ML18141A248

Supplemental Info in Response to 831107 Request for Addl Info Re 830913 Application for Amend to Licenses DPR-32 & DPR-37,allowing Operation W/Reduced Boron Concentrations

ML18141A248
Person / Time
Site:	Surry
Issue date:	11/30/1983
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton, Varga S Office of Nuclear Reactor Regulation
References
521B, NUDOCS 8312050604
Download: ML18141A248 (4)

Text

e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261

w. L. STEWART VxcE PRESIDENT NUCLEAR 0P:ERATIONS November 30, 1983 Mr. Harold R. Denton, Director Serial No. 5218 Office of Nuclear Reactor Regulation WBR/NAS:bhg/OOllN Attn: Mr. Steven A. Varga, Chief Docket Nos.: 50-280 Operating Reactors Branch No. l 50-281 Division of Licensing License Nos.: DPR-32 U.S. Nuclear Regulatory Commission DPR-37 Washington, D. C. 20555 Gentlemen:

SUPPLEMENT TO AN AMENDMENT TO OPERATING LICENSES DPR-32 AND DPR-37 PROPOSED REDUCTION IN BORON CONCENTRATIONS SURRY POWER STATION UNITS l AND 2 In our letter dated September 13, 1983 (Serial No. 521), Vepco requested an amendment to Operating Licenses DPR-32 and DPR-37 to allow operation of Surry Unit Nos. land 2 at reduced boron concentrations. This letter provides in Attachment 1, supplemental information in response to questions forwarded to Vepco in the NRC letter of November 7, 1983.

Should you have any further questions, please contact us at your earliest convenience.

-~ry truly you.rs, UL~--.

W. L. Stewart Attachment (1) Response to Cohtainment Systems Branch questions for the proposed reduction in boron concentrations for Surry Power Station cc: Mr. James P. 0 1 Reilly Mr. J. Don Neighbors Regional Administrator NRC Project Manager - Surry Region II Operating Reactors Branch No. l Division of Licensing Mr. D. J. Burke Mr. Charles Price NRC Resident Inspector Department of Health Surry Power Station 109 Governor Street Richmond, Virginia

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e ATTACHMENT 1 RESPONSE TO CONTAINMENT SYSTEMS BRANCH QUESTIONS FOR THE PROPOSED REDUCTIONS IN BORON CONCENTRATIONS FOR SURRY POWER STATION Question:

Provide the following information in support of the proposed boron concentration reduction in the boron injection tanks:

1. The mass and energy release data for the design basis main steam line rupture, based on a reduced boron concentration, and the computer code used to generate the data.

2. The results of the containment pressure/temperature analysis for the design basis steam line break and the computer code used to perform the analysis.

3. Alternatively, discuss the potential impact of a reduced boron concentration in the Boron Injection Tank on the containment response following a MSLB by, for example, reference to analyses performed for a similar plant.

Justify the acceptability for the approach used and the applicability of any referenced information.

Answer:

Vepco has performed an evaluation of the impact of the main steam line break transient with zero ppm boron in the Boron Injection Tank (BIT) on the Surry containment response.

With respect to the Surry containment temperature response, Vepco has used the LOCA temperature envelopes for post-accident equipment qualification in lieu of Main Steam Line Break (MSLB) temperatures as allowed by IE Bulletin 79-0lB and its supplements (Reference 1).

However, Vepco has performed sensitivity studies to address the impact of reducing the BIT boron concentration on early MSLB energy release

(<200 seconds), which dominate in influencing peak containment tempera-ture. We have concluded that, while the MSLB does not form the basis for the equipment qualification temperature envelopes for Surry, the effect of the proposed boron concentration changes on post-MSLB peak

e

• containment temperatures would not be significant.

An evaluation of the impact on the containment pressure analysis was also performed. This evaluation was perfonned by comparing mas*s

• and energy release data generated by the RETRAN computer code calculations discussed in Reference 2 with similar analyses performed for the Beaver Valley Power Station, documented in Reference 3. Vepco discussed the applicability of Beaver Valley results to the Surry Plant in Reference 4.

The comparisons perfonned show similar M&E release rates initially and significantly lower integral mass and energy releases for Surry at 30 minutes into the transient, which is the time at which auxiliary feedwater flow termination by the operator is assumed. At this tirne the Surry integrated 9

energy release is approximately 50% of the corresponding Beaver Valley values.

The primary reason for this difference lies in the margin between the Auxiliary Feedwater (AFW) flow rates assumed in the Beaver Valley analysis and those actually possible at Surry. The AFW flow to the faulted generator assumed in the contairvnent evaluation of Reference 3 was approximately 1600 gpm. This compares to a maximum flow of les~ than 400 gpm for the Surry units. This lower flow results from the presence of flow limiting venturis in the AFW discharge lines.

Examination of the analysis results from Reference 2 shows that the energy release rates beyond about 200 seconds into the transient are governed predominately by the AHJ flow rate, since the initial steam generator inventory has been depleted.

Vep~o has also reviewed the analyses and sensitivity studies performed in support of Beaver Valley's Boron Concentration Reduction Progrpm as submitted in Reference 5. It has been noted that all of the Reference 5 analyses also assume an AFW runout flow rate to the faulted generator on the order of 1600 gpm. As a result, we have concluded that the Beaver

e e Valley calculations (References 3 & 5) are bounding with respect to the expected Surry peak containment pressure following a secondary side break.

References

1. IE Bulletin No.79-018, "Environmental Qualification of Class IE Equipment," U.S. NRC Office of Inspection and Enforcement, January 14, 1980.

2. Letter from W. L. Stewart (Vepco) to H. R. Denton (NRC), "Amendment to Operating Licenses DPR-32 and DPR-37, Surry Power Station Units 1 and 2, Proposed Technical Specifications Change, 11 Serial No. 521, September 13, 1983.

3. Letter from C. N. Dunn (Duquesne Light) to A. Schwencer (NRC), "Beaver Valley Power Station, Unit No. 1, Docket No. 50-334, Auxiliary Feedwater/

Containment Pressure Analysis," November 31, 1979.

4. Letter from B. R. Sylvia (Vepco) to J.P. O'Reilly (NRC-Region II),

Surry Power Station Unit Nos. 1 and 2, Response to IE Bulletin No.

80-04, 11 May 8, 1980.

5. Letter from J. J. Carey (Duquesne Light) to S. Varga (NRC), "Beaver Valley Power Station, Unit No. 1, Docket No. 50-334, License No. DPR-66 Proposed Change Request No. 79 to Operating License," April 4, 1983.