ML20077F708
| ML20077F708 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/30/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20077F698 | List: |
| References | |
| NUDOCS 9412150024 | |
| Download: ML20077F708 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.174 TO FACILITY OPERATING LICENSE NO. DPR-16 GPU NUCLEAR CORPORATION AND JERSEY CENTRAL POWER & LIGHT COMPANY OYSTER CREEK NUCLEAR GENERATING STATI0B DOCKET N0. 50-219
1.0 INTRODUCTION
During the electrical distribution functional inspection (EDSFI), a Nuclear Regulatory Commission (NRC) inspection team found that undervoltage protection for degraded grid voltage was not adequate to ensure that accident mitigating equipment would get sufficient voltage to perform their safety function.
By letter dated July 8, 1994, as supplemented October 10, 1994, GPU Nuclear Corporation (licensee) requested a revision to the Technical Specification to change the degraded voltage relay setpoints from 3671 volts (88.5% of 4160V) to 3840 volts (92.3% of 4160V), and to revise the allowable setpoint range from i 1% to +20V, -40V.
The revised setpoint tolerance values in volts represents a range of +0.5%, -1.0% compared to the existing setpoint tolerance range of 1%.
The current Technical Specification degraded voltage time delay setting of 10 10% seconds is not changed.
The setpoint change is being proposed in conjunction with modifications to the 480V system, and some related field testing and verification at the 120V level is ongoing.
The staff requested some additional information which was provided by a letter on October 10, 1994. The licensee has committed that any additional modifications identified will be completed by the end of the next refueling outage.
Because of this ongoing work, the licensee has also proposed some administrative controls to be used in the interim until the final system modifications are completed.
2.0 EVALUATION The licensee reanalyzed the electrical distribution system to determine the voltage available at the terminals of required Class IE ac electrical equipment by using DAPPER computer program. The analysis included determining the running and starting voltages for the 4160V and 480V equipment, voltages for motor starter pickup and dropout, and available voltages at the terminals 9412150024 941130 DR ADOCK 0500 9
e of 120V equipment. The evaluation utilized updated power and control cable lengths for 480V and 120V Class 1E equipment, and reflected the current electrical configuration of the plant and consideration of the impact of planned modifications at the 480V level.
The licensee's proposed setpoint of 3840V (92.3% of 4160V) at the 4.16kV bus results in voltages higher than the motor starter pickup value (85%) at the 480V level. At the proposed setpoint, and with the 480V modifications, all
'l equipment at the 4160V and 480V level will operate at voltages above the minimum required.
The licensee has verified the base model for DAPPER computer program against field measurements. The field testing is ongoing during the current outage to l
verify 120V system voltage drops and current values. Measured voltage and current values will be compared to analysis assumptions. ' Any modifications to these 120V circuits identified as a result of this reanalysis are to be i
completed by the end of next refueling outage, The revised setpoint for the-degraded voltage relay includes the relay drift, potential transformer inaccuracy, and calibration tolerances, plus an additional safety margin.
The staff has determined that the revised degraded voltage setpoint will improve the level-of protection for the safety related electrical equipment from loss of capability in the event of a sustained degraded voltage condition. However, based on the conservative assumptions used in the analysis (with respect to degraded grid voltage and a LOCA), the increased setpoint would not protect some electrical equipment at the 480V and 120V levels. Therefore, the licensee is performing modifications, additional analysis and field measurements to establish appropriate final resolutions for this equipment.
They have committed that any modifications resulting from the i
final resolutions will be completed by the end of the next refueling outage.
As added protection for this equipment, until the final implementation of all needed modifications, the licensee has established interim administrative controls to monitor the 4.16kV bus voltages and ensure that bus voltage is 4100V or greater and to take corrective actions as necessary to improve voltages and ensure that the 120V vital loads are powered from regulated sources.
These interim controls, combined with the low probability of the postulated worst case conditions, provide reasonable assurance that the 480V and 120V components will have adequate voltage to perform their safety function in the interim.
Based on the above evaluation, the staff concludes that the revised degraded voltage setpoint and administrative controls will provide adequate protection from the adverse effects of sustained degraded voltages in the interim and are, there/ ore, acceptable.
In addition, the staff concludes that the revised degraded voltage setpoint and the implementation of the identified
q t modifications will ensure adequate voltage to all required safety related equipment under postulated worst case conditions for the longer term, and this is, therefore, acceptable for the final resolution.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the New Jersey State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, aad 51.35, an environmental assessment and finding of no significant impact have been prepared and published in the Federal Reaister on November 17, 1994 (59 FR 59443). Accordingly, based upon the environmental assessment, the staff has determined that the issuance of the amendment will not have a significant effect on the quality of the human i
environment.
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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
N. K. Trehan Date:
November 30, 1994
.