ML20078C936
| ML20078C936 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 01/20/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078C934 | List: |
| References | |
| NUDOCS 9501270169 | |
| Download: ML20078C936 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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f WASHINGTON, D.C. 20066-0001 j
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 1
l RELATED TO AMENDMENT NO.127 TO FACILITY OPERATING LICENSE NPF-35 AND AMENDMENT NO.121 TO FACILITY OPERATING LICENSE NPF-52 DUKE POWER COMPANY. ET AL.
I CATAWBA NUCLEAR STATION. UNITS 1 AND 2 i
j DOCKET NOS. 50-413 AND 50-414 i
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1.0 INTRODUCTION
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By letter dated August 25, 1994, as supplemented November 16, 1994, Duke Power Company, et al. (the licensee), submitted a request for changes to the Catawba 4
Nuclear Station, Units 1 and 2, Technical Specificatio,s (TS). The requested i
changes would change TS. Table 3.3-4, " Engineered Safety Features Actuation i
System Instrumentation Trip Setpoints" by revising the " Trip Setpoint" and j
" Allowable Value" for the 4 kV bus undervoltage grid degraded voltage relays -
and the " Allowable Value" for the 4 kV undervoltage loss of voltage / loss-of-j offsite power relays. This revision was submitted in response to a concern i
identified by the licensee in their Self-Initiated Technical Audit (SITA) and
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during the electrical distribution system functional inspection (EDSFI) team findings. The November 16, 1994, letter provided clarifying information that j
did not change the scope of the August 25, 1994, application and the initial proposed no significant hazards consideration determination.
l The two trains of the 4160 volt ac essential auxiliary power system are each provided with two levels of undervoltage protection. The first level detects i
a loss of voltage.
The relays will drop out if the voltage falls below 3500 volts for more than 10 cycles. This 3500 volt setpoint, identified as " Loss of Offsite Power" or " Loss of Power /4KV Bus Undervoltage-Loss of Voltage,"
j appears in five functional units in Table 3.3-4.
It did not require i
modification for the reasons discussed below. However, the allowable value i
for this parameter did require a change from 3200 volts to 3242 volts. The j
second level of protection provides degraded voltage detection and alarms and drops out after established time delays. This parameter, identified as " Loss of Power /4KV Bus Undervoltage-Grid Degraded Voltage," appears once in Table
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3.3-4.
Its setpoint was changed from 3685 to 3766 volts and its allowable j
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value was changed from 3611 to 3738 volts.
t As noted above, the " Trip Setpoint" for the 4 kV loss-of-voltage / loss-of-offsite power does not require any change. This is because the existing TS trip setpoint is already at a more conservative value than required.
The licensee's original calculation for establishing these parameters did not account for all variables in determining the relay settings. The consideration of those variables is required in order to determine the 9501270169 950120 i
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i appropriate relay Trip Setpoint and Allowable Value. The new calculation l
includes allowance for these variables. The proposed revision is a result of i
the licensee's SITA and the EDSFI team evaluation.
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2.0 EVALUATION The staff has evaluated the proposed revisions submitted by the licensee as follows:
l Revision to Existina TS Table 3.3-4 i
l The licensee has proposed to revise the " Engineered Safety Features Actuation i
Instrumentation Trip Setpoints," TS Table 3.3-4 for the 4 kV essential power
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system which supplies power to those Class 1E loads required to safely shut down the unit following a design basis accident. The system is divided into two completely redundant and independent trains.
Each redundant 4 kV essential bus is provided with two levels of undervoltage protection to monitor bus voltage. Each level is provided with a separate set of three undervoltage relays which are utilized in a two-out-of-three logic scheme.
l The proposed changes are as follows:
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l 11gm.fLt:
Loss of Offsite Power:
Under " ALLOWABLE VALUE" change "2 3200" volts to "2 3242" volts.
Item 10.a:
4 kV Bus Undervoltage Loss of Voltage:
Under " ALLOWABLE VALUE" change "2 3200" volts to "2 3242" volts.
Item 10.b:
4 kV Undervoltage Grid Degraded Voltage: Under " TRIP SETPOINT" change "2 3685" volts to "2 3766" volts, and under " ALLOWABLE VALUE" change "2 3611" volts to "2 3738" volts.
Item II.b:
Loss of Offsite Power: Under " ALLOWABLE VALUE" change "2 3200" volts to "2 3242" volts.
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Item 14.c:
Loss of Offsite Power:
Under " ALLOWABLE VALUE" change "2 3200" l
volts to "2 3242" volts.
Item 15.c:
Loss of Offsite Power: Under " ALLOWABLE VALUE" change "2 3200" l
volts to "2 3242" volts.
The first level of undervoltage relays detects a loss of voltage on the 4 kV essential bus.
The TS trip setpoints for the loss of voltage / loss of offsite power do not require any changes because the existing TS trip setpoints are already at a more conservative value than required by the calculation. The allowable value for the loss-of-voltage / loss-of-offsite power was revised to 2 3242 volts to account for instrument errors which were not considered in the licensee's original calculation.
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' The second level of undervoltage protection provides degraded voltage protection. The EDSFI team evaluation identified that the reset-to-dropout ratio of the degraded voltage relays was high, approximately 105 percent.
This wide reset band could allow unnecessary actuation of the undervoltage protection system.
In response to the EDSFI team concerns, the licensee replaced the degraded voltage relays with a model that has a narrower tolerance band and better pickup-to-dropout ratio. Also, the licensee's original calculation was non-conservative in that the voltage drop analysis i
l only went down to the 4 kV level rather than the 120 volt level. Also, the l
calculation did not account for all possible errors in determining the relay settings. The allowance for error in the calculation is required in order to determine the minimum allowable value and the relay trip setpoint. The new calculation includes all possible errors, tolerances, and drift considerations in the determination of the trip setpoint of the relay. The licensee also did a new voltage drop analysis that went down to the 120 volt level on all essential buses. The calculation specifies a trip setpoint of 2 3766 volts (approximately 90.5% of nominal bus voltage) with a revised aliowable value of 2 3738 volts (89.9% of nominal bus voltage).
Branch Technical Position (BTP) PSB-1, " Adequacy of Station Electrical Distribution System Voltages," provided the criteria for determining adequate degraded voltage protection. The licensee conducted an engineering review and reanalysis of the Electrical Distribution System, which involved adequately addressing the EDSFI results and the requirements of BTP PSB-1, in order to establish the technical specification trip setpoint and allowable value for grid degraded (undervoltage) relays. The proposed revision does not change the design, function, or method of operation of Class IE equipment at Catawba, Units 1 and 2.
This proposed TS modification requires no change to the actual field settings because the current settings of the affected relays are in conformance with the proposed values.
Based on the above evaluation, the staff finds the proposed changes to l
Catawba, Units 1 and 2, T5 to be acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina 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 typen, 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 i
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amendments involve no significant hazards consideration, and there has been no public comment on such finding (59 FR 51619 dated October 12,1994).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursu:nt to 10 CFR 51.22(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 Contributor: Charles R. Thomas Date:
January 20, 1995 i
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