ML20116C981

Part 21 Rept Re Defective Welds Originally Specified & Performed by W on Component Cooling Water Nozzles for RCP Seal Injection Lines

ML20116C981
Person / Time
Site:	Summer
Issue date:	05/20/1996
From:	Zaccone M SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC
References
REF-PT21-96 30507, NUDOCS 9608010243
Download: ML20116C981 (6)

Text

. _ - - __-_ _ _. -_ __ _ - . ..

50-395 i POWER REACIOR EVENT NUMBER: 30507 FACILITY: SIBWIER REGION: 2 NOTIFICATION DATE: 05/20/96 UNIT: [1] [] [] STATE: SC NOTIFICATION TIME: 16:48 (ET]

RX TYPE: [1] W-3-LP EVENT DATE: 05/08/96  !

EVENT TIME: 00:00[EDT] l NRC NOTIFIED BY: MIKE ZACCONE LAST UPDATE DATE: 05/20/96 HQ OPS OFFICER: RUDY KARSCH NOTIFICATIONS EMERGENCY CLASS: NOT APPLICABLE 10 CFR SECTION:

CDEF 21.21(b) (2) DEFECTS / NONCOMPLIANCE HODGE NRR UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX MODE 1 i N N O HOT STANDBY 0 HOT STANDBY EVENT TEXT 1

THE LICENSEE DISCOVERED THAT WELDS ORIGINALLY SPECIFIED AND PERFORMED BY l WESTINGHOUSE ON COMPONENT COOLING WATER NOZZLES FOR REACTOR COOLANT PUMP l SEAL INJECTION LINES ARE DEFECTIVE. ONE WELD HAD A CIRCUMFRENTIAL CRACK AND FIVE OTHERS ALSO SHOWED SIGNIFICANT CRACKING. THE LICENSEE SUSPECTS THAT TIG WELDING IS REQUIRED BUT NOT DONE.

fp/7 o/

9608010243 960520 -

PDR ADOCK 05000395 S pm ,

n: m .... ~ . W. . . < W ., .. .... ~

]

i'

. VOI %%0 lem3&7) 6%I ENGINEERS Serial 15150120R3

99. Awe.

TECHNICAL WORK RECORD Enginear D. SHUE i

Date 5MU96

! Projed Title Sn= mary of Rame*ar C~ Jane Pnmn Thermal Barrier Nanla Reworks Tab 2C. Page_L of _5_

durine Refuel-8 and 9 ner NCNs 5166. 5415. 5429 and 5429A

~

SCOPE: This 'IWR provides the cause and corrective action and the 10CFR21 evaluation for NCNs 5415, 5429 and 5429A. In addition, a summary discussion of Reactor Coolant Pump thermal barrier i noule workisincluded, i

j

. v l DISPOSITION: Disposition is a " CLARIFICATION" to provide the 10CFR21 evaluation and address

cause and corrective action.

i j POSTDISPOSITION TESTING: None required for this Clarification.

DISPOSITION BASIS: No basis is required; however, the following summary of nozzle work is provided i to enhance the understanding of the work performed on the Reactor Coolant Pump i nozzle wekis at the Thennal Barrier Plange.

The initial problem with the nozzle welds at the Reactor Coolant Pump (RCP)

Thermal Barrier Flange was discovered in May of 1987. This problem was a

- through wall crack on the upper portion of the "C" RCP Seal Injection Line at the socket weld where it enters the pump thermal barrier. At that time the weld was i partially excavated and rewelded. NCN-2765 contains the details on this work.

In December of 1994 during Refuel-8, the same "C" RCP Seal Injection Line agam had a through wall leak on the same socket weld. This time the crack was on the lower portion of the weld. Again the weld was partially excavated and replaced.

After the replacement of the affected portion of the weld, all of the original Westinghouse weld had been removed. The details of this work are contained in NCN 5166.

Subsequent to the second weld failure on the "C" SealInjection line, EPRI was contacted to determine if a NDE method existed to properly examine the RCP Thermal Barrier nozzle welds for similar conditions. At the time there was no

- appropriate method; however, EPRI worked to provide an "information only"

method to examine the December 1994 failure. 'Ihis method was tested on the j failure with some success in finding the known crack.

After Refuel-8 was completed, EPRI worked to provide an acceptable NDE i method for examining all of the RCP Thermal Barrier nozzle welds. After appropdate testing, it was determined that the developed method was suitable for inspection of the nozzle to thermal barrier welds during Refuel-9. It was decided

4.v.w.. n m w ;.. m m:..i ,. m m m

.c. ... . m .x.y e g.q

. . p.. .

.,.u...,

.. .. ,..,. . s_~~~~

ENGINEERS serial 15150-120n2 TECHNICAL WORK RECORD Engineer _D. SHUE Date s/am

% Project Title S=nmary of Pear Caa1** Pumn Thervnal Barrier Nanla Reworks Tab _RC. Page _2_ of 1.

durine Refuel-R and 9 ner NCNs 5166. 5415. 5429 and 5429A that the EPRI method would be utilized to examine the Seal Injection nozzles on all of the RCPs. It is noted that this NDE technique is recognized to be a "go" or "no-go" type technique. The technique will determine if a flaw exists; however,it is unable to =p-46= 1y size and locate the flaw in the weld.

v .

The SealInjection nozzle inspections were performed during the last week of April,1996 during Refuel-9. The msults of the inspection were somewhat surprising. The "C" RCP which was rewelded in 1987 and 1994 showed no indicadons. The "B" RCP also showed no indications. However, inspection of the "A" RCP showed that weld flaws existed and that corrective action was required.

NCN-5415 was written and dispositioned to Rework the subject weld.

It was determined that per this Rework, the entire weld should be excavated and remade. 'Ihis was done based on concerns with stressing the remaining portions of the weld should partial excavation and rewelding be performed. Additionally,it v was known that partial excavation did not remove the entire problem on the "C" RCP when performedin 1987.

After removal of the nozzle assembly from the "A" RCP actions were taken to reuse the existing nozzle; however, upon closer examination it was discovered that there was significant pipe distortion and wall thinnine of the existing nozzle. It was then determmed that a new nozzle assembly would be fabricated. Disposition 2 to NCN-5415 provided for replacement of the entire nozzle assembly.

Based on the previous problems with the "C" RCP Seal Injection Line and the discovered problem on the "A" RCP Seal Injection Line, Engineering provided a recommendation to perform additionalinspections. It was known that the Component Cooling Water (CCW) nozzles at the Thermal Barrier Flange are identical to the SealIqjection nozzles; therefore, after reviewing the stresses on the lines to each pump, Design Engineering recommended inspection of the RCP "C" CCW Inlet and "A" CCW Inlet. This was based on the fact that these two locations exhibited the highest bending stress ratios and were on pumps with v' previous v eld flaws.

It is important to note that the Design Engineering nozzle evaluation is contained in 'nVR-15053 by C. Barbier dated 2/29B6. It is noted that the date on the TWR should be 4/29/96. This TWR is contained in NCN-5429. As noted above, the v

'IWR provides the bending stress ratio for each nozzle connection. It is noted that none of the nozzles are considered to be overstressed; however, the nozzles with i

1

- _ _ _ _ _ _ _ _ _ - - 1

N .c.sM. -.,ML , ,, ;. . e,vM .; ,, p,. .f. ,. , , ., 1W.,.

,,.. ~.. .

ENGINEERS Sedal 15150120R3 m TECHNICAL WORK RECORD Engineer D. SHUE ]

Date 5/R86 I

Projed Title Sum ==rv d Rae'nr Caalant Pumn hrmal Barrier N=*1a Reworks Tab.AC. Page_1., of 1_

y durinn Refuel-R =ad 9 ner NCNs 5166. 5415. 5429 and 5429A the highest stresses were detennined to have the highest probability of failure concurrent with potential weld flaws.

1 It is also noted that clarification is required to better understand the table at the bottom of page 2 of the subject TWR. In the right most column of the TWR

' entitled "VCS Observed Nozzle Defects In Pump" , "yes" means that the subject pump had a history of nozzle defects prior to inspection of the CCW nozzles. The "C" RCP had the work of NCNs-2765 and 5166, and the "A" RCP had the work of NCN-5415.

l 'Ibe "A" and "C" RCP CCW Inlets were subsequently inspected. The "A" Inlet l was found to have existing weld flaws. The "C" Inlet was found to be acceptable. l l NCN-5429 was written to address the weld flaw in the "A" RCP CCW Inlet.

j Disposition 1 of this NCN provided a Rework to replace the nozzle with new t

material and remake the nozzle to pump weld. Additionally, Disposition 1 lv required that the "C" RCP CCW Outlet nozzle be inspected. This was based on l the fact that the nozzle had the third highest bending stress ratio.

The "C" Outlet nozzle was inspected and found to be acceptable; however, Refuel-j 9 Outage Management made the decision to inspect all of the RCP CCW nozzles from a prudency standpoint. Suprisingly, out of these inspections, the "A"RCP Outlet nozzle and both nozzles on the "B" RCP were found to have weld flaws, l

although there bending stress ratios were very low.

It is additionally noted that the "B" RCP CCW Inlet exhibited signs of through wallleakage. Subsequently, this line was penetrant tested which confirmed the =

l presence of the thr ough wall indication; however, it is noted that during flange l

l disassembly to correct the subject indication, a pipe snubber, CCH-1374, was foundlekad See NCN-5442 for details concerning the snubber.

The "A" RCP CCW Outlet was rap 1--A per Disposition 2 to NCN-5429.

Associated NCN-5429A was wdtten and dispositioned in Disposition 1 to allow l

for replacement of the Inlet and Outlet nozzles on the "B" RCP. After initial I

, replacement, the CCW Inlet nozzle on "B" RCP failed the post replacement test l utilizing the EPRI probe and was again replaced. This replacement occurred per l Disposition 2 to NCN-5429A.

A summary of all the work perfonned to date and the associated work documents is included as Table I of this TWR. This table lists the NDE and corrective action I work documents for the nozzles sorted by the applicable nozzle and RCP.

)

a. . : .......,..:.... ... -'^^';.=^".... .

"*"" .--.; . ., . T.f. T

.. W

.: l

. 1 ENGINEERS Serial 15150-120R1 v TECHNICAL WORK RECORD Engineer D.SHUE Date - 5/8B6 Project 11tle Summary of Recor Coal *nt Pumo hermalBarrier Nozzle Reworks Tab _RC. Page 4 of _J_

v during Refuel.R and 9 per NCNs 5166. 5415. 5429 and 5429A 10CFR21 EVALUATION: The subject condition appears to be a generic hardware defect in manufacturing

" of a basic component which has the potential to cause a loss of safety function and a major reduction in the degree of protection provided to public health and safety.

Because the nozzle weld defect are in both the Seal Injection and Component Cooling Water connections at the Reactor Coolant Pump Thennal B arrier Flange the potential exists that both could fail simultaneously. Should this occur there would be no cooling to the RCP seal or lower pump bearing. Both would be subjected to Reactor Coolant System cold leg temperature in excess of 550*F.

This has the potential to initiate a RCS cold leg loss of coolant accident. See Westinghouse WCAP-10541 and NRC Generic Issue 23 for possible safety significance.

s 18CFR50.72/73 EVALUATION: Providedin a previous disposition.

10CFR50.59 EVALUATION: Not required for Sis type disposition.

CAUSE AND CORRECTIVE ACTION: The cause of the subject failures appears to be associated with the initial welding of these nozzles by the OEM. NCN-5166 provided an initial review of these nozzle. problems and subsequently Root

_ Cause 508-108 was issued to further address the issue. Cunently, it appears that there may be evidence ofincomplete penetration and subsequent flaw initiation. This has been corrected by removing and replacing the subject weld.

6... S N.N

. W. NENW

.. . . . ... W!K M G.M . . . . ..

1

. . . j j

ENGINEERS Serial 15150120R3 l l

. TECHNICAL WORK RECORD Engineer _A SHUE_

Date snug 6 Project Title Summarv of FamMar Conlant Pume Thermal Barrier Nanla Reworks Tab.EC. Pagel of 1 v durina Refuel-8 and 9 per NCNs 5166. 5415. 5429 and 5429A l l

l TABLEI l REACTOR COOLANT PUMP

!v SEAL INJECTION & COMPONENT COOLING NOZZLE INSPECTIONS \ REPLACEMENT l l SeatInjecdon to CCWInlet to CCW Outist from TherrnalBarrier Thermal Barrier Thermal Barrier l RC PUMP NDE Nozale NDE Nazak NDE Nozak I

LOCATION ~

Replacement DW-nt Replacanes l 96D3051 96D3053_ 96D3053

! "A" 95Q3112 NCN 5415 96T3158 NCN-5429. #1 96T3158 NCN 5429.#2 i

~ 4/28/96 (Note 3) 5/IM 5/4 M iHiAbsp'taWiwir 96D3056 96D3056

( "B" 95Q3115  %!#1hNot/liini 9 96T3161 NCN 5429A. #1.2 96T3161 NCN 5429A. #1 l WNIMOM ii 5/3/1996(Note 5) SS/96 i 94Q3079 94D3240 fd E - = "

• P 4M W 9 " ""

l "C" 9603024 NCN-5166 96T3159 HlWifN6ttN4 $ M 96T3159 @@lIISWdialient j y (Notes 2 & 3) 12/5/94 l!LWRisinitun?MS #3f!ReiguiredMS Noses: 1. An unas more reinapsewd armi carreeJve nedei udlising to anaw EPRITmhnique that fand the unld as=o 2 - The remaining *C" Scat h)rtion uns OEM

• eld was soplaced la 19M due to inihare and reinspessed h 1996 3 - De "C" Seal hjaalen une was perdauy replaced in 1987 per NCN.2765 dus to ihraush wmu failure 4 The *A* CCW Inist une was penetrant lesad and found to have a asknal through waU lsak in 1996

! 5 De 'B' CCWInler une fausd pet sold kirpaalan fe Dispaaltie 1 ad the Rowerk was xsparformed par Disposition 3 E/Mf$@Nozzk Myable - Rephemmeni not Requitud i

e i

t A

$ Y

>