This is a very interesting and timely topic for Diablo Canyon.
Hopefully my write up makes some sense. I have attempted to bundle a
lot of information into maybe too few words.
Background information:
We use Thermo MK2 with Sentinel software. Dosimeter maintenance is
administered through EMDS2. We process our own Panasonic TLDs. Thermo
calibrates our EDs. A portion of the EDs are source checked daily to a
NIST traceable irradiator. The EDs are irradiated against a phantom
during these checks. At this time, estimated dose is rounded at RCA
logout. TLD LLD is 7 mrem. TLDs are changed out at approximately 4
month intervals. Depleted Zn injection since 2006. New steam
generators 2008,2009. New heads 2009, 2010.
Duke's questions:
1) Yes
2) 10%
3) We have had a fairly constant gross ED to TLD comparison of
approximately 2-3% ED over response in outages and 20% ED over response
in non-outages. I have seen a change in our numbers since we changed
out steam generators although I still have limited data. For our last
two outages we have seen a 4-5% ED over response. It is still way to
early to draw any conclusions.
Robinson's questions:
We currently round dose and have for our entire operating history. We
are considering changing in early 2011, however after talking to our
software vendor (PTI) about the recent Plant Hatch OE32422 both PTI and
Diablo will be doing some further testing regarding the impacts and
possible error traps in the transition to unrounded dose.
Happy Holidays to all,
Linda
Linda M. Sewell, CHP
Principal Health Physicist
Pacific Gas & Electric Company
Diablo Canyon Power Plant
MS 119/1/117
PO Box 56
Avila Beach, CA 93424
P: 805.545.4315 | F: 805.545.26128| [email protected]
________________________________
From: [email protected] [mailto:[email protected]] On Behalf
Of Courtenay, Christopher C
Sent: Tuesday, December 14, 2010 11:37 AM
To: [email protected]
Subject: Powernet: Electronic Dosimeter Bias
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."
