Effective dose

RADIOACTIVITY, NUCLEAR FUEL CYCLE, RADIOACTIVE WASTES MANAGEMENT

From history

1895: H. Becquerel - discovery of radiation

1896: W.C. Roentgen – X rays

1898: M. Curie-Sklodowska - discovery of radium (natural radioactivity)

1934: J. Curie – preparation of first artificial radioactive element

1942: E. Fermi – 1. controlled fission reaction

1954: Obninsk – 1. nuclear power plant

Radioactivity

· Feature of atoms (of given elements) to decay to other elements

Activity

· Amount of radioactive changes per time unit: 1 Becquerel (Bq)= 1 decay per second

Ionizing radiation

· Released by radioactive elements

· X rays

· Cosmic rays

Half time:

· Time period, one half of nuclei decay (from fraction of second up to bil. of years)

Izotope:

· Element is defined by number of protons, might differ by number of neutrons

How to detect and measure radioactivity (ionising radiation)

· We cannot use chemical procedures, but physical effects

o Vaporous chamber

o Geiger-muller

o Photographs

o Optical features of some matter

o Changes in features of semiconductors

o Thermoluminescence

Utilization of radioactive elements in practice

· Neutron activation analysis (detection of unknown elements with very low concentration – 10^-12 g/g

· Marked compounds – monitoring of chemical reactions, technological processes (e.g. blending), observation of metabolism

· radiopharmaceuticals – direct irradiation of cancer tumours

· spas

· sterilization and disinfection (e.g. old wooden objects)

· leak tests

· test of material quality

· material modification – e.g. colour of glass, polymers production

· fire alarms, and many other
Radioactivity and ionising radiation – health and other effects

Absorbed dose

· absorbed energy per unit weight in J/kg (1 Gray = 1J/kg), D_T,R

· effect differ with intensity and type of radiation

Equivalent dose

· respects “quality” of radiation – radiation weighting factor w_R

o photons, all energies incl. gamma and X rays: 1

o electrons, all energies: 1

o neutrons: <10 keV 5

<100 keV 10

<2 MeV 20

<20 MeV 5

o protons: 5

o alpha particles, fission fragments, heavy nuclei 20

Effective dose

· respects type of organ affected, w_T

o gonads 0.2

o bone marrow 0.12

o lung 0.12

o …

o skin 0.01

o bone surface 0.01

Collective dose

· exposure of group of people or population (average dose times number of individuals affected)

Дата добавления: 2015-11-14