ML20141M576
| ML20141M576 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 08/24/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20141M575 | List: |
| References | |
| NUDOCS 9209020054 | |
| Download: ML20141M576 (5) | |
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UNITED STATES e
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NUCLEAR REGULATORY COMMISSION
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SAFETY EVALVATION BY THr.0fflCE OF NUCLEAR REACTOR REGULATION B[ LATED TO AMENDHENT NO. 74 T0 FAClllTY OPERATING LICENSE NO. NPF-3S ENTERGY OPERATIONSu L WATERFORD STEAM ELECTRIC STATION. UNIT 3 DOCKET NO. 50-381
1.0 INTRODUCTION
By application dated May 11, 1992, Entergy Operations, Inc. (the licensee) submitted a request for changes to the Waterford Steam Electric Station, Unit 3 (Waterford 3), Technical Specifications (TS). The requested changes would revise TS 3/4.3.2, " Engineered Safety features Actuation Instrunentation," and TS 3/4/8/1, *A.C, Sources-Operating," to adjust the degraded voltage protection relay setpoints.
2,0 LyALUAT10N The staff has reviewed the licensee's submittal and provides the following evaluation.
During an NRC ;nspection conducted from December 4, 1990, through February 1, 1991, at Waterford 3, violations of NRC requirements were identified.
The violations involved a failure to verify or to check the adequacy of design and the failure to establish, follow, and maintain procedures appropriate to the circumstances.
2.1 Failure to Verify or to Check the Adequacy of Drsion Criterion 111 of Appendix B to 10 CFR Part 50 requires that design control measures be established for verifying or checking the adequacy of a design and for assuring that applicable regulatory requirements and the design basis are correctly translated into specifications, drawings, procedures, and instructions.
Contrary to the above, the degraded grid (undervoltage) relay setpoint calculations for Waterford 3 did not analyze for potential undervoltage conditions for Class IE loads at all onsite electrical system distribution levels.
The existing 4160 Vac undervoltage protective relays were set at trip setpoints that would have resulted in inoperable downstream 120 Vac safety-related equipment for degraded voltage conditions.
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2-2.2 Failure to Establish. Follow. and Maintain Procedures ADJroDriatt to the Circumstanees TS Section 6.8.1 requires that written procedures be established, implemented, and maintained for activities such as the calibration, testing, and adjustment of equipment that provides an interlock-permissive or -prohihit function.
Contrary to the above, Surveillance Procedures HE-003 319, "GE Undervoltage Relay Model 12NGV13B, Revision 4," directed setting the relay setpoints at Waterford 3 at the TS value without adequate consideration of tolerance or potential drift.
Furthermore, the proce-dures did not provide adequate guidance for engineering review responsibilities should the relay be found outside the acceptance band.
The following TS changes by the licensee are being proposed as a result of the above issues raised during the NRC Electrical Distribution System functional Inspection (EDSf!):
1.
In lable 3.3-4, " Engineered Safety feature Actuation System Trip Values of Specification 3/4.3.2," the " Trip Values" and " Allowable Values" for the 4160 volt emergency bus undervoltage (degraded voltage) are being changed from 2 3640 volts and 2 3604 to 2 3875 volts and 2 3860 volts, respectively.
2.
In Table 3.3-5, " Engineered Safety feature Response Time of Specification 3/4.3.2," the 4160 volt emergency bus undervoltage (degraded voltage) " Response Time in Seconds" is being changed from s 11 seconds to 5 14 seconds.
3.
In TS 3/4.8.1, "A.C. Sources", the emergency diesel generator minimum voltage of Surveillance Requirement 4.8.1.12 paragraphs A.4, 0.1, 0.3.b, 0.4, 0.5.b, and 0.6 is being changed from 4160 A 420 volts to 4160 +420/-240 volts.
2.3 Enaineered Safet_y_1galure Actuation System Trio Values The NRC, in reviewing protective relaying, concluded that the TS trip setpoint and-the allowable value for the 4160 volt bus degraded relays were too low to ensure proper operation of all Class IE equipment (i.e., downstream loads) if the bus voltage degraded down to a value slightly above the established setpoint.
In addition, the NRC found the existing G.E. NGV degraded (undervoltage) voltage relay to have excessive drift due to the adjustment potentiemeter..In response to the concerns Waterford 3 conducted an engineering review and reanalysis of the-electrical distribution system to establish the TS trip setpoints and allowable values for the degraded voltage relays.
The new analysis established a TS allowable value of 3860V (92.8% of 4160) and a trip value of 3875V (93.1 % of 4160V). The allowable value is based on the minimum voltage required by safety equipment plus uncertainty for equipment inaccuracy. The trip value is based on the allowable value plus the relay drift value.
Additional corrective actions involve installing new solid state relays (i.e. during refueling), conducting load flow and voltage drop
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- instruction 91-02.
The standing instruction, issued on January 23, 1991, is used to monitor the grid voltage for degraded 1
conditions.
When the grid decays to 223kV or less, operations personnel are required to.
1) trip the reactor, it critical; 2) start both emergency diesels;
- 3) after confirming satisfactory voltage and frequency of the emergency diesel generators (EDGs), separate the lE and non-lE buses by opening the tie breakers at the 4160 volt level; and 4) allow the EE to carry the safety-related loads until grid conditions i.; rove and the EDGs can be systematically shutdown.
2.4 Enaineered Safety Feature Response Time The degraded voltage " Response Time in Seconds" as pr. "ided in Table 3.3-5 is based on the relay timer setpoint. The degraded voltag relay timer setpoint
- is based on the time it takes for a motor to start and accelerate.
The degraded voltage protection system time relays accommodate the voltage drops resulting from starting motors by blocking actuation of the degraded voltage protection system.
If, during this time delay, the bus voltage recovers to a level tbove the reset value of the degraded voltage protection system, the syster.; will reset and no further action will be required.
Analysis done by the licensee determined the motor acceleration time to be 11.1 seconds.
This value was adjusted to include the timer tolerance of 110% and another i 10%
to accommodate potential positive drift.
The result of the analysis by the licensee was a degraded voltage relay response time setpoint of 14 seconds.
The analysis evaluated the impact on running motors at a voltage value slightly above the loss of voltage trip for the extended time delay to determine any detrimental effects, and concluded that running motors would not stall and motor qualifications would not be adversely impacted.
2.5 Emeroency Diesel Generator Minimum Voltaqq The final TS change is based on the revision of the reset values of the minimum voltage relay and assures that the minimum voltage output of the emergency diesel generator (EDG) is adequate before the bus loads are connected and the degraded voltage relays resets.
The current minimum voltage of'3740V will be changed to 3920V or 4160V minus 240V. This change will-ensure the degraded voltage relay will reset under the worst equipment drift and inaccuracy conditions.
The TS changes identified cove are supported by the new analysis and dependent upon several modifications to the electrical auxiliary system as briefly_ described below:
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. 1.
The control element drive mechanism (CEDM) fans presently do not trip upon initiation of a safety injection actuation signal (SIAS).
The control logic will be changed to trip all four CEDM fans upon initiation of a SIAS.
If the CEDM fans were not tripped, the degraded voltage setpoint would be higher and would potentially subject the degraded voltage relay to inadvertent trips.
2.
The three heater drain pumps will be tripped upon actuation of a generator lockout relay. The heater drain pumps are not required for safe shutdown.
If the heater drain pumps were not tripped, the degraded voltage relay would trip at a grid voltage slightly below the normal minimum voltage. Thus, tripping the heater drain nurps will allow the grid to degrade to a value well below the normal minimum grid voltage without tripping the degraded vnitage relay.
3.
The safety-related transformers for Power Distribution Panels 360/394-SA, 361/395-SB, 362/SAB, 3004-SA, and 3005-5 will have their tap setting changed from center to -5%.
This tap setting will improve the 120 volt system voltage to an acceptable value during a degraded voltage condition.
4, The present degraded voltage computer alarm will be modified to include an annunciator window that will alarm prior to tripping the degraded voltage relay.
This annunciator will warn the operator to beware of a potential trip due to degraded voltage and to avoid starting any motors.
5.
The load on Power Distribution Panel 360-SA will be balanced to provide a uniform voltage drop at the 120 volt system. This will.
improve the 120 volt system voltage to an acceptable value during a i
degraded voltage condition.
6.
The existing G.E. NGY electromechanical and agastat timing relays will be replaced with ABB 27N electronic relays.
The existing G.E.
relays were found to have excessive-drift due to the calibration potentiometer. The new relays have a self-test feature and a
" target" to indicate that the relay has tripped - features not present on the existing relays.
The electronic relays are more accurate (40.1%) and will be set to reset at approximately 0.4% (ISV) above setpnint.
7.
To increase voltage at the starter coils and other auxiliary devices (120V relays, solenoids, etc.) to an acceptable level during degraded conditions, some control cables will be paralleled or the existing control power transformer will be replaced with a larger transformer.
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1 2.6 Conclusion L
Branch Technical Position (BTP) PSB-1, 'Adoquacy of Station Electrical Distribution System Voltages," provided the criteria for determining adequate degraded voltage protection.
In an engineering review and reanalysis of the electrical distribution system, the licensee has addressed the requirements of BTP PSB-1 to establish the TS trip setpoints and allowable values for tha degraded grid relays.
The staff agrees that the revised trip settings, reset voltages, and tim: delays for the degraded voltage relays will help to establish an optimum voltage for all safety-related buses.
The proposed changes and modifications will not change the design, function, or method of operation of Class IE equipment at Waterford Unit 3 and will not create the possibility of a new or different kind of accident from any previously evaluated.
The staff concludes that the proposed TS changes and modifications described in this SE will improve the reliability and protection of Class IE equipment during degraded grid conditions and will not pose a threat to the public health and safety.
Therefore, these proposed changes to the Waterford 3 TS are acceptable.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Louisiana State official was notified of the proposed issuance of the amendment.
The State official had no comments.
4.0 ENVIRONMLNTAL C01SIDERAT10N The amendment changes a re<Jirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. The NRC staff has determined that the amendment involves 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 pro-posed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (57 FR 28200).
Accordingly, the amendment meets the elinibility 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 ste 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 amendment will not be inimical to the common defense-and security or to the health and safety of the public.
Principal Contributor:- M. Pratt Date:
August 24, 1992
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