ML20079B284
| ML20079B284 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 12/14/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20079B281 | List: |
| References | |
| NUDOCS 9501050387 | |
| Download: ML20079B284 (4) | |
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4 UNITED STATES 2
E NUCLEAR REGULATORY COMMISSION E
f WASHINGTON, D.C. 10666 4 001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS.162 AND 143 TO FACILITY OPERATING LICENSE N05. DPR-70 AND DPR-75 PUBLIC SERVICE ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY i
ATLANTIC CITY ELECTRIC COMPANY SALEM NUCLEAR GENERATING STATION. UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311
1.0 INTRODUCTION
By letter dated March 28, 1994, as supplemented June I and August 24, 1994, the Public Service Electric & Gas Company (the licensee) submitted a request for changes to the Salem Nuclear Generating Station, Unit Nos. I and 2, 1
Technical Specifications (TS). The requested changes would revise the sustained degraded voltage relay trip setpoint and the allowable value due to changes in the switchyard configuration. The June I and August 24, 1994, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 BACKGROUND
PSE&G has implemented modifications to the Unit I and Unit 2 switchyard configuration that consist of new 500/13-kV station power transformers, new 13-kV circuit breakers, and new 13/4-kV station power transformers. The new equipment will continue to provide the two offsite sources of power to the three vital buses as well as power to a new non-vital 4-kV bus.
PSE&G performad calculations to support the switchyard modifications in order to determine the minimum vital bus voltage necessary to maintain vital loads within their voltage ratings without having to transfer these loads to the emergency diesel generator. These calculations also determined the minimum bus recovery voltage after a transient that would reset the undervoltage relay, preventing unnecessary transfers to the emergency diesel generators.
. The results of these calculations showed that a sustained degraded voltage trip setpoint of 294.6% and an allowable value of 294% will ensure that the vital bus electrical loads operate at or above their minimum operating voltage based upon the completed switchyard modifications.
9501050387 941214 PDR ADDCK 05000272 P
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i In Licensee Event Report (LER) 93-014-00 dated August 20, 1993, PSE&G notified the NRC that a review of engineering calculation ES-15008(Q), " Salem Unit 1 and 2 Degraded Grid Study," showed that the present TS sustained degraded voltage trip setpoint of 91.6% may not fully protect loads served by the 4160-V vital buses should the bus voltage degrade to less than 93.2% but greater than 91.6%. As part of the LER, PSE&G committed to implement a design change to revise the sustained degraded voltage trip setpoint to no less than 93.2% in order to provide a greater margin of reliability and to enhance the level of performance of these loads. Therefore, the proposed setpoint changes address the LER commitment.
3.0 EVALUATION PSE&G proposes to revise TS 3/4.3.2, Table 3.3-4, Item 7b, sustained degraded voltage setpoints for SGS Units 1 and 2.
It proposes to change the trip setpoints from 291.6% of bus voltage for s13 seconds to 294.6% of bus voltage for s13 seconds, and the allowable value for sustained degraded voltage from 291% of bus voltage for $15 seconds to 294% of bus voltage for sl5 seconds.
Two levels of undervoltage protection are provided for the loads served by the 4160-V vital buses at SGS. At first level, one undervoltage relay per 4160-V vital bus is used to sense the loss of offsite power.
The second level of undervoltage protection system (SLUPS) is provided to comply with the requirement of an NRC letter dated June 2, 1977, and Branch Technical Position (BTP) PSB-1 (NUREG-0800). The SLUPS ensures that minimum voltage is maintained at the vital buses.
The bus will be isolated from its offsite power source by tripping (2-out-of-3 logic) the infeed breaker and will automatically be aligned to the associated emergency diesel generator, if for any reason the bus voltage decays below the specified setpoint for more than the prescribed time.
As mentioned previously, PSE&G performed calculation to determine the optimum setpoint for the trip function on the basis of the response to various transients including a loss of coolant accident, degraded grid voltage, transformer failure and startup of the largest electrical load in accordance with the existing design basis. The setpoint also was determined on the basis of the requirement that all vital loads operate satisfactorily at or above the setpoint and following a transient, and that the bus voltage recover above the reset value of SLUPS so that unnecessary loading of the diesel generators is prevented.
The staff has reviewed the PSE&G calculations to determine if at the proposed trip setpoint and allowable value of the undervoltage relay settings provide adequate voltage at the terminals of all engineered safety features (ESF) equipment. The staff concludes that the proposed sustained degraded voltage relay trip setpoint change from 291.6% of bus voltage for $13 seconds, to 294.6% of bus voltage for sl3 seconds, and the allowable value for sustained degraded voltage relay from 191% of bus voltage for sl5 seconds to 294% of bus voltage for $15 seconds will ensure that vital bus loads operate at or above 1
their minimum operating voltage and that the proposed scheme conforms to the BTP PSB-1.
These changes are, therefore, acceptable.
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In a conference call with the NRC staff, PSE&G clarified the following points:
(1) In response to the question as to why there is no time delay for trip setpoints and allowable value for a loss-of-voltage condition, PSE&G stated there is no specific requirement for time delay as part of the design basis for the first level of undervoltage protection. However, to allow electrical systems to recover from voltage perturbations, the relays (GE IAV) used for the first level of undervoltage protection have inverse time characteristics that will actuate the relay within a period of time in accordance with the time-voltage curve of the relay, as the voltage drops below 70 percent.
(2) The PSE&G calculations for the degraded voltage value have been analyzed down to the 120-V level in documents ES-15.005 (Unit 1) and ES-15.006 (Unit 2). These supporting documents were submitted to the NRC as attachments to the supplemental information.
(3) In response to the question as to what type of field verification was done to validate the data for the degraded voltage calculation, PSE&G stated,
that the data used to perform the calculation was taken from the Salem Load Management System (LMS) database. This database was developed using transformer specification and nameplate data, cable impedance data, and motor data.
These data are used in conjunction with load flow software to perform various types of load flow and short circuit calculations.
(4) To control future modifications to the bus load, PSE&G follows procedure NC.NA-AP.ZZ-0008(Q), " Control of Design and Configuration Change, Tests and Experiments," and several lower-level eagineering procedures that control the design change package process.
Should a design change be
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initiated that might affect the electrical distribution system, a j
checklist is required to be completed that will identify the need to update the LMS database.
The LMS database represents a model of the electrical distribution system at Salem, Unit I and 2 from the 500-kV to the 120-V level. The need to revise the degraded grid study calculation is assessed on the basis of identified changes to the LMS database.
(5) The guidance of the NRC letter of June 2, 1977, and BTP PSB-1 forms the basis of undervoltage protection at Salem, Unit I and 2.
The proposed changes in trip setpoint and allowable value are still in compliance with both the letter and BTP PSB-1.
Conclusion The proposed amendment will increase the minimum voltage available at the vital buses and maintain vital loads within their voltage ratings. This ensures that the minimum voltage for any load will continue to be available including during sustained degraded voltage conditions.
Therefore, the proposed changes of the sustained degraded voltage relay trip setpoint from 291.6% of bus voltage for sl3 seconds to 194.6% of bus voltage for $13 seconds, and the allowable value from 291% of bus voltage for $15 seconds to 194% of bus voltage for sl5 seconds, will not significantly increase the probability or consequences of an accident previously evaluated. The staff finds the changes acceptable.
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4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the New Jersey State official was notified of the proposed issuance of the amendments. The State official had no comments.
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5.0 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 exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, 41d there has been no public comment on such finding (59 FR 29633). Accordingly, the amendments t
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 amendments.
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6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, j
that:
(1) there is reasonable assurance that the health and safety of the j
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 i
defense and security or to the health and safety of the public.
Principal Contributor:
S.K. Mitra Date: December 14, 1994 i
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