At Beaver Valley, we use +20%. When we dose TLDs and EADs to Cs-137 on a
phantom, the EADs will read 20% higher than the TLDs. However, the
response difference in the field is not 20%. Typically, when we compare
collective personnel dose the difference is 5-10%,
We are a two Unit site - zinc for about 6 years at one Unit and just
recently at the other. Our non-outage dose is very low. For outages, we
have seen some difference between the Units, however this may be due to the
differences in the work that is performed - e.g., under head inspection &
repair work (with significant dose) is done at one Unit and not at the
other. The collective dose agreement is this case is more like 0-5%
difference.
We try to maintain the +5-10% collective dose field bias to minimize the
number of cases where the TLD dose exceeds the EAD dose for an individual.
When the individuals EAD dose is lower than the TLD dose, we view this as a
potential dose control issue, since dose control is based on the EAD dose
(until TLDs are processed). If a bias is established so that collective
dose shows no difference, you should find that about 50% of the individuals
will have a TLD dose that is higher than the EAD dose. We selected +20%
for the EAD calibrations based on years worth of TLD/EAD comparisons. For
us, this minimizes the number of non-conservative EAD dose situations and
does not introduce an excessively high bias for the monitoried population.
"Courtenay,
Christopher C"
<Christopher.Cour To
te...@duke-energy "[email protected]"
.com> <[email protected]>
Sent by: cc
owner-power...@hp
s1.org Subject
Powernet: Electronic Dosimeter Bias
12/14/2010 02:37
PM
Please respond to
[email protected]
Duke Energy would like to know the following:
1. Do you bias your EDs to over-respond in the field?
2. What bias do you apply if you do? (5%, 10%, etc)
3. Have you noticed a change in ED response due to changing
plant conditions (Co58/Co60 ratio changes due to Zinc injection, etc)
or specific jobs (weld overlay, alloy 600, etc)?
Point of reference – Duke uses the DMC2000S from Mirion.
Chris Courtenay
Engineer, Duke Energy
980-875-5005
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
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