ML20062M743

Intervenor Exhibit I-MFP-63,consisting of Nonconformance Rept & Mgt Summary Ncr DC2-92-TN-N028,Rev 00, Leak in Asw Annubar Line & Corrosion on Components in Pipe Trench,

ML20062M743
Person / Time
Site:	Diablo Canyon
Issue date:	08/19/1993
From:	AFFILIATION NOT ASSIGNED
To:
References
OLA-2-I-MFP-063, OLA-2-I-MFP-63, NUDOCS 9401110171
Download: ML20062M743 (42)

Text

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3. ItemIActivity Luh -ir ASW Annubar Line/A9/ E*I*'*n** N/A l

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i I A hole of approximately 1 1/2" in diameter was found in the ASWannubar.ilfner

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Upstream of SW-2-865. This is considered a nonconformance per 0AsD'.T.

I paragraph 2.1.8. -

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' 6'. it ted /s) 7. Organisetten S. Bote i . (p/s) 10. ergenisatsen H. Data l l 1 Gr ff Tech Sves If 7W M Mer Tech Sves A 2. feCN Ewaldtion Att.ched on the NCR Test Cent tien S N ta h I. Plant Conditions 111. e of Probles V. Corrective Actions - i i A 11. 44rscription of Problem IV. Analysis of Probles TI. Additional lafermetion  !

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u. Eatiested 15. Responsible I i E s u. Tr.nd i Other coepietion Orsanisatten e i Cs Il-11Iii1-11I Il-11I a te M S N

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P Tes [ j No l) Yes l l Mc l ] Ves lj We !I J L i R 20. Essis 8

7 j A Initial 21. Time Limit 22. Method 23. Notified By 34. Time 25. Date .

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E 1 i V L Fellowup 26. Seguired 27. Tina Limit .24. LIR No. 29. Date 1 1 Rep:-* Ves [ ] We { ]

E T I W Y 30. Other Agencies hetified l 31. Remasks ,

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, r 34. QA (p/s) 35. Date - 42. Other (p/s) 43. Date

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V M. QC (p/s) 37. Date &&. Other (p/s) &S. Date A

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St. Reg. Comp. for DCPF NCRs 39. Date 46. Other (p/s) 47. Date enly (p/s)

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P5RC 68. Meetang Date 49. GohFhAC kettiacassen Dates

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i a Corrective 50. Complete - TRG Chairman (p/s) 51. Date 52 94 verification by (p/s) 53. Date d

Action i

- 9401110171 930819 PDR ADOCK 05000275 Isis t riteut ion g PDR

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) NFC Materials PSRC Secretary Manager. QA ,

Station / Hydro Construction Initiater j Plant Manager, DCPP ,

TES Appropriate QC

, 00NPP.AC Secretary Autherised Inspector, Other *

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Engineering if applicable other i ( -

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NCR DC2-92-TN-N028 Rev. 00' Octobere21, 1992 '  ;

NOTE: DETAILS REGARDING DIESEL FUEL'OILLTRANSFER LINEi .;

CORROSION IN THE TRENCH BEGIN ON PAGE.18.

1 MANAGEMENTE

SUMMARY

On June 18, 1992, a hole approximately_lt" in diameter-was). ,

discovered in the Auxiliary Salt: Water (ASW) annubaripiping. r for ASW train 2-2. The leakirate throughithe-. hole upon '

discovery was estimated;to be less than 50 gallons per minute. After grinding away the coalitar coating'and corrosion products, the hole.was approximately 2"'xil 1/16". .

Other corrosion flaws were' identified in the:ASW.annubar- '

pipes, the worst case being on the 1-1 annubar;;however, no 5

other through-wall holes were-identified. All'annubar:

piping was replaced in Units 1-and 2 as'anlimmediatef

~

corrective action. 1

Subsequent inspection of other^ piping

in the' Unit'laand, Unit" '

l 2 west buttress area pipe' trench /concretefpipeway identified t

3 other areas of corrosion on the cardox'and diesel fuel oil (DFO) transfer' lines. Details begin'onlpage118. ,

The root cause for both events, basedLonLexamination ofi-the [

hole and the other corroded areas,'is external general ~

cor- sion' due to a degradation .or -breakdown 1Ln the coal tar ,

! _m coating-exposing the pipe--to standing / water and the i L-

' saltwater air environment.  !

Corrective actions to prevent recurrence =of the ASWcannubar corrosion include: a change in'the annubar-pipe material..to l a new corrosion-resistant. material, new' bolting and' insulating kits, and sacrificial anodes on the buried-portion of the 24"' piping, and additional 1 investigations of '

potential corrosion on the ASW and other; plant systems.

Refer to details beginning on.page 18'for cardox and DFO' transfer line corrosion corrective actions to' prevent .

f recurrence.

i 92NCRWP\92TNN028.PSN Page 1 of 40 f- ,

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-NCR DC2-92-TN-N028 Rev.-00 October 214 1992 .

NOTE: DETAILS REGARDING DIESEL FUEL. OIL TRANSFER LINE CORROSION IN THE TRENCH.BEGIN ON:PAGE 18.

NCR DC2-92-TN-N028 LEAK'IN ASW ANNUBAR LINE AND CORROSION ON' COMPONENTS IN PIPE'TRENCE-I. Plant' Conditions '

Units 1 and.2 wereiin Mode 1 (Power. Operation) at.100t' power.

II. Description of Event A. Sununary: y On June 18, 1992, a hole approximately ll""in diameter was discovered in the Auxiliary Salt-Water.annubar piping-for ASW train 2-2.~~Other-corrosion' flaws were also identified in the?ASW' annubar pipes. Subsequent inspection'of other:

piping in the Unit 1 and. Unit 2' west buttress area-l pipe trench / concrete pipeway. identified areas of corrosion on the cardox and dieser fuel oil (DFO)-

transfer lines (ref. 2, ref.=3).

B.

Background:

The supply lines from the Auxiliary.SaltLWater (ASW) system to'the Component: Cooling Water (CCW)

~

l system are buried 24" pipes, lined with a.

polyvinylchloride inner "paraliner" and-a coal. tar outer coating to prevent. corrosion (ref. 8).. The annubar pipe is a'4" diameter, schedule 140 (ref.

pipe specification G1,.dwg. no. 047219) pipe, internally paralined and externally; coated with-coal tar. The annubar pipes extend from~above ground to connect to the buried ~ASW' pipes, and are used during ASW. system flow measurements.

The horizontal pipe trench / concrete pipeway where the vertical annubar pipestexit from the ground also contains two cardox supply lines-and a-diesel fuel oil transfer line,-which'run; horizontally in the pipe trench.

92NCRWP\92TNN028.PSN Page 2 of 14 0

.t:

I

'NCR DC2-92-TN-N0281Rev.E00- -

2 > October- 21, 1992 ,

1 l

The Technical ~ Specification ~(TS) governingLthe-ASW' system is TS"3.7.4.1. It requires,that two trainsi  ;

of ASW shall~be operable ~in ModesEl', 2,E3, and14'- , i with a 72-hour Action Statementhif only-one train' ,

is. operable. .Although not l the TS, the ASW system is lso a(specifically stated required to' operate in-in support of the CCW system in Modes 5-and 6.- ,

1 The annubar piping is_ safety-related:PG&E Code-  !

H Class C pipe, which is. classified under ANSI . q Boiler & Pressure. Vessel Code B31.7-as Code Class j 3 (considered'the-same as A,SME Code. Class-3:for' ASME Section XI and'TS purposes). TS 3.4.10 l

requires that structural' integrity of ASME Code; I Class components be maintained, and TS:3.4.10 Action c.-requires that with the: structural-integrity of any ASME.CodeLClass'3 components.not2 conforming to code requirements,4the plant must.

" restore the structural integrity;of the affected component (s) to within'its limit or isolate:the affected. component (s);from' service.'"

1 NRC Generic' Letter (GL) 90-05' states'that the NRC -

staff considers temporary. repairs that are not.in compliance with Section XI'of thefASME Code to be.

unacceptable without specific written relief granted by the NRC. The GL:provides guidelines' for a calculation ~to demonstrate the stability of~

i the flaw and acceptable structural integrity ofL the remaining pipe,~to be. performed as supporting information for a relief request (ref. 4).' A supplementing NRC memorandum-provides:

clarification and outlines'the acceptability of

" stopgap" repair ~ measures-to limitcleakage while-preparing a relief request for a non-Code repair (ref. 4). .

C. Event

Description:

l

1. On June 18, 1992, a hole approximately ll"Lin .-

diameter was discovered'in the annubar' piping.for ASW train 2-2. Theileak rate through'the hole at the time of the discovery was estimatedito be less than 50 gallons per' minute (ref. 2). j '

On June 18, 1992, at 1735 PDT, ASW train!2-2.was isolated and TS;3.7.4.1 was entered.. A soft' patch; was installed to limit'theileakage (ref.:2).. ,

92NCRWP\92TNN028.PSN Page 3 of 40

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t' j NCR DC2-92-TN-N028 Rev.-00 October 121,11992 .

The installed soft' patch consisted ^of.two pieces of 1/8" rubber gasket material,. backed'with!

garlock-gasket, bonded togetherJin a" laminate ]  :

fashion using adhesive. The soft patch was~ _

attached to the pipe using hose-clamps.. No credit ~

was taken for the soft.patchiin safety evaluations because it was neither.an-ASME. Code-approved-repair nor:an NRC-approved.non-Code repair, and.

the as-found condition-could not< meet the Generic Letter 90-05 criteria. However,Lthe patch did provide leak-tightness.(ref.12).

On. June- 18, 1992, at'2053'PDT,JASW train:2-2-was declared operable'and TS 3.7.4.1 was exited. - The  !

basis for the operability determination-is '

)

documented in Jul A0269002 (ref. 2), and;is i summarized las -follows : - The soft patch was leak l l

checked with'the system in the lineLup for a safety injection (SI), and; system pressures,- y remaining pipe wall,.and' seismic analyses were  ;

considered. Even-with_the as-found leak,Jthe'ASW  ;

system would have_been capable of supplying l 1

sufficient flow to perform its' safety function (ref. 2). l On June 19, 1992, Event" Responsej Plan ~(ERP) '92-6 was initiated to investigate and document ,

immediate corrective actions. l There were water marks and. evidence ofiprevioust ~

conditions of standing waterfinithe. .

I trench /pipeway, based on' visual 7 observations by DCPP Mechanical Maintenance. -There wastcorrosion.

surrounding tne hole,:such thatJthe' hole 1 tapered from approximately-2.1/8"'x l'5/8" at the outside.  ;

diameter to the 1 1/8" x 1 1/16" hole at:the' '

inside diameter (see Attachment.1,:also'ref. 3 ,

Action Item #7). The edge of the paraliner at the hole was smooth, and there were no: cracks-in the concrete at the interface in'the trench'where the pipe enters the ground'(ref. 7).

A calculation was' performed demonstrating-that the l ASW system remained-capable of supplying adequate; cooling to.the CCW heat 1exchangers,'with-specific .I ocean water conditions, even: assuming a1 guillotine pipe break in one'of the twoud" annubar_ pipes per)

Unit (ref. 2, ref. 5, ref. 6)..

92NCRWP\92TNN028.PSN Page 4 of 40

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t NCR DC2-92-TN-N028 Rev. 00 .

October 21, 1992 The coal tar coating and corrosion products.on the.

2-2 annubar were removed in1 order'.to perrorm accurate ultrasonic thickness-(UT) inspections. )

The final dimensions of the hole _after cleaning down to bare metal.were approximately 2" x l '

1/16". There were no cracks identified by.

magnetic particle testing:(MT)'of the metal surrounding the hole.- Other corrosion-flaws were.

identified; however,'in~all cases the thickness of

~the 2-2. metal pipe wall was greater:than'O.210",

with the exception of the hole and'another flaw-with a minimum thickness of 0;100" (ref. 3,. Action Item #9, and.ref. 7).. The-inner diameter of-the-paraliner was. visually inspected'with a boroscope? 9 and was found'to be in good condition, except for j the hole caused by:the external' corrosion (ref.-  !

7).

In accordance with Generic LetterL90-05, a-flaw

~

l evaluation was performed for-the 2-2Tannubar (ref. '

l 3, ActionLItem #7), but could not demonstrate that-the as-found condition met the acceptance. criteria ^

l of the Generic-Letter. . Consequently, DCPP.did not submit a' relief request.to the NRC to allow a temporary non-Code repair:of the 2-2 annubar, but 1

instead performed a permanent Code-approved.

repair.

Visual inspection of the other thre'e ASW annubar pipes indicated significant-corrosion on 1-1"(ref.

7), although'no otherLthrough-wall holes were identified.

The corroded' areas on.the 1-1 annubar-pipe were cleaned in order!to allow'UT' measurements of the' remain'fng! wall thicknessi and the worst-case remaining wall thickness on.the.1-1 annubar was 0.029" (ref.-3, Action _ Item'#9). -The evaluation performed for this' flaw was'able to-demonstrate that the GL 90-05 criteria are met (ref. A0269111).

l l

2. Subsequent inspection.of other piping.in the pipe-trench identified other areas of corrosionLon the-l cardox and diesel fuel oil transfer 1 lines-(ref~ .

! 2). .The ERP initiated an' action; item to inspect these lines along the entire length:of the pipe trench and attempt to identifyLthe' areas with'the-worst. corrosion. These flawed areas will then be characterized 1to determine the' impact of the-corrosion-on the cardox and DFO systems (ref. 3, 92NCRWP\92TNN028.PSN Page .5 of 40

- . - .. ~ :.= -=--

sS NCR DC2-92-TN-N028 Rev. 00 October 21, 1992 -

Action Item #15). Additional details for cardox and DFO begin on page 18.

On July 8 and August 28, 1992,.during continued excavation to inspect the main 24" ASW lines, a hard corrosion / sand mix was'found packed around the buried main ASW flanges and bolts. . In addition, blisters were noted on the exterior surface of the 2-1 pipe. The blisters appeared to be due to external environmental conditions (not through-wall leakage), and neither condition affected the operability or functionality of the piping (ref. A0270619, A0274806).

l 3. On September 2 and 3, 1992, the outer blistered pipe coating was removed from-the four ASW pipes (which were exposed by' excavation). Small corrosion pits were found on all four'ASW pipes, l

and a corroded bolt was found on the 1-2 lead flange. The pits and corroded bolt'were not found to have impacted the structural integrity of the components (ref. A0275136). The exposed ASW piping was cleaned and recoated with a new coating-product and a local cathodic protection system was installed for the 24" dia. ASW pipes. The pipeway joint seal was repaired.

D. Inoperable Structures, Components, or Systems that Contributed to the Event:

None.

E. Datet and Approximate Times for Major Occurrences:

1. June 18, 1992; 1735 PDT: Event / Discovery date. ASW 2-2 annubar leak was discovered, ASW train 2-2 was isolated, and TS 3.7.4.1 was; entered.

2. June 18, 1992; 1735-2053: Soft patch was installed.

3. June 18, 1992; 2053 PDT:- ASW train 2-2 was declared operable 92NCRWP\92TNN028.PSN Page 6 of 40

. . .4 t'! I I

.-NCR DC2-92-TN-N028'Rev. 001 ~

4 October _ 21, 1992- ,  !

l and TS 3.7.4.1 was' exited.

F. Other Systems or Secondary Functions Affected:

l There are two diesel fuel oil. transfer' lines and two carbon dioxide fire suppression: system supply lines running along the length'of the. pipe trench. l These other lines'also'show indications of corrosion.

18.

Refer..to discussion beginning on_page G. Method of Discovery:

The through-wall hole on annubar 2-2 was discovered by Mechanical ~ Maintenance personnel.

during routine-activities in'the area.

H. Operator Actions:

Operators isolated the 2-2 ASW. train upon discovery of ' the leak and ' entered: TS;.3.7.4.1.

After installation of the soft patch, ASW' train '

2 was returned to service.and TS 3.7.4.1 was) exited'(ref. 2). . .

I. Safety System Responses:

None. 1 1

III. Cause of the Event ]

A. Immediate Cause: ,

i The immediate cause of the through-wall hole on- '

ASW annubar 2-2 appears to be external corrosion.-

B. Determination of Cause:

1. Human Factors:

a. Communications: N/A

b. Procedures: .The existing surveillance procedure did not. provide 1 instruction"for~ identification of corrosion on. piping. It has been assumed Lthat the.

problem reporting process'and 92NCRWP\92TNN028.PSN Page 7 of 40 i

NCR DC2-92-TN-N028 Rev. 00 October. 21,-1992- ,

the diligence of plant staff-would' cover.this condition.

c. Training: N/A

d. Huma'n Factors: -N/A

e. Management System:- N/A

2. Equipment / Material:

a. Material Degradation: ' The ASW annubar-sections of piping-were corroded ~due-

.to general- ,

i corrosion.. .

b. Design: N/A

c. Installation: Examination l of -the l trench /pipeway. revealed that there'were wood

. blocks andidebris.that had.

not been removed. Also, the' bottom 1/3 of the-piping was not' adequately-coated with coal tar due.

to the closefquarters in the trench.:

d. Manufacturing: N/A-i Preventive Maintenance: The current

~

e.

preventive

-maintenance program does.not specifically.

l require inspection for pipe corrosion in.the pipe

] trench /pipeway.

f. Testing: N/A

g. End-of-lifeffailure: N/A 92NCRWP\92TNN028.PSN Page 8 of 40

i i I

NCR DC2-92-TN-N028 Rev. 00. 1 October 21, 1992= ,

.]

C. Root Cause:

l The root cause, based on examination of.the hole.  !

and the other corroded areas, is. external: general corrosion due to a degradation or breakdown in the coal tar coating. exposing the. pipe to standing water and the saltwater' air environment. Standing.

water seeping through the. coating would. corrode the pipe, especially.at the water / air interface. J As the iron oxide rust formed, it would expand 1 significantly in volume (at a' volumetric ratio of approximately 7 to 1). This bulging or. blistering-would further degrade the coal tar and exacerbate:  !

the corrosion process (ref. 7).- The smooth edge-  :

of the~paraliner at the hole supports the postulation that the wall of the pipe corroded-l away until either normal operating pressure or a ,

pressure-transient " blew out" the liner-in that.

) area (ref. 5). The standing water was due to .

l inadequate drainage,1 caused by. flow blockage by'  ;

l P i Pe supportsfand external debris.

D. Contributory Cause:

.s.

l See p. 26 for DFO' contributory causes.

l IV. Analysis of the Event A. Safety Analysis:

As discussed in OE 92-14, the ASW systemLwas

-determined to have been operable, even with the-as-found through-wall _ hole. The ASW' system'would i have been'able to provide adequate' cooling 1 water, given the existing ocean temperature conditions. o Therefore, this event did not adversely affect-the health and safety of the public. ,

B. Reportability:

l 1.

Reviewed under QAP-15.B and determined to be.

s i

non-conforming in~accordance with Section 2.1.8.

2. ~

Reviewed under.10 CFR 50.72-'and 10 CFR.50.73:

per NUREG 1022 andLdetermined to be.not.

reportable in accordance~with 10 CFR.50.73.

As discussed in OE 92-14,fthe ASW systemEwas still operable with the as-found hole.in the 92NCRWP\92TNN028.PSN Page 9' of 40 l H l

48 l

g.

NCR DC2-92-TN-N028 Rev. 00 October 21, 1992 .

annubar. Therefore, ASW TS wereinot violated.-

(NOTE: .A voluntary report was. submitted regarding DFO: corrosion. See reportability l discussion'on page 28-below.).

3. This problem will' not require-a 10 CFR Part 21 report, since (a) it is'being evaluated under ,

10 CFR 50.72 and-50.73,.and;(b) it does not involve defects in vendor-supplied services or ,

spare parts in stock in the warehouse.

4. This problem will.not be reported ~via ansINPO l Nuclear-Network entry.. i NOTE: DFO-corrosion;was. reported to-INPO.--  ;

See p. 28 below. .

1

5. Reviewed'under 10 CFR.50.9-and: determined to be not reportable since this event does not have a significant. implication for public  ;

health and safety or-common defense.and. _

security.-

I

6. Reviewed under.the criteria.of AP C-29 t

. requiring the issue and approval of an.OE andL determined-that an OE is required. OE 92-14,-  :

Revision 0, was approved by PSRC on June'26,.

1992-(ref. 5).-

V. Corrective Actions i

A. Immediate Corrective Actions: j

1. A temporary 4 soft 1 patch was:irstalledito limit leakage from the hole (ref. 2).: . Subsequently, the four annubar pipes for Units ILand 2 were-replaced with a new corrosion-resistant material (ref. A0269551,'ref. 3).

2. Event Response Plan (ERP) 92-6 was initiated to document immediate' investigative-and-corrective actions.

3. Operability Evaluation (OE) 92-14 describes the continued operability.of'the~ASWfsystem with the condition described in this NCR. .)

l

. 1 92NCRWP\92TNN028.PSN. Page 10 of 40L i

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NCR DC2-92-TN-N028 Rev. 00 -

October 21, 1992 .

B. Investigative Actions:

(See page 30 below for DFO Investigative Actions)

~

l

1. Event Response Plan (ERP) 92-6 was initiated l

to document immediate investigative and corrective actions.

l 2. Obtain the finalized metallurgical corrosion analysis for the ASW annubar section.

(This AE tracks closure of ERP 92-6 Action Item (13)

RESPONSIBILITY: C. Groff ECD: COMPLT DEPARTMENT: Tech. Sycs.

Tracking AR: A0269233, AE #06 i

3. Develop a plan for P. comprehensive review, to l identify other systems with safety-related piping and conduit that may be susceptible to i similar general corrosion. '

(This AE tracks closure of ERP 92-6 Action Item #20)

RESPONSIBILITY: C. Groff ECD: 12/1/92 DEPARTMENT: Tech. Sves.

Tracking AR: A0269233, AE 404 NRC Commitment? Yes 4.

l NECS to issue DCN to further excavate around all four of the main 24" diameter ASW pipes to inspect the flanges and bottom side of the pipe.

RESPONSIBILITY: D. Wong ECD: RETURN DEPARTMENT: NECS - Civil Tracking AR: A0269233, AE 407

5. Develop a plan to perform corrosion studies on ASW piping to include corrosion specialists from both TES and ENCON Civil.

(See Corrective

1. 1-#3 on page 12Actions below.)to Prevent Recurrence RESPONSIBILITY: T. Nelson ECD: COMPLT DEPARTMENT: System Engineering Tracking AR: A0269233, AE #08 92NCRWP\92TNN028.PSN Page 11 of 40

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NCR DC2-92-TN-N028 Rev. 00 '

OctoberH21, 1992 .

C. Corrective Actions to' Prevent Recurrence:

1. Complete the excavation, inspection, and replacement of the bolting forLthe 24" flanges- l on the ASW piping. . Based on'the. .

recommendations of the corrosion engineer,

~ install _an insulating kit',.and sacrificial .

anodes as required. Develop contingency plans. l to repair / replace the piping if severe corrosion is found,iand implement if needed.

(Reference A0269551, A0270619)'

RESPONSIBILITY: K. Brungs ECD: 9/15/92'

~

DEPARTMENT: . NECS-Civil ,

Tracking AR: . A0269233,,AEl#12 Outage Related? No

~

l OE Related? No-  !

NRC Commitment? No I CMD Commitment? No

2. Revisit the original l corrosion studies performed by TES in:the early 1980s.

Corrosion specialists from TES and ENCON Civil" should be involved. The-study.should include:

a. Excavation-of a number-of the Dresser couplings:for. inspection andl installation of test leads. -Consider' electrically bonding.the Dresser-couplings and the pipe in preparation'for. installing a cathodic protection system.-

b. Inspection of the pipe where it' enters ,

some of the thrust blocks, due to the; potential? difference between the pipe and' t tha r u nforced concrete. '

c. Investigation of the soi1' resistance along the pipe to find' locations-offspecial' Concern.

d. Consider excavating where the ASW line .

exits the. intake structure. This may-prove necessary due to the' probable saltwater.in that location.-

e. Develop and implement, as'needed, a contingency plan for-repair /replacementlof 24" ASW-piping if severe. degradation is discovered.

RESPONSIBILITY:- Nelson /Wong- ECD: 12/31/93 DEPARTMENT: Sys. Eng/NECS - Civil Tracking:AR: A0269233,-AE #14-92NCRWP\92TNN028.PSN Page 12 of 40

l NCR DC2-92-TN-N028 Rev. 00 -

October 21, 1992 .  !

Outage Related? No OE Related? No NRC Commitment? No CMD Commitment? No

3. Design and implement a cathodic protection system for the ASW pipes based on these investigations and studies.

RESPONSIBILITY: D. Wong ECD: 12/31/93 DEPARTMENT: NECS - Civil Tracking AR: A0269233, AE #15 Outage Related? No OE Related? No NRC Commitment? No CMD Commitment? No

4. Define the scope for Corrective Action to Prevent Recurrence #2 above, and generate an AT-EWR.

RESPONSIBILITY: T. Nelson ECD: 10/2/92 DEPARTMENT: Sys. Eng.

Tracking AR: A0269233, AE #13 Outage Related? No OE Related? No NRC Commitment? No CMD Commitment? No

5. Further generic investigations of corrosion on other plant systems will be reviewed by a Corrosion Study Group (see Investigative Action #3 above - AE #04).

D. Prudent Actions (not required for NCR closure)

1. Coordinate with ENCON metallurgy and develop a PM program to monitor the cathodic protection system installed under DCN DCl-EP-47635 for protection of the ASW piping. The PM program should abide by standard industry practice for frequency of monitoring with provision for piping inspections if conditions warrant it.

This task may be reassigned to electrical or predictive maintenance.

i RESPONSIBILITY: T. Nelson ECD:

s 12/31/92 Tracking AR: A0269551, AE (12 I

92NCRWP\92TNN028.PSN Page 13 of 40 -

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NCR DC2-92-TN-N028 Rev. 00 October 21,-1992 q

VI. Additional Information  ;

A. Failed Components:' -

1 Significant, and inione case,.through-wall; corrosion was.found on the carbon steelfannubar-piping in the ASW system.

B. Previous Similar-Events: ,

NCR DC2-87-TN-N007 STP P-78.  ;

This NCR discussed galvanic corrosion on ASW vacuum breakers. Corrective actions addressed -

minimizing direct-' contact between. dissimilar. ,

metals.and prevention.of runoff in~the ASW vault.  ;

NCR 9Cl-91-MM-N015 .ASW Pipe Support?286-72R -

Corrosion.  !

This NCR discussed corrosion on a^ pipe support in the ASW vault'. _The root cause7was< degradation of the protective coating'on-theJsupport,'butfit could not be determined'whetherstheLeoating had1 ,

been-improperly applied,-oridamagedLduring. '

maintenance.~ Corrective-actions-expanded the scope _of. routine inspectionsLto' include other

^

components in ASW and'DFO vaults (but not the-DFO-trenches). ,

4 NCR DCl-91-MM-N067 ASW Pump Vault) Drain Check  !

Valves This NCR was'de't' Ermined not toL6eLa' l nonconformance. It discussed:an event where:

debris caused the ASW vault drain check valves'to ,

remain partially open. Corrosion was not specifically-identified'as'an issueLin this-event.  ;

NCR DCl-92-TN-N002 ASW System This NCR discussed anLevent.where both trains of I ASW on. Unit-2 were inoperable. However, it wasL l subsequently determined that'one train had always been functional, iso.the event'was not a-nonconformance. Corrosion was not identified-as'  ;

an issue in this' event.

92NCRWP\92TNN028.PSN Page -14 of 40 i E

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= t NCR DC2-92-TN-N028 Rev. 00 -

October 21, 1992 .

OE 00005838 U-l and 2 ASW Pump Discharge l Vacuum Relief Check Valves Unbolted l This QE was issued to address missing bolts in the I ASW breaker valve hangers. The design was modified as a result, including the use of protective coatings on structural members..

Routine PMs and an " evolving plant corrosion program" were credited for identifying problems in the future.

C. Operating Experience Review: l

1. NPRDS:

i Not applicable.

2. NRC Information Notices, Bulletins, Generic '

Letters:

l A search of the Operating Experience Assessment database under keywords CORROSION and AUXILIARY SALTWATER SYSTEM, CORROSION and 1 COATINGS, CORROSION and EMERGENCY DIESEL l GENERATOR revealed the followings NRC Information Notice 90-39'and Generic I Letter (GL) 89-13 discuss problems identified l in service water systems. The main concern regarding corrosion was the potential for corrosion products to cause flow blockage.

PG&E's response to GL 91-13 did note that the ASW system piping.ia lined internally and externally. A limited inspection of accessible ASW piping found no significant problems with corrosion or coating integrity (ref. A0184820, AEs 12 & 13).

Other non-applicable items discussed various problems with biofouling, internal corrosion, and/or valve failures in other systems.

Generic Letter 90-05 (regarding temporary repairs of ASME Code piping) and its applicability to this nonconformance is discussed in the " Description of Event" section on page 3 above.

92NCRWP\92TNN028.PSN Page 15 of 40

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'i NCR DC2-92-TN-N028 Reve 00 -I OctoberL21, 1992 -

3. INPO SOERs and SERs:

None applicable. 'See.the abover search of'the:  :

Operating Experience. Assessment database. .

D. Trend Code: }

i YY - D (Other) - (Other,. general corrosion) j i

! E. Corrective Action-Tracking:

1. The tracking action request'is'A0269233.- i

2. Are the corrective actions outage related?

No. >

1 l

i F. Footnotes and Special. Comments': i i

As discussed in the.ERP/TRG, no previous NCRs on corrosion'had required ~ performance of'an.  :

l inspection of the full length of these piping trenches. j G.

References:

1. - Technical Specification 3/4.7.4.1 (ASW System). .. .

i Technical Specificaticn 3/4.4.10 (Structural integrity)

.i

2. -

Initiating Action Request A0269002 (2-2 l annubar)  !

j Shift Foreman Log, dated 6/18/92 Action'Lequest A0269111;(1-l'annubar)  !

Action Request A0269118 (cardox line).

Action Request A0269152 (diesel' fuel' oil line)

Action Request A0269398 (repair-of DFO line. ,

below min. wall thickness)

Action Requests A0270619,'A0274806'  ;

(corrosion foundlon buried 24" ASW piping) '

Action Request A0276136 (evaluation of- ,

corrosion on buried 24"LASW piping)

3. Event Response Plan (ERP)-92-6, "ASW Annubar. i i

Piping Leak"

4. NRC Generic Letter 90-05 dated June 15, 1990-92NCRWP\92TNN028.PSN Page 16 of 40 ,

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l .

I NCR DC2-92-TN-:028 Rev. 00 '.

October 21, 1992 .

Memorandum from Director, NRR (USNRC) to l

' Regional Directors (USNRC), dated Aug. 16, 1990

5. Operability Evaluation (OE) 92-14 l

6. Engineering Calc. No. M-923, Rev. O I

7. -

E-mails from DGW1 to various, dated June 20, 1992, re: ASW annubar 2-2 pipe inspection (see also ref. 3, Action Item #9)

E-mail from JEA3 to various, dated July 23, 1992, re: " ACTION PLAN FOR ASW PIPE CORROSION"

8. Design Criteria Memorandum (DCM) S-17B, i

" Auxiliary Salt Water System" l 9. -

Engineering Calc. No. M-910 WCAP-12526

10. E-mails regarding DFO safety analysis

11. Licensee Event Report (LER) 1-92-006

12. Previous corrosion on DFO lines ARs A0180877, A0178470

13. Memorandum from NECS (P. Hirschberg) to DCPP (C.

Groff) dated August 27, 1992, re: " Evaluation of DFO Piping"

14. -

Letter from CERCO (J. Howard) to PG&E (D.

Wong), dated July 23', 1992, re: " Aux 1 Alary Salt Water Pipelines Corrosion Evaluation &

Cathodic Protection Feasibility Study" Memorandum from Civil Engineering (D.

Schubert) to Diablo Canyon Power Plant (D.

Wong) dated July 17, 1992, re: " Diesel Fuel Oil Line and Bangers" Memorandum from Civil Engineering (D.

Schubert) 1992, re:

to DCPP (D. Wong) dated July 30, ,

i "DCPP Diesel Fuel Oil (DFO) Line and Auxiliary Saltwater (ASW) Pipe Lab l

Evaluation" B. TRG Meeting Minutes:

4 ERP and TRG meeting minutes begin on page 32 below.

92NCRWP\92TNN028.PSN Pagra 17 of 40 I

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' NCR DC2-92-TN-N028 Rev.-00 October- 21, 1992 .

l NOTE: DETAILS REGARDING AUXILIARY SALT WATER ANNUBAR l CORROSION.IN THE TRENCH BEGIN ON PAGE 1.

MANAGEMENT

SUMMARY

On July 2, 1>92, ultrasonic testing identified'one location on the DFO train 0-1 piping below the-minimum wall thickness requirement;'this piping was. replaced.:

However, a subsequent engineering evaluation-concluded that the piping would have remained operable under all design basis loading conditions..

The root cause of the event was general corrosion-due-to a degradation or breakdown in the coal tar coating exposing _

the pipe.to the standing' water and saltwater air environment.

Corrective actions to prevent recurrence include: (1)-

revision or creation of an inspectioniprocedure to-emphasize visual inspection for corrosion as well as . i leakage, (2) development and implementatica of a repair program to repair and/or replace.the remaining areas of corrosion on the DFO piping, and-(3) a comprehensive review to identify other systems with safety-related piping and conduit that may be susceptible to similar general corrosion.

1 l

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NCR DC2-92-TN-N028-Rev. 00 -j'

... October 21',-1992 . 1 1

I. Plant Conditions Units 1 and 2'were in Mode 1 (Power Operation) at 100--

percent power.

II. Description of Event A. Summary:

)

On June 21, 1992,, corrosion'was discovered on: i piping associated'with the diesel fuel oil;(DFO)

,j train 0-1-and the two' fire suppression ~ system  :

l carbon dioxide-(cardox) lines contained in a pipe l l trench /pipeway located in the' Unit.2 west buttress l l area trench. Immediate visual inspection of the-corroded-areas evaluated the pipe to be op'rable. e '

l On June 23, 1992, at_0240 PDT, the DFO train 0-2  ;

I was removed from service for'the tie in of the new- i emergency diesel generator-(EDG).2-3.

l '

i On July 2,'1992, ultrasonic-testing.ident'ified-one location on the DFO train 0-l' piping below the minimum-wall' thickness' requirement; this piping- -

was subsequently, replaced.-

oOn July 8, 1992, plant management conservatively determined that, because the corrosion experienced :J by the-DFO system piping mustLhave. required a significant: period of time to degrade below a minimum wall condition, Technical Specification 3

i (TS) 3.8.1.1 action g. may not'have been met. In- '

addition, since DFO train;0-2Lwas-removed:from service on June- 23, 1992, at 0240 PDT and DFO-  !

train 0-1 may have been~ inoperable'duc toLthe' minimum wall conditions, TS 3.8.1.1 action h.~may.

not have been met. ,

However, an engineering evaluation concluded that; the piping would have remained-operableLundertall design basis loading' conditions.

B.

Background:

The DFO system supplies fuel-oilito the Unit'l and' Unit 2 EDGs~. .There are two redundant DFO: pipe trains-0-14and 0-2. These two trains each consist' of a 40,000 gallon underground diesel fuel oil:

1 storage-tank,-a fuel. oil transfer-pump, and associated piping, filters, and' valves.-

92NCRWP\92TNN028.PSN Page- 19 of' 40 m

\

NCR DC2-92-TN-N028 Rev. 00 October 21, 1992 .

The.DFO transfer system supplies diesel: fuel oil _!~

from the underground storage tanks.to the individual diesel-generator day tanks. The day tanks have a capacity of 572 gallons but contain a minimum of 200 gallons of.DFO for each EDG at all times. Each EDG uses approximatelyn200 gallons per hour.at a full load of.~2650 kilowatts.

TS 3.8.1.1. action statements!g. and'h. govern the DFO transfer system. With one supply. train of the DFO' storage and transfer system inoperable, action

g. requires _that.therinoperable. supply train'must be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or.

be in at least hot-standby within the~next-6 hours and be in hot shutdown within-the following 6 H hours. With.both supply trains of the DFO storage I and transfer systemscinoperable,: action.h.

requires.that one supply train must befrestored to <

operable status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> ~or be-in at'least: I hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> ~and be in cold l shutdown within the following 30: hours.

TS 4.8.1.'1.3.e requires: visual examination of ,

accessible DFO piping.during an~ operating pressure. l leak test at least once every 10 years.  :

STP M-91 implements this 10-year visual inspection  !

for DFO piping leakage. LSTP M-91 is performed- I every 5 years per administrative requirements.. l l

STP M-9A, " Diesel Engine Generator Routine.

Surveillance. Test," requires'a series of"EDGctests to be performed on a frequency ranging from-1 test per 7 days to 1 test per 31 days, depending upon the number of valid starts. The. tests performed under STP M-9A determine the overall operability of a single EDG and verify that the-DFO trains transfer fuel.

STP P-12B1 (P-12B2), " Routine Surveillance Test of Diesel Fuel Oll' Transfer Pump 0-1 (0-2)", requires testing of the DFO transfer pumps on a quarterly basis.

C. Event

Description:

In February 1990, two areas of surface. corrosion were identified on the DFO piping. -At least one of the areas had been identified during the 92NCRWP\92TNN028.PSN Page 20 of 40

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4 October 21,J1992f -

}

j performance of STP M-91.. The corroded areas were cleaned, inspected, and.recoated. .For one of the i corroded areas, the maintenance _ engineer j documented on the work' order 1that.there:was no

! damage to the pipe 1due"to corrosion orLpitting.

However,.as a resultiof'thisnevent,-the, frequency

. of STP M-91. was 1 changed from :10. toe 5 years in -

{ August, 1991 (ref. 12). . This event didinotiresultl e in an inspection of-the full lengthLof.the

} buttress area piping trenches.

) On June _ 18, 1992,. corrosion was discovered in the, j Auxiliary Salt Water-(ASW)'annubar, piping. _The .

j ASW system: piping, DFO system: piping, andLthe. ~l j cardox piping are found in a common: area in'one j location of the Unit-1/Uniti2 west. buttress-area j pipe trench /pipeway. .As_ discussed above-on pages j 4 and 5,-ERP 92-6 was initiated to document i investigations and' corrective actions.-

1 1

On June 21, 1992, at Mechanical' Maintenance 1 work f

crew was inspecting the west buttress' area l

i trenches to determine- the extent ~ of lut _. l acid / caustic spilliin the Unitf2 west buttress.. - i Corrosion was discovered on.the DFO train 0-1  !

! piping and the twoffire suppression system-cardox-l lines contained in the trench.D Design'. engineering-i performed an immediate evaluati~on of thetworstL j

corroded areas identified by theLwork crc;:. , It:

) was concluded that the. piping was: operable. _An

! inspection plan was formulated to mechanically- ,

l clean the corroded. areas and non-destructively'. . '

examine the piping to determine the remaining.. wall J thickness ~(ref. 3, Action It'im-#15). l On June 23, 1992,;during implementation of the!

inspection plan, corrosion was_also identified:on.

l the DFO 0-2 train and additional ~ corrosion areas i were identified on the two cardox lines. Again, 1

based upon the findings of the, visual. inspections {

and some selective; ultrasonic thickness (UT)- i' examinations of the DFO line, these: pipes'were i

i evaluated to be operable (ref. 3, Action Item

1. 15).

On June 23, 1992, at'0240 PDT, DFO train 0-2~was j

removed from service and TS 3.8.1.1 action g. was:

~'

' entered for the tie in of'EDG 2-3.to;the DFO 0-2L train. As part of the tie in activities,_an , J 1

92NCRWP\92TNN028.PSN Page. 21 of 40 i 4 i J i a r.-_. .. _, . . . , , , _ , . . , _ . . . _ , , _ _ ~ _ , _ . , _ , - - -,._-..a___. ..._._., _-. a. .u ..m. _

i i '- l t

NCR DC2-92-TN-N028 Rev. 00 October-21, 1992 .

i operational pressure test (up.to approx. 68; psi)-

l (ref. C0090586, ref. 13) was performed'onsthe pipe  !

train. The previouslyJidentified areas-of: concern on DFO train 0-2 were observed'with no leakage i

identified.

On June 24, 1992, at 0320 PDT,JDFO? train 0-2 was i returned to service and TS'3.8.1.lfaction g was exited..  ;

On June ~24, 1992, a comprehensiveLinspection plan was developed to evaluate the condition of the-piping and associated supports on both-the 0-1 and  !

0-2 DFO trains. The plan-involved a complete 1' .

visual inspection.of the entire DFO' train from the transfer pump vaults to the-EDG. day' tank level t control valves, including pipe-supports,:and.UT.

inspe_ tion of the worst _ corrosion areas'to verifyL ,

wall thickness. t On June 25, 1992, at~'0230:PDT,EDFO train 0-1 was removed from service; and TS- 3.8.1.1 action g. was entered for the tie in ofLEDG 2-3 to-the DFO 0-1 train. Also on June 25, 1992,-the visual' inspection plan for the DFO train-O-1 was implemented. As part of the tie in'adtivities, an-operational pressure test-(up to approx.-68. psi)-

(ref. C0090586, C0102707,-ref. 13)-of the pipe'was performed. The exposed sections of the train were walked.down with no leakage identified. This, . ,

included the section of pipe on DFO train 0-1 that-

-was later found to be below minimum-wall thickness ,

requirements. _- .:

On June 26, 1992, at 0224 PDT, DFO train 0-1:was- 'I returned to service-and TS 3.8.1.1 action g.-was exited.

On June 29, 1992, the visual inspections were l completed. The visualfinspections; identified 6 areas.on.the'DFO 0-1 train for UT examination.-  !

'l On_ July 2,'1992, at?0500JPDT, DFO train 0-1 was: -j cleared and drained for the UT testing. .At 1700  ;

PDT, one location on:DF01 train-0-1 was identified; j as being below the minimum ~ wall. thickness i requirement. DFO train-0-1 was conservativelyf declared inoperable.

92NCRWP\92TNN028.PSN Page 22 of 40 o

-C NCE cd TN-N028 Rev.'00 October 21,'1992L ,

.j 1 On July 3, 1992, at 0500 PDT, the repair plans for DFO. train 0-1 were implemented. .At-1700 PDT, the l visual inspection plan for the portion.of DFO "

train 0-2 for the Unit 2; diesels wasLinitiated. -i This piping was identified by'the visual i

examination as having-the. worst corrosion. Since the UT examination did not identify: concerns with- 3 the other areas tested,.the' validity of'the visual '

examination was confirmed.

e On July 4, 1992, at 1300 PDT, the section of pipe with below minimum wall thickness on'DFO train 0-1 was. replaced and the train 0-1 was declared y operable.

On July 4, 1992, at'1500 PDT, the. visual inspection of the portion.of the DFO train'0 .

supplying the Unit 2 diesels:was-completed'and 7 '

areas were. chosen for UT examinations.

On July 5, 1992, at 1100 PDT, the UT tests on-DFO train 0-2 were completed and no: areas.of pipefwere found below minimum wall. At',1200-PDT,_the '

inspection of the portion offthe DFO train 0-2 4 supplying the Unit 1-diesels' began. At 2300 PDT, the visual inspection for the train 0-2 supply piping for Unit 1 was completed er.d 5 areas were i chosen for UT testing.

t l

On July 6, 1992,-at 1200 PDT, the UT tests'were' '

completed and no areas were found-below'the l - minimum wall thickness requirements.

i On July 8, 1992, plant management conEOrvatively.  ;

determined that because the corrosion on the DFO system piping'aust have required a significant i

period of time to degrade below;a minimum wall  ;

! condition, TS 3.8.1.1 action g. may not have been i met for an indeterminate period of time, and action h. may not have been met'forithe. period when DFO train 0-2 was removed.fromz service. A Between July 8, 1992, at 0700?PDT, Land July-13,. l 1992, the cardox supply line inspections were. "

l implemented and all lines were determined to meet-the minimum wall requirements.

l Inspections of the;DFO and cardox piping supports were also performed at the same time asuthe pipe-92NCRWP\92TNN028.PSN Page 23 of 40

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NCR DC2-92-TN-N028 Rev. 00 October < 21, 1992 .

wall thickness inspections. .Dhs a result of the inspections, it was determined that two of the DFO pipe supports on DFO train.0-1, and one cardox ,

pipe support, were degraded. A' conservative :l engineering analysis was performed and determined j that.the degraded supports would not affect the- ,

operability of the piping.

D. Inoperable Structures, Components, orJSystems that.

Contributed to the Event:. ,

l None.  !

E. Dates and Approximate Times for Major' Occurrences:. l

1. June 21, 1992: Corrosion:was discovered on.the DFO. supply piping..

2. June 23, 1992 at 0240 PDT: 9NE 3.8.1.1xaction- ,

g. enteredifor DFOL train 0-2,.EDG 2-3:

tie in and.

subsequent pipe

~

' pressure test. -

3. June 24, 1992 at 0320 PDT:- DFO-train 0-2 returned.to service and TS 3.8.1.1 action.g.

exited.- -j

4. June 25, 1992 at 0230'PDT: -

TS~3.8'.1.1 action.

g. entered for DFO- ,

'trainLO-1, EDG 2-3 .!

tie-in and- ,

subsequent pipe- '

pressure test._

5. June 26, 1992 at 0224 PDT: DFO train 0-1:

returned ~to service and TS 3.8;1.11 action g..

exited.  :

i '

6. July 2, 1992 at 1700.PDT: Event date. DFO '

train 0-1.found below minimum wall requirements.- TS:' ,

92NCRWP\92TNN028.PSN Page 24 of 40- ,

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. 1 NCR DC2-92-TN-N028 Rev. 00 -

l October 21, 1992 -

l 3.8.1.1 action 9 l entered. j

7. July 4, 1992 at 1400 PDT: Corroded section of pipe replaced. l TS 3.8.1.1 action '

g. exited. l

8. July 8, 1992: Discovery date.

t An evaluation determined that TS 3.8.1.1 action statements g. and

h. may not have been met.

9. August 27, 1992: An engineering evaluation concluded that the DFO transfer-piping was l operable under all design basis loading (ref. 13).

F. Other Systems or Secondary Functions Affected:

j Corrosion was also discovered on ASW and cardox system piping.

G. Method of Discovery:

l On June 21, 1992, a Mechanical Maintenance work crew was inspecting the DFO t'r'ench/pipeway to l determine the extent of an acid / caustic spill in the Unit 2 west buttress. Corrosion was found on the DFO train 0-1 system piping and two fire suppression system cardox lines.

H. Ope:<4 tor Actions:

On July 2, 1992, at 1700 PDT, DFO train 0-1 was l

conchrvatively declared inoperable.

I. Safety System Responses:

None.

l l

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III. Cause of'the Event A. Immediate Cause: j The immediate-cause.of the event was.DFO' train 0-1 i piping below minimum wall thickness requirements.- ]

B. Root Cause:

The root cause of the event was general corrosion due to a degradation or.breakoown in the coal tar-coating' exposing the pipe to standing. water and saltwater air. environment. Standing water seeping through the coating would corrode'the pipe ~,

-especially-at the water / air interface. LAs the iron oxide rust formed, it.would expand-significantly'in-volume.(at a volumetric. ratio of appror*mately 7 toil). 'This; bulging or: blistering.

would-further, degrade.the coal tar and exacerbate:

-the corrosion process. The standing-water was.due-to inadequate drainage, caused by flow blockage by pipe supports and external debris.

C. Contributory Cause:-

1. Existing inspection procedures did not provide" instruction for identification of corrosion on the pipes, and only required inspection of accessible DFO transfer piping.- '

2. There was' inadequate initial application and-maintenance of the coal tar protective coating l on the underside of the DFO and,cardox-piping. ,,

IV. Analysis of the Event-A. Safety Analysis:

A portion of the'DFO train 0-1 piping was found severely corroded and has been replaced. -This section of corroded pipe was judged to'have'the worst corrosion of both DFO' trains. Preliminary examination of.the corroded ~section found~some areas below the required minimum pipe' wall thickness and numerous:small pits-that were.very near through wall. The pits are1 considered _not to- i have affected operability. This was demonstrated' l when the piping was pressurized,without'.any-- '

92NCRWP\92TNN028.PSN Page 26 .of 40.

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a NCR DC2-92-TN-N028 Rev. 00 October 21, 1992 .~

indication of leakage on June 25, 1992, during tie l in of EDG 2-3.

An evaluation was performed to evaluate the effect of the degraded pipe wall condition on the integrity of the DFO piping. Seismic, thermal, pressure, and dead loads were considered. The fracture mechanics method of NRC Generic Letter 90-05 was used, except for one location, where the i Section XI draft Code Case was used. These I

methods provide a reasonable means for evaluating

! operability of a piping system that has areas of l significant wall loss in that they address the j ability of the remaining pipe wall to withstand l

design loads. The Code Case method is essentially the same as the Generic Letter, except that it is less restrictive in the selection of-depth at which the flaw is evaluated (ref. 13).

According to the design _ loads in the piping stress analysis, a minimum pipe wall of 0.071" or less was required. All flaws that were_ deeper-than the minimum pipe wall were evaluated using the fracture mechanics equations of the Generic Letter or Code Case. The result was that all of the flaws were able to meet the criteria of at least l

one of these two documents. Therefore, the pipe would have remained operable under all design basis loading conditions (ref. 13).

As discussed above in the description of the I

- event, inspections of the cardox piping and pipe  ;

supports were performed b;1 ween July 8-13, 1992. '

It was determined from these inspecticas that the existing conditions do not affect the operability of the cardox piping (ref. A0269118, A0269215, ref. 3, Action Item #15).

Based on the above analysis, this event did not adversely affect the health and safety of the i

public.

B. Reportability:

1.

Reviewed under QAP-15.B and determined to be i

i non-conforming in accordance with Section 2.1.8.

92NCRWP\92TNN028.PSN Page 27 of 40 i

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• NCR DC2-92-TN-N028 Rev. 00' October _ 21, 1992' -,

2. Reviewed under 10 CFR 50.72 and 10 CFR-50.73 per NUREG 1022 and determined to be not '

reportable:in;accordance with 10 CFR 50.73' (a)(2)(1)(B).. ,

o At the time of~ discovery of DFO train?0-1. ,'

below minimum wall thickness, train ~0-1 had  :

previously been-taken out of service;in order to measure-the wall' thickness. The affected -'

section of piping was replaced' prior to declaring the line operable;and_ returning.it to service. 10pon re-evaluation ~by senior plant management on:7/8/92 andfin subsequent ~

meetings,.it was' determined with an engineering evaluation that.the as-found--  :  !

condition would have_ remained capable of performing its design function under all-design basis loading conditions.

The below-minimum wall condition'had already.

been corrected,7and since there'was no longer ,

an existing nonconforming condition, it was .

determined that no 10 CFR 50.72. report was ,

necessary._ In addition,esince the' system j operability:wasinever? compromised, there was-no violation of TS. ~A. voluntary; report *(LER l l-92-006-01) associated with this NCR was '

submitted to the NRC.

i

3. This. problem _will not require a'10 CFR Part 21 report, since'(a) it is.being evaluated under

- 10 CFR 50.72.and 50.73, and. (b): it' does _ not involve. defects in' vendor-supplied services or spare parcs in stock in the warehouse.-

4. This problem was reported via an INPO Nuclear Network-entry (OE 5442) on July 17, 1992.

5. Reviewed under 10 CFR 50.9 and determined to be not reportable-since this event does not have a significant implication.for public health and safety or_ common? defense and_ -

security.

6. Reviewed under the criteriaLof AP'C-29 requiring the issue .and approval of am OE and ' ,

determined that no'OE is required.: - The area identified as being below minimum wall" l thickness on DFO train 0-1 has been' replaced, i

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I and it appears that the affected area was i typical of the worst identified corrosion. '

Additional inspections were performed to provide assurance that there are no additional areas below minimum wall thickness.

V. Corrective Actions A. Immediate Corrective Actions:

1

1. The section of pipe below minimum wall thickness  !'

requirements on the DFO train 0-1 was replaced (ref. 3, Action Item #15).

2. The trenches containing the DFO trains have been l

cleaned to minimize standing water (ref. 3, Action l Item #15). 1

3. Interim measures are being taken to minimize further pipe support corrosion until Corrective i Action to Prevent Recurrence #2 below (AE #03) is completed.

RESPONSIBILITY: R. Waltos ECD:

L DEPARTMENT: 12/31/93 i Mechanical Maintenance l

Tracking AR: A0269233, AE #01 Outage Related? No OE Related? No NRC Commitment? Yes CMD Commitment? No

4. - Visual inspection of both trains of DFO has been completed, along with UT examination, on the wntst accessible areas of corrosion"(ref. 3, Action Item

1. 15).

5.

l Additional visual, UT, and/or radiography examination of both DFO trains and associated pipe support contact areas is ongoing, to establish a comprehensive basis for. adequacy of the piping. ,

I RESPONSIBILITY: R. Waltos ECD:

l DEPARTMENT: 9/30/92 }

Tracking AR: NECS/ Mechanical Maintenance /ISI '

A0269233, AE #02 Outage Related? No i

l OE Related? No NRC Commitment? Yes CMD Commitment? No 92NCRWP\92TNN028.PSN Page 29 1 of 40 '

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B. Investigative Actions:

(See page 11 above for ASW Investigative. Actions)'

1. Obtain the finalized metallurgical, corrosion analysis.for the DFO-pipe'section.

RESPONSIBILITY: C. Groff ECD:' COMPLT.

DEPARTMENT:' Tech. Sycs. .

Tracking AR: A0269233, AE #10'

2. Investigate and provide additional details on'the previous ARs from the Feb. 1990 timeframe.

RESPONSIBILITY: C. Harbor -ECD:. 11/1/92 DEPARTMENT: . System Engineering Tracking AR: A0269233, AE #09 C. Corrective Actions to Prevent Recurrence:

1. Inspection procedures ~will be: revised ori created to emphasize visual inspection for corrosion as-well asileakage.

RESPONSIBILITY: R.,Waltos- _ ECD: 112/31/92 DEPARTMENT: . Mechanical. Maintenance.

Tracking AR:- A0269233, AE fil  ;

Outage Related? No  :

OE Related? No NRC Commitment? No CMD Commitment? Yes

2. A program will be developed . and implemented to repair and/or repla'ce the . remaining ~ areas of z corrosion on the.DFO-and cardor piping and l supports. The program will also address-the~ q following issues: i

1. Improving'the protective coating- '

2. Improving the drainage in.the trench

~

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3. . Minimizing standing. water in: trench

4. Improving.the surveillance program. j (Reference AT-EWR ARs A0272290, A0272368)- j RESPONSIBILITY: R.-Waltos: LECD: 12/31/93

-DEPARTMENT: Mechanical Maintenance /NECS ,

Tracking AR: A0269233,.AE #03. 1 Outage Related? No '

OE Related? No NRC Commitment? Yes a

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CMD Commitment? No 1

3. Develop a plan for a comprehensive review, to  !

identify other systems with safety-related piping l and conduit that may be '.isceptible to similar i general corrosion. l Tracking AR: A0269223, AE #04 (Also listed as Investigative Action #3 on page 11 l above)

VI. Additional Information I A. Failed Components:

The carbon steel piping in the diesel fuel oil transfer system was found corroded below minimum wall thickn.ss.

B. Previous Similar Events:

See " Additional Information" section on pages 14-16 above.

C. Operating Experience Review:

See " Additional Information" section on pages 14-16 above.

D. Trend Code:

Sae'" Additional Information" section on pages 14-16 above.

E. Corrective Action Tracking:

1. The tracking action request is A0269233.

2. Are the corrective actions outage related?

' See " Additional Information" section on pages 14-16 above.

I. Featnotes and Special Comments:

None.

l G.

References:

See page 16 above.

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H. TRG Meeting Minutes:

i On June 22,.1992,- theIinitial TRG: convened /ERP 1 l reconvened and considered the following:

The ERP/TRG reportedton. efforts overithe weekend i to remove the coalltar from the~2-2 annubar.and characterize the. hole.

Preliminary ~cales (later:

verified) indicated that the hole would NOT maintain structural integrity per GL 90-05 criteria.

t Therefore, a relief request would not:likely be approved by the NRC,'and repair options would have to be limited.to codeLrepairs- .The.two remaining options involved variations'onleither:' (1)  :

excavation, or (2)'in-situ _ weld repair, with advantages and disadvantages to both approaches.- l The.ERP will recommend to management that excavation option (s).be. pursued.

Removal of coal tar'will-proceedlon the 1-1 l annubar, since visual-inspections showed 1-2 and l 2-1 annubars generally OK. Discovery of

(

additional blistering on'other piping in:the l trench /pipeway will kne covered in this ERP.

On June 24, 1992, the TRG/ERP reconvened and considered the following::

l

- Discussion of the postulated corrosion model i indicated that' standing; water, especially atxthe water / air intet2a.;, is~~a major factork Runoff 1 from chemical spills, and possibly; galvanic  !

corrosion, may'also be factors. _The ERP will not-l focus on this trench /pipeway'only,-butLwill investigate the " big picture" of corrosionlin trenches and vaults,-and potentially buried pipe i (although buried piping: currently not thought to '

I be susceptible).

Excavation ~ options were discussed 5(scheduling, availability of new materials, logistics).

A plan will be developed to inspect this: trench (length of the turbine-bldg.) and attempt'to-characterize the impact'of the worst-case-corrosion on the cardox and DFO lines. Other 92NCRWP\92TNN028.PSN Page 32 of 40

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investigative actions were assigned to look at the

" big picture" of corrosion. The ERP will reconvene next week (week of 6/29/92).

(On June 25, 1992, a conference call was held with l NRC Region V and Resident Inspectors in order to ,

inform them of the current status of the problem, l and DCPP's action plan for repairs.)  ;

1 On July 1, 1992, the ERP/TRG reconvened and considered the following: l Inspection of the DFOT and cardox piping is continuing. Quantitative results will be available soon regarding whether tmin has been maintained on the DFOT piping.

The OE confirming the operability of the ASW system (assuming ocean temperature less than 59')

was discussed. Ocean temperatures reached 57' over the weekend; NECS is trying to increase the limit.

Options were discussed regardino scheduling of the ASW annubar replacement. The new pipe materials are being expedited, but will not arrive until next week. Management may want to go ahead :nd excavate and install blind flanges in the meantime in order to avoid having to monitor otran.

temperature per the OE.

I A status / planning meeting-(not"a full ERP) will oe j held on Mon 7/6, and work should start Tue 7/7. '

l (On July 8, 1992, a v.anagement meeting was held to discuss the potential reportability of the DFOT piping found with below minimum wall thickness.

It was determined that the condition, although currently repaired, caused a violation of DFOT'TS (therefore a 50.73 report),.but no current i condition outside design bases (so no 50.72 l report).

On July 10, 1992, the ERP reconvened to discuss the DFOT piping found below tmin and replaced over I

92NCRWP\92TNN028.PSN Page 33 of 40

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the weekend. LAlso, cardox inspections are being completed, with UT scheduled for Monday 7/13. "Two ERP subcommittees will provide white papers for management to summarize and recommend repairs;.one on replacing the'DFOT lines, the other on ASW ,

corrosion. .Some rust found on ASW components .

below-ground will require-that the OE be revised. I A new OE will be' recommended discussing the DFOT and car dox111nes. Some ERP actions'are. complete and' ready.to be signed off.

The TRG reconvened on. July 24, 1992Lat 0900 and I the following. items,were7 addressed.(see ref.~7):  ;

(1)^ Discussion on the status of-the ASW excavation.- Repairs to the annubar risers are 1 complete for.1-1.and.2-2. -The 1-2 and 2-1 risers will'be' installed next week. NECS.. l Civ!i in conjunction with System Engineering 1 has developed:an action plan'to investigate 1 further the ASW' piping. .The plan' includes:

.(a) Excavation,' inspection, and replacement of l the bolting ~for the 24 in.-flanges on the i ASW piping. Based on the recommendations l of the corrosion engineer,. insulating kits and sacrificial' anodes will be installed l

as required to allow the excavation'to be l backfilled.

! (b) Re-visitation.of the original corrosion studies-performed by TES in the.early ,

1980s'. Corrosion specialists from both i TES and ENCON Civil should be involved-to provide a well-rounded study.. A study would probably involves _m

1) Excavation o'f a'numbernof the Dresser 4 couplings for inspection'and l installation of _ test : leads. . The corrosion engineers have also suggested that we< electrically' bond .l l the Dresser. couplings.and the pipe'in-preparation for-the. installation.of a-

. cathodic protection-system. .

2) -Inspection of the pipe where-it enters some--of'the' thrust blocks, due toithe' l potential' difference between pipe and- ~

reinforced concrete.

3) Determination of the soil resistance along the. pipe to find' locations of special concern. ,

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l 4) One location considered a potential problem area is where the ASW lines exit the intake structure. Although excavation of the lines at this l location will be difficult, it may prove necessary due to the probable saltwater in that location.

(c) Plan on designing a cathodic protection system for the ASW pipe based on these investigations and studies.

i (2) Discussion on status of DFOT/cardox inspections. A sampling plan is being developed to use radiographic testing in the-pipe support areas of DFOT piping. It is apparent that this is the best way to examine pipe wall thickness in the areas where the piping and support meet. The sampling plan will most likely mimic the snubber Tech. Spec.

plan of 10%, expanding when failures are detected. -

i (3) Discussion on the DFO reportability issue.

l Regulatory Compliance presented'a draft LER (1-92-006) on the DFOT 0-1 piping below minimum wall thickness event. The need to quickly get a TES characterization of the piping defects and NECS analysis for seismic consideration was discussed. System Engineering (C. Harbor) was assigned the task to develop in cooperation with Operations, compensatory measures that would have been taken during the period when DFO train 0-1 and 0-2 ref. lines 10). were considered out of service (see (4) Establishment of the proposed root cause for the DFO 0-1 piping below minimum wall thickness. It was agreed that the proposed l

' root cause of general corrosion will be used as written in the ASW portion of this NCR (see page 8).

(5) The ERP and TRG will be merged together under the TRG chairman for closecut of investigative i

actions and corrective actions. This TRG will reconvene on July 29,-1992, at 0900, to discuss the final LER l-92-006-00.

t 1

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i The TRG reconvened on July- 29,~1992 and'consideredt j the following

. 1 The TRG reviewed and revised the'LER, specifically.

the. root cause," contributory cause, safety analysis, and corrective action sections.

Additional information on the corrosion root:cause.

will be coming from the metallurgists, and will be reported in a supplemental-LER. Regarding the l safety _ analysis, the1TRG felt ~that itiwould be ,

difficult for the' GC work crew to re-establish .i

' flow through~the.DFO-train if the opposite train

~

1 had failed during the:EDG-2-3; tie-in. clearances;  !

-however, subsequent discussions 1with NECS/OPEG '

Mechanical determined'thatirestoring some. amount?

of. flow would be'possible. . : Interim anI Iong-term i

-plans lto assure: adequate drainage.and continue q l inspections in the trench /pipeway:were discussed '

i l

The status of the ASW annubar. repairs-was updated.

Installation and testing.of the new-annubars'is -

scheduled to'be completed this week, with some i final inspections of the.ASW piping next~ week' ]

prior to refilling the excavated site. .

j Most ERP action' items are completed, and only need' .

final signatures. - AEs will be assigned for thel I remaining open ERP. items, so they can be tracked by the NCR and the ERP'can~be closed. This TRG will reconvene on Tuesday,'8/4/92.

1 The TRG reconvened on Augustf4, 1992, Land I considered the ic11owing:- 'i The draft LER root cause was discussed. lThe TES corrosion report will not be done before the LER needs to be submitted, but the bottom line is.that there was_ general corrosion of the carbon steel piping. Additional' info will be provided'in the supplemental LER if the TESjreport'also indicates other mechanisms (e.g. galvanic, pitting). ~Also, buried piping may not be subject' to exactly the same mechanism. The NCR/TRG will consider.this as-investigations _ continue. )

The TRG noted that although.the DFO corrosion was l

' discovered during' inspections from:the' chemical  ;

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NCR DC2-92-TN-N028 Rev. 00 -

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spill, we were taking actions after the ASW l annubar corrosion that would have found it. l The TRG discussed the LER safety analysis. TES has found small pits (approx. 1/32" dia.) in the ,

l removed DFO pipe that are through-wall or very '

close to it. These pits may have leaked approx.

1/2 gpm after a seismic event, but there is significantly enough flow margin (on the order of  !

1000 gpm) not to affect operability. This is still based on Engineering's preliminary evaluation that the pipe would not catastrophically fail, as the calculation will not be done until approx. Wednesday next week. With the DFO piping acceptable, current thinking is to replace it during 2RS.

The methodology for the statistical sampling of DFO pipe support locations was discussed. The i plan is scheduled to complete east trench RTs by 8/12/92, with analysis results by 8/13/92; then j the west trench RTs by 8/21/92 and analysis by i 8/24/92. l AEs were assigned to document corrective and )

investigative actions that will be LER j commitments, as listed above. This TRG will

{

reconvene on approximately 8/14/92 to discuss the l NCR, long-term actions, and the NECS safety i analysis. l l

l Based on Engineering's evaluation (preliminary at this point, but being finalized) that the DFO pApe would not fail, management determined that the LER was not required and would be submitted as a voluntary LER.

I On August 14, 1992, the TRG reconvened and considered the following:

AEs were assigned for proposed investigative and corrective actions, as listed in the text above.

System Engineering will coordinate the plans to continue investigating corrosion on the ASW system, and Corrective Actions to. Prevent 92NCRWP\92TNN028.PSN Page 37 of 40

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i NCR DC2-92-TN-N028 Rev. 00 October. 21,:1992 ..

Recurrence #1-#3 on p. 12:above will track each "

phase of this_ plan. .

NECS Engineering's finalized calculation is- ,

expected next week, to confirm.the preliminary conclusions that the Drotpiping would'have l . remained functional'in the as-found condition.

The TRG. discussed previous DCPP and' industry! j!

experience with piping corrosion. ;It: appears that utilities have not taken a comprehensive lookcat

. corrosion. 1:n the case of safety-related: salt, water systems, the problem at most plants is_an internal cement.: lining that is subject?to-degradation. Erosion / corrosion concerns are being .

studied, but this is also an internal corrosion-problem that is.different:from this NCR.. j l The investigative action.to consider 7what other-safety-related piping and conduit could-be i susceptible.to corrosion:will-take considerable

manpower. A multi-disciplinary'" task force" will- 4

! meet next week to'begin defining the scope of the ~

review.

l The additional RT. inspections.ofLatsample of DFO piping are continuing. .This.TRG will reconvene in ~

approximately two. weeks.

On August 25,'1992,' the TRG: reconvened and considered the following:. ,

Results of the TES cdtros' ion analyses'are not;yet finalized. However, NECS has the data they need' from TES and areiworking on completing'their  !

calculation'to confirm-the. preliminary evaluation that the DFO pipe, in-its as-found condition, would have been able to perform its design function to provide DFOfflow. j 1

The new task force on general' corrosion met--last"  !

H week to begin defining the scope of:the.

investigation andLactions to be taken.

InvestigativeLAction-#3 on p. 111above-(AE #04) will remain open until 12/1/92 to track _ progress.'

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The TRG reviewed the reportability section of the l NCR and revised'it to more accurately represent j the operability and reportability determinations.

l The ASW corrective actions to prevent. recurrence l were discussed, and provisions for contingency plans were added. Prior to assigning the actions

( l for the follow-on corrosion study and the cathodic protection system, an AT-EWR needs to be done to scope the jobs and get funding. A new action was assigned to generate the AT-EWR.

This TRG will reconvene approximately 9/10/92, to review the completed TES corrosion analysis and Engineering evaluation.

! On September 25, 1992, the TRG reconvened and considered the following:

The TRG discussed the status of investigative and corrective actions. The BLI for the DFO and cardox line replacement was approved approx. two

! weeks ago. For ASW, the design change to install new bolting, insulating kits, and sacrificial anodes was just completed, the exposed portions of the 24" ASW pipes were recoated, the pipeway joint seal was repaired, and the excavation has been filled back in. The vendor (CERCO) has completed their testing; however, weekly monitoring may be t

required until the testing is incorporated into the monthly STP (ref. Prudent Action on p. 13 above). AEs were assigned lo Corrective Actions to Prevent Recurrence #2 and #3 (additianal field studies of corrosion on the ASW pipes), with estimated due dates of 12/31/93 to be updated as necessary.

The TRG discussed the finalized NECS evaluation l

that the DFO piping was operable in its as-found condition (see ref. 13). The voluntary LER is being revised with this updated information.

j l

The Corrosion Study Group met again, and the TRG l

reviewed its proposed investigations._ The scope 1s now beyond the original NCR scope of only

!. buried and trenched piping, and will look at systems all over the plant (including some non-safety-related).

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This NCR will be finalized and presented to PSRC.- ,

The final writeup will be. distributed by 10/9/92, the TRG agreed to provide comments to the chairman ,

by 10/19/92, and the TRG will meet to sign.off the NCR on 10/26/92. Overall ECD for NCR closure'will ,

be 4/1/94.

I. Remarks: j i~

None.

J. Attachment (s):

i None.

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