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RE: Neutron Survey Meter
I do not know the equipment, but "slow neutron survey meter" with an Am-241 source makes one wonder whether there is a Am-Be source of (fast) neutrons. The only such combination that readily springs to mind is a soil humidity meter which detects thermalized (slow) neutrons reflected from the moisture in the soil as a measure of soil humidity. The detector would probably be a BF3 tube, which effectively only sees the slow (reflected) neutrons. That would make it a "slow neutron survey meter" (for soil humidity). The question now arises what (gamma?) detector was used to investigate the source. The second peak, apart from the 60 keV Am-241, could be due to (fast) neutron scattering in the detector, e.g. in a Ge detector (I seem to remember 492 keV?). Much less credible would be (slow) neutron capture in boron (480 keV doppler broadened gamma peak) and neutron capture in hydrogen (2.2 MeV). This type of source is long-lived (Am-241 has a halflife of 432y) and should be de!
co!
mmissioned by a competent authority. Taking a very long shot.
Chris Hofmeyr
chofmeyr@nnr.co.za
-----Original Message-----
From: Flanigan, Floyd [mailto:Floyd.Flanigan@nmcco.com]
Sent: 20 August 2003 02:55
To: Kevin Hughes; radsafe@list.vanderbilt.edu
Subject: RE: Neutron Survey Meter
Standard questions:Did you check your print-out for the possibility of summation peaks and escape peaks and correlate the energies to germane energies which fall off scale hi/lo? Beryllium seems unlikely. You probably already thought of all of this before so consider this as not being an affront to your process but rather my thinking 'out loud'.
Floyd W.Flanigan B.S.Nuc.H.P.
-----Original Message-----
From: Kevin Hughes [mailto:K.H.Hughes@aston.ac.uk]
Sent: Wednesday, August 20, 2003 4:00 AM
To: radsafe@list.vanderbilt.edu
Subject: Neutron Survey Meter
To All Radsafers
I read with interest earlier postings of similar requests for information:
We too have an old "Slow Neutron Survey Meter" made by Ekco Electronic Ltd
- Type N578M, which (as some of you will know) contains a radioactive
source. Our initial spectral investigations of the source indicate 2 peaks,
1 being identified as 241Am and the other remains unknown (possibly
Beryllium!).
The reason for our request is that we would like to dispose of the source,
but are unable to until we can identify the other unknown peak and
determine the source activity - there are no labels/markings either on the
meter itself or the source to indicate the nature of the radioactivity or
it's activity.
Any help whatsoever would be much appreciated.
Kind Regards
Kevin Hughes
Site Radiation Officer
Aston University
Birmingham
England
k.h.hughes@aston.ac.uk
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