ML20070D393

Application to Amend Licenses NPF-4 & NPF-7,allowing Optimization of Core Loading Patterns & Providing Addl Operating Flexibility

ML20070D393
Person / Time
Site:	North Anna
Issue date:	12/08/1982
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20070D396	List: ML20070D393
References
622, NUDOCS 8212150048
Download: ML20070D393 (9)

Text

6 VIRGINIA ELECTRIC AND Powan COMPANY RIcIIxoNn,VINGINIA 20 26I W. L. STEWAErr Vac. Prestomwr wuco. . o,.. mon. December 8, 1982 Mr. Harold R. Denton, Director Serial No. 622 Office of Nuclear Reactor Regulation FR/KLB: plc Attn: Mr. Robert A. Clark, Chief Docket Nos.: 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing License Nos: NPF-4 U.S. Nuclear Regulatory Commission NPF-7 Washington, D.C. 20555 Gentlemen:

AMENDMENT TO OPERATING LICENSES NPF-4 AND NPF-7 NORTH ANNA POWER STATION UNIT NOS. 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGE Pursuant to 10CFR50.90, the "irginia Electric and Power Company requests an amendment, in the form of changes to the Technical Specifications, to Operating License Nos. NPF-4 and NPF-7 for the North Anna Power Station Unit Nos. 1 and 2.

N Vepco proposes to change the existing Fxy and F fractional power 03 multiplier from 0.2 to 0.3. Enclosure 1 provides the Safety Evaluation for the proposed changes. These changes will ellow optimization of the core loading patterns and provide additional operating flexibility.

Minor changes to the core thermal limits and f(AI) function are required to implement the change; however no accident reanalyses are necessary.

The resulting specific Technical Specification changes are given in Enclosure 2. In addition, Enclosure 2 contains some administrative changes to the North Anna Unit 2 Technical Specifications designed to enhance the consistency between the North Anna 1 and 2 Technical Specifications. Specifically, the one-for-one reduction of the F g(Z) limit, when the F limit is exceeded, has been eliminated for North Anna Unit 2. Thischan{ehasbeenconfirmedwiththeNRCCore Physics Staff

( to be appropriate for a plant which is no longer required to use the Axial Power Distribution Monitoring System (APDMS) to ensure F limit compliance. O 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 10CFR50.59.

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VIMOINIA EMCTMIC AND POWER COMPANY TO Mr. Harold R. Denton 2 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 hazards consideration for Unit I 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 I and Unit 2, respectively. A voucher check in the amount of $4,400 is enclosed in payment of the required fees.

1 Very truly yours, 9

.i. 3(M~O W. L. Stewart a

Enclosure (1) SafetyEvaluationforproposedFxyand{H anges (2) Proposed Technical Specifications Changes (3) Voucher Check for $4,400 cc: Mr. James P. O'Reilly Regional Administrator Region II

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COMMONWEALTH OF VIRGINIA )

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CITY OF RICHMOND )

The foregoing document was acknowledged before me, in and for the City and Commonwe:.ilth aforesaid, today by W. L. Stewart, who is Vice President-Nuclear Operations, of the Virginia Electric and Power Company. He is duly authorized to execure and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this day of , 19 PA .

My Commission expires: 2-26 , 19 pr ,

0 . YYW Notary Public (SEAL)

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6 ENCLOSURE 1 b

SAFETY EVALUATION FOR A REVISED F AND Fxy H

PART POWER MULTIPLIER FOR NORTH ANNA UNITS 1 AND 2 Historically, increasing the allowable F with decreasing power has been H

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 North Anna Technical Specifications require a 0.7 part power multiplier on F AH and Fxy .

More recently, the NRC has approved a 0.3 part power multiplier and F and Fxy .

AH The results of the North Anna F H Technical Specification limit analysis indicate that the limit may be modified by changing the limit slope from 0.2 to 0.3 at reduced power, resulting in the following relationship:

+

F H < 1.55 [ 1.0 .3 (1-P) ] [ l - RBP (BU) J where P = fraction of rated thermal power. Note that the only change from the current Technical Specification is the multiplier on the quantity (1-P) from 0.2 to 0.3. No change is made in the F limit at full power.

H This change is requested for North Anna to allow optimization of the core loading pattern by minimizing restrictions on 8t 1 W Power. This change H

will also minimize the probability of making rod insertion limit changes to satisfy peaking factor criteria at low power with the control rod banks at the insertion limit.

The North Anna core thermal limits and axial offset Itaits for an increased allowaole at reduced power levels were determined using Vepco's version of the COBRA code 8 and the documented Westinghouse setpoint methodology . The core limits at 1875 and 2000 psia remain unchanged from the current limits. At 2250 and 2400 psia the proposed thermal core limits are slightly more limiting below 100 percent power. The core thermal limits only have these minimal changes because at most conditions below full power, the restriction that the average enthalpy at the vessel exit be less than the enthalpy of saturated liquid is more limiting than DNB considerations. This vessel exit enthalpy limit is not core peaking factor dependent.

For North Anna 1 (Technical Specifications based on an average temperature of 582.8 F) and North Anna 2 (Technical Specifications based on either the current average temperature of 580.3 F or the proposed value of 582.8 F), analysis has shown that no changes to the KI, K2, K3, K4, K5 or K6 factors are required in Table 2.2-1 of the Technical Specifications as a result of the new core thermal and axial offset limits. Therefore, since no changes to the overpower and overtemperature AT eetpoints are necessary, no accident reanalysis is required.

Minor changes to the current f(AI) function are required as a result of the new axial offset limits. The appropriate modifications to Table 2.2-1 of the Technical Specification are included in Enclosure 2.

In addition, reanalysis of the total peaking factor (FQ) versus core height curves for North Anna 2 Cycle 2 ' and North Anna 1 Cycle 4 were performed by Vepco using the documented Westinghouse FQ flyspeck methodology . The analyses assumed an Fxy limit at fractional thermal power with a part power multiplier of 0.3 instead of 0.2 as currently required. The analyses results demonstrated that the current FQ flyspecks on record for North Anna 1 and

2 were not impacted by the assumption of a 0.3 part power multiplier for Fxy and remain bounding. No change is made to the Fxy limit at full power.

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 both H

and Fxy does not result in an unreviewed safety questions. Appropriate Technical Specifications changes are provided in Enclosure 2.

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References:

1. Technical Specifications - North Anna Power Station Unit #1, Virginia Electric and Power Company

2. Technical Specifications - North Anna Power Station Unit #2, Virginia Electric and Power Company

3. " Reference Core Report 17x17 Optimized Fuel Assembly", WCAP-9500, Westinghouse Nuclear Energy Systems, July 1979 4 Letter from Mr. C. M. Trammell, III (NRC) to Mr. B. D. Withers (PGE),

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

5. Letter from Mr. S. Varga (NRC) to Mr. F. P. Librizzi (PSE&G), Amendment No.- 30 to Facility Operating License No. DPR-70 for the Salem Unit 1 Nuclear Plant", December 22, 1980

6. Letter from Mr. W. Ross (NRC) to Mr. R. A. Uderitz (PSE&PG), Amendment No.

6 to Facility Operating License No. DPR-75 for the Salem Unit 2 Nuclear Plant", March 29, 1982

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

8. S. L. Ellenberger, et.al., " Design Basis for the Thermal Overpower AT and Thermal Overtemperature AT Trip Functions", WCAP-8745 (proprietary),

Westinghouse Nuclear Energy Systems, March 1977

9. Letter from R. H. Leasburg (Vepco) to H. R. Denton (NRC), " Revised Core Surveillance Report for North Anna 2, Cycle 2", Serial Number 279, May 7, 1982

10. Letter from R. H. Leasburg (Vepco) to H. R. Denton (NRC), " Reload Information for Cycle 4, North Anna Nuclear Power Station Unit No. 1",

Serial Number 254, April 23, 1982

11. Letter from C. Eicheldinger (Westinghouse) to J. F. Stolz (NRC), Serial No. 986C, April 6, 1978

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