ML18139C321

Application for Amend to Licenses DPR-32 & DPR-37,changing Tech Specs to Allow Optimization of Core Loading Patterns & Provide Addl Operating Flexibility by Changing Existing Fractional Power Limit

ML18139C321
Person / Time
Site:	Surry
Issue date:	05/02/1983
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton, Varga S Office of Nuclear Reactor Regulation
Shared Package
ML18139C322	List: ML18139C321 ML18139C323
References
250, NUDOCS 8305060556
Download: ML18139C321 (8)

Text

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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 W. L. STEWART VICE PRESXDE:NT NUCLEAR OPERATIONS May 2, 1983 Mr. Harold R. Denton, Director Serial No. 250 Office of Nuclear Reactor Regulation NO/WDC:acm Attn: Mr. Steven A. Varga, Chief Docket Nos. 50-280 Operating Reactors Branch No. 1 50-281 Division of Licensing License Nos. DPR-32 U. S. Nuclear Regulatory Commission DPR-37 Washington, D. C. 20555 Gentlemen:

AMENDMENT TO OPERATING LICENSE DPR-32 ND DPR-37 SURRY POWER STATION UNITS NO. 1 AND NO. 2 PROPOSED TECHNICAL SPECIFICATIONS CHANGES Pursuant to 10CFR50.90, the Virginia Electric and Power Company hereby requests an amendment, in the form of changes to the Technical Specifications, to Operating Licenses DPR-32 and DPR-37 for the Surry Power Station, Unit Nos.

1 and 2. The proposed changes are enclosed.

In order to allow optimization of the core loading patterns and provi~e additional operating flexibility, Vepco proposes to change the existing Fb,H fractional power limit to the form:

F!H = 1.55 (1 + 0.3 (1-P))

where Pis the fraction of rated power. We noted our intention to do this in our letter, dated November 22, 1982 (Serial No. 619). Enclosure 1 provides the Safety Evaluation for the proposed changes. Changes to the core thermal limits, overtemperature and overpower 6T setpoints, and the f( 6 I) function are required to implement this change. The resulting specific Technical Specification changes are given in Enclosure 2.

In particular, we are interested in restoring operating flexibility for Surry 1 Cycle 7 which has been lost as a result of the revised rod insertion limits.

As noted in the Reload Safety Evaluation for Surry 1 Cycle 7 transmitted by our letter dated April 14, 1983 (Serial No. 238), and restated in the Safety Evaluation provided in Enclosure 3, all design constraints, except the predicted radial power peaking factor are met for the rod insertion limits shown in Enclosure 4. A 0.3 part power multiplier will provide substantial additional radial power peaking factor design margin at low powers. Based on the rod insertion limits shown in Enclosure 4, t;Jie predicted radial power peaking for Cycle 7 will be below the proposed FB.H (O. 3 multiplier) design limit for hot zero power at all times in Cycle 7 lifetime. In addition, the hot full power radial power peaking factors are predicted to be below the design limit by 1000 MWD/MTU of cycle lifetime. Therefore, we are interested in receiving your approval of the Technical Specifications changes provided in Enclosures 2 and 4 by approximately June 1 , 1983, in order to res tore the operating flexibility for Surry 1 Cycle 7 following 1000 MWD/MTU core burnup .

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e VIRGINIA ELECTRIC A.ND POWER COMPANY TO Harold R. Denton This request has been reviewed and approved by the Station Nuclear Safety and Operating Committee and the Safety Evaluation and Control Staff. It has been determined that this request does not involve any unreviewed safety questions as defined in 10CFRS0.59.

We have reviewed this request in accordance with the criteria in 10CFR170.22.

Since this request involves a safety issue which the staff should be able to determine does not involve a significant hazard consideration for Unit 1 and a duplicate safety issue for Unit 2, a Class III license amendment fee and a Class I license amendment fee are required for Unit 1 and Unit 2, respectively. A voucher check in the amount of $4,400 is enclosed in payment of the required fees.

Very truly yours,

(\

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W. L.

Enclosure (1) Safety Evaluation - 0.3 Part Power Multiplier (2) Proposed Technical Specification Changes - 0.3 Part Power Multiplier (3) Safety Evaluation - Revised Rod Insertion Limits for Surry Unit 1 (4) Proposed Technical Specification Changes - Revised Rod Insertion Limits (5) Voucher Check for $4,400 cc: Mr. James P. O'Reilly Regional Administrator Region II Mr. Donald J. Burke NRC Resident Inspector Surry Power Station

e ENCLOSURE 1 SAFETY,,- EVALUATION FOR 1

. A REVISED ~H PART POWER f1ULTIPLIER

calculation of F~H versus power level for Surry Unit 1, Cycle 7 (using the raised insertion limits) and Surry Unit 2, Cycle 7 compared to the current and proposed Technical Specification limits on F:H.

The Surry core thermal limits and axial offset limits for an increased allowable F~Hat reduced power levels were determined using Vepco's version of the COBRA code 6 and standard Westinghouse methodology. These analyses retain the fuel densification power spike 7 for DNBR calculations as part of

/

the generic margin to accommodate the effects of rod bow 8 , 9

• The DNB limited portion of the core thermal limits became slightly more restrictive at N

powers less than 100%, reflecting the change in the F~H part power multiplier. The vessel exit enthalpy limits, which form the major portion of the core thermal limits below 100% power, are not core peaking factor dependent.

The overtemperature and overpower ~T Kl, K2, K3, -K4, KS and K6 factors given in Section 2.3 of the Technical Specifications were recalculated based on the new core thermal limits using the documented Westinghouse setpoint methodology 10

• The analysis resulted in insignificant changes to these factors as can be seen in Enclosure 2. However, since the Kl term increased slightly, confirmatory analyses were performed to verify that the revised constants and resulti~g setpoints are appropriate. These consisted of evaluating the rod-withdrawal-at-power transient over a bounding range of reactivity insertion rates. This transient represents the bounding transient with respect to these setpoints.

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e e SAFETY EVALUATION FOR A REVISED F~H PART POWER MULTIPLIER FOR SURRY UNITS l AND 2 Historically, incre.asing the allowable F! with decreasing power has been permitted for all previously approved Westinghouse designs. The increase is permitted by the DNB protection setpoints and allows for radial power distribution changes with rod insertion to the insertion limit. The current Surry Technical Specifications require a 0.2 part power multiplier on FN l tH

• More recently, the NRC has approved a 0.3 part power multiplier on F6NH 2, 3, 4 The results of the Surry F:H Technical SpeGification limit analy~~s for full thermal design flow indicate that the limit may be modified by th*anging the limit slope from 0.2 to 0.3 at reduced power, resulting*"in the following relationship:

FN6H-

< 1.55 {1.0 + 0.3 {1-P))

where P = fraction of rated thermal power. Note that the only change from the current F~H Technical Specification is the multiplier on the quantity {l-P) from 0.2 to 0.3. No change is made in the F~H limit at full power.

This change is requested for Surry to allow optimization of the core loading pattern,by minimizing restrictions on F:i at low power. This change will also minimize the probability of making rod insertion limit changes to satisfy peaking factor criteria at low power with the control banks at the insertion limit as was required for Surry Unit 1, Cycle 7 5

• Figures land 2 show the cdk/0426C/1

e The currently licensed f(~I) function, which is applied to both the overtemperature ~T and the overpower ~T setpoints, was developed using a conservative "flyspeck" approach lO, 11

• This "flyspeck" included FQ's for axial power distributions generated without constant axial offset control.

The new f(~I) is based on Constant Axial Offset Control 12 with a ~I band of

+5%, consistent with Surry operation. As a result of this, the new f(~I),

shown in Figure 2.3-1 of the attached Technical Specification changes, has a wider deadband and a flatter slope for the positive ~I line segment.

As a result of our analyses, we have determined that the modification of the 0.2 fractional power multiplier to a value of 0.3 for F~H does not result in an unreviewed safety question. Appropriate Technical Specifications changes are provided in Enclosure 2*.

cdk/0426C/3

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REFERENCES:

l. Technical Specifications - Surry Power Station Units l and 2, Virginia Electric and Power Company.

2. "Reference Core Report 17 x 17 Optimized Fuel Assemb ly 11 , WCAP-9500 ~

Westinghouse Nuclear Energy Systems, July 1979.

3. Letter from Mr. C. M. Trammell, III (NRC) to Mr. B. D. Withers (PGE),

"Amendment No. 76 to the Facility Operating License No. NPF-1 for the Trojan Nuclear Plant", August 13, 1982.

4. Letter from Mr. L.B. Engle (NRC) to W. L. Stewart (Vepco) dated April 22, 1983.

5. Letter from w. L. Stewart (Vepco) to H. R. Denton (NRC) Serial No. 238, dated April 14, 1983, Attachment 2, "Reload Safety Evaluation for Surry Un it 1 Cycle 7 Redesigned Core

• 11

6. F. W. Sliz, 11 Vepco Reactor Core Thermal-Hydraulic Analysis using the COBRA-Ille/MIT Computer Code", VEP-FRD-33, Virginia Electric and Power Company, August 1979.

7. "Fuel Densification - Surry Power Station Unit l 11, WCAP-8012 (proprietary), Westinghouse Nuclear Energy Systems, December 1972.

8. C. Eicheldinger (Westinghouse) to V. Stello (NRC) letter dated August 13, 1976, Serial No. NS~CE-1163.

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e

9. A. Schwencer (NRC) to W. L. Proffitt (Vepco) letter dated July 27, 1979.

10. S. L. Ellenberger, et.al, "Design Basis for the Thermal Overpower.t:i.T and Thermal Overtemperature .6.T Trip Functions", WCAP-8745 (proprietary),

Westinghouse Nuclear Energy Systems, March 1977.

11. A. F. McFarlane, "Topical Report - Power Peaking Factors", WCAP-7912 (proprietary), Westinghouse Nuclear Energy Systems, March 1972.

12. T. Morita, et. al, "Topical Report - Power Distribution Control and Load Following Procedures", WCAP-8383 (proprietary)., Westinghouse Nuclear Energy Systems, September 1974.

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