Chapter 18 – Ionising Radiation and Risk

Work from GCSE/AS/A2 that I need to know… / Before / After
I know that the nucleus of an atom contains protons, neutrons and electrons, and what their charges and relative masses are
I know that some nuclei are unstable and decay to produce alpha particles, beta particles and gamma rays
I know what absorbs alpha, beta and gamma and what they are used for
I know that when an atom loses or gains an electron (or electrons) an ion is formed
I know that kinetic energy = ½ mv2 and is conserved
I know that all the standing waves patterns for waves on a string and their wavelengths
I know that atoms have energy levels and electrons jump between them, emitting or absorbing photons
18.1 Radiation put to Use / Before / After
I know that ionising radiations have a wide range of uses, in medicine, technology and everyday life
I know that ionising radiations mainly interact with matter by ionising atoms. Alpha radiation is strongly ionising; beta and gamma radiation less so
I know that alpha particles have a definite range in air. Beta particles have a variable range. Gamma radiation is attenuated exponentially in absorbing material, with
I know that the unit of absorbed dose is the gray Gy, the energy in joule absorbed per kilogram of material. The unit of dose equivalent is the sievert Sv, the absorbed dose in gray multiplied by numerical factors to allow for the different effects of different types of radiation and tissue
I understand that the concept of risk combines the probability of an event with the consequences of that event occurring: risk = probability ´ consequence

18.2 The Nuclear Valley

/ Before / After
I know that stable light isotopes tend to have equal numbers of protons and neutrons; more massive isotopes have a larger proportion of neutrons to offset the mutual electrical repulsion of the protons
I know that the binding energy of a nucleus is the difference between the rest energy of the nucleus and the total rest energy of its individual nucleons. The rest energies are found from the masses, using Erest = mc2
I know that the binding energy per nucleon forms a valley with a minimum near iron
I know that alpha emission reduces proton and neutron numbers each by 2. Several chains of such decays are known
I know that electron (-) emission changes one neutron into a proton. Positron (+) emission changes one proton into a neutron
I understand that radioactive decays take a nucleus to a state of lower energy. Gamma emission does so without change in numbers of protons and neutrons
18.3 Fission and Fusion / Before / After
I know that fission releases energy by a large nucleus such as U-235 breaking into two parts
I know that fission chain reaction can occur
I know that there is a critical mass for fissile material
I know that slow neutrons are captured more efficiently than fast neutrons. Nuclear reactors use a moderator to slow the neutrons
I know that in nuclear fusion
I know that the fusion of hydrogen to helium occurs in the Sun. On Earth