rpc prelims 3 and 4?

• Radioactivity


  - some atoms exist in abnormally excited state

  -
• Radioactive Disintegration


  - known as radioactive decay

  - a process where an unstable atom emits particles and energy to transform into another atom to become stable

  - involves radionuclides
• Radionuclides


  any nuclei that undergo radioactive decay
• Radioisotopes


  - a type of radionuclides

  - Isotopes that are unstable by either having too few or too many neutrons

  - may be naturally occurring or artificially produced
• Naturally Occuring Radioisotopes


  - may originate at the time of the Earth's formation and are still decaying very slowly

  - may also be produced in the upper atmosphere through the action of cosmic radiation
• Artificially Produced/ Made Radioisotopes


  man-made products, produced in machines such as particle accelerators or nuclear reactors
• Beta Emission (Beta-Decay)


  - occurs in neutron-rich nuclei

  - occurs in stable nuclides bombarded with neutrons in nuclear reactors

  - electron is created in the nucleus and is ejected with considerable kinetic energy and escapes the atom
• Beta Emission (Beta-Decay)


  - a simultaneous conversion of neutron to a proton also occurs

  - the result is the loss of a small quantity of mass and one unit of negative electric charge from the nucleus of the atom
• Beta Emission (Beta- Decay)


  - the atomic number increases by one (Z=Z+1), while the atomic mass number remains the same (A=constant)

  - this tranformation results in the changing of an atom from one type of element to another
• Beta Emission (Beta- Decay)


  - a negatron and an antineutrino are emitted

  - absorbed by Aluminum
• Positron Emission (Beta+Decay)


  - important for some nuclear medicine imaging

  - occurs in proton-rich nuclei

  - occurs in stable nuclei bombarded with charged particles in
• Positron Emission (Beta+ Decay)


  - one proton is converted into a neutron

  - results in a decrease to the atomic number by 1 (Z=Z-1), w
• Electron Capture


  - an electron from the closest energy level falls into the nucleus, causing a proton to become a neutron

  - A neutrino is also emitted from the nucleus

  - another falls into the empty energy levels causing a cascade of falling electrons

  - atomic number decreases by one and atomic mas number remains unchanged
• Internal Conversion


  - process in which the nucleus of an atom with excess energy released that energy without altering its proton and neutron count
• Alpha Emission (Alpha Decay)


  - much more violent process than beta emission

  - a nucleus must be extremely unstable to emit alpha particles

  - consists of two protons and two neutrons bound together, it's atomic mass is 4
• Alpha Emission (Alpha Decay)


  - occurs when the nucleus is too large or too heavy

  - occurs when a large atom (Z=82 above) loses 2 protons and 2 neutrons leaving a decay product

  - coincidentally the atomic mass number loses a value of 5 and the atomic number loses a value of 2

  - least penetrating and is absorbed by paper
• Gamma Ray Decay


  - occurs when the nucleus of an atom is still unstable after a beta or alpha decay

  - the nuclei emits gamma radiation in order to become stable
• Isometric Transition


  a nuclear process in which a nuclei with excess energy following alpha or beta decay emits energy without charging the atomic number and atomic mass number
• Decay Chain


  a series of transformations that a given radionuclide will undergo and what type of radiation it will emit
• Four Decay Chain for Natural Radioactive Series

  235-U series

  232-Th series

  238-U series

  237-Np series
• Radioactive Equilibrium


  occurs in the decay chain when the rate of creation and decay of a radionuclide is the same rate
• Transient Equilibrium


  occurs when the half-life of the original radionuclide and its product are similar
• Secular Equilibrium


  the half-life of the original radionuclide is longer than that of the product
• No Equilibrium


  the half-life of the decay product is longer than that of the original radionuclide
• Half-Life


  the time required for a quantity of radioactivity to be reduced to one-half its original value
• Physical Half-Life


  the time required for a quantity or radioactivity to be reduced to one-half its original value
• Biologic Half-Life


  the time required for the human body to eliminate one-half of the dose of any substances by biological process (sweating, urinating, defecation, or breathing)
• Effective Half-Life


  - combination of both half-life

  - used when health physicists calculate the dose received from an internal radiation source
• Antoine Henri Becquerel


  father of radioactivity

  ​
• Marie and Pierre Curie


  - extensively studied Uranium

  - Discovery of Radium and Polonium
• CURIE (Ci)


  - conventional unit

  - corresponds to the activity of 1 gram of Radium 226

  - 1 = 3.7x10¹⁰ Disintegration per second (dps)
• BECQUEREL (Bq)


  - Sl unit

  - 1 = 2.7x10^-11

  - 1 = 1 dps