ML18153A794

Forwards Response to Request for Addl Info Re Core Uprate

ML18153A794
Person / Time
Site:	Surry
Issue date:	04/13/1995
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
95-036B, 95-36B, NUDOCS 9504210021
Download: ML18153A794 (4)

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VIRGINIA. ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 13, 1995 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.

NE/JLJ-CGL Docket Nos.

License Nos.

95-0368 RO' 50-280 50-281 DPR-32 DPR-37 CORE UPRATE - MATERIALS & CHEMICAL ENGINEERING BRANCH REQUEST FOR ADDITIONAL INFORMATION The Surry Core Uprate Technical Specification change request was submitted for NRC review by an August 30, 1994 letter (Serial No.94-509). Subsequently, we received a request for additional information from the Materials & Chemical Engineering Branch (EMCB) of NRR regarding our core uprate submittal. The EMCB questions and our responses, except one, were transmitted by a March 23, 1995 letter (Serial No. 95-036A). The attachment to this letter provides the outstanding response.

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

Very truly yours,

~u-Pwl~

James P. O'Hanlon Senior Vice President - Nuclear - Response to EMCB Request for Additional Information Regarding Proposed Technical Specification Changes to Accommodate Core Uprating - Surry Power Station Units 1 and 2 9504210021 950413 PDR ADDCK 05000280 p

PDR

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• - cc:

l:J. 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 Commissioner Department of Radiological Health Room 104A 1500 East Main Street Richmond, Virginia 23219

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ATTACHMENT 1 Response to Materials & Chemical Engineering Branch Request for Additional Information Regarding Proposed Technical Specification Changes to Accommodate Core Uprating -

Surry Power Station Units 1 and 2

2.

The Steam Generator Tube Integrity portion of the Surry Power Uprate amendment has been reviewed.

The licensee is requested to respond to-the following question:

a. The structural analyses performed by the licensee has not been adequately described (i.e., the licensee states that the analysis performed for their steam generator replacement program was reperformed with the uprated conditions and that the components continue to remain in compliance with the ASME Code).

A more detailed description of the analyses performed to demonstrate the adequacy of the 40% plugging criteria should be provided.

This analysis should include an assessment of the changes in such factors as temperature, pressure, and flow on the minimum

. required tube wall thickness.

Regulatory Guide 1.121 describes a methodology acceptable to the staff for determining tube repair limits.

RESPONSE

The standard used for establishing steam generator tube plugging criteria isSection XI of the ASME Code, which provides two acceptable methods for

. establishing the steam generator tube plugging limit. Paragraph IWB-3521.1 allows a depth of outside diameter degradation not to exceed 40% of the wall thickness of the tubing from SB 163 material when the mean tube radius to wall thickness ratio is less than 8.7. Alternatively, Paragraph IWB-3630 provides that a plant-specific evaluation may be performed by analysis and testing consistent with the guidelines of Regulatory Guide (RG) 1.121 to determine the allowable tube wall degradation. It has not been necessary.to perform a RG 1.121 analysis for the Surry. steam generators since the provisions of Paragraph IWB-3521.1 are satisfied.

The plugging criterion of 40% allowable tube wall loss in Paragraph IWB-3521.1 in Section XI of the ASME Code is based on the work performed by its Working Group on Steam Generator lnservice Inspection. The Working Group considered the following four different steam generator designs in its evaluation:

the Combustion Engineering Non-Economizer design, the Combustion Engineering System 80 design, the Westinghouse Series 51 designs, and the Westinghouse Model D design.

The tubing material for the four designs is Alloy 600 (SB 163) and the ratio of mean radius to thickness ranges from 7.3 to 8.7. Each design was evaluated generically using bounding loads during normal operation and postulated accident conditions.

1-1

e Based on this evaluation, the Working Group concluded that, for the four designs considered, the tubing can sustain degradation in excess of 50% of the wall thickness and still meet the applicable stress and strength requirements. Finally, a conservative factor of 10% wall thickness was assumed to account for both eddy current measurement uncertainty and corrosion allowance for continued plant operation until the next inspection. Thus, a plugging criterion of 40% tube wall was established and adopted by the Working Group on standards for ASME Section XI.

The mean radius to wall thickness ratio for the Surry Units 1 and 2 Model 51 F replacement steam generator tubes is approximately 8.3 and the tubing material is Alloy 600 (SB 163).

Therefore, the 40% steam generator tube plugging limit established within Paragraph IWB-3521.1 of Section XI of the ASME Code applies to Surry. Furthermore and as shown below in Table 1-1, it is judged that none of the design and operating parameters applicable to the tubes change significantly due to the core uprating such that the conclusion of the Working Group would be adversely affected. Therefore, no further analysis is required in support of the currently applied 40% steam generator tube plugging limit for the Surry Units 1 and 2 Model 51 F steam generators for operation at the uprated core power level.

TABLE 1-1 SURRY PERFORMANCE PARAMETERS Parameter Core Power (MWt)

Thermal Design Flow (gpm)

RCS Pressure (psia)

RCS Temperature (°F)

Core Outlet Vessel Outlet Core Average Vessel Average Vessel/Core Inlet SIG Outlet Steam Generator Steam Temperature (°F)

Steam Pressure (psia)

Total Steam Flow (x106 lb/hr)

Feed Temperature (°F)

Zero Load Temperature (°F)

Core Bypass (%)

Tube Plugging (%)

1-2 Current Conditions 2441 88500 2250 608.2 605.6 577.1 574.4 543.0 543.0 516.0 785 10.66 437.7 547 4.5 0.0 Uprated Conditions with 7% Plugging 2546 88500 2250 609.3 605.6 576.5 573.0 540.4 540.1 515.9 784 11.26 443.2 547 6.0 7.0