ML20134L782
| ML20134L782 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 02/10/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20134L780 | List: |
| References | |
| NUDOCS 9702190281 | |
| Download: ML20134L782 (7) | |
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1 UNITED STATES e
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NUCLEAR REGULATORY COMMISSION "s...../
2 WASHINGTON, D.C. 20066-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT N0.104 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482
1.0 INTRODUCTION
By letter dated December 13, 1995, as supplemented by letter dated October 10, 1996, Wolf Creek Nuclear Operating Corporation (the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License No. NPF-42) for the Wolf Creek Generating Station. The proposed changes would revise the 125-volt D.C. Sources Technical Specifications l
3.8.2.1 and 3.8.2.2 and the Onsite Power Distribution Technical Specifications 3.8.3.1 and 3.8.3.2.
The 125-volt D.C. Sources Technical Specifications 3.8.2.1 and 3.8.2.2 would be revised to include provisions for installed spare chargers which will be added to the plant design before startup from the ninth refueling outage.
The Onsite Power Distribution Technical Specifications 3.8.3.1 and 3.8.3.2 would be revised to indicate that spare charger NK25 may be connected in place of charger NK21 or NK23 and spare charger NK26 may be connected in place of l
charger NK22 or NK24.
The October 10, 1996, supplemental letter forwarded additional information concerning compliance with IEEE-308-1974, "IEEE Standard Criteria for Class IE Power Systems for Nuclear Power Generating Stations" (IEEE-308) and dio not change the staff's original no.;ignificant hazards determination published in the Federal Reaister on January 22, 1996 (61 FR 1639).
2.0 BACKGROUND
The current power block DC power system consists of four independent Class 1E 125-volt DC subsystems, four non-Class IE 125-volt DC subsystems, and one non-Class IE 250-volt 2 system. The Class IE DC system provides DC electric power to the Class IE DC loads and for control and switching of the Class IE systems. Each Class 1E DC power subsystem consists of one 125-volt battery, one battery charger, one inverter, and distribution switchbaards.
For Load Group 1, the battery charCars for DC subsystems 1 and 3 are supplied 480-volt AC power from Class IE busses NG01 and NG03, respectively.
Similarly, for l
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Load Group 2, the battery chargers for DC subsystems 2 and 4 are supplied
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480-volt AC power from Class IE busses NG02 and NG04, respectively.
Physical
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separation, electrical isolation, and redundancy of the two load groups are l
provided to comply with the requirements of IEEE Standard 308.
l Currently, one spare battery charger and one spare inverter are provided for the power block. These items are physically located central to all of the Class IE DC systems. They are not, however, electrically connected.
In the i
event of the failure of a charger or inverter, the spare is manually connected j
to the affected system. Therefore, the malfunctioning equipment may be repaired without imposing long-term disruption of the system. However, the connection of the spare batter ll charger cannot be completed within the 2-hour allowed outage time.
In the proposed modification, the current spare battery charger will be permanently installed as a spare battery charger for the 125-volt DC busses NK01 and NK03 and powered from either Class IE bus NG01 or non-Class IE bus PGl9. A new battery charger will be installed as a spare battery charger for 125-volt DC busses NK02 and NK04 and powered from either Class IE bus NG04 or non-Class IE bus PG20. Each Class IE DC power subsystem will then consist of one 125-volt battery, one primary battery charger, one inverter, distribution switchboards, a sharei spare batte y charger, and spare battery charger transfer switches.
Ir. the event c a failure of a primary battery charger, the respective spare battery charger can be quickly aligned to provide power to the affected DC power subsystem. Therefore, the malfunctioning equipment may be repaired witb a t imposing long-term disruption of the system. Once the spare battery charger is aligned to a given DC power subsystem all of the required annunciated trouble conditions are monitored on the spare battery charger and an annunciator window on the main control boards.is lit to alert the control ream staff that a spare battery charger is in use.
The batteries, racks, chargers, inverters, and auxiliary distribution equipment (switchboards and transfer switches) are designated seismic Category 1, and are designed to maintain their functional capability during and after an SSE. This modification will be made under the provisions of 10 CFR 50.59.
The modification will allow 125-volt DC power to be supplied from the installed spare chargers within the Technical Specification 3.8.2.1 and 3.8.2.2 allowed outage time of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
3.0 EVALUATION The technical specifications would be revised as follows:
Technical Specification 3/4.8.2.1 - D.C. Sources - Operating Parts a and b of the Limiting Condition for Operation would be modified to read as follows:
"a.
125 Volt Batteries NK11 and NK13 and associated Full Capacity Chargers NK21, NK23, or installed spare NK25 (powered from NG01), and i
! b.
125 Volt Batteries NK12 and NK14 and associated Full Capacity Chargers NK22, NK24, or installed spare NK26 (powered from NG04)."
Surveillance Requirement 4.8.2.1 would be modified to require that surveillances be performed only on the battery chargers that are connected to the DC busses.
Technical Specification 3/4.8.2.2 - D.C. Sources - Shutdown Parts a and b of the Limiting Condition for Operation would be modified to read as follows:
i "a.
125 Volt Batteries NKil and NK13 and associated Full Capacity Chargers l
NK21, NK23, or installed spare NK25 (powered from NG01), or b.
125 Volt Batteries NK12 and NK 14 and associated Full Capacity Chargers NK22, NK24, or installed spare NK26 (powered from NG04)."
l Surveillance Requirement 4.8.2.2 would be modified to require that sureveillances be performed only on the battery chargers that are connected to i
the DC busses.
j Technical Specification 3/4.8.3.1 - Onsite Power Distribution -
Operating j
Parts g, h, i, and j of the Limiting Condition for Operation would be modified to read as follows:
l "g.
125-Volt D.C. Bus #NK01 energized from Battery #NKil and Charger #NK21 (or #NK 25 powered from NG01),
1 h.
125-Volt D.C. Bus #NK02 cnergized from Battery #NK12 and Charger #NK22 (or #NK 26 powered from NG04),
1.
125-Volt D.C. Bus #NK03 energized from Battery #NK13 and Charger #NK23 (or #NK 25 powered from NG01), and J.
125-Volt D.C. Bus #NK04 energized from Battery #NK14 and Charger #NK24 (or #NK 26 powered from NG04)."
Technical Specification 3/4.3.8.3.2 - Onsite Power Distribution -
Shutdown Parts a.4) and b.4) of the Limiting Condition for Operation would be modified to read as follows:
"a.4) 125-Volt D.C. Busses #NK01 and NK03 energized from batteries #NK 11 and NK 13 and Chargers #NK21 and NKt3 (Spare Charger #NK25 powered from NG01 may be connected in place of #NK21 or #NK23), or
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l b.4) 125-Volt D.C. Busses #NK02 and NK04 energized from batteries #NK 12 and i
NK 14 and Chargers #NK22 and #NK24 (Spare Charger #NK26 powered from i
NG04 may be connected in place of #NK22 or #NK24)."
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In the event of a failure of the primary battery charger, the installation of i
the spare battery charger will allow 125-volt DC power to be supplied from the installed spare battery charger within the allowed outage time of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
l The spare battery chargers will be located in switchgear rooms 3301 (NK25) and 3302 (NK26). These rooms are
.:te from the rooms that house the primary battery chargers. Conduits and cabling will be installed in accordance with
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the separation criteria as defined in IEEE 384-1974. The staff finds this acceptable.
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The spare chargers will be installed such that each one can only supply one DC bus at a time from their respective safety-related bus, NG01 for charger NK25 i
and NG04 for charger NK26. Alternate AC nonsafaty-related electrical feeds to l
spare battery chargers NK25 and NK26 will be provided for maintenance purposes only during safety-related AC train outages. The AC transfer switch in each j
redundant load group allows the spare battery charger to be powered from i
either a class IE AC source or a non-class IE AC source.
j The following design features and administrative controls will prevent the j
spare battery chargers from being powered from a non-Class IE AC circuit for the performance of safety related functions. There are three control switches 4
i located on the panel face of the AC transfer switch. One is a hand switch I
which operates the Class IE AC circuit breaker to connect the transfer switch i
to the Class IE AC bus. The second is a keylock switch which operates the i
non-Class IE circuit breaker to connect the transfer switch to the non-Class l
1E AC bus. The third is a hand switch which connects the spare battery charger to either the Class IE or non-Class IE bus at the transfer switch.
In order to prevent Class IE to non-Class IE separation conflicts, only one power source can be energized at a time. The breaker close circuits are interlocked through isolation relays, located in each AC transfer switch, so that the open breaker cannot be closed unless the other breaker is open.
Each keylock switch has a unique key code to prevent the key for one load group from inadvertently being used to operate the non-Class IE breaker for the second load group. The keys for the keylock switches will be administrative 1y controlled by the control room to ensure that the non-Class IE breaker is closed only during load group outages (see Figure 1). The staff finds the design and controls for prevention of the use of non-Class IE power for IE functions acceptable.
Additional switches will be installed in the output of the primary battery chargers. These switches will prevent the connection of two battery chargers (the primary and the spare) to the same DC bus (see Figure 1). The staff finds this acceptable.
The spare battery chargers are equivalent to those in the present design.
Yhey are seismic Category I and meet separation criteria by use of appropriate isolation devices. The control building heat load and air conditioning cticulations have been revised to reflect the new spare battery charger and j
. l transfer switch installation. The air conditioning cystem capacity is capable of cooling the~ additional heat loads.
The staff finds'this acceptable.
Normally, the primary battery chargers are supplied from two different 480-volt AC busses. However, if battery. charger NK23 (Load Group 1) or NK24 (Load Group 2) failed and the spare battery charger was placed in service, both operational battery chargers in the affected Load Group would be powered from the same 480-volt AC bus (NG01 for Load Group 1 and NG04 for Load Group 2).
The licensee has evaluated this condition and determined that the additional load imposed on busses NG01 and NG04 with both battery chargers connected is l
within the capacity of the busses. The staff finds this acceptable.
l The surveillance requirements associated with the battery chargers are being changed.to require only those chargers actually supplying power to the DC busses to be surveilled. However, the licensee will maintain the spare chargers energized and available for immediate alignment to the DC bus in the event the primary battery charger fails. The staff finds this acceptable l
because if the spare charger is incapable of supplying the DC bus when called on, the action statement would require a plant shutdown within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> of the l
original failure. During the action statement time, the batteries would be j
supplying the required DC loads. The 18-month surveillance requirements will i
be performed on all the battery chargers, including the spare battery chargers. The staff finds this acceptable.
The original design of the DC power system was in accordance with IEEE-308.
l This modification will maintain compliance with IEEE-308. The installation of the third battery charger in the two redundant DC power systems does not compromise the separation requirements.
Load Group 1 and Load Group 2 will continue to be completely separated from each other. The staff finds this acceptable.
4.0 STATE CONSULTiJ D M 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.
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.
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 proposed finding that the amendment involves no significant hazards consideration, and there has been no 4
public comment on such finding (61 FR 1639). Accordingly, the amendment meets i
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0 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.
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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 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.
Attachment:
Figure I Principal Contributor: James Stone Date:
February 10, 1997 I
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