Re: Skin Dose Assessment from Whole Body Contamination Meters from No

[JSBland@aol.com]

John,
I have been working with a PWR utility developing a method for correlating 
noble gas exposure (and associated uptake) with a BNC SMART 905 NaI gamma 
spec detector.  Our experience is that individuals exiting containment, 
shortly after reactor shutdown and prior to containment purge, will alarm the 
whole body exit monitors.  The method we are developing will allow for the 
assessment of the noble gas (mostly Xe-133) uptake and reconcile the whole 
body monitor alarm (without having to retain the individuals unnecessarily 
until offgas or decay).  

The uptake modeling is based on a paper in Radiation Protection Dosimetry 
(Vol. 22, No. 1, 1988) by Peterman and Perkins.  I am using MATHCAD to solve 
the interlinked differential equations.  This approach allows for an 
assessment of the individual's uptake as a function of airborne levels, 
exposure time, and exit time.  This model will give the activity level for 
the key organs.  We are coupling this organ burden with MCNP modeling for 
calculating a monitor response. 

We have done limited testing of this modeling with actual data, but more is 
planned (and needed).  We believe this modeling provides a very defensible 
approach to the assessment and release of individuals after a containment 
entry with high noble gases.  This approach may also be applied in reverse to 
correlate a skin dose, but this is not needed since we have the measured 
noble gas concentrations in containment prior to entry.  

Hope to get something more formal (paper or presentation) in near future, but 
still need to do some work.  If you have any specific questions, let me know.

J. Stewart Bland, CHP
JSB Associates
Annapolis, MD  USA   
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