IR 05000277/1987030
| ML20245H866 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/26/1989 |
| From: | Martin T, Strosnider J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Corbin McNeil PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 8905030556 | |
| Download: ML20245H866 (2) | |
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APR 2 6.1989
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Docket Nos'. 50-277' 50-278' Philadelphia Electric Company ATTN: Mr. C. A. McNeill' Executive Vice Presiaent-Nuclear Correspondence Control Desk-P. 0.' Box 7520 Philadelphia, Pennsylvania 19101 Gentlemen: Subject: . Inspection No. 50-277/87-30 and 50-278/87-30 This refers to your. letter dated March 23, 1939, in response to our letter dated December 13, 1988.
Thank you for informing us of the corrective and preventive actions documented in:your letter. These actions will be examined during a future' inspection of '+ your. licensed program.
Your cooperation with us is appreciated.
Sincerely, Original Signed By: Jack R. Strosnider
Thomas T. Martin, Director Division of Reactor Safety cc: John S. Kemper, Sr., Senior Vice President-Nuclear J.-W. Gallagher, Vice President, Nuclear Services E. C. Kistner, Chairman, Nuclear Review Board Dickinson H. Smith, Vice President, Peach Bottom Atomic Power Station Jack Urban, General Manager, Fuels Department, Delmarva Power & Light Co.
~ John F. Franz, Plant Manager, Peach Bottom Atomic Power Station
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Troy B. Conner, Jr. , Esquire
- W. H. Hirst,' Director, Joint Generation Projects Department, Atlantic Electric L Bryan W. Gorman,' Manager, External Affairs l Eugene J. Bradley, Esquire, Assistant General Counsel (Without Report)
Rayraond L. Hovis, Esquire Thomas Magette, Power Plant'31 ting, Nuclear Evaluations EE W. M. Alden Director, Licensing Section s 'Dorf s .Pouls,en Secretary of Harford County Cour,cil i Public Docunent Room (PDR) i
' 'Lecal Public Document Room (LPDP.)
< . Nuclear l Safety Inforn ation Center (NSIC) NRC Pesident Inspector E Commonwealth of Pennsylvania 0FFICIAL RECORD COPY RL PB 87-30 - 0001.0.0 1 030Sf6Ap%(L 89 @ 94 04/19/89 ( I 0Sw*t?? \ F o c-o - -_ -_ -- _- - - - _ - - ---- - --IBO) L
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i Ys i\. 10 CFR 50, Appendix R
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PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET
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P.O. BOX 8699 , c PHILADELPHIA A. PA.19101
{215) 841 4502-S. J, KOW A LSKI vics-PRgslogNT
.m.............. March 23,1989.
Dockets Nos. 50-277 50-278 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 SUBJECT: 10 CFR 50, Appendix R Multiple High Impedance Faults Peach Bottom Atomic Power Station Units 2 and 3 REFERENCE: 1) NRC Inspection Report Nos. 50-277/87-30; 50-278/87-30 Unresolved Item No. 3 2) June 15,1988 letter from E. P. Fogarty (PECo) to W. R.
Butler, (NRC)
Dear Sir:
This letter is in response to the December 19, 1988 letter from R. E. , Martin (NRC) to G. A. Hunger, Jr. , (PEco) concerning the potential for multiple high impedance faults during a postulated Appendix R fire at Peach Bottom Atomic Power Station. The NRC concluded that the Company's May 27, Flame : 1988 report titled, " Appendix R. Multiple High Impedance Cable Fault, Test Report" (transmitted with reference 2) did not provide sufficient justification to resolve this issue. This is a NRC Region I Unresolved Item (reference 1).
On March 15, 1989 representatives of the Company met with NRC representatives from the Nuclear Reactor Regulation staff and Region I staff in White Flint, MD and described the additional actions being taken to resolve the multiple high impedance faults issue. The Peach Bottom NRC Project Manager requested that the Company submit the information that was presented at the meeting. Accordingly, we have enclosed a written version of the , presentation and the hand-outs provided at the meeting.
If you have any questions or require additional information, please do not hesitate to contact us. Sincere y,
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cc: W. T. Russe]], Administrator, Region I, USNRC T. P. Johnson, USNRC Senior Resident Inspector R. E. Martin, USNRC Peach Bottom Project Manager A. Krasopoulos, USNRC Region I Inspector T. E. Magette, State of Mary 3and T. M. Gerusky, Commonwealth of Pennsylvania J. Urban, De3marva Power J. T. Boettger, Public Service Electric & Gao H. C. Schwemm, Atlantic E3 ectric-2- _ _ - _ _ _ _ _ - _ _ _ _ _ _ - - - _ _ _ _ _ - - _ _ _ - _ . .__.
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PBAPS Unit 2.& 3 HIF Rasolution
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a Docket Nos. 50-277/50-278 Page 1 of 12 APPENDII R HICH IMPEDANCE FAULT RESOLUTION , PECO PBAPS UNIT 2 & 3 Introduction Presentation Overview l The topics included in this presentation on high impedance faults are listed on the attached agenda. The background to be p ovided has a technical focus as related to high impedance faults. The guidance pertaining to high impedance faults is summarized per Generic Letter 86-10. The practical i implications of the guidance on addressing this issue will be discussed via an illustrative example of a power distribution syscem. The options that are available to address this issue will be summarized as described in the NRC letter to Philadelphia Electric Company (PECo) on this subject. The NRC letter, dated December 19, 1988, is a response to a previous submittal to the NRC on a fire test conducted by PECo.
The presentation on approach to resolution of this issue is broken into two parts. The first pertains to the technical work done with conservative assumptions to establish which power sources require restorative procedures.
Based on this first phase of work, a second phase technical review was conducted to determine that restorative procedures are technically justifiable where they are required based on the initial phase technical review. The procedures have been prepared and a discussion of procedure methodology is included. The completion of these first two phases including the implementation of the restorative procedures is presented as proposed closure for the iosue of high impedance faults as addressed in CL 86-10. An additional technical review, designated as Phase 3, which uses more ! realistic assumptions is in progress. This additional review is expected to eventually eliminate many of the restorative procedures being implemented based on the first two phases.
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Docket Nos. 50-277/50-278 Paga 2 of 12 A status of the technical reviews and implementation of restorative procedures and concluding remarks follow the discussion on " Approach."
Background Ceneric Letter 86-10 This generic letter contains the guidance on high impedance faults that is being enforced in NRC inspections of licensees' compliance with Appendix R safe shutdown requirements. In response to question 5.3.8 on rSe need to consider high impedance faults, the NRC response says that to meet the separation criteria of Appendix R, simultaneous high impedance faults should be considered for all associated circuits located in the fire area of concern. In response to this issue, PECo had previously conducted a flame test on a cable tray containing a number of cables. Each cable contained conductors, at least one of which was energized and at least one of which was connected to a ground. The flame was provided according to a standard IEEE specified source. The cables were subject to the flame until a fault of sufficient magnitude to blow the source fuses occurred. PEco believes ] the flame test was successful in demonstrating that cable faults when subjected to a fire are of limited energy content until they cascade to a , I low resistance fault of sufficient magnitude and blow the source fuse. l l Also, the duration of the high impedance fault is less than one minute. The test also demonstrates the time interval from flame application to the j I development of high impedance faults is a random distribution.
PEco submitted the flame test report to the NRC for review as alternate compliance with the guidance of CL 86-10. In response, the NRC was not able ) to conclude the results were necessarily applicable to an Appendix R fire since an Appendix R fire is undefined and the flame test source used by PECo was a standard specified source. The basis for extending the results to a general conclusion is that a flame source causes the initial degradation of insulation to occur; however, the fault current during the period of high impedance fault is transient. During this period the current ranges from very low values to high impedance values and is definitely not of a l l l _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . . . . _ _ _ _ _ _ . _ _ _ _ _
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Docket Nos. 50-277/50-278 Page 3 of 12 sustained steady state magnitude. Further the layering of cables in the test tray simulates a varying intensity of flame to the cable insulation.
In the interest of a timely resolution of this issue, PECo has elected to implement restorative procedures such that if multiple high impedance faults do cause a breaker to trip, plant operators would have procedural guidance on how to reset the source breaker and restore Safe Shutdown (SSD) loads such that the breaker would not re-trip due to multiple high impedance faults.
To demonstrate the application of the multiple high impedance fault concept, an illustrative example of a feeder breaker and bus are shown on page 4 of the handout. The example shows a feeder or source breaker from a 480 volt Load Center (LC) feeding power to a Motor Control Center (MCC). The MCC provides power to a number of loads through individual load breakers. The relative relationship of the LC breaker to MCC breakers is expressed as the
" upstream" breaker for the LC and " downstream" for the MCC breakers. A typical MCC would have 40 or more load breakers as compared to the illustrative example. Note that the load breakers on the MCC are labelled SSD for safe shutdown loads and NSSD for non-safe shutdown loads. SSD loads power equipment used for safe shutdown per the Appendix R requirements and are, therefore, protected or their cables are outside the fire area - which relies upon their use for safe shutdown. Non-safe shutdown loads are " associated" via the common electrical supply bus. The cables of NSSD loads are subject to the phenomenon of high impedance faults.
Trip coordination between the MCC breakers and LC breaker is achieved by raviewing the MCC load circuits and determining which one 9:ould result in the greatest fault current. Then the trip settings of that breaker and the LC breeker are reviewed to ensure the MCC breaker would trip before the upstream LC breaker. By ensuring the largest MCC load circuit fault is coordinated, all other MCC load circuits are also coordinated. The guidance of GL 86-10 imposes simultaneous high impedance faults on all the NSSD loads. The magnitude of fault current is such that each of the MCC NSSD breakers would not trip on the long time trip value. Typically this means thet for a 50 amp breaker, the fault current is just below 50 amps for a
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.Dockat Nos. 50-277/50-278 Page 4 of 12 sustained duration. The sum of the NSSD load high impedance faults must ,
then be compared to the long time trip rating of the upstream LC breaker to
' determine if coordination exists for the multiple high impedance fault condition.
The December 19, 1988 NRC letter to PECo on multiple high impedance faults contains a list of options commonly used by licensees to address high impedance faults. They are:
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' Written procedures for nanual clearing of faults
- Change breaker / fuse coordination
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Split common bus; add a parallel supply breaker
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Reroute or shield common bus load raceways
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Submit additional analysis using probabilistic arguments
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Approach Overview The approach PEco has used to implement restorative procedures is based on-three phases of work. The first phase determined if restorative procedures are required for each of the SSD load power sources based on very conservative screening assumptions. The results showed that restorative procedures are not required for a significant portion of the power sources.
The second phase was to verify that rectorar.ive procedures are technically supportable where they are required. In other words, can the operator l l successfully restore a bus by stripping the NSSD loads and re-energizing the j upstream breaker to only the SSD loads without the upstream be.t k er tripping h again. The arialysis methodology to support the use of restorative I i l procedures is also conservative. The results of this review conclude that j these procedures are technically acceptable for all power sources that _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ .
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PBAPS Unit 2 & 3 HIF Resolution
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Docket Nos. 50-277/50-278 Page 5 of 12 , require them. These procedures have been written and their implementation j satisfies the guidance of CL 86-10. For some fire areas several restorative procedures are applicable, however the probability of needing to implement restoration of any one of the power sources is low. The existing timelines for operator action contain conservativisms such that sufficient time would be available for operator response to high impedance faults should it be required. Portable lighting is available to the operators for their use.
The final phase of work which is in progress is a more detailed review of those power sources which require restorative procedures with more realistic data input. The objective of this analysis is to determine if these procedures are still required given this more realistic data. This effort will take approximately 2-3 months to complete and is expected to j significantly reduce the ultimate number of restorative procedures required.
Approach-Technical Review As previously discussed the analysis is being performed in three phases.
For each phase assumptions are made for the analysis performed by that phase.
The results of the analysis are compared to pass / fail criteria. The bases of the pass / fail criteria is the same for all of the phases.
Phase 1 (Reference page 8 of the handout) Phase 1 analysis is a gross screening of the power sources (switchgear, load centers, motor control centers, and panels) that support safe shutdown loads to evaluate the effects of the postulated high impedance fault (HIF) load on the power source circuit breaker or fuse. The screening included 69 power ' sources from the 4160-120 volt AC buses and 250/125 volt DC buses. These are all of the SSD power sources from Unit 2, Common and Unit 3.
l The Phase 1 assumptions are that all power bus circuits are routed through all fire areas of concern and all circuits experience a simultaneous high impedance fault. These assumptions are extremely conservative because , _ - _ _ _ _ _ _ _ _ - _ _ - - _ _ _ - _ _ _ _
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PBAPS Unit 2 & 3 HIF Resolution
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o Docket Nos. 50-277/50-278 Pege 6 of 12 realistically the power supply is centrally located with circuits routed radially in all directions, and for a fire area of concern, circuits required for a Safe Shutdown method for that area are protected.
The HIF current contribution for a circuit is the 1000 second current rating af the device (circuit breaker or fuse) protecting the circuit (e.g. 100 amp fuse =100 amp HIF current; 20 amp circuit breaker = 20 amp HIF current). 1 This value was used because it is the maximum current that a protection device can pass without incurring a trip. On a characteristic time-current curve for the protection device this is the point at which the curve becomes asymptotic.
Referencing page 10 of the handout, the representative MCC is shown with its supply breaker located in a LC. The MCC supports NSSD circuits and SSD required circuits. All of the circuits are contributing HIF current equal to the 1000 second current rating of the circuit breaker. To calculate the l sum total HIF current of the MCC, the circuit breaker ratings were added algebraically. For example if the MCC circuit breakers shown in the diagram were all 100 amp rated, the total HIF current load of the MCC would be 500 amps. The sum total value of the MCC current was then used for the pass / fail determination.
I The pass / fail criteria were applied in a two step analysis in that power
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supplies that failed Step 1 were further analyzed in Step 2. Step 1 was the comparison of the calculated current of a power supply to the 1000 second rating of the power supply protection (circuit breaker or fuse). The basis for using the 1000 second rating of the power supply protection is that this is the maximum amount of current that a protection device can pass without incurring a trip. On a time-current characteristic curve at this point the protection device curve beceraes asymptotic. If the sum total HIF current of the power supply was less then the 1000 second current rating of the source protection the power supply passed; therefore, no restorative procedure is required.0therwise, the analysis went to Step 2.
The Step 2 pass / fail criterion utilized the 60 cecond current rating of the j l source protection. The sum total HIP current was compared to the 60 second l l
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HIF Resolution i , Docket Nos. 50-277/50-278 Pege 7 of 12 current rating of the power supply protection. If the sum total current was less than the 60 second current rating of the power supply protection the
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power supply passed; therefore, no restorative procedure is required.
The basis for using the 60 second rating of the source protection was an analysis of the characteristic of the HIF as presented in the flame test report which was previously discussed in the Background section. The flame test demonstrated that after a HIF was initiated it increased in magnitude ' until it became a low impedance fault or short that would trip the circuit protection. The duration of the combination of faults from the initiation of the HIF to the circuit protection trip was between 8 seconds and 54 seconds with an average duration of 37 seconds. The 60 seconds used in the pass / fail criteria was the longest duration comprised of 54 seconds with an additional 10% conservatism added. The nature of the long time circuit protection is a direct relationship between time and current; less current requires more time to actuate the protection device to trip. As faults are cleared by circuit protection, the sum total of the power supply HIP current is reduced. Only a percentage reduction of the sum total fault current is required for the value to be less than the 1000 second current rating of the protection device.
Phase 2 (Reference page 11 of the handout) Phase 2 of the analyses was performed for those power supplies that did not pass the Phase 1 analyses. As previously discussed this phase is an analysis used to ensure that restorative procedures can be used.
Restorative procedures would be used to restore a bus (power supply) by stripping the NSSD loads and re-energizing the upstream (source) breaker to feed only the SSD loads.
In this phase the assumptions changed to include enay S$4 circuits; Scuever, the pass / fail criteria remained the same. The assumptions are that all SSD power bus circuits ary routed through all fire areas of concern end all ) i cirevits experience a simultaneoor high impedance fault. This assumption is ;
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conservative because not all SSD circuits are required for the sr.fe shutdown method required for a given fire area of concern. The safe shutdown method l
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' for a fire area is based on equipment and cables not located in the fire area of t.oncern. Also, the circuits required for the safe shutdown method
~in the fire area of concern are protected from a fire in that area.
Referencing page 12 of the handout the same MCC with the LC source breaker is illustrated, however, reflecting the new assumptions, the NSSD loads are removed. To calculate the sum total of HIF current of the power supply (NCC in the example illustrated) the 1000 second rating of the SSD circuits was added algebraically.
The same pass / fail criteria was used. In Step 1 the sum total power supply HIP current was compared to the 1000 second rating of the source protection (the LC circuit breaker in the example illustrated). If the sum total HIF current was less than the 1000 second rating of the source breaker, the power supply passed; otherwise the analysis went to Step 2. In Step 2 the sum total power supply HIF current was compared to the 60 second current rating of the source breaker. If the sum total HIF current was less than the 60 second current rating of the source breaker, the power supply passed.
Otherwise,the power supply failed the analysis.
Power supplies that passed the pass / fail criteria were deemed suitable for power restoration procedures. Of the thirty power supplies analyzed in this phase, one power supply, an MCC, did not meet the general pass / fail criteria. For this MCC a more detailed review of the actual circuit routing was performed. A sufficient number of circuits that do not share a common fire area were found thereby reducing the sum total HIF current to less than pass / fail criteria.
! Phasej (Reference page 13 of the handout) Phase 3 of the analysis is being performed to remove the restorative procedures. Thi.s is being accomplished utilizing more realistic assumptions. In this phase the realistic detailed circuit routing on a per 4 fire area basis is used, with only cables routed throuch the fire area of concern experiencing a simultaneous high impedance fault.
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Docket Nos. 50-277/50-278 Page 9 of 12 Page 14 of the handout illustrates a more realistic example of actual L circuit routing. The power supply is centrally located with circuits being routed in all directions. Although in the example power supply only ten circuits are illustrated, in reality the number is approximately twenty five to forty. The number routed through any fire area of concern will only be a percentage of those available. It should also be noted that for the fire area where the power supply is located, no SSD loads are required for the safe shutdown method used in that fire area. The power supply is not postulated to survive a fire that occurs in the fire area in which it is located.
In this phase the 1000 second current rating of a protection device is again being used to calculate the sum total HIF current by adding algebraically only the contribution of those circuits routed through the fire area of concern. This sum total will then be compared to the two step pass / fail criteria previously used in Phases 1 & 2. The power supplies that pass the pass / fail criteria will then be the basis for removing the restorative procedures on a per fire area basis.
Analysis Results (Reference page 15 of the handout) The results of raalyzing the PBAPS Units 2 & 3 SSD power supplies
, (switchgear, load conters MCC's and panels) were that 39 passed the Phase 1 analysis and 30 req.. ired restorative procedures acd further analysis by Phase 3. A breakdo m on a per unit basis is as follows:
Power Supplies Passed Passed Analyzed 1000 Sec 60 Sec Failed Unit 2 28 14 2 12 Common 12 1 4 7 Unit 3 22 14 4 11 Total 69 29 10 30
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Docket Nos. 50-277/50-278 Page 10 of 12 Procedures for Power Restoration A meeting was held in mid-February 1989 between Engineering, PBAPS Fire ' Protection Group, and Operations Support to address operation response to possible multiple high impedance faults (MHIF). From this meeting the ' method for procedural guidance for MHIF was decided to be incorporated into the T-300 Fire Guides. The Fire Guides provide the operator with vital information required for plant shutdown based upon which fire area is involved.
At Peach Bottom, the initial procedure implemented in response to a fire is ON-114 (OFF-Normal). This procedure will direct the shift supervisor te take action in accordance with the plant scram procedure (T-100) and the T-300 series Fire Guides depending upon plant respense to the Fire (Reference page 18 of the handout). The T-300 series procedures are plant layout drawings which identify the various fire areas, and designates them with respective fire guide numbers (i.e. the main control room is area T-325). The individual Fire Guides are formatted into two sections,
" Protected Equipment," and " Contingency Actions." The " Protected Equipment" section is a list of equipment which, through cable encapsulation or routing, should not become inoperative due to the fire. The " Contingency Actions" section contains direction for manual actions that may be required in order to operate the protected equipment, should they be effected by the fire. In general contingency actions described in the form of an attachment to the Fire Guide. Following this philosophy of the contingency actions section, it was decided to incorporate as an attachment a power restoration l
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procedure to restore equipment tripped due to HIF. This attachment would be I implemented as directed by the contingency actions section. The attachments would be specific to their respective fire area.
1 If a protected piece of equipment fails to operate, and the initial contingency actions are not successful, a loss of power due to a MHIF may be
the cause. The power restoration attachments are identically formatted, { with area specific equipment detailed in two tables. From Table 1 of the attachment the operator identifies the power supply for the component which fails to operate. In Table 2 the power supply location is specified, and l
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'f "' , PBAPS Unit 2 & 3 HIF Resolution . . Docket Nos. 50-277/50-b78 Page 11 of 12 the operator is directed to inspect the component in questions' power supply source breaker. If the component's source breaker is tripped, no further action is required since a problem with the component probably exists. If the component source breaker is not tripped, the operator is directed to check the component's power supply source breaker. If this breaker is tripped, the cause may be a MHIF. The possible fault condition is cleared by opening all load breakers for that power supply, then reclosing the supply breaker. If the supply breaker can not be reclosed, then a true fault condition may exist, and the operator is directed to notify the control room and exit the attachment. If the power supply source breaker can be reclosed, the operator is instructed to reclose only the safe shutdown loads (SSD) supported by the power supply. This should clear the MHIF' condition, and allow operation of the SSD components. This process is shown on page 19 of the handout.
Status Eighty-two (82) fire areas representing both PBAPS Units 2 & 3 were impacted by the.MHIP concern. Consequently, a power restoration attachment was required for each of the eighty-two Fire Guides. All of the 82 attachments were walked down by a representative of the site fire protection group for accuracy. A sample attachment was reviewed for usability by the Floor Foreman, who is the senior non-licensed supervisor on the operating shift.
His comments were incorporated into the attachments. Prior to submittal to the Plant Operations Review Committee (PORC) for approval, a sample attachment was reviewed by the following personnel:
- Operation Support Emergency Operating Procedure Coordinator (EOP) -
Licensed Reactor Operator (RO) q l
- Senior Technical Assistant for the Power Generation Engineer l All the time of the meeting it was stated that all of the T-300 Fire Guides were scheduled for PORC review on March 16, 1989. Subsequent to the meeting all T-300 fire guides have been approved by PORC. It was also stated at the
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HIF Resolution Docket Nos. 50-277/50-278 Page 12 of 12 meeting that a training session for both licensed and non-licensed operators on the T-300. Fire Guides is scheduled for each crew prior to restart. In
. addition, subsequent,to the meeting, a walkdown of a power restoration attachment for non-licensed operators has also been scheduled as part of this training.
Conclusion In conclusion, the restorative procedures that have been implemented at PBAPS to resolve the issue of multiple high impedance faults are based on a conservative analysis philosophy. This analytical philosophy used is similar to that used by other licensees based on limited discussions PEco has had with others. The number of restorative procedures implemented is a maximum number required to resolve the issue of multiple high impedance faults. PECo fully expects the number of restorative procedures that are ultimately required to be reduced as additional analysis using realistic assumptions is completed.
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K ETING AGENDA-
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APPENDIX R - HIGH IMPEDANCE FAULT RESOLUTION Peach Bottom APS 3/15/89 Introduction W. J. Boyer Background W. J. Boyer Approach Technical G. L. Spinka Procedures C. J. Kerr Status C. J. Kerr
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Ccnclusion W. J. Boyer
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PBAPS UNITS 2 & 3
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l ; l Presentation to NRC by Philadelphia Electric Company 3/15/89
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h BACKGROUND
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uce ket Nos. 50-277/50-278 !
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q l GENERIC LETTER 86-10 SUBJECT: IMPLEMENTATION OF FIRE PROTECTION REQUIREMENTS QUESTION: 5.3.8: Should Circuit Coordination Studies Consider High Impedance Faults ,
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RESPONSE: To meet the separation criteria of Appendix R, simultaneous high impedance faults should be i considered for all associated circuits located in the fire area of concern.
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NRC LETTER (December 19,1988) e Written Procedures for Manual Clearing of Faults e Change Breaker Fuse Coordination ! e Split Common Bus; Add a Parallel l Supply Breaker e Reroute or Shield Common Bus Load Raceways e Submit Additional Analysis Using Probablistic Arguments L Pg. 5 l
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t APPROACH
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6,. n. . - Docket Nos. 50-277/50-278
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I APPROACH .i l
PHASE 1 i l
- Are Restorative Procedures required? j l
e Conservative Screening Assumptions i PHASE 2
- Can Restorative Procedures be used?
PHASE 3
- Can Restorative Procedures be eliminated?
e More Realistic Analysis input
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Pg. 7
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l Docket Nos. 50-277/50-278
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ANALYSIS APPROACH PHASE 1 ASSUMPTIONS e All 3ower bus circuits are routed through all tire areas of concern.
- All circuits experience a simultaneous high impedance fault.
PASS /FAllCRITERIA e Step 1 - Source Breaker / Fuse 1,000 Sec.
Rating e Step 2 - Source Breaker / Fuse 60 Sec. , Rating j i ! l v Pg. 8
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Docket Nos. 50-277/50-278
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i i ANALYSIS APPROACH (Continued) PHASE 2 ASSUMPTIONS e All SSD Power Bus Circuits are routed through all fire areas of concern.
o All SSD circuits experience a simultaneous high impedance fault.
PASS /FAllCRITERIA
* Step 1 - Source Breaker / Fuse 1,000 Sec. l Rating i e Step 2 - Source Breaker / Fuse 60 Sec.
Rating
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- _ - _ - _ _ - _ _ _ _ _ _ - - .. ,, .. * *
Docket Nos. 50-277/50-278
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ANALYSIS APPROACH (continued) PHASE 3
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ASSUMPTIONS e Detailed circuit routing on a per fire area basis.
o Only cables routed through fire area of concern experience simultaneous high impedance fault.
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e Step 1 - Source Breaker / Fuse 1,000 Sec.
Rating e Step 2 - Source Breaker / Fuse 60 Sec.
Rating i i
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' i t, i... Docket Nos. 50-277/50-278
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PBAPS UNITS 2 AND 3 ANALYSIS RESULTS PHASE 1
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e 69 POWER SUPPLIES ANALYZED 120V - 4160V AC 250/125 DC e 39 POWER SUPPLIES PASSED HIF ANALYSIS PHASE 2 e 30 POWER SUPPLIES REQUIRED RESTORATION PROCEDURES ! I Pg. 15
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Docket Nos. 50-277/50-278
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PROCEDURES e ON-114 - FIRE REPORTED IN THE POWER BLOCK e T-100 - SCRAM PROCEDURES , o T-300 - FIRE GUIDE
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-t' Docket Nos. 50-277/50-278
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j STATUS i I i l
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Docket Nos. 50-277/50-278
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RESTORATION PROCEDURE STATUS I PHASE 1 & 2
I e ANALYSIS - COMPLETE l e HIF FIRE GUIDE ATTACHMENT- i COMPLETE o OPERATIONS REVIEW - COMPLETE e PORC SCHEDULED - 3/16/89 e OPERATOR TRAINING SCHEDULED - PRIOR TO RESTART PHASE 3 e ANALYSIS -IN PROGRESS Pg. 21
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CONCLUSION i e Conservative Analysis Philosophy i e Maximum number of Restorative Procedures in place prior to Restart e Required Number of Restorative Procedures will likely deminish as additional analysis completed
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