ML070430281
| ML070430281 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 01/31/2007 |
| From: | Pierre G Florida Power & Light Energy Seabrook |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-06-002, SBK-L-07020 | |
| Download: ML070430281 (5) | |
Text
FPL Energy Seabrook Station FPL Ene gV P.O. Box 300 Seabrook, NH 03874 Seabrook Station (603) 773-7000 JAN 3 1 2007 Docket No. 50-443 SBK-L-07020 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Seabrook Station Response to Request for Additional Information Regarding Resolution of Generic Letter 2006-02, Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power
References:
- 1. Florida Power and Light Company (FPL) letter L-2006-07, NRC Generic Letter 2006-02, 60-Day Response, April 3, 2006
- 2. NRC letter to FPL Energy Seabrook, LLC, Request for Additional Information Regarding Resolution of Generic Letter 2006-02, Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power (TAC NOS. MD0947 through MD1050), December 5, 2006 By letter dated April 3, 2006, (Reference 1) FPL submitted the FPL Energy Seabrook, LLC (FPL Energy Seabrook) response to Generic Letter 2006-02.
Jn Reference 2, the NRC requested additional information in order to resolve issues discussed in the Generic Letter.
Enclosed are the FPL Energy Seabrook responses to Request for Additional Information (RAI)
Questions 4 and 5. As stated in Reference 2, Enclosure 3, RAI Questions 4 and 5 are the only questions applicable to FPL Energy Seabrook.
Should you have any questions regarding this information, please contact Mr. James Peschel, Regulatory Programs Manager, at (603) 773-7194.
Very truly yours, FPL Energy Seabrook, LLC Gene St. Pierre Site Vice President 2-/5 an FPL Group company
United States Nuclear Regulatory Commission SBK-L-07020 / Page 2 Enclosure cc:
S. J. Collins, NRC Region I Administrator G. E. Miller, NRC Project Manager, Project Directorate 1-2 G. T. Dentel, NRC Resident Inspector OATH AND AFFIRMATION I, Gene St. Pierre, Site Vice President of FPL Energy Seabrook, LLC, hereby affirm that the information and statements contained within this response to the request for additional information regarding Generic Letter 2006-02 are based on facts and circumstances which are true and accurate to the best of my knowledge and belief.
Sworn and Subscribed before me this dayof
,4 2007 Gene St. Pierre Site Vice President Notary Public
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Enclosure to SBK-L-07020 FPL Energy Seabrook Response to Request for Additional Information
Response to Request for Additional Information Regarding Resolution of Generic Letter 2006-02, Grid Reliability and the Impact on Plant Risk and Operability of Offisite Power Question 4:
Identification of Applicable Sin2le Contin2encies In response to question 3(a) you did not identify the loss of other critical transmission elements that may cause the offsite power system (OSP) to degrade, other than the loss of the nuclear unit.
If it is possible for specific critical transmission elements (such as other generators, critical transmission line, transformers, capacitor banks, voltage regulators, etc.) to degrade the OSP such that inadequate post-trip voltage could result, have these elements been included in your N-1 contingency analysis? When these elements are included in your GO's contingency analysis model and failure of one of these transmission elements could result in actuation of your degraded voltage grid relay, is the offsite power declared inoperable? If not, what is your basis for not declaring the offsite power inoperable?
Response to Question 4 Discussions with the local Regional Transmission Operator (ISO-NE) confirm that the loss of other transmission elements, other than the Nuclear Power Plant (NPP), will not result in inadequate post trip voltages at the NPP.
Question 5:
Seasonal Variation in Grid Stress (Reliability and Loss-of-offsite power (LOOP) Probability Certain regions during certain times of the year (seasonal variations) experience higher grid stress as is indicated in Electric Power Research Institute (EPRI) Report 1011759, Table 4-7, Grid LOOP Adjustment Factor, and NRC NUREG/CR-6890. Do you adjust the base LOOP frequency in your probabilistic risk assessment (PRA) and Maintenance Rule evaluations for various seasons? If you do not consider seasonal variations in base LOOP frequency in your PRA and Maintenance Rule evaluations, explain why it is acceptable not to do so.
Response to Question 5 As provided by ISO-NE, there is no seasonal variation in the LOOP frequency in the local transmission region.
Appendix B of WCAP-16316 (2/2005) identifies 7 events described as "major disturbances and unusual occurrences" that impacted ISO New England from 1999 to 2003. Two of these events occurred in Summer (July, August), one in the fall (November), three in Winter (December and 2 in March), and one in Spring (June). This shows no seasonal variation in this limited data set.
Also note that these events impacted only a small area of the ISO New England grid or resulted in only a voltage reduction. These events may be identified as precursor events to a LOOP at Seabrook, but were not significant with regard to actual Seabrook-area grid performance.
Based on the data for the ISO New England grid, there is no significant seasonal variation.
There are no known time related variations in the probability of a LOOP at Seabrook. The PRA model of record is an average model. As such, frequencies are average values without time related variations. Specific applications may require consideration of variations in baseline 1
frejuencies. LOOP and ATWS are examples where variation from average frequency may be considered on an application specific basis.
Based on the ISO New England specific information, no seasonal adjustments to LOOP frequency are required for 1 OCFR50.64a(4) evaluations. However, LOOP frequencies are adjusted based on grid related maintenance and predicted weather conditions for 10CFR50.64a(4) evaluations.
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