RE: Instrument Repair/calibration -Reply

["Lavera, Ron" <Ron.Lavera@nypa.gov>]

Regarding the instrument repairs :

I believe that care should be exercised when changing detectors in the
field.  GM detector dead times can vary with the result that high end
response can change to a value outside the calibration window.

Regarding the cable replacement, provided that the instrument is
equipped with a cable that meets the manufacture requirements, i.e. the
correct RG specification, and you don't change the length and you have a
reference source check value for comparison purposes ( preferably on all
ranges ) then you should be OK.

The reference to N323A is a good reference to keep in mind.

Another consideration is how well your overall program will be viewed if
your maintenance/calibration methods are not tight and you are taken to
court for a radiation liability case.  Even though your program may be
technically adequate, you may have a lot of fun and spend a lot of money
trying to convince the judge/jury.  An ounce of prevention ...

... mine and mine alone ...

Ron LaVera
lavera.r@nypa.gov

-----Original Message-----
From: Michael S Ford [mailto:MFORD@pantex.com]
Sent: Monday, January 04, 1999 9:43 AM
To: Multiple recipients of list
Subject: Instrument Repair/calibration -Reply


Joey,

Unless you have a well-documented basis for changing out
instrument components (with the exception of batteries), I would be
cautious in assuming that you don't need to recal.  Many people
would interpret a cable replacement as maintenance (albeit minor).

If you get reference readings on multiple scales prior to each use,
you might be on better technical footing.  A single scale reference
reading might not catch minor changes in system performance that
a cable change could introduce (e.g., impedance deltas).

I have had different experiences than Jim Kost pointed out,
especially with regard to cable lengths.  However, a great deal of that
could be attributed to instrument and cable quality.

ANSI N323A-1997 states the following:  "4.9 Calibration Frequency...
Calibrations shall be scheduled after any maintenance or
adjustment that can affect instrument performance.  Exchange of
detectors in the field shall be permitted only after a specific
procedure, such as the one described in 4.2.2, has been
documented and implemented."

My advice would be to contact your local regulator and make sure
they are comfortable with your (well-documented) practice.

v/r
Michael
*************************
Michael S. Ford, CHP
Texas Radiation Advisory Board
Address:
Radiation Safety Department
Battelle Pantex
Amarillo, TX
806.477.5727 phone
806.477.4198 fax
mford@pantex.com
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