ML20056H450
| ML20056H450 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/07/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056H449 | List: |
| References | |
| NUDOCS 9309090342 | |
| Download: ML20056H450 (3) | |
Text
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E UNITED STATES 5;
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555K01 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS.174 AND 155 TO FACILITY OPERATING LICENSE N05. NPF-4 AND NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY OLD DOMINION ELECTRIC COOPERATIVE NORTH ANNA POWER STATION. UNITS NO. 1 AND NO. 2 DOCKET NOS. 50-338 AND 50-339
1.0 INTRODUCTION
Pursuant to 10 CFR 50.90, by letter dated May 24, 1993, the Virginia Electric and Power Company (the licensee) proposed changes to the Technical Specifications (TS) for the North Anna Power Station, Units 1 and 2.
The changes would increase the as-found main steam safety valve (MSSV) setpoint tolerance from 1% to 3% of nominal setpoint pressure.
2.0 PROPOSED TECHNICAL SPECIFICATION CHANGES Table 3.7-2 would be changed to indicate a lift setting of (+/-)3% rather than
(+/-)1% and add a note specifying that all steam line safety valves shall be returned to an "as left" lift setting of their nominal lift setting (+/-)1%.
Basis section 3/4.7.1.2, auxiliary feedwater system, would be changed to reflect the reduction in the minimum auxiliary feedwater (AFW) flow rate, expand the discussion on pump surveillance testing, and clarify the basis.
3.0 EVALUATION There are a total of five ASME Code safety valves located on each of the main steam lines outside the reactor containment. The valves have setpoints of 1085, 1095, 1110, 1120, and 1135 psig. The Code safety valves ensure that the secondary system pressure will be limited to within 110% of the system design pressure during the most severe anticipated system operational transient.
The existing setpoint tolerance is 1%; haaver, the valves have been found to drift outside this tolerance. The licensee states that there is ample margin in the safety analyses and evaluations supporting operation to justify a relaxation of the allowable as-found setpoint tolerance from 1% to 3%.
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. Several Licensee Event Reports (LERs) concerning the "as-found" lift setpoints being outside the 1% tolerance at North Anna were reviewed.
Several "as J
found" lift setpoint values were also outside the 3% tolerance.
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The licensee states that the safety analysis design inputs or safety analysis criteria affected by the proposed increased tolerance include the Locked Reactor Coolant Pump Rotor and the Loss of Load transients. The Loss of Normal Feedwater, Main Feedline Break, and Loss of Offsite Power transients were also considered in the licensee's evaluation and found to be bounded by safety analysis criteria.
Transient analyses assuming a 3% setpoint tolerance demonstrated that the maximum primary and secondary pressure safety limits would not be exceeded for the Locked Rotor or the loss of Load events.
The effect of higher backpressure on the AFW system and the resulting effect on decreasing AFW flowrate was also evaluated. This evaluation resulted in the licensee taking credit for existing safety analysis margin and reducing the assumed AFW system flow rate from 340 gpm to 300 gpm.
The licensee stated that the transient analyses had already been incorporated into the North Anna design basis via 10 CFR 50.59 including the application of a 3% MSSV setpoint tolerance. The licensee evaluated each pertinent safety criterion for an increased MSSV setpoint tolerance and all were found to be acceptable.
4.0
SUMMARY
The changes will not affect the capability of the MSSVs to perform their design function.
Primary and secondary pressure safety limits will not be exceeded in the most limiting overpressure transients with the MMSV lift setpoint tolerance increased from 1% to 3%. The staff finds the licensee's proposed revisions to the TS to be acceptable.
5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Virginia State official was notified of the proposed issuance of the amendment.
The State official had no comment.
6.0 ENVIRONMENTAL CONSIDERATION
These amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendmen+s involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no i
public comment on such finding (58 FR 36448). Accordingly, these amendments i
f meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such i
activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
R. P. Croteau Date: september 7,1993 L
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