U-603146, Application for Amend to License NPF-62,changing TS Table 3.3.8.1-1 to Revise Allowable Values for Degraded Voltage Relay Reset & Dropout Setpoints as Specified Per Items 1.c, 1.d,2.c & 2.d of Table

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Application for Amend to License NPF-62,changing TS Table 3.3.8.1-1 to Revise Allowable Values for Degraded Voltage Relay Reset & Dropout Setpoints as Specified Per Items 1.c, 1.d,2.c & 2.d of Table
ML20199H260
Person / Time
Site: Clinton Constellation icon.png
Issue date: 01/20/1999
From: Mcelwain J
ILLINOIS POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20199H264 List:
References
U-603146, NUDOCS 9901250154
Download: ML20199H260 (17)
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Text

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liknois Power Company P O. Box 678 Chnton,IL 61727 Tel 217 935-88B1 x3000'  !

Fax 217 935-4632 l

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John P. McElwain Chief Nuclear Officer P(MNER ==  !

8E.100s i An lihnova Company J January 20, 1999  ;

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Docket No. 50-461 10CFR50.90 l

Document Control Desk Nuclear Regulatory Commission Washington, D.C. 20555 l

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Subject:

Clinton Power Station Proposed Amendment of j Facility Operatina License No. NPF-62 (L,S-98-012) j l

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Dear Madam or Sir:

Pursuant to 10CFR50.90, Illinois Power (IP) hereby applies for amendment of Facility Operating License No. NPF-62, Appendix A - Technical Specifications, for Clinton Power Station (CPS). This request consists of proposed changes to Technical Specification 3.3.8.1, " Loss of Power Instrumentation," and to various Suiveillance Requirements (SRs) under Technical Specification 3.8.1, "AC Sources-Operating."

Specifically, IP proposes to change Technical Speci6 cation Table 3.3.8.1-1 to revise the Allowable Value(s) for the degraded voltage relay reset and dropout setpoints as specified per items 1.c, l.d,2.c, and 2.d of the table. In addition, SR 3.8.1.2, SR , 3.8.1.7, SR 3.8.1.11, SR 3.8.1.12, SR 3.8.1.15, SR 3.8.1.19, and SR 3.8.1.20 are being  !

changed to reflect a new/ revised value for the minimum steady-state bus voltage )

identified in these SRs. l l

The proposed changes are prompted by recent developments in IP's I implementa? ion of plant modifications to resolve degraded voltage concerns for CPS, the subject of which has been addressed in meetings and previous correspondence with the NRC, and in several CPS Operating License amendments. Modifications completed )

or nearly completed include installation of new, more accurate degraded voltage relays,  ;

installation of a load tap changing transfonner to replace the existing emergency reserve auxiliary transformer (ERAT), and the addition of static VAR compensators (SVCs) on the ERAT and reserve auxihary transformer (RAT). These modifications were supported or authorized by License Amendments 110,116 and 117 respectively.

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U-603146 Page 2 In addition to the above modifications, and as previously described to the NRC, a number of 480/120-volt regulating transformers are being installed (under 10CFR50.59) within the auxiliary power system at CPS during the current outage. A reassessment was performed to identify the number of transformers required to be installed during the current outage since it was determined that there are alternative solutions to ensure adequate voltage for some of the affected 120-volt circuits. As a result, it has been determined that adequate voltage for the affected circuits can be achieved (without the use of regulating transformers) by raising the minimum required bus voltage. The degraded voltage relay (DVR) setpoints will be adjusted to support the new higher voltage requirements. (Final verification of the DVR Technical Specification Allowable Values will be provided when all of the supporting calculations are complete.) A boost to the RAT secondary voltage through a change in the position of the RAT tap setting will maintain the capability of the offsite source (s) to reset the degraded voltage relays when offsite voltage is greater than or equal to the minimum expected level. Revising the DVR setpoints requires appropriate changes to be made to the CPS Technical Specifications, as requested herein.

Additional information and documents to support this application are provided as attachments to this letter. An affidavit supporting the facts set forth in this letter and its attachments is provided as Attachment 1. A description of the proposed changes and associated justification (including a Basis for No significant hazards Consideration) are provided in Attachment 2. A marked-up copy of the affected pages from the current TS is provided in Attachment 3. A marked-up copy of the affected pages from the current TS Bases is provided in Attachment 4. (The Bases pages are for information only. Following NRC approval of this request, IP will revise the CPS TS Bases, in accordance with the TS Bases Control Program of TS 5.5.11, "TS Bases Control Program," to incorporate the changes in Attachment 4.)

IP has reviewed the proposed changes against the criteria of 10CFR51.22 for categorical exclusion from environmental impact considerations. The proposed changes do not involve a significant hazards consideration, or significantly increase individual or cumulative occupational radiation exposures. Based on the foregoing, IP concludes that the proposed changes meet the criteria given in 10CFR51.22(c)(9) for a categorical exclusion from the requirements for an Environmental Impact Statement.

Please note that completion of the degraded voltage project modifications at CPS is the critical path in completing the current outage. Therefore, IP respectfully requests an expedited NRC review and approval of the requested Technical Specifications change prior to restart of the unit which is currently scheduled for mid-March 1999.

Sincerely yours,

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af'M John P. McElwain Chief Nuclear OfIicer

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U403146 Page 3 r

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At*-hments  :

i cc: NRC Clinton Licensing Project Manager NRC Resident Office, V-690  :

NRC Regional Administrator, Region III I Illinois Department ofNuclear Safety t

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Aach=*=t 1 to U-603146 Page 1 of1 John P. McElwala, being first duly sworn, deposes and says: That he is ChiefNuclear OfBcer for Clinton Power Station; that this application for amendment ofFacility Operating License NPF-62 has been prepared under his supervision and direction; that he knows the contents thereof, and that to the best of his knowledge and belief said letter and the facts contained therein are true and correct.

Date: This 20 day ofJanuary 1999.

Signed: bbf3-L .

' John P.'Me'Elwain

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STATE OFILLINOIS l SS. <= - 1r--=

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Jacqueline S. Matthias Notary Putdic, State of IEnois ll l My Commissies Epirse 1144/mi ll

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Subscribed and sworn to before me this .20 # day ofJanuary 1999.

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1 Attachment 2 to U-603146

- LS-98 012 Page 1 of13 &

Backaround Desian Basis l Successful operation of equipment important to safety is dependent upon the availability l of adequate power sources for energizing essential components such as pump motors, motor-operated valves, and the associated control components. An onsite electric power l system and an ossite electric power system are provided for time unit for this purpose, pursuant to General Design Criterion (GDC) 17 of 10CFR50 Appendix A (see Figure 1,

! page 2 of this attachment). Either of these systems for CPS are capable of providing required power to the three divisional, Class IE (safety-related) 4.16 kV plant emergency buses.

l Offsite power is the preferred and normal source for the 4.16 kV emergency buses. The l

primary offsite source of power for the unit Class IE AC power system is via the reserve i auxiliary transformer (RAT) which is connected to a 345 kV offsite network with multiple incoming lines. The secondary offsite source of power for the unit Class IE AC power system is via the Emergency Reserve Auxiliary Transformer (ERAT) which is connected l to a separate, independent 138 kV offsite network. These circuits (the RAT and ERAT) provide the two qualified offsite circuits required by Technical Specification 3.8.1, "AC Sources-Operating," and 10 CFR 50 Appendix A GDC 17.

l The onsite standby power supply consists of diesel generators (DGs) one for each of the l

three divisional load groups (i.e., divisional buses) such that each bus has a dedicated DG.

The DGs start automatically in response to a loss of coolant accident (LOCA) or in response to a degraded or loss ofvoltage to the bus (es).

l The Loss of Power (LOP) instrumentation addressed by Technical Specification (TS) t 3.3.8.1, " Loss of Power Instrumentation," monitors the voltage of the 4.16 kV emergency buses. If the LOP instrumentation determines that insufficient voltage is available (for a period of time longer than a predetermined time delay), the buses are disconnected from the offsite power source (s) and connected to the respective onsite diesel generator (DG) power source. Each 4.16 kV emergency bus has its own independent LOP instrumentation and associated trip logic. The voltage for the Division 1,2, and 3 buses is monitored at two levels which are considered as two different undervoltage Functions:

loss of voltage and degraded voltage. This amendment request only affects the degraded voltage functions.

As discussed in the Bases for TS 3.3.8.1, the LOP instrumentation ensures that the emergency core cooling system (ECCS) and other required systems are supplied power at

! an acceptable voltage in the event of any of the accidents analyzed in the Updated Safety

{ Analysis Report (US AR), including a LOCA, in which a loss of offsite power is assumed.

! The initiation of the DGs on loss of offsite power, and subsequent initiation of the ECCS,

! ensure that the fuel peak cladding temperature remains below the limits of 10CFR50.46.

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M e Figure 1 1 . . j Attachment 2 . to U-603146 . LS-98 012  ! Page 3 of13 ) } A degraded voltage condition on a 4.16 kV emergency bus indicates that while offsite l power may not be completely lost to the respective emergency bus, power may be l

insufficient for starting loads such as large motors without risking damage that could 2 disable the load. Therefore, power supply to the bus is transferred from offsite power to
onsite DG power when the voltage on the bus remains less than the degraded voltage  ;

Allowable Value for a period of time greater than or equal to the associated time delay

Allowable Value. This ensures that adequate power will be available to the required

j equipment in the event of a design basis accident (DBA) in conjunction with a degraded j grid voltage condition. l l Historical Backaround j , l In 1994, Illinois Power (IP) identified and reported, via Licensee Event Report (LER) i 94-005, that the setpoints for the degraded voltage relays at Clinton Power Station (CPS) 1 ! were not sufficient to ensure proper operation of all required equipment. This was identified as a result of calculation reviews performed in response to Electrical i Distribution System Functional Inspection (EDSFI) findings at other nuclear plants. As  ; j interim corrective action, IP installed an alarm for the 4.16 kV safety-related buses and established contingent operator actions to minimize the potential for the Class IE loads to

receive inadequate voltage. Longer-tenn actions were initiated to develop design change i i options for restoring the plant to its licensing basis for automatic degraded voltage j l protection. One action taken was to procure more accurate, state-of-the-art relays to l

. replace the existing degraded voltage relays. 4  ! j By letter dated February 22,1996, and to :,upport use of the new relays, IP proposed an 1 l amendment to the. CPS Technical Spedlications to revise the setpoints (Allowable Values) for the 4.16-kV degraded voltage relays. Extensive calculations were performed in j support of the amendment to as.ture that continuous-duty motors and motor-operated i valve motors hed adequate staning voltage. The revised setpoints (and other related l changes) were approved by th NRC in Amendment 110 to the CPS Operating License, 3 dated December 4,1996, and the new relays were subsequently installed during the l current, extended outage in early 1997. I Due to the reduced margins for ensuring adequate voltage to loads at CPS from the offsite j t-electric power system, and in recognition of a need to implement additional plant modifications to recover required margins, detailed studies of the IP electrical distribution system were completed later in 1997. These studies took into account current and projected peak system load conditions through the year 2007, the changing generation mix in Illinois forecasted to occur due to deregulation, and reconsideration of the single-contingency loss of a major line or generating station. The predicted voltage available to , the CPS 4.16 kV safety buses was shown to be less than required, on a long-term basis, assuming a loss of coolant accident (LOCA) and unit trip. It was therefore recognized me y -+ m- -> -- --- r -r- l l' Attachment 2 to U-603146 LS-98-012 Page 4 of 13 that additional modifications would be needed to ensure adequate voltage to plant loads from the offsite electric power system in the future. An extensive plan was thus developed to implement the following modifications for the auxiliary power system at CPS:

1) Installation of 480/120-volt regulating transformers (to replace selected non-regulating 480/120-volt transformers used in the CPS auxiliary power system).
2) Replacement of the emergency reserve auxiliary transformer (ERAT) with a load tap changer (LTC) transformer. (Longer-term, future plans include replacement of the RAT with an LTC transformer.)
3) Addition of static VAR compensators (SVCs) on the 4.16-kV side of the reserve auxiliary transformer (RAT) and ERAT.

All of the above modifications, which were discussed in meetings conducted with the NRC in early 1998, are being implemented during the current outage at CPS. IP requested license amendments to support installation of the ERAT LTC and the SVCs for the RAT and ERAT. These amendments were approved by the NRC on October I and 9,1998, respectively. With particular regard to installation of the regulating transformers, work in this area is ongoing during the current outage. As noted previously, the regulating transformers were identified as a means to resolve voltage concerns at the 120-volt level since a number of 120-volt circuits had been identified as the most limiting for establishing minimum voltage requirements to plant loads. All of the work in this area was intended to be performed under 10CFR50.59 with no license amendment required. The initial plan was to replace non-regulating transformers with nine (9) regulating transformers: four (4) in Division 1, four (4) in Division 2, and one (1) in Division 3. As detailed loading calculations were completed, however, it was determined that some of the regulating transformers were needed in combination with the non-regulating transformers in order to avoid overloading some of the regulating transformers. This approach involves rewiring eleven motor control centers supplied by the non-regulating transformers. In addition, several technical issues were identified during design completion for the regulating transformers and associated circuits, thus adding to the increased scope and complexity of the overall modification. Revised Approach to Installation of Regulating Transformers The above concerns and issues led to the development of a modified approach to installation of the regulating transformers and/or resolution of the 120-volt circuits. Under the modified approach, the number of regulating transformers to be installed during the current outage would be reduced. This is primarily made possible by boosting RAT Attaciunent 2 to U-603146 LS-98-012 Page 5 of13 secondary voltage through a change in the position of the RAT tap setting and taking s advantage of the regulating effect of the RAT SVC to accommodate the expected voltage range for the offsite source (s).' Based on a new, higher minimum required bus voltage, the repositioned tap setting for the RAT would support safe plant operation while precluding the need to install regulating transformers for most 120-volt circuits. The remaining circuits (approximately 27 circuits) would be modified as needed during the current outage. (In some cases, voltage concerns can be resolved by decreasing voltage drop to the circuit loads through the installation of new or additional cable, or the rerouting of cable to the affected loads, in lieu ofinstalling a regulating trs.nsformer. For others a regulating transformer is required and will thus be installed.) The boosted 4.16 kV voltage supports the new minimum required bus voltage due to the limi:ing circuits / loads. At the same time, the SVC(s) in conjunction with the boost to RAT secondary voltage permits the offsite source (s) to support the new required bus voltage over the expected voltage range for the otTsite source (s). Under the current plan, the number of regulating transformers anticipated to be installed during the current outage is reduced to two (2) for Division 1, one (1) for Division 2, and one (1) for Division 3. However, ongoing analyses may affect the actual number of regulating transformers required to be installed. Each tap setting for the RAT corresponds to a 2.5 percent change in secondary voltage. Moving the tap setting up two positions for the RAT will thus boost 4.16 kV secondary voltage by five percent, and supports the desired increase in the minimum bus voltage required for plant loads. The increased minimum bus voltage correspondingly requires the setpoints of the degraded voltage relays to be increased by a comparable amount. (That is, the relay must not trip at too low a value relative to the voltage needs of es:ential equipment. Also, the upper limit for relay reset point (pickup) must be raised to ensure that the relay does not separate the 4.16 kV emergency buses from the offsite power when the offsite source is capable of supplying the emergency bus loads). On this basis, the allowable values specified in the Technical Specifications for the degraded voltage relay setpoints are required to be changed. Further, because the minimum required bus voltage is being raised consistent with the new degraded voltage relay setpoints, the minimum bus voltage required to be attained during testing of the standby emergency diesel generators must also be increased. This necessitates revising the value specified for the minimum required bus voltage wherever it appears in the DG Surveillance Requirements. ' Maintaining adequate voltage at the 120-volt level is not a concern for the ERAT because a tap setting for the ERAT will be chosen such that the possibility of a high voltage condition (caused by an ERAT SVC trip) will not be created and therefore there will be no need to maintain a minimum load level on the ERAT to prevent an overvoltage condition on the safety buses. It will be slwwn by calculation that the l expected offsite voltages will remain well within the abilities of the ERAT SVC to maintain a proper control band. h - 0 Attachment 2 , to U-603146 LS-98-012 Page 6 of13 Description of Proposed Channes In accordance with 10CFR50.90, the following changes to the CPS TS are being proposed: (1) The Note associated with Required Action A.2 under Limiting Condition for Operation (LCO) 3.3.8.1 is being revised to eliminate reference to a previously completed plant modification. The text to be eliminated was inserted via License Amendment 110 in anticipation of the associated modification so as to make l associated Action A.2 effective upon release for operation of the modification. Action A.2 is now effective, and the conditional text is no longer needed. (2) The Allowable Value specified for the degraded voltage relay reset point (" Degraded Voltage Reset - 4.16 kV Basis") for Divisions 1 and 2 of the 4.16 kV emergency buses, identified as item 1.c, and for the Division 3,4.16 kV emergency bus, identified as item 2.c of Table 3.3.8.1-1, " Loss of Power Instmmentation," is proposed to be revised to 2 4090 V and 5 4111 V. (3) The Allowable Value specified for the degraded voltage relay dropout /setpoint (" Degraded Voltage Drop-out - 4.16 kV Basis") for Divisions 1 and 2 of the 4.16 kV emergency buses, identified as item 1.d, and for the Division 3,4.16 kV emergency bus, identified as item 2.d ofTable 3.3.8.1-1, is proposed to be revised to 2 4051 V and 5 4092 V. (4) Footnote (a) to Table 3.3.8.1-1 is proposed to be revised to maintain the currently specified reset point for the degraded voltage relay until the recent, associated modification is completed. The current text of this note was based on the aforementioned previous modification (s) made to the degraded voltage relays (addressed in Amendment 110). The first part of this note regarding release for operation (RFO) of the corresponding plant modification can be applied to, and is needed for, the current modification (in the same way that it was needed for the previous modification). This text is therefore being used (again) with some revision including the addition of wording to specifically identify the associated function (i.e., " Degraded Voltage Reset - 4.16 kV basis"). However, the second sentence of this note is no longer applicable due to completion of the previous modification. This wording should thus be eliminated as it is not applicable to the current, associated plant modification. (5) Footnote (b) to Table 3.3.8.1-1 is proposed to be revised to maintain the currently specified drop-out point for the degraded voltage relay until the recent, associated modification is completed. The current text of this note was based on the aforementioned previous modification (s) made to the degraded voltage relays (addressed in Amendment 110). l g  ; . - # V 4t ? y %Y g W W i e r t

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'i! G s , ) k( Attachment 2 to U 603146 LS-98-012 Page 7 of13 (6) Neta (c) to Table 3.3.8.1-1 is proposed to be deleted since it is no longer needed. Similar to Notes (a) and (b), this note was incorporated via Amendment 110 to _ . address modifications being made to the degraded voltage relays at that time. [ Note (c) was needed due to a modification made to the Division 3 degraded voltage relay logic and the associated number of relay channels.] Completion of those modifications makes Note (c) unnecessary. Deletion is required to avoid ( confusion with the modification currently being implemented. (7) Technical Specification testing requirements for the emergency standby diesel generators (DGs) refer to a required minimum steady state bus voltage. The value for the required minimum steady state voltage is proposed to be changed from 2 3870 to 2 4068 in Surveillance Requirements (SRs) 3.8.1.2, 3.8.1.7, 3.8.1.11, \ 3.8.1.12,3.8.1.15,3.8.1.19, and 3.8.1.20. The proposed TS changes are reflected on a marked-up copy of the affected pages from the CPS TS in Attachment 3. In addition, changes to the CPS TS Bases, consistent with the proposed TS changes, are provided for information only in Attachment 4. Technicas Basis and Evaluation for Proposed Changes to Degraded Voltare Relav Setooints and Minimum Required Bus Voltare Methodology for Establishina Degraded Voltage Relav Setpoints The methodology used to establish the new degraded voltage relay (DVR) setpoints is the same as that described in IP's previous amendment application involving changes to the degraded voltage relay setpoints, which resulted in Amendment 110 to the CPS Operating License. A summary of the approacii being taken, consistent with the approach taken for Amendment 110, is provided as follows. Calculation of the DVR setpoints themselves is being performed under calculation 19-AN-19. (Final verification of the DVR TS Allowable Values will be provided when all of the supporting calculations are complete.) The methodology used in this calculation is consistent with industry guidance and was reviewed by the NRC staff during their review for Amendment 110. The NRC's review of Amendment 110 included consideration of the characteristics and specifications for the Asea Brown Boveri 27N relays (which were new at the time ofIP's application leading to Amendment 110), the associated, instrument uncertainties and drift allowance, and the uncertainties associated with the relay logic configuration for both the dropout and reset function. Resolution of these issues and acceptance ofIP's calculation methodology is reflected in the Safety Evaluation issued by the staffin support of Amendment 110. On that basis, the same methodology is being used to calculate the new, proposed DVR setpoints under updated calculation 19-AN-19. 4 Attachment 2 8 to U-603146 4 . LS-98-012 Page 8 of13 l As noted in the staffs Safety Evaluation for Amendment 110, calculation 19-AN-19

establishes DVR setpoints based on analytical values determined in calculation 19-AQ-02.

The analytical values are based on the minimum required voltage necessary to assure i proper operation of essential / safety electrical loads. Values / limits calculated under 19-AQ-02 include the level to which bus voltage must recover following the starting

transient that occurs during a LOCA when accident loads are loaded onto the bus, and the voltage that would allow safety loads to continue to operate properly during steady state l operation. These values establish the analytical limits for the DVR reset point and dropout i point, respectively, as utilized in Calculation 19-AN-19. Again, the methodology being i utilized in calculation 19-AQ-02 to support the new, revised DVR setpoints is the same as j that used previously, except as described below.

l In earlier circuit analyses and voltage calculations performed by IP (and as originally described in LER 94-005), detailed modeling of plant electrical loads down to the 120-volt

level was not performed. Under subsequent analyses performed by IP, more detailed analyses were performed at the 480-volt level to identify the most susceptible 120-volt ,

circuits. A sampling of the susceptible 120-volt circuits for analysis at that level identified l 3 a population oflimiting 120-volt circuits, from which required voltage limits for the 4.16 1 kV buses were established and utilized. Further analyses are now being completed for all required 120-velt circuits of concern These 120-volt circuit analyses are being completed , under calculation 19-AJ-74. I Results from this calculation have indicated that, in order to install a minimum number of regulating transformers such that adequate voltage will be available to the susceptible 120-

volt circuits (through appropriate plant modifications, as described previously), the 1

minimum required bus voltage must be increased by a nominal amount. Consequently, it ! has been determined that the minimum required bus voltage will be increased i approximately 5%. To support the increased minimum bus voltage requirement, a j corresponding boost in the secondary voltage from the RAT will be made. A 5% boost corresponds to moving the RAT tap setting two positions. A 5% beost in the minimum required bus voltage corresponds to an analytical limit for the DVR dropout setpoint of I 4035 V and an analytical value for the DVR reset point of 4118 V. I i Impact of SVC Operation ! As noted previously, with the increase in the minimum required bus voltage (to i accommodate the limiting 120-volt circuits), along with the required higher RAT tap setting and higher degraded voltage relay setpoints, advantage is taken of the RAT SVC ! to enable bus voltage to be maintained greater than or equal to the minimum required voltage over the entire range of expected offsite voltages for the next fuel cycle. Figure 2 (page 9 of this attachment) illustrates this condition. Attachment 2 to U-603146 LS-98-012 . Page 9 of 13 T 1.033._ __________________________________________________ i i

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i i N i  ! , O.96 _ ' 8 s %*  ! 0.94 _ i g g, i / existin9 oes neiev l t i O. 94 0.96 0.98 1.-00 1.02 1.04 1.06 345 KV i 1.033._ _____-__________________________ ___________________ ___ 'S

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g 0. 98 _ ' 0.96 _. / g,oposeg ogg ge,,y 4 0.94 _ 0.92 _ 0.94 0.96 0.98 1.00 1.02 1.04 1.06 345 KV I Figure 2 l 1 LS-98-012 Page 10 of13 Referring to the figure, both graphs are plots of 4.16 kV bus voltage versus offsite (345 kV) voltage. The top half of the figure (upper graph) shows what this voltage relationship looks like for the SVC working with the RAT set at tap No. I with the DVR trip band set as currently required. The lower graph shows the effect of SVC operation with the RAT set at tap No. 3. In the upper graph, it can be seen that although the current minimum required 4.16 kV bus voltage can be maintained over the entire range of expected offsite voltages, bus voltage begins to fall offwith offsite voltage less than approximately 0.99 pu since the control range of SVC operation cannot be maintained below 0.99 pu when the RAT is set at tap No.1. The lower graph shows that with RAT set to tap No. 3, the control range of SVC operation is shifted so that the SVC can maintain the new minimum required 4.16 kV voltage with offsite voltage down to 0.94 pu, which is the projected minimum expected offsite voltage for CPS Operating cycle 7. This figure also shows the full extent of control range for the SVC, including the point at which the SVC can no longer hold voltage down for increasing bus /offsite voltage. Referring to the lower half of the figure, and as noted above, even with the SVC in operation there is a rise in 4.16 kV bus voltage at the upper end of the expected offsite voltage band. For this case,4.16 kV bus voltage is still maintained below the desired maximum 4.16 kV bus voltage. Without the SVC in operation, however, the figure shows that 4.16 kV voltage exceeds the desired maximum bus voltage when offsite voltage exceeds approximately 1.01 pu. This suggests that a potential overvoltage condition could occur in the event of an SVC trip. This is further discussed below. Evaluation of Overvoltage As noted above, with the RAT tap set at position No. 3, the potential for an overvoltage condition exists when offsite (345 kV) voltage exceeds approximately 1.01 pu and the RAT SVC is not in operation. This condition could also occur unexpectedly in the event , of an SVC trip. IP has evaluated this potential condition, including the magnitude of the I overvoltage, the probability of occurrence, and what contingencies or compensatory measures exist or can be put into place to prevent or mitigate overvoltage. It should be noted that during completion of the 120-volt circuit analyses (pursuant to calculation 19-AJ-74), IP identified not only those circuits having a potential undervoltage condition, but also those circuits having a potential overvoltage concern in light of changing the RAT tap 5%. Those circuits are planned to be resolved through appropriate plant modifications and are included in the previous discussion of the 27 circuits to be modified during the current outage. As noted previously, the RAT is capable of supplying power to the safety buses as well as the balance-of-plant (BOP) buses. (The ERAT does not have this capability.) Normally, the BOP loads are connected to the unit auxiliary transformers (UATs) where power is l extracted directly from the main generator. Transfer capability (both automatic and j manual) exists to allow transfer of the BOP buses from the UATs to the RAT. BOP loads l Attachment 2 to U-603146 LS-98-012 Page 11 of13 connected to the RAT will thus tend to drop voltage at the 4.16 kV level. This capability can be unlized to mitigate the overvoltage potential when the RAT SVC is out of service. The three conditions required to effect an overvoltage condition (with safety loads connected to the RAT) are as follows: (1) Offsite (345-kV) voltage exceeds 1.0lpu, (2) BOP loads are lost or less than some desired minimum level, and (3) The RAT SVC is out ofservice. IP has developed measures to prevent or mitigate an overvoltage condition when all three safety buses are being supplied by the RAT. These measures include establishing operating practices such that the BOP buses will normally be supplied from the RAT (vice the UATs). This practice will eliminate the possibility of an overvoltage condition on the safety buses in the event of a trip of the RAT SVC. Procedural changes will be performed such that if the total RAT 4.16 kV load becomes less than required to protect against an overvoltage condition (in the event of the SVC trip), operators will transfer either the Division 1,4.16 kV bus or the Division 2,4.16 kV bus to the ERAT. Although the potential for overvoltage to cause any significant equipment damage is believed to be extremely remote, dividing the buses as described reduces the potential for overvoltage to be a common mode condition. Basis for No Significant Hazards Determination In accordance with 10CFR50.92, a proposed change to the Operating License (Technical Specifications) involves no significant hazards considerations ifoperation of the facility in accordance with the proposed change would not: (1) involve a significant increase in the probability or consequences of any accident previously evaluated, or (2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin of safety. The propos,xi changes are evaluated against each of these criteria below. (1) The proposed changes do not involve a significant increase in the probability or consequences of any accident previously evaluated. The degraded voltage relays are designed to respond to degraded voltage conditions from the offsite sources, and are not initiators of such a condition themselves. However, proper establishment of the degraded voltage relay setpoints is necessary to avoid inadvertent or unnecessary disconnection of the offsite source and transfer to the standby diesel generators (DGs) when the offsite sources are still capable of supplying adequate power to the plant safety buses. At the same time, proper establishment of the setpoints must also ensure that a transfer will occur when required so that power can be provided to safety loads, with voltage at greater than or equal to the minimum required voltage. The revised degraded voltage setpoints were established consistent with these requirements using an NRC-approved methodology. The revised setpoints (and the revised minimum bus voltage specified in the DG surveillances) take into Attachment 3 to U-603146 LS-98-012 Page 12 of13 the revised minimum bus voltage specified in the DG surveillances) take into account the new minimum required bus voltage required for all safety loads based on a more in-depth circuit analysis. Concurrently, the expected range of offsite voltage has been factored into the setpoint calculations to ensure that the offsite source can reset the degraded voltage relays at the minimum expected offsite voltage, thus maximizing the availability of the offsite source consistent with the intent of 10CFR50 Appendix A General Design Criterion 17. Raising the degraded voltage relay setpoints does not increase the probability of transferring the safety buses to the DGs. This is because the existing margin between the safety bus voltage (based on the minimum expected offsite voltage) and the upper reset value of the degraded voltage relay will be maintained by the static VAR compensators that are installed on the CPS auxiliary power system. Chapter 15 of the Clinton Updated Safety Analysis Report (USAR) discusses the effects of anticipated process disturbances to determine their consequences and the capability of the plant to control or accommodate such events. Subsection 15.2.6 discusses lou of a-c power, including loss ofgrid voltage. This discussion demonstrates that fuel design limits and reactor coolant pressure boundary design conditions are not exceeded. The proposed changes do not affect the discussion nor the conclusion of this evaluation. Due to the associated change in the tap setting for the reserve auxiliary transformer (RAT), the proposed changes involve some increased potential for overvoltage for certain loads. Although the estimated magnitude of the overvoltage to those loads is not severe, procedural guidance will be established to prevent or mitigate such a condition. This will minimize the potential for equipment failure due to overvoltage. Therefore, this aspect of the proposed changes does not involve a significant increase in the probability of failure of equipment important to safety. Based on all the above, the proposed changes do not involve a significant increase in the probability or consequences of any accident previously evaluated. (2) The proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed changes involve setpoint changes for the degraded voltage relays and a change to the minimum bus voltage required to be achieved during DG testing. The setpoint changes to the relays alters their performance in an intended manner but in no other way affects their intended function. The change to the DG surveillance criteria is primarily administrative since the DGs have repeatedly shown that they are able to achieve this value during testing. The DGs themselves are physically unaffected. These changes by themselves thus involve no physical changes to the facility, no new failure modes or initiating conditions that could lead to a new or different accident. l Attachment 2 to U-603146 l LS-98-012 Page 13 of13 Notwithstanding the above, and as noted previously, the associated change in the RAT tap setting could involve an increased potential for overvoltage to some plant loads. As noted above, however, this potential is reduced by providing procedural guidance to plant operators. The potential for equipment failare due to overvoltage is thus minimized, and no new failure mode is thus introduced. Based on the above, the proposed changes do not involve any significant increase in the failure of plant equipment due either to overvoltage or inadequate voltage, and do not introduce any new failure modes or conditions that could lead to a new or different kind of accident. On this basis, the proposed changes do not create the possibility of a new or different accident from any accident previously evaluated. (3) None of the proposed changes involve a significant reduction in a margin of safety. The margin of safety that may be associated with the degraded voltage relays is the margin involved in ensuring adequate voltage to plant safety loads. The revised degraded voltage relay setpoints, as proposed, were established by an NRC-accepted methodology that ensures the revised setpoints will maintain this margin of safety. Consistent with this determination, the proposed revision of the lower voltage limit for the DG surveillances (SR 3.8.1.2, SR 3.8.1.7, SR 3.8.1.11, SR 3.8.1.12, SR 3.8.1.15, SR 3.8.1.19, and SR 3.8.1.20) will assure that the DGs will be capable of controlling voltage to a range that will be adequate for the loads on the bus. This value was detennined using revised voltage calculations and is consistent with the proposed degraded voltage setpoints. Therefore, the proposed changes do not involve a significant reduction in a margin of safety. Based on the foregoing, IP concludes that this request does not involve a significant hazards consideration. l

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