RE: Asking for opinions

["McDonald, Michael P" <mpmcdon@sandia.gov>]

Joe,

How about a couple of control badges?  If you can document background (even
due to rad material being parked next to the building and glass window) by
using control badges, why even worry about the glass vs. concrete shielding
values.  If you must make a determination of sorts, tape a couple of control
badges to the glass window and a couple of control badges to the concrete
wall.  No need to calculate or assess, and you'll be able to substantiate
the claim "where an HP approximates a mostly glass wall as a concrete wall
for shielding calculations."  Now, to answer the question asked, "How would
you interpret a case where an HP approximates a mostly glass wall as a
concrete wall for shielding calculations?". Depending on the glass type and
the concrete/block type, the "management type CHP" may be 100% correct in
his/her assessment.  Have you tried to find the appropriate
shielding-thickness values for those two materials?  No opinion is really
necessary!  Besides, who am I to judge another's assessment without first
looking through all the factual information gained?  Give the assessor the
benefit of the doubt until proven wrong.

Michael McDonald, CHP, RRPT
Sandia National Laboratories, NM
mpmcdon@sandia.gov
505-844-0653

-----Original Message-----
From: Archer, Joe [mailto:archerj@wipp.carlsbad.nm.us]
Sent: Friday, September 10, 1999 1:52 PM
To: Multiple recipients of list
Subject: Asking for opinions


A situation came up at our facility and I am interested in getting a general
consensus as to how to interpret the issue.

We had a TLD rack at the entrance to our facility where people put their
TLDs when they leave the site. This rack is a vertical board between 3 & 6
feet above the floor. 3 feet in front of the rack is a wall. The wall is 16
inch thick concrete from the floor to about a height of 3 feet and glass
from 3 to 7 feet above the floor. If you are standing at the TLD rack
looking out, your 135 degree field of view would be obstructed by two
concrete door jams about a foot wide each and the rest would be glass.

A concern was raised that radioactive material would be routinely parked
about 10-15 feet outside the glass and that this might dose the TLDs
unnecessarily. Two independent assessments by Rad engineers (one a CHP)
concluded that between 20-40 mrem per quarter may be absorbed by the TLDs
and that moving the rack was a reasonable precaution. This actually has some
relevance considering the collective dose goals of the site.

A management type CHP wrote up an analysis that assumed that the mostly
glass wall was approximated by a 16 inch thick concrete wall and he
concluded that the TLDs would get no dose. The question I would like
RADSAFERs to comment on is "How would you interpret a case where an HP
approximates a mostly glass wall as a concrete wall for shielding
calculations?". Although there is no human health issue involved, would this
border on being or is it blantantly unethical?.  Obviously, reasonable
people can disagree but for the purposes of this discussion, give your
opinion based on the assumption that you could see the radioactive material
from the TLD location and 100 or at least 99 out of 100 people would agree
that the only thing directly between the source and the TLDs was a pane of
glass.

Thank you to all who chime in.
Joe Archer


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