ML18153A251

LER 98-006-00:on 980324,unisolable Through Wall Leak of RCP Thermowell Was Noted.Cause of Leak Is Unknown.Rtd Will Be Replaced

ML18153A251
Person / Time
Site:	Surry
Issue date:	04/22/1998
From:	Christian D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18153A248	List: ML18153A247 ML18153A251
References
LER-98-006, LER-98-6, NUDOCS 9804270423
Download: ML18153A251 (3)

Text

e

. NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104

-95) EXPIRES 4130/98 ESTIMATED BURDEN PER RESPONSE TO CDU'LY WITH lHS MMOATORY INFORMATION COLLECTION REQUEST: 50.0 ~S.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO 1lE LICENSEE EVENT REPORT (LER) LICENSING PROCESS /WD FED BACK TO INDUSTRY. FORWARD CO!.M:NTS REGARDING BLRDEN ESTIW.TE TO 1lE INFORMATION /WD RECOROS P.WW,EMENT BRANCH (T-6 F33),

U.S. NUCLEAR REGll.ATORY CCM.ISSION. WASHNGTON. DC (See rewrse for required number of digits/characters for each block) 2055S-0001, /WD 10 1lE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT /WD BI.DGET, WASHNGTON. DC 20503.

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

SURRY POWER STATION, Unit 1 05000 - 280 1 OF 3 TITLE (4)

Unisolable Through Wall Leak of RCP Thermowell EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENllAL REVISION FA.CILITY NAME DOCUMENT NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER 05000-FACILITY NAME DOCUMENT NUMBER 03 24 98 1998 -- 006 -- 00 04 22 98 05000-OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) (11)

MODE (9) NA 20.2201(b) 20.2203(a)(2)(v) X 50. 73(a)(2)(i) 50. 73(a)(2)(11iii)

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

LEVEL (10) 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) OTHER

,20.2203(a)(2)(iii) 50.36(c)(1) 50. 73(a)(2)(v) Specify in Abstract below 20.2203(a)(2)(iv) 50.36(c)(2) 50. 73(a)(2)(11ii) or in NRC Form 366A E

LICENSEE CONTACT FOR THIS LER 12)

I TELEPHONE NUMBER (Include Area Code)

(757) 365-2000 D. A. Christian, Site Vice President COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TONPRDS TONPRDS B AB TW W120 No NTAL CTED (14 EXPECTED MONTH DAY YEAR YES NO SUBMISSION X

DATE (lf~s. complete EXPECTED SUBMISSION DATE).

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

On March 24, 1998, with Unit 1 at Cold Shutdown, the B Reactor Coolant Pump (RCP) Motor was being removed for maintenance. During the removal process, it was noted that there was a boric acid build-up on the head of the RCP lower radial bearing Resistance Temperature Detector (RTD) connection. The RTD cap was removed and it was noted that the thermowell was filled with water. This RTD is dry mounted in a thermowell. The thermowell forms part of the Reactor Coolant System (RCS) pressure boundary. A sample of the water revealed that the water was from the RCS indicating a through wall leak of the thermowell. Technical Specification 3.1.C.4 prohibits a non-isolable fault in a RCS component body, pipe wall, vessel wall, or pipe weld. Prior to Unit operation the defect was repaired in accordance with

' appropriate codes and standards.

This event is reportable pursuant to 10CFR50.73(a)(2)(i)(B) .for conditions prohibited by Technical Specifications.

---

9804270423 980422 PDR ADOCK 05000280 S .PDR

NRC FORM 366A e U.S. NUCLEAR REGULATORY COMMISSION

• (4-95)

LICENSEE EVENT REPORT (LER)

. TEXT CONTINUATION FACILITY NAME (1) DOCKET PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Su Power Station, Unit 1 05000 - 280 1998 - 006 - 00 2 OF3 TEXT_ (If more space is required, use additional copies of NRC Form 366A) (17)

1.0 DESCRIPTION

OF THE EVENT On March 24, 1998, with Unit 1 at Cold Shutdown, the B Reactor Coolant Pump (RCP)

Motor was being removed for maintenance. During the removal process, it was noted that there was a boric acid build up on the head of the RCP [EIIS-AB-P] lower radial bearing Resistance Temperature Detector (RTD) [EIIS-AB-TI] connection. The RTD cap was removed and it was noted that the thermowell was filled with water. This RTD is dry mounted in a thermowell. The thermowell [EIIS-AB-TW] forms part of the Reactor Coolant System (RCS) pressure boundary. A sample of the water revealed thatthe water was from the RCS indicating a through wall leak of the thermowell. Technical Specification 3.1.C.4 prohibits a non-isolable fault in a RCS component body, pipe wall, vessel wall, or pipe weld. Prior to Unit operation the defect was repaired in accordance with appropriate codes and standards.

This event is reportable pursuant to 10CFR50.73(a)(2)(i)(B) for conditions prohibited by Technical Specifications.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS The visual evidence of the leakage indicates that the defect appears to have existed for some time. Reactor Coolant leakage is quantified daily including unidentified leakage.

• The unidentified leakage had been relatively consistent at values less than the unidentified leakage limits specified in TS 3.1.C.2. Catastrophic failure of the thermowell is unlikely, but if it were *to occur, the resultant loss of RCS inventory would be bounded by analysis. Therefore, the health and safety of the public were not affected.

3.0 CAUSE The thermowell has not been removed for detailed examination, therefore the exact

.cause of the leak is unknown. A review of Westinghouse Technical Bulletin ESBU-TB-96-01-RO, dated June 17,1996, documents three instances in which water has been observed leaking from the electrical portion of the pump bearing RTD. The thermowells were fabricated by machining a long rod and center boring from both ends to meet in the middle. Westinghouse has determined that in some cases the two bores did not meet exactly and left a thin spot. NOE examination of leaking thermowells at other plants has confirmed failures at this intersection. It is theorized based on the Westinghouse Technical Bulletin that we have the same condition on the Unit 1 B RCP.

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 PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Sur Power Station, Unit 1 05000 - 280 1998 -006- 00 3 OF 3 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) 4.0 IMMEDIATE CORRECTIVE ACTION(S)

The RTD (1-CH-TE-1128) was removed and the thermowell was isolated with a seal welded plug in accordance with an Engineering Transmittal (ET 98-0058). Appropriate non-destructive examination (penetrant test) was satisfactorily performed. This modification did remove the RTD function, however, degradation_ of the lower radial bearing due to loss of cooling or seal injection can be monitored via alternate indications.

Unit 1 A and C RCPs were inspected for leakage. No evidence of leakage was observed. Unit 2 unidentified leakage was and continues to be monitored for any increase. No increases have been noted.

5.0 ADDITIONAL CORRECTIVE ACTIONS To recover the original function of the RTD, it is necessary to install an RTD with system pressure capabilities. Westinghouse has designed a replacement RTD with high pressure capability specifically for this situation. The new RTD will be installed for the B RCP at the next refueling outage for Unit 1.

The Engineering Department will develop a programmatic inspection of RCP thermowell caps for those thermowells that do not have the new RTD with system pressure capabilities.

6.0 ACTIONS TO PREVENT RECURRENCE During future scheduled RCP Motor change outs (normally one per Refueling Outage) the original design RTD will be replaced with the high-pressure RTD.

7.0 SIMILAR EVENTS No previous LERs have been submitted on this issue.

8.0 ADDITIONAL INFORMATION Unit 2 was operating at 100% and was not affected by this event.

NRC FORM 366A (4-95)