Re: La Hague

[kmq@cosmail1.ctd.ornl.gov (Kim McMahan)]

At 09:25 AM 2/25/97 -0600, Alden Tschaeche wrote:
>Clearly the internal dose to an organ would be higher per unit activity
>in the organ for babys and children than for adults because the mass of
>the organs is less.  But, the statement to which I refered talks,
>apparently, about external radiation, not internal.  So, although I
>agree with your statements about internal exposure, that does not seem
>to be the subject under discussion here.  Al Tschaeche xat@inel.gov
>(until 2/28/97)

Al,

Please re-read Dr. Julian Gibbs' response. He addressed the external
dosimetry considerations. Here's another version of what he said:

Recall that (absorbed) dose is energy absorbed per unit mass. Since photons
are attenuated as they pass through the body, the dose to a unit mass of
tissue on the incident side of the body is greater than the dose to a unit
of tissue on the opposite side. Admittedly, for high energy photons the
difference is not great, but for lower energy photons (<100 keV or so) it
becomes significant. Since children are not as "thick" as adults, the
attenuation is less and therefore the average dose to any organ (which is
then weighted and summed to get the EDE) is greater.

What this might mean to emergency response planners is that it would be
better to choose "thicker" volunteers for recovery operations (uh, oh, did
I say that?)  :-o



Kim McMahan, CHP
Office of Radiation Protection
External Dosimetry Group
Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN  37831-6290
Phone: (423) 576-1566
Fax:   (423) 241-5744
e-mail: mcmahankl@ornl.gov