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RE: radiographer "overexposure"
George,
I hope that someone from SONGS will correct any errors in what may well be
my flawed recollection:
The extremity dosimeter result that indicated 513 rem (or thereabouts) was
strongly believed to be an artifact of excess adhesive from tape used to
either secure the dosimeter, or as part of the protective clothing scheme.
(Recall that because of the problems with NRC dose limits at the time, any
NPP with a real or potential hot particle problem resorted to pretty
draconian protective clothing and survey requirements, most of which were
not at all ALARA.) This theory was supported by very high residual readings
on the extremity element (well in excess of 10% of the processed dose).
SONGS staff and their consultants presented a pretty convincing technical
case, but I do not recall the ultimate resolution on the issue of record
dose.
In an unrelated couple of events from the 1980s, several individuals working
in the circulating water or condenser systems at a couple of plants
experienced erroneous TLD results from a chemical reaction between the TLD
material and hydrogen sulfide produced from biomass debris present in the
system.
Bottom line -- you can have a very good dosimetry system in place and still
run into unexpected confounding factors that will cause trouble for the
well-intentioned, but possibly unsuspecting user. That's what makes me
nervous about the recent trend to take a Wal-Mart approach to dosimetry --
simply treating the dosimeter as a commodity to be obtained from the lowest
bidder.
George J. Vargo, Ph.D., CHP
Senior Scientist
MJW Corporation
http://www.mjwcorp.com
610-925-3377
610-925-5545 (fax)
vargo@physicist.net
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of George Cicotte
Sent: Wednesday, July 30, 2003 1:13 PM
To: radsafe@list.vanderbilt.edu
Subject: RE: radiographer "overexposure"
Does anyone recall the 513 REM extremity dose incident at San Onofre in the
late 1980s?
(Anyone at SONGS please correct me - going on recollection rather than
review)
To refresh everyone's memory, the processor sent an email report to SONGS
that said the dose was something like 13.333 REM. The REM column had only
two places. The "flag" portion of the reporting program took its' input
from the inserted (hundreds column truncated) entry, rather than from the
absolute value that was the input to that entry, so the reported value
didn't calculate out to over 75% of the extremity dose, and the report
didn't highlight it as intended. SONGS, not being aware of the program
fault, didn't even ask for a reevaluation until later.
The later, written report had the third digit, showing 513.333 (or whatever
the mrem remainder was). Eventually, the investigation cast doubt on
whether the 513 was a good figure, but that's beside the point of whether
the information was relayed in a manner that correctly alerted the user.
Supposition:
If the 1,423,000 mrem reported may be the result of a simple reporting
problem, rather than a processing problem, the QA program for the dose could
be just fine. Perhaps the film badge was read as 1423 mrem, but the
printout shows a multiplier, or the program for some reason screwed up place
value.
I have no personal knowledge of this incident, but I do have quite a bit of
experience in how computers can make our lives and careers incredibly
easier, until we let the computer do our thinking.
I would also caution, from personal painful experience, against assuming we
actually know enough about this to speak intelligently, or to criticize the
regulators, who may have looked at the incident and may contemplate
enforcement action or other followup, but with the processor rather than the
licensee, who is allowed to rely on the processor in most instances
(assuming they're NVLAP).
Respectfully,
George R. Cicotte
DISCLAIMER: I haven't asked my employer what he thinks about this, and it
is, after all, opinion rather than learned study.
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