ML20217N085

Summary of 980303 Meeting W/South Texas Project Re long-term Resolution of Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant System. Proprietary & non-proprietary Handouts Provided by Licensee Encl

ML20217N085
Person / Time
Site:	South Texas
Issue date:	04/06/1998
From:	Alexion T NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
Shared Package
ML20013H289	List: ML20217N085
References
IEIN-88-008, IEIN-88-8, TAC-M93822, TAC-M93823, NUDOCS 9804080322
Download: ML20217N085 (46)

Text

tro -499 1 pweuq% UNITED STATES i

T* * [' ) S- NUCLEAR REGULATORY COMMISSION -

'T < wasuswoTow.' o.c. asses.eeos

• • • • • April 6, 1998 LICENSEE: STP Nuclear Operating Company (STPNOC)

FACILITY: SOUTH TEXAS PROJECT (STP), UNITS 1 AND 2

SUMMARY

OF MARCH 3,1998, MEETING ON LONG-TERM RESOLUTION OF BULLETIN 88-08, " THERMAL STRESSES IN PIPING CONNECTED TO .

REACTOR COOLANT SYSTEMS,"(TAC NOS. M93822 AND M93823)

On March 3,1998, the NRC staff met with the licensee and representatives from Westinghouse on the above subject. Meeting attendees are listed in Attachment 1. The non-proprietary meeting handout provided by the licensee is included as Attachment 2. The proprietary meeting handout provided by the licensee is in Attachment 3 and is being withheld from public disclosure.

The licensee indicated that the information in the proprietary meeting handout had previously been submitted to the staffin various topical reports. The NRC staff had previously reviewed these topical reports and agreed that the proprietary infamation in these reports would be withheld from public disclosure in previous correspondence.

The licensee indicated that the unisolable sections of piping connected to the reactor coolant system at STP (related to the bulletin) are the normal and altamate charging lines, the auxiliary spray line, and the residual heat removal (RHR) lines. The licensee presented analysis which

. concludes that the structural integrity of the charging lines would not be challenged when subjected to isolation valve leakage over the life of both units. They also pointed out that a major l difference _between STP and Fariey is that at STP the charging system is separate from the safety injection system and the charging flow is preheated.

in addition, since STP has two charging flow paths (normal and attemate) and since only one is j used at a time, on a rotating basis, the licensee calculated that 10 years of operation at normal operating pressure and temperature for the Unit 1 charging lines will be reached in the year 2009  ;

(the NRC and the licensee had previously reached an interim agreement that charging line piping integrity is ensured for 10 years of operation at normal operating pressure and temperature).

The licensee also indicated that the structural integrity of the auxiliary spray line is bounded by the charging line analysis, and that leakage in the RHR lines would not result in pipe cracking due to the absence of a thermal gradient in the unisolable piping.

The NRC staff indicatid that it did not have any immediate concems regarding the licensee's plans not to reinstall leakage monitoring instrumentation during the upcoming Spring 1999, Unit 1 refueling outage. Regarding long-term resolution of Bulletin 88-08, the staff provided preliminary I

l 9004080322 980406 m M!C Hi?~CEaliER 00Py PDR ADOCK 05000498 4 0 .. . PDR ij t -.  ;

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$ 2 feedback on the assumptions and applicability of the analyses presented and indicated that following the meeting, it would consider the information presented and provide a formal list of additional information needed to bring the long-term resolution to closure, if needed.

b

<f sw .

AuerJ Thomas W. Alexion, Project Man er Project Directorate IV-1 Division of Reactor Projects lilliV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499 Attachments: As stated cc w/atts 1 & 2: See next page l

1 I

.: 1 L _____________ i

84, T

feedback on the assumptions and applicability of the analyses presented and indicated that following the meeting, it would consider the information presented and provide a fonnal list of additionalinformation needed to bring the long-term resolution to closure, if needed.

ORIGINAL SIGNED BY:

Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499 Attachments: As stated cc w/atts 1 & 2: See next page DISTRIBUTION:

HARD COPY E-MAIL w/all atts . SCollins/FMiraglia (SJC1/FJM) KManoly (KAM)

Docket File BBoger (BAB2) MHartzman (MXH)

PDIV-1 r/f EAdensam (EGA1) LLund (LXL) w/atts 1&2 only CHawes (CMH2) RWessman (RHW)

OGC TMartin (SLM3) JHannon (JNH)

PUBLIC TAlexion (TWA)

ACRS Document Name: STP03398.MTS

'OFC PM/9M( LA/PD4-1 BC/EMEB\ D/PD -)

NAME TAlexih CHa N RW 'J.Har( or' DATE Ok/9 ) MS/98 7 / I /98 / h/98 COPY EhTNO YES/NO YES/NO YESh "

V OFFICIAL RECORD COPY i

.\ \

Cb\

Y i

( .. ; . s a^1 i

South Texas, Units 1 & 2

( STP Nuclear Operating Company _

cc:

Mr. David P. Loveless Jack R. Newman, Esq.

Senior Resident inspector Morgan, Lewis & Bocklus U.S. Nuclear Regulatory Commission 1800 M Street, N.W.

P. O. Box 910 Washington, DC 20036-5869 Bay City, TX 77414 Mr. Lawrence E. Martin

' A.' Ramirez/C. M. Canady Vice President, Nuc. Assurance & Ucensing City of Austin STP Nuclear Operating Company Electric Utility Department P. O. Box 289 721 Barton Springs Road Wadsworth, TX 77483 Austin, TX 78704 Office of the Govemor Mr. M. T. Hardt ATTN: John Howard, Director Mr. W. C. Gunst Environmental and Natural

' City Public Service Board Resources Policy P. O. Box 1771 < P. O. Box 12428

. San Antonio, TX 78296 Austin, TX 78711 Mr. G. E. Vaughn/C. A. Johnson Jon C. Wood Central Power and Light Company Matthews & Branscomb One Alamo Center P. O. Box 289 Mail Code: N5012 106 S. St. Mary's Street, Suite 700 Wadsworth, TX 74483 San Antonio, TX 78205-3692 INPO Arthur C. Tate, Director .

Records Center Division of Compliance & Inspection 700 Galleria Parkway Bureau of Radiation Control Atlanta, GA 30339-3064 Texas Department of Health -

1100 West 49th Street Regional Administrator, Region IV Austin, TX 78756 U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Jim Calloway Arlington,TX 76011 Public Utility Commission of Texas Electric Industry Analysis D. G. Tees /R. L. Balcon; P. O. Box 13326 Houston Lighting & Power Oo. Austin, TX 78711-3326 P. O. Box 1700 1 Houston, TX 77251 Judge, Matagorda County - .

Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414 Mr. William T. Cottle President and Chief Executive Officer .-

STP Nuclear Operating Company -

South Texas Project Electric Generating Station

,;, 1 P. O. Box 289 -

4 Wadsworth..TX 77483 4

MEETING BETWEEN STP NUCLEAR OPERATING COMPANY AND NRC LONG-TERM RESOLUTION OF NRC BULLETIN 88-08. " THERMAL STRESSES IN PIPING CONNECTED TO REACTOR COOLANT SYSTEMS" March 3,1998 Name Oroanization R. Wessman NRC K. Manoly NRC M. Hartzman NRC L.Lund NRC E. Debec NRC T. Alexion NRC M. McBurnett STPNOC M. Kanavos STPNOC S. Patel STPNOC P. Walker STPNOC D. Roarty Westinghouse P. Strauch Westinghouse

)

ATTACHMENT 1

\

NRC Bulletin 88-08 l

" Thermal Stresses in Piping Connected to Reactor Coolant Systems" 1

• , d ATTACHMENT 2

V NRC Bulletin 88-08 '

" Thermal Stresses in Piping Connected to <

Reactor Coolant Systems"

't

. NRC Bullatin 88-08

• " Thermal Stresses in Piping Connected to Reactor Coolant Systems" AGENDA a Management Overview (M.E. Kanavos) e Why Pipe Cracking at STP is Unlikely e Chronology - NRC Sulletin 88-08 e Desired Conclusion a Westinghouse Non-Proprietary Presentation (P. Strauch)

WCAP 11786 Analysis e Farley SI Line Cracking

• Farley Flow Diversion Test

. Farley Stress and Fatigue Evaluation

. Farley Crack Stability and Leak Rate Evaluation e Farley Conclusions a TASCS Program

. Turbulent Penetration Length Lyp e Turbulent Penetration Thermal Cycling Length Lu

. Location of Safety injection Line Cracks

)

)

e Farley SI Cracking versus TASCS Simulation Testing I e TASCS Approaches to Determine Cyclic Frequency a Application of TASCS Methodology to STP e Charging Lines e Status of Westinghouse Plants Regarding Charging Lines I e RHR Lines a Application to TASCS Methodology to Farley SI Line Cracking incident

• Recent SI Failures BREAK l 5 Proprietary Presentation (D. Roarty)

• Example Calculations 1

.. NRC Bullotin 88-08 1

V " Thermal Stresses in Piping Connected to Reactor Coolant Systems" Why Pipe Cracking at STP is Unlikely

)

i a Normal Charging and Alternate Charging Lines

• STP charging system is separated from Si system.

• Charging flow is preheated.

• Stratification is inconsequential.

• Piping stresses are below endurance limit where cycling is postulated.

• Two charging flow paths available for normal and alternate use. I

• Monitoring would not be required until year 2009, based on current NRC approval and actual plant operating history.

NORMAL CHARGING

-><--h XCV0003 XCV0002 N

XCV0001'

@ 560'F

$ - LEAK

~  !.

! ALTERNATE CHARGING

' Q*

M4 XCV0006 XCV0005 M

XCV0004

% h m ss0 r xcyoor

NRC BULLETIN 88-08

" Thermal Stresses in Piping Connected to Reactor Coolant Systems"  !

Why Pipe Cracking at STP is Unlikely a Auxiliary Spray Line

. Bounded by Charging Line Analyses a Residual Heat Removal Lines (RHR)

. Piping Layout is NOT conducive to Thermal i Stratification.

. STP Monitored data suggests unisolable portion stays ,

HOT, therefore, stratification is not likely. 4

. ' Leakage would not result in pipe cracking due to absence of thermal gradient in unisolable piping.

1

)

I 1

l y

.- NRC Bullstin 88-08

" Thermal Stresses in Piping Connected to Reactor Coolant Systems" Why Pipe Cracking at STP is Unlikely a CONCLUSION Through analyses supported by monitored data, STP has demonstrated that the Normal Charging lines, the Alternate Charging lines, the Auxiliary Spray lines, and the RHR lines are not likely to crack due to valve leakage as discussed in NRC Bulletin 88-08. i l

~

SOUTH TEXAS PROJECT CHRONOLOGY

( REGARDING NRC BULLETIN 88-08 SEPTEMBER 1988: HL&P SUBMITS SYSTEM REVIEWS TO NRC JANUARY 1989: HL&P SUBMITS WCAP-12108 FOR RHR LINES TO

-NRC FEBRUARY 1989: HL&P INFORMS NRC OF UNIT 2 NDE/ MONITORING NOVEMBER 1989: HLikP INFORMS NRC OF UNIT 1 NDE/ MONITORING SEPTEMBER 1990: H'.&P SUBMITS WCAP-12598 FOR CHARGING AND AUXILIARY SPRAY LINES TO THE NRC.

NOVEMBER 1990: AL&P SUBMITS WCAP-12598 FOR CHARGING AND AUXILIARY SPRAY LINES TO THE NRC SEPTEMBER 19'J2: NRC INFORMS HL&P THAT MONITORING REMOVAL MAY HAVE PdEN PREMATURE.

NOVEME':R 1993: HL&P SUBMITS WCAP-12598 SUPPLEMENT FOR CHARGING AND AUXILIARY SPRAY LINES TO THE NRC.

APRIL 1994: NRC INFORMS HL&P OF ACCEPTABILITY OF NEAR TERM OPERATION OF CHARGING AND AUXILIARY SPRAY LINES SEPTEMBER 1994: EPRI SUBMITS TASCS REPORT TO THE NRC FEBRUARY 1996: NRC ISSUES FIRST SER REGARDING STP SUBMITTALS AND TASCS REPORT JULY 1996: HL&P SUBMITS RESPONSES TO FIRST SER

' MARCH 1997: NRC ISSUES SECOND SER REGARDING STP SUBMITTALS AND TASCS REPORT JANUARY 1998: NRC/STP/W PHONE CALL WITH AGREEMENT TO

' MEET AT NRC OFFICES

0 FARLEY UNIT 2 SAFETY INJECTION LINE CRACKING INCIDENT VO51 B

/ N

[

(r ~

= --

/

]

CRACK LOCATION 6" SI LOOP B COLD LEG COLD LEAKAGE A T A SUFFICIENTL Y HIGH FLOW RA TE CAUSED SEVERE STRA TIFICA TION AND CYCLING THA T RESUL TED IN CRA CKING IN THE UNISOLABLE PIPE.

I f

l l

]

FARLEY UNIT 2 TEMPERATURE MONITORING RESULTS l

I

• MONITORING LOCATION ABOUT 6 UD FROM COLD LEG 4

)

. FIVE RTDs AROUND CIRCUMFERENCE, AT 45 DEG. INTERVALS e

HIGH DELTA T (215 F) BETWEEN TOP AND BOTTOM OUTER WALL e LARGE FLUCTUATIONS AT BOTTOM RTD TOP j 74 F,12 CYCLES / DAY (120 MINUTE PERIOD) 45 F,98 CYCLES / DAY (14.7 MINUTE PERIOD) gg g  !

19 F,220 CYCLES / DAY (6.5 MINUTE PERIOD) j

)

BOT 500 WhW VY + f s "' M\D l &

W h y ff* & & + f% f Pf '

y y s y A f  % % ^

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10.7 10.9 11.1 11J , 11 A 11.7 11.9 11.1 113 115 12.7 6

1 I

d I FLOW DIVERSION TEST THAT CONFIRMED LEAK SOURCE l

I BORON INJECT.

SURGE TANK THIS VALVE WAS OPENED (Pm)

TO DIVERT LEAK FLOW TO BORON INJECTION SURGE TANK ,

CHARGING

^

LINES CRACK LOCATION ,,

., k, j

/ "7 BORON l '

I-t+v: $ . , ,

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e, 1 .

I f I ^

VM VM CHARGING l l PUMPS RCS COLD LEG 2600 PSIG l LOOP B 2265 PSIG 2 1" LINE l n Vm +-

LEAKING VALVE 1

NOTE: ARROWS INDICATE DIRECTION OF LEAK FLOW DURING TEST.

FLOW DIAGRAM IS SIMPLIFIED FOR ILLUSTRATION PURPOSES. j l

l t

c.

FARLEY FLOW DIVERSION TEST FOLLOWING FLOW DIVERSION:

. THERMAL CYCLING ENDED

. BORON INJECTION SURGE TANK LEVEL INCREASED AT A RATE OF 1.5 GPM nao

g "

nos _- _1

'Ter ff 4ao h Mk [ I sse **\ g>" ,

- Leer a uma sInEM soo

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=\ f V" V a.o .

NT tM sao .

too r 12.5 13 13.4 '93 2 14.2 14.8 15 I nur m

FARLEY UNIT 2 SAFETY INJECTION LINE 1988 EVALUATION OF CRACKING INCIDENT EVALUATION DOCUMENTED IN WCAP-11786 CONCLUDED THAT THE OBSERVED TEMPERATURES COULD HA VE INDUCED STRESS CYCLES LEADING TO FATIGUE CRACKING CRACK WOULD HAVE REMAINED STABLE UNDER MAXIMUM POSTULATED LOADING l I

j

1988 FARLEY STRESS AND FATIGUE EVALUATION 4

• WESTINGHOUSE EVALUATED THE ELBOW WELD JOINT UNDER THE OBSERVED THERMAL TRANSIENTS (3D "WECAN" ANALYSIS).

• FATIGUE USAGE OF 1.0 WAS REACHED IN 2 TO 4 YEARS.

• CRACK PROPAGATION IS ESTIMATED TO OCCUR AT 1 TO 2 YEARS.

• INITIATION AND PROPAGATION IS ESTIMATED TO OCCUR AT 3 TO 6 YEARS. '

• PLANT HAD BEEN IN OPERATION FOR ABOUT 6 YEARS PRIOR TO  ;

CRACKING INCIDENT.

RELEVANT TESTING FROM ELECTRIC POWER RESEARCH INSTITUTE THERMAL STRATIFICATION, CYCLING AND STRIPING (TASCS) PROGRAM RESEARCH PROJECT 3153-02 l (EPRI REPORT TR-103581, MARCH 1994)

TURBULENT ENERGY FROM THE REACTOR COOLANT LOOP IS INSUFFICIENT TO CAUSE THERMAL CYCLING OF LEAKAGE FLOW BEYOND THE LENGTH Lm, WHICH IS MEASURED AXIALLY ALONG THE AUXILIARY PIPING FROM THE LOOP CONNECTION i

i

DISTINCTION BETWEEN TURBULENT PENETRATION LENGTH AND TURBULENT PENETRATION THERMAL CYCLING TURBULENT PENETRATION LENGTH RCS

{ x ZONE OF PIPING HEATED BY RCS TURBULENCE, LTP (10 TO 25 PIPE INNER DIAMETERS)

TURBULENT PENETRATION THERMAL CYCLING LEA $ RCS I

• =

• ZONE OF PIPING VULNERABLE TO CYCLING, Lm

• CYCLING MUST BE ASSUMED TO OCCUR AT ALL LOCATIONS WITHIN PREDICTED CYCLING ZONE

I.

TURBULENT PENETRATION THERMAL CYCLING W

k , =///c/)

L, (uEAsunEo Fnou no ogag poow(coto)

OF HEADER PIPE) ,

U i

l HEADER PlPE FLOW (HOT) q l

( () l 1

l l

e TURBULENT ENERGY DECAYS EXPONENTIALLY ALONG THE BRANCH PIPE FROM THE HEADER PIPE CONNECTION e BEYOND L., TURBULENT ENERGY CANNOT CYCLE STRATIFIED FLOW

. L. IS A FUNCTION OF LEAK FLOW RATE AND TEMPERATURE, AND HEADER FLOW VELOCITY AND TEMPERATURE 1

TURBULENT PENETRATION THERMAL CYCLING 14

- 12 10  %

h 2

5 8 o

o 6 m

4 E

E2 1

0 {

.0 2 4 6 8 10 LEAK FLOW RATE (GPM)

LEAK h a RCS )

ZONE VULNERABLE TOTHERMAL CYCUNG L VARIES WITH LEAK FLOW RATE.

FOR LARGER LEAKS, CYCLING IS MORE LIKELY TO OCCUR CLOSER TO RCS. 1 PIPING VULNERABLE TO CYCLING IS WITHIN 15 PIPE INSIDE DIAMETERS (L/D) OF RCS.

LOCATION OF SAFETY INJECTION LINE CRACKS 18

> . 16 -. UPPER LIMIT OF THERMAL CYCLING (4 = 15 UD) 7 g 14 --

=

O -

m E 12 -

k 10 -- i z i 8-- M h

< m 6--

, m .

k 4-- a 5

2--

.o -l  :  :  :  :

n r e n en n E E E E

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e n t t t i:  !

O O S 5

l g

l ALL KNOWN CRACKING INCIDENTS RESULTING FROM LEAKAGE INTO THE RCS HAVE OCCURRED WITHIN THE ZONE PREDICTED BY THE TASCS METHODOLOGY

FARLEY SAFETY INJECTION CRACKING VS. TASCS SIMULATION TESTING FARLEY CRACKING:

• CRACK IN ELBOW INLET WELD (5 L/D)

• NO CRACK INDICATIONS AT VALVE WELD (8 L/D)

FARLEY PLANT MONITORING:

• HIGH DELTA T AND CYCLING AT 6 L/D TASCS SIMULATION TESTING:

• LOW DELTA T AND MINIMAL CYCLING AT ELBOW WELD (5 L/D) e HIGH DELTA T AND SIGNIFICANT CYCLING AT 6 L/D e TASCS METHODOLOGY PREDICTS CYCLING IS POSSIBLE FROM HEADER TO VALVE DISK WHY CRACKING AT 5 L/D AND NOT 6 L/D PER TASCS TESTING?

e PROBABLE DIFFERENCE IN LEAK FLOW RATE:

FARLEY LEAK FLOW RATE (UNKNOWN)

LEAK FLOW RATE INFLUENCES CYCLING LOCATION

• POTENTIAL HIGHER TURBULENT ENERGY IN TASCS TESTING

FARLEY SAFETY INJECTION CRACKING (CONT.)

TASCS TESTING: DIRECTION OF LEAK FLOW e HIGH DELTA T AND CYCLING

• LOW DELTA T 0 p(lq 7 3 I '

6 UD 8 UD ~ ~

6" CHECK VALVE '

5 UD l

r ,-

k"M

. l_ _ _r _

, n% _

.,T (f

/ UPSTREAM OF DISK 10 UD FARLEY MONITORING (HIGH DELTA T, AND CYCLING)

FARLEY CRACK 8" HEADER (TASCS TESTING) 27.5" HEADER INSIDE DIAMETER (FARLEY COLD LEG)

. DESPITE DIFFERENCES, TASCS CONSERVATIVELY PREDICTED CYCLING ZONE I

TASCS APPROACHES TO DETERMINE CYCLIC FREQUENCY TASCS METHODOLOGY PROVIDES FLEXIBLE BUT CONSERVATIVE APPROACHES TO DETERMINE CYCLIC FREQUENCY:

. TASCS METHODOLOGY RECOGNIZES TEMPERATURE MONITORING AS AN ACCEPTABLE APPROACH TO DETERMINE CYCLIC FREQUENCY (E.G.,1988 FARLEY EVALUATION)

. ULTRA-CONSERVATIVE APPROACH:

- DETERMINE STEADY STATE STRESS *

- ASSUME CYCLIC FREQUENCY OF ONE CYCLE / MINUTE

-THIS APPROACH RESULTS IN MAXIMUM STRESS AND MAXIMUM CYCLES l

. CONSERVATIVE BUT MORE REALISTIC APPROACH:

- DETERMINE TIME DEPENDENT STRESS DISTRIBUTION

- DETERMINE WOAST CASE FREQUENCY THAT MAXIMlZES S.a LOWER FREQUENCIES YlELD HIGHER STRESS HIGHER FREQUENCIES YlELD LOWER STRESS l

• STRATIFICATION STRESS IS MAXIMUM AT STEADY STATE

i l

APPLICATION OF TASCS METHODOLOGY l TO FARLEY SAFETY INJECTION LINE CRACKING INCIDENT l

l l

THE TASCS METHODOLOGY CONSERVATIVELY PREDICTS CRACKING ATFARLEY*

l l

l l

I

• NOTE: APPLICATION OF THE TASCS METHODOLOGY TO OTHER '

SAFETY INJECTION LINE CRACKING INCIDENTS (TlHANGE, ETC.)

WOULD RESULT IN THE SAME CONCLUSION

_' * ' l7 i :. '. , y1,"

? "?.: V:. .. -

..,__,-,--_n._,-

APPLICATION OF TASCS METHODOLOGY

• ' TO FARLEY SAFETY INJECTION LINES

\

THERMAL LOADING:

UNISOLABLE PIPE IS 550*F (COLD LEG)

. LEAKAGE TEMPERATURE AT CHECK VALVE IS 100*F

. MAXIMUM POSSIBLE FLUID DELTA T IS 450*F (ESTIMATE FROM FARLEY MONITORING IS 335'F

. CYCLIC PERIOD IS FlVE MINUTES (ESTIMATE FROM FARLEY MONITORING IS 6 TO 13 MINUTES)

. TASCS CONSERVATIVELY PREDICTS THERMAL LOADING CRACK LOCATION:

. UNISOLABLE PIPING UP TO CHECK VALVE IS VULNERABLE TO TURBULENT PENETRATION THERMAL CYCLING

. CRACKING OCCURRED IN UNISOLABLE PIPING

. TASCS CORRECTLY PREDICTS FAILURE ZONE TIME TO FAILURE:

. THE TASCS METHODOLOGY PREDICTS THAT CRACKING WOULD OCCUR IN LESS THAN 2 YEARS.

. TASCS, THEREFORE, CONSERVATIVELY PREDICTS THE TIME SPAN FOR THE FARLEY FATIGUE FAILURE.

SAFETY INJECTION LINE (FARLEY CASE)

LEAK FLOW TEMPERATURE 500 --  !

i 0.05 gpm C  :  :

0 i

$ 400 -- i sm  : 0.10 gpm 1

)

! /

g 300 -- /

W /

a.  : /

I  ! /

j 3: 200-- i j j' O.50 gpm

• W  ! .-

6 J

100 .

1.0 gpm O i

! 550T LEAK  :

, 2 e coLo  ;

-rac -

LEAK SOURCE IS 100 F c,

• TASCS PREDICTS MINIMAL HEATUP OF LEAKAGE IN UNISOLABLE PIPE AT ESTIMATED LEAK RATE OF 0.5 GPM

i SAFETY INJECTION LINES (FARLEY CASE)

FLUID DELTA T IN UNISOLABLE PIPING C 450 s - - . . . . . . . - - - - - - . . . . . . . . . . . . . . . . . 1. 00 g p m 400 -- N 0.50 gpm

• N

@ 350 -- s a 's F 300 - -

's  %

b< 2 5 0 --  %*%

g ' N.10 gpm g 200 --

O P 150 --

k 100 -.- 0.05 gpm I

(

• TASCS PREDICTS HIGH FLUID DELTA T 50 ~ ~ AT ESTIMATED LEAK RATE OF 0.5 GPM

• 0  :  :  :  :

0 10 20 30 40 50 DISTANCE FROM CHECK VALVE OUTLET (INCHES) i MONITORING INO!CATED l CYCLING. ESTIMATED NO CRACK INDICATIONS FLUID DELTA T WAS 335 F. CRACKING I l (8 UD FROM COLD LEG) (6 UD FROM COLD LEG) (5 IJD FROM COLD LEG)

/

'/ / COLD LEG l LEAK 550*F

. ZONE OF PIPING VULNERABLE TO THERMAL CYCLING INCLUDES ALL OF THE UNISOLABLE PIPING

• HIGHER LEAK RATES RESULT IN LARGER DELTA Ts BECAUSE LEAKAGE IS LESS L1KELY TO HEST UP PIPING e CRACKING MORE LIKELY TO OCCUR CLOSER TO LOOP AS LEAK RATE INCREASES

APPLICATION OF TASCS METHODOLOGY TO SOUTH TEXAS PROJECT CHARGING LINES CHARGING LINES DO NOT HAVE A COLD LEAK SOURCE THE TASCS METHODOLOGY PREDICTS THAT THE STRUCTURAL INTEGRITY OF THE CHARGING LINES WOULD NOT BE CHALLENGED WHEN SUBJECTED TO ISOLATION VALVE LEAKAGE OVER THE LIFE OF THE UNITS

CHARGING SYSTEM LAYOUT

"EjENERATIVE gg 25'

"" 3' PIPING IS INSULATED H T 7'

CV0007 CV0008 ,

POINT "A" 3 1' g 1' 6' 13'  !' "U3 # '

xCv0003 xCv0002 xCv0001 1' 3,

24' 'W 5 ' '

3' NORMAL CHARGING LINE 7' 10' l

/ 2, 49' 3' 1' 1' 1' 6' 2

b' b' .RCS COLD LEG xCv0005 xCv0004 LOOP 3 ALTERNATE CHARGING LINE

• CHARGING FLOW TEMPERATURE AT THE REGENERATIVE HEAT EXCHANGER OUTLET IS 477 F FOR MAXIMUM CHARGING FLOW CONDITIONS (=530 F AT NORMAL FULL POWER OPERATION)

• PIPE LENGTHS FOR POINT "A" TO THE UNISOLABLE PIPE:

86 FEET (NORMAL CHARGING LINE, VALVE XCV001) ,

107 FEET (ALTERNATE CHARGING LINE, VALVE XCV0004) l I

l

)

l

SOUTH TEXAS PROJECT CHARGING LINES LEAK TEMPERATURE seo .

• TASCS PREDICTS MINIMAL COOLING  : 0.05 gpm ** l OF LEAKAGE AT HIGHER LEAK RATES i l (SIMILAR TO LINE BEING IN SERVICE) j saa . ]

i 0.10 gpm," l C i /  !

j S*

g s-- . . . . . . . . - .1.o gpm * !. . .. .. ..p, . ; .(. [.. .. .,.

E "' s N

0.50 gpm * !

! /

[

h< N N

i

/

400 -

\  :

N -

E s

% 380 -

N s i:/

uJ N  :/ " TASCS PREDICTS O . SIGNIFICANT HEATING h 320 -  ! OF SMALL LEAKS IN

UNISOLABLE PIPE.

! PREHEATING UPSTREAM ,

200 - j OF CHECK VALVE WAS l NOT CONSIDEDED HERE.

240  :

Q W

! NORMAL CHARGING XCV0003 XCV0002 N

XCV0001,

'T' j SMT

- LEAK  :

• ALTERNATE CHARGING M XCV0006 4' XCV0005 NXCV0004 TX i

w ,

SOUTH TEXAS PROJECT CHARGING LINES '

DELTA T IN UNISOLABLE PIPING 350

• PREDICTED HIGHER DELTA T'S AT LOWER LEAK RATES (6 TO 13 OUNCES / MINUTE) WOULD BE INSIGNIFICANT, 0.05 gpm

• CONSIDERING PREHEATING UPSTREAM OF VALVE.

j C 300" THIS IS CONSISTENT WITH EdF STUDIES WHICH G INDICATE THAT AT LEAST 0.4 GPM OF COLD LEAKAGE IS W NECESSARY TO INITIATE CRACKS IN SAFETY INJECTION b 250 -- PIPING.

h N ZONE VULNERABLE TO THERMAL CYCLING, L l d 200 -- N' s Q 0.10gpm N g WITHIN 15 UD (52") OF COLD LEG Z

O 33o ._ -

h E 100 - .

0.50 gpm

\*g*

g 1.0 gpm g  %~ ~.

u) 50 - -

LEAK _

0 l l O 10 20 30 40 50 60 70 80 DISTANCE FROM CHECK VALVE OUTLET (INCHES) i 24 UD (82") FROM COLD LEG Lm = 52"

/

S CL l NORMAL CHARGING LINE 560F XCV0001,l l

1

' STP MONfTOMING OONFIRMED NO CYCUNG WfTH FLOW l ouseNG R ON, S T FICA l ~v.~:=am!*-

8

' i L. = 52" A

I f

=

ALTERNATE CHARGING LINE

=Ql

'g C XN 21 UD (73') FROM COLD LEG

O SOUTH TEXAS PROJECT CHARGING LINES MAXIMUM CALCULATED STRATIFICATION DELTA T IN ZONE SUSCEPTIBLE TO THERMAL CYCLING 200 C 180 d 160 0

'^ '

ii 120 I N' '

g 100 / N ,

E 80 f 60

$ 40 20 0

o o.1 0.2 0.3 o.4 0.5 o.s LEAK RATE (GPM)

MAXIMUM STRATIFICATION DELTA T IS 16(fF FOR A LEAK FLOW RATE OF 0.10 GPM

~

f

^

SOUTH TEXAS PROJECT CHARGING LINES

, FATIGUE EVALUATION OF LEAK TRANSIENT PIPING IN TURBULENT PENETRATION THERMAL CYCLING ZONE:

.* MAXIMUM STRATIFICATION DELTA T IS 160 F e CONTROLLING COMPONENT IS ELBOW WELD e MAXIMUM S.n IS 14.4 KSI (N.now = 4.5E7 CYCLES) e LEAKAGE CONTRIBUTION TO FATIGUE NEGLIGIBLE (0.084)

• I l

PIPING BEYOND CYCLING ZONE:

• MAXIMUM S.n IS 27 KSI AT VALVE WELD e

LOW NUMBER OF STRESS CYCLES (PLANT HEATUP/COOLDOWN)

. LEAKAGE CONTRIBUTION TO FATIGUE USAGE IS NEGLIGIBLE

• ASSUMING CONTINUOUS CYCLING FOR 40 YEAR PLANT LIFE.

~

SOUTH TEXAS PROJECT CHARGING LINES MAXIMUM CALCULATED STRATIFICATION DELTA T IN ZONE SUSCEPTIBLE TO THERMAL CYCLING FOR RHX OUTLET TEMPERATURE OF 530 F (TYPICAL CHARGING TEMPERATURE AT NOT/NOP) 200 -

180 160 8 -

@ 140 F t j

W E 120 -

/

i

!10. x N 80 J N 60 5 40 20 0

0 0.05 0.1 0.15 0.2 0.25 LEAK RATE (GPM)

MAXIMUM STRATIFICATION DELTA T IS 145 F FOR A LEAK FLOW RATE OF 0.075 GPM MAXIMUM S,IS 13 KSI l

S,IS LESS THAN Sone (13,6 KSI @ 10" CYCLES) 1

CONCLUSIONS FOR SOUTH TEXAS CHARGING LINES

. BASED ON TASCS METHODOLOGY, STRUCTURAL INTEGRITY OF THE CHARGING LINES WOULD NOT BE CHALLENGED

. BASED ON STP MONITORING *, STRUCTURAL INTEGRITY OF THE CHARGING LINES WOUl D NOT BE CHALLENGED

• STP MONITORING CONFIRMED NO CYCLING WITH FLOW THROUGH BYPASS LINE CONTAINING VALVE XCVOOO7. DURING NORMAL POWER OPERATION, STRATIFICATION DELTA T WAS APPROXIMATELY 40*F. (16 UD FROM COLD LEG)

ALTERNATE CHARGING LINE b  : VCL ,

Lm(15 UD) 21 UD (73") FROM COLD LEG f l

ESTIMATION OF DATE AT WHICH SOUTH TEXAS PROJECT UNIT 1 CHARGING LINE FATIGUE USAGE COULD REACH 1.0 ASSUMING CYCLING AT THE CHECK VALVE WELD *

• FATIGUE USAGE TO DATE BASED ON PLANT HISTORY, ASSUMING CONTINUOUS LEAK IN THE ISOLATED LINE

. FUTURE FATIGUE USAGE BASED ON 100% PLANT AVAILABILITY, AND ALTERNATE USE OF EACH CHARGING FLOW PATH

= MAY 15,2009 l

l l

l

• NRC HAD PREVIOUSLY REQUESTED THAT CYCLING BE CONSIDERED AT THE CHECK VALVE OUTLET WELD i 4

RECENT SAFETY INJECTION LINE CRACKS IN ELECTRICITE de FRANCE 900 MWe PLANTS

• NO NEW SURPRISES:

SIMILAR TO FARLEY CRACKING FRENCH REFER TO THIS AS THE FARLEY-TlHANGE ISSUE

• CRACKS WERE FOUND IN STRAIGHT SECTIONS OF PIPING.

(WHILE WELDS MAY BE PREFERRED INITIATION SITES, STRAIGHT PIPE IS NOT IMPERVIOUS TO CRACKING.)

• EdF STUDY INDICATES AT LEAST O.4 GPM OF COLD LEAKAGE IS NECESSARY TO INITIATE CRACKS.

• CONCLUSIVE EVIDENCE IS THAT A COLD LEAK AT A SUFFICIENTLY HIGH FLOW RATE WILL RESULT IN CRACKING AT THE CYCLING LOCATION.

I

• EdF INITIATIVES TO RESOLVE CRACKING:

IMPLEMENT GENERIC MODIFICATION ON ALL THIRTY-FOlJR 900 MWe UNITS DURING 1999-2002 MODIFICATION INCLUDES ADDITIONAL PIPING CONTAINING AN ACTIVE RE!.lEF VALVE (i.E., MONITOR 1 AND RELIEVE PRESSURE) a

i

\

CURRENT STATUS OF DOMESTIC WESTINGHOUSE PLANTS

. REGARDING CHARGING LINES I

l l

I

• LINES NOT SUSCEPTIBLE (54% OF THE PLANTS):

-LAYOUT PRECLUDES STRATIFICATION J

-lNSUFFICIENT AP ACROSS ISOLATION VALVE

-SIMULTANEOUS OPERATION OF BOTH CHARGING LINES

-SINGLE CHARGING FLOW PATH (NO ALTERNATE PATH) e MONITORING BEING PERFORMED k OF THE PLANTS)

• UNKNOWN STATUS (11 % OF THE PLANTS)

• LEAKAGE ACCEPTABLE PER ANALYSIS (8% OF THE PLANTS)

(RESULTS BASED ON IN HOUSE WESTINGHOUSE DATA, WHICH MAY NOT l BE CURRENT. THIS INFORMATION IS PROVIDED TO INDICATE THE GENERAL STATUS OF WESTINGHOUSE PLANTS REGARDING BULLETIN )'

88-08 REQUIREMENTS FOR CHARGING LINES.)

GENKAl UNIT 1 RESIDUAL HEAT REMOVAL LINE CRACKING INCIDENT us., ....i

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w i .i.sio, v.i..

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1 h0T INTERMITTENT LEAKAGE FROM THE RCS INTO THE COLD TRAPPED PIPING CAUSED SEVERE STRATIFIOATION CYCLES THAT RESULTED IN CRACKING IN THE UNISOLABLE PIPE THE CRACK WAS STABLE AND WOULD NOT HAVE RESULTED IN A DOUBLE-ENDED GUILLOTINE BREAK

GENKAl UNIT 1 CRACKING INCIDENT

• RESIDUAL HEAT REMOVAL SUCTION LINE,8" SCH 140 PIPING e LEAK WAS FROM HOT LEG THROUGH THE VALVE PACKING GLAND (WET AND RUSTED LEAKOFF PIPING) l

• SEVER STRATIFICATION IN COLD-TRAPPED HORIZONTAL PIPE NEAR ISOLATION VALVE j e LEAK WAS PERIODIC (20 MINUTE CYCLES), DRIVEN BY EXPANSION / CONTRACTION OF VALVE DISK, PER MHI e CRACK INITIATED ON ID OF ELBOW TO HORIZONTAL PIPE WELD (BASE TO WELD METAL INTERFACE), AT 12 O' CLOCK )

POSITION

• CRACK SHOWN TO BE STABLE UNDER MAXIMUM LOADINGS  ;

e VALVE WAS ADJUSTED TO ALLOW CONTINUOUS LEAK, THUS ELIMINATING CYCLING {

l i

1 l

1

)

i I

9

e APPLICATION OF TASCS METHODOLOGY TO GENKAl 1

RESIDUAL HEAT REMOVAL LINES l

1 THE TASCS METHODOLOGY CONSERVATIVELY PREDICTS CRACKING AT GENKAl

APPLICATION OFTASCS METHODOLOGY TO DETERMINE THERMAL LOAD CONDITIONS FOR GENKAl RESIDUAL HEAT REMOVAL LINE

. UNISOLABLE PIPE IS HOT OVER A DISTANCE OF AT LEAST 10 UD FROM THE HOT LEG CONNECTION.

. PIPING BEYOND 10 UD IS AT AMBIENT TEMERATURE (THE UNISOLABLE PIPE LENGTH IS 24 UD).

LEAK TEMPERATURE IS THE HOT LEG TEMPERATURE (~620 F).

. STRATIFICATION IS PREDICTED IN THE HORIZONTAL SECTION OF UNISOLABLE PIPING NEAR THE ISOLATION VALVE, BASED ON THE RICHARDSON NUMBER.

. THERMAL STRESS CYCLING WAS REPORTED TO HAVE l RESULTED FROM PERIODIC VALVE LEAKAGE DUE TO HEATING AND COOLING OF THE VALVE DISK, AT 20 MINUTE CYCLES.

. CRACKING OCCURRED IN THE HORIZONTAL SECTION OF PIPING, WHERE TASCS PREDICTS A HIGH DELTA T (~520 F).

l l . TASCS THERMAL LOAD BOUNDS THE ACTUAL THERMAL LOADING, SINCE BOUNDARY TEMPERATURES (HOT LEG AND AMBIENT) ARE USED.

. TASCS PREDICTS FATIGUE FAILURE WITHIN THE HORIZONTAL SECTION OF UNISOLABLE PIPING NEAR THE ISOLATION VALVE.

THE CRACK OCCURRED IN THIS SECTION.

SOUTH TEXAS PROJECT CHARGING LINES REASONS WHY CRACKING IS UNLIKELY

• LEAK SOURCE IS HOT (FARLEY SI LEAK SOURCE WAS COLD).

• SMALL LEAKS WOULD SIGNIFICANTLY PREHEAT UPSTREAM OF THE CHECK VALVE.

• COLD LEAKAGE OF GREATER THAN O.4 GPM IS NECESSARY TO INITIATE A CRACK, PER ELECTRICITE de FRANCE STUDY.

• LEAKS OF ABOUT 0.5 GPM OR HIGHER RESULT IN CONDITIONS SIMILAR TO THE CHARGING LINE BEING IN SERVICE.

• SOUTH TEXAS MONITORING SHOWED NO CYCLING AT 16 L/D WITH BYPASS LINE FLOW.

• TURBULENT PENETRATION CYCLING NOT CREDIBLE AT THE CHECK VALVES, WHICH ARE AT LEAST 21 L/D FROM COLD LEGS.

• CYCLING DUE TO INTERMITTENT LEAKAGE (E.G., GENKAl RHR)

NOT CREDIBLE SINCE ISOLATION VALVE TEMPERATURE IS CONSTANT.

• THERE HAVE BEEN NO FAILURES IN CHARGING SYSTEM LINES.

• ISOLATION VALVE LEAKAGE RESULTING IN CHARGING LINE CRACKING IS NOT CREDIBLE, BASED ON THE ABOVE CONSIDERATIONS.

1 i

i i

SOUTH TEXAS PROJECT RESIDUAL HEAT REMOVAL LINES REASONS WHY CRACKING IS UNLIKELY

= UNISOLABLE PIPE IS HOT OVER A DISTANCE OF AT LEAST 10 UD FROM THE HOT LEG CONNECTION. SINCE THIS EXTENDS INTO THE HORIZONTAL PIPING, FREE CONVECTION IS CAPABLE OF HEATING ALL OF THE UNISOLABLE PIPING.

• TEMPERATURE MEASUREMENTS AT SOUTH TEXAS CONFIRMED THAT THE PIPING NEAR THE ISOLATION VALVES IS HOT.

• HOT LEAKAGE ENTERING A HOT SECTION OF UNISOLABLE PIPING PRESENTS NO STRUCTURAL INTEGRITY CONCERNS, SINCE THE DELTA T IS NEGLIGlBLE.

. THE SOUTH TEXAS RHR ISOLATION VALVES DO NOT HAVE LEAKOFF LINES, WHICH WERE THE LEAK PATH AT GENKAl.

• LEAKAGE IN THE OTHER POTENTIAL LEAK PATH IS PROHIBITED BY TWO CLOSED VALVES IN SERIES (DOUBLE ISOLATION).

. EVALUATION ASSUMING GENKAl TYPE LOADING (WCAP-12108)

INDICATED CRACKING UNLIKELY AT SOUTH TEXAS

. THERE HAS BEEN ONLY ONE REPORTED FAILURE IN RHR LINES.

THIS INCIDENT RESULTED FROM A COMBINATION OF VERY SPECIFIC COEXISTING DETRIMENTAL CONDITIONS WITHIN THE SYSTEM (COLD TRAPPED PIPING, PERIODIC LEAKAGE THROUGH VALVE PACKING GLAND CAUSED BY CYCLIC HEATING OF ISOLATION VALVE DISK).

• ISOI.ATION VALVE LEAKAGE RESULTING IN RHR LINE CRACKING AT SOUTH TEXAS IS NOT CREDIBLE, BASED ON THE ABOVE l CONSIDERATIONS l

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