U-602972, Application for Amend to License NPF-62,incorporating Requirements for Static Var Compensator (SVC) Protection Sys Under New TS
| ML20216B118 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 05/04/1998 |
| From: | Walter MacFarland ILLINOIS POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20216B123 | List: |
| References | |
| U-602972, NUDOCS 9805150044 | |
| Download: ML20216B118 (18) | |
Text
liknois Power Comsany Chnton Power Staton P O ecx 678 Chnton IL 61727 Tel 217 935 5023 Fax 217 9 ~! S.4632
, Walter G MacFarland IV Senior ute Prevdent and Ch+f Noaear GNw NMR U-602972 An Illinova Company 8E.100a j May 4, 1998 Docket No. 50-461 10CFR50.90 Document Control Desk Nuclear Regulatoiy Commission Washington, D.C. 20555
Subject:
Clinton Power Station Proposed Amendment of Facility Operating License No. NPF-62 (LS-98-001)
Dear Madam or Sir:
In recent meetings and discussions between Illinois Power (IP) and NRC staff personnel, IP has had the opportunity to update the NRC staff on the degraded grid voltage issue at the Clinton Power Station (CPS) and to present an overview of planned modifications that are now underway to address this probIem.
In order to assure CPS has two circuits of offsite power with adequate capacity and capability in accordance General Design Criterion 17 of10CFR50, Appendix A, two static VAR compensators (SVCs) are being installed for connection to the CPS auxiliary power system. Specifically, one SVC is being installed for connection to the secondary (4.16-kV side) of the CPS reserve auxiliary transformer (RAT), and the other SVC is being installed for connection to the secondary (4.16-kV side) of the CPS emergency reserve auxiliary power transformer (ERAT). (The RAT is associated with the offsite 345-kV transmission system, and the ERAT is associated with the offsite 138-kV transmission system. These two transmission systems, i.e., their circuit connections to the CPS auxiliary power system via the RAT and ERAT, respectively, constitute the two required offsite electrical power sources for CPS.)
SVCs are highly reliable and effective in providing voltage support, and as such they have been used for many years in electrical transmission and distribution systems throughout the world. The SVCs for CPS are being supplied by Asea Brown Boveri (ABB), and each will be provided with an enhanced protection system. A summary of ABB's experience with SVCs (installed and planned applications) is included in Attachment 7. A design report describing the SVCs being installed at CPS and their 4;i operation, including a failure modes and effects analysis (FMEA) for the SVCs, is provided as Attachment 6 to this letter. \
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9805150044 980504 PDR ADOCK 05000461 P PDR m . . _ . . . _
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U-602972 LS-98-001 Page 2 The FMEA demonstrates that, for the SVCs to be installed at CPS, there is no single failure of an SVC that would adversely impact safety-related equipment since each postulated failure is mitigated by the enhanced protection system provided for each SVC.
A probabilistic risk assessment (PRA) has also been performed, and it demonstrates that for an event involving the failure of an SVC that could lead to degradation of the plant safety busses and subsequent reactor core damage, the probability of such an event is 4
approximately 1.5 x 10 / year. This low event probability is primarily due to the low probability that results when SVC failure event probabilities are coupled with failure probabilities of the enhanced SVC protection system. Thus, because the SVC protection systems are relied upon to provide protection to the Class IE 4.16-kV busses in the unlikely event of an SVC malfunction that could adversely affect safety-related loads, it ha been determined that the plant Technical Specifications should be changed to incorporate requirements for the SVC protection systems.
Based on the above, and pursuant to 10CFR50.90, IP hereby applies for amendment of Facility Operating License No. NPF-62, Appendix A - Technical Specifications, for CPS. The proposed change would incorporate requirements for the SVC protection systems under a new Technical Specification. These requirements include a Limiting Condition for Operation (LCO), Required Actions in the event that the SVC protection system (s) is declared inoperable, and appropriate Surveillance Requirements for periodically testing / verifying operability of the SVC protection systems.
l Additional information and documents are provided as attachments to this letter.
An aflidavit supporting the facts set forth in this letter and its attachments is provided as l Attachment 1 A more detailed description of the proposed Technical Specification i changes, as well as an evaluation for no significant hazards consideration is provided as !
Attachment 2. An evaluation for environmental impact consideration is provided in Attachment 3. Proposed (new) pages for the CPS Technical Specifications, reflecting the proposed changes, are provided as Attachment 4. A marked-up copy of the affected pages from the current Technical Specification Bases along with new Technical 1 Specification Bases for the new SVC protection system Technical Specification are l provided as Attachment 5. The required Bases changes will be incorporated following NRC approval of the proposed Technical Specification changes, in accordance with Technical Specification 5.5.11, " Technical Specification Bases Control Program."
This submittal may be regarded as an initial submittal for IP's amerdment application regarding the SVCs and their protection systems. As indicated in recent discussions with the NRC, activities such as the completion of calculations to support the associated plant modifications are ongoing. IP thus anticipates that information gained l from completion of these activities, or in response to requests from the NRC, may need to be incorporated into this amendment application. Accordingly, follow-up submittals will be provided as required.
U-602972 LS-98-001 Page 3 With respect to additional submittals, it should be noted that a separate submittal is currently being prepared to address installation of a load tap changer (LTC) to replace the
' fixed-tap transformer for the ERAT. As discussed in earlier meetings with the NRC, IP's l
original plans called for having the SVCs installed before this summer, and installing LTCs i for the RAT and ERAT at a later date. Due to the extended schedule that resulted for installation and testing of the SVCs, the decision was made to install the more immediately ;
available ERAT LTC to provide voltage support for the plant even while in a shutdown condition this summer. Since the Technical Specifications only require one offsite source to be operable while the plant is in a shutdown condition, installation of the ERAT LTC will support continued compliance with the Technical Specifications throughout the summer when offsite voltages are at their lowest. The ERAT LTC submittal will be submitted in the near future. Due to the more immediate need for NRC review and approval of that submittal, IP respectfully requests that it receive first priority upon ,
receipt. j As noted in previous discussions about the SVCs with the NRC (and not withstanding installation and use of the ERAT LTC prior to installation and use of the SVCs), calculations indicate that under certain conditions, the voltage associated with the two offsite power sources for CPS could be outside the acceptable voltage range without the SVCs in service IP thus intends to place both SVCs in service prior to returning CPS to service from tiie current outage. Since an approved amendment is required before the
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SVCs can be connected (energized) to the plant power system, IP's intent is to gain I approval of this amendment request in a time frame to support startup testing of the SVCs beginning this August. Therefore, IP respectfully requests timely review and approval of {
this request to support that intent.
Sincerely Yours, 1 T ) ,
aMl Walter G. MacFarland, IV 2
Senior Vice President and Chief Nuclear Officer TBE/mlh Attachments cc: NRC Clinton Licensing Project Manager NRC Resident Office, V-690 NRC Regional Administrator, Region III Ill:nois Department of Nuclear Safety f
I Attachment 1 to U-602972 Page1of1 l
l Walter G. MacFarland, IV, being first duly sworn, deposes and says: That he is Senior !
l Vice President and Chief Nuclear Officer for Clinton Power Station; that this application l for amendment of Facility 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. l l
Date: This [ day ofMay 1998.
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Signed: :
).) -c.r 6 lM &
l Walter G. hiacFarland,'IV STATE OF ILLINOIS l 'N SS. Jeogerms s."usahias ,
f '
newy Mas, man sialasis
)< */ COUNTY J Mr Commission E$es 11% j Subscribed and sworn to before me this '9 day of May 1998. j 491aANe W- YW '
/ [/ Notary Public)'
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Attachment 2 to U-602972 Page 1 of 10
1 Background
As discussed in Section 8,3.1 of the Clinton Power Station (CPS) Updated Safety Analysis Report (USAR), the primary offsite source of power for the Unit Class 1E AC power system is via the Reserve Auxiliary Transformer (RAT) which is connected to a 345-kV off-site 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 to a separate, independent 138-kV off-site 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 ,
General Design Criterion (GDC) 17, " Electric Power Systems" The CPS electrical {
system configuration (prior to SVC installation) is shown on Figure 1 of Attachment 6.. j I
As identified in CPS Licensee Event Report 94-005 (Illinois Power letter U-602296 dated l June 3,1994), Illinois Power (IP) identified that the secon9-level undervoltage (degraded voltage) instrumentation at CPS was not adequate to automatically ensure that sufficient voltage would be provided to all Class IE loads, particularly at several 120-VAC distribution panels. As interim corrective action, IP installed an alarm for the 4.16-kV l safety-related busses and established contingent operator actions in order to minimize the i potential for the Class IE loads to receive inadequate voltage. Longer term actions were initiated to develop design change options for restoring the plant to its licensing basis for
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automatic degraded voltage protection. One action that was taken was to procure more accurate, state-of-the-art relays to replace the existing degraded voltage relays.
By letter dated February 22,1996, and to support use of the new relays, IP proposed an amendment to the CPS Technical Specifications to revise the setpoints (Allowable Values) for the 4.16-kV degraded voltage relays. Extensive calculations were performed in support of the amendment to assure that continuous duty motors and motor-operated valve motors had adequate starting voltage. The revised setpoints were approved by the NRC in Amendment 110 to the CPS Operatir.g License, dated December 4,1996, and the new relays were subsequently installed during the sixth refueling outage in early 1997.
Also in early 1997 (while CPS remained in a shutdown condition), additional calculations were performed to assess required voltages for plant equipment. From these calculations, offsite source voltage limits were established (at the 4.16-kV level) for determining when an offsite source must be declared inoperable. Subsequently, in mid-1997, IP determined that for frequent but short periods of time, voltage on one of the offsite power sources was not able to be maintained above the minimum required value conservatively established for CPS. This occurred primarily due to unusually low voltages occurring as a result of a lack of operating generators in Illinois, coupled with high summer load demands during peak hours. In response to this situation, and in anticipation of plant startup at that time, a computer model of the IP electrical system was developed that can predict grid voltages under various load and generation conditions. This " predictor model" can be used in predicting resultant grid voltages in the event of CPS tripping off-line.
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a Attachment 2 to U-602972 Page 2 of 10 l
i The issue ofinoperability of an offsite source with respect to the Technical Specifications, as well as the offsite source " capacity and capability" requirements of GDC 17, was discussed in various meetings and telephone conferences between the NRC staff and IP l personnel in early to mid 1997. On July 22,1997, a request for a temporary partial exemption to GDC 17 was requested. This temporary partial exemption would have
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allowed plant operation with one of the two offsite power sources experiencing j intermittent periods ofless than the minimum required voltage. However, by letter dated i September 30,1997, this exemption request was withdrawn while CPS remained in a shutdown condition. !
l Due to the recognhion of reduced margins for ensuring adequate voltage to loads at CPS, and in recognition of a need to implement plant modifications to recover required margins, additional 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. As shown in Tables 10 and 11 in Attachment 6, the predicted vohage available at the CPS 4.16-kV safety busses would be significantly less than required, assuming a loss of coolant accident (LOCA) and unit trip. It was therefore recognized
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l that major actions are needed to ensure the future operability of the offsite power sources !
for CPS.
To correct this degraded voltage condition, IP will be performing upgrades to the CPS auxiliary power system that include a number of modifications. These include the following:
- 1) Installation of 480/120-volt regulating transformers (to replace selected non-regulating 480/120-volt transformers used in the CPS auxiliary power system).
In addition to these modifications, future plans include replacement of the RAT with an LTC transformer. In the meantime, and as discussed in the cover letter, replacement of the ERAT with an LTC transformer will begin as soon as possible. However, because IP has determined that the ERAT LTC modification involves an unreviewed safety question, NRC approval of that modification will also be required prior to implementation. NRC approval of that request will be sought via a separate submittal. With respect to installation of 480/120-volt regulating transformers, such installation will begin this spring or summer, and is being evaluated pursuant to 10 CFR 50.59. The focus of this license amendment request is therefore on the SVCs and their associated protection systems.
l Attachment 2 to U-602972 Page 3 of 10 l
The SVCs and Associated Protection Systems As discussed in the January 27,1998 meeting between IP and the NRC, aspects of the CPS design, including a large non-safety related load on the RAT (in addition to its safety-related load), the fact that LOCA loads at CPS are essentially " block" started (not sequenced), and the fact that CPS operation substantially supports grid voltage (so that a significant voltage drop occurs when Clinton trips off-line), require the CPS auxiliary l l power system to accommodate a wide voltage range as well as the transient conditions associated with LOCA loading. Long-term considerations favor the use ofload tap changers (LTCs) to accommodate a wide range of steady-state voltage, in combination with SVCs to provide transient voltage support due to their ability to quickly respond to rapidly changing conditions, including the transient loading conditions postulated for a design basis accident (DBA) LOCA. (The SVCs can also provide steady-state voltage support as well, without the LTCs. However, the LTCs will be needed to accommodate l the complete range of voltage projected to be necessary based on long-term forecasts.)
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As noted previously, the SVCs to be sed at CPS have been purchased from Asea Brown j Boveri (ABB). ABB SVCs are highly reliable and have been used for many years in electrical transmission and distribution systems and industrial applications throughout the world. A summary of ABB's experience (installed and planned applications) with SVCs is included in Attachment 7.
SVC design and operation was discussed with the NRC staffin the January 27 and March 19,1998 meetings conducted at White Flint. Each SVC is rated at +28.5/-14.0 MVAR j and includes a thyristor controlled reactor bank rated at 21.5 MVAR, a thyristor-switched l capacitor bank rated at 21.0 MVAR, and a harmonic filter bank rated at 7.5 MVAR as shown in Figures 8 and 9 of Attachment 6. The filter bank is always connected to the 4.16-kV bus whenever the SVC output breakers are closed, and provides a capacitive 7.5 MVAR supply. The SVC normally maintains operation in the lower inductive range, typically 0-7 MVAR inductive, in order for the SVC to retain its full capacitive range in reserve to counteract large system voltage drops and/or motor starting. Additional details concerning the SVCs, as well as the results of the FMEA, are provided in Attachment 6.
Installation of the SVCs on the 4.16-kV RAT and ERAT busses was determined to be the most effective means for resolving the degraded grid voltage problem for CPS As discussed in the January 27 and March 19 meetings with the NRC, SVCs could have been- j added to the 345-kV and/or 138-kV transmission systems either on the CPS site or at a distance from the CPS site. Onsite SVCs were chosen because they put voltage control where it is needed. The SVCs will thus be added to the CPS auxiliary power system as shown on Figure 7 in Attachment 6. With the SVCs installed, the predicted 4.16-kV bus voltages for the RAT through the year 2007 and for the ERAT through the year 2001 are shown in Tables 12 and 13 in Attachment 6.
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Attachment 2 to U-602972 Page 4 of 10 As noted in the cover letter, the SVCs provided by ABB for use at CPS are provided with enhanced protection systems. As they are normally provided for industrial use, ABB
!- SVCs are equipped with a control and protection system that includes a programmable high speed controller, thyristor monitoring circuit and other features (as described in Attachment 6) that collectively provide some degree of protection for the SVC and its
!- load. Howe -r, for use at CPS, each SVC has been provided with additional or enhanced protection capability. The enhanced protection system for each SVC has two redundant
, subsystems (with battery back-ups) to protect the SVC load from the fault conditions l identified in the FMEA (included in Attachment 6).
l l As also noted in the cover letter, the FMEA and PRA yield favorable results when the l enhanced SVC protection systems are taken into account. The results of the PRA analysis l performed for the SVCs confirm that the enhanced protection system provided for each l SVC substantially reduces the probability of an SVC failure leading to degradation of l plant safety-related equipment to an acceptably small level. Specifically, the probability of an event involving a potentially harmful failure of the inservice SVC leading to damage of
- safety-related equipment in multiple electrical divisions and the subsequent occurrence of 4
l reactor core damage was calculated to be 1.5 x 10 / year. This places such an event below the threshold of credibility primarily due to the protection provided by the enhanced SVC l protection system (s). On this basis, and as discussed at the March 19,1998 meeting l between IP and NRC personnel, the SVC protection systems are important for protecting the CPS 4.16-kV safety busses and should thus be addressed in the CPS Technical Specifications.
l DescrictiojLof the Proposed Change Due to the critical role of the SVC protection system in protecting the Class IE 4.16-kV busses and connected loads, and consistent with the criteria of 10CFR 50.36, a new Technical Specification for the SVCs is proposed for incorporation into the CPS Technical Specifications. Accordingly, a Limiting Condition for Operation (LCO) and Surveillance Requirements (SRs) are proposed as follows:
- 1) Under new Technical Specification (TS) 3.8.11, " Static VAR Compensator (SVC)
Protection Systems," LCO 3.8.11 is proposed such that it requires an SVC protection system, consisting of two independent SVC protection subsystems, to be OPERABLE l for each inservice SVC.
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- 2) An Applicability of "During SVC operation"is proposed such that an SVC's protection system must be OPERABLE when the SVC is in operation (i.e., in service).
- 3) Required Actions for when one protection subsystem of a required SVC protection system is inoperable, and for when both protection subsystems of a required SVC protection system are inoperable, are proposed. A Completion Time of 30 days is proposed for the former (Condition "A"), and a Completion Time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (to restore one SVC protection subsystem to OPERABLE status) is proposed for the
Attachment 2 to U-602972 ,
Pagc 5 of 10 !
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latter (Condition "B"). With either of these Required Actions not met within its required Completion Time, proposed Condition "C" is entered, wherein the associated ;
SVC output breaker (s) must be opened to remove the SVC from service within one j hour. {
In addition, a note for the Actions section is proposed to allow " separate condition" entry for each SVC protection system.
- 4) Two Surveillance Requirements are proposed: j
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(i) SR 3.8.11.1 requires, at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, performance of a local, l visual check of the SVC system control and status panel to confirm satisfactory operation of the SVC protection system.
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l (ii) SR 3.8.11.2 requires that, at least once per 18 months, a system functional test )
! of each SVC protection subsystem be performed, including actuation of the i associated SVC main circuit breaker.
Justification for Proposed Changes As noted previously, each of the SVCs employed for use at CPS is equipped with an enhanced protection system consisting of two independent protection subsystems. For <
I l each SVC, the protection subsystems interface with the SVC control system to protect the CPS Class IE safety busses from any SVC fault condition that could potentially damage the busses. Although such a fault condition is very unlikely, the FMEA and PRA performed for the SVCs yield the most favorable results when the protection systems are l taken into account. The proposed changes to the CPS Technical Specifications to l incorporate LCO and surveillance requirements for the SVC protection systems ensures l that the protection systems will be maintained OPERABLE as required and that i appropriate action is taken in the event one or both subsystems of an SVC protection l system (for an inservice SVC) are determined to be inoperable.
Proposed LCO 3.8.11 and its Applicability would require both subsystems of an SVC protection system to be OPERABLE whenever the associated SVC is in service. As noted in the proposed changes to the Bases for LCO 3.8.11, an SVC is "in service" (or "in operation") whenever it is connected to the associated auxiliary transformer (RAT or ERAT), the transformer is energized by the offsite network, and the transformer is supplying power to at least one ESF bus or automatic transfer capability to that l transformer exists such that it could supply power to at least one ESF bus. As also noted in the proposed changes to the Bases for LCO 3.8.11, the requirements for the offsite electrical power sources are dictated by CPS Technical Specification (TS) 3.8.1, "AC Sources-Operating," or TS 3.8.2,"AC Sources-Shutdown." Requiring a protection system to be OPERABLE for each inservice SVC is consistent with the assumptions of the PRA performed by IP for the SVCs and their potential impact on the safety busses.
Attachment 2 to U-602972 Page 6 of 10 !
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The proposed Conditions, Required Actions and Completion Times address having one or l both subsystems for each SVC protection system inoperable for each inservice SVC. An allowed out-of-service time (i.e., Completion Time) of 30 days for one protection subsystem inoperable (Condition "A") has been determined to be acceptable on the basis that it permits a reasonable time to restore OPERABILITY relative to the risk of having only one protection subsystem OPERABLE The PRA performed by IP supports this completion time. Similarly, risk analyses support a completion time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore at least one of two inoperable protection subsystems to OPERABLE status (Condition "B"), while the other inoperable SVC protection subsystem must continue to be restored to OPERABLE status within 30 days from the time when the first SVC protection subsystem became inoperable. If neither of these Required Actions can be met within the specified Completion Times, Condition "C" applies such that Required Action C.1 requires opening at least one of the two SVC main circuit breakers within one hour to disconnect the associated SVC from the bus (i.e., remove it from service). The Completion Time of one hour permits disconnecting the SVC in an orderly fashion, including assessing the impact of removing the SVC from service with respect to the offsite source (s) and its capability to provide proper voltage. j l
It should be noted that removing an SVC from service would not necessarily make the associated offsite circuit inopert.ble Removing an SVC from service would prompt evaluation of the offsite source to determine whether the source (s) is capable of supporting adequate voltage to plant loads under design basis conditions. As discussed !
previously, IP has developed a " predictor model" that is particularly useful for determining, while CPS is operating and supporting grid voltage, what the voltage would be at the site (4.16-kV level) in the event of a DBA LOCA and associated plant trip. This can be used to assess the operability of the offsite source (s) when the associated SVC(s) is removed from service. If an offsite source was determined to be inoperable (with an SVC removed from service), the Required Action of TS 3.8.1 or 3.8.2 would then apply.
Appropriate changes to the Bases for these Technical Specifications have been proposed i I
to acknowledge these provisions.
The proposed Note regarding multiple condition entry allows the Condition (s) and Required Action (s) to be entered and tracked separately for each SVC protection system.
Thus, for example, if one protection subsystem was inoperable for the ERAT SVC, and one protection subsystem was inoperable for the RAT SVC, Condition A and its Required Action A.1 would be tracked .wparately for the inoparable ERAT SVC protection subsystem and for the inopenble RAT SVC protection subsystem.
The Surveillance Requirements proposed for the SVC protection system are based on the ,
vendor's recommendations, consideration of the SVC protection system design, and {
consideration of testing requirements for similar components / equipment. SR 3.8.11.-1 is a l daily basic system status check to ensure that the SVC protection systems are in service and to identify any alarm or trouble conditions. This would be implemented by checking the SVC system control and status panel located within the SVC control building located near each SVC. (Although a supervisory trouble alarm will be provided in the main .
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Attachment 2 to U-602972 Page 7 of 10 l
control room for the SVCs, more extensive status indication will be obtainable locally m the SVC control building (s).)
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SR 3.8.11.2 would be required to be performed at least once per 18 months. It requires performance of a system functional test to verify that each protection subsystem trips the associated SVC's main circuit breakers in response to the various input trip signals, ;
particularly for the following conditions: )
(1) Overvoltage (2) Undervoltage (3) Phase Unbalance (4) Overcurrent (5) Harmonics The above trip input signals are primarily derived from sensors that are potential or current transformers. On this basis, inputs for the purposes of system functional testing can be actual or simulated. As noted in the proposed Bases for this SR, however, consideration must be given to a sensor's failure mode for determining whether the sensor itself must be tested. The specified frequency of 18 months is consistent with other Technical Specification Surveillance Requirements for such kinds of tests, and it is consistent with vendor recommendations wherein it is not recommended that such testing be done during plant operation.
Evaluation for Sinnificant Hazards Consideration In accordance with 10CFR 50.92, a proposed change to the operating license involves no significant hazards consideration if operation 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, (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. This request is evaluated against each of these criteria below:
(1) The changes addressed by this amendment request involve the addition of SVCs l
and their associated protection systems to the onsite circuit connections for the
, plant offsite electrical power sources, i.e., to the RAT and ERAT. As noted l throughout this request, the addition of the SVCs will help to maintain voltage at the site for both of the offsite electrical power sources consistent with the
" capacity and capability" requirements of GDC 17. Further, the regulating effect of the SVCs will compensate for the voltage drop that can occur without the SVCs when the plant trips off-line (and thus no longer supports grid voltage) during normal or accident conditions. This supports compliance with the GDC 17 requirement to minimize the probability ofle'ng electric power from the offsite supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit. Consequently, the likelihood of transferring to the onsite
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f Attaclunent 2 to U-602972 Page 8 of 10 emergency power supplies (diesel generators) during an accident will be reduced.
At the same time, as also addressed in this amendment request, incorporation of the SVCs into the CPS auxiliary power system requires consideration of failure modes that could be introduced by the SVCs wherein such failure modes could involve a significant increase in the probability or consequences of any accident l previously evaluated.
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By supplying each of the SVCs with an enhanced protection system, consisting of dual, redundant protection subsystems, either of which will isolate the SVC from the bus (by automatically opening the SVC main circuit breakers) in response to postulated SVC failures or associated abnormal conditions, the potential for such conditions or failures to adversely affect the plant safety busses, the associated plant loads, or the onsite emergency electrical power sources is reduced to a very low probability. The protection systems designed for the SVCs include consideration of failure modes or abnormal conditions that may be postulated or expected to occur with some degree of probability for the offsite electrical sources l or grid with or without the presence of the SVCs, (such as a sustained degraded l voltage condition), as well as consideration of any new or other failure modes or abnormal conditions potentially introduced by the SVCs that would be less likely to occur in the offsite electrical network without the presence of the SVCs (such l
as the introduction of harmonics). The proposed change to the CPS Technical
- Specifications to incorporate requirements for the SVC protection systems will ensure that the SVC protection systems are adequately maintained in an operable l
l condition to perform their intended function of protecting against such conditions i or failure modes. Operable SVC protection systems will reduce the probability of l
an SVC failure event that leads to equipment damage and subsequent core damage to a level that makes such an event incredible.
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l It should be noted that tripping of the SVCs in response to an SVC failure or j
! abnormal condition does not result in a loss of power from the offsite sources. l l
Thus, the probability of a loss of offsite power, which is an analyzed event in the j i
plant safety analyses, will not be significantly increased by the SVC protection systems.
As noted previously, the proposed change to the Technical Specifications to incorporate SVC protection system operability and testing requirements would ensure that plant safety systems or components are not electrically affected by the SVCs in an adverse manner. In addition, except where the SVCs are physically located and connected to the ERAT and RAT via bus ducts, plant safety-related structures and supporting systems would not be mechanically affected by the SVCs. Separation, clearance and related requirements to ensure no other interaction with the RAT, ERAT and offsite source connections, as well as for maintaining offsite source independence would be maintained. On this basis, the safety functions of systems for preventing or mitigating analyzed events or accidents would not be impacted by the SVCs.
l Attachmeri 2 to U-602972 Page 9 of 10 l
Based on the above, the proposed change to the Technical Specifications does not involve a significant increase in the probability or consequences of any accident previously evaluated.
1 (2) In consideration of the potential adverse in.yacts that the SVCs may have on plant I systems, structures or components, such impacts are primarily confmed to potential electrical faults or abnormal conditions. As noted above, the SVCs have no mechanical impact on safety-related plant systems, structures or components.
Thus, no new failure modes or precursors to potentially new and unanalyzed events would be introduced via any mechanical means.
I With respect to potential adverse electrical impacts, the potential electrical failure modes or abnormal conditions postulated for the SVCs include conditions or l
events that, although could be considered possible for the offsite sources (i.e., the grid), were not in fact considered credible and therefore previously evaluated for the offsite electrical sources. These conditions or events, such as the introduction of harmonics or excessive overvoltage or phase imbalance caused by an SVC failure, would have the potential to degrade plant safety-related equipment connected to the busses at the time of the SVC failure if no protection for such conditions was provided. However, enhanced protection systems are provided for j the SVCs to ensure that such failures cannot damage plant equipment. As noted i previously, the probability of an event involving an SVC failure that leads to !
equipment damage and subsequent core damage has been calculated to be 1.5 x j 10 / year. This low probability makes such an event incrediblejust as comparable i events that could be postulated for the offsite electrical power sources were not previously considered credible and therefore were not considered to be design 4
basis events. The calculated probability of1.5 x 10 / year for an SVC failure event involving core damage is an order of magnitude lower than the threshold probability criterion specified in Section 2.2.3 of the Standard Review Plan (NUREG 0800) for design basis events involving an offsite hazard that can lead to l core damage and a radioactive release with dose consequences in excess of the l limits specified in 10 CFR Part 100.
l The proposed change to the Technical Specifications incorporates requirements for maintaining operability of the SVC protection systems. On this basis and as described above, no new credible accidents that could be associated with the SVCs (i.e., failure of the SVCs) are thus introduced, so that the proposed change does not create the possibility of a new or different kind of accident from any accident l previously evaluated.
(3) As noted previously, incorporation of the SVCs into the CPS auxiliary power system will support or regulate plant bus voltage for both of the offsite sources.
Specifically, analysis has shown that the SVCs will recover reduced margin that has occurred or would occur in the future (without the SVCs) with respect to the voltage required for plant safety loads and the minimum expected offsite voltage,
Attachment 2 to U-602972 Page 10 of 10 under normal and accident conditions (i.e., under steady-state and transient voltage conditions). This also means that the SVCs will enhance the capability and capacity of the offsite sources such that, when compared to the configuration of not having the SVCs, either source will be more likely to reset the safety bus degraded voltage relays in the event of an accident, thus permitting the preferred <
offsite sources to remain connected (and not causing a transfer to the diesel generators). These desirable results constitute a significant increase in the margin of safety with respect to voltage requirements for plant loads.
Based on the above, IP has concluded that the proposed change to the Technical Specifications to support use of the SVCs and their protection systems does not involve a significant reduction in the margin of safety.
Based on the conclusions reached for each of the foregoing criteria, IP has concluded that the proposed change involves no significant hazards consideration.
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Attachment 3 to U-602972 Page ! of 3 Environmental Assessment
Background
The Clinton Power Station (CPS) was designed to have two "immediate access" sources of offsite power. These offsite sources are associated with the 345-kV and 138-kV offsite transmission systems. The 345-kV system provides power to the CPS auxiliary power system via the Reserve Auxiliary Transformer (RAT), and the 138-kV circuit provides power to the CPS auxiliary power system via the Emergency Reserve Auxiliary Transformer (ERAT). This design for the offsite power sources meets the requirements of 10CFR50 Appendix A, GDC 17. The NRC's review, evaluation and acceptance of the design for the electric power system at CPS was documented in the CPS Safety Evaluation Report (NUREG 0853). {
The offsite power system for CPS, like those for other electric utilities, has experienced voltage swings on the grid (
Reference:
IEIN 98-07). These variations in voltage are I primarily the result ofload growth without the addition of new generation capacity. The l observed offsite voltages can be low during periods of peak demand and high when demand is low. As a result, CPS has identified a number of plant modifications that will control voltages provided to the onsite emergency loads from the offsite power sources.
These include the installation of selected 480/120-volt regulating transformers (to replace existing non-regulating type transformers within the auxiliary power system), replacement of the ERAT (and RAT) with a load tap changer transformer, and the addition of static VAR compensators (SVCs) on the 4.16-kV side of the RAT and ERAT. These modifications are intended to restore and maintain compliance with the originallicensing basis for the CPS auxiliary power system. This application for amendment addresses the incorporation of SVCs into the CPS auxiliary power system.
Need for the Proposed License Amendment Since the SVCs can control voltage supplied by the offsite sources to the Class 1E 4.16-kV busses, the addition of SVCs to the secondary circuits of the RAT and ERAT will ensure adequate voltage to Class IE plant loads during unit operation, shutdown, and emergency conditions. In this regard, the proposed amendment supports use of the SVCs and thus supports safe operation of the facility.
Each SVC has redundant protection subsystems that are designed to trip the SVC if an abnormal condition that could be caused by SVC failure is detected. This is important since abnormal conditions could potentially damage or disable Class 1E loads connected to the affected busses if the SVC is not removed from service. Since the SVC protection i system is relied upon to protect Class IE equipment, the addition of appropriate Technical Specifications requirements is intended to ensure that operability of the SVC protection systems is maintained. The requested license amendment will incorporate the desired Technical Specification requirements.
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Attachment 3 to U-602972 Page 2 of 3 Environmental Impacts of the Proposed Amendment Granting the license amendment would suppon use of the SVCs to increase the reliability of the offsite power system for CPS. In particular, this would support offsite power requirements for CPS in the event of a ,ccident, and therefore, would decrease the probability of a radiological release from CPS. Further, with respect to supporting operation of the facility, the amendment will reduce the potential for required shutdowns of the facility due to low voltage conditions that could require the offsite sources for the facility to be declared inoperable per the plant Technical Specifications. This reduces the probability of a plant transient that could result from a plant shutdown or repeated plant shutdowns.
With regard to potential non-radiological impacts, the proposed amendment would not affect plant operation except to support electrical power requirements for the facility.
Supporting electrical power requirements for the facility supports operation of the facility consistent with the requirements of the operating license. Apart from any radiological impacts, this may also minimize the potential for nonradiological effluents that could result from operation or recovery of the facility under abnormal or accident conditions. In addition, supporting continuous operation of the facility suppons grid voltage and minimizes the likelihood of power interruption to customers which can itself have adverse environmental and public safety impacts.
With further regard to non-radiological impacts, addition of the SVCs results in the addition of new electrical componems and small structures within the plant protected area.
Various systems or components associated with the SVCs utilize or contain chemical fluids or gases that may be considered from an environmental impact perspective.
However, the amounts or volumes of each are relatively small, and the chemicals are either relatively harmless or are normally contained. For example, the cooling system for the SVCs, which utilizes a mixture of de-ionized water and glycol, is self contained. For fire l protection, a water mist fire protection system is used to protect the SVCs. Maximum discharge per release via a compressed nitrogen gas cylinder is 15') liters. The SVC control system is fire protected via a gaseous flooding system designed to NFPA Standard 2001. The gas used, FM-200 (Heptafluoropropane), is an environmentally acceptable replacement for Halon 1301. Less than 20 pounds is utilized for the system. With respect to the capacitors used in the SVCs, the capacitors are of a film design with non-PCB diaelectric fluid or impregnate. Finally, the main circuit breakers for the SVCs contain SF6 which is already used in 345-kV breakers within the switchyard at CPS. In totaj, IP does not believe that these SVC features constitute a significant hazard or impact to the environment, particularly in light of the fact that the SVCs are within the protected area of the facility, and as such, should have little or no impact to the surrounding area.
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to U-602972 Page 3 of 3 Alternative to the Proposed Action Given that the proposed amendment supports plant operation, there are no significant environmental effects associated with the proposed amendment beyond those attributed to operation of the facility, Other alternatives (except to not allow operation of the facility) l would have no greater, favorable environmental impact. Other alternatives include significant changes to the offsite transmission system or the installation of new, additional generating capacity to locally support voltage. These options, which were rejected, would
! involve more extensive environmental impacts than the modifications that were selected to i be done. Thus, the principal alternative would be to deny the requested amendment, l which would effectively preclude operation of the facility.
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Alternative Use of Resources The proposed amendment involves the use of human resources and materials of a type already utilized for the facility (i.e., onsite). With respect to natural resources and the environment, the proposed change involves minimal additional impact. As noted above, alternatives to the selected modifications associated with the proposed amendment would likely involve a more extensive impact to the environment and would likely involve a more j extensive use of resources (materials or fuel, for example).
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Attachment 4 to U-602972 LS-98-001 Page 1 of 3 Proposed (New) Pages for the CPS Technical Specifications
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