05000424/LER-1996-001, :on 960220,nuclear Svc Cooling Water Sys Determined Inoperable Due to Pipe Fatigue.All Discharge Line Weld Indications &/Or Cracks Have Been Repaired & Design Changes Have Been Implemented

:on 960220,nuclear Svc Cooling Water Sys Determined Inoperable Due to Pipe Fatigue.All Discharge Line Weld Indications &/Or Cracks Have Been Repaired & Design Changes Have Been Implemented

ML20117M727
Person / Time
Site:	Vogtle
Issue date:	09/10/1996
From:	Mccoy C, Sheibani M GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LCV-0773-A, LCV-773-A, LER-96-001, LER-96-1, NUDOCS 9609180013
Download: ML20117M727 (5)

LER-1996-001, on 960220,nuclear Svc Cooling Water Sys Determined Inoperable Due to Pipe Fatigue.All Discharge Line Weld Indications &/Or Cracks Have Been Repaired & Design Changes Have Been Implemented

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
4241996001R00 - NRC Website

text

_ _ _ _ _ _ _ _ _ - _.

Georgia Power Company 40 inverness Center Parkway Post Offce Box 1295 Birmingham. Alabama 35201

, Telephone 205 877-7122 C. K. McCoy Georgia Power Vee Presdent Nuclear Vogtle Project tre southem electic system September 10, 1996 LCV-0773-A Docket No. 50-424 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Ladies and Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT LICENSEE EVENT REPORT l-96-1, Revision 1 PIPE FATIGUE LEADS TO NUCLEAR SERVICE COOLING WATER SYSTEM INOPERABILITY In accordance with the requirements of 10 CFR 50.73, Georgia Power Company (GPC) hereby submits the enclosed revised report. Completion of corrective action is being extended due to additional design changes, an unplanned unit outage that divened manpower resotrces, nd a delay in obtaining the necessary materials.

Sincerely, C. K. McCoy CKM/TEW Enclosure: LER 1-96-1, Revision I cc: Georgia Power Company Mr. J. B. Beasley, Jr.

Mr. M. Sheibani NORMS U. S. Nuclear Regulatory Commission Mr. S. D. Ebneter, Regional Administrator Mr. L. L. Wheeler, Licensing Pr@ct Manager, NRR Mr. C. R. Ogle, Senior Resident ingector, Vogtle l

i(^

9609180013 960910

~~

l PDR ADOCT 05000424 l

g PDR i

NRC FOR1136s U.S. NUCLEAR RE& ULAToRY CoMMISSloN APPROYED OMB NO. 31 SO4104 (4M)

EXPIRES. 04t30/98

'a" Jay'F#e"Ma " cwa"CL' Ra"D' % a' LICENSEE EVENT REPORT (LER) tEs"'S N'$U INUE iO"Cx 'TO " E 'Y

'"ISWE O

N F

ORDS M NT B H

6 33 US UCLEAR i

K R TION R

(

04 OFFICE MANAGEMENT AND BUDGET. WASHINGTON. DC 20603.

P ACILITY NAME (1)

DOCKET NUMBER (2) s's it Vogtle Electric Generating Plant - Unit 1 l5l0l0l0l4l2l4 1

OF 4

TITLE (4)

PIPE FATIGUE LEADS TO NUCLEAR S":RVICE COOLING WATER SYSTEM INOPERABILITY EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR 6E R

MONT H DAY YEAR FACILITY NAME DOCKET NUMBER (S) olslololol l l F ACluTY NAME 012 210 916 9l6

~ Ol0ll

~

0l1 0l9 1l0 9 l6 ol5lololol l l THIS REPORT 18 $UBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 6: (Check one or more) (11)

OPERATING MODE (9)

]

20 2201(b) 20 2203(a)(2)(v)

X SO 73(a)(2)(t) 60 73(a)(2)(vm)

POWER 20 2203(a)(1) 20 2203(a)(3)(.)

50 73(a)(2)(n) 50 73(a)(2)(x)

LEYEL (10) l9l}

20 2203(a)(2)(!)

20 2033(a)(3)(a) 50 73(a)(2)(m) 73 y 20 2203(a)(2)(u) 20 2033(c)(1) 50 73(a)(2)(w)

OTHER

]

20 2203(a)(2)(m)

$0 36(c)(1)

X 6o 73)(2)(v) s,.c,ry m 4esir.c,e.e.

20 2203(a)(2)(v) 60 36(c)(2)

X

$0 73(a)(2)(vn) er m A/RC Form 306A LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (mclude area coa.)

^ " ' ' ' '

Mehdi Sheibani, Nuclear Safety and Compliance 710l6 812161-1312l0l9 COMPLETE ONE LINE FOR EACH COMPONENT F AILURE DESCRIBED IN THl3 REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPRDS l

n BIS lPlSIP Kl01515 N

l l l l l l l l

II I I II I

I I I I

I 1

SUPPLEMENT AL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBMISSION YES (if ye. complete EXPECTED SUBMISSION DATE)

X NO DATE (15) l l

l

.TR Au-,o 14w.,-..,.. a,,,o-m.,1s.

. -e, im..nio)

On February 17,1996, the nuclear service cooling water (NSCW) pump #1 (Train A) discharge line 1

was found to be cracked and leaking at the toe of the weld where the 4-inch bypass line weldolet joins the main 18-inch pump discharge line. On February 19,1996, the other two NSCW pump discharge lines on Train A (3 and 5) were also found to have indications and/or cracks. On February 20,1996, the three NSCW Train B pump discharge lines (2,4 and 6) were found to have indications and/or cracks. By 2225 EST, on February 20,1996, an engineering evaluation concluded that, due to the indications, pumps 1, 2, 5, and 6 may be unable to perform their intended safety function following a seismic event. Pump 1 in Train A had been returned to service earlier that day following weld repair and pump 3 had been subsequently removed from service. However, unit operation per Technical Specification (TS) 3.0.3 was initiated because the TS requires at least two pumps in one train of NSCW to remain operable. At 2242 EST, on February 20,1996, pump 3, also in Train A, was returned to service following weld repair, and unit operation per TS 3.0.3 was ended.

l The cause of this event was a design that allowed fatigue cracks to develop in the NSCW pump i

discharge piping. All of the indications / cracks in the pump discharge lines have been repaired.

Additional design upgrades have been developed and are being implemented.

1 I

NRC Form 364 (4%)

l

~

NRC 70RM 3ssA U.S. NUCLEAR REa ULAToRY coMMISSloN (4 95) l LICENSEE EVENT REPORT (LER) l TEXT CONTINUATION l

1 F ACluTY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

L YEAa j seougNy Rg;sgg Vogtle Electric Generating Plant - Unit 1 je.5l0l010l4l2l4 9l6

- 0l0l1 0l1 l2 OF l4 runn mo,..

c..

.au,on..om, mC % 3eewi

• A. REQUIREMENT FOR REPORT l

This report is recuired per:

l

1) 10 CFR 50.71 (a)(2)(i), because the unit operated in a condition prohibited by the Technical Specifications (TS),

j

2) 10 CFR 50.73 (a)(2)(v), because a condition existed that alone could have prevented the fulfillment of the safety function of the nuclear service cooling water (NSCW) system, and

3) 10 CFR 50.73 (a)(2)(vii), because a single condition caused independent trains to become inoperable in the same system.

B. UNIT STATUS ATTIME OF EVENT l

At the time of the discovery of this event on February 20,1996, Unit I was operating in Mode 1 l

(power operation) at 92 percent of rated thermi.1 power. Other than that described herein, there was no inoperable equipment that contributed to the occurrence of this event.

C. DESCRIPTION OF EVENT

l On February 17,1996, nuclear service cooling water (NSCW) system pump 1 (Train A) was out of l

service for maintenance. Following a pump start, an equipment operator noticed a leak coming from the toe of the weld where the 4-inch bypass line weldolet joins the main 18-inch pump discharge line.

Around this weldolet, two indications were found, one with through wall leakage. The indications were 180 degrees apart, each approximately 4 to 6 inches long at the surface, and were oriented l

roughly parallel to the axis of the 18 inch pump discharge line. Following inspection by a j

metallurgist, who determined that the indications appeared to be fatigue induced, repairs were initiated.

.. On February 19,1996, the same welds on the discharge lines of the other two pumps in NSCW Train A, the pump 3 and pump 5 discharge lines, were inspected with liquid penetrant and similar l

indications were found, but no leakage was observed. An engineering evaluation was initiated to support the interim operability determination that these pumps remained operable, even with indications.

4

- 1 i

NRC 7orm 346A (446)

)

,U.S. NUCLEAR RE a ULAToRY CoMMISSloN (4-05)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION j

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER [6)

PAGE (3)

YEAR l SEQUENilAL REV$ N s

Vogtle Electric Generating Plant - Unit 1 0l5l0l0l0l4l214 9l6 0l0l1 0l1 l3 OF l4 m, mm..

c..,.,.

.aa-m., cor.. o, Nac go, 3ee,;(ii)

On February 20,1996, at 1530 EST, liquid penetrant inspections were performed on the same discharge line welds on the NSCW Train B pumps 2,4 and 6. Indications similar to those found on Train A were found at the toe of all three welds and water seepage was found on the pump 4 discharge line weld. These Train B ind cations were then included in the ongoing engineering i

evaluation.

Also, on Feb:uary 20,1996, at 1401 EST, pump I was returned to service, and repairs were initiated to the pump 3 discharge line weld. At 2225 EST, it was concluded that the engineering evaluation was unable to determine that pumps 1,2,5 and 6 could supply the flow required to perform their intended safety function following a seismic event. Unit operation per TS 3.0.3 was initiated because the TS requires at least two pumps in one train of NSCW to remain operable and, at that time, only pump 1 was considered operable. At 2242 EST, repairs were completed and pump 3 was returned to service and unit operation per TS 3.0.3 was ended. On February 21,1996, at 0057 EST, the NRC Operations Center was notified because this condition could have resulted in a failure of both trains of NSCW in a postulated seismic event. Weld repairs were completed and all pumps were restored to operability by February 22,1996, at 2310 EST.

D. CAUSE OF EVENT

The cause of this event was a piping design that allowed fatigue indications and/or cracks to be induced in the NSCW discharge piping. The primary cause is attributed to hydraulic transients in the bypass line, which serves as a pump miniflow line, and as a slow fill line to help minimize hydraulic transients when the pump discharge valve opens. The hydraulic transients in the bypass lines were causing movement of the lines. These hydraulically induced loads occur when an NSCW pump is started or stopped. Testing performed on February 27 and 28,1996, indicates that the most severe movements of the bypass line occur when one pump is started while the other two are in service.

This movement is primarily caused by flow from the starting pump impacting a closed check valve which must open against pressure from the operating pumps.

Modifications to reduce effects from hydraulic transients were previously made subsequent to the discovery of a pipe stress problem identified during Unit I start-up testing. The corresponding Unit 2 piping was modified and flow orifices were added to the Unit 1 piping in an efTort to reduce pipe stress. Unit 2 piping welds have been inspected with no indications found. However, all six affected Unit I locations showed indications as previously described.

i nac n,mi m r w

1

..U.S. NUCLEAR REOULAToRY CoMMISSloN l

(4 95) l LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION 1

s F ACluTY NAME (1)

DOCKET NUMBER (2)

LER NUMBER 'S)

PAGE (3)

1",I"

"'uM N

Vogtle Electric Generating Plant - Unit 1 0l5l0l0l0l4l214 9l6 0l0l1 0l1 l4 oF l4 m1,

,.ou-

, mC %,, um

E. ANALYSIS OF EVENT

NSCW is uwd to cool various safety-related components and represents the unit's ultimate heat sink.

The indications that were found did not prevent the NSCW system from performing this function.

Although one of the three locations on each train had through wall indications, the amount of leakage was insignificant and was quantified as " seeping." A review of the piping stresses at this location due to various loads and load combinations, i.e. weight, thermal, pressure, building differential settlement, seismic, hydraulic transients, etc. was performed. Testing determined that the most severe stresses were from the hydraulic transient loads resulting from starting a third pump l

while the other two pumps are in service. Although it is possible that a hydraulic transient could result in a complete severing of a 4-inch bypass pipe from one of the weld locations, the other two pumps of that train would most likely be unaffected, and the alternate train would also still be available. Based on these considerations, there was no adverse affect on plant safety or on the health and safety of the public as a result of this event.

F. CORRECTIVE ACTIONS

1) All of the discharge line weld indications and/or cracks have been repaired. An evaluation of the l

repaired piping was performed based on field testing data, actual geometry of the connection, and appropriate safety factors. The results of this evaluation demonstrated that the weld repair can withstand a significant number of severe hydraulic transients. The remaining corrective actions described below will be implemented before the number of fatigue cycles calculated in this evaluation are exceeded.

2) Design changes have been implemented and the discharge spool pieces replaced on four of the six NSCW pumps. Pipe suppon enhancements, along with replacement of the discharge spool pieces for the remaining two pumps, will be completed by December 15,1996.

G. ADDITIONAL INFORMATION

1) Failed Components:

Pipe spool at weldolet,18-inch, stainless steel,6 each, ASME Section III, Class 3, manufactured by Pullman Power Products, a division of Kellogg/Wheelabrator-Fry.

2) Previous Sim;lar Events:

None

3) Energy Industry Identification System Code:

Nuclear Service Cooling Water System - BS f 3RC Form 366A 1445)