Re: Samarium-153 -Reply -Reply

[FRAMEP@ORAU.GOV]

Wrt the following:

>A question about dose rate constants came up in our group recently.
>The Health Physics and Radiological Health Handbook lists the
>dose constant for I-125 as 7.432E-5 mSv/h/MBq at 1 meter.  That
>is about 275 mRem/h/Ci at 1 meter.   Amersham safety data sheets
>list it at 41 uSv/h/MBq or 152 mRem/h/Ci.  An unreferenced table
>apparently from the UCLA Office of Environmental Health and Safety
>dated 1971 lists it as 70 mR/h/Ci at 1 meter.  That one I know
>is effected by the difference between R and Rem at that energy.
>A program that I wrote to calculate the dose from photon energies
>branching ratios and mass energy absorbtion coefficients comes
>up with about 140 mRem.

>Does anyone have an opinion on what the real value is (i.e. with
>an error bar somewhat less than a factor of two)?  Is there this
>much scatter in reported values for other low energy emitters?

For what its worth, here's another number: 143 from a Mallinckrodt
table. I'd say that the range of values is due to two key factors

1. At low energies there is a lot of uncertainty about gamma/x-ray
intensities (yields).

2. It is often assumed that the source is encapsulated and that the
low energy stuff doesn't get out. Some folks ignore stuff below 30
keV while others might include anything over 10 keV.

Best wishes

Paul Frame