ML20042D342

"Draft Meeting" is not in the list (Request, Draft Request, Supplement, Acceptance Review, Meeting, Withholding Request, Withholding Request Acceptance, RAI, Draft RAI, Draft Response to RAI, ...) of allowed values for the "Project stage" property.

Summary of 891227 Meeting W/Numarc to Discuss Draft Augmented Guidance Prepared by NUMARC to Address Station Blackout rule,10CFR50.63.List of Attendees & Subj Guidance W/Markup of Staff Comments Encl

ML20042D342
Person / Time
Issue date:	12/28/1989
From:	Chopra O Office of Nuclear Reactor Regulation
To:	Thadani A Office of Nuclear Reactor Regulation
References
TAC-40577, NUDOCS 9001090018
Download: ML20042D342 (15)

Text

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t DE03B 133 y

MEMORANDUM FOR:

Ashok C. Thadani, Director Division of Systems Technology-THRU:

Faust Rosa, Chief Electrical Systems Branch Division of Systems Technology FROM:

0. P. Chopra Electriedl Systems Branch Division of Systems Technology

SUBJECT:

MEETING

SUMMARY

- STATION BLACKOUT ISSUES-(TACf40577);

A meeting was held on December 27, 1989, to discuss draft = augmented _ guidance-prepared by NUMARC to address the SB0 rule,'10CFR 50.63. Enclosure lhis a list of meeting attendees.

The attendees discussed staff's marked up comments on the augnented guidan' ce-(Enclosure 2) which consists of two parts titled "NUMARC 87 00 Supplemental Questions / Answers" and "NUMARC 87 00-Assumptions." The staff and NUMARC agreedi_

/

on changes made to answer.to question 0.2,_however, answers to questions 3.4, 7.2 and B.3 were-modified based on mutual agreement.

It.is our. understanding 4

that the changes will be reflected in' the development of the final document.

A mark.up (Enclosure 3) of the affected pages (4,5,6) of_ Enclosure 2 which y

' reflect the mutually agreed upon changes;is also-attached.'

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O. P. Chopra

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Electrical Systems Branch _

Division of Systems, Technology ;

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SENT SY:Xerex Tele 8991er 1921 112-20-89 i 5:2EPR i 2027851896*- -492 0268:s 2; NUMARC 87-00 SUPPLEMENTAL QUESTIONS / ANSWERS GENERALRESTIONS 0.2 Q: Are utilities reauirod to apply the NUMARC 87-00 assumptions and methodology to their station blekout calculations and supporting. documentation? A: NUMARC 87 00 consists of guidance acceptable to the NRC for demonstrating compliance with the station blackout rule. Alternative methodologies may be used by utilities, but will be reviewed' independently by the Staff, it is recognized that utilities may have used alternative- \\, I methodologies that conservatively bound those of NUMARC 87-00. Virtually all utilities utilized the approved generic response. format in providing to NRC information required under the station blackout-rule. The generic response contains a statement that the utility used NUMARC 87-00 methodology and technical bases in preparing the submittal. Where this was not the case, it is important to identify and document the alternative methodology used. If this has not been done, utilities should consider providing additional information to the NRC. 0.2 Q: What level of planning must be complete to support modifications. t (if any) which a licensee proposed in the station,blac,kout submittgl?,, W, p g/ r v g.we..( . f.. q yw r.wb 6.* A: Licensees should have identifi the. nature of any modifications a required to meet the station blackout rul 'and a proposed schedule for implementation. The implementation statu of conform to 10CFR50.63 Sections C(1)(iii), C(3) proposed modifications should andC(4). SECTION 1: INTRODUCTION 1.1 Q: Is it necessary to perform further analyses to verify that baseline assumptions of NUMARC 87-00 are valid for each plant, or is an assumption a. "given"? A: Section 1.3 of NUMARC 87 00 suggests that utilities ensure baseline assumptions are applicable to their plants. Per Question / Answer 3 from: Responses to Questions Raised at the NUMARC 87 00 Seminars-(NUMARC 87-00 October 1988), ' utilities are not expected to perform rigorous analyses or L evaluations in verifying the assumptions of NUMARC 87-00." However, the validity of assumptions for each plant should be established and documented.- d A list of major assumptions among those to be verified has been provided to utilities by NUMARC. Each assumption on the list should be reviewed to assure 1 applicability to individual plants. 1 i

SENT'BY:Xerex Telecepier 7021 112-20-89 : 5:29PM i 2027i51hIl 'C l EECTION 2: RENERAL CRITERIA AND RASELINE AttuMpT10MS 2.5 Reacter toelant Invanterv Loss 2.1 Q: Must the assumed 25gpm reactor coolant pump seal leak rate be used by all plants (BWR and PWR)? A: No. It is acceptable to NRC to use-18gpm for BWR recirculation Leakage rates lower than 25 gpm for PWRs or 18 gpm for BWRs may be pumps. used, provided a.iustification exists and the NRC is informed that lower ~ g , s rates are being utilized. 2.7 Effects of Lets Ventilation 2.2 Q: Is it necessary to provide reasonable assurance of equipment operability in dominant areas of concern where temperatures'are below 120F7 A: The need to establish reasonable assurance of equipment operability applies only to dominant areas of concern. Att Section 2.7.1 of NUMARC 87

00. Adominantareaofconcern(DAC)existswien,basedondocumented enoineerino iudaement areas containing station blackout response equipment have substantial heat generation terms and lack adequate heat removal systems due to the blackout. 11ANUMARC87-00,p.-7-18.

If temperatures in the DAC are calculated to be equal to or. less than 120 degrees F, this establishes reasonable assurance of equipment operability without further analysis. If temperatures in the DAC are calculated to be in excess of 120 degrees F, reasonable assurance of equipment operability must be provided. NUMARC 87-00, Appendix F, and its accompanying topical report provide acceptable methods for assuring equipment operability. For the control room, even though it may not meet' the DAC. criteria, a heat-up analysis should be documented to demonstrate that temperatures do not exceed 120 degrees F-. If temperatures exceed 120F, reasonable assurance of-station blackout response equipment operability must then be provided. NUMARC 87 00, Appendix F, and its accompanying topical report provide methods for t I assuring equipment operability. In the control room, cabinet doors should be opened within 30 minutes of the onset of SB0 to provide adequate air mixing to maintain internal cabinet. temperatures in equilibrium with the contro1' room temperature. Refer to NUMARC 87-00, Section 2.7.1, p. 1-9 and 2-10. For additional information, refer to Question / Answer Nos. 4, 6, and 82-from the Responses to-Questions Raised at the NUMARC 87-00 Seminars.(NUMARC, October,1988). 2.3 Q: May masonry, sheet metal or gypsum walls be assumed-as heat sinks in the NUMARC 87-00 room heat-up calculations? 2 i

5ENT sy:xerex Telecocier 1021 112-20-89 i 5:30PN i 2027851898* 452 02sota 4: At The NUMARC 87 00 methodology assumes poured concrete walls to be the heat sink. Other wall materials are not addressed by the methodology, If other wall materials are used, additional calculations must be performed and the use of such calculations should be identified to the NRC. 2.4 Q: May air volumes above drop ceilings, such as in the control room, be used for calculation of room temperatures using the NUMARC 87-00 methodology? A: Generally, no. A continuous ceiling is assumed by the methodology-to inhibit any heat transfer to the volume above unless ceiling tiles are removed, by procedure, at the start of the blackout. If air volumes above-drop ceilings are used and ceiling tiles are not removed by procedure, additional heat transfer calculations would be necessary and the basis of such calculations should be identified to the NRC. 2.5 Q: What wall temperatures may be assumed when applying the NUMARC 87-00 methodology to poured concrete walls acting as heat sinks in air conditioned rooms? A: If the room on the.outside of the wall is warmer than the room on the inside, the average wall temperature should be used. The wall, in this 1 case, will not be as effective a heat sink as a wall uniformly at the inside i room temperature. 2.6 Q: Are any restrictions placed on taking credit for opening doors to an outside room? A: Yes. To allow credit for opening doors for. cooling, the outside i room should be cooler than the room being analyzed-and should-be sufficiently-large that hot air from the inside room will not appreciably alter the 's tem >erature of the outside room. Opening _the control room door to a closet or (itchen for example will not provide a sufficient-heat sinkLand should not be credited. Furthermore,. blackout response procedures should identify the doors to be opened. 2.7 Q: Are there circumstances where cabinet doors need not be opened as provided in Question / Answer No. 82 of Responses to Questions Raised at NUMARC 87-00 Seminars (October,1988) to ensure that the control room is not a DAC? A: Yes. For example, cabinet doors need not be opened where fans are powered during SB0 to provide forced ventilation of cabinets or if HVAC is provided during $B0 t =ht9 tM :=tr:1 :: ; hh MOT. SECTION 3: REQUIRED COPING DURATION CATEGORY i 3.2. Part 10. Evaluatina Indonendence of off-site Power 1vstem 3.1 Q: How quickly must manual transfers be-made, when evaluating the independenceofoffsitepowersystems(IGroup)? i 1 3 l

{ SEN[ BY: Xerox Telecopier 7021 :12-20-80 i 5:30PM : 2027551895-492 0260:# 5 A: Any manual method of transferring power sources-for all safe shutdown buses is acceptable providing the transfer can be accomplished in a reasonable t time, such as less than one hour. Thus, a manual transfer involving operation of a disconnect link requiring several hours to complete is not acceptable. 3.2 Q: How independent must switchyards be for the purpose of I Group determinations? A: A 'no" answer to Criterion A, p. 3-11.of NUMARC 87 00 requires that multiple switchyards must be physically and electrically independent. Electrical independence can be provided by normally open breakers, i.e., two open breakers in series, between switchyards or busses. Physical independence would be satisfied by two separate and distinct switchyards each bounded by-a perimeter fence. Supplying power to plant unit safety busses via, 1) e N multiple voltage transformations occurring within a single switchyard (-area, or (2) via designated switchyard busses originating from a single switchyard, 1 does not satisfy the intent for physical switchyard independence. 1 3.3 Q: Where normal AC power is provided by the unit main generator and only one of two safe shutdown buses is automatically or manually transferred to preferred or alternate off-site sources, does that qualify as a transfer of all safe shutdown buses? A: No. All safe shutdown buses must be transferred per Criteria B(1) andB(2),p.311,ofNUMARC8700. g 3.2.2. Part 2.B Determine the Number of Nece n arv EAC Standbv Power systems 3.4 Q: When determining the number of EAC standby power sources necessary to operate safe shutdown equipment, what safe shutdown loads should be considered? .f t' g i td;n h: n f:1 h u b; ; h ;; ef eff ;1 % ;;.;;r [.00 0 e nf: teu-h:e =3 5: 6t=ind f = m ;unt*: e:i;r ten j 1: From NUMARC 87 00, p. 3-15: t The number of necessary EAC standby power sources should be '\\. determined by accounting for the individual safe shutdown \\ N '( / loads or inferred from the site's design basis for operating-i \\ Class 1E equipment without off-site-power. s However, if the safe shutdown loads selected for operating Class IE f equipment during a LOOP event are different from the design basis safe shutdown loads, the utility must determine that the shutdown loads powered are capable ' of maintaining the plant in a safe condition for an extended period (i.e., Qongerthanthecopingduration). i 4 ) e v,,.n ..._,_--.-._...e-. --,,_,or ~ m

+ SENT' SY: xerox Telecopierl021 :12-20-69 i 5:31PN i 2027851896* 492 0260:86 a l 3.5 Q: Does safe shutdown mean cold shutdown? U4 A: No. The plant should be brought to the desien basis safe shutdown condition, which may be hot standby, hot shutdown, or cold shutdown. 3.6 Q: At a multi unit site, if an EAC source.is used as an AAC source, should that EAC/AAC source be excluded from the number of EAC standby power supplies used to determine the blacked-out unit's EAC Group? A: Yes. An AAC source which is also an EAC source must.be' subtracted from the number of EAC sources available as EAC standby power supplies. To-do otherwise would be double counting as discussed in NUMARC 87-00, p. 3-14. SECTION 4: STATION BLACKOUT RESPONSE PROCEDURES 4.f.1 Station Blackout Rasennse Guidelines 4.1 Q: Is it acceptable to dispatch an operator from the control' room to the remote shutdown panel for the purpose of providing power from the Appendix R diesel or the safe shutdown facility? I A: Yes. However, the control room should not be abandoned. It is

r. v anticipated that recovery from a station blackout may require operator action vb or monitoring from the control room.-

SECTION 7: COPING WITH A STATION BLACK 0UT EVENT 7.1 Q: When ensuring containment integrity, can normally closed valves be excluded from consideration similar to valves normally locked closed during operation per NUMARC 87-00, Section 7.2.5, Step 1 (1). A: No. A normally closed valve may not be considered to' be a normally locked closed valve unless some action is taken to prevent valve operation. Such actions would include removing control power fuses or racking-out-breakers supplying power to motor operators. 7.2 Q: Can the main control room be disabled and evacuated to reduce the - battery loads when assessing battery capacity to support decay heat removal during SB07 A: No. The plant monitoring and electrical system controls are an i integral part of the control room and are considered essential for successfully a uti ity to disable and evacuate t,he cA. Therefore, it.is unacceptable for-M p y,- copin with and recovering from the $B0 rol room for the purpose of reducing ,A g battery loads. No-w-v). M/ g~~ ~ $ana$g,1((,x.jG.g Jua,r.wL,) J &.% M J'g4; m-g 5 hf ? t 555 M MLr~Mn.e1..n+4 m -w h dg g %j

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SENT BY:Xerex Telee991er 1081 192-29-89 : 5:31PW i 2027651865* 4Wr ene.a t APPENDIX B: ALTERNATE AC p0WER CRITERIA What single failure considerations are applicable at a multi-unit B.1 Q: site where EAC sources are utilized for AAC7 When a Class IE emergency AC (EAC) source is used as an AAC source, a single f ailure is applied to one of. the EAC power sources in the non-blacked-A: If the remaining EAC source meets the criteria of NU M RC 87-00 Appendix B, AAC power is assumed to be available to the blacked out unit. out unit. Refer to NU MRC 67 00, p. 1 2 through 2 4. i What single failure considerations are applicable-to $80 AAC power B.2 Q: systems? Per Criterion B.8.e of NU M RC 07-00, the AAC power source must not-be susceptible to a single point vulnerability whereby a likely weather related - A: event or single active failure could disable any p@ortion of the on-siteor the preferred - t emergency AC power sources 3Birggralibi+*=iibioiMm4 site) power sources, and simultaneously fail the AAC power sou 3 4 andneednotbeconsidered.Jm~ (f. w/ A (. / e What loads must be carried by an AAC source which is also an EAC-B.3 Q: source? L.C d t.dt,. : SM& The AAC source must carry the safe shutdown loads on the non blacked-A: out unit ':n enti= =d =: = 3.', 2;';d and the station blackoutjoads i' tial i rin6 -f-tfRiTen41acked'.Ance $9AAas been confirmed,:. shedding on the blacked out unit. 're i out.pnit is acce table arevided the loads l (' argMmonstrated capableg1haintaining thepeAlacked-out un a safe ' A l t 4(ndition'for the duraHon of the $80. # - _.. ~. _ _ ,p( Criterion B.g of NUmRC 87 00 states, "The AAC power system shall be sized \\ ,.p - ---.s to carry the required shutdown loads for the required coping duration } T determined in Section 3.2.5, and 'be calable of maintaining voltage: and i frequency within limits consistent witiestablished industry standards that .At'a j b) will not degrade the performance of any shutdown sys multi-unit site, except for 1/2 Shared or 2/3 emergency AC power-configurations, an adjacent unit's' Class IE power source may l t' i ~ required loads at both units.' It is expected that AAC sizing determinations consider both steady state 1 -g -l and dynamic loading effects, . ~ . M M d D %) n a uc w [q4rw or t, (.4 /u hM <dd.M M % nA(, t4 jt 4p.,' %f dw Nw %s.k-t o o e p' %.% ~ bLAIat 4

h2OpsO SEh. SY:Xtrox-Teleccpier 7021 88 5 2 r; 2021Hi p d f-l l i APPENDIX C; 1 AMPLE AAC CONFIGURATIONS Is it acceptable to connect the AAC source to the blacked out unit-C.1 Q: j by a single cross-tie? l i However, when the AAC source is one of the available' Class IE-EAC sources, the cross-tie must be able to supply power to the blacked out A: Yes. (' K unitfromanyEAC/AACsource, o t A single cross-tie connected to either of two EAC sources. l' Era *< ele 1 -) Figures A and B, Attachment 1, show two such cross-tie. con'igurations, although acceptable configurations are no is hecentable. examples. use of the second EAC source for AAC power. Figure C, attached, illustrates a potentially unacceota31e-single cross tie connecting one EAC source to a second.EAC' source, and tie Examele 2.. connecting the second EAC source to ?he blacked out. unit. t 12 are not available, and either diesel 21 or 22 is ass The remaining diesel (21;or 22) may be designated as an EDG single failure. AAC source provided Appendix B criteria are satisfied.7 EACsource(21or22)istheAACsource, -I F i q 1 9 i 7

"},SfATBY:XerexTelegener 1821 192-28-8B 3 5:32 W i 2027t&1tita 462 S2 tats e i -A 1 i l l 1 R$ERC B7-00 A15LarilGits j i i As stated in NUMARC 87 00 Section 1.3, it is important that utilities-l verify that baseline assumptions are applicable to their plants. Chapter i of NUMARC 87 00 discusses baseline assumptions however, other chapters. include j additional assumptions, as well. Many assumptions are verified in the course of performing the various coping calculations, but some assumptions require 1 specific ver<fication, j The rigor to be applied by licensees in verifying assumptions is stated in Question / Answer 3 of Responses to Questions Raised at the NUMARC 87 00 i Seminars (October 1988): ' utilities are not expected to perform rigorous i analysesorevaluat.ionsinverifyinE.theassumptio,nsof,NUMARC4700"..... i &_.u,.. ..._ u., ...s ..u s... a....._.. % :L !..t' C :':Jr,7L'T..:r:/nrL mc':'C'L'L'" r-' ._o HiveheintIIItiss'a'eixpecteftievalusie'delppiicadIt[be documented U the i r assumptions to individual plants, and this evaluation should i i i and available for NRC review. l Listed below are major assumptions which in some cases have not been f satisfactorily verified. Preceding each assumption is the number of the applicable NUMARC 87 00 section. 2.4.1(1) The event ends when AC power 1,2 restored to shutdown busses from any source. To support AC power restoration it will be necessary to close breakers. This can be done either manually or electrically r r;

• via DC power. For those utilities utilizin; DC power, the ability to close breakers at the end of the blackout siould be included in the batter ~' calculation. The first available power source can be an EDGt therst e flashing of the EDG field should also be included in the l

calculation. 2.5.2 Reactor coolant pump seal leakage-is assumed not to exceed 15 I gpm per pump. It is recognited that SWRs do not have reactor coolant 4 pumps; however recirculation pump leakage should be evaluated. The WRC 1 staff has indicated that 18 gpm is an acceptable assumed le'akage rate for BWR recirculation pumps. SWRs/PWRs taking credit for lower leakage rates should have documentation to support use of the lower rates. 2.7 Loss of ventilation effects. t.7.1 Temperatures resulting from loss of ventilation are enveloped by LOCA and HELt profiles. LOCA/ Hill transients dump i large amounts of energy into a containment in a short. time, lyses

thus, i

1 this assumption may seem intuitive. However, LOCA/HELB ana assume fans and coolers are operating. During $B0, containment fans j 1 1 1

and coolers may not be available. This assumption, therefore, should be verified. 2.7.1(2)(a) Control room temperature does not exceed 120F. Utilities usually verify this assumption, but sometimes misapply the methodology of NUMARC 87 00, Section 7.2.4. See below. Typical problems encountered with utility use of the methodology of Section 7.2.4 to calculate $80 temperatures in the control room and dominant areas of concern are as follows: es 1) Initial wall temperatures assumptions are not verified by actual measurements i i s' !) Wall temperatures for walls actina as heat sinks in air conditioned j rooms are assumed to be at the initial room temperature. This is valid if the rooms on both sides of the wall are air conditioned ) to the same temperature. If the outside wall temperature is hotter, i 1.e., not air conditioned, the average wall temperature, not the 1 air conditioned room temperature, should be used: 4 3) Where a continuous drop ceiling prevents free passage of air out of the dominant area of concern, air volumes above can not be i included in the analyzed room's free volume when using the NUMARC 87 00 methodology. Other analyses can properly take credit for l heat transfer across the ceiling tiles, and these additional analyses l should be identified to NRCI 4) Only poured concrete walls may be used as heat sinks, not cinder take credit for othe(Section E.3.1)l materials, and these additional block or wa11 board Other analyses can properly r types of wal analyses should be identified to NRC; l 5) In order to take credit for opening doors to an adjacent room, the adjacent room must be large and at a lower temperature relative to the room in question. (133SectionE.3.3.) Opening a closet door, for example will not provide a significant heat sink and can not be credited. 2.7.1(t) (b) Loss of heating in the battery room is assumed not to affect battery capacity, provided battery capacity calculations used the lowest electrolyte temperature anticipated under normal operating conditions", further consideration of loss of battery capacity is not required, per NUMARC 87-00, p.7 7. i b 6

ggliT BY: Xerox Teletepie? 1021 111-10-15 i 5:8DPR i 2021851885~ all OllD:e 5 pc.t.ec est s A: Any manuel method of transferring power sources for all safe shutdown buses is acceptable revidin the transfer can be accomplished in a reasonable L. k time, such as less t an one out. Thus, a manual transfer involving operation of a disconnect link requiring several hours to complete is not acceptable. 3.t 0: How independent must switchyards be for the purpose of I troup deteminations? At A 'no' answer to Criterien A p. 3 11 of NUMARC 87 00 requires that multiple switchyards sust be physically and electrically independent. Electrical independence can be provided by normally open breakers, i.e., two open breakers in series, between switchyards or busses. Physical independence multiole voltese transformations occurring within a single O k would be satisfied b pplyins power to plant unit safety busses via,

area, or(t)viadesignatedswitchpardoussesericinatinafromasingleswitchyard, dnaimot satisfy the intent For physical sultchyar11 independence.

3.3 Q: Where nomal AC power is provided by the unit main eenerator and only one of two safe shutdown buses is automatically or manually transferred to preferred or alternate off site sources, does that qualify as a transfer of 11 safe shutdown buses? [, A: No. E,1 safe shutdown buses must be transferred per Criteria 8(1) and 8(2), p. 3 It, of NUMARC 87 00. 3.2.2. Part f.B Batermine the 8' ar of blecessary ht Standby power Evstame 3.4 Q: When detemining the number of EAC standby power sources necessary to operate safe shutdown equipment, what safe shutdown loads should be y considered?

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l 3.5 Q: Does safe shutdown mean cold shutdown? ) condition,whichmaybehotstandby,hc1httothedenianbasinsafeshutdown A: No. The plant should be bro Lt. shutdown, or cold shutdown. l 3.6 Q At a multi unit site, if an EAC source is used as an AAC source, should that EAC/AAC source be excluded from the number of EAC standby power supplies used to determine the blacked out unit's EAC $roup? 4 i GK At Yes. An AAC source which is also an EAC source must be subtracted from the number of EAC sources available as EAC standby power supplies. To do otherwise would be double counting as discussed in lluMARC 87 00, p. 314. l RECT 10N or ETATION BLatgntri tripnwer ponernutEs 4.f.1 Station Blackout Ramannaa Ruidelinas 4 4.1 Q: Is it acceptable to dispatch an operator from the control room to the remote shutdown panel for the purpose of providing power from the Appendix R diesel or the safe shutdown facility? ) A: Yes. However, the control room should not be abandoned. It is g anticipated that recovery from a station blackout may require operator action i or monitoring from the control room. i RECTION 72 TOPING WITH A STATION RLatt0UT EVENT 7.1 Q: When ensuring containment integrity, can normally closed valves be excluded from consideration similar to valves normally locked closed during l operationperNUMARC47-00,Section7.t.5, Step 1(1) A: No. A normally closed valve may not be considered to be a nomally j 'sigd closed valve unless some action is taken to prevent valve operation. ( huch actions would include removing control power fuses or racking out breakers l L supplying power to motor operators. 7.2 Q: Can the main control room be disabled and evacuated to reduce the battery loads when assessing battery capacity to support decay heat renoval during $807 s wne y 6a8 W-e - ( hk As flo. The ant monitoring and electrical system controls \\are an integral part of the control room and are considered essential for successfully Therefore it is unacceptable for coping with and recovering from the Sto.;krotroom for the purposegredusdA9 a uti.it to disable and evacu g he cd 'g,m't

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~ j stNT SY:Xerex Teletopier 1021 112-10-00 t 6:31PN 1 2027051896* ass v4ev.o e A;; 3 DIX St ALTERNATE E ptntER ttffs't1A l l 5.1 Q: What single failure considerations are applicable at a multi unit site where EAC sources are utilised for AAct A: WhenaClass1EemergencyAC(EAC)SourceisusedasanAACsource, ) l a single fativre is applied to one of the EAC power sources in the non blacked-If the remaining EAC source meets the criteria of NUERC 87 00 i out unit. Appendix 8 AAC power is assumed to be available to the blacked out unit. l Refer to NUMARC 57 00, p. 1 2 through t 4. j L B.t Q: What single failure considerations are applicable to 580 AAC power systemst j A: Per Criterion B.S.e of NUERC 87 00, the AAC power source must not 1 be susceptible to a single point vulnerability whereby a likely weather related event or single active failure could disable any portion of the on site Lor the preferred (off-g( emergency AC power sources Random l site) power sources, and simultaneously fail the AA; power source. ,N

• failures other than the type addressed by Criterion t.8.e are not contemplated 4

and need not be considered, far Q. M A (, / e 1 s urce which is also an EAC 8.3 Q: Patloadsmustbecarrief '"p** M J f i source? .M gri C*,_5*Me?_" out unit {' r ; =:t' = =? = :Z r. M, 2 :'/ O and 4he station blackou A: ds I 4f/ on the blacked out unit / A ice as-been u,4ined ding se 1 6 l ( r,nn me,ap 61sdoc out is acceptable ded the loads red A.- - ! 9f g. a o ed capable 41ntaining the lacked out un a safe l/ 4 di for_the dura. On af.-the-880.- Criterion B.9 of NUMARC 47 00 states 'The AAC power system stall be sized [ ' [' to carry the required shutdown loads for lhe required coping duration determined in Section 3.t.5, and be capable of saintaining voltage and frequency within limits consistent with established industry standards that At a (A i y will not degrade the performance of any shutdown systems or component. '\\ multi unit site, except for 1/2 Shared or 1/3 emergency AC pow l ,,f i AAC power source for the blacked out unit if it is capable of powering the p required loads at both units.' + lt is expected that AAC siting determinations consider both steady state l and dynamic loading effects. l A ik nam

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