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Radiation weighting factors

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The probability of stochastic radiation effects depends not only on the absorbed dose, but also on the type and energy of the radiation causing the dose. This is considered by weighting the absorbed dose with a factor related to the radiation quality. In the past this factor was known as the quality factor. For photon and electron radiation, the radiation weighting factor has the value 1 independently of the energy of the radiation and for alpha radiation the value 20. For neutron radiation, the value is energy-dependent and amounts to 5 to 20.

Radiation type and energy

Radiation weighting factor WR

Photons, all energies

1

Electrons, myons, all energies

1

Neutrons

< 10 keV
10 keV to 100 keV
> 100 keV to 2 MeV
> 2 MeV to 20 MeV
> 20 MeV

 

5
10
20
10
5

Protons > 2 MeV

5

Alpha particles, fission fragments, heavy nuclei

20

Radiation weighting factor WR in accordance with Euratom basic standards 1996

The numerical values indicated above are valid legal EU-regulations for calculating the equivalent dose in an organ or tissue. In 2007 ICRP published a new set of radiation weighting factors (ICRP Publ. 103: The 2007 Recommendations of the International Commission on Radiological Protection) given below. These data are adopted in the proposal of the new EU Basic Safety Standards (European Commission, Proposal for a Council Directive laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, COM(2012) 242 final 2012-05-30 to be accepted by the Council of the European Union
eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=COM:2012:0242:FIN:EN:PDF

Radiation type

Radiation weighting factor WR

Photons, all energies

1

Electrons, myons, all energies

1

Protons and charged pions

2

Alpha particles, fission fragments,
heavy ions

20

Neutrons

A continuous function of neutron energy (see equation)

Radiation weighting factors (ICRP 2007)

Radiation weighting factors

Continuous function in neutron energy, En (MeV),
for the calculation of radiation weighting factors for neutrons

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