ML20059C922
| ML20059C922 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 12/23/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059C916 | List: |
| References | |
| NUDOCS 9401060209 | |
| Download: ML20059C922 (3) | |
Text
0
~
g a2
[
'o,,
UNITED STATES NUCLEAR REGULATORY COMMISSION t
o E
WASHINGTON, D. C. 20555 E
Og...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 22 AND R TO FACILITY OPERATING LICENSE NOS. NPF-87 AND NPF-89 TEXAS UTILITIES ELECTRIC COMPANY i
COMANCHE PEAK STEAM ELECTRIC STATION. UNITS 1 AND 2 DOCKET NOS. 50-445 AND 50-446
1.0 INTRODUCTION
By application dated September 10, 1992, Texas Utilities Electric Company (the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License Nos. NPF-87 and NPF-89) for the Comanche Peak Steam Electric Station (CPSES), Unit No.1.
By letter dated March 17, 1993, the application was expanded to include Unit 2.
The proposed changes would revise the Comanche Peak Steam Electric Station Technical Specifications (TS) Table 2.2-1 for the reactor trip system instrumentation trip setpoints. The first change will increase the "Z" value for the reactor coolant pump (RCP) undervoltage (UV) relay trip setpoint, Item 14 of TS Table 2.2-1, from 0 to 1.2 and the second change will lower the " Allowable Value" of the RCP underfrequency (UF) relay trip setpoint, Item 15 of Table 2.2-1, from " greater than or equal to" 57.1 Hz to " greater than or equal to" 57.06 Hz.
The proposed change for the RCP UV relay will account for the uncertainties introduced by the potential transformer (PT) accuracy class error that was not included in the previous RCP UV relay trip setpoint calculations. The current allowable value of " greater than or equal to" 57.1 Hz of the RCP UF relay trip setpoint is too close to the trip setpoint of 57.2 Hz and the maintenance personnel at Comanche Peak experienced difficulties in setting the UF relay at or above 57.1 Hz, but below 57.2 Hz.
The RCP undervoltage and underfrequency relays have been provided to monitor the power supply to'the RCP motors to prevent any unrecognized loss of the reactor cooling system on loss of all ac power to the RCPs. The RCP UV and UF relays are energized from the 6900 V RCP buses through 7200 V : 120 V potential transformers (PT ratio 60:1).
The current "Z" value for UV relay trip setpoint in TS Table 2.2-1, Item 14, and the " Allowable Value" of the UF relay trip setpoint, Item 15 of TS Table 2.2-1, are based on data in Westinghouse document WCAP-12123, Rev.1,
" Westinghouse Setpoint Methodology for Protection Systems Comanche Peak Unit 1".
This document specifies a calibration allowance of +/- 1.4 percent of span for UV relay and a calibration allowance of +/- 0.7 percent of span for UF relay. These calibration allowances correspond to UV relay trip i
9401060209 931223 PDR ADDCK 05000445 P
i
, setpoint between 80.08 V and 80.92 V and UF relay setpoint between 57.17 Hz and 57.23 Hz. The UV and UF trip settings are also specified in the Station documents El-2400, " Protective Devices Settings Document" and El-2700,
" Precautions Limitations and Setpoint Document." El-2400 specifies UV relay trip setpoint between 79.70 V and 81,70 V and UF relay trip setpoint between 57.1 Hz and 57.31 Hz. During a review of these documents to resolve these discrepancies, the licensee discovered that the PT accuracy class error had not been considered in the original setpoint calculations.
In addition, the maintenance personnel indicated that_they had experienced difficulty in adjusting the UF relay trip setpoint within the current band width.
2.
EVALUATION The licensee submitted a calculation, Calculation No. RXE-TA-CP1/0-027, Rev.1, covering the implications of the proposed changes. This alculation demonstrates that to account for the potential transformer accuracy class error the "Z" value for RCP UV relay trip setpoint should be increased from 0 to 1.2.
With this change the nominal trip setpoint for the RCP UV relay will remain unchanged at 4830 V (i.e., at 70 percent of system nominal voltage of 6900 V). The safety analysis limit for RCP UV is 4692 V.
For the RCP UF relay trip setpoint the licensee proposed to increase the relay adjustment allowance from one percent of the span to two percent of the span.
Calculation No. RXE-TA-cpl /0-027 indicates that with the proposed changes the nominal trip setpoint for the RCP UF relay will remain unchanged at 57.2 Hz (i.e., 95.33 percent of normal frequency 60 Hz). The calculation also indicates that with the proposed changes the minimum value of the RCP UF relay trip setpoint of 57.06 Hz will be above the upper bound of the safety analysis limit of 57.0 Hz. The calculation further demonstrates that with the proposed UV and UF changes, other parameters of Items 14 and 15 of TS Table 2.2-1 will remain unchanged.
The analysis the licensee submitted with the proposed changes indicates that the proposed changes will not alter the UV and UF relay trip setpoints or exceed the safety analysis limits or incorporate any physical change to UV and UF monitoring circuits. The licensee claims that the proposed changes will not alter the time sequence of events that could result in a decrease in reactor coolant system flow rates of Final Safety Analysis Report (FSAR)
Table 15.3-1 nor will they alter the transient curves of departure from nucleate boiling ratio (DNBR) versus time, FSAR Figure 15.3-12A, and core flow during coastdown, FSAR Figure 15.3-9A.
We have reviewed the justification provided by the licensee and agree that the proposed changes do not alter the trip setpoints of the RCP UV and UF relays and will not endanger the reactor cooling system. The proposed changes will better represent the "Z" value of the UV relay trip setpoint and provide relief in the setting of the UF relays.
-t
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The 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 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 exoosure. 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 19488). Accordingly, the 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 amendment.
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 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: Subinoy Mazumdar, NRR Date:
December 23, 1993 1
1 i
i 1
- -