ML082180004
| ML082180004 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/05/2008 |
| From: | Markley M NRC/NRR/ADRO/DORL/LPLIV |
| To: | Edington R Arizona Public Service Co |
| Markley M, NRR/DORL/LPL4, 301-415-5723 | |
| Shared Package | |
| ML082170703 | List: |
| References | |
| TAC MD9329 | |
| Download: ML082180004 (5) | |
Text
August 5, 2008 Mr. Randall K. Edington Executive Vice President, Nuclear/CNO Mail Station 7602 Arizona Public Service Company P. O. Box 52034 Phoenix, AZ 85072-2034
SUBJECT:
PALO VERDE NUCLEAR GENERATING STATION, UNIT 2 -
SUMMARY
OF CONFERENCE CALL REGARDING THE SPRING 2008 STEAM GENERATOR TUBE INSPECTIONS DURING REFUELING OUTAGE 14 (TAC NO. MD9329)
Dear Mr. Edington:
On April 29, 2008, representatives of the U.S. Nuclear Regulatory Commission (NRC) and Arizona Public Service Company (APS) held a telephone conference call to discuss the ongoing steam generator tube inspection activities at Palo Verde Nuclear Generating Station (Palo Verde), Unit 2. The NRC staff did not identify any issues that warranted immediate follow-up.
The staff plans to review the APS submittal of the Palo Verde, Unit 2 steam generator report, when available.
The slides provided by the licensee in support of these discussions (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082170723) are available to the public. A summary of the conference call is enclosed.
If you have any questions, please contact me at 301-415-5723, or Michael.Markley@nrc.gov.
Sincerely,
/RA/
Michael T. Markley, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN 50-529
Enclosure:
Summary of Conference Call cc w/encl: See next page
Pkg ML082170703, Letter/Summary ML082180004, Palo Verde Slides ML082170723 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/CSGV/BC NRR/LPL4/BC (A)
NRR/LPL4/PM NAME MMarkley JBurkhardt AHiser (*)
JDonohew MMarkley DATE 8/05/08 8/5/08 5/5/08 8/05/08 8/05/08
Palo Verde Nuclear Generating Station 7/2/2008 cc:
Mr. Steve Olea Arizona Corporation Commission 1200 W. Washington Street Phoenix, AZ 85007 Mr. Douglas Kent Porter Senior Counsel Southern California Edison Company Law Department, Generation Resources P.O. Box 800 Rosemead, CA 91770 Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 40 Buckeye, AZ 85326 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 Chairman Maricopa County Board of Supervisors 301 W. Jefferson, 10th Floor Phoenix, AZ 85003 Mr. Aubrey V. Godwin, Director Arizona Radiation Regulatory Agency 4814 S. 40th Street Phoenix, AZ 85040 Mr. Scott Bauer, Director Regulatory Affairs Palo Verde Nuclear Generating Station Mail Station 7636 P.O. Box 52034 Phoenix, AZ 85072-2034 Mr. Dwight C. Mims, Vice President Regulatory Affairs and Plant Improvement Palo Verde Nuclear Generating Station Mail Station 7605 P.O. Box 52034 Phoenix, AZ 85072-2034 Mr. John C. Taylor Director, Nuclear Generation El Paso Electric Company 340 E. Palm Lane, Suite 310 Phoenix, AZ 85004 Mr. James Ray Public Service Company of New Mexico 2401 Aztec NE, MS Z110 Albuquerque, NM 87107-4224 Mr. Geoffrey M. Cook Southern California Edison Company 5000 Pacific Coast Hwy., Bldg. D21 San Clemente, CA 92672 Mr. Robert Henry Salt River Project 6504 E. Thomas Road Scottsdale, AZ 85251 Mr. Jeffrey T. Weikert Assistant General Counsel El Paso Electric Company Mail Location 167 123 W. Mills El Paso, TX 79901 Mr. Eric Tharp Los Angeles Department of Water & Power Southern California Public Power Authority P.O. Box 51111, Room 1255-C Los Angeles, CA 90051-0100 Mr. Brian Almon Public Utility Commission William B. Travis Building P.O. Box 13326 1701 N. Congress Avenue Austin, TX 78701-3326 Ms. Karen O'Regan Environmental Program Manager City of Phoenix Office of Environmental Programs 200 W. Washington Street Phoenix, AZ 85003
SUMMARY
OF CONFERENCE CALL REGARDING STEAM GENERATOR TUBE INSPECTION RESULTS ARIZONA PUBLIC SERVICE COMPANY, ET. AL.
PALO VERDE NUCLEAR GENERATING STATION, UNIT 2 DOCKET NO. STN 50-529 On April 29, 2008, representatives of the U.S. Nuclear Regulatory Commission (NRC) and Arizona Public Service Company (APS) held a telephone conference call to discuss the ongoing steam generator (SG) tube inspection activities at Palo Verde Nuclear Generating Station (Palo Verde), Unit 2. In support of the conference call, the licensee provided several slides (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082170723) that summarized the inspection activities and preliminary findings.
Palo Verde Unit 2 has two SGs, each having 12580 thermally treated Alloy 690 tubes that have an outside diameter of 0.75 inches and a wall thickness of 0.042 inches. Ferritic stainless steel eggcrate tube supports, diagonal bars, and/or vertical straps support the tubes at various locations.
The conference call focused on wear indications found near the central cavity region and in the periphery of the tube bundle on the cold-leg side of the SG. Additional information discussed during the conference call and not included in the document provided by the licensee is summarized below:
The design of the replacement SGs took into account the power uprate that was recently implemented at Palo Verde.
Acronyms used in the document provided by the licensee include:
BW (batwing)
BWSC (batwing stay cylinder)
EFPY (effective full power years)
FOSAR (foreign object search and retrieval)
PLP (possible loose part) psid (pounds per square inch differential)
PVNGS (Palo Verde Nuclear Generating Station)
TW (through-wall) 3NDP (three times the normal operating differential pressure)
No batwing wear was identified in the central cavity region in Unit 1; however, the first operating cycle for Unit 1 was shorter than typical. In addition, prior to operation, several tubes that border the central cavity region were preventively plugged and stabilized. This preventive plugging took place between columns 75 and 130. This region of the tube bundle was not preventively plugged in the original SGs.
Enclosure
As the distance from the central cavity region increases, the batwing wear rate tends to decrease. This is consistent with what was observed in the original SGs.
The growth rate of the wear indications at the vertical straps is lower than the growth rates of the wear indications at the batwings.
The size of the region near the central cavity where batwing wear is occurring in the replacement SGs is comparable in size to the similar region in the original SGs.
The design of the replacement SGs was intended to limit the number of wear indications at the batwings in the central cavity region (e.g., at most eight tubes plugged as a result of this mechanism).
None of the tubes that were plugged in the central cavity region for wear indications at the batwing support during the 2008 outage were stabilized.
Although tubes that were plugged for this mechanism during the first inservice inspection at Unit 2 were stabilized, it was subsequently concluded that stabilization in this region is not needed (since there is no concern for tube severance).
The flow holes in the batwings are approximately 0.3 inches from the edge of the batwing. This distance corresponds to the length of some of the wear scars.
Gasket material was left in the SG. Since this material did not cause wear in a higher flow rate area, the licensee does not expect that it will cause significant wear at its current location. The licensee will continue to track this material.
In addition to performing foreign object search and retrieval inspections at the top of the tubesheet and at the flow distribution baffle, a third party review of the eddy current data is performed to look for loose parts and wear attributed to loose parts near the top of the tubesheet. In addition, the eddy current inspections focused on peripheral tubes (i.e., the location more likely to have a loose part).
Regarding the batwing wear indications in the periphery of the cold-leg, no visual inspections have been performed in this region; however, rotating probe testing of these indications validated that the supports are in their normal position and appear to be intact (based on eddy current testing). These indications are being evaluated as part of the licensees corrective action program. Visual inspections of this region may be an outcome of this evaluation.
The one tube plugged as a result of wear at the batwing in the periphery of the cold-leg was stabilized. The tube was stabilized since this tube was in the periphery of the tube bundle and could be affected by wear from a loose part.
Based on this subsequent information, the NRC staff did not identify any issues that warranted immediate follow-up action.