ML20024H158

LER 91-016-00:on 910418,failure of Check Valve to Prevent Backflow Discovered.Caused by Mfg Error in Machining Process of Valve Body Casting.Valves Reassembled & Scheduled to Receive testing.W/910521 Ltr

ML20024H158
Person / Time
Site:	Comanche Peak
Issue date:	05/21/1991
From:	Hope T, Scott A TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-016, LER-91-16, TXX-91180, NUDOCS 9105290127
Download: ML20024H158 (7)

Text

.

? .

Log # TXX-91180 _-

~

file # 10200 TUll FC1RK: 910.4 c Ref. Voluntary (

w mi.m J < .u, Jr. May 21, 1991 i,,,,,,,, .. , nm a. .,. j .,

A U. S. Nuclear Regulatory Conunission 5 Attn: Document Control Desk 46' Washington, D. C. 20555 .J

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STA110N (CPSES)

DOCKET NO. 50 445 REPORT Of EVENT WITH GENERIC INTEREST - - -

LICENSEE EVENT REPORT 91-016-00 Gentlemen:

Enclosed is Licensee Event Report 91-016 00 for Comanche Peak Steam Electric '

Station Unit 1, " Manufacturing Error Leading to the f ailure of a Check Valve to Prevent Backflow."

Review of this event has been corducted with due regard to the previous history and corrective actions associated with these check valves at CPSES.

Based on this review, it was concluded that the current plans for continued use of these valves remains technically sound.

Sincerely, William J. Cahill, Jr.

/ /

s By.

A. B. Scott, Jr.

Vice President, Nuclear Operations JAA/bm c - Mr. R. D. Martin, Region IV Resident inspectors, CPSES (2)

I

" '""" """ ***' '" " """*' l"*' " /

b $bbk b bk4S S PDR

Enclosure to TXX 91180 NHC 5 04W 306 V $ NJGil AH HluLlLA f OHV (A>WWibbivN p g g g g p,g y E AP1HL5 4"J01l2

( STW4ft D DJWE N PtR Rf SFUNSE TO COWPtY WITH TH:S hrOWdATON COtt tCTON Rt OLit ST. 600 HRS IORWARD COVWIN15 R[GARDN3

• " * ' " ' " " ' ' ' ' " "' c "5 ^* "" "'8"'*

LICENSEE EVENT REPORT (LER) iMANCHIP 64 U.S NUCtt AR REGut ATOHY COWWIS$ON. WASHWGTON T. 20%6, AND TO THE P APE RWORK REDUCTON PROJECT (3160 010s) 3F FICC Or W ANACd WtNT AND BJCoC1, W ASHNGTCM CC A%03

, , -,, s., o )  :- w.. m r. o, lee (4)

COMANCHE PEAK - UNIT 1 015101010141415 1 I or 10i6 MANUFACTURING ERROR LEADING TO THE FAILURE OF A CHECK VALVE i TO PREVENT BACKFLOW

,%,a.m na~~m um.. m m.. . .-

(

p lv , v, TO*' d '.*, Vonih Day vr 8"N/A

'tNa*** * *N'"

0151010101 1 I ht d91 911

~

Olil8 -

010 m ... . .- , ~ .. . ~..-. . . , u v u m u 015 2l1 9 11

.m N/A

~ ,m o s ,

0151010101 l I 6013,s)mtw) b a

'k_ PO 4W(b)

PO 40$(alo)(#)

_ PO eD$ic) 60 3Nc)(t) 60.73alfttv)

_ 1311M 73 711e1 i I- '01010

- 2* '06(*d'"* -

5 '*") r -

6 7^*)* **) I ("'"' 'h4C S'*d'****'"'***"'*b-

p pem 3,r,'A)

20 436(a)(1)(m) _

60 734ax2Mi) _ 60 7Asstatv4A)

• ! Po 40s(.x4n,i 60 s.nas) 60 73..xaN.

r .w , ,,,,

w 73..,v.,

w ,3 .,w. , "' voluntary n.epon tu, Cmus.Tn. tiron

. , , . i.  %-.

Av.e Gm.

T. A HOPE COMPLIANCE SUPERVISOR 8 l 117 9l917l-l6131710 C .o.t~,eac r o.ww.rs.R.-o3 Cav.e Srstem Co"ta..a W.w.au ,

(*$"] Cao e Sriiem Cor.swer. W.veoren 7,"$n'y d B BIA II IV Bl31510 YES I l l l l l l l l l l 11 I I Il l 11I s . n , t .,-., o.i ... W- o., ..-

Sutmsewsi h Y.s (# y . cortsv.t. Ino.ded Sobevesseor, De!.i  % l l l cw eit-noi4x. .... - .e* m . - i - ..,o, ion On April 18,1991, reverse flow testing was being perinrmed on check valves in the Auxiliary Feedwater System. One of eight check valves in the system branch lines failed to meet the test acceptance criteria. The cause of the failure was determined to be a manufacturing deficiency in the finish machining of the rough casting of the valve body.

The incomplete machining resulted in excess casting materialinside the valve body which interfered with full stroke motion of the swing arm counterweight. Corrective action included finish machining of the affected check valve, inspection of similar valves in the system, and procedure review. A voluntary report is being submitted due to interest resulting from previous experience with check valves in the Auxiliary Feedwater System.

Enclosure to TXX 1.i 194 NHC FORM 3H6A U S NUCLE AR REGULATOHV COMW.550N ggg ggg g g EXPIRES: 4'30112 E STIMATED BURDEN PER HESPONSE TO COMPLY WITH THIS INFORMA?ON

" '" "E"CSU 5" "a$ ' "* ^* "*'"'5"*""

LICEfJSEE EVENT REPORT (LER) BURDEN ESilWATE TO THE RECORDS AND REPOR18 WANAGEMEN1 .

aRANCa iP sw Nm E AR uax ArORnOuuissm. WAssiNG10N.

TEXT CONTINUATION DC. P06S6. AND TO THE PAPE RWORK REDUCTON PROJECT (31600104) 0FFICE OF WANAGE MI NT AND BUDGET. W ASHINGTON. DC. 20503.

f ards, Nano p) Duches Nunte (2; LaH Nunne i,u Pep (3)

"" *W. 2%T COMANCHE PEAK - UNIT 1 015101010141415 911 i n, .. . -.. -..a .,o ,4 .m n 0I116 -

010 012 OF 018 L DESCRIPTION OF THE REPORTABLE EVENT A. PLANT CONDITIONS PRIOR TO THE EVENT On April 18,1991, Comanche Peak Steam Electric Station (CPSES) Unit 1 was in Mode 5, Cold Shutdown, with the Reactor Coolant System at a temperature of 100 degrees F and pressure of approximately 15 psia.

B. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT There were no inoperable structures, systems, or components that contributed to the event, C. NARRATIVE

SUMMARY

OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On April 18,1991, backflow testing was being performed on check valves (Ells:(V))

in the Auxiliary Feedwater (AFW) System (Ells:(BA)). One of the check valves included in the test did not satisfy the test acceptance criteria, and action was initiated to identify the cause of the test failure. Radiography revealed that the valve disk was being held off of its seat by mechanicalinterference between the disk counterweight and the valve body. The valve was disassembled and it was discovered that the valve body casting had not been fully finish machined by the manufacturer. A lip of excess casting material at the back of the valve body had caused the disk counterweight to catch on the opening stroke and hang the valve disk in the open position.

E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL OR PERSONNEL ERROR The condition was identified during work activity initiated following the failure of the check valve to meet the reverse flow test acceptance criteria.

Enclosure to TXX-91180 NRC FORM 3 64 U S. NUCLE AR RE GUL ATORY COMWissoN APPROVED OMB NO. 3160 0104 EXPIRES er10W E811M ATED BURDEN PER RESFVNSE TO COMPLY WITH THIS INrORMAtlON i

'C LICENSEE EVENT REPORT (LER) g3,," ","j"8'; ,'y","Sgn",**", , c Q%'fff;'j,

""^""N"**"""""' ****"***"'"'"-

TEXT CONTINUATION DC. 20%6, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104) 4 l

of rice OF MANAGE MENT AND BUDGET. WCHINGYON. DC. PDS03 FacMy Narne v) h et Naam E) LE4 %" tap to) Pap (;si W WC COMANCHE PEAK - UNIT 1 015101010141415 911 -

0l116 -

010 013 OF 016 I w n. . -. .-- w ,~ A ., o n

11. COMPONENT OR SYSTEM FAILURES A. FAILED COMPONENT INFORMATION l

Component

Description:

Pressure seal check valve,4 inch,900 pound Manufacturer: Borg Warner / International Pump, Inc (BW/IP).

Manufacturer's Part Number: 75560 i B. FAILURE MODE, MECHANISM, AND EFFECT OF EACH FAILED COMPONENT The affected check valve stuck open due to interference between the disk counterweight and a tip of excess casting material on the valve body, allowing reverse flow in one branch of the AFW system.

C. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE A manufacturing errorin the machining process of the valve body casting allowed excess casting material to remain on the inside surface of the valve body.

D. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS The Auxiliary Feedwater System is designed to provide flow to the steam generators for heat removal from the primary system after certain design basis accidents as described in the CPSES Final Safety Analysis Report and serves as the feedwater source during hot standby and cooldown from power operations. The system can also be used to adjust steam generator water levels prior to and during plant startup, to establish wet layup in tho steam generators, or to maintain steam generator water levels following a loss of coolant accident. The check valve failure described in this report would not inhibit the ability of the system to deliver flow to the steam generators for performance of any of the functions for which the system is designed.

- _ _ _ _ . _ _ _ _ _ > _ _ _ . _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ - r.m_. _ - - - - rr

Enclosure to TXX-91180 NRC f 0RV 3tAA U S NUCLE AR REGULATORY COMU6 SON gpFMDOMB NO Nm EXPIRES 4"n92 EST!WATED BURDEN PER RESPONSE TO COMPty WITH THIS INrORMATON

" 5 ' " """ S ' - ""8' "*^" ' * *'N'S " * " "

LICENSEE EVENT REPORT (LER) RURDE N EritM A1E TO THE RECORDS AND REPORTS MAN AGEWEN1

• • ^""i"'"'""^"""" "# c"* tSS" * 'S"*

TEXT CONTINUATION 3C. 20555 AND 10 THE P APEHWORK REDUCTON PROJECT (3ttoC104)

OF FICE OF WANAGE WlNi AND BUDGE T. W ASH:NGTON. LC 70'c3

. . ., N,. o , w N-.m a a N- m rea

• T:-# 1 bg COMANCHE PEAK..e.~ - UNIT 1 0l51010101414l5 911 0I116 -

0IO OI4 OF 0I6 i..m .. .. . . - ., o n Ill. ANALYSIS OF THE EVENT A. SAFETY SYSTEM RESPONSES THAT OCCURRED Not applicable - there were no safety system actuations associated with this event.

B. DURATION OF SAFETY SYSTEM TR AIN INOPER ABILITY There were no safety systems rendered inoperable as a result of the event.

C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT For each of the design functions of the AFW system, the failure described in this report would not prevent the system from delivering flow to the associated steam generator, and additional check valves in the system would prevent or inhibit backflow, in the absence of a line break or manual valve misoperation, the check valve failure would lack significance in any plant mode because of the absence of a backflow path, it is concluded that the condition did not adversely affect the safe operation of CPSES Unit 1 or the health and safety of the public.

IV. CAUSE OF THE EVENT Immediate cause High flow rates through the branch hne in conjunction with a manufacturing deficiency caused the check valve to stick in the open position. On April 12,1991, dynamic testing was performed on the motor operated isolation valve down stream of the affected check valve. The test is conducted to meet the requirements of Generic Letter 89-10 to ensure that the motor-operated valve will close during a main feedwater line break accident. The test simulates, to the extent possible, expected AFW flow to a faulted steam generator during the accident. The test involves a flow rate of approximately 660 gallons per minute, and caused the swing arm and counterweight to impact the excess casting material with sufficient force to cause plastic deformation to the casting and wedge the disk in the open position. The test flow rate is wellin excess of the flow rate required during normal surveillance testing of components in the AFW system.

I

Enclosure to TXX-91180 NRC FORM 3f44 U $ NUCLE AH Rt GULATOHY COMMMON APPROWD OMB NO. NOW E KPIRE S 4M2 i STIMATED BURDE N PER Rf $PONSE TO COMPLY W:TH THIS INF ORMA1ON

" " " ' ' " "' *S' * """* ' "**" " "'" "" "

LICENSEE EVENT REPORT (LER) dVRDEN ESTlW ATE TO THE RECORDS AND REPORTS MANAGEMENT TEXT CONTINUATlON ""'*"'"*"""'""" "'"******S"'" '"

JC 70$55, AND TO THE PAPE RWORK REOUCTON PROJECT (31500W)

OFFCE OF MANAGEMENT AND RUOGET, WASH:NGTON. DC. 20503 f scany Nano p) h*.i Nur,ter (2) LE A NuM*' 46, Pap 63:

'" TO? DTl' COMANCHE PEAK - Uti}Lma.,on0151010101414 N.m 1

l5 911 0l116 -

010 OIS OF 016 i.o e r . e. .

Roolcause The component was not manufactured in accordance with design. During the manufacture of the valve body, finish machining of the rough casting was not adequately performed. The incomplete machining resulted in excess casting material inside the valve body (Refer to Figure 1) which interfered with full stroke motion of the swing arm counterweight. Information related to valve port dimensions is BW/IP proprietory information and not an inspectable attribute during receipt inspection.

The counterweight was added in April,1990, as a design modification to the eight check valves in the AFW branch lines. Post modification testing consisted of manual full stroke manipulation of each set of internals on an uninstalled test valve body. Since the test valve was the same model and vintage as the installed plant valves, it was assumed that no significant differences existed in the valve bodies. In an unmodified condition the valve would not have stuck open, and the condition described should not be considered a generic problem for this model check valve in other applications.

N N

7 s

\ 's ,

s 'N N

N' \

\ 'N s N \s v

\

'\ N N \'s'9 Qx% 9 EXCESS CASTING MATERI AL AS-DESIGNED CONTOUR F1gure 1 I

Enclosure to TXX 91180 N4C f0RM 3%A U S N'JCLL AR ktOL)LAf 0HY COVWibbON gppgD OMB W WM E KPIRE S 4"JO92 ESTIMA1ED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORVATON

" ' ' ' " "' "5 $" 5" ""* ' "*** ***'S""""

LICENSEE EVENT REPORT (LER) BURDEN EsilWATE TO THE RECORDS AND REPORTS MANAGEMENT

• • ^"'" F 5 * "5 " " ^*" * *' " ""'S5 N""'" '"

TEXT CONTINUATION 3C. 705%. AND TO THE PAPERWORK REDUCTON PROJECT (31SD0104 0F FICE Or W ANAGE MENT AND BUDGE T.

• ASH'NGT ON. DC. 20603 Li 4 N W e'to Fap Qi Fncur Neo p) ax*w Neer (2)

'" .".$ l ?g"$

COMANCHE PEAK - UNIT 1 015l010l0141415 911 0l116 -

0IO OI6 OF 016 r..m - .. ... ~ . ~ a.,on V. CORRECTIVE ACTIONS IMMEDIATE The affected valve was machined to remove excess casting material from the valve body and restore the design contour of the valve port. The remaining seven check valves in the AFW branch lines were disassembled, photographed, and inspected to ensure that finish machining had been adequately performed. Measurements inside the valve body were taken for each of the valves and revealed that finish machining had been performed correctly. The valves were reassembled and are scheduled to receive forward and reverse flow testing prior to piant restart.

ACTIONS TO PREVENT RECURRENCE Procedures will be reviewed and revised as appropriate to ensure that in the event that replacement of one of the AFW branch line check valves is required, sufficient inspection and testing will be performed to prevent a similar condition.

VI. PREVIOUS SIMILAR EVENTS There have been no previous similar events reported pursuant to 10CFR50.73.

Vll. ADDITIONAL INFORMATION Although the event does not meet the reporting criteria of 10CFR50.73, a voluntary report is being submitted because of the significance and generic interest of the event resulting from pievious experience with BW/IP cneck valves in the AFW system.

_ _ _ _ _ _ _ _ _ _ - _