Atom’s Nucleus and Radioactivity 20 October 2015 Background Background Radioactivity and natural background exposure Radioactivity and natural background exposure Principles of radioactivity and human health Principles of radioactivity and human health Application of the principles of radioactivity Application of the principles of radioactivity

Isotopes Atoms have specific number of protons, neutrons and electrons Atoms have specific number of protons, neutrons and electrons 8 8 OOxygen-16 OOxygen-16 16(breath deep …) 16(breath deep …) If the number of protons is unchanged but the number of neutrons goes up or down, what happens to the chemical properties of that element (i.e., Periodic Table)? If the number of protons is unchanged but the number of neutrons goes up or down, what happens to the chemical properties of that element (i.e., Periodic Table)? 8 OOxygen-17 OOxygen-17 17(breath deep …) 17(breath deep …)

Isotopes … A Bit More Atoms of an element with same number of protons but different number of neutrons = isotopes Atoms of an element with same number of protons but different number of neutrons = isotopes Conventional notation (Element - Mass) Conventional notation (Element - Mass) Oxygen -17 or Oxygen -16 Oxygen -17 or Oxygen -16 Carbon -12 or Carbon -13 Carbon -12 or Carbon -13 Iodine -131 Iodine -131 Cesium -135 Cesium -135 Plutonium -237 Plutonium -237 Uranium -235 Uranium -235

Example: Isotopes of Hydrogen Hydrogen 1 1 H Stable Deuterium 1 2 H Stable Tritium 1 3 H Unstable Proton Neutron What is a stable versus an unstable isotope?

Stable Versus Unstable Isotopes Stable over time Stable over time Oxygen-16 Oxygen-16 Carbon -12 Carbon -12 Carbon -13 Carbon -13 Unstable: “atom changes” by releasing mass and/or energy (i.e., radioactive) Unstable: “atom changes” by releasing mass and/or energy (i.e., radioactive) Carbon -14 (radioactive carbon) Carbon -14 (radioactive carbon) Hydrogen-3 (radioactive hydrogen/tritium) Hydrogen-3 (radioactive hydrogen/tritium)

Unstable Isotopes: Radioactive Emissions Alpha  2 protons + 2 neutrons (same as the helium atom) Alpha  2 protons + 2 neutrons (same as the helium atom) Beta (  ): high energy electron Beta (  ): high energy electron Gamma (  ): electromagnetic radiation with very short wavelengths (not visible to eye) Gamma (  ): electromagnetic radiation with very short wavelengths (not visible to eye)

Natural or Background Radioactivity Sources Sources Cosmic rays from outer space Cosmic rays from outer space Soils Soils Water Water Building materials Building materials(rock) Nuclear sources Nuclear sources Examples Examples Radon gas (Radon-222) - soils Radon gas (Radon-222) - soils Beryllium (Beryllium-7) - atmosphere Beryllium (Beryllium-7) - atmosphere Annual Mean Exposure (OSU)

Example: Radon Exposure in the Home Radon gas (Radon-222) Radon gas (Radon-222) Radioactive gas Radioactive gas Human health effects - lungs Human health effects - lungs Human health exposure Human health exposure Homes Homes At-risk groups: smokers At-risk groups: smokers Risk mitigation - venting of basements Risk mitigation - venting of basements Geologically based radioactivity: 100% natural Geologically based radioactivity: 100% natural

The Essence of Being Unstable: Radioactive Decay Uranium-238 Uranium protons neutrons (contrast with other atoms) Spontaneous release of an alpha (  ) particle (2 protons + 2 neutrons): atom now with only 90 protons and mass of 234, which is ____? Spontaneous release of an alpha (  ) particle (2 protons + 2 neutrons): atom now with only 90 protons and mass of 234, which is ____? All isotopes of all elements with > 83 protons (Bismuth) are unstable and radioactively decay All isotopes of all elements with > 83 protons (Bismuth) are unstable and radioactively decay Rate of decay: unaffected by the environment Rate of decay: unaffected by the environment

Periodic Table

Types of Decay and Human Health Alpha (  ) Alpha (  ) Two protons + two neutrons Two protons + two neutrons Travel distance: stopped by sheet of paper (even air) Travel distance: stopped by sheet of paper (even air) Beta (  ) Beta (  ) high energy electron high energy electron Travel distance: ~10 meters; stopped by 1 cm aluminum block Travel distance: ~10 meters; stopped by 1 cm aluminum block Gamma (  ) Gamma (  ) high energy radiation high energy radiation Travel distance: 100’s meters; stopped by 5 cm lead brick Travel distance: 100’s meters; stopped by 5 cm lead brick

Penetration of Different Types of Ionizing Radiation Alpha Particles Stopped by a sheet of paper Beta Particles Stopped by a layer of clothing or less than an inch of a substance (e.g. plastic) Gamma Rays Stopped by inches to feet of concrete or less than an inch of lead Radiation Source

Radioactivity: Human Health Radioactivity in biological tissues results in atoms being ionized Radioactivity in biological tissues results in atoms being ionized Disrupts chemical bonds Disrupts chemical bonds DNA as primary site of action (e.g., mutations) DNA as primary site of action (e.g., mutations) Disrupts biochemistry Disrupts biochemistry Sensitivity greatest for actively growing cells Sensitivity greatest for actively growing cells Blood (Strontium-90) Blood (Strontium-90) Bone marrow (Cesium-137) Bone marrow (Cesium-137) Thyroid (Iodine-131) Thyroid (Iodine-131) Muscle (Pu-239) Muscle (Pu-239)

Periodic Table

Radioactivity: Principles and Applications Background Background Radioactivity is natural Radioactivity is natural Quantitative analysis of radioactivity Quantitative analysis of radioactivity Principles of radioactivity and human health Principles of radioactivity and human health Application of the principles of radioactivity Application of the principles of radioactivity

Radioactive Decay Rate of decay to a stable state (no more spontaneous decay): specific for each isotope Rate of decay to a stable state (no more spontaneous decay): specific for each isotope Rate: unique terminology = “half-life” Rate: unique terminology = “half-life” Time for ½ (50%) of atomic nuclei to decay to the stable state (abbreviated t 1/2 ) Time for ½ (50%) of atomic nuclei to decay to the stable state (abbreviated t 1/2 ) Range: fractions of second to billions of years (isotope specific) Range: fractions of second to billions of years (isotope specific) Unaffected by the environment (e.g., moisture, light, pressure, etc.) Unaffected by the environment (e.g., moisture, light, pressure, etc.) Example: M&M’s Example: M&M’s

Radioactive Decay

Question The half-life of a radioactive element is ___. A. the time it takes for 50% of the atoms in a sample to spontaneously decay B.indicates that it is capable of reducing the life of an exposed human by 50% C.describes 50% of the energy that is released when the atomic nucleus decays D.is a measure of 50% the radioactivity that is emitted from each atomic nucleus that decays

Question As the temperature of a sample of radioactive element increases, the half-life will ___. A.Decrease B.Remain unchanged C.Increase D.None of the above

Question There are two radioactive sources, A and B; both have the same number of unstable nuclei at the beginning. After 10 days, the number of unstable nuclei remaining for B is more than A. Which of the following statements is correct? A.The mass of A is larger than that of B B.The mass of B is larger than that of A t 1/2 C.The half-life (t 1/2 ) of B is longer than that of A t 1/2 D.The half-life (t 1/2 ) of A is longer than that of B

Application of Atomic Principles of Radioactivity Medical science Medical science Nuclear energy Nuclear energy Chernobyl Russia Chernobyl Russia Fukishima Japan Fukishima Japan Dirty bomb Dirty bomb

Medical Science: Nuclear Applications Nuclear imaging and radio-pharmaceuticals Nuclear imaging and radio-pharmaceuticals Injection of radioactive element Injection of radioactive element Allow for distribution in body Allow for distribution in body Imagine body for presence or absence of radioactive element Imagine body for presence or absence of radioactive element Function: assessment of functional and dysfunctional tissues (e.g., thyroid, kidneys, heart, liver) Function: assessment of functional and dysfunctional tissues (e.g., thyroid, kidneys, heart, liver) Examples Examples Iodine-131 (thyroid) Iodine-131 (thyroid) Thallium-201 (kidney) Thallium-201 (kidney)

Nuclear Reactor: Power Generation (read section in text) Fuel rods Moderators Coolants Steam turbines Cooling towers Nuclear waste storage Comparison with fossil fuel power generation

Chernobyl Reactor and Sarcophagus - April 1986 Complete core meltdown Sarcophagus - risk containment Human health (~4,000 death) Acute radiation poisoning – on site workers Chronic exposure - residents Iodine -131 Thyroid cancer and leukemia No detectable effects > 100 miles

Fukushima Daiichi Nuclear Power Plant Accident - March 2011

Question Fissionable (means what?) uranium-233, uranium- 235 and plutonium-239 are used in nuclear reactors as ___. A.Coolants B.Control rods C.Moderators D.Aspirators E.Fuels

Question Nuclear reactors and traditional fossil fuel combustion (gas and/or coal) plants share the following fundamental energy conversion feature. A.Nuclear reactor B.Control rods C.Power lines D.Aspirators E.Stem-driven generators to convert chemical energy to electrical energy

Atom’s Nucleus and Radioactivity 20 October 2015 Background Background Radioactivity and natural background exposure Radioactivity and natural background exposure Principles of radioactivity and human health Principles of radioactivity and human health Application of the principles of radioactivity Application of the principles of radioactivity