Nuclear Energy and Radiation 2

• EnvSc
  • Lecture 3
    • Ecosystem 1
    • Ecosystem 2
    • Exam & Assignments
  • Lecture 4
    • Aerosol particles 1
    • Aerosol particles 2
  • Lecture 5
    • Aerosol particles 3
  • Lecture 6
    • Env. management 1
    • Env. management 2
  • Lecture 7
    • Nuclear Energy and Radioactivity 1
    • Nuclear Energy and Radiation 2
  • Lecture 8
    • Ecotoxicology
  • Lecture 10?
    • Energy
  • Lecture Last
    • Before exam
    • Before exam 2
    • Before exam 3

Radioactivity Nuclear physics (fundamental facts about isotopes) alpha-radiation Energy: 4-9MeV Distance: Air: 5-10cm, Tissue: 20-50µm beta-radiation ... gamma-radiation ... See slides and stuff on course homepage: fy.chalmers.se/~funbd/MV/MVMF-10.htm Important concepts: Isotope Ionization Characteristics of alpha, beta and gamma radiation Ionizing → separation of matter is negative and positive fractions Radiation → positive ion + negative (usually electron) The ionizing radiation penetrates the body.

How do we define the emitting radioactive nuclei? How do we define the ionizing radiation? How do we define the interaction between the radioaction and the body? The emitting of radioative atoms (nuclei) Given by their activity = the number of decays per second Substance: A decays per second In only aplpha-decays the A alpha particles emitted per second. If only beta decays the A beta particles emittied per second Decays are assoc. with alpha and/or beta emission gamma emissions is following, usually beta-emission, but also sometimes alpha emissions Parent nucleus → decay (alpha or beta) + daughter nucleus daughter can decay, also by gamma radiation. How do we define gamma radiation? By intensity or energy and number of particles passing area per second Interaction radiation - matter The absorbed radiation energy per kg of the tissue defines the dose in the unit Gray (Gy). 1Gy=1J/kg Dose equicalent: Measured in Sievery (Sv)

"define" the biological effects of the radiation. Activity measured in Becqerel (Bq), 1Bq = 1 decay/second H = Q·D Q = quality factor gamma & beta → Q=1 alpha → Q = 20 effective dose equivalent; depends upon which tissue exposed to radiation The cells in the bone marrow producing blood cells are the most sesitive. The iris is also sensitive. Causes black spots if exposed. Reproductive organs. Swedish/EU limit: 5mSv/year Background radiation: ~1mSv/year Cosmic (1/4), soils (>1/3), our own body (K-40) (~1/3) Relate dose to effect, studies from Hiroshima bomb 1945-2000: 700 cases of leukemia, clearest link between dose and cancer No convincing argument about genetic defects! There are effects but they should not be over-estimated

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