Thanks, Kevin
Duane Gore
Supervisor, Reactor Engineering
STPNOC
(361) 972-8909
From: Elam, Kevin
Scott [mailto:kselam@tva.gov]
Sent: Monday, July 14, 2008 9:02
AM
To: Greer, C. Dale;
pwrrm@retaqs.com
Subject: Re: [Pwrrm] Cycle Length
Prediction Error when usingWestinghouse1.5xIBFAs
My memory tells
me Exelon's Byron and Braidwood units were similar to what is described
below. Our Nuclear Fuels core designers assumed the end of core life
would occur when the design was at ~30 ppm. They can correct me if I am
wrong.
At Watts Bar, we
have the opposite experience. We get more energy out of the core than
predicted. (Remember, we have Trittium producing inserts that nobody else
has.) The following are estimates:
Cycle
6 +10 ppm (Mild CIPS)
Cycle
7 +20 ppm (Moderate CIPS)
Cycle
8 +40 ppm (No CIPS)
Cycle
9 +60 ppm (In progress at 3800 MWD/MTU)
Kevin S.
Reactor
Engineer
(423)365-8806
Pager
14211
From: Greer, C.
Dale
Sent: Monday, July 14, 2008 8:43
AM
To: Elam, Kevin Scott
Subject: FW: [Pwrrm] Cycle Length
Prediction Error when using Westinghouse1.5xIBFAs
Would you respond to Duane Gore at STP about this question?
From:
pwrrm@retaqs.com [mailto:pwrrm@retaqs.com] On
Behalf Of BRYSON, DAMON V
Sent: Monday, July 14, 2008 8:30
AM
To: PWR Reactivity Management
Subject: Re: [Pwrrm] Cycle Length
Prediction Error when using Westinghouse1.5xIBFAs
At VC Summer we have
been having cycle length prediction errors for many cycles, with at least 4
different IFBA concentrations. Since we do our own core design with APA,
we have done a lot of investigations of the problem. W also did a root
cause on why so many units are having problems with this. That’s
part of the reason behind the upgrade to ANC 9.0. Unfortunately, not all
of the reactivity errors are going in the same direction, so when they
benchmark ANC, they try to hit the average. A major factor in this issue
is each utility’s method for determining calorimetric reactor power.
In other words, each unit may be operating at a different place within the ~2%
calorimetric uncertainty, and a 1% change in core power will cause a reactivity
change of around 35 ppm at the end of the second fuel cycle (at least in our
unit – 3-loop core at 2900 MWth).
We tend to have a
reactivity shortfall of about 300-600 pcm at the end of cycle. In the
last few cycles we have implemented a bias factor on the eigenvalue, based on
the average of the last 3 cycles. This has given us fairly good results,
as long as there are no core modeling or fuel design changes.
I have given some
presentations at the RxE seminar and the Tech User’s Group on this issue.
The BEACON User’s Group has also discussed it, since the reactivity bias
is programmed into the software. I’ll be happy to discuss it
further if anyone is interested.
Damon Bryson
(803) 345-4814
dbryson@scana.com
From: pwrrm@retaqs.com
[mailto:pwrrm@retaqs.com] On Behalf Of Gore,
Duane
Sent: Thursday, July 10, 2008 5:44
PM
To: pwrrm@retaqs.com
Subject: [Pwrrm] Cycle Length
Prediction Error when using Westinghouse 1.5xIBFAs
STP has been experiencing a difference between predicted
cycle lengths and actual EOC burnup (specifically, over-predictions of cycle
length). This effect seems to have begun when we started using 1.5x (B-10
loading) IFBA. Westinghouse uses their APA package for our core design. Has any
other utility had a similar experience?
Duane Gore
Supervisor, Reactor Engineering
STPNOC
(361) 972-8909