Re: Spectral Analysis

["Michael Kay" <makay43@home.com>]

Daren,

My first question is: was the spectrum taken at a distance far enough to

avoid saturating the detector? Probably a few feet minimum to get a valid

spectrum.



What does the source look like?

Is it a sealed source?

Are there any identifying marks or numbers on it? You can use optics to do

this from a distance.

Is the field isotropic? Or is there one direction with a higher reading

(which would indicate a window for a beta source).



One type of source that comes to mind is a Kr-85m beta source used in

industrial gauges.



If your intensity measurements are correct and not from flooding the

instrument, then it is too small to be a radiography source.

Neutron sources for moisture measuring instruments should have a gamma or

x-ray component.



All in all, more information is needed to make a better guess at what this

source contains.



Michael Kay, ScD, CHMM

Licensed Health Physics Consultant

State of Oregon



----- Original Message -----

From: "Perrero, Daren" <Perrero@IDNS.STATE.IL.US>

To: "'RADSAFE'" <radsafe@list.vanderbilt.edu>

Sent: Thursday, November 01, 2001 10:08 AM

Subject: Spectral Analysis





> This is definitely not my strong suite so any help here is appreciated.

The

> situation involves a field test using a portable MCA.  Field readings give

> dose rates of approximately 100 mr/h near contact and 10 mr/h at a foot

from

> a discrete source with no markings.  However a limited time (approx  5

min)

> NaI spectra out to 2.5 MeV does not show a discernible peak.   What type

of

> nuclide could be producing these readings?  If a beta emitter was here

> wouldn't there at least be an x-ray peak produced from the capsule

material?

>

>

> Eventually a lab quality spectra will be obtained and the mystery solved

but

> it would be nice to have some idea (or at least a couple of good guesses)

of

> what's being transported before it gets to the lab.

>

> Daren Perrero

> Health Physicist

> Illinois Department of Nuclear Safety

> (217) 785-9929

> perrero@idns.state.il.us

>

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