RE: Anyone hear of "flawed rad detectors"...

["Walker, Scottie" <swwalke@sandia.gov>]

I would submit that the dosimeters in these cases are all performing as
intended.  If a flaw exists, it is in the application of a technology with
the lack of an adequate technical basis.  The end user has the ultimate
responsibility for the accuracy of the dosimetry results, even if they are
using a vendor such as ICN, Landauer, etc.  Unless the user has provided the
vendor with the appropriate field correction factors, there is no way that
any one dosimeter could possibly account for all neutron or beta energies.

We don't use CR39 at our lab, but for our TLDs we can easily see a x10
difference in the neutron dose equivalent calculation if the wrong dose
conversion factor is applied to the data (reactor leakage spectrum versus
PuBe spectrum).  And a difference of x50-60 is easily possible for beta
exposures to extremities if the wrong correction factor is applied.

Scottie Walker
External Dosimetry Project Leader
Sandia National Laboratories
P.O. Box 5800, MS-0651
Albuquerque, NM 87185-0651
swwalke@sandia.gov
(505) 844-5241 (phone)
(505) 844-8313 (fax)


-----Original Message-----
From: Sandy Perle [mailto:sandyfl@earthlink.net]
Sent: August 25, 2000 2:12 PM
To: Multiple recipients of list
Subject: Re: Anyone hear of "flawed rad detectors"...


While I don't have any data regarding the assertion that the beta and 
neutron dose may be underestimated by as much as a factor of 10, I 
can state that there is most likely an under-estimation. I can say 
this based on my experience with the United Kingdom criteria for 
"Approval of Dosimetry Service." We had to explain in extreme details 
why it was appropriate for us to utilize a beta correction factor for 
not only whole body dosimetry, but for extremity monitoring as well. 
The expectation is that the dosimeter should simply report the H(p)10 
and H(p).07 dose without any corrections what-so-ever. We provided 
data demonstrating that a beta correction, when the energy is known, 
provides for SDE dose assessment within +/- 3% or so. Again, it took 
months of documents being sent back and forth, for the HSE to accept 
our beta correction factors for use for whole body and extremity 
dosimetry. We now have the Certificates for "approved Dosimetry 
Service" in the U.K.

Therefore, based on our experience, there is some truth in the 
article. The degree of truth can't be determined since one would have 
to know what dosimetry was used, and who processed the dosimeters.


------------------------------------------------------------------------
Sandy Perle					Tel:(714) 545-0100 / (800)
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Director, Technical				Extension 2306

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