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Re: Weighting Factor for Hot Particle Skin Doses per Cm^2
Dear Colleagues
The issue of how to weight localised skin doses was considered in
some detail in the UK by the NRPB and published as:
Assessment of skin doses. M P Little, M.W Charles, J W
Hopewell, A Mayall, D Lloyd, A A Edwards, C Sharp and J R
Cooper. Documents of the NRPB, 8(3) 1997
The issue is not necessarily straight forward. ICRP (publication
60) recommended a tissue weighting factor for skin of 0.01. This
is for a uniform whole body skin exposure. One might think that
for a small area skin exposure the weighting factor would be
reduced pro-rata (since skin cancer risk might reasonably be
expected to be proportional to the number of cells exposed and
therefore to the area of skin exposed). There is however a
complicating factor which arises because skin cancer risk is
dominated by those parts of the body that are not usually exposed
to solar UV and there is a generally accepted synergism between
UV and ionising radiation in the case of radiation induced skin
cancer. The NRPB document discusses this in some detail and
gives separate weighting factors for the UV-exposed and non-UV
exposed parts of the body. The NRPB document is one which
provides advice. As far as I am aware it has not found its way into
regulations and has not been formally endorsed by the ICRP. It
may however provide a useful starting point if you wish to revisit
the issue.
Monty Charles
**************************
On 23 Jan 2003 at 19:07, Carol Marcus wrote:
> Jan. 23, 2003
>
> Dear Radsafers:
>
> This question is probably for health physicists at nuclear power plants.
>
> If you have a worker who received a face skin dose from a single "hot
> particle", expressed as rad/cm^2, what weighting factor do you use in
> adding it to his other doses? While the original Part 20 specifies a
> weighting factor of 1.0 for a head dose, the Statements of Consideration
> for Part 20 state that "The use of other weighting factors for external
> exposure may be approved on a case-by-case basis upon request to the NRC."
> (Fed. Reg. 56(98):23369; May 21, 1991.)
>
> I assume that a case must have been made to NRC for "hot
> particles". Anyone know what the weighting factor is?
>
> Much obliged for your help in advance.
>
> Ciao, Carol
>
> Carol S. Marcus, Ph.D., M.D.
> <csmarcus@ucla.edu>
>
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>
Dr Monty Charles
Reader in Radiation Physics
Head of Radiation Biophysics Group
School of Physics & Astronomy
The University of Birmingham
Birmingham B15 2TT
Tel +44 (0) 121 414 3483
Fax +44 (0) 121 414 4725
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