ML18066A226

LER 98-009-00:on 980531,small Pinhole Leak Found on One of Welds,During Leak Test Following Replacement of Pcs Sample Isolation Valves.Caused by Welder Error.Leaking Welds Repaired

ML18066A226
Person / Time
Site:	Palisades
Issue date:	06/30/1998
From:	Flenner P CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18066A225	List: ML18066A224 ML18066A226
References
LER-98-009, LER-98-9, NUDOCS 9807080115
Download: ML18066A226 (3)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4/95) EXPIRES 4/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY wml THIS MANDATORY N'ORMATION ca..L.ECTKlN REQl.eST:

50.0 IRS. REPORTED LESSONS l.EARNEDARE LICJ";NSEE EVENT REPORT (LER1 INCORPORATED INTO THE LICENSING PROCESS ANO FED BACK TO INDUSTRY.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION ANO RECOROS MANAGEMENT BRANCH F33). U.S. NUCLEAR REGULATORY (See reverse for required number of digits/characters for each block) COMMISSION.

WASHINGTON.

OC 2055$-0001.

ANO TO THE PAPERWORK REDUCTION PROJECT (31504104.

OFFICE OF MANAGEMENT N¥:J BUDGET. WASHINGTON.

OC 20503 FACILITY NAME (1) CONSUMERS ENERGY COMPANY DOCKET NUMBER PAGE PALISADES NUCLEAR PLANT 05000255 1of3 TITLE "LEAKS IN ASME CLASS 1 PRIMARY COOLANT SYSTEM SAMPLE LINE WELDS" EVENT DATE LER NUMBER REPORT DATE OTHER FACILITIES INVOLVED I SEQUENTIAL REVISION MONTH DAY YEAR FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NUMBER 05000 05 31 98 98 009 00 06 30 98 FACILITY NAME DOCKET NUMBER 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check one or more) MODE N 20.2201(b) 20.2203(a)(2)(v)

50. 73(a)(2)(i)

50. 73(a)(2)(iii)

I POWER I I 20.2203(a)(1) 20.2203(a)(3)(i)

50. 73(a)(2)(ii)

50. 73(a)(2)(x)

LEVEL 0% 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)

Voluntary Report 20.2203(al(2)(iv) 50.36(C)(2)

50. 73(a)(2)(vii)

• LICENSEE CONTACT FOR THIS LER . NAME TELEPHONE NUMBER (Include Area Code) Philip D. Flenner, Sr. Licensing Engineer (616) 764-2544 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TOEPIX TOEPIX A AB ISV 1¥25 N SUPPLEMENTAL REPORT EXPECTED MONTH DAY YEAR I YES x I NO EXPECTED If yes, COMPLETE EXPECTED COMPLETION DATE SUBMISSION DATE (15) ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On May 31, 1998, during the leak test following the replacement of the Primary Coolant System (PCS) (AB) Sample Isolation Valves (ISV), a small pinhole leak was found on one of the welds. During the leak test following the repair of this weld, a second pinhole leak was found on another weld made during valve replacement.

These welds were located in piping connected to the PCS but are normally isolated with closed control valves. The welds are also part of the containment boundary.

The inservice leak test was performed with the PCS in hot shutdown.

• The small leaks in the new welds were the result of residual moisture in the line during welding.

This resulted in pinholes in the single pass socket welds that were not detected using the PT examination method. Through-wall leakage is not allowed in ASME Class 1 system piping and would normally be reportable as rendering the system in a condition outside the design basis of the plant. However, in this particular instance, the leakage was identified during initial inservice leak testing which was performed in accordance with ASME Code requirements as a part of post maintenance testing. Leakage identified in this manner is not considered a Code violation.

Therefore, since no Code violation occurred and the magnitude of the leakage was not sufficient to impact either PCS leak rate or containment building leakage Technical Specifications requirements, this occurrence is being reported as a voluntary Licensee Event Report. Th.ere were no significant safety implications as a result of this occurrence due to the size of the line, the tvoe of discontinuitv, and the amount of the leakaQe. PDR PDR s

• NRC FORM 366a U.S. NUCLEAR REGULATORY COMMISSION 4/95 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) DOCKET12\

LER NUMBER 6l g CONSUMERS ENERGY COMPANY YEAR I SEQUENTIAL REVISION NUMBER NUMBER PALISADES NU9LEAR PLANT 05000255 98 009 00 3 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) EVENT DESCRIPTION On May 31, 1998, during the leak test following the replacement of the Primary Coolant System (PCS) Sample Isolation Valves, a small pinhole leak (characterized as one drop every two minutes) was found on one of the welds. During the leak test following the repair of this weld, a second pinhole leak (characterized as <:one drop every five minutes) was found on another weld made during the replacement process. As a result, the code requirement that the system pass the leak test with no leakage noted was not met until further repairs were made. These welds were located in piping connected to the PCS but are normally isolated with closed control valves. The welds are also part of the containment boundary.

The inservice leak test was performed in accordance with the Code with the PCS in hot shutdown.

Since the PCS was in the hot shutdown mode of operation, Technical Specifications (TS) action statement 4.5.2C(1) was conservatively entered during the repairs to the welds. This action statement requires repair within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or placing the plant in hot shutdown within the following six hours and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Subsequent evaluation has shown that entry into TS 4.5.2C(1) was not required.

PCS structural integrity was not compromised and the leak rate was well within TS limits. Containment integrity, as defined by the TS, was also maintained.

The leaking welds were isolated from the PCS during the repair by closing manual isolation valves and separating mechanical joints within containment.

Through-wall leakage is not allowed in ASME Class 1 system piping and would normally be reportable as rendering the system in a condition outside the design basis of the plant. However, in this particular instance, the leakage was identified during initial inservice leak testing which was performed in accordance with ASME Code requirements a part of post maintenance testing. Leakage identified in this manner is not considered a Code violation.

Therefore, since no Code violation occurred and the magnitude of the leakage was not sufficient to impact either PCS leak rate or containment building leakage Technical Specifications requirements, this occurrence is being reported as a voluntary Licensee Event Report. ANALYSIS OF EVENT Two small leaks were found in PCS and containment boundary welds during an inservice leak test following valve replacement.

The valves, CV-1910 and CV-1911, are socket welded Primary Coolant System Sample Isolation Valves which were replaced during the 1998 refueling outage. Valve CV-1910 is an ASME Class 1 valve that provided both a PCS and a containment isolation function.

The replacement activity required welding and was completed using a gas tungsten arc welding (GTAW) process. The welds were examined using the liquid dye penetrant (PT) method and no rejectable indications were found. Pressure testing was then performed fo check for NRC FORM 366a U.S. NUCLEAR REGULATORY COMMISSION 4/95 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

' FACILITY NAME 11\ DOCKET12l LER NUMBER 6l PAGE CONSUMERS ENERGY COMPANY YEAR I SEQUENTIAL REVISION NUMBER NUMBER 30F3 PALISADES, NUCLEAR PLANT 05000255 98 009 00 .. TEXT (If more space 1s required, use additional copies of NRC Form 366A) (17) leakage in the valves and new welds. The leak test was accomplished with the Primary Coolant System at normal operating pressure and temperature.

A small pinhole leak was found on one of the field welds. The leak rate was quantified as one drop every two minutes. After the repair of the leaking weld, another leak test was performed, at which time a second weld was discovered to be leaking, also as a result of a small pinhole leak. The leak rate was quantified as less than one drop every five minutes. This weld was repaired and subsequently passed the PT examination and the leak test. The small leaks in the new welds were the result of residual moisture in the line during welding. This resulted in pinholes in the single pass socket welds that were not detected using the PT examination method. The welder recognized that the line was moist and attempted to dry the line by heating with a torch. This was not ultimately successful.

The weld repair was subsequently completed after additional actions were taken to dry the line. SAFETY SIGNIFICANCE There were no significant safety implications as a result of this occurrence due to the size of the line, the type of discontinuity, and the amount of the leakage .. While the potential for an uncontrolled release of radioactive material exists whenever a containment penetration has leakage, any release through such small defects would be well within 10 CFR Part 100 criteria.

• The pinhole leaks in the welds would not have affected the weld integrity from a strength standpoint.

CAUSE OF EVENT The root cause of this event was the welder's mistaken belief that residual moisture had been removed from the weld area. CORRECTIVE ACTIONS The leaking Welds were repaired under acceptable conditions and passed both the PT examinations and the inservice leak test. The lessons learned from this event will be reviewed with selected Mechanical Maintenance, Planning and Engineering personnel.