ML20202B458
| ML20202B458 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 01/26/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20202B454 | List: |
| References | |
| NUDOCS 9901290086 | |
| Download: ML20202B458 (3) | |
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UNITED STATES aj j
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 3050641001 i
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5 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
j RELATED TO AMENDMENT NO. 200 TO J
FACILITY OPERATING LICENSE NO. NPF-6 ENTERGY OPERATIONS. INC.
ARKANSAS NUCLEAR ONE. UNIT NO.2 l
DOCKET NO. 50-368
1.0 INTRODUCTION
l By letter dated June 29,1998, Entergy Operations, Inc. (the licensee) submitted a request for l
changes to the Arkansas Nuclear One, Unit No. 2 (ANO-2) Technical Specifications (TS). The l
requested changes would provide a range of acceptable values for the 4 kV bus loss of voltage relays. The present TS Table 3.3-4," Engineered Sefety Feature Actuation System Instrumentation," provides a single value for both the trip and allowable values for the 4 kV bus l
loss of voltage requirements. This change would provide a tolerance band for allowable values for the loss of voltage relay setting and allow for the control of the actual trip value in the licensee's surveillance test procedures, in addition, minor adjustments would be made to the l
trip time delay.
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2.0 BACKGROUND
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There are two redundant and independent 4160 V safety buses and each safety bus has two levels of undervoltage protection: (a) loss of voltage, and (b) degraded voltage. The loss of voltage protection is provided by two inverse time undervoltage relays on each of the 4160 V i
safety buses. The loss of voltage relays set at 3120 V (approximately 78% of motor rated l
voltage) initiates load shedding and the starting of the associated diesel generator within i
approximately one second of a totalloss of voltage at the safety bus. The isolation of the safety buses will be delayed approximately two seconds (for a total of approximately three seconds) to i
permit the offsite power to supply the safety related loads in the event of a failure of the fast l
transfer to an alternate source. The second level of undervoltage protection is provided by two undervoltage relays on each 480 V safety bus for degraded voltage conditions. This second level of undervoltage protection is not affected by this change.
i TS Table 3.3-4, item 7.a, "4.16 kV Emergency Bus Undervoltage (Loss of Voltage)," specifies a trip value of 3120 V and allowable value of 3120 V. The table entry has a Note (4) which reads:
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" inverse time relay set value, not a trip value. The zero voltage trip will occur in 0.75*0.075 seconds." By letter dated June 29,1998, Entergy Operations Inc requested approval of the 1
proposed TS change to provide a range of acceptable values for the 4 kV bus loss of voltage condition instead of a single trip and allowable value for the loss of voltage relays, i
9901290086 990126 PDR ADOCK 05000368 P
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3.0 EVALUATION l
Currently, the tr6 setpoint for the loss of voltage relays on each 4160 V safety bus is set at a l
single value of 3120 V (approximately 78% of the motor base voltage of 4000 V). Entergy l
Operations, Inc. determined through operating experience that such single values (for the trip l
setpoint as well as for allowable value) do not take into acccunt applicable margins, channel i
uncertainties and calibration tolerances. Therefore, the licensee has proposed to remove the l
specific value in TS 3/4.3.2, item 7.a. under the trip value column and replace it by Note (4).
The proposed Note (4) reads,"The trip value for this function is listed in the surveillance test procedures. The trip value will ensure that adequate protection is provided when all the applicable calibration tolerances, channel uncertainties, and time delays are taken into account." The licensee has proposed to revise allowable values for the loss of voltage relays in this table from 3120 volts to 2300 t 699 volts. The proposed setting provides a range of values based on a maximum setting which is below the lowest allowed motor voltage of 75% of motor l
voltage rating. The licensee also discovered that the present setting provides marginal protection from unnecessary actuations during certain limited potential system transient events.
To prevent these transients, the licensee has proposed to reduce the allowable setpoint voltage value from 3120 V to 2999 V (2300 V + 699 V). The staff has determined that allowable values as low as 1601 V (2300 V - 699 V) will still provide the necessary safety function for the loss of 4
voltage protection. Additionally, the licensee has proposed to revise the allowable values for the time delay from "0.75
- 0.075" second to "0.64 0.34" second. This lower nominal setting and expanded relay time delay setting tolerance band do not affect the safety function since there is no appreciable time difference during a loss of voltage event. The maximum proposed time delay setting is within those used in the ANO-2 safety analysis. The minimum proposed time delay setting provides adequate time to allow the fast transfer of the associated bus to an alternate power source.
The use of a range of allowable values instead of a single fixed trip value for the loss of voitage relays and the change of allowable values for the time delay is equivalent to what is specified in Revision 1 of NUREG-1432," Standard Technical Specifications for Combustion Engineering Plants."
Based on the above, the staff concludes that the proposed change for the addition of a range of allowable values (2300 m 699 volts) instead of a fixed trip setpoint (set at 3120 volts) for the loss of voltage relays, and the change "0.64 0.34" seconds instead of "0.75
- 0.075" seconds provides protection from unnecessary actuations during certain system trainsients while still ensuring the necessary safety function for the loss of voltage protection. Therefore, the staff concludes that the proposed change is acceptable.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Arkansas State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes
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i surveillance requirements. The Nuclear Regulatory Commission staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the i'
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 amendment involves no significant hazards consideration, and there has been no public comment on such finding (63 FR 56244). Accordingly, the l
amendment meets 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.
6.0 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
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_ 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 l
common defense and security or to the health and safety of the public.
Principal Contributor: N. K. Trehan l
Date: January 26, 1999 l
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