ML20024H654

Forwards Response to Nrc/Saic Questions Posed During 910509 Telcon Re Station Blackout

ML20024H654
Person / Time
Site:	Callaway
Issue date:	05/31/1991
From:	Schnell D UNION ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-68524, ULNRC-2416, NUDOCS 9106070291
Download: ML20024H654 (11)

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hE May 31, 1991 U.S. Iluclear Regulatory Commission Attnt Docun.ont Control Dosh Mail Stop Pl-137 UL11RC- 2416 Washington, D.C. 20555 llRC TAC llo. 68524 Gentlement CALIAWAY PIAllT DOCKET liUMDER 50-403 STATIOff DIJsCROUT Poferencoat 1) U L!IRC-197 3, dated April 12, 1989

2) U Lil R C - 2 1 8 2 , dated March 29, 1990 A tolocon was hold on May 9, 1991 betwoon Union Electric and 11RC/SAIC to discuss the callaway Station Blackout (SDO) submittal. The results of this tolocon, in the form of liRC question and Union Electric responso, are contained horcin.

Please contact un if there are any questions concerning this information.

Very truly yours,

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/,;, Donald P. Schnell jp~

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i Alon C. Pnnnwnt er, of 1 awf til nye, beino firnt duly nwotn utson oath nnyn that hn in Mannger, 1,1 conning and Fooln (thielonr) for  !

tinion Electric Company; thnt. he hnn send the f or ngn.i nri document anti s knows the content thornof; that he han executed the n orne for nnd on behstf of enid company wi th full pownt nn<1 nuthority to do no; nnd that the facto therein sinted nro true niul cot t eet to the bont of hin i ltilowl e d uta , 11) f ol m a t i oti niid belief.

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DARDARA'. N Aff' Not ARY PUBLIC. St Att Of MissWki MY COMMISMON inNRis APRIL 22, 1993 '

ST. LOUIS -COUNTY 1

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ces T. A. lin x t o r , Enq.  !

Shaw, P.i t t man , Pot t.n & Trowbridgo 2300 11. St i ent, 11. W .  :

Wnnhington, 1).C. 20037 '

I Dr.-J. O. Ce t ninit i CFA, Inc. I 19225- A Flownr 11111 Way .

Unitherstsury, itD 20079-5334 11 . C. 1* tion Chief, Itenctor Ptoject Bianch 1

11. S ', thicl onr Pogiil n t.ory Commi nnit>n llegion 111 799 lloonovel t Itonc!

Otan Ellyn, i111noin r,013 7 i

Bruco Unrtlet.t i Onllawny Ronidant Offier.

U.S. thiclent fleguintory Comminnlon  :

IllHil i

Stontiman, Minnout1 65077 M. D. I;ynch (2)

Office of thicinar React or Hngtilation j U.S. thtclear Regulatory Commin91on 1 White Flint, 110 t t h , Mail Stop 13E21 115S5 Pockvi]Io Pihn Rockvi1In, MD 20052 Mnnager- Elect ric Departmnnt

, i Minnouti Public Se vico Comminnion i

-P.O.-Box 360 Jeffornon City, MO 65102 Gary DeMoss SAIC 1710 Gootl it hlge Drive

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McClean, VA 22102 i

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-. Attachment UhNRC-2416 IIRC Q.1 Justify the claim that the two preferred sources of 1 offsite power to the ESF buses are independent. ]

UE A.1 -As depicted in Figure 8.2-5 of the Callaway FSAR Site l Addendum and in Figure 0.3-1 of the Standard Plant FSAR, the two Engineered Safety Features (ESF) transformers with their supply circuits from the 345-hV switchyard provide two independent sources of .!

offsite power for the Class 1E buses.

• ESF Transformer XNB01 is supplied by one of the two 345/13.8 kV Safeguard transformers in the switchyard.

• A Safeguard Transformer is connected directly to each 345-kV bus through a disconnect switch. Each Safeguard Transformer has two low sido breakers connected so that ofther transformer may supply XNB01 via underground duct. The 13.8-kV breakers are ,

electrically interlocked so that the low side ,

windings of the Safeguard Transformers cannot be connected together. XHB01 is normally supplied by Saf eguard Transformer B wi th the capabili ty for manual transfer to Safeguard Transformer A. i ESF Transformer XNB02 is supplied from one of the secondary windings of Start-up Transformor XMRO1. g XMRO1 is supplied power from a 345-kV circuit from the switchyard. The 345-kV breakers connecting this <

circuit to switchyard buses-A and B are all normally s closed.

Normally, Class 1E Load Group 1 (Bus NB01) is

• supplied by ESF Transformer XNB01 and head-Group 2 1 (Bus NB02) is supplied by ESF Transformer XHB02. -In '

the event of the loan-of a preferred source, the affected-load group would be automatically supplied by its associated emergency diesel generator.

However, if required, the incoming preferred power supply associated with one load group can supply the 4.16-kV bus of the other load group. This manual transfor is accomplished by operator action in the control room. Each preferred source is sized to supply both load groups simultaneously.

NRC Q.2 Explain what w.ill be stripped, and when it will be

• stripped, to ensure-that the batteries will last for the four-hour SB0 without charging. (The UFSAR-states that the batteries will last for 200 minutes or'3.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> )

UE A.2 To support the SBO. coping assessment for Callaway, calculations employing the methodology of IEEE STD  ;

405 were performed to demonstrate that station batteries have adequate capacity for the four hour coping duration. These calculations assumed a 60F electrolyte temperature and used a 25 percent margin for aging, i Page 1 of 8

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For the Clann IE batteries, no loads arn required to bn shed to achieve a four-hour ca.. city. To be prudent, procedural guidnnee is provided to allow the operators to de-ene191ze the ESF Statun Panels in  ;

order to connervo battery capacity. Thnso paneln may 4- be re-energized if neconnary to evaluate equipment t status. [

h The nonsafety-related batterios do not supply any loads nocessary for decay heat removal during an 880 but do provide bronkor control power to rentoro ,

offsite power to ESF Transformer XNB02. A non-vital i inverter will be shed within one hour after the onnot  !

of the SB0 to assure the capability to operato tho supply breaker to XNB02. l i

The 200 minute Clann 3E battery londing cyclo provided in FSAR Table 0.3-2 in the design load cycle i for the batteries. A footnote will be added to this table to clarify that the batterios have been analyzed for a 240 minute loading cycle to support t the SBO coping analynis.

NRC Q.3 hoon of IIVAC (more detailed explanation in needed)  ;

NRC Q.3.a What are the annumed initial temperaturon? j UE A.3.a The assumed initial temperaturen are: ,

Turbine Driven Auxiliary Feed Water  ?

(TD AFW) Pump Room 113'E (1) [

Battsry & Inverter Rooms 90*F

- Control Roem/1&C Cabinet Room N/A (2) i Mein Steam / Main Feedwater (MS/MFW)

Tunnel 120"F~

(1) NUMARC 07-00 guidance was uned, but plant denign  ;

is baend on lonn of offnito powor/ venti,ation  :

for thin room which dono not have safet; related coolern. The original A/E ntnady stato equilibrium calculation shows 142*F finn 1  !

temperature with loss of power (LOP).

(2) The initial temperature la not applicablo ninco a-steady-stato equilibrium calculation was used. ,

instead of NUMARC equation. The NUMARC equation-is not appropriato for room construction. >

NRC'Q.3.b . Explaln the control room calculations. i UE A.3 b Since NUMARC methodology is not appropriate due to control room construction, a steady ntate equilibrium

. calculation was unod. A combined calculation van dono for the control room proper and the 1&C cabinet room since they are in the name structural enclosure 4

Page.2 of 8

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- . - Attachmont but separated by the control bontd. The control room /1&C cabinet room in encioned by heavy concreto I construction with two exterior walls (SE and NE j axposuro), one wall uith nir conditioned adjacent  !

space and one wall adjacent to the control room IIVAC  :

t equipment room in tho aux building. Air conditioned cable spreading roomn are above and below. Uning tho .

approprinto coef ficient of heat trannfer "O" valuco  !

nnd Q in e O out., finni equilibrium temperaturen woro  !

cniculated'  ;

i NRC Q 3.c What heat loads were unod in t he AFW nnd control t com analynon? (

IfE A.3.c lle a t londn.in tho TD AFW pump room woro not given etnce it wnn acitnowindged thnt the originn1 dontyn i bnnon for the room wun 1,0P and that the nononfoty-rointed room coolorn would bo inoperable. ,

lleat load in the control room is 8.6 1;W nnd in tho i 1&C cabinot room 32.6 KW, for a to t a l o f 41. 2' . j NRC Q.3.d When, npoci ficall y, doen pi oceduro 0T0-01 -00001 require opening inntrumnnt enbinet doorn?  ; UE A.3.d OTO-010-00001 in boing rovined to comply with NUMARC 07-00 2.7.1.2n critorin of "within approximately 30 minutos of tho event (lonn of all AC powor) onnot".  ! NRC Q.3.o What nonures that fully grouted concreto bloc)( walin (used as heat ninl<n l 1 equivalent to poured concrotn , walls) havn enough mnon to approximato concrete? UE-A.3.e The only concreto block walln involved are in the battery and inverter roomn. The cores in theno' blocks were required to be completely filled with grout to achieve the required fire rating. In , addition, the walls are noinmic category 11/I. The i construction proceduto that governed the election of-t hone walin requirod 'innpoctionn by field engineering personnel. 'Thene documented innpectlone included . verification that the walln were fully grouted per tho denign documentn.

                                             ' f RC - Q . 3 . f What are the finn 1 room temperaturen?

5 UC-A.-3.f The finnl-room temperaturen-aro an follown: TD AFW Pump Room 142 F (Originni A/E cnic)(1) Inverter Rooms 103.9"F Battory Roomn 93.7"F

                                                                - Control Room            111,5"F-1&C cabinet Room          98.1"F MS/MFW Tunnel            202.2"F (1)  NUMARC 87-00 Equation E-18 resultn in 136.4"F.

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      *-                                                      Attachment NRC Q.4  What is the expected temperature of the drywell?

Doen it pose equipment operability problems? UE A.4 A plant specific containment analyses was performed for the callaway large dry containmerit. Two casen

                 -were run; one with 111 gpm Re ctor Coolant System (l.CS ) leakage (i.e., 25 gpm/ Reactor Coolant Pump (RCP), 10 gpm identified leakage, 1 gpm unidentified) and one case with no RCS lenhage. The resultn were as followar with leakage - 166 F T^

T no leakage - 173"F The difference in due to the improved heat transfer due to humidity. Both temperatures are well below the Environmental Qualification envelope temperature of 384.9 F for Main Steam ne Break. Therefore, containment temperature 1. .ot a concern for BBO. 4 NHC Q.5 Explain the containment isolation valve (CTV) analysis and how CIVn are treated in SB0 proceduren. Additionally, when are the excluded CIVs operated or tented and do they have electrical indication? UE A.5 The containment inolation valve analysis was performed by reviewing the containment inolation valves identified in FSAR Figure 6,2.4-1 againot the exclusion criteria npecified in Reg. Guide 1.155 Position C.3.2.7 and the exclusions in INMARC 07-00. Once the valven that clearly fell under these exclusions were eliminated, the remaining valven were evaluated to determine whether they should be excluded for other reasons. The following providen some of the specific considerations-that went into the reviews as discunned in the NHC tolecon.

                  - When considering exclusion b) for valves that fail closed on a loss of power,-valves were not excluded unions they had some mechanical mechaninm,-ouch as springs, that force the valve to clone regardless of what position it was in at the time of power f ailure.

Motor operated valven'that fail as-is vero not excluded. The valves-that were excluded are air operated valven and-nolenoid valven that fail closed using spring force. Air operated valven that use DC powered air supply- nolene ids were not excluded since on-loss of AC power thnne valves wil1 not fail closed, i Page 4 of 8

    *           .                                                                                                          Attachment-                   j
                                     -     For the exclunion on non-1ndioactive closed-loop                                                             i systems not expected to be breached in n station                                                                    t blackout, wo excluded valves in penetrationn for the                                                                 J Essential Service Wator, Component Cooling Water, and                                                                l Secondary Sido of the Steam Generator nyntomo.                                                                       j
                                     - Foutteen valven woro excluded because they are in                                                                 i penatrations which would bo isolated by home other                                                                   !

valve, generally a check valvo. This to bnced on tho , allowance that we do not have to assume a ninglo failure. The check valves taken credit for were i either containment isolation check valven or Renctor  ; Coolant System Pressure Isointion Valves (P!V's) which are leak tonted por our Technient Specifications. We did not-take credit for other , valves that welo not containment inolation valven. l

                                     - A opecific annlynin was performed in ordet to                                                                    i exclude the Residual llent Removal (Ri!R) nuction                                                                  ['

isointion valven f rom the RCS hot legn. Although they do not moet the specific exclusionn for normally ocked clocod or for fnil cloned valves, due to the teoign of the.controlo for those valven they could not be open at the onset of a station blackout. These valves _have interlocks which prevent them from being opened- when RCS preneuro in abov6 425 PSIG. It would take a failure of theno interlocks in order for thene valves to be.open and-the SBO analysin does not nasumo ningle failuros. HUMARC 87-00 ansumption 2.2.1 states that the SB0 analynin be performed nanuming the SB0 occurs at 100% power which would menn that our RCS prensure would be approximately 2235 psig.

                                     - A specific analynic wan performed for the RilR nuction isolation valven f rom the containment numps.

Thone valves are verified to be closed once overy month per pinnt Technical Spec.i f i c a ti on s . Thene  ; valves are maintained closed during all power opern-tions and opening the valven would result in ent ry into Technical Specification act. ion staterranta. The

                                  - valves are only opened for nurveillance testing during refuelir.g outages in Mode _5 or 6.                                             These valvos have interlocks which prevent them from being opened when
                                   - the RIIR suct^on loolntion valves from.the Refueling Water Storage Tank are open.                                               Therefore it would again take a failure of-the-interlocks in order for these-valves _to be open at the onnet of a SBO. Daned on tho                                                             ;

namn discussion as above, thenn valven were excluded.

                                     - A specific annlysin wan performed for the Conta.in-ment Spray suction isointion valven from the con-tainment sumpe. These valves are maintained closed during all power operations and opening the valven would result in entry into Technien1 Specification action statements. The valves are only opennd for                                                                  i Pago 5 of a

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+ . Attachment  ! survoillance tenting during tofueling outagen in Mode 5 or 6. The valves are verified to be closed once overy month por plant Technical Specificationn. , The valves are encapnulated insido tankn that aro - designed as an extension of the containment boundary. , Although DC poworod indiration is available in the control room, these encapsulations will provent taking manual control to operate the valves. Ilowever, the containment spray nyntem was designed to contain radioactive fluid following a LOCA. As

                             -discussed in FSAR Figure 6.2.4-1, pago 13, a ningle                     ,

active or paonive failure can be accommodated since  ; the oystem in closed outsido the containment and in  ; designed and constructed commensurate with the design and construction of the containment. The nyntom is  : testod periodically for loaks as part of our i Technical Specification 6.0.4.a Reactor Coolant nources outside of Containment leakage reduction -j program, In addition, the nystem in maintained _ full  ! of water and isolated from all other systems, which , would prevent relennes from containment. Daned on i the low probability of the valves being open and the system in closed outsido of containment, it in  ; acceptable that thene valven are not capable of being - nanually cloned following n SBO. The valves are included in the emergency renponso procedure to verify the valven are closed. , in the Slio proceduren, the CIVs that need to be verified closed are identified. Proceduro ECA-0.0, Loss of-AC Power, directs operatorn to ensura all of these valvon are closed using the control room > Engineered Safety Features (ESP) status pnneln which are DC powered. If any of the valven are not closed, it directs operators to nanually align the , componentn. i The question on when the excluded CIVn are oporated and testod was only discusend in the tolocon with regard to the valves that were excluded due to being normally-locked closed during-operation. Our locked  : closed valven are not operated or surveilled during power operation. In addition, mont of_theso valven do not have electrical Audication. Every valvo that receives an automatic containment isolation nignal , has electrical--DC powered indiention in the control room. The emergency procedure on lons of AC power verifien all .of the valvos that have thin indication are closed. NRC Q.6 Identify the assumptions and doncribe tha approach to the plant-specific reactor coolant inventory analysia. Page 6 of 8 _.a,__._-_.,._.a___.___..____._____.__._-- _ . _ _ _

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'.g UE-A.6              The assumptions used to verify the core would remain covered during an SBO event were RCS leakayc of 11 gpm                                                                                     ,

10 ppm identified (allowable por Tech Spoca) i gpm unidentifjed (allowable per Tech Specs) RCP Seal leakage of 100 gpta total 25 gpm per RCP 3 Letdown Lossen 167 ft 125 gpm for 10 min, until letdown isolation 3 RCS shrinkage due to cooldown of 2390 ft . Therefore, 30tal system losses for the 4 hour period are 6118-ft . Jotal volume availablg or to 23,726 cover top of fuel is 9290 ft .- Therefore 3172 ft gallons of margin exists'. NRC Q.7- Is there enough compressed air _to operate valves needed to cooldown the plant? UE A.7 The capacity of the nitrogen accumulators for'the Steam' Generator Atmospheric. Steam Dump Valves and AFW-control valves was examined to' ensure sufficient prewire is required to assure valve _ operations during the 4 hour coping period. The design nominn) pressure will-provide aufficient nitrogen for an 8 hour period with each ARV being stroked every 10 minutes, and each AFW control valve stroked 3 times per hour. The minimum _ allowed pressure will pt; ovide ai r. for 5 hours with the same - f requency of operation. Therefore,_ adequate backup air-capacity exists. p NRC-Q.8 Provide-the assumptions used__in the CST inventory calculation. UE A . 8 - _The question _was raised as to how Union Electric performed the calculstion which determined the-required Condensate Storage Tank (CST) Vo lutt.e . The q loads considered in our calculation are: l-L Decay heat removal (7.43,x-10g: BTU for 4 hours) l Sensible hgat removal from RCS for cooldown (1.13 x 10 BTU) Sensible heat removal from tha steam generator-(S/G) fluid Rostoration of S/G 1eveln to hot'zero power

                                                                              . conditions i

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• Attachment The removal of-decay heat and nensible heat from the RCS and S/Gs required approximately 91,C00 gallonn.

Restoration =of S/0 levels required approximately 40,000 gal 4onn. The calculation then adds a 20% margin:which brings the total required water volume to 158,000 gallons. This annumed an initial CST , temperature.of 120 F. No further actions were

                       - required since the current technical ^ specification limit on CST inventory is 281,000 gallonn, i

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