ML073100377
| ML073100377 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 10/23/2007 |
| From: | Jenewein B South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G25, NOC-AE-07002224, RR-ENG-2-47, STI 32216226 | |
| Download: ML073100377 (4) | |
Text
Nuclear Operating Company South Texas Pm/ed Eectrkic GenermingStatlon P.. Sox289 Wadsworth, Teras 77483 October 23, 2007 NOC-AE-07002224 File No.: G25 1 OCFR50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2746 South Texas Project Unit 2 Docket No. STN 50-499 Supplement to Request for Relief from ASME Boiler and Pressure Vessel Code,Section XI Requirements for the Essential Cooling Water System (Relief Reauest RR-ENG-2-47)
Reference:
Letter from David W. Rencurrel to NRC Document Control Desk, "Request for Relief from ASME Boiler and Pressure Vessel Code,Section XI Requirements for the Essential Cooling Water System (Relief Request RR-ENG-2-47)," dated November 15, 2006 (NOC-AE-06002070) (ML063250344)
In accordance with the provisions of 10 CFR 50.55a(g)(5)(iii), the STP Nuclear Operating Company requested relief from IWA-5250 of Section Xl of the ASME Boiler and Pressure Vessel Code, as referenced above. In response to reviewer questions, attached to this letter is supplemental information in support of that request.
There are no commitments in this submittal.
If there are any questions, please contact either Mr. P. L. Walker at (361) 972-8392 or me at (361) 972-7431.
Br nd nrL. Jenewein TMest ger, Testi ng/P rog rams PLW
Attachment:
Supplement to Request for Relief from ASME Boiler and Pressure Vessel Code, Section Xl Requirements for the Essential Cooling Water System (Relief Request RR-ENG-2-47) kwr LA4~4Z~
STI No. 32216226
NOC-AE-07002224 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Mohan C. Thadani Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (MS 7 D1) 11555 Rockville Pike Rockville, MD 20852 Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan C. Thadani U. S. Nuclear Regulatory Commission Thad Hill Steve Winn Harry Holloway Eddy Daniels Marty Ryan NRG South Texas LP J. J. Nesrsta R. K. Temple E. Alarcon Kevin Polio City Public Service C. Kirksey City of Austin Jon C. Wood Cox Smith Matthews
Attachment NOC-AE-07002224 Page 1 of 2 SOUTH TEXAS PROJECT UNIT 2 SUPPLEMENT TO REQUEST FOR RELIEF FROM ASME BOILER AND PRESSURE VESSEL CODE, SECTION XI REQUIREMENTS FOR THE ESSENTIAL COOLING WATER SYSTEM (RELIEF REQUEST RR-ENG-2-47)
- 1.
How often are periodic walkdowns performed?
With no abnormal conditions present, a system walkdown is performed every 6 months.
If an area of de-alloying is identified, the affected location has a walkdown every month until it is repaired.
- 2.
What criteria are used after examining a de-alloyed area to determine if sufficient change has occurred to warrant further action?
The need for further action will be addressed if any of the following occur:
Change from residue buildup to active dripping; New indication at a different area on the component; or A substantial change (about 2x or more) in the size of the original indication.
- 3.
What is the allowed outage time for the Essential Cooling Water System?
Allowed outage time for the ECW system is seven days.
- 4.
How long did it take to complete the repair?
The repair was performed during Unit 2 refueling outage 2RE12 (3/25/2007-4/28/2007).
The pump was stopped at about 0800 on 3 April 2007.
Field work was ready to begin at 2005 on 3 April 2007.
Field work was completed at 0313 on 11 April 2007.
The system was restored at about 0700 on 11 April 2007.
- 5.
What is the operating temperature of the Essential Cooling Water (ECW) System at that point?
During normal operation, temperature in the supply header ranges from 47 to 950 F.
- 6.
The flaw length was 1/2-inch. What was the width?
The flaw is a roughly circular area about 1/2-inch in diameter.
- 7.
What is the conclusion regarding ECW leakage from Appendix 9A of the UFSAR?
Safety-related equipment is either designed to operate in a spray environment, or protected if sensitive to spray. Flooding in a given area due to the ECW system is enveloped by worst case flow from an opening in a local pipe due to a "critical crack,"
Attachment NOC-AE-07002224 Page 2 of 2 with an area equivalent to a rectangle of length one-half the pipe diameter and a width equal to one-half the pipe wall thickness.
- 8.
What is the source of the fracture toughness number used for aluminum-bronze?
The fracture toughness of the aluminum-bronze as determined in APTECH study AES-C-1964-1 (ML003742174) for alloy CA-954 ranges from 63.5 to 95.1 ksi-in 12
- 9.
What is the critical K factor?
For flaw stability, this methodology specifies "K" should be less than the critical stress intensity factor which represents the fracture toughness of the material. From this range, a conservative value of 65 ksi-in 112 was established. Alloy CA-952 will have better toughness than CA-954 because it will be less susceptible to dealloying.
Therefore, applying 65 ksi-in 112 as the critical stress factor will be conservative for all castings in the ECW system.
- 10.
Provide examples of previous relief requests for aluminum-bronze de-alloying:
Relief Request RR-ENG-2-38, approved by NRC safety evaluation dated 03/25/2004 (ML040860117)
Relief Request RR-ENG-2-42, approved by NRC safety evaluation dated 10/26/2006 (ML062230309)
Relief Request RR-ENG-2-44, approved by NRC safety evaluation dated, 04/30/2007 (ML070851008)