ML20059C943

Intervenor Exhibit I-MFP-117,consisting of LER 1-92-022-00, Re Docket 50-275,dtd 921030

ML20059C943
Person / Time
Site:	Diablo Canyon
Issue date:	08/21/1993
From:	Rueger G PACIFIC GAS & ELECTRIC CO.
To:
References
CON-#194-14439 OLA-2-I-MFP-117, NUDOCS 9401060255
Download: ML20059C943 (7)

Text

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/WM so- 2.75 323 an - z I-/HFP // 7 6 M,d hregoryM.RuegerdI5EU?19 77 Beale Street i

Pacific Gas and Electric Company .

l San Francisco,CA94106 SeniorVicePresident and l

f 415/973-4684 I' GeneralManagphri, tJuclear Po,g tion l

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I october 30, 1992 ,93 T 28 P5 :48-PG&E Letter No.-DCL-92-242 U.S. Nuclear Regulatory Commission m- _;;3

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l ATTN: Document Control Desk l Washington, D.C. 20555 2: Docket No. 50-275, OL-DPR-80  !

Re:

Diablo Canyon Unit 1 '

Licensee Event Report 1-92-022-00  !

Indications on the Main Feedwater Piping Near the Steam Generator Nozzles due to Thermal Fatigue Gentlemen:

PG&E is submitting the enclosed voluntary Licensee Event Report (LER) ~

concerning indications on piping in the main feedwater system near the steam generator nozzles due to thermal stratification induced fatigue.

This report is submitted for information purposes only as described in Item 19 of Supplement I to NUREG-1022.

This event has in no way affected the health and safety of the public.

Sincerely, 7

[

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Gregcry M. Rueger cc: Ann P. Hodgdon  ;

l John B. Martin Philip J. Morrill l Harry Rood CPUC Diablo Distribution INP0 nuctrAR R!CUWORY c0VESON DCl-92-TN-N047 l

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LICENSEE EVENT REPORT (LER) 198539 FACIUTY NAME (1) DoCEET NUMBER (29 PAOE (2l 1

DIABLO CANYON UNIT 1 Ol5l0l0l0l2l7l5 Il 'l 6 P ,

wu (= INDICATIONS ON THE MAIN FEEDWATER PIPING NEAR THE STEAM GENERATOR FEEDWATER N0ZZLES Dlf' '

TO THERMAL FATIGUE \

EVENT DATE (El LER NUMBER itt REPORT DATE (75 OfMER FACILITIES INVOLVED (8)

MSN DAY YR YM SEQUEN REVl404 MON DAY YR DOCKET NUMSER (54 1 0 5 0 0 0 09 G

24 92 92 -

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6 to CFR ,

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0l010 X OTliER - VOLUNTARY (Specify in Abstract below and in text, NRC Form 366A) 7 7

i UCENSET CONTACT POR TMs LER (12)

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DAVID P. SISK, SENIOR REGULATORY COMPLIANCE ENGINEER 805 545-4420 COMPUTE ONE UNE FOR EACH COMPONENT F AILURE DESCRist 3 IN TMS REPORT (13) cAust sisitM comeONENT MA,urac. cAust sysitM A

ogt COMPONENT MAgra,c. agagt i III III I lll l -l l l lll. III suPPuMENT AL MEPORT EXPECTED (14 I lll I l -l " " " D 'E^"

EXPECTED

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l l YES (if yes, COnplete EXPECTED SUBMISSION DATE) lXl - NO - C r

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This voluntary LER is submitted for information purposes only as described 'in' .

Item 19 of Supplement I to NUREG-1022.

On September 24, 1992, with Unit 1 in Mode 6 (refueling) at'0 percent power, PG&E conservatively determined that the linear indications on piping in the main .

feedwater system near the steam generator (SG) 1-1, 1-2, and-1-3 nozzles may be beyond the American Society of Mechanical Engineers (ASME) Code Section XI flaw acceptance criteria. At 1511 PDT, PG&E made a four-hour, non-emergency report to the NRC in accordance with 10 CFR 50.72(b)(2)(i).

Based on a preliminary engineering evaluation, PG&E decided to replace the ,

horizontal piping from the 45 elbows to all four SG feedwater (FW) nozzles during >

the Unit 1 fifth refueling outage.

On October 15, 1992, a metallurgical analysis of the indications in the removed pipe sections determined that the piping near the SGs was acceptable under the ASME Code Section XI flaw acceptance criteria. -

Based on a metallurgical analysis, PG&E has determined the preliminary root cause to be thermal stratification induced fatigue. _

1 During the Unit 2 fifth refueling outage, nondestructive examinations will be performed on all four Unit 2 SG FW nozzle weld areas. 1 i 1066S/85K

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I. Plant Conditions Unit I was in Mode 6 (refueling) at 0 percent power.

II. Descriotion of Event A. Summary: i (UT) of the The Unit I fifth (IRS) refueling outagel ultrasonic test ng(AB)(N Unit I steam generator (SG)(AB) feedwater (FW) nozz eslinear ind J) near SG l-1, SG l-2, piping (SJ)(PSP) identified circumferentialpiping On September 24, 1992, at indications on SG l-3, and SG 1-4 nozzle-to-pipe welds.

1400 PDT, PG&E conservatively evaluated flawthat d the American the linear acceptance the SG l-1, SG 1-2, and SG l-3 piping may be bey criteria. h On September 24, 1992, at 1511 PDT, PG&E made h a four- our, non-emergency report to the NRC in accordance wit 10 CFR 50.72(b)(2)(i). d on the a metallurgical analysis performeflaws to be On October 15, 1992, criteria.

transition piping removed from the SGs deter B.

Background:

f ement (IE) the NRC Office of Inspection and En orcS tem On October 16, 1979, issued IE Bulletin 79-13, Revision 2, " Cracking Piping."

The Bulletin Westinghouse and Combustion Engineering power ll PWR licenseesplants.

sections i

recommended that during the next refueling outa of main feedwater (MFW) piping to the SG nozzles.to During the Unit 1 first (IRI) refueling outage, in response h Bulletin completed:

79-13, the following examinations i l and in auxiliary feedwater (AFW)(BA) toAtthe MFW the time, connection, piping and e criteria.

and v inspection of pipe supports and snubbers. t welds were found to be acceptable under ASME Code accep anc During the Unit 2 first (IR2) refueling outage, in response h AFW Bulletin completed:

79-13, the following examinations ts and and i to the MFW connection, and visual inspection of p snubbers.

under ASME Code acceptance criteria.

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L0l5l0l0l0l2l7l5k192 $0 -h 0l0h 2l23 l 'd, in March 1991, NUREG/CR-5285 in Feedwater System Piping,", u closed B ll"Closecut of IE etin 79-13 for Units Crackin On March 19, 1992, cracking was di 1 and 2.g q

at TVA's Sequoyah nuclear power plantscovered on the SG FW nozzle welds a crackingat TVA's son July 2, 19 potentially occur at Diabloequcyah Canyon Po nuclea,r power plant, couldpr similar initiated nozzle to conduct welds NDE nonniton wer each Plant the (DCPP).Unit SG IOCPP adU has wereFW piping during 1R5. 2 SG.

Plans nozzle welds and associated radiograph recordsIn September 1992, as a result of Bulletin 79-13 it was wasdetermined incompleteradiography s

that the Unit 1 SG perform,eFWan i nozzle SG welds.

nozzle-to-pipe welds were r.

{ pipe The pipe-to-pipe welds o the adjacent tre techniquesAlso, (10/86 recent used for adiographed reviews the Unit 1 suggest instead that thof the- o-SG nozzle t e radiography full co)m,pand IR2 (5/87) SG nozzle examinations thickness,liance with Bulletin 79-13 requirements sensitivity, and density values may not have been in, IR1 i '

after with hot functional all requirements testing on Unit .

The2 radiographs performed, su the removed piping sec.

Subsequent1/85) were in full compliance inves(tigative radiogr these segmennottions havewith detected cracksthe small thermal suggest f that radiaphs taken on C.

significance.ts; therefore, PG&E believes that this iteatigue Event

Description:

m has no safety >

In September 1992, during IR5 '

Additional examinations verified thindications the areas adjacent to the welds near; in e area of the first-off weld. '

Also in September 1992, during IR5 e presence o four Unit 1 SG thermal sleeves has conclud

, erosion operation. ed that the SG therma (AB)(St.V). / corrosion was found on all significance.Therefore, l sleeves PG&E are acceptable believes that this nued forevent contiAn h en as no safety the piping adThe initial engineering evaluati 45* elbows to alltofour PG&E decided replace SG thereho FW i repairs. noz lSubseque n

k z es during 1R5.r zontal piping from the

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e . LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 198539 DOCKET NUMBER (2) LER NUM6(R l'6) PAGE (3)

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DIABLO CANYON UNIT 1 Ol5l0l0l0l2]7l5 92- -

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I. Plant Conditions i

l Unit I was in Mode 6 (refueling) at 0 percent power.

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j II. Descriotion of Event A. Summary:

The Unit 1 fifth (IR5) refueling outage ultrasonic testing (UT) of the Unit I steam generator (SG)(AB) feedwater (FW) nozzles (AB)(NZL) and piping (SJ)(PSP) identified circumferential linear indications on l

piping in the main feedwater system (MFWS)(SJ) near SG 1-1, SG 1-2, SG 1-3, and SG 1-4 nozzle-to-pipe welds. . On September 24, 1992, at 1 1400 PDT, PG&E conservatively evaluated that the linear indications on j the SG 1-1, SG 1-2, and SG 1-3 piping may be beyond the American e Society of Mechanical Engineers (ASME) Code Section XI flaw acceptance criteria.

l On September 24, 1992, at 1511 PDT, PG&E made a four-hour, ,

non-emergency report to the NRC.in accordance with 10 CFR 50.72(b)(2)(1).

On October 15, 1992, a metallurgical analysis performed on the transition piping removed from the SGs determined the flaws to be acceptable under the ASME Code Section XI flaw acceptance-criteria.

t B.

Background:

[ On October 16, 1979, the NRC Office of Inspection and Enforcement (IE) issued IE-Bulletin 79-13, Revision 2, Cracking in Feedwater, System k

Piping."Bulletin 79-13 identified FW nozzle-to-pipe welds in 14 Westinghouse and Combustion Engineering power plants. The Bulletin

recommended that during the next refueling outage, all PWR licensees

! should perform nondestructive examinations (NDE) on various sections of main feedwater (MFW) piping to the SG nozzles. 1 i During the Unit 1 first (1RI) refueling outage, in response to

{ Bulletin 79-13, the following examinations and inspections were 4 completed: radiography, UT of one pipe diameter downstream of the 1

); auxiliary feedwater (AFW)(BA) to the MFW connection, and visual l inspection of pipe supports and snubbers. At the time, piping and welds were found to be acceptable under ASME Code acceptance criteria.

During the Unit 2 first (1R2) refueling outage, in response to i Bulletin 79-13, the following examinations and inspections were I completed: radiography, UT of one pipe diameter downstream of the AFW i to the MFW connection, and visual inspection of pipe supports and snubbers. At the time, piping and welds were found to be acceptable j under ASME Code acceptance criteria.

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i In March 1991, NUREG/CR-5285, "Closecut of'IE Bulletin 79-13:

in Feedwater System Piping," closed Bulletin 79-13 for Units 1 and 2. Cracking On March 19, 1992, cracking was discovered on the SG FW nozzle' welds. 1 at TVA's Sequoyah nuclear power plant.

On July 2, 1992, PG&E determined that cracking, previously detected on-the SG FW nozzle welds at TVA's Sequcyah nuclear power plant, could potentially occur at Diablo Canyon Power Plant (DCPP). DCPP has similar nozzle welds on each Unit I and Unit 2 SG. Plans were ' l' initiated piping during to IRS.

conduct NDE on the SG FW nozzle welds and associat In September 1992, as a result of an investigative review of past radiograph records, it was determined that the Unit 1 SG FW nozzle Bulletin. 79-13 was incomplete. ' The pipe-to-pipe w SG nozzle-to-pipe pipe welds. welds were radiographed .instead of the SG nozzle-to-Also, recent reviews suggest that the radiography techniques used for the Unit 1 post hot functional testing (9/79), IRli (10/86 , and IR2 (5/87) SG nozzle examinations may not have been ' in full co)mpliance with Bulletin 79-13 requirements, thickness, sensitivity, and density values. The radiographs performed su with all requirements.after hot functional testing on Unit 2 (1/85) were. -

. Subsequent investigative radiographs taken on

the removed piping sections with cracks suggest that radiography wou i not have detected the small thermal fatigue crackin these segments significance. ; therefore, PG&E believes that this'g experienced on . ite C. Event

Description:

1 d

indications in the MFW piping in the' area of the f

• I Additional the areas adjacent examinations verified the presence of linear' indications in to the welds. i Also in September 1992, during 1RS, erosion / corrosion was found on four Unit 1 SG thermal sleeves An has concluded that the SG therma (AB)(SLV).l sleeves are. engineering e operation. acceptable for continued significance.Therefore, PG&E believes that this event has no safety the piping adjacent to the SG FW nozzles may re _

Subsequently, 45 PG&E decided to replace the horizontal piping from the elbows to all four SG FW nozzles during IRS. '

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-; O l0 6 On September indications may not be acceptableeunder acceptance criteria. aw MFW piping ASME Se On September 24 non-emergency re, port to the NRC in accordance with1992 10 CFR 50.72(b)(2)(i).

On October 15, 1992, a metallurgical analysis of the li nearpiping determi indications in the removed section of HFW piping was acceptable under the ASME Code criteria. Section ned shat aw acceptance the XI fl D.

Inoperable Structures, Components, or Systems that Cont ib Event:

r uted to the None.

E.

Dates and Approximate Times for Major: Occurrences

1. September 24, 1992, at 1400 PDT:

Event / Discovery date. MFW piping was discovered beyond the code limit acceptance

2. September criteria.

24, 1992, at 1511 PDT:

A four-hour, non-emergency report was made to the NRC in accordance with

3. October 4, 1992: 10 CFR 50.72(b)(2)(i).

MFW piping replacement '.::s

4. started.

October 15, 1992:

A metallurgical analysis concluded the piping was

5. acceptable.

October 21, 1992:

MFW piping replacement was F. completed.

Other Systems or Secondary Functions Affected:

None.

G.

Method of Discovery:

On September 24, 1992, at 1400 PDT, based on UT conservatively concluded that the MFW piping examinations, indicati PG&E acceptable under ASME Section XI flaw eria. acceptance ons may not be crit

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H. Operators Actions:

' None.

I.

Safety System Responses:

None.

III. Cause of the Event ,

A. Immediate Cause:

Linear indications were found in MFW piping adjacent to the SG nozzles.

1 B. Root Cause:

Based on a metallurgical analysis, PG&E has determined the prel Additional i root cause to be thermal stratification induced fatigue.If additional evaluations are being performed on the welds.informatio 7 submitted.

C. Contributory Cause:

Corrosion fatigue.

IV. Analysis of the Event J The MFWS is designed a r. ide FW to the SG to maintain the proper heatIt also l i

p balance between thi m irr / and secondary systems.w available or in respon ths SG whenever MF6 AFW flow.

A metallurgical analysis was performed to evaluate the effect of the lin indications in the MFW piping and it was determined that the piping was acceptable under the ASME Code Section XI flaw acceptance criteria.

Consequently, the linear indications on the MFW piping near the did not adversely affect the health and safety of the public.

V. _ Corrective Actions A. Immediate Corrective Actions:

1. The horizontal piping from the 45 elbows to all four SG FW nozzles was replaced during 1RS. i 1066S/85K

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DOCKET NUNSER (2) tra NUM8(R f6)

FACILITY NAME (1)

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2. During 2R5, NDE will be performed on the MFW piping adjacent to and including the SG FW pipe-to-nozzle welds and corrective actions will be taken as appropriate.

B. Corrective Actions to Prevent Recurrence:

1. PG&E has conservatively decided to perform NDE during each refueling outage _on the MFw piping adjacent to and including the SG FW pipe-to-nozzle welds.

2. PG&E is reviewing several modifications that may inhibit crack development in the pipe-to-nozzle weld areas and inhibit erosion / corrosion in the thermal sleeves. If a modification is determined to be appropriate, a supplemental LER will be submitted.

VI. Additional Information A. Failed Components:

None.

B. Previous LERs on Similar Problems:

None.

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