ML20039C030
| ML20039C030 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/15/1981 |
| From: | VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | |
| Shared Package | |
| ML20039C027 | List: |
| References | |
| NUDOCS 8112280336 | |
| Download: ML20039C030 (4) | |
Text
i e ATTACIIMENT i Safety Evaluation For Proposed Technical Specifications Power Distribution Limits Changes For North Anna Unit Nos. 1 and 2 8112280336 811215" PDR ADOCK 05000338 P
ie SAFETY EVALUATION The Technical Specifications power distribution limits are primarily a function of the total heat flux peaking factor limit, Fq x K(Z)
(T.S. Figure 3.2-2), established by LOCA analyses. Adherance to the power distribution limits is specifically evaluated during each reload evaluation.
The key to the power distribution limits safety evaluation is whether the analytically predicted total heat flux peaking factor values (or flyspecks) are below the FQ x K(Z) curve. The methodology for the generation of the FQ flyspeck values is well established, and this methodology, which has been reviewed and approved by the NRC, is documented in Reference 1.
The relationship of the Technical Specifications power distribution limits to the analytically predicted total heat flux peaking factor values is discussed below.
Axially dependent Fxy limits are currently in the North Anna Technical Specifications. These limits are synthesized with appropriate axial power distributions for each reload cycle to determine the Fq flyspeck values. The Fq flyspeck values are then used to determine the appropriate axial power distribution surveillance and axial flux difference limits. The axial power distribution surveillance limit is expressed as a threshhold power level, Pm, above which axial power distribution surveillance is required. This value of Fm is determined from the ratio of the limiting Fq flyspeck value to the Fq x K(Z) curve at the same core elevation.
Similarly, the axial flux difference (AFD) limits include a threshold power level, P, above which a 15 minute time limit for restoration within the f
AFD target band is required, and an allowable range for short-term operation outside the AFD target band. Pf and the upper and lower allowable AFD
t e range parameters, R and R are related to P,as shown on Figure 3.2-1 of the u
g attached Technical Specifications and as discussed in Reference 2.
Lowering of the AFD limits below the generic limits is required only if the value of P is less than 100%. Consequently, the values of Pm and Pf, are evaluated m
prior to each reload cycle, and/or as a result of a new Fq x K(Z) curve being determined by a new LOCA analysis.
The removal of the specific Fxy, Pm, and Pf limit values from the Technical Specifications will not eliminate any of the licensee responsibili-ties for operating the reactor in compliance with the appropriate power distribution limits.
The proposed Technical Specifications changes will ensure provision of the Fxy and Pm limit values (the value for Pf is defined in the Technical Specifications as a function of P ) and the Fq flyspeck basis to the m
NRC in a supplemental report titled the Core Surveillance report. These limits will continue to be evaluated during the reload evaluation process as they are now, and the supplemental report will be provided to the NRC at least 60 days prior to the initial criticality for each fuel cycle.
The Vepco units have historically been LOCA limited with very little margin to thresholds associated with surveillance. As a rese1.t, complete reload safety evaluations have had to be submitted in the past to provide Technical Specifications changes when the analytically predicted total heat flux peaking factor value exceeded the Fq x K(Z) curve. Since the relationship between the generation of the analytically predicted total heat flux peaking factors and the Technical Specifications power distribution limits is well understood, it is not necessary to address these changes in reload safety evaluations with all of the accompanying licensing and administrative effort.
The attached Technical Specificatiens changes will climinate these costly and burdensome reload safety evaluation submittals which are required only to address Technical Specifications changes related to the LOCA analysis power distribution Itaits.
This change does not result in an unreviewed safety question.
i.
References 1.
Letter from Westinghouse (C. Eicheidinger) to NRC (J. T. Etolz) dated April 6, 1978, Serial No. 986C.
2.
T. Morita, et.al. " Power Distri'oution Control and Load Following Procedures", WCAP-8385, Westinghouse Electric Corporation, September, 1974.
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