ML20117K422
| ML20117K422 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/05/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20117K406 | List: |
| References | |
| NUDOCS 9606110220 | |
| Download: ML20117K422 (3) | |
Text
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4 UNITED STATES s
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20665 4 001
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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 201 AND 182 TO FACILITY OPERATING LICENSE NOS. NPF-4 AND NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY l
OLD DOMINION ELECTRIC COOPERATIVE NORTH ANNA POWER STATION. UNITS N0. 1 AND N0. 2 DOCKET NOS, 50-338 AND 50-339
1.0 INTRODUCTION
By letter dated January 30, 1996, 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 (NA-1&2). The proposed amendments modify the TS to increase the minimum allowable reactor coolant system (RCS) total flow rate from 284,000 gpm (for Unit 1) and 275,000 gpm (for Unit 2) to 295,000 gpm for both units.
2.0 BACKGROUND
Through the 1980's and into the 1990's, the North Anna Unit 1 and 2 steam generators experienced increasing levels of steam generator tube plugging.'
There was a corresponding decrease in the reactor coolant flow rate.
As a result, the Commission issued several amendments in the 1989 to 1992 time l
frame to reduce the minimum reactor coolant flow rate. These reductions in minimum allowable RCS total flow rate reduced the available departure from i
nucleate boiling ratio (DNBR) margin.
Subsequently, the licensee replaced the steam generators in both units, with steam generators having an increased number of tubes compared to the replaced steam generators. With the increased number of tubes and less flow resistance, a greater reactor coolant flow rate is attainable. When the amendments were issued decreasing the minimum required reactor coolant flow rate, the transmittal letters stated the revision was temporary and would be increased when the steam generators were replaced.
3.0 CHANGES TO THE TECHNICAL SPECIFICATIONS a
I The following specific TS changes apply to Units 1 and 2 as noted:
Unit 1. Table 3.2-1. DNB Parameters. of TS 3.2.5 Change the existing criterion for Reactor Coolant System Total Flow Rate from "1 284,000***" to "2 295,000."
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Remove the following note from the bottom of Table 3.2-1 (page 3/4 2-15):
"*** The value for the minimum allowable Reactor Coolant System Total Flow Rate is reduced to 268,500 gpm until steam generator replacement."
Unit 2. Table 3.2-1. DNB Parameters. of TS 3.2.5 Change the existing criterion for Reactor Coolant System Total Flow a
Rate from "2 275,300" to "2 295,000."
1 4.0 EVALUATION The RCS flow rate is an assumption in safety analyses, affecting Updated Final Safety Analysis Report Chapter 15 transient analyses, Reactor Core Safety Limits, and thermal overtemperature and overpower A protection functions.
l An increase in the minimum RCS flow rate limit generates a benefit for safety analyses which have a DNBR acceptance criterion.
For other safety analyses which are limited by considerations such as heat sink or pressurization criteria, an increased RCS flow rate limit is either a benefit, or the event is insensitive to RCS flow rate.
The existing safety analyses are analyzed for a lower RCS flow rate limit, and are bounding with respect to expected actual plant behavior and to analyses at the proposed RCS total flow rate.
Th'; change when implemented will increase the available analysis margin and make the TS for the RCS total flow rate consistent for both North Anna, Units 1 and 2.
5.0 SVMMARY Based on its review, the staff finds the proposed changes to the TS acceptable.
6.0 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.
7.0 ENVIRONMENTAL CONSIDERATION
l These amendments change a requirement with respect to instailation or use of a ftcility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments 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
3 public comment on such finding (61 FR 7559). Accordingly, these amendments 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.
8.0 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 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: Bart Buckley Date:
June 5,1996 4
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