Re: The Search for a Real MicroR meter

[welch@CEBAF.GOV (welch)]

Hi Josh,

Bicron makes a microrem meter which we have used successfully for a number
of years.  This instrument "solves" the problem of energy dependence of the
NaI due to its 'tissue equivalent' plastic scintillator and therefore reads
in actual micro-REM, not R.  The lowest range is 0-20 microrem/hr which is
perfect for background surveys (normal bkg is ~50% of scale).

These go for around $1500 but I don't have exact price.  I'm not familiar
with the Victoreen.  I agree with your general opinion on Victoreen meters.
The Bicron instrument has held up well under normall field use conditions.
The only problem we've had is that severe shock (or repeated thermal
"cycling") will tend to cause the PMT to work loose from its base.(easily
fixed in < 1 minute).
Good luck in your search.


THIS IS NOT AN ENDORSEMENT OF THE PRODUCTS MENTIONED, MERELY A DESCRIPTION
OF SITE SPECIFIC EXPERIENCE.   ALL STATEMENTS ARE MY OPINION AND DO NOT
REPRESENT THE OPINIONS OR POSITIONS OF ANYONE ELSE.

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>        We've recently decided to aquire a microR meter mostly for use in
>spot checking radiation levels just outside of our controlled area.  As I
>went through the catalogs of instruments I found that most are NaI crystals
>with just a regular scalar attached to them.  We're a small reactor
>facility, since we deal with a wide range of isotopes calibrating an
>instrument for a single nuclide is not an option.  A few SCA's built into
>the meter might work, but it's not ideal.  The Victoreen 450P is the only
>instrument I've found which actually measures dose in the microR range and
>it's an ion chamber.
>        So I have two questions.  Are there any other instruments availible
>which have real dose measurement capability in the microR/Meters?  Does
>anybody make a NaI based instrument which does a weighted average of pulse
>size? List price under $1000 is a big plus but I know that's asking a lot.
>        Second I'd appreciate any feedback about the Victoreen 450P.  On
>paper it looks quite nice.  I'm particular interested in how robust it is
>and how fast the response is.  Right now we're useing a CDV-718 and it's
>response is too slow.  My limited experience with Victoreen instruments is
>that they are fragile.
>
>Many thanks in advance
>
>
>Josh Filner (jfilner@reed.edu)
>Reed College Reactor Facilty
>Portland, Or. 97202 (503) 771-1112 x7858
>http://www.reed.edu/~reactor
>
>
>
Keith Welch
Continuous Electron Beam Accelerator Facility
Newport News VA
welch@cebaf.gov