ML20151J455

Comments on Rept Submitted by NRC Re Reactor Vessel Heatup & Cool Down Tech Spec Pressure Temp Limits for Plant.Rept Does Not Adequately Encompass Vessel Closure Flange Region Pressure Temp Safety Margins

ML20151J455
Person / Time
Site:	Comanche Peak
Issue date:	06/19/1984
From:	Youngblood B Office of Nuclear Reactor Regulation
To:	Spence M TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
References
NUDOCS 8406270081
Download: ML20151J455 (3)

Text

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j g 1 9 1994 Docket Nos.: 50-445 and 50-446 Mr. M. D. Spence President Texas Utilities Generating Company 400 N. Olive Street Lock Box 81 Dallas, Texas 75201

Subject:

Reactor Ves.iel Heat-Up and Cooldown Technical Specification Pressure-Temperature Limits for Comanche Peak Steam Electric Station (Units 1 and 2)

Mr. H. C. Schmidt's letter to me dated May 16, 1984 provided a report containing the results of a stress and fracture mechanics analysis of the Comanche Peak reactor vessel materials in support of incorporating the reactor vessel heat-up and cooldown pressure-temperature limits calculated in the Comanche Peak Technical Specification Figures 3.4-2 and 3.4-3.

The NRC technical review staff has reviewed the report and finds that the heat-up and cooldown curves reflected in Figures 6 and 7, respectively, in the report do not adequately encompass the vessel closure flange region pressure-temperature safety margins, which are specifically identified in Appendix G to 10 CFR Part 50.

The analytical results presented in the report show that the reactor vessel beltline materials are more limiting than are the vessel closure flange materials, and that both the bolt-up and total stresses in the closure flange region are predicted to be much lower than anticipated by the NRC staff. At the critical flange location (outside postulated circumferential flaws at the vessel flange-to-shell jtnction), the calculated bolt-up stress is reported to be 15.61 ksi, and the calculated total stresses are reported to be 13.42 ksi and 34.90 ksi during vessel cooldown and heat-up, respectively; values which are significantly lower than those calculated for an identically designed and fabricated reactor vessel installed in the Salem Nuclear Power Plcnt by the Salem licensee.

The Comanche Peak and Salem Nuclear Steam Supply System designs each contain four loops, were purchased from Westinghouse, and had their reactor vessels designed and fabricated by Combustion Engineering. Therefore, the reactor vessel design for Comanche Peak and Salem should be identical.

In Table 5.2-14 of the Salem FSAR, the total stress intensity at the vessel flange is reported to be 58.20 ksi.

Furthermore, Combustion Engineering has reported in correspondence to the ASME Section XI Code Committee (J. Houstrup to P. N. Randall) dated February 27, 1981 a bolt-up stress of 30.14 ksi at a 8406270001 840619 PDR ADOCK 05000445 A

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) typical reactor vessel flange-to-shell junction (a stress concentration factor of 1.29 was used to account for the fillet at that location; i.e., the nominal bolt-up stress was 23.50 ksi). At the vessel head-to-flange junction, the corresponding stresses were reported to be 49.40 ksi (peak) and 31.90 ksi (nominal). These stresses are significantly higher than those calculated in your report for Comanche Peak.

Unless these differences can be satisfactorily explained and technically justified by Texas Utilities, the staff cannot accept your request for incorporating the pressure-temperature limits reflected in Figures 6 and 7 of your report in the Comanche Peak Technical Specifications.

If these calculated stress differences cannot be settled within the current schedule for Comanche Peak Unit I licensing, the staff will utilize the more conservative pressure-temperature limits (depicted in Figures 4 and 5 of your report) for inclusion in the Comanche Peak Technical Specifications.

1 These findings were discussed in detail with your staff and Westinghouse during a conference call held on June 1,1984. This letter serves to summarize and document the relevant facts discussed during that conference call.

If further discussion of this matter is desired, please advise John Stefano of my staff accordingly.

Sincerely, B. J. Youngblood, Chief Licensing Branch No. 1 Division of Licensing cc: See next page CONCURRENCES: *See previous con ences

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COMANCHE PEAK Mr. M. D. Spence President Texas Utilities Generating Company 400 N. Olive St., L.B. 81 Dallas, Texas 75201 cc: Nicholas S. Reynolds, Esq.

Mr. James E. Cummins Bishop, Liberman, Cook, Resident Inspector / Comanche Peak Purcell & Reynolds Nuclear Power Station 1200 Seventeenth Street, N. W.

c/o V. S. Nuclear Regulatory Washington, D. C. 20036

- - Commission P. O. Box 38 Robert A. Wooldridge, Esq.

Glen Rose, Texas 76043 Worsham, Forsythe, Sampels &

Wooldridge Mr. John T. Collins 2001 Bryan Tower, Suite 2500 U. S. NRC, Region IV Dallas, Texas 75201 611 Ryan Plaza Drive Suite 1000 Mr. Homer C. Schmidt Arlington, Texas 76011 Manager - Nuclear Services Texas Utilities Generating Company Mr. Lanny Alan Sinkin 2001 Bryan Tower 114 W. 7th, Suite 220 Dallas, Texas 75201 Austin, Texas 78701 Mr. H. R. Rock B. R. Clements Gibbs and Hill, Inc.

Vice President Nuclear 393 Seventh Avenue Texas Utilities Generating Company New York, New York 10001 Skyway Tower 400 North Olive Street Mr. A. T. Parker L. B. 81 Westinghouse Electric Corporation Dallas, Texas 75201 P. O. Box 355 Pittsburgh, Pennsylvania 15230 William A. Burchette, Esq.

1200 New Hampshire Avenue, N. W.

Renea Hicks, Esq.

Suite 420 Assistant Attorney General Washington, D. C.

20036 Environmental Protection Division P. O. Box 12548, Capitol Station Ms. Billie Pirner Garde Austin, Texas 78711 Citizens Clinic Director Go,ernment Accountability Project Mrs. Juanita Ellis, President 1901 Que Street, N. W.

Citizens Association for Sound Washington, D. C.

20009 Energy 1426 South Polk David R. Pigott, Esq.

Dallas, Texas 75224 Orrick, Herrington & Sutcliffe 600 Montgomery Street Ms. Nancy H. Williams San Francisco, California 94111 CYGNA 101 California Street Anthony Z. Roisman, Esq.

San F"ancisco, California 94111 Trial Lawyers for Public Justice 2000 P. Street, N. W.

Suite 611 Washington, D. C. 20036 L