Radioactive Decay

1. Radioactive Decay By: Nathaniel Hunt

2. Definition Radioactive decay – spontaneous process of breaking down an atomic nucleus by releasing particles and energy Let’s step back…

3. Definition • Isotopes are atoms of the same element with the same # of protons, but different # of neutrons • Unequal # of neutrons may upset the atoms’ binding energy; atoms become “unstable” • Unstable nucleus will release particles and energy to attain a balanced state (radioactive decay) • As the unstable nucleus changes, it gives off radiation

4. Definition • Radioactive isotopes are often called radioisotopes • As radioisotopes try to become stable, they transform into new elements; process called transmutation • Radioactive decay and transmutation processes continue until a new, stable, non-radioactive element forms

5. Types of Radioactive Decay Three types of radioactive decay: Alpha, Beta, Gamma Alpha Decay (α) - nucleus emits an alpha particle containing two protons and two neutrons (helium nucleus); transmutation occurs as nucleus has four less particles Alpha Decay of Americium to Neptunium

6. Types of Radioactive Decay Beta Decay (β) – a state where the nucleus of an atom has too many neutrons; the neutron transforms into a proton; an electron (Beta particle) is released from the nucleus Electron beta-minus Beta Decay of Hydrogen to Helium Variations: Positron Emission positively charged electron release Electron Capture proton to neutron Positron Decay of Carbon to Boron Electron Capture of Beryllium to Lithium

7. Types of Radioactive Decay Gamma Decay (γ) – occurs when the energy level in the nucleus is too high; the unstable nucleus changes from a higher-level energy state to a lower energy level by releasing a high energy photon known as a gamma particle or ray (energy wave) Gamma Decay of Helium

8. Types of Radioactive Decay

9. Use in Weapons Radioactive decay is used to create nuclear reactions (fission or fusion) within bombs. The release of nuclear energy must be self-sustaining, in a short time period, and in amounts large enough to cause an explosion. Bombs explode at the critical mass point (the point when the chain reaction becomes self-sustaining). • Nuclear Fusion • “joining” of two nuclei into a heavier nuclei • takes place at extremely high temperatures • releases huge amounts of energy • applied to weapons such as the hydrogen bomb • scientists still have not found a way to control fusion reactions • Nuclear Fission • “splitting apart” the nucleus into neutrons and lighter nuclei • occurs when the atom is bombarded with neutrons • applied to weapons such as the atomic bomb

10. Use in Weapons Uranium or Plutonium are typically used as the fuel for bombs as this matter is highly susceptible to radioactive decay using fission. All three types of radioactive decay (alpha, beta and gamma) are present at some point during the reaction. Millions of uranium or plutonium atoms packed tightly; necessary for chain reaction

11. Use in Weapons • The explosive’s energy impact is dependent on energy yield, burst altitude, and weapon design, but general distribution is… • 85% air blast (and shock), thermal radiation and heat • 15% nuclear radiations • 5% initial radiation • 10% residual • Air blast (and shock) – destruction of buildings (nuclear is million of times more powerful than conventional explosives) • Thermal radiation – fires and skin burns as far as 12 miles from impact (nuclear is tens of millions of degrees hotter than conventional) • Initial nuclear radiation – highly penetrating and harmful gamma rays that can travel great distances; for near ground explosion, radioactive particles can fuse with dirt and debris causing contamination • Residual nuclear radiation – radiation decay emitting gamma rays and beta particles over an extended period of time “continuous decay;” most intense after explosion and diminishes over time

12. Bibliography “Radioactive Decay.” NDT Resource Center. Iowa State University, 2012. Web. 29 Jan. 2013. <http://www.ndted.org/EducationResources/HighSchool/Radiography/radioactivedecay.htm> “Three Types of Radioactive Decay.” ThinkQuest. Web. 31 Jan. 2013. <http://library.thinkquest.org/3471/noNetscape/radiation_types.html> Walker, Gregory. “Trinity Atomic Web Site.”2003. Web. 30 Jan. 2013. <http://www.cddc.vt.edu/host/atomic/nukeffct/index.html> Wenner Jennifer M. “How Does Radioactive Decay Work?” 12 Aug. 2008. Web. 30 Jan. 2013. <http://serc.carleton.edu/quantskills/methods/quantlit/RadDecay.htm>