[ RadSafe ] Fwd: Feild instruments for low activity gamma in soil

Chris Alston achris1999 at gmail.com
Tue Jul 8 16:49:44 CDT 2014


The FIDLER (Field Instrument for the Detection of Low Energy
Radiation) NaI probe was designed for this purpose, or more exactly,
to look for, e.g., Am-241 from Broken Arrows.  It works perfectly well
for higher E emissions; the crystal is only 1 mm thick, so it is most
efficient up to ~ 100 keV and you pick up nothing directly over about
350 keV (as best I recall), but there is plenty of scatter down from
higher energy photons, and the window is thin enough that you can read
high-E betas.  Bicron used to sell it as the Model G5.  Saint-Gobain
bought their detector business, quite some time ago, but was still
using the brand name as recently as about four years back, so I would
give them a call.

A 2x2" NaI probe like the Ludlum 44-10 also works well.  The advantage
to the FIDLER is that it sees basically nothing but what is directly
in front of it, or directly above it, because the crystal is so wide
(5 inches) and thin.


P.S.  It has been used on more than one DOE remedial action project.

---------- Forwarded message ----------
From: Owen, Austin Andrew <owenaa at oro.doe.gov>
Date: Tue, Jul 8, 2014 at 1:55 PM
Subject: [ RadSafe ] Feild instruments for low activity gamma in soil
To: "The International Radiation Protection (Health Physics) Mailing
List" <radsafe at agni.phys.iit.edu>

Does anyone know of a field instrument capable of detection of 7
pCi/gm gamma in soils for Thorium remediation.  To be used in Northern
Illinois with a higher than average Rn background?
If so, has DOE or EPA approved use of instrument to meet free release
criteria and/or screening for lab analysis.
I would also be interested in any previous technical papers used to
justify use of instrument or combination of scanner and scalar.

Andy Owen
Health Physicist
Engineering and ISC Services Division
(865) 576-0852
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