DCFs

[Michael Stabin <stabin@npd.ufpe.br>]

>
> I did a quick run on the CINDY code and got a result of 4.4 E8 rem/curie
for the
> inhalation of Class-W Pu-239.  It looks like FGR 11 and the CINDY code
pretty
> much agree on this one.  I do not know the source or accuracy of the
DOE/EH-0071
> values.

I'm also not familiar with the DOE values.  However, Dr. Kearfott of
Michigan participated in a study a few years back that showed that DCFs
between ICRP 30, 10CFR20 and the FGR can vary quite a bit, owing mostly to
roundoff errors in jumping between Ci and Bq units, with DCF values using
only using 1 or 2 sig figs.  DACs and ALIs also may not be consistent with
each other.  Even the original ICRP 30 numbers suffer a bit in this
roundoff - for example, I estimate that the real ALI for ingestion of P-32
should be 2.4E7 Bq, which comes out in ICRP 30 itself as 2E7 Bq (rounded to
1 sig fig).  The FGR and 10CFR 20 then have the value as 600 uCi.

This can of course become problematic when you have a situation (like at the
NIH and at MIT in recent memory) where you have an intake close to the ALI,
and you are playing the "bright red line" game with the NRC.  First,
everyone knows that the calculated values of intake and dose have big
uncertainties, and that your estimate of intake based on one or more
bioassays has a big uncertainty.  But if the reg is 600 uCi and intake comes
up as 610 uCi (actually 601 will do), you are over the line. If the line
itself has this much uncertainty because of rounding errors (570? 600?
650?), it would seem unfair to me that one would have to pay a fine in this
circumstance.



Michael Stabin, PhD, CHP
Departamento de Energia Nuclear/UFPE
Av. Prof. Luiz Freire, 1000 - Cidade Universitaria
CEP 50740 - 540
Recife - PE
Brazil
Phone 55-81-271-8251 or 8252 or 8253
Fax  55-81-271-8250
E-mail stabin@npd.ufpe.br

"Quantum Mechanics: The dreams stuff is made of"
- Steven Wright


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