Answers below from Beaver Valley Power Station
Anthony (A.R.) Burger Supervisor, Reactor Engineering FENOC - Beaver Valley Power Station Phone: (724) 682-4108 Cell: (724) 601-3224 FAX: (724) 682-4250 Email: aburger@firstenergycorp.com
Charlene.N.Chotal al@dom.com Sent by: To pwrrm@retaqs.com pwrrm@retaqs.com cc
01/22/2009 09:12 Subject AM [Pwrrm] PWRRM Request for B-10 Information(in preparation for INPO) Please respond to PWR Reactivity Management <pwrrm@retaqs.com >
Greetings,
INPO will be coming to Surry Power Station in a week and I would like to ask two questions to the group. In your response, you do not need to reply to everyone. I will be gathering the information and putting it into one excel file. If you would like a copy, please let me know.
1) This question has been asked already, but we did not get many responses. Core modeling is performed using the CASMO-4/SIMULATE-3 computer codes. Our most recent Reactivity Anomaly calculation(the comparison between measured and predicted boron concentrations) gave us an uncorrected value of about 750pcm. This is quite close to our tech spec limit of 1000pcm. If we corrected for B-10, the anomaly value would be closer to 300pcm. Currently we use the uncorrected value in our comparison to the predicted model. What is your typical maximum offset between your measured and predicted Reactivity Anomaly? Is this with or without B-10 depletion? Do you use your B-10 depletion value for the tech spec surveillance?
Response: BV utilizes the corrected B-10 values for the monthly Tech Spec surveillance. We were also near 750 pcm a few cycles ago until we started using corrected values for B-10. Both BV units have performed some up-rates (8%) and LEFM implementation (1.4%) over the last three cycles, so our measured to predicted values have varied a little. The BV-1 anomaly is currently about 200 pcm, while BV-2's is about 400 pcm (high, i.e. excess reactivity). If we had not corrected for B-10, BV2 would have exceeded the TS 1000 pcm requirement a few cycles ago. This is especially true for long operating runs (500 days) when B-10 continues to deplete because there is no make-up from a downpower, etc.
The other reason to correct for B-10 is in shutdown margin. While not correcting for B-10 for the monthly reactivity anomaly is "conservative", this is not true for comparsion to shutdown margin. With depleted boron in the RCS your actual shutdown margin, based on a required boron concentration, is reduced if you compare the measured uncorrected value to the predicted, since the predicted assumes 19.9 a/o (core design values).
2) This question is regarding Estimated critical conditions/position. What is the pcm delta typically observed at your plant between the predicted critical conditions and the actual conditions? If a delta is observed, does the predicted critical calculation account for B-10 depletion? At what point (i.e. >100 pcm delta) would Operations or Reactor Engineering write a condition report?
Response: Fortuneately, both units have had very few ECPs for the last few cycles. The last few have been well within 200 pcm of predicted. We have also corrected for B-10 during ECP calculations. Especially, since we have had long operating runs and the B-10 values have been as low as 17 a/o. Near the end of the cycle this is not much of a factor since the difference in boron cocentration is low, but 2/3 through a cycle this can be a large difference in boron concentration.
We would issue a CR if the measured to predicted ECP difference was greater than 300 pcm.
Charlene Chotalal Lead Reactor Engineer Surry Power Station Work: (757)-365-2819
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