Atomic Structure and Radioactivity

• Irradiation

  an object is exposed to nuclear radiation but not made radioactive itself.
• Radioactive contamination?

  radioisotopes are transferred to an object making it radioactive.
• Ion

  charged particle produced when atom gains or looses electrons
• Ionising power

  the ability of radiation to create ions
• penetrating power

  the ability of radiation to pass through substances
• Which nuclear radiation has the highest penetrating power?

  Gamma. Infinite range in air.
• What is radioactive decay?

  some atoms are unstable, in order to become stable they release ionising radiation from the nucleus.
• What is beta decay?

  a beta particle is a fast moving electron. For every one emitted, a neutron turns into a proton. This keeps the mass number the same but the proton number decreases by 1.
• What is nuclear fission used for?

  The gamma radiation given off is transferred to thermal energy to heat water to steam to turn power station turbines. This turns the generator, generating electricity.
• What are control rods in a fission reactor used for?

  lowered between uranium fuel rods and absorb neutrons so that the chain reaction is slowed down and controlled.
• What are control rods made of?

  boron or cadmium
• What is the moderator in fission reactor?

  water or graphite. Slows down neutrons so they are more likely to hit another uranium nuclei, this speeds the reaction.
• Fusion?

  two lighter nuclei collide and high speed to fuse to create a larger nucleus. Some of the mass is converted to energy.
• what ratio is used to show how much the radioactivity of a substance will decline over a certain period of time?

  The net decline is the ratio of the number of radioactive nuclei that have decayed in a time period to the number of radioactive nuclei at the start of the time period.