ST-HL-AE-2062, Forwards FSAR Revs for Sections 7.4.1,10.4.9,App 10A,Tables 10.4-3,7.3-15 & Figure 6.2.4-1 Re Starting Turbine Driven Auxiliary Feedwater Pump W/Trip & Throttle Valve,Not Steam Inlet Valve as Previously Indicated

Forwards FSAR Revs for Sections 7.4.1,10.4.9,App 10A,Tables 10.4-3,7.3-15 & Figure 6.2.4-1 Re Starting Turbine Driven Auxiliary Feedwater Pump W/Trip & Throttle Valve,Not Steam Inlet Valve as Previously Indicated

ML20215G490
Person / Time
Site:	South Texas
Issue date:	04/14/1987
From:	Wisenburg M HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
ST-HL-AE-2062, NUDOCS 8704170130
Download: ML20215G490 (27)

Text

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April 14, 1987 ST-HL-AE-2062 File No. G9.17 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 FSAR Revisions Concerning Sections 7.4.1, 10.4.9; Appendix 10A; Tables 10.4-3, 7.3-15: Figure 6.2.4-1 Attached are FSAR revisions which state that the turbine driven auxiliary feedwater pump will be started with the trip and throttle valve, not the steam inlet valve as previously indicated. This configuration has proven to start the turbine driven auxiliary feedwater pump reliably with no overspeed trip; and is also the preferable configuration in terms of draining condensate from the steam inlet line.

HL&P believes that conclusions previously reached in the SER remain valid. If you should have any questions on this matter, please contact Mr. J . S . Phelps at (713) 993-1367. g A

M. R. Wispnburg Deputy Prbject Man er JSP/yd

Attachment:

Revised FSAR Sections 7.4.1, 19.4.9, Appendix 10A; Tables 10.4-3, 7.3-15; Figure 6.2.4-1 8704170130 870414

{DR ADOCK 05000498 PDR Ll\nrc\ga. y tjli

ST-HL-AE-2062 File No.: G9.17 Ifouston 1.ighting & Power Company Page 2 cc:

Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Drive, Suite 1000 P.O. Box 1088 Arlington, TX 76011 Austin, TX 78767-8814 N. Prasad Kadambi, Project Manager A. von Rosenberg/M.T. Hardt U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771 Bethesda, MD 20814 San Antonio, TX 78296 Robert L. Perch, Project Manager Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue 1717 H Street Bethesda, MD 20814 Washington, DC 20555 Dan R. Carpenter Senior Resident Inspector / Operations c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 Claude E. Johnson Senior Resident Inspector /STP c/c U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 M.D. Schwarz, Jr. , Esquire Baker & Botes One Shell Plaza Houston, TX 77002 J.R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.W.

Washington, DC 20036 T.V. Shockley/R.L. Range Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 Ll\nrc\ga. Revised 2/3/87 i

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ATTACHMENT ST HL-AE. 2o6%

STP FSAR PAGE i OF a.9 41

2) RCP seal injection flov Q32.39

e. Condensate Storage and Transfer System  !

1) Auxiliary feedwater storage tank (AFST) level

• The description and design criteria for the essential monitoring indicators

.are described in Section 7.5 and Appendix 7B. 41 7.4.1.1 Auxiliary Feedwater Control. The A WS consists of three l41 motor-driven pumps and one steam turbine-driven pump, associated piping, valves, instruments, and controls as shown in Figure 10.4.9-1. The three i motor-driven pump trains and the turbine-driven pump train are started auto- l41 matically by the ESF Actuation System and ESF load sequencers, as discussed 2 53 below. All four pumps can be started manually from the control room or the Q32.16 ASP. Each pump feeds one SG through an individual auxiliary feedwater line.

Flow control is provided by individual, motor-operated regulator valves that l41 can be manually controlled from the control room or the Auxiliary Shutdown Panel (ASP), using the Qualified Display Processing System (QDPS), described 53 in 7.5.6. AW flow indication and SG level for each SG is provided in the control room and on the ASP.

Each AW pump may be remote-manually cross-connected in absence of a safety actuation signal to feed any combination of steam generators if instrument air 41 is available. Manual valve operability is also provided.

n e A W turbine driven pump is supplied with steam from SG 1D through the

( steam inlet valve.p th: :::- -inlet bypees. valve *'and the turbine trip throttle valve. The steam iglet valve and the-4 team inlet hyp;:e-valv; ::: b : th"-

is norma 11f@loset/"WA epe . they :lle-# steam flow to the normally-open*c.losed l

^

turbine trip throttle valve. These valves 44&Neeive open signals on an AW initiation. -Ihe st = inl:t velv: re :iv:: -it epen ri;nel th::rgh t * -- S deley (appr-estfeatelyC ;.: . ) . %ia-tim deley :lle": etter f1;; thrru;h th;' 51

-et = i .1 t-bypase-vatve-and4yper: crific: te ser:1::::: th; turb're t:-c A rp::d which 411 =: the-sur4&c ;:vur. : :: ::: =: p: d ::rtr:1 prie te th?-

steam--inlet v;17 epentagw Manual control of the steam inlet valve _ -*- *'

&olet-bypase--vel *&* and the turbine trip throttle valve is available in the Control Room and on the ASP.

Status indication is provided in the control room and at the ASP for the 41 motor-driven pumps, steam inlet valvef, turbine trip and throttle valve, regu-lator valves and isolation valves.

The AWS is described in Section 10.4.9. 2 Q32.16

1. Initiating Circuits The motor-driven pumps are immediately started on a two-out-of-four l low-low water level signal from any SG and are started by the ESF load sequencers following a safety injection (SI) signal or a 1DOP. The AW 41 valves are automatically actuated to their proper position by a

• Essential systems and components for safe shutdown.

(

7.4-3 Amendment 53 I

n - - - . - , .- - , - - - - - - - - , . - . . - - - - - - - - - - - - - - - - . . - - - - . - - - . - - - - - - -

ATTACHMENT STP FSAR ST-HL-AE aoba PAGE 5 OFp5 two-out-of four low-low water level signal from any SG or a SI signal. 2 Ac neted d:::, t k -  !".' turbine -eteam-inletwelve-opaning te ^1 yed 9 eeeure prep-r--turbine-speed-contro1F The flow to the SGs is not auto-Q32

.16 ]

matica11y provided after a 140P until a SG low-low water level signal or a SI signal is received. The QDPS controls the flow into the SGs through the A W regulator valves, within prescribed limits (see Section 7.5).

~

2. Logic l l

See Figure 7.2-16.

41

3. Bypass Control from the control room and automatic control are bypassed at the transfer switch panels when control is transferred to the ASP. This transfer of control is alarmed and indicated in the control room through the ESF Status Monitoring System (see Section 7.5.4).

4. Interlocks There are no interlocks.

5. Redundancy Four level sensors for each steam generator and three actuation trains 53 are provided for system actuation logic redundancy. Any two of the four 4g auxiliary feedwater pumps provide sufficient feedwater for safe. shutdown requirements. 2

6. Diversity The SI signal and SG water level signals are provided for actuation .' 53 diversity. AWS diversity is provided by motor-driven pumps and one turbino driven pump.

7. Actuated Devices Actuated devices are listed in Table 7.3-15, 51

8. Supporting Systems The Class 1E electric systems are required for AW control. Ventilation 41 support is required (see Section 9.4.8). The AFST is required (see Section 10.4.7).

9. Portion of System Not Required for Safety The ESF Status Monitoring System is not required for safety. $1 i

10. Design Basis Information Design bases for the AWS are that the operation will be controlled auto-matica11y by the Engineered Safety Features Actuation System (ESFAS) or i

7.4-4 Amendment 53 l

l

ATYACHMENT STP FSAR ST-HL AE 2c>to A PAGE t, OF a5

(

The AFWSs water supply is from the AFST which is designed to seismic Category I SC 3 requirements and the applicable codes discussed in Section 3.8.4. The AFST is designed to withstand environmental design conditions, including flood, earthquake, hurricane, tornado loadings, and tornado missiles. The AFST is designed to retain a sufficient quantity of water for AFWS use. The 31 AFST is designed such that no single active failure will preclude the ability to provide water to the AFWS. The AFW suction and discharge lines are routed separately to prevent coincident damage.

For vacuum protection, the AFST is provided with a water loop seal fabricated of safety Safety class Class piping physically 3 concrete structure.located within the AFST seismic Category I, breakers are provided. In addition, redundant non-safety vacuum 4 The AFWS is provided with control at the auxiliary shutdown panel in addition l39 to those in the control room so operation is possible in the unlikely event the control room is inaccessible.

10.4.9.4 Tests and Inspections. The AFWS may be tested and inspected while the plant is in operation. Only one pump at a time may be tested. A test line is provided on each pump discharge back to the AFST to allow for l31 performance testing of each pump.

Leakage can be detected by visual inspection and by loss of tank inventory.

l31 The AFWS will be tasted in accordance with Section 14.2.

l39 l 10.4.9.5 Instrumentation Application. The control logic for the AFWS is described in Section 7.4.1.1 and 7.3.1. l2 l45 The AFWS is capable of starting automatically and supplying the SGs with water required for decay heat removal. Each motor-driven AFW pump is started auto-matically by two out of four low-low water level signals from any SG, or by an automatic load sequencer signal based upon a LOOP or an SI signal.;fThe tu -

[ -driven AFW pump is automatically started by the opening of the 39 inlet valve, which is opened by a two of four low-low w evel REPLACE signal from a or by an SI signal. After the steam bypass valve opens, steam flows to

%vlTH , limited flowrate to permit tFW pump turbine throu bypass orifice at a bine to a erate to a speed at which the E NS ERT *A governor can assume control. After delay sufficient for the turbine governor to assume speed contr , e steam valve is opened and the turbine is allowed to a rate to normal operatin d. The turbine trip 51 and throttle valv pplied with the pump turbine, is a no open valve.

It receive

SI s onfirmatory open signal (SG low-low watsr level in . . or an and may be manually controlled form the control room or the iliary shutdown panel.f All AFV pumps may be manually controlled from the control room and the auxiliary shutdown panel. Status lights are provided at both locatiens to monitor the performance of each AFW pump. The two of four low-low water level signals in any SG or the SI signal close the SG blowdown 39 valves, sample line valves, and AFW crossover isolation valves, and initiate control of the AFW regulator valves by the QDPS. It also allows the stop 5 check valves to function normally. Thus on a LOOP, the motor driven AFW pumps start and recirculate water to the AFST until an SI signal or a two of four low-low water level signal in any SG occurs. Each AFW regulator valve may be l

I 10.4-31 Amendment 54 i

l I

ATTACHMENT ST-HL-AE N) b L PAGE r/ OF JL5 Insert "A"

....The turbine-driven A W pump is automatically started by the opening of the turbine trip and throttle valve (supplied with the pump turbine), which is opened by a two of four low-low water level signal from any SG or by an SI signal. The turbine trip and throttle valve may be manually opened from the control room or the auxiliary shutdown panel. The steam inlet valve, located upstream of the trip and throttle valve, is a normally open valve. It receives-a confirmatory open signal on SG low-low water level in any SG or an SI signal.

4 9

i t

Ll\nrc\ga.

o i

i h61e 10.4-3 hilmre Made Amm1 mis for the hadliar Pendustar W F1 sat Mstnad Failure Effsets numeriptism Safety Operut- Failure of Faihet am Systm Safety l of rw heetIan imutMode* Mode (s) Detectim heetice Casability thmeral Ramunks 4

151 Meter driven M pg W =us to start 1, 2 & 3 1)Fallstostart 1 & 2) 1) Ame - The other gerating (typical-1 in tinge sud provide M or steps nus- s. hmy stahs light Arv page will pivride ef the femr truime) to the SC wemme- aist stuma re- b. FJF unmitorise sanysste AFW flow, l51 les117 gnired (1only)

, c. Freemure Indicatian

• i

2) W start (via QFS) 2) Ame -If ArW is met re- I er failure to gaired tie effseted st, enw Arv line can be isolated Thublime driven M start and provide 1. 2 & 3 Falls to start s. Frassure Yealeselm Esse - The meter drigua 3' (hela de-castro ArW to SG D auto- eretgs nas- b. Flow Indicatim Arv pays will be oper- Si satically sing wous w- ating providing adegate gaired M ilaw.

ei o Open N M pay tambine trip ~, . *dan I 2&3 1) Fails elemed 1&2) 1) Ihmue - The notar driven lI 4 2,

j and timettle in13e 0c54514) serum 11y centrol stama W=Im to the er falls to s. Femitian ladiestle eye em faitle- b. Freemsre indicatim M pumps will be eper-ating providing ade {

.apmPacpanesud ' ArW turbine tiam e. air unmitarus Arv fla .

glmf (1 enly) j 2) h ile syse er 2) name - If M is ant If Heim Stamm 51 a fails to close rugsfred the lima can isolstiam is j m initiatim heisolatedbydQHD19 russired IcM143 j Mov cm be closed.

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mp >-4 i& O 4

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1. Famer geratism a 2. Startay j 3. Ant st a dby

4. Not slutdoim -

5. Cold shutdeim

6. Refueling

Table 10.6-3 (Cartiremd)

Failure Itide Armiveis for tie Amillary Feeduster Syste Flart Mlux! Failure Effects m Syste Safety 39 Safety Operst- Failure of Failure Drecriptim Martim w ility Ca eral Reserks Bartim im ptxte* Male (s) Detectim of Cm =--

"^ " '-

1,2&3 - D raii. C ' I # . L _

Steam Inlet Iypees islw r ""' "- ' * -h S ' e c ';i L ' s. Yalve positi m IH)l43 noruntly closed (depomerud) L 1"?d-.E To s% (_lont)

W -

-L {

inlicatim.

M im. --

.'"' ; 7-""-,,(

_wr m. su=.

51 I)ATFellsopeor : . 1 .- . ~ " 2 Ik.se - If fal e.- M ^ rapirvd fact e im  ; @ .- *- train can be 1so g{ i.% .m ov - o n y eruf a M t 1,2&3 I) Falls to op e 1 & 2) 1) Ikse - Mutor driven M Steam apply volve gange will supply adapete MN.0143 rrauelly stems to tle M m ccused er s. Vol w positi s indicatim M flow.

.sjeenk(depouered) pimp turbine. Also {4g c(g b. ESF emitmirg op4M prwides isolatim of tte steen line in (1only) ,

the evet of a line c. Steam Freneure Q break via plare ccuputer 5 2) Ihme - If M is rut if usin steam isols- ,,,

2) Falls to close tim is rapiiral

• s-e initiatim rapiired this line can "5 d, MN-0514 cm be 51 be isolated by MW-0019

• tripped.

s. Fceitim inficatim itse - Otler crose corswet Thane isivue could l51 To etsy closed I,2&3 Valve falls be used to allow Cross co m ect volw e b. ESF srunitorizg velves will le closed 39 or to cicae m open nornelly closed cross corewetion (typicale per AN sipal of tte AFW traire.

line)

I

1) Ihme -Ik flow will occur Normal positim AN ccstrol selve To regulate AFW 1,2&3 1) Falls closed 1&2) not specified 51 fr a this train, liourwr, flow or fails to s. Positim indicatim (typical- cue per AFW tie other trains will open cm b. Flow indicatica 7tA>

line) l initiatim c. ESF emitorirs prwide adequate AN flow. '

--i (1 mly)

2) Fails opm or D(I$ 'O fails to close 2) Ikue - If tle flow is art m initiatim rapiirei or it is excessiw L2k1 I $

the stop check isolation

> velve cm be closed

,vy Nh e

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2. Startup

3. Ikt etmulby

4. Ikt shutdae '

5. Cold stutdoun

6. Refueling

ATTACHMENT ST HL AE Jo 6d-PAGE 10 OF A5 STP FSAR s

consists of' suction piping, pump / driver combination, discharge piping, cross-connect piping between trains and test and recirculation piping, is l housed in a separate Seismic Category I compartment.

Pump pressure and flow testing is accomplished through a 3-inch diameter recirculation line connected to the 4-inch diameter main flow line downstream of the flow element. Flow through this line is isolated by a normally locked-closed globe valve downstream of the recirculation connection to the -

mainline. Opening this valve allows recirculation to the AFWST for pump testing.

10A.2.2 Component Description

1. Motor-Driven Pumps:

The motor-driven pumps are driven by AC-powered electric motors. Each motor receives power from an independent Class 1E l

power supply bus and its corresponding standby diesel genera-tor. The pumps are horizontal, centrifugal, multistage units.

I

2. Turbine-Driven Pump:

The turbine pump is a horizontal, centrifugal, multistage, noncondensing steam turbine-driven unit. A steam line connec-tion is taken from the Safety Class 2 section of the Steam 54 Generator D main steam line upstream of the main steam isola- ,

tion valve. The turbine steam inlet line is provided with 'I '

j remote manual isolation and throttle valves. The turbine dis-charge steam exhausts directly to atmosphere. Overspeed of the AFW pump turbine automatically trips the turbine. Once this

occurs, the mechanical overspeed trip latching mechanism must be manually reset in order to restore the turbine to an oper-able status. Power for all controls, valve operators, trip solenoid and other support systems is from the Train D Class lE DC system. The major support system is the lube oil pump and cooling system. The lube oil pump is direct driven off the turbine shaft. The cooling water supply for the turbine lube oil cooler comes from a first stage bleedoff point on the l.

turbine-driven pump, passes through the lube oil heat exchanger, and is discharged to a drain.

l

3. Piping and Valves y pq s 05 tM (e d The safety-related AFWS piping is manufactured and installed in i accordance with e ASME Code. Motor operated valves AF0048, AF0019, normallyAF0065[,

close +501437.

AF0085valve Motor operated and solenoid

-XMSGS valveis FV0143normally are open. Valves AF0065, AF0048 and F0085 are AC powered. Valves MS0143, FV0143, AF0019, and XM 14 are DC po red. Since motor-operated valves 7523, 752 , 7525 and 75 6 may be in any initial position prior to AFW actuation, the alves are assumed to be closed prior to actuation.

ATSO \H 3 ..

4 10A-6 Amendment 54

ATTACHMENT ST-HL-AE pow STP FSAR PAGE 11 OF 25 l

4. Auxiliary Feedwater Storage Tank The Seismic Category 1 auxiliary feedwater storage tank pro-vides water to the AFW pumps. It is a concrete, stainless steel lined, 518,000 gallon tank which has sufficient capacity to allow the RCS to remain at hot standby for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> followed by a 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> cooldown and an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> soak period at which point further RCS cooldown is performed by the residual heat removal system.

The AFWST is designed to withstand environmental design condi-tions, including floods, earthquakes, hurricanes, tornado load-ings, and tornado missiles. The AFWST is designed so that no single active failure will preclude the ability to provide water to the AFW system. Each train has a dedicated suction line from the AFWST to the AFW pumps. The water level in the AFWST is indicated in the control room as well as at the auxiliary shutdown panel. A low level alarm is also provided in the control room.

10A.2.3 Emergency Operation The AFWS is designed for automatic actuation in an emergency. Any of the following conditions automatically starts the three Class 1E motor-driven

! Pumps:

54 4

( 1. Two out of four channels showing low-low water level in any steam generator

2. Safety injection signal

3. 4.16 kV bus undervoltage. The AFV pump is started in conjunction with diesel generator starting and load sequencing.

Water is not automatically fed to the steam generator until condition 1 or 2 above exists.

The turbine-driven auxiliary feedwater pump starts automatically on any of the following signals:

1. Two out of four channels showing low-low water level in any steam generator

2. Safety injection signal (Aone-inchbypasslinewithanormallyclosedsolenoidoperatedvalve(FV0143) j and orifice is provided around the steam inlet valve (MS0143). This bypass valve (FV0143) opens upon receipt of either of the above signals to supply steam to the turbine and allow the turbine to reach governor control speed, l

After a time delay to allow governor control speed to be reached, the steam inlet valve is opened which allows rated steam flow to the turbine. This arrangement precludes an overspeed trip due to excessive steam flow prior to governor warmup. This bypass line is not dependent upon AC power to operate.

N l

10A-7 Amendment 54

ATTACHMENT ST HL AE- 26W PAGE / AOFf5 STP FSAR i

Component Test Test Frequency ~

e Non-Automatic Valve Position Verify position at least every 31 days e Automatic Valve Actuation Verify actuation to correct position during each refueling shutdown e Motor and Turbine Driven Pump Verify pumps start on actuation Actuation signal during each refueling shutdown e Train Operability Verify ability to establish flow path to each steam generator following cold shutdowns greater than 30 days 10A.3 METHODOLOGY This section presents the step-by-step procedure followed in performing the AFWS quantitative reliability evaluation.

10A.3.1 Sys'cem Review In the first step, the various drawings, P& ids, and schematics representing 54 'T the AFWS were examined. Special attention was given to identifying: )

1. Instrumentation systems required for system actuation -

2. Fluid systems connected directly or indirectly to the AFWS

3. Power sources for each component

4. Any obvious single-point vulnerabilities. ,

The reliability information described in Appendix III of NUREG 0611 was then appraised, and AFVS studies of other facilities were reviewed. With this information, the evaluation boundaries were established. -

10A.3.2 Fault Tree Development and Quantification Fault trees are constructed from the P& ids. These trees include component failures (mechanical and control circuit), test and maintenance outages, and human errors (from testing, maintenance and accident response). The fault trees are constructed using a segment level approach. A segment is defined as the piping section between two points of intersection with other pipe seg-ments. Failures within the segments are characterized and developed into the

j fault trees. The fault trees developed for each scenario are presented in

/ Figure)( 10A-3.iv len . A table to identify the codes used in the fault trees is shown in Table 10A-5.

Quantification of the AFWS fault trees is done by two computer codes, GRAFTER and WESCUT. Refer to Section 10A.3.5 for a description of these code.s. . "}

10A-10 Amendment 54

ATTACHMENT STP FSAR ST HL-AE- acLA PAGE / 30F 45 Compared to other Westinghouse NSSS plants evaluated in NUREG-0611, the South Texas AFVS contains a greater number of motor-driven pump trains (3 versus the typical 2). This redundancy reduces the likelihood of AFWS unavailability during a IREV/IDOP event. -

For this reason and the local manual crossover capability, the qualitative reliability rating given the South Texas AFWS is comparable to that of other high reliability Westinghouse NSSS plants as reported in NUREG 0611.

10A.4.1.3 Loss of Main Feedwater with Loss of all AC Power The major feature of this initiating event is the total dependency of the AFWS on steam power. Low and medium reliability classifications under this event are generally due to systems having AC power dependencies in the steam turbine-driven pump train. Such dependencies may include lube oil cooling, AC I

power to steam turbine admission valves, or air-operated valves which fail closed on loss of air. Those systems characterized as having a relatively high reliability'are usually automatically actuated and have no potentially degrading AC power dependencies (except HVAC).

When comparing the STP AFWS to the NUREG-0611 plants which have a high reli-ability characterization, the STP design has comparably high reliability because the turbine pump train has no AC dependency in order to function. 54 However, since no credit is taken for the steam turbine driven pump to serve other than SG-D (due to absence of control room activated crossover capability and the requisite manual actuation of the step check isolation valves in the other trains), the South Texas AFWS is rated slightly lower than some of the 50g ,q highest rated other Westinghouse NSSS plants as reported in NUREG-0611 (refer j to Figure S6A-6-) . As noted earlier, it is possible to manually initiate i

crossover from outside the control room if the need should ever arise. The turbine driven pump is qualified for operation in the environment resulting '

from a loss of HVAC.

I 10A.4.1.4 Qualitative Comparison with Other Designs 4

Figure 10A-)(is a reproduction of the reliability characteristic chart pre-sented in NUREG-0611 for AFWS designs in plants using the Westinghouse NSSS.

l An added row presents the results of a qualitative evaluation of South Texas l

AFWS reliability. The figure shows the relative reliability ranking of South l

Texas AFWS for each of the three cases studied and compares these results to those obtained by the NRC. This qualitative evaluation is included to com-plement the results of the quantitative analysis.

10A.4.2 Quantitative Evaluation The quantitative characterization of the South Texas AFWS reliability is i

developed using the methods and data provided in NUREG-0611. The system's conditional unavailability is quantified for three initiating events: LMFW, IRIV/IDOP and IRFV/IAAC. System unavailability is associated with hardware failure, human error, and test and maintenance downtime.

10A 14 Amendment 54 t

l

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ATTACHMENT -

STP FSAR ST HL-A L ab@ . ._

R GE/- 0F a5 10A.4.2.1 Quantitative Results ' .

i

-la The results of the quantitative evaluation are presented in Table 10A-4 2.9 % M System unavailability for the IMW and IMW/1DOP events is approximately O. ; ', anLO.00 ~ per demand, respectively. Even for the IMW/1DAC event, b gY where all AC power is lost and the system is totally dependent on the steam

-2 turbine drivenispump unavailability approximate to supply1water to the steam generators, the system Je 9 UO " per demand. These results demon-i strate that the South Texas AW designs and the USNRC acceptance criteria of 10 8 design is reliable when compared with IMW transient (Ref. 5). to 10 4 per demand for the 10A.4.2.2 Failure Modes

! There are many.possible combinations of random hardware failures, component i

unavailabilities in the unavailability due tooftest theorAWS. maintenance, and human error which can result

. Since each system component (e.g., pump, valve) generally has a different failure rate, there are certain combinations of failure modes that contribute significantly more to the total unavailabi-lity of the AWS than others. These are the most significant failure modes.

Unavailability per demand of each of the possible combinations of failt.re-modes is computed by the computer code "VESCUT".

Once the unavailabilities associated with each minimal cutset have been computed, their percentage t

i contribution failure modes to identified.

total AWS unavailability can be determined , and significant 54 minimal cutsets based on Boolean expressions.The In general, higher-order AWS reliability eva cutsets contribute less.to the top event than do lower order cutsets if the failure rates of the basic events are similar. With four separate pump trains, the aggregate of fourth-order cutsets (representing various combina-tions of pump and valve failures affecting different trains) contribute significantly to the failure of the entire AWS. Higher order cutsets (e.g.,

fifth-order) involve other basic events with much smaller failure rates, and their aggregate contribution to total A WS unavailability is numerically small.

The following sections present a summary of failure modes associated with the IMW, IEW/IDOP, AND IMW/14AC failure scenarios.

10A.4.2.2.1 Imss of Main Feedwater (Case I)

N(r . 0_ m JQ 1M W scenario (Case I), the A WS unavailabilityq was calc fourth-order cue dominant contributors to system unavailability a which motor-driven pumps B an ue to hardware faults. Train A pump is able due

[ j, valve in Train D fails.

1 Othe ance, and a motor-operated failure (either Tr=" ; or ), s include combinations of a pump a motor-opera failure in Trdin D, a motor valve failure in Train B or C (the oppos n which the

. ( ilure occurred) and the Train A pump unavailable due to maint E.s Ivm i m'tely a 4E-08 -dar and co cutset desgd es n.-

.Luve nas a cutset probability of approxi-el 1.5% to the system unavailability.

( .

Because e vidual cutset has a proba g a cutset contributor is dominant.

, 9 -- e the other cutsets, ~~

j 10A-15 Amendment 54

ATTACHMENT ST-HL-AE ao,> r INSERT A ME /60F35 For the LMFW scenario f calculatedas2.9x10gaseI),theAFWSunavailability.was unavailability are fourth-order The dominant cutsets. contributors to system The dominating cutset is the motor-driven pumps B and C fail due to hardware faults Train A pump Train D is unavailable fails. Thisdue to. maintenance, and the governor va,lve in cutset probability is approximately 7.8 x 10-8 and contributes 2.7% to the system unavailability. Other dominating contributors include combinations of a pump failure (either Train B or train C),inawhich motor-operated the pump failure valve failureoccurredin Train B or C (the opposite Train D fails, and the Train A pump is un)a,vailable due tothe governor valve in maintenance. Each of probabilityof7x10-ghesefourth-ordercutsetshasacutset and contributes approximately 2.4% to the

' total AFWS unavailability.

9 0

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Va\9f ATTACHMENT ST.HL. AE. acA

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4iewswrMen the basic events are examined, approximately ')( percent of the j failures of the system can be attributed to the Train A pump's unavailability i due to maintenance in combination with other failures. (This result is l \ expected based on the restrictions applied in the analysis). Other dominant, basic events arehthe failure to start and run of motor-driven pumps in Trains -

B and C (304%)

discharge lines,ofand the motor Trains B and operated C (25 A4).valves (failing s...-__ ..

to...u..

open).te in the pe. us . . . -

;c;;; ;h ; ce..;. 'h t

20.1 ;; n ;..; .ul ^;.; ye&s.u. . . .y o wl . 1, me C ..

-": 1 .y.i.= uu. .il.Lii uyj.

One first order cutset was determined for the IRW event (failure of the AFST). However, the failure probability is 3.6E-08 and its contribution to system unavailability is approximately one percent. Thus, the conclusion can be drawn from this analysis that the South Texas AWS is highly reliable in the event of a loss of main feedwater.

10A.4.2.2.2 Loss of Main Feedwater Coincident with Loss of Offsite Power i

s.; r ja-5/d )

i For the IRW/ LOOP scenario (Case II) (unavailability equal to *3.5" C fuj , most of the failure combinations involve pump or valve hardware failures coupled with failure of the diesel generators (diesel generator operation is required 6 during a loss of offsite power). The up i wuusu.s uvuu i'..;ing u /T.!O

(

" m;;1

M11t; : : - k i-

• i-~ -f - : di; el ,, nere ur.,~f_ilin , ;fu T .iu. L *

nd 0; -10. . . 1.. f;ilm_. i.. Trair " : d th; T uin t. purp un:7111 ^1 4 l

in t ~~ = - The top four cutsets have a probability of d"-

contri-

• ^

547 r

bute approximately 5.7 percenu ota navailability. The remain-ing two cutsets have probabili .1 -

E-06 and contribute '

apprpximately four to the unavailability. Other a inations determin e evaluation include failure of three diesel generators ds

! .G . . I.11 re in O. .L=.m umbine 6tiveu pump train u.

(-----31 1.

) When the basic events involved in these4 failures are examined, the dominant contributors are the diesel generators (??.? pr::nt) followed by Train A motor driven pump unavailable due to maintenance (59)(l)/and the motor i operated valves in Train D y....u. each). These basic events are coupled with other failuresn[fcutsets e . ~, that contribute that percentage to the I system unavailability, J g h g .J he) ydvs. (317.h From this analysis, it can be concluded that the failure of the diesel genera-tors and not an actual AWS failure is the most important factor affecting l AWS availability following a loss of main feedwater coincident with a loss of i offsite power. , m 10A.4.2.2.3 Loss of Main Feedwater Coincident with Loss of All AC Power l

-3 l 8 A,D g{AWS unavailability

.fr 2/d> is attributablefortothe anyIRN/iDAC hardwarescenario (Casetest related failure, III) (unavailability or maintenance=

l unavailability, or human error that could disable Train D, since this is the i only AW train which can operate independently of AC power. The percentage contribution of each to total AWS unavailability for Casa III is as follows:

l Train D motor.-operated valve failure G T , operator error in failing to reset

! the trip and throttle valvesgor failing t close a manual valve af ter test (/37.\

ateiW-). and the unavailability of the turbine driven pump due to maintenance

-13) . - (,15 7.h ,

l (31 1

(3M #

10A-16 Amendment 54 t __ _____ __ ___ _ . _ _ _ _ _ _ _ _ _ ,_ _ _ . _ _ _ _ . . _ . . _ ___ ___

ATTACHMENT ST-HL- AE. a c>too -

INSERT B I PAGE I 7 0F2c; 1

The top three cutsats contributing to AFWS unavailability are combinations of two diesel generators failing (for Trains B and c) with the Train A pump unavailable due to maintenance and a valve failure i 2.8 x 10-g Train D. The first cutset has a probability of )

and contributes approximately 9.2% to the total system unavailabigityandthenexttwocutsetseachhaveaprobabilityof 1.66 x 10~ and contribute 5.4%. Other top failure combinaticas determinedcoupled generators in the evaluation include with a valve failurefailure of three in Train D. diesel i

e a

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ATTACHMENT ST-HL-AE. actox STP FSAR ._PAGE lY OF as

(

TABLE 10A-1

, Component Basic Event Failure Probabilties*

1. Check valve. Failure to open.

. AF0122, AF0120, AF0121, AF0119, AF0011, AF0058, AF0091, AF0036 1 x 10'4/dg ,)

2. Automatic actuation signal.

ASA, ASB, ASC 7 x 10 s/d

3. Manual backup signal.

(Conditional probability given automatic signal fails)

MSB, MSC, MSD 1 x 10 2/d

4. Flow element plugging.

FE7526, FE7524, FE7523, FE7525 (This failure rate was taken from VASH-1400 for plugging of the flow orifice Table III 4-1). 3 x 10'*/d

5. Cate valve. Plugging contribution.

, i AF0014, AF0012, AF0024, AF0093, 54

{ AF0061, AF0059, AF0053, AF0095, AF0080, AF0078, AF0073, AF0096, AF0041, AF0043, AF0031, AF0094 1 x 10~4/d gjf)W

[5'. Solenoid v fve failure.

FV 3 Mechanical componen 1 x 10 af 3

Plugging contrib on 1 x 10" /d (WASH-1400)

Local control cuit 6x s/d Total 7. x 10 s/d,,s, ,

e l

• Data Source, NUREG-0611 except as noted. -

• • The median value presented here was calculated from the mean value and the

,( variance contained in Reference 6.

l 1

10A-19 Amendment 54 l

t __ __ -

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ATTACHMENT ST HL-AE. pd. A r OF 05 PAGE le STP FSAR TABLE 10A-1 (Continued)

Ccaponent Basic Event Failure Probabilities *

- $, Motor-operated valvt, failure to open.

)

AF0019 AF0065, AF0085,'ftsettWl AF0048 W7523, W7524, W7526, W7525 Mechanical components Plugging contribution 1 x 10 s/d Control circuit (local) 1 x 10**/d Total , 6 x 10 s/d 7.1 x 10 s/d

7. K . Motor-driven pump.

MPA02, MPA03, MPA01 Mechanical components Contial circuit (local) 1 x 10 s/d Total 7 x 10 s/d 8 x 10 s/d

8. M Turbine-driven pump.

MPA04 Mechanical Components .

Overspeed Trip: 1 x 10'8/d

' Solenoid Valve Failure 7.1 x 10 s/d

{;.. n._ 7) .

54 Orifice Plugged 3 x 10**gd-( Total 8.4 x 10 s/d

9. X Motor-operated valve..

.- L1.Z;14 Plugging contribution.

McW 3 1 x 10'*/d po, X Auxiliary feedwater storage tank (unavail-ability per demand estimated from that 3.6 x 10 s/d

? giver. for condensate storage tank in WASH-1400).

)), K Diesel generator. . ,

DG13 DG12 4.8 x 10*8/d DG11 4.8 x 10*8/d l 4.8 x 10'8/d

{

The fromhardware Ref. 3. Total failure rate of diesel-generators (4 x 10*8/ demand) is taken diesel generator unavailability is the sum of unavailabilities due to hardware failure, test, and maintenance; i.e.,

total unavailability - 4 x 10'8 + 1.9 x 10 s + 6.4 x 10 s = 4.8 x 10*8 (Refer to Table 10A-2).

(2.. N Covernor Valve.

Plugging Coptribution i

n hnt e.aA a..y ns.A s 1 x 10',4/d Iy ab /al Co. hrs \ ChsdA Usssh 4,5 go"*/ d TM 7 1

• so'*/cl

(*)d - demand l

10A-20 Amendment 54

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ATTACHMENT --

STP FSAR ST.HL-AE- a fe L P.A.GE 2cOF ;t.5 TABLE 10A-2 Unavailability of Components Due to Testing or Mainte' nance Hrs / . Test / Hrs /

Component Test Yr Maint. StestI ") Saint (b)

Pump B, C, D 1.4 4 19 6.39 x 10'*/dI *) 5.8 x 10 s/d Valve 7 ...

2.1 x 10 s/d Diesel 1.4 12 21 Generator 1.9 x 10 s/d 6.4 x 10 s/d Pump A 1.4 -1 4 336 6.39 x 10~4/d 1.03xION/dId) 58 (a) N test - (# hrs / test)(stests/ year) [See NUREG-0611,' Table III-2)

(whrs/ year)

(b) Saint.-(0.22)(whrs/maintenanceactivity) [See NUREG-0611, Table III-2]

720 (c) d - demand

[ (d) See explanation in Section 10A.3.4.1.3 10A-21 Amendment 54

STP FSAR ATTACHMENT ST-HL-AE. p.otos

(. PAGE Gl OF 2,5 TABLE 10A-4

, AWS Unavailability (per Demand) .

54 IRN IRW/IDOP

~

INW/LOAC Total M g,n ,in .- r, t , 3,7 2* 30

.3.0 5 8 $ 3.13

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10A-23 Amendment 54

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