ML20217D981
| ML20217D981 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 10/12/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217D980 | List: |
| References | |
| NUDOCS 9910180218 | |
| Download: ML20217D981 (4) | |
Text
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p UNITED STATES j
NUCLEAR RE12ULATORY COMMISSION 2
WASHINGTON, D.C. 20066 4001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.128 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482
1.0 INTRODUCTION
By application dated July 8.,1999, Wolf Creek Nuclear Operating Corporation (the licensee) requested changes to the Technical Specifications for the Wolf Creek Generating Statior, (WCGS). The proposed hanges would increase the allowable values for engineered safety features actuation systr 2SFAS) loss-of-power 4 kV undervoltage trips in Table 3.3-4 (functional units 8.a ant o) of the current Technical Specifications (TSs) and in surveillance requirement (SR) 3.3.5.3 of the improved TSs. The word " nominal" is also being added to describe the trip setpoint in SR 3.3.5.3 and in the Bases of the improved TSs. The improved TSs were issued in Amendment 123 dated March 31,1999, but have not yet been implemented.
The application was supplemented by letter dated September 2,1999. This letter provided additional clarifying information, did not expand the scope of the application as originally noticed, and did not change the initial no significant hazards consideration determination published in the Federal Reaister on August 11,1999 (64 FR 43782).
2.0 BACKGROUND
The emergency diesel generators (EDGs) provide emerpocy power to the site when offsite power is unavailable or sufficiently degraded to allow stable safe power operation. One of the engineered safety features actuation systems provides undervoltage and degraded voltage protection for the engineered safety feature 4.16 kV Class 1E (NB) system bus (the 4.16 'kV bus). When actuated, the undervoltage and degraded voltage protection circuits will do the following:
a.
Trip the 4.16 kV preferred normal and altemate bus feeder breakers to remove the deficient power source to protect the Class 1E equipment from damage; b.
Shed all loads from the bus except the Class 1E 480 Vac load centers and centrifugal charging pumps to prepare the buses for re-energization by the load shedder and emergency load sequencer (LSELS); and c.
Generate a EDG start signal.
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., - These protection circuits are described in Section 8.3.1.1.3 of the Updated Safety Analysis Report (USAR) for WCGS. Each circuit has more then one channel for redundancy in having the trip function.'
The TSs list allowable values and trip setpoints for the loss-of-voltage and degraded voltage ESFAS protection circuits of the EDG start instrumentation. The licensee has proposed to increase the allowable values and to add the term " nominal" to the trip setpoint for these protection circuits.
Conformance to the TSs requires periodic surveillance tests of the trip setpoints of each
. channel of these protection circuits. The requirement for this surveillance, the type of surveillance test, and the frequency of the periodic tests are not being changed by the proposed amendment, if the as-found trip setpoint is within the allowable value and the calibration tolerance band, the circuit channel is considered operable and no further action is required. If the as-found trip is within the allowable value but outside the calibration band, the circuit channelis operable but the trip is recalibrated to the TS value. If the as-found trip setpoint is less than the allowable value, the circuit channel is inoperable and the action statement for limiting condition for operation in the TSs for the trip setpoint is entered and the appropriate actions must be taken.
2.0 EVALUATION Increase Allowable Values in its submittal, the licensee stated that during a review of the load flow and voltage drop calculation E-B-8 that applies to the EDG it was discovered that a revision to the calculation had resulted in a revised worst case 4.16 kV bus voltages during steady state lose-of-coolant accident (LOCA) conditions in the WCGS USAR accident analyses. A calculation was performed by the licensee to establish the correct allowable values and trip setpoints for the loss of voltage and degraded voltage protection circuits for the EDG.
The licensee stated that the allowable value for the loss of voltage protection circuit was calculated taking into account instrument inaccuracies using the square root of the sum of the squares methodology. An allowable value of 82.5 volts was the result of the calculation. The 1
trip'setpoint remained the value in the TSs. The licensee stated that the instrument inaccuracies accounted for include potential transformer inaccuracies and relay error.
The degraded grid voltage trip setpoint is selected to ensure that no end use loads are adversely affected from sustained operation of the EDG at a voltage below the setpoint. The trip setpoint remains the value in the TSs, but the allowable value was recalculated to be 2105.9 volts. The licensee stated that the instrument inaccuracies accounted for include bistable setting accuracy, bistable drift, and potential transformer inaccuracies.
. The revised allowable values for the loss of voltage and degraded voltage protection circuits are based on calculations for the worst case 4.16 kV bus voltage which are during steady state LOCA conditions for WCGS. Because these allowable values will ensure that the engineered safety feature 4.16 kV bus is available and stable during all plant conditions including the design basis accidents, the licensee-proposed changes to the allowable values to the current
. - TSs and the improved TSs are acceptable. The proposed changes are being made to both the current TSs and improved TSs because the improved TSs havo not yet been implemented at WCGS.
Add the Word Nominal to the Imoroved TSs The licensee has proposed to add the word " nominal" to the phrase " trip setpoint" in SR 3.3.5.3 of only tile improved TSs.. The proposal would, therefore, have the trip setpoint requirement in
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the SR be on the " nominal" trip setpoint. The use of nominal trip setpoint in the TSs is related to (1) the setting of the actual trip setpoint based on plant conditions and (2) the surveillance of the actual trippoint as to whether the instrumentation channel is operable. For the use of nominal trip setpoint, the actual trip setpoint is set more conservative than the t.ominal trip setpoint that is specified in the TSs. The nominal trip setpoint in the TSs is listed without the inequality that would be given in the TS when only the trip setpoint is used. In proposing the nominal trip setpoint for the improved TSs, the licensee has deleted the inequality associated with values of the trip setpoints in SR 3.3.5.3.
The second part of the use of the nominal trip setpoint is that the operability of the instrumentation channel for the trip setpoint is determined by the relationship of the measured "as-found" trip setpoint to (1) the calibration tolerance band for the channel, and (2) the
. allowable value for the trip setpoint. If the "as-found" trip setpoint is within the calibration tolerance band then the instrumentation channel is operable and the trip setpoint is left "as-found." If the "as-found" trip setpoint is outside the calibration tolerance band, but within the allowable value, the instrumenation channel is still operable, but the channel is re-adjusted to have the trip setpoint within the calibration tolerance band. If the "as-found" trip setpoint is outside the allowable value, the instrumentation channel is declared inoperable and the appropriate actions for the limiting condition for operation are entered.
In using the nomhal trip setpoint methodology in the TSs, the licensee must have a discussion on the use of nominal trip setpoints and the instrumentation channel operability in the Bases of the TSs for SR 3.3.5.3. The licensee submitted such a discussion in its letter of September 2, 1999. This discussion is consistent with the previous paragraph above. Any changes in the future to this discussion are controlled by the Bases Control Program in Section 5.5.14 of the improved TSs.
Therefore, based on the discussion above, the licensee's proposed use of the nominal trip setpoint in SR 3.3.5.3 is acceptable.
3.0 STATE CONSULTATION
in accordance.with the Commission's regulations, the Kansas State Official was notified of the proposed issuance of the amendment. The State official had no comments.
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Eff/lRONMENTAL CONSIDERATION The amendment changes surveillance requirements. The NRC staff has determined that the amendment invobes no significant increase in the amounts, and no significant charige 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 amendment involves no significant hazarris consideration, and there has been no public comment on such finding (64 FR 43782). Accordingly, the 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 stateme:nt or environmental assessment need be prepared in connection with the issuance of the amendment.
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: J. Donohew Date: October 12, 1999