Re: LLD for Albedo Dosimeter

["Rob Gunter" <gunterrj@hotmail.com>]

Bob,

I believe what you want to find is the "Critical Level (Lc)".  This is 
the lowest dose that can be measured with 95% confidence.  Check out 
"L.A. Currie, 'Limits for Qualitative Detection and Qualntitative 
Determiation: Application to Radiochemistry,' Anal.Chem. 40, 586 (1968).  
This is the standard reference I have seen used.

good luck.

Rob Gunter

>I think I have an interesting puzzle for some of you math fans out 
there. I
>think I could figure this one out myself, but I find there just aren't
>enough hours in the day any more...
>
>So, I'm hoping someone out there can point me to a convenient reference 
as
>a shortcut.
>
>We use albedo TLDs (2 types, a loose disk LiF system and the Panasonic
>UD-802) in several different geometries to monitor area and personnel
>neutron dose. We have various moderating materials to use, and I'd like 
to
>determine the LLD for each dosimeter/moderator combination.
>
>The methods I have always used for LLD calculations use the background 
DOSE
>and the associated standard deviation as well as bias and standard
>deviation data for small, non-background dose measurements. We have
>developed dose conversion factors for a variety of neutron spectra, and 
I
>would like to determine the LLD for each. The traditional (NVLAP, 
DOELAP)
>calculation method doesn't really allow for what I want to do.
>
>For each dosimeter system, we can determine the average background 
SIGNAL
>for each element and the associated standard deviations. What I would 
like
>to calculate is the minimum detectable signal above background for each
>such element. These values could then be used with the dose conversion
>factors to determine the minimum dose that could be detected at each
>energy. I base this on the assumption that the minimum detectable 
signal
>attributable to neutron dose above natural background is a 
characteristic
>of the ambient background and the measurement conditions and devices, 
and
>once determined, this minimum detectable signal above noise can be used 
to
>calculate the neutron dose necessary to generate that signal at each
>neutron energy.
>
>Does anyone know of a good reference or two that I could look at for
>calculational techniques?
>




Robert J. Gunter, M.Sc. 
Health Physicist
ICN Dosimetry Service
ICN Plaza
3300 Hyland Avenue
Costa Mesa, CA  92626
Ph:  800 548-5100 X 2414
     +714 545-0100 X 2414
Fax: +714 668-3149
Email: rjgunter@icnpharm.com


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