonly used for fission reactions in nuclear power reactors because they are easy to initiate and control. Nuclear fusion occurs when two atoms slam together to form a heavier atom, like when two hydrogen atoms fuse to form one helium atom (same process in the Sun) and creates huge amounts of energy. Nuclear energy is the energy in the nucleus, or core, of an atom. It can be used to create electricity, but it must first be released from the atom.

It is a positively charged particle emitted from the decay of various radioactive materials. Symbol α, α²⁺, He²⁺ . Uses (Alpha Particle) : treatment of cancer, smoke detectors, providing power to spacecrafts, oil industry. Beta Particles (β) are high energy, high speed electrons (β⁻) or positrons (β⁺) that are ejected from the nucleus by some radionuclides during a form of radioactive decay. Uses : To treat health conditions such as eye and bone cancer. Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. Uses : Medicine (radiotherapy), the nuclear industry. Neutrons : Subatomic particles that are one of the primary constituents of atomic nuclei. Uses : To analyze simple samples of materials in a nuclear reactor

Uranium (symbol ‘U’ and atomic number 92). It is a radioactive metal. Nuclear fuel is a substance that is used in nuclear power stations to produce heat to power turbines. The most common nuclear fuels are the radioactive metals Uranium - 235, and Plutonium - 239.

It was discovered by Martin Klaproth. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. It has the highest atomic weight of all naturally occurring elements. Gold (Au, 79), silicon (si 14), Radon (Rn 86).