Diablo Canyon's responses are below. 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: 805.545.2618| [email protected]<mailto:[email protected]>
From: [email protected] [mailto:[email protected]] On Behalf Of
LITTLE, DOHN V
Sent: Friday, February 03, 2012 8:08 AM
To: '[email protected]'
Subject: Powernet: TLD wearing, TLD vs EAD comparision
Fort Calhoun would appreciate your input about TLDs.
If you have any procedures that address these items and would not mind sharing,
you can email them to [email protected]<mailto:[email protected]>
1. Does your site use some type of a jig to standardize the position of a
worker's EAD and TLD or do you just provide guidance to the worker to keep the
EAD and TLD together (such as within a hands width of each other and on the
front of the body between the waist and head)
Yes. We use something we call a geometry card. It is a piece of lamicoid with
slots for the ED and TLD
2. If you use a jig, did/does its use improve how your TLD vs EAD results
match up.
We started using it when we still used Dositec EDs. It was a tremendous help
there. Now, I think it's big advantage is that it takes geometry issues out of
the equation when we investigate mismatchs
3. If you move dosimetry from the chest location to another location such
as the head or Thigh when they are the highest exposed body part, do you record
that movement somewhere (survey map, log, etc.)?
Yes. TLD/ED relocation is documented in job history comments which is treated
as a part of a survey or permit and is retained accordingly.
4. What is your TLD wear period and minimum reporting level for the TLD?
(example, 6 month wear period, 5 mrem reporting level)
Our wear period varies. We change TLDs out three times a year, but move the
times around to support outages. Our fade studies allow support a six month
changeout cycle. Our minimum reporting level is 5 mrem
5. Is the INPO and ANI criteria the only criteria you use for determining
when to investigate TLD vs. EAD results or do you have additional criteria you
apply? What is the additional criteria you use? (INPO and ANI criteria -
investigate if either TLD or EAD is greater than 100 mrem and > 25% difference
between readings)
We formally evaluate at the INPO level. We also informally (and sometimes
formally) evaluate the following criteria:
1) TLD dose and no RCA entries - false positives are possible with our
aggressive reporting limit.
2) PED > 15 mrem and 0 TLD. At this time we round estimated dose at 0.5. We
plan to start using unrounded dose soon. That number will probably change
after we get some experience under our belts.
3) +/- 2.5 SQRT of the TLD reading - "Lantz" method. We are big proponents of
the Mike Lantz method and use it every period.
Thanks,
Dohn
Dohn Little
Radiation Health Specialist - Dosimetry
[email protected]<mailto:[email protected]> - (402) 533-7162
Admin Building FC 2-1
OPPD - Fort Calhoun Station
9610 Power Lane
Blair, Ne. 68008
[Description: cid:[email protected]]
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