ML18106A693

LER 98-003-00:on 980122,inappropriate Plugging of Tubes R9C60 & R10C60 in Salem Unit 2 Sg,Was Performed.Caused by Failure of Qualification,Verification & Validation Process. Tubes Reviewed to Verify No Others Inappropriately Plugged

ML18106A693
Person / Time
Site:	Salem
Issue date:	06/29/1998
From:	Knieriem B Public Service Enterprise Group
To:
Shared Package
ML18106A692	List: ML18106A691 ML18106A693
References
LER-98-003-02, LER-98-3-2, NUDOCS 9807140090
Download: ML18106A693 (4)

Text

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NRC FORM 366 U.S. NUCLEAR LATORY COMMISSION ROVED BY OMB NO. 3150-0104 (4-95) EXPIRES 04/30/98 LICENSEE EVENT REPORT (LER) ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD (See reverse for required number of COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND digits/characters for each block) RECORDS MANAGEMENT BRANCH (T*6 F33J, U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 205 5-0001, AND TO THE PAPERWORK REDUCTION PROJECT ~150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, C 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE(3)

SALEM UNIT 2 05000311 1 OF 4 TITLE (4)

Inappropriate Plugging Of Tubes R9C60 And RlOC60 In The Salem Unit 2, 24 Steam Generator

• EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL I REVISION MONTH DAY YEAR NUMBER NUMBER I

FACILITY NAME DOCKET NUMBER 01 22 98 98 - 003 - 00 06 29 98 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) (11)

MODE (9) 1 20.2201(b) 20.2203(a)(2)(v) 50. 73(a)(2)(i)(B) 50.73(a)(2)(viii)

POWER 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a)(2)(ii) 50. 73(a)(2)(x)

LEVEL (10) 100 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50. 73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv) x OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50. 73(a)(2)(v) Spec~ in Abstract below or in RC Form 366A I I 20.2203(a)(2)(iv) 50.36(c)(2)

LICENSEE CONTACT FOR THIS LER (12) 50.73(a)(2)(vii)

NAME TELEPHONE NUMBER (Include Area Code)

Brooke Knieriem, Licensing Engineer ( 6 09) 339-1782 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TONPRDS TONPRDS

-

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION IYES (If yes, complete EXPECTED SUBMISSION DATE). x INO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

This voluntary LER reports an inappropriate repair that was performed on two tube plugs in the Salem Unit 2, 24 Steam Generator.

In 1996, an inappropriate repair of the cold leg sentinel plugs for tubes R9C60 and RlOC60 in the Salem Unit 2 24 Steam Generator was performed. I The repair installed a Plug-a-Plug (PAP) behind each of the existing sentinel plugs. This repair eliminated the ability of the sentinel plugs to allow a small amount of primary-to-secondary leakage as an indication of tube fatigue cracking.

The apparent cause of this occurrence was the incorrect identification of tubes R9C60 and RlOC60 as tubes requiring installation of PAPs. Continued operation of Unit 2 in this configuration was determined to be acceptable until the PAP behind the affected sentinel plugs can be removed during the next refueling outage.

9807140090 980629 PDR ADOCK 05000311 S PDR

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE(3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM UNIT 2 05000311 98 - 003 - 00 2 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor Steam Generator {SB/SG}

Westinghouse Model 51

• Energy Industry Identification System (EIIS) codes and component function identifier codes appear as {ss/cc}

CONDITIONS PRIOR TO OCCURRENCE At the time of identification, Salem Unit 2 was operating at 100% power.

(Mode 1) .

DESCRIPTION OF OCCURRENCE In 1988 tubes R9C60 and RlOC60 in the Salem Unit 2 24 Steam Generator (SG) were removed from service and stabilized using a Westinghouse stabilizer.

This action was taken in response to NRC Generic Letter 88-02 "Rapidly Propagating Fatigue Cracks In Steam Generator Tubes", and addressed steam generato~ tubes that were determined to be susceptible to circumferential failure above the SG top tube support plate due to secondary side flow induced vibration. The Westinghouse stabilizer is installed inside the tube and consists of a stainless steel cable, approximately 31 feet long, with swaged sleeves. The stabilizer functions to prevent a failed tube from contacting adjacent tubes. In addition to the installation of the stabilizers, each tube was removed from service by plugging the hot and cold leg ends with Inconel 600 (I-600) plugs.

In 1991 (after two cycles of operation), the hot leg plugs in tubes R9C60 and RlOC60 were repaired to address potential corrosion induced failure of the I-600 plugs. This repair was performed in response to NRC Bulletin 89-01, "Failure Of Westinghouse Steam Generator Mechanical Plugs".

At that time, the cold leg mechanical plug in each of these tubes was removed and an Inconel 690 (I-690) sentinel plug was installed to address Westinghouse SECL 91-439, "Salem Unit 2 Steam Generator Tube Stabilizers Safety Evaluation". SECL 91-439 determined that the installed stabilizer design was not qualified to dampen vibration in the tube U-bend area presenting the potential for tube fatigue in that area. The replacement sentinel plugs were designed with a leak-limiting orifice and were installed to provide indication of tube fatigue cracking. This cracking would be detectable via primary-to-secondary leakage monitoring. The source of the leakage would be determined, and the separation would be repaired at the next outage.

NRG FORM 366A (4-95)

'"

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR I SEQUENTIAL NUMBER I REVISION NUMBER SALEM UNIT 2 05000311 98 - 003 00 3 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE(Cont.)

In February of 1996, Frarnatorne Technologies (FTI) was authorized to repair all previously unrepaired or unreplaced I-600 plugs in the Unit 2 Stearn Generators. The repair method that was used was the Plug-A-Plug (PAP) method. This method installs a redundant I-690 plug behind the existing plug. The work scope for the plug repair was based upon a repair list provided to FTI by the Public Service Electric and Gas Stearn.Generator Group. This list was developed using information contained on the existing Plugging Tabulation Sh~ets. The Tube Plugging Tabulation Sheets contained two entries for tubes R9C60 and RlOC60 located in different locations on the sheet. The first entry for R9C60 and RlOC60 did not identify the tube plug type for the installed cold leg plugs. The second entry listed the sentinel plug information for the installed cold leg plugs. Only the first entry for R9C60 and RlOC60 was noted when preparing the plug repair list thus PSE&G personnel decided to repair those plugs by installing the PAP in the cold leg. This decision was thought to be conservative at the time. However, the change negated the leak limiting functionality of the sentinel plug as the PAP did not contain an orifice.

Therefore the sentinel plug's ability to provide indication of tube cracking was eliminated.

APPARENT CAUSE OF OCCURRENCE The apparent cause of this event was a failure of the Qualification, Verification, and Validation (QV&V) process. This process was not properly implemented when the Tube Plugging Tabulation Sheet for the 24 Stearn Generator was updated, resulting in duplicate entries for tubes R9C60 and RlOC60. In addition, a QV&V process for authorizing steam generator tube/tube plug repairs was not established. Both factors contributed to the inadvertent repair to the cold leg sentinel plugs installed in R9C60 and RlOC60.

PRIOR SIMILAR OCCURRENCES A review of LERs for Salem Units 1 and 2 issued in the last two years identified no LERs that reported similar occurrences.

SAFETY SIGNIFICANCE There are no safety consequences as a result of this event.

Because of the incorrect repair, tubes R9C60 and RlOC60 are plugged at both ends and are isolated from primary system pressure. In this condition the sentinel plugs are unable to carry out their leak limiting function. This condition does not significantly impact safety because if a circumferential crack were to develop in one of these tubes, the NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

• TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE(3)

YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SALEM UNIT 2 05000311 98 - 003 - 00 4 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

SAFETY SIGNIFICANCE(Cont.)

stabilizer would restrain the failed tube and prevent damage to adjacent tubes. In the event that the stabilizer did not function, and damage occurred to an adjacent tube, the resultant leakage from fretting through an in-service tube by the severed tube would be bounded by the existing tube rupture analysis.

CORRECTIVE ACTIONS

1. All Salem Unit 2 steam generator tubes containing sentinel plugs were reviewed to verify that no other tubes were inappropriately plugged.

This condition is limited to Unit 2, as there are no sentinel plugs installed in the Salem Unit 1 steam generators.

2. The inappropriate plugging of tubes R9C60 and RlOC60 was reviewed in accordance with 10CFRS0.59. This review determined that the loss of functionality of the sentinel plugs in did not constitute an unreviewed safety question and that operation could continue until functionality .

is restored during the next Unit 2 refueling outage.

3. The I-690 PAPS that were installed in tube R9C60 and R10C60 cold legs will be removed during the next Unit 2 refueling outage. (Problem Identification Report 980122241, Deficiency Report, Job Supervisor Notification 01)

4. The tubes adjacent to tubes R9C60 and R10C60 will be inspected for wear during the next Unit 2 refueling outage. (Problem Identification Report 980122241, Condition Resolution Corrective Action 01)

5. The 24 Steam Generator Tube Plugging Tabulation sheet was updated to correct duplicate tube entries for tubes R9C60 and R10C60.

6. A review process for authorizing steam generator tube plug repairs will be developed for future steam generator work. (Problem Identification Report 980122241, Condition Resolution Corrective Action 03)

• NRC FORM 366A (4-95)