ML19329B055

Safety Evaluation Supporting Revision of Tech Spec Table 3.2-1, DNB Margin Reactor Coolant Flow Rates to Accommodate DNBR Penalty Per OL Condition

ML19329B055
Person / Time
Site:	Davis Besse
Issue date:	04/10/1978
From:	TOLEDO EDISON CO.
To:
Shared Package
ML19329B053	List: ML19329B052 ML19329B055
References
NUDOCS 8001300653
Download: ML19329B055 (1)

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DB-1 SAFETY EVALUATION To accommodate the DNBR Fuel Rod Bow Penalty of 11.2%, a 1% credit for the Flow Area Reduction Factor and a 1.11% credit for the DNB Power Spike Factor is being taken. The Flow Area Reduction Factor is described in Section 4.4 of the Davis-Besse Nuclear Power Station Unit No. 1 FSAR.

The DNB Power Spike Factor is described in Topical Report BAW-1401, titled " Davis-Besse Unit 1 Fuel Densification Report", incorporated by reference in Section 1.6.1 of the Davis-Besse Unit 1 FSAR. Our thermal-hydraulic analysis shows the remaining part of the Fuel Rod Bow Penalty can be offset by a reactor coolant flow rate in excess of 104.5% of the design flow. The minimum required flow rates in Table 3.2-1 of the Technical Specifications have been increased to 105% of designed flow rate for additional conservatism. Analysis of Davis-Besse Unit 1 flow determination test data at powers up to 90% of rated thermal power indicates a flow rate in excess of 110% of design flow rate.

Safety analyses provided in Chapter 15 of the Davis-Besse Unit 1 FSAR are based upon design flow with the criterion that design flow is the minimum reactor coolant flow that will be measured during plant operation. The increased DNBR afforded by reactor coolant flow in excess of design has a beneficial effect on the safety analyses and as such it is concluded that 105% of design reactor coolant flow constitutes an acceptable operating mode and is bounded by FSAR Chapter 15 events. Consequently the changes in the technical specifications will be an improvement and the changes will not adversely affect plant safety.

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