ML20036C219
| ML20036C219 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 06/07/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20036C218 | List: |
| References | |
| NUDOCS 9306150305 | |
| Download: ML20036C219 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
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WASHINGTON, D. C. 20555 k....+,/
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 65 TO FACILITY OPERATING LICENSE NPF-68 l
AND AMENDMENT NO. 44 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER COMPANY. ET AL, l
V0GTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 f
QOCKET NOS. 50-424 AND 50-425 I
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1.0 INTRODUCTION
i By 1etter dated January 22, 1993, Georgia Power Company, et al. (the licensee) i proposed license amendments to change the Technical Specifications (TS) for Vogtle Electric Generating Plant (Vogtle), Units 1 and 2.
The proposed change would revise TS Table 2.2-1, " Reactor Trip System Instrumentation Trip Setpoints," and TS Table 3.3-3, " Engineered Safety Features Actuation System Instrumentation Trip Setpoints," to delete information that became obsolete l
once all steam generator (SG) instrumentation taps were relocated to elevation 1
333 inches. The proposed change would also revise the value of "Z" for the SG 1
level instrumentation. The Z-value represents the statistical summation of i
errors assumed for the instrument setpoints in various analyses (excluding errors associated with the sensor and rack drift and the accuracy of their measurement).
The Z-value is used in the TSs to determine reporting requirements.
j Specifically, the change would delete the footnotes in TS Table 2.2-1 and TS 1
Table 3.3-3 that read: "... the value stated inside the parenthesis is for i
instrumentation that has the lower tap at elevation 333 [ inches]; the value stated outside the parenthesis is for instrumentation that has the lower tap l
at elevation 438 [ inches)." The associated values within these tables that l
are outside the parenthesis, and their reference to these footnotes, would be deleted.
The changes to TS Table 2.2-1 apply to reactor trip due 'to Steam Generator Water Level Low-Low; this 2-value would be changed to 17.6.
The changes to TS Table 3.3-3 apply to turbine trip and feedwater isolation due to Steam Generator Water Level High-High; this Z-value would be changed to 10.47.
i The changes to TS Table 3.3-3 also apply to auxiliary feedwater actuation (start motor-driven pumps a:.d start turbine driven pump) due to Steam Generator Water Level Lo%-Low; these Z-values would be changed to 17.6.
2.0 EVALVATION I
2.1 CHANGE IN Z-VALUES Original calculations for determining SG level instrument settings and j
instrument-loop uncertainties were performed for the licensee by Westinghouse.
l For these calculations, Westinghouse used a value of 2% of span for the j
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process measurement accuracy. This value of 2% of span was based upon Westinghouse's best engineering judgement and was applied to their various models of SG design. This value was based on density variation as a function of power and level and the assumption that the calibration would be performed at 50% power.
i More recently, an improved understanding of errors associated with differential pressure measurement systems has prompted the licensee and Westinghouse to reexamine the process measurement accuracy terms for the SG level instrumentation loop. This improved understanding is based upon an Instrument Society of America paper, " Delta-P Level Measurement Systems," by G. E. Lang and J. P. Cunningham, presented in Instrumentation. Controls. and.
Automation in the Power Industry, Volume 34, Proceedings of the Thirty-Fourth Power Instrumentation Symposium, June 1991. Unlike the previous calculations, the revised calculations explicitly accounted for the effects of downcomer subcooling and changes in reference leg temperature from the calibration temperature. The revised calculations continue to account for fluid velocity effects. The previous assumption of calibration at 50% power conditions was replaced with an analysis based on the actual conditions assumed by the plant at the time of calibration. The licensee found that the revised calculations resulted in the need for small changes (less than 2.0 percent span) to the value of Z as given in existing TS Tables 2.2-1 and 3.3-3.
The licensee stated that it has removed unverified assumptions from the earlier SG level instrument-loop calculation and revised the calculation using the latest setpoint methodology, to determine loop uncertainty and setpoint.
The proposed change to the Z value does not affect setpoints or allowable values. The Z value is used only for determining when excessive instrument i
setpoint drift needs to be reported to NRC. The change in Z will not affect safety analyses or plant responses to accidents or transients, and will not affect any of the current operating requirements.
i The NRC staff finds the newer method used to calculate the Z values to be acceptable. The resulting change to the Z values does not have an adverse affect upon safety and is, therefore, acceptable.
2.2 REMOVAL 0F OBSOLETE INSTRUMENTATION VALUES FOR STEAM GENERATOR LEVEL l
On August 30, 1990, the NRC issued Amendments 34 (Vogtle Unit 1) and 14 (Vogtle Unit 2). These amendments added footnotes and additional values for SG level instruments to provide for a plant modification to relocate the lower instrumentation tap from an elevation of 438 inches to 333 inches (as measured from the top of the SG tubesheet). Because the plant modifications were to be implemented on the two Vogtle units at different times, Amendments 34 and 14 specified appropriate setpoints, allowable values, and data for instrumentation utilizing either a lower tap at 333 inches or a lower tap at 438 inches.
i Plant modifications have now been completed for both Vogtle units. Thus, the information in the TS for the instrumentation tap at 438 inches is obsolete and the licensee has requested that this information be deleted.
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. The NRC staff finds that the removal of this information is of an t
administrative nature and has no adverse affect upon safety. This proposed change is, therefore, acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Georgia State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements 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 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 the amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 16861 dated March 31, 1993).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR Sl.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 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 Contributors: D. Hood S. Athavale Date: June 7, 1993