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, Web. 29 Jan <
“Three Types of Radioactive Decay.” ThinkQuest. Web. 31 Jan
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Walker, Gregory. “Trinity Atomic Web Site.” Web. 30 Jan <
Wenner Jennifer M. “How Does Radioactive Decay Work?” 12 Aug Web. 30 Jan <