ML18153C838

Submits Info Re Revised 10CFR50.61 Requirements & Procedure for Calculating Reactor Vessel Matl Embrittlement. Implementation of Flux Reduction Program Underway at Surry 1.Values Re end-of-life PTS Revised

ML18153C838
Person / Time
Site:	Surry, North Anna
Issue date:	12/10/1991
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
91-328, NUDOCS 9112120203
Download: ML18153C838 (4)

Text

,. .' e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 December 10, 1991 United States Nuclear Regulatory Commission Serial No.91-328 Attention: Document Control Desk NO/CGL:vlh R1 Washington, D. C. 20555 Docket Nos. 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 REVISION TO 10 CFR 50.61 FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS In response to the revised 10 CFR 50.61 requirements and procedure for calculating reactor vessel material embrittlement, Virginia Electric and Power Company is providing the following information.

The Pressurized Thermal Shock (PTS) rule requires each PWR licensee to report the results of the calculations of predicted RTPTS values for each beltline material for the fluence at the time the report is submitted and the fluence at the expiration date of the operating license (EOL). The report should include the copper content, nickel content, fluence values, and assumptions about core loading patterns that were used in the calculations. The PTS rule further requires that if RTPTS for the controlling material is predicted to exceed the screening criterion before EOL, the licensee should submit plans and a schedule for flux reduction programs that are reasonably practicable to avoid reaching the screening criterion. Finally, the PTS rule requires licensees of plants that would reach the screening criterion before EOL despite the flux reduction program to submit a plant-specific safety analysis justifying operation beyond the screening criterion.

The recent revision to the 10 CFR. 50.61 PTS rule requires the PWR licensee to recalculate values of RTPTS for the limiting reactor vessel beltline materials. If the RTPTS for any of the materials is predicted to exceed the screening criterion prior to EOL, the licensee must resubmit to the NRC the RTPTS results for those materials prior to December 16, 1991. If RTPTS is not predicted to exceed the screening criterion prior to EOL, the assessment must be submitted with the next update to the pressure-temperature limits, or the next reactor vessel materials surveillance report, or within 5 years bf the effective date of the rule, whichever comes first. l\r~ *

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We submitted PTS analysis reports to the NRC via letters dated April 30, 1987 and March 15, 1988 (Serial Nos. 86-8198 and 88-056) for Surry and North Anna, respectively. The Surry PTS analysis is documented in WCAP-11015, Revision 1 (C.

C. Heinecke, et al., "Surry Units 1 and 2 Reactor Vessel Fluence and RTPTS Evaluations," dated April, 1987). The North Anna PTS analysis is documented in WCAP-11016, Revision 3 (C. C. Heinecke, et al., "North Anna Units 1 and 2 Reactor Vessel Fluence and RTPTS Evaluations," dated January, 1988). These analyses utilized the method of 10 CFR 50.61 prior to the incorporation of the RG 1.99 Revision 2 methodology into the PTS rule.

We have calculated revised values of the EOL RTPTS for the controlling materials identified in the previous PTS submittals for both Surry and North Anna. We have concluded that none of the revised RTPTS values exceed the applicable screening criterion prior to end of license with the exception of that of the Surry Unit 1 Lower Shell Longitudinal Weld L2. Our calculations utilized the revised 10 CFR 50.61 procedure, as well as the same copper nickel contents, EOL fluence, and core loading pattern assumptions as the previous PTS submittals. All assumptions reflect, or are conservative with respect to, the current plant configuration and the requirements of 10 CFR 50.61.

As indicated in previous correspondence (Letters Serial Nos.* 89-748 dated December 1, 1989,90-335 dated July 30, 1990, and 91-374 dated July 8, 1991 ), we are in the process of implementing a flux reduction program at Surry 1. As noted in our July 8, 1991 letter, flux suppression inserts (FSls) are planned to be installed in Surry Unit 1 during Cycle 13. The target fluence in this program is well below that which could cause RTPTS to exceed the screening criterion at EOL. We consider this plan adequate to ensure that the requirements of 10 CFR 50.61 will continue to be met throughout the operating life of the plant.

The attachment presents the chemistry and fluence data, and the RTPTS values calculated for the limiting materials in the Surry and North Anna vessels. As required by the PTS rule, the appropriate information is included in the attachment for the Surry Unit 1 Lower Shell Longitudinal Weld L2, which is predicted to exceed the screening criteria at EOL in the absence of flux reduction. Although 10 CFR 50.61 does not require immediate submission of revised values of RTPTS for materials not predicted to exceed the screening criterion prior to EOL, the attachment also includes revised*

RTPTS values for the limiting materials in the Surry and North Anna reactor vessels.

If you have any questions or require additional information, please contact us.

Very truly yours, wrf(ii;J W. L. Stewart Senior Vice President - Nuclear Attachment - Revised Current and EOL RT PTS Values

cc: U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. M. S. Lesser NRC Senior Resident Inspector North Anna Power Station

REVISED CURRENT AND EOL RTpTs VALUES FLUENCE Screen.

(1El9 RT(PTS) Crit.

STATION UNIT WELD ID WT.% CU WT% NI NLSQ.CMl (DEG Fl (DEG Fl NOTES N. Anna 1 Lower Shell 03 .15 .80 6.79 240 270 EOL N. Anna 1 Lower She 11 03 .15 .80 1.88 207 270 Current N. Anna 1 Circ. Weld 04 .11 .086 6.79 148 300 EOL N. Anna 1 Circ. Weld 04 .11 .086 1.88 134 300 Current N. Anna 2 Lower Shell 03 .13 .83 6.96 230 270 EOL

~- Anna 2. Lower Shell 03 .13 .83 1. 79 201 270 Current N; A~ha 2 Circ. Weld 04 .065 .044 6.96 60 300 EOL N. Anna 2 Circ. Weld 04 .065 .044 1. 79 *49 300 Current Surry 1 Circ. Weld 05 .21 .58 5.55 295 *

• 300 EOL Surry 1 Circ. Weld 05 .21 .58 2.07 259 300 Current Surry 1 Long. Weld L2 .35 .67 .901 282*/*

• 270 EOL Surry 1 Long. Weld L2 .35 .67 .335 221 270 Current Surry 2 Circ. Weld 05 .19 .56 5.69 281 300 EOL Surry 2 Circ. Weld 05 .19 .56 2.07 247 300 Current Surry 2 Long. Welds Ll/L2 .29 .55 .922 246 270 EOL Surry 2 Long. Welds Ll/L2 .29 .55 .336 195 270 Current

• Predicted to exceed screening criteria at EOL in the absence of flux reduction.

• *

• Expected RTprs under flux reduction will be less than this value.