ML20044B214

Withdraws 891003 Amend Request to Allow Sufficient Time to Reevaluate Technical Position & Develop Addl Technical Justification

ML20044B214
Person / Time
Site:	Byron, Braidwood
Issue date:	07/11/1990
From:	Hunsader S COMMONWEALTH EDISON CO.
To:	Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9007180124
Download: ML20044B214 (2)

Text

{{#Wiki_filter:_ ] h Commonwealth Edison "I ' 1400 Opus Place \\ / Donners Gr:ve, Illinois 60515 ( \\v/ t' July 11, 1990 1 Dr. Thomas E. Murley Office of Nuclear Reactor Regulation i U.S. Nuclear Regulatory Commission Washington, DC 20555 t Attn: Document Control Desk t

Subject:

Byron Station Units 1 and 2 4 Braidwood Station Units 1 and 2 Supplement to Application for Amendment to Facility Operating Licenses NI'F-37, NPF-66, NPF-72 and NPF-77, i Appendix A, Technical Specifications NRC Docket Nos 50-454, 50-455, 50-4M_and._5.Ihk5L

References:

(a) October 3, 1989 R.A. Chrzanowski letter to T.E. Murley

Dear Dr. Murley:

In reference (a) pursuant to 10 CFR 50.90, Commonwealth Edison (Edison) proposed to amend Appendix A Technical Specifications, of Facility Operating Licenses NPF-37. NPF-66, NPF-72 and NPF-77. The proposed amendment requested a change to Technical Specification 3/4.8.3.1 to allow one 120 VAC instrument bus to be energized from its associated constant voltage transformer for a period of up to 72 hours instead of for a period of up to 24 hours, as currently specified in the Byron /Braidwood Technical Specifications. Recent dialogue with the NRC staff has indicated that additional information is necessary to support the technical justification for the amendment request. As a result, Edison is withdrawing this request for an amendment to allow sufficient time to re-evaluate our technical position and to develop additional technical justification. Upon completion of thesc - activitities, Edison will make an appropriate amendment application. Edison is notifying the State of Illinois of this withdrawing of an appilcation for amendment by transmitting n copy of this letter and its attachments to the designoted Stat e Of f icini. l l

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f' 9007180124 900711 0 PDR ADOCK 05000454 i { p PDC f l

/>,,- j,' t i F r. a; Dr. Th mas E. Murley July 11, 1990 .A copy of reference'(a) is enclosed. Please direct any questions you-may have concerning this'oubmittal to'this office. i. Very truly yours, E,; JC. f&J S.C. Hunsader-Ll Nuclear Licensing Administrator [o . /srm:1042T v. I-Enclosurest q h. s.u-m . Reference (a),' October 3, 1989 R.A. Chrzanowski letter to T.E. Murley. f' + ect Resident Inspector-Byron. k Resident Inspector-Braidwood T. Boyce-NRR-s L .S.P. Sands-NRR f 'W..Shafer-Region III [. .M.C. Parker-IDNS-O I, y 4 ?,', k ' d'. i i n p[ I 'f. 6 i

C:mm:nwealth Edison K s fs ' bt b Cruca;p =>$ 60093 0767 October 3, 1989 Dr. Thomas E. Hurley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Byron. Station Units 1 and 2 Braidwood Station Units I and 2 Application for Amendment to facility Operating Licenses NPF-37, NPF-66, NPF-72, and NPF-77 HRC_QocteLNoL__50-li4L45 Land-50-456/451

Dear Dr. Murley:

Pursuant to 10 CFR 50.90, Comonwealth Edtson proposes to amend Appendix A. Technical Specifications of Facility Operating Licenses NPF-37, NPF-66 NPF-72, and NPF-77. The proposed amendment requests changes to Specification 3/4.8.3.1, Onsite Power Distribution. The detailed description is contained in Attachment A. The revised Technical Specification pages are contained in Attachment B. The proposed changes have been reviewed and approved by both on-site and off-site review in accordance with Commonwealth Edison procedures. Commonwealth Edison has reviewed this propcsed amendment in accordance with 10 CFR 50.92(c) and has determined that no significant hazards consideration exists.- This evaluation is documented in Attachment C. Commonwealth Edison has evaluated the proposed amendment with the requirements of 10 CFR 51.21. Attachment D contains the corresponding Environmental Assessment Statement. Commonwealth Edison is notifying the State of Illinois of our application for this amendment by transmitting a copy of this letter and its attachments to the designated State Official. 0308T:1 ) T

~ l.:5I l ,1 :. '", I Or.'T.E. Hurley_ October 3,1989 i Please direct any questions regarding you may have this matter to this office. 4 l-Very truly yours, i kM R. A. hrzanowskt g Nuclear Licensing Administrator Attachments cc: Senior Resident Inspector - Byron Senior Resident Inspector - Braldwood L.N. 01shan - Project Manager, NRR S. P. Sands - Project Manager, NRR Regional Administrator - Region III Office of Nuclear "acility Safety - IONS i ? 4 030BT:2

h, l 3 i LIIACHMf1La l 'l DEIAI1EQ_011CRlPl10N i IhlR0RiiCIl0N i The 3yron and Braldwood Stations Technical Specification 3/4.8.3.1 requires tha' each 120 VAC instrument bus be energized from its associated inverter connected to its associated DC bus during operation in Modes 1, 2, 3, and 4. An act'on statement allows the instrument bus to be de-energized for a period of up t1 2 hours.and not energized from its associated Inverter connected to its associated DC bus for a period of up to 24 hours. Fallure to meet either of the action statement conditions would require the plant to be in bot standby within the next 6 hours and in cold shutdown within the following 30 hours. This attachment supports a proposed amendment to the Technical Specifications which would allow one 120 VAC instrument bus to be i energized from its associated constant voltage transformer for a period of up to 72 hours. The proposed amendment will: 1. Reduce the hesitancy to allow planned outages on Inverters for preventive maintenance to be performed due to the short 24 hour allowed out-of-service time currently permitted by Technical Specifications and. 2. Allow sufficient time to troubleshoot, repair, test, tune, clean and inspect failed inverters before requiring a plant shutdown. BACEGRQUND The 120 VAC Instrumentation System supplies a-reliable source of regulated instrument and control power to equipment and systems which must remain in operation during a momentary or complete loss of AC power. These systems include the-Reactor Protection System, the ESF Actuation System, Process Instrumentation System, and rertain Safety Category II (non-safety related) loMs required to facilitate plant operation. Each of the Byron units has four 120 VAC Instrumentation busses, supplying one of the four Reactor Protection System channels, Each of the two 480 VAC ESF Divisions supplies two of the 120 VAC instrumentation busses. A 120 VAC Instrumentation bus is capable of receiving power from its 480 VAC ESF busses by two means:

1) from its associated static inverter or 2) from its associated 480/120 Volt self-regulating constant voltage transformer.

The inverter and transformer feeder breakers are mechanically interlocked to prevent their simultaneous closure and subsequent paralleling of the inverter and the transformer power feeds. The inverter power supply frequency is much more regulated (60 Hz

0. 57. ) than the constant 4

voltage transformer output and parallel operation might cause overheating of the inverter. The inverter is the normal and preferred source while the l constant voltage transformer serves as a backup source when the inverter is L out-of-service for maintenance or repair. l 0308T:3

4 I The 7.5 KVA inverter provides additional redundancy in that it is i capable of being powered from either the 480 VAC ESF bus or from a 125 VDC control power battery bus. The inverter produces a single phase, 60 Hz, 118 VAC output. The 480 VAC ESF bus is the normal source of power to the inverter l with automatic transfer to the 125 VDC bus if the AC input fails. The three-phase, 480 VAC input to the inverter is first transformed then rectif!*d to a DC output voltage. DC output voltage is adjusted so that it doei not exceed 140 VAC and is not less than the battery voltage. A blocking diode is installed in the battery input circuit. This blocking diode is normally reverse-blased, thus blocking the DC bus input. If the AC power supply falls, the diode will conduct and automatically "bumplessly" transfer battery power-to supply the instrument bus through the inverter. The 10 KVA constant voltage transformer is classified as Safety Category I (Class IE) and is powered from its associated 480 VAC ESF bus. The transformer produces a single-phase, 60 Hz, 120 VAC output. The transformer is the controlled ferro-resonant type and provides output voltage regulation to within 32% with +10% to -15% input variation. The constant voltage transformer is a reliable piece of equipment and no failures have occurred on Byron Units I and 2 based on a review of the Nuclear Plant Reliability Data System. In addition, a review of the Total Job Hanagement data base identified that no maintenance activities have been required on these transformers as a result of any work requests. A sketch of the bus arrangements is provided in Addendum 1. Plant Response to a Complete Loss of an Instrument Bus The complete loss of power to a 120 VAC instrument bus can interrupt the following safety related and non-safety related power supplies depending on the particular bus de-energized: 3 SAFr Y-RELATED i 1. NIS Channel Control Power 2, NIS Channel Instrument Power 3. Auxiliary Safeguards Relay. Power 4. Safeguard Test Relay Power 5. Reactor Coolant Loop Stop Valve Protection System Power 6. Solid State Protection System Train "A" Input Channel Power 7. Solid State Protection System Train "B" Input Channel Power 8. ESF Sequencing and Actuation Cabinet Power L 9. Main Control Board ESF Power Supply l 10, Process Instrumentation and Control Rack Channel Power Supply 11. Solid State Protection System Output Relay Power i l 0308T:4 L 1 4

4 NON-SAFETY RELAJIQ 12. Process Instrumentation and Control Rock Channel Power $upply

13. Main Control Board Instrument Channel Power Supply It should be noted that an automatic transfer to reserve power separate from the 120 VAC instrument busses is provided for the process instrumentation and control cabinets. identified in items 10 and 12 above.

Therefore on a loss of instrument bus power it is highly unlikely that the process I & C cabinets would be de-energized. Additionally, the operator is required by procedure to select alternate control channels or defeat inoperable control channels and is provided with Abnormal Operating Procedures to identify which process instruments have been lost when a particular instrument bus is de-energized. It should be noted that for each of the two ESF Divisions only one of the two 120 VAC Instrument busses on that division supplies power to its dedicated train Solid State Protection System (SSPS) output relay cabinet. As such for Division 11 (21), only 120 VAC instrument bus 111 (211) supplies power to SSPS Train A output relay cabinets while bus 113.(213) does not. Similarly, for Division 12 (22), only 120 VAC instrument bus 114 (214) supplies power to SSPS Train B output relay cabinets while bus 112 (212) does not. With instrument bus 111 (114' (211 (214)) on the Constant Voltage Transformer (CVT) and with a loss of offsite power concurrent with an SI signal the shutdown sequencer and safety loads would sequence on the 4KV bus l per design. There would be no re 9ction in the level of safety provided by an instrument bus fed from either its associated instrument inverter or from its associated CVT. No single failure during a loss of offsite AC power would prevent the automatic actuation of at least one division of safety, should it .i be required. This is because of the inherent system design. When instrument bus 111 (114) [211 (214)] is deenergized the SSPS would process the SI signal up'to the master relays. When the 4KV ESF bus 141 (142) [241 (242)] is reenergized the slave relays associated with the SI signal would be energized. The sequencing cabinet does not start sequencing uatil the undervoltage relay for the 4KV ESF bus has reset. The time for.this reset is about 1.8 seconds. The average time for the SSPS to process an ESF signal is less than 0.5 seconds. Thus the automatic ESF System for the associated 4KV ESF bus will respond as designed under loss of offsite power with an SI signal upon the diesel generator (DG) for the associated 4KV ESF bus reaching rated speed and voltage at which time the DG feed breaker to the associated 4KV ESF bus would close and the loads would sequence on the 4KV ESF bus. The bus feed breaker from the 4KV ESF bus to the 480 VAC bus which feeds the CVT and the breaker from the 480 VAC bus to the CVT does not open on undervoltage. Thus the instrument bus would be reenergized when the DG feed breaker closes on the 4KV bus. Some control board indication would be lost until the DG feed i breaker closed on the bus, but indication of plant parameters would be l provided by the other instrument busses on their respective 125 VDC battery source through the inverter. There would be no delay in providing any L protection required due to the instrument bus being fed from the CVT. 0308T:S L

F 1 l 3 ) l All ESF functions would respond as required on a loss of offsite AC If the Diesel Generator on the division not affected by the Inverter outage I were to fall. Abnormal Operating Procedure 1/2 BOA ELEC-2, LOSS OF INSTRUMENT BUS provides the symptoms and required operator actions for a loss of any of the four 120 VAC instrument busses. While the procedure is written based on the l loss of an instrument bus while on its associated inverter, it would also be applicable for loss of the bus while on the constant voltar itesformer. The control room indications following a ims sf .n M: % /Snt bus would include one or more of the following: l 1. Possible Reactor Trip and/or Safety Injection from % m aes made up by tripped bistables. 2. Tripped status lights for a particular channel indicate a tripped condittor. 3. Abnormal main control board indications fed from the de-energized i instrument bus. 4. Various main control board alarms. 5. Loss of instrument and control power to the channel of nuclear instrumentation fed from the de-energized bus. 6. General Warning alarm from the Solid State Protection. System Cabinet A or B. Required operator actions consist of: 1. Check Rod Control System in manual.

2. -Check TAVE - TREF deviation is stable and within l'F.

3. Check that the following instrument control channels are operable: Pressurizer pressure Pressurizer level Steam flow Steam generator level Feedwater flow Turbine Impulse Pressure aT l-0308T:6 i i

l. 4. Determine which instrument bus is de-energized by verifying instrument and control power is available to all NI$. 5. Restore power to affected instrv.wnt bus (ses) by checking inverter amps and voltage, verifying supply and individual load breakers are closed and transferring to the constant voltage transformer if necessary. 6. Check that the instrument bus (ses) is(are) reenergized and available to all NIS. Onsite Power Distributton Technical Specifications The basis for the operability of the AC and DC power sources and associated distribution systems during operation ensures that sufficient electrical power will be available to supply safety related equipment required for: 1) the safe shutdown of the facility, and 2) the mitigation and control of accident conditions within the facility. The minimum specified AC and DC power sources and distribution systems satisfy the requirements of General Design Criteria 17 of Appendix A to 10CFR part 50. As mentioned above, Technical Specifications currently limit operation with an inverter out-of-service to 24 hours during which time the 120 VAC instrument bus is energized by its constant voltage transformer. If during this time period transformer power becomes unavailable for any reason, one Reactor Protection System channel is lost and one train of ESF Protection may be lost and.the degree of protection redundancy is potentially reduced. The Technical Specification Bases do not present a discussion of the basis for the allowable out-of-service times for the power distribution i system but does state that the AC and DC source allowable out-of-service times for the power sources are based on Regulatory Guide 1.93, " Availability of Electrical Power Sources", December 1974 For the lack of a more definitive guidance, the regulatory position as presented in Regulatory Guide 1.93 will be used as a reference for extending the allowable out-of-service time with an inverter out-of-service from 24 to 72 hours during which time the 120 VAC instrument bus is energized by the constant voltage transformer. Regulatory Guide 1.93 states that whenever the Technical -Specifications allow power operation to continue with less than the required number of electrical power sources, such continued power operation should be contingent on: a) an immediate vertftcation of the availability of the remaining sources, b) reevaluation of the availability of the remaining diesel-generators at a time interval not to exceed eight hours, c) verification that required maintenance activities do not further degrade the power system or in any way p ant safety, and d) compliance with the additional conditions stipulated for each specified degradation level. 0308T:7 4 i

-) Since Regulatory Guide 1.93 was intended to provide a basis for the - allowable out-of-service times for power sources to the 4 Kv ESF busses strict application of items a) through d) above is not deemed appropriate for power sources.to the 120 VAC instrument busses. Each item and its application to the extenston of the action time allowed for an A.C. Instrument bus to be energized from a source other than from the inverter connected to its associated D.C. Bus is commented on below. Item a) an immediate verification of the availability of the remaining sources. There are two sources under consideration:

1) the sources supplying the instrument bus Dr Lentinizid from its associated inverter and 2) the sources supplying the three instrument busses gningittd from their associated inverters.

L ror the instrument bus not_fDtI9tZid from its inverter the sources under consideration are the supplies to its associated Division 4 KV ESF bus and 125 VDC battery. Since the battery is not capable of supplying the instrument bus via the constant voltage transformer, the remaining sources are the associated diesel generator and either units System Auxillary. Transformer (SAT) as prescribed in specification 3.8.1.1. Surveillance Requirement 4.8.3.1.2 has been added to meet the intent of this item. 4.8.3.2 The 480-Volt A.C. ESF bus energizing the affected 120-Volt A.C. instrument bus shall be determined energized in the required manner by verifying correct breaker alignment and indicated voltage on the associated 4160-Volt and 480-Volt busses. For the three Instrument busses tuttg1Ztd from their associated inverters the sources under consideration are the supplies to their associated 4 KV ESF bus and 125 VDC battery. Surveillance Requirement 4.8.3.1.3 has been added to meet the intent of this item, 4.8.3.3 The three unaffected 120-Volt A.C. Instrument busses shall be determined energized from an OPERABLE inverter by verifying correct breaker alignment and indicated voltage on the associated ESF and 125-Volt D.C. busses. The current action statement does not require immediate verification of the availability of the remainlag sources, but allows 24 hours of operation on the constant voltage transformer. This is consistent with NUREG-0452 and in general with all stations whose Technical Specifications are based on NUREG-0452. Rev. 4 and later. Ir.sertion of the Regulatory Guide 1.93 requirement to immediately verify the remaining sources would make the action statement more restrictive than the current action statement since any variation in breaker alignment or indicated voltage on z' associated 480-Volt and 4 Kv busses could immediately force the plant into shutdown via specification 3.0.3. E 0308T:8

P Based on the above the action statement has been modified to allow 72 hours of operation with the instrument bus not energized from its associated inverter. Verification of correct breaker alignment and.

Indicated voltage would be required within 24 hours and at least once per 8 hours thereafter. The choice of the 24 hours is consistent with the current industry practice of allowing 24 hours of operation on the constant voltage transformer without verification of sources and consistent with the Regulatory Guide of requiring-immediate verification (after the 24 hour period) for the extension period. Item b)-re-evaluation of the availability of the remaining diesel-generators at a tiue interval not to exceed eight hours. The proposed amendment request does not specifically require thatithe. availability of the remaining diesel-generators.be reevaluated, but does require. verification by Surve111ances.4.8.3.1.2.and 4.8.3.1.3 of correct breaker alignment and indicated voltage on the 4 Kv ESF busses. The term verify as used in this context means to administratively check by examining logs or other information to determine if certain components-are out-of-service for: maintenance or other reasons and this would include the -diesel generators. It is felt that these additional surveillances,'and-with the'requiremists of ACTION C of specification'3.8.1.1 if one. diesel-generator were inocerable,-are sufficient to meet the intent of this item. Item c) verification'that required maintenance activities do not further degrade the power system or in any way. plant safety. 4 This;1 tem will be covered by the performance ~of. surveillance 4.8.3.1.2' &nd 4.8.3.1.3 above. Additionally, the station out-of-service procedure BAC-330-1, Revision 4, dated. December:20,1989 states the~ following: a - 1.. ' Prior to taking a Technical Specification required component 005,Dthe< redundant train will be verified'operableL(item 2.a page13)' The Shift r gineer or-SRO licensed assistant determines that the' 2: a redundant train of Safety Related equipment is operable by; checking the Haster-Out-of-Service board,' prior to approving an outage 1on Safety:Related equipment. E, Item d) compilance with the additional conditions stipulated for each- \\ D specified degradation 11evel. There it only one~ degradation levei-under consideration, the instrument j bus supp1ted for a period of time (72 hours) by its constant voltage ?> transformer instead of the inverter. Additional considerations are jy, provided by the modified action statement and'the addition of surveillance u requirements. at 0308Tro u t i

The proposed Technical Specift:ation changes are provided in Attachment B. The proposed amendment will reduce the time pressures to complete repairs or limit opportunities for preventive maintenance on the inverters currently felt as a result of the 24 hour limit. While a quantitative assessment of plant availability has not been conducted it is felt that it is gnod engineering practice to provide sufficient time for the conduct of both these repair / maintenance activities. The current 24 hour limit is insufficient when considering that: 1. It takes several hours to complete the required paperwork and equipment tag out process prior to any work being started. 2. Troubleshooting the inverters has historically taken 10 to 15 hours depending on the complexity of the circuit that has failed. 3. Once the failed item (5 determined, a paper work change with accompanying repair work instructions and signatures mutt be obtained a prior to repair. 4. Following repair the inverter must be temporarily energized and loaded to verify proper operation and tuning. 5. It can take several hours to clear the equipment tags and complete the required paperwork to return the inverter to service. The total time for the above process outline for a corrective action is in the range of 15 to 21 hours depending on the complexity of the failure. This does not include any additional time for preventive maintenance actions such as tuning the ferro-resonant transformer, capacitor change outs, cleaning the inventer, as.ertation of electrical connection tightness and new part " burn in" time. The inverter units need Deriodic inspections for dust and dirt buildup on electrical circuit components and particularly on capacitors located in the ferro-resonant transformer. This req"' s that the normal paperwork and equipment tag out process described above be completed in order to disassemble and access the ferrs resonant transformer for cleaning. With the 24 hour time clock operating, repair of all but minor problems would be limited. It sho 'd be noted that the Regulatory Guide does not specify a particular time limit for allowed out-of-service time for this bus. Additionally, the instrument cLs will be energized during this period from a very reliable 480 VAC ESF bus with in;reased surveillances on both the affected and unaffected busses. For these reasons and those discussed above, we believe it is acceptable to a' low an instrument bus to be supplied via the 10 rVA constant voltage transfo;ver for up to 72 hours to allow for suffi: lent time for the performance of both ccmprehensive repair and maintenance actions in accordance with good engineering practices. l l 0308T:10 1

g m ~ F i. e ...,z e. n ry i e i 611ACHMENT B PROPOSED CHANGES TO APPENDIX A. I r IIQlRCAL.SRECIFTCATIONS OF-FACILITY OP_ERATING LLCENSE NPE-37. NPF-66. NPF-72'AND NPF-77 4 T

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4 i BYRON SRIDH000-Revised Pages: 3/4 8-14 3/4 8-14 3/4 B-15 3/4 8-15 j i ,n t< i h' i

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)' 4 I ELECT'ICAL POWER SYSTEMS. R 3/4.8.3-ONSITE POWER DISTRIBUTION OPERATING-LIMITING CONDITION FOR OPERATION 3.8.3.1 The following electrica'l busses shall be energized in the specified manner for the applicable unit: a. A.C. ESF. Busses consisting of: UNIT 1 UNIT 2 s a Division 11 Division 21 U 1) 4160-Volt Bus 141, 1) 4160-Volt Bus 241 l 2) 480-Volt Bus 131X, and 2) 480-Volt Bus 231X, and: 1 3) 480-Volt Bus 131Z. 3) 480-Volt, Bus 231Z. b. A.C. ESF Busses consisting of: UNIT'1 UNIT 2 Division.12 Division 22 1) 4160-Volt Bus 142 1) 4160-Volt Bus 242 2) -480-Volt' Bus 132K, and 2)- 4CO-Volt Bus 232X, and 3) 480-Volt Bus 1322, 3) 480-Volt Bus 232Z. 120-Volt A.C. Instrument Bus 111 for Unit 1 (Bus 211 for Unit 2) c. energized from its associated inverter connected to D.C. Bus 111 for Unit 1 (Bus 211 for Unit 2), d. 120-Volt A.C. Instrument Bus 113 for Unit 1 (Bus 213 for Onit 2). energized from its associated inverter connected to D.C. Bus-111 for Unit 1 (Bus 211 for Unit 2), + 120-Volt A.C. Instrument Bus 112 for Unit 1 (Bus 212 for Unit 2) c e. l- ' energized-from its associated inverter connected to 0.C. Bus 112 for Unit 1 (Bus 212 for. Unit 2), and f. 120-Volt A.C. Instrument Bus 114 for Unit 1 (Bus'214.for Unit'2) ' energized from its associated inverter connected to D.C. Bus 112 for L Unit 1 (Bus 212 for Unit 2). o lc APPLICABILITY: M0f'E. 1, 2, 3, and 4. it; ACTION: [ With'one of the required divisions of A.C. ESF busses notifully a. H energized, reenergize the division within 8 hours or be in at'least I L: HOT STANDBY within the next 6 hours and-in COLD SHUTDOWN ^within the following'30 hours. b. -With'one.A.C. instrument bus either not energized from its associated ) E inverter, or.with the inverter not connected to its associated 0.C. bus:

1) reenergize the A.C. instrument bus within 2 hours or be.in

(. at least HOT STANOBY within the next 6 hours and in COLD SHUTDOWN-1 L, within the following 30 hours and 2)-reenergize the A.C. instrument - bus from its -associated inverter connected to its associated 0.C. bus s l' withia f hoursaor be in at least HOT STANDBY within the'next'6 hours L and in' COLD SHUT 00WC within the following'30 hours. Q ad winansfraie. cvinga.ay of yfe tep.,ht A d. utess wleu 24 Lmars and et jerst mee per e Awes BYRON - UNITS 1 L 2 3/4 8-14 f4< reader hy federe.f spee4ca M_r i; 4' t. 3 /. 2 o., < 4' s. 3. /. 3, J i@ T x

8 .Q ELECTRICAL POWER SYSTEMS r SURVEIL 1ANCE REQUIREMENTS 4.8.3.1.1The st ecified busses shall be determined energized in he required manner at least once per 7 days by verifying correct breaker alignment and I indicated voltage on the ESF busses. i r/e a c 6 d 12 o e ll A. C. 4 6.3 L 2 h g. Y 6 0 voit A c, csr sus gne ;,, 5 nil be 6 & % nec/ e m,zeg in 4/,e regy,r'ed' men w by ,ksitumenb bo.5 I 9 co te d bwbr* + abjdaed an d inc6 ca.bd g /t'aye on t'fe casa c.,a.ggel t p'er r y,go voti and 4'80 @ t f-basse5. v,ree una.t'OcT.ed tzo-vor A. C. inniumpst'.6usses JAa/t Q y 3,7 3 yu re<#yidf "" rex g, g,,as aeiy.ias % a<, c h e & E d eu r 6 y i ud O

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y 1 l m ELECTRICAL POWER SYSTEMS o =3/4.B.3 'ONSITE POWER DISTRIBUTION OPERATING LIMITING CONDITION FOR OPERATION i '3.B.3.1. The following electrical busse shall be energized in the specified-o ? manner for the_ appitcable unit: s t a '. A.C. ESF Busses consisting of: ~l UNIT 1 UNIT 2 Division n Division 21 1) 4160-Volt' Bus 141, 1) 4160-Volt Bus 241-1 2) 480-Volt Bus 131X. 2) 480-Volt Bus 231X. 'i b. - A.C; ESF Busses consisting of: UNIT 1 UNIT 2 i Division 12 Division 22 1) 4160-Volt Bus 142 1) 4160-Volt Bus 242' 2) 480-Volt Bus 132X. 2) 480-Volt Bus'232X. 120-Volt A.C. Instrument Bus in for Unit 1-(Bus 211 for Unit 2) c. energized from its associated inverter connected to D.C. Bus 111 for-Unit l'(Bus 2n _for Unit 2), d. 120-Volt A.C.-Instrument Bus 113 for Unit l'(Bus 213'for Unit 2) energized from its associated inverter connected to D.C. Bus n1 for - R Unit 1 (Bus 2P for Unit 2), 'e. 120-Volt A.C. Instrument Bus 112'for Unit 1 (Bus 212 for Unit 2) energized free ;its associated inverter connected to D.C. Bus'112 for' Unit 1 (Bus'212 for Unit 2), and. f. 120-Volt A.C. Instrument Bus 114 for Unit 1 (Bus 214 for Unit 2) energized from its associated inverter connected to D.C. Bus n2 for Unit 1 (Bus 212 for Unit 2). APPLICABILITY: MDDES l', 2, 3, and 4. ACTION: -.With one of the required divisions of A.C. ESF busses not fully a. energized, reenergize the division within 8-hours or be in at'least-- HOT STANOBY within the next 6 hours and in COLD SHUTDOWN within the following 30 hours. e ' b. With one A.C. instrument bus either not energized from its associated inverter, or with the' inverter not connected to its associated D.C.. bus:

1) reenergize the A.C. instrument-bus within 2 hours or be in at least HOT STANDBY within the next 6 hours and in. COLD SHUTDOWN within the following 30 hours, and 2) reenergize the A.C. instrinnent bus from its associated inverter connected to its associhted 0.C. bus 1

within hours o e in at least HOT STANDBY within the-next 6 hours and-in OLD SHU OWN within the following 30 hours. 7E'

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d .e 8 ATTACHMENT C t .4 i fyAL'JATION OF SIGNIFICANT HAZARD CONSIDERATIONS .r . Commonwealth Edison has evaluated this proposed amendment and has determined that it does not involve a significant hazards consideration. 'According to 10;CFR 50.92(c), a proposed amendment to an operating Ilcense ,1 involves no significant hazards considerations.lf. operation of the facility in 'i 'accordance with the proposed amendment would not: L '). Involve a significant increase in the probability or consequences of an 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. T The proposed amendment requests a change which involves revising Technical Specification 3/4.8.3.1 to increase the allowed action time from 24 hours to 72 hours for an AC instrument bus to be disconnected from its associated inverter. Two additional surveillance requirements (4.8.3.1.2 and 4.8.3.1.3) are proposed. Surveillance 4.8.3.1.2 will verify that the 480 VAC ESF_ bus supplying the constant voltage transformer is energized in the required manner within 24 hours and at least once.per 8 hours thereafter. ' Surveillance 4.8.3.1.3 wlll verify that the other three-instrument busses are energized.from-an OPERABLE' inverter within the same time period. :This amendment is requested to allow sufficient time to fully troubleshoot-and . repair failed inverters and to provide sufficient-time for preventive . maintenance to be performed on operable inverters while in modes 1-through.4. g The proposed change does not involve a significant increase in~the - probability or consequences of an accident previously evaluated. Increasing the action time to allow one 120 VAC-instrument bus to be energized from its associated constant voltage transformer from 24 hours to 72 -hours /does'not significantly increase the probability of an accident previously evaluated. The loss of a single 120 VAC instrument bus is not in itself~an Linitiating event in any of the accidents presented in Chapter 15 of the:FSAR. . Hith one of the instrument busses on its constant voltage transformer instead of.its associated inverter there is some loss of redundancy.in bus pcwer 1 supplies due to tile loss of feed.from the inverter to the 125V DC bus. This loss of redundancy may result in an increased probability of a spurious reactor trip and/or safety injection, and loss of one train of ESF output relays. 'It is felt that this increase is not significant due to the following: 0308T:12

~ L 1 , o e e 1. The 480 VAC ESF bus is a very reliable source of power to the constant voltage transformers._ The 480 VAC ESF bus receives power from the 4.16kV ESF bus which in turn is capable of receiving power from the Unit-Auxillary Transformer-(UAT), Station Auxillary Transformer (SAT), the l emergency diesel generator and the SAT of the opposite unit. 2. The constant voltage transformer is a reliable t..i.e of equipment classified as Safety Category I (Class lE) and is required for safe- + shutdown..The failure probability of the constant voltage transformer, while not quantified, is considered to be small. This is substantiated _.by the fact that no failures have occurred on any of the sixteen constant-r voltage transformers installed o-Byron and Braidwood Units 1 and 2. _This was determined based on a review of the Nuclear Plant' Reliability Data System. 3. Two surveillances, 4.8.3.1.2 and 4.8.3.1.3, have been proposed to ensure the reliability of the.three unaffected instrument busses and the Instrument bus on'the constant' voltage transformer. Also, it should be noted that the Allowable Outage Time is only being increased when one redundant power supply to an instrume,1t bus is out-of-service. There are three additional instament busses (while not totally t redundant they have several overlapping cap' abilities) that would remain operable in accordance with Specification 3.8.3.1. Increasing the' action time to allow one 120 VAC instrument bus to be energized from its associated constant voltage transformer from 24 hours to 72 - hours does not'significantly~ increase the consequences of an-accident previously evaluated. The current Technical Specifications (3/4.8.3.1) and , the FSAR (Section 15.0.1.1) allow operation with the inverter out-of-service for 24 hours. Extending this period to 72 hours will not alter the plant response _to a loss of a 120 VAC instrumentibus should the constant voltage transformer fall while supplying the instrument bus. Off normal procedures - have already been developed and would be used by the operators to address this sli9ation.- The proposed change does not create the possibility.of a new or different kind of accident fiom any accident previously evaluated. Increasing the action time to allow one 120 VAC instrument bus to be one eJzed from its-associated constant voltage transformer from 24 hours to 72 hours wlli not create any new mod;s of plant operation beyond those.normally [ srmed. The proposed change does not involve a modification to currently installed systems or. equipment or require operation in a manner different from that currently allowed. The_ constant voltage transformer is designed for continuous operation so the extended action time is within design limitations. R M, 0308T:ll m /: {

-l y..'.. t. w The change is administrative in nature end as such it has no: impact' on.the accident analysis-from the standpoint of the possibility of creating a. new or different kind of accident from any accident previously evaluated. The proposed change does not involve a significant reduction:in a margin of safety. p Previously evaluated accidents demonstrate margins of safety. These! accident analyses are based on the availability of a minimum set of safety equipment and do not take into account allowable outage times for_ equipment. Therefore, there is no margin of safety associated with allowable' outage tines, i y

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ATTACHMENT D r-ENVIRONMENTAL ASSESf81HI Commo.iwealth Edison has evaluated the proposed amendment-against the. criteria for and identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CF3 51.21. It has been-determined that the proposed changes meet the criteria'for'a categorical exclusion as provided for under 10 CFR 51.22(c)(9) and (10). 'Following is a. discussion of the changes and how they meet the criteria _for categorical i exclusion. . The change to Specification 3/4.8.3.1 Increases the action time i allowed for an A.C. Instrument bus to be energized from a source other than' from the' inverter connected to its associated D.C. bus from 74 hours to 72 hours. Two additional surveillances 4.8.3.1.2 and 4.8.3.1.3, have been added for verification of energization of the affected instrument bus from the 480 VAC bus supplying its constant voltage transfer and verification of energiza-tion of the three-unaffected busses from their inverters, respectively. This does.not involve a change in the use of a facility component located in the restricted area. The preceding change does not involve.a significant* hazards consideration as-discussed in-Attachment C of this letter. Also there is no l

significant change'in the types or significant increase in the amounts of:any

effluents'that may be released offsite'since this change-does'not affect the generation of any radioactive effluents nor does.it affect any of the permitted release paths.

Finally, the change does not involve'a'significant i increase in individual or cumulative occupational radiation exposure. Therefore, this-change meets the categorical exclusion permitted by 10 CFR ~51.22(c)(9), L i L 1 l-I h- -0308T:15

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