RE: MicroShield Exposure Estimates

["Heinmiller, Bruce" <heinmillerb@aecl.ca>]

There are variations in reported values of both the specific gamma-ray
constant and in the exposure rate constant for Ra-226.  These variations
have arisen for a number of reasons, which could include, I believe, any of
the following:

- confusion between the above two quantities
- variation in the filtration assumed in calculations and in experiment
- uncertainties in the gamma-ray spectrum used in calculations
- variations in the values assumed for muen/rho and W-bar for air
- differences in the gamma-ray and X-ray cut-off energies used
- differences in Pb-210 grow-in
- error in the assumed specific activity of Ra-226
- other uncertainties in experimental conditions

The assumed filtration is important, and I believe that the 0.825 R h^-1 m^2
Ci^-1 figure assumes filtration through 0.5 mm Pt (10% Ir), (and assumes the
historical specific activity of Ra-226 of 1 Ci/g, which is no longer quite
correct).

It doesn't surprize me at all that a code would derive a value 10% larger
than 0.825 for a given set of exposure assumptions, and I don't see the
discrepancy as a problem in this regard.

Bruce Heinmiller CHP
heinmillerb@aecl.ca

> ----------
> From: 	SENES Consultants Limited[SMTP:senes@senes.on.ca]
> Reply To: 	radsafe@romulus.ehs.uiuc.edu
> Sent: 	Thursday, April 15, 1999 9:15 AM
> To: 	Multiple recipients of list
> Subject: 	MicroShield Exposure Estimates
> 
> I would have sent this question to MicroShield (MS) (Grove/Framatome),
> but they don't accept registration on their WWW users' group unless you
> have the <underline>latest </underline>version.  They also haven't
> responded to my direct E-mails.
> 
> 
> We often do calculations involving NORM radionuclides and have found that
> MS appears to give  exposure estimates that are larger (by 20% or more)
> than one would obtain from other references e.g.. for Ra-226 in soil.  In
> fact,  the MS estimate for a point Ra-226 source (and decay products) is
> about 10% larger than the 0.825 R/h per Ci at 1 m given in the
> Radiological Health Handbook.
> 
> 
> Is this the "latest" value for a point Ra-226 source?  Has anybody else
> found similar discrepancies with MS?
> 
> 
> 
> Leo M. Lowe, Ph.D.
> 
> Senior Health and Environmental Physicist
> 
> 
> SENES Consultants Limited
> 
> 121 Granton Drive, Unit 12
> 
> RICHMOND HILL, Ontario
> 
> Canada L4B 3N4
> 
> Tel:  (905) 764-9380
> 
> Fax:  (905) 764-9386
> 
> Email Address:  llowe@senes.on.ca
> 
> Web Site:  http://www.senes.on.ca/
> ************************************************************************
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
> 
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html