Re: RADSAFE digest 3135

["D. Kosloff" <dkosloff@ncweb.com>]

Sandy,

Here is what the NUREG that I have says about the transit exposure:

5. ESTIMATION OF TRANSIT EXPOSURE

Field dosimeters receive exposure both while in transit to and from the
placement contractor and while in storage at the contractor's facility, as
well as while they are at their monitoring locations.  To determine the
field exposure, it is necessary to estimate this additional exposure, which
is designated transit exposure.

Two control dosimeters are sent to each contractor to estimate the transit
exposure.  Control #1 remains unshielded, except when stored in the
NEC-provided lead cask at the contractor's facility.  This cask provides
2.75 inches of lead shielding.  Control #2 is no longer used.  Control #3 is
used to indicate whether a significant exposure was received by the
dosimeters while in transit from the NRC office in King of Prussia, PA, to
the contractors.  It is shipped unshielded  with the new batch of dosimeters
to the contractor and returned unshielded with the previous quarter's
dosimeters.  If an unacceptably high transit exposure is detected by this
dosimeter as a result of its shipment to the site, a new set of field
dosimeters will be sent to the contractor for an early exchange.

The exposure to Control #1 is the sum of the transit exposure and the
exposure received while in storage during the quarter.  The exposure rate
during storage is estimated to be 0.0825 + or - 0.0265 mR per day and is
based on previous measurements.  For information on how the exposure rate in
the cask was previously estimated, refer to Appendix A of NUREG-0837, Vol 2,
#4.  The Transit exposure to the field dosimeters is estimated by taking the
difference between the exposure measured by Control #1 and the exposure
calculated to have been received by Control #1 while in storage in the
contractor's lead cask.  The storage exposure rate is essentially due only
to the cosmic ray component of the local natural background radiation.

Likely sources of transit exposure include shipments of medical and other
radioisotopes in the mail, as well as natural terrestrial and cosmic
radiation.
-----------------------
By the way we lived in Costa Mesa for a few years, across the street from
Orange Coast CC.  I used to work for Fluor in Irvine.  Both my daughters
were born at Hoag Hospital.  I don't remember where Hyland is.

Don Kosloff dkosloff@ncweb.com
2910 Main St, Perry OH 44081

----- Original Message -----
From: Sandy Perle <sandyfl@earthlink.net>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Saturday, April 29, 2000 10:53 AM
Subject: Re: RADSAFE digest 3135


> Thanks for the information. The only dose other than background
> should have been the transit dose, depending on the distance from
> the NRC lab RT to the monitoring point. The clarification that the
> dose reported was net is appreciated. That net dose is still
> essentially the natural background in the area.
>
> Keeping a "control" in a lead safe in some cases can cause a
> problem. I've observed facilities keeping their controls in a lead
> safe, and those controls actually had a higher dose than the
> personnel doses received by the staff. I'm sure that the NRC facility
> did characterize the safe to ensure that it was "contamination free".
>
> --------------------------------------------------------------------------
--------
> Sandy Perle Tel:(714) 545-0100 / (800) 548-5100
> Director, Technical Extension 2306
> ICN Worldwide Dosimetry Division Fax:(714) 668-3149
> ICN Biomedicals, Inc. E-Mail: sandyfl@earthlink.net
> ICN Plaza, 3300 Hyland Avenue  E-Mail: sperle@icnpharm.com
> Costa Mesa, CA 92626
>
> Personal Website:  http://www.geocities.com/capecanaveral/1205
> ICN Worldwide Dosimetry Website: http://www.dosimetry.com


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