PWRRM July 2008

pwrrm@retaqs.com

7 participants
4 discussions

Re: [Pwrrm] Cycle Length Prediction Error when using Westinghouse1.5xIBFAs
by Elam, Kevin Scott 15 Jul '08

15 Jul '08

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. Elam 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(a)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(a)scana.com From: pwrrm(a)retaqs.com [mailto:pwrrm@retaqs.com] On Behalf Of Gore, Duane Sent: Thursday, July 10, 2008 5:44 PM To: pwrrm(a)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

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Johnny Henderson/NUC/VANCPOWER is out of the office.
by Johnny.Henderson＠dom.com 14 Jul '08

14 Jul '08

I will be out of the office starting 07/13/2008 and will not return until 07/21/2008. I will respond to your message when I return. CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and/or privileged and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an additional express written confirmation to that effect. The information is intended solely for the individual or entity named above and access by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or use of the contents of this information is prohibited and may be unlawful. If you have received this electronic transmission in error, please reply immediately to the sender that you have received the message in error, and delete it. Thank you.

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Cycle Length Prediction Error when using Westinghouse 1.5x IBFAs
by Gore, Duane 14 Jul '08

14 Jul '08

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

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Reactivity plan approval and revisions/ramp rate alarm
by Adina.K.Lafrance＠dom.com 08 Jul '08

08 Jul '08

SOER 07-01 recommendation 3 stated that "plans for significant reactivity changes are reviewed and approved by appropriate station and shift operations management..." and "If plant conditions delay power changes, the reactivity plan is revised to meet the new plant conditions and approved by management". Does anyone have specific thresholds for: 1) the level of review a plan requires (such as <10% requires shift supervision, >10% requires shift management, >50% requires station management) or 2) when a reactivity plan must be revised (such as > 1 hour delay, rods > 10 steps from the predicted value, current power level step >2% from predicted) Additional question How do other stations incorporate any ramp rate restrictions that may apply? (Ramp rate alarm, operator training, ramp plan) Thank you. Adina LaFrance Nuclear Analysis & Fuel Reactor Engineer Surry Power Station Email: Adina.K.LaFrance(a)Dom.com Phone: 757-365-2658 Pager #: 4290 CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and/or privileged and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an additional express written confirmation to that effect. The information is intended solely for the individual or entity named above and access by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or use of the contents of this information is prohibited and may be unlawful. If you have received this electronic transmission in error, please reply immediately to the sender that you have received the message in error, and delete it. Thank you.

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PWRRM July 2008