05000250/LER-2013-003, Regarding Manual Reactor Trip Due to Increasing Reactor Coolant Pump Seal Leakage

Regarding Manual Reactor Trip Due to Increasing Reactor Coolant Pump Seal Leakage

ML13128A311
Person / Time
Site:	Turkey Point
Issue date:	04/19/2013
From:	Kiley M Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2013-138 LER 13-003-00
Download: ML13128A311 (5)

LER-2013-003, Regarding Manual Reactor Trip Due to Increasing Reactor Coolant Pump Seal Leakage

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2502013003R00 - NRC Website

text

FPL.

L-2013-138 10 CFR § 50.73 U. S. Nuclear Regulatory Commission APR 19 2013 Attn: Document Control Desk Washington, D. C. 20555-0001 Re:

Turkey Point Unit 3 Docket No. 50-250 Reportable Event: 2013-003-00 Manual Reactor Trip Due to Increasing Reactor Coolant Pump Seal Leakage The attached Licensee Event Report 05000250/2013-003-00 is submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A) due to valid actuations of the Reactor Protection and Auxiliary Feedwater Systems.

If there are any questions, please call Mr. Robert J. Tomonto at 305-246-7327.

Very truly yours, Michael Kiley Vice President Turkey Point Nuclear Plant Attachment cc:

Regional Administrator, USNRC, Region II Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant Florida Power & Light Company 9760 SW 344 St., Florida City, FL 33035

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 110-2010)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1PAGE Turkey Point Unit 3 05000250 1 of4

4. TITLE Manual Reactor Trip Due to Increasing Reactor Coolant Pump Seal Leakage

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED JFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL RV MONTH DAY YEAR I

UBR REVFACILITY NAME DOCKET NUMERý 18 2013 2013-003 -00 4

19 2013

9. OPERATING MODE 11I. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) oI 20.2201(b)

El 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

E] 50.73(a)(2)(vii)

Mode 1 0l 20.2201(d)

El 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

Ej 50.73(a)(2)(viii)(A)

[3 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

[] 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A) 0] 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL El 20,2203(a)(2)(ii)

El 50.36(c)(I)(ii)(A)

Z 50.73(a)(2)(iv)(A)

E] 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

[] 50.36(c)(2) 0l 50.73(a)(2)(v)(A)

El 73.71(a)(4)

El 20.2203(a)(2)(iv)

E] 50.46(a)(3)(ii)0 El 50.73(a)(2)(v)(B)

El 73.71(a)(5) 72 El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A) 0l 50.73(a)(2)(v)(C)

El OTHER El 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

El 50,73(a)(2)(v)(D)

Specify in Abstract below or in groove. The shaft shoulder for the runner was also found damaged. The runner anti-rotation pin slot in the sleeve and the corresponding anti-rotation pin were also found to be worn. The four locating pins for the runner were found to be slightly flatted on the bottom from potential contact with the runneri. The corresponding groove in the runner showed wear from contact with the locating pins. No degraded seal components were discovered with the No. 2 and 3 seals although some missing pieces of the No. I runner o-ring where found therein.

A review of the evidence indicates that the No. 1 runner o-ring was pinched and/or rolled on the runner during installation. The inherent design of the seal precludes verification of proper runner o-ring orientation after installation.

The investigation also determined the existence of insufficient mating surfaces, from previous shaft shoulder stoning, between the No. I seal runner landing and the RCP shaft shoulder. Insufficient mating surfaces caused a condition where an acceptable amount of runner nutation (rotate in a wobbling motion) could cause damage to the RCP shaft shoulder. This damage then exacerbated the existing seal runner nutation which led to eventual failure of both the DDCS and runner o-rings. Damage to either the DDCS or runner o-rings would cause excessive No. I seal leak-off flow rate.

ANALYSIS OF SAFETY SIGNIFICANCE Erratic 3A RCP No. 1 seal leak-off flow rates were noted during the evening of February 17, 2013. When No. 1 seal leak-off flow exceeded 5.5 gpm early on February 18, 2013, Operations personnel began a fast load reduction in accordance with plant procedures. When No. 1 seal leak-off flow reached 6.0 gpm, operators manually tripped the reactor and stopped the 3A RCP in accordance with plant procedures, and isolated seal leak-off flow. These actions precluded further 3A RCP No. I seal degradation. Recovery from the reactor trip was as expected. As a result, the safety significance of this event is very low.

CORRECTIVE ACTIONS

Corrective actions are documented in AR 1849104 and include the following:

1. The 3A RCP seal was replaced with a new seal.

2. Seal leak-off performance was reviewed for the other five RCPs. Only the Unit 4 4B RCP No. I seal showed similar characteristics. It has been repaired (Unit 4 was shut down for a refueling/modification outage at the time) utilizing the lessons learned from the 3A RCP seal investigation.

3. Revise procedure 0-CMM-041.06, Reactor Coolant Pump Coupling and Seal Removal, Inspection, and Installation, to provide additional guidance for machining a RCP shaft shoulder.

4. The seal vendor will perform a technical review of procedure 0-CMM-041.06 to identify any additional needed guidance for seal reassembly that should be incorporated.

FAILED COMPONENTS IDENTIFIED: Areva Model 93 Reactor Coolant Pump Seal

PREVIOUS SIMILAR EVENTS

RCP shaft shoulder anomalies and a pinched No. 1 seal runner o-ring were identified as causes for RCP high No. I seal leak-off a few times over the years. The most recent events delayed start-up or resulted in controlled plant shutdown that did not require submission of Licensee Event Reports (LER).

A previous seal failure on the Unit 4 4A RCP (May 5, 2011) was caused by a pinched runner o-ring during installation that led to a failure and high leak-off after only 9 days of operation during startup from a refueling outage. Because the o-ring was found pinched at the upper end of the No. 1 runner o-ring groove, it was concluded that it was caught and moved out of position while lowering onto the shaft. There are several shaft landings where it could make contact and move outside of the groove. Corrective actions included hold points and inspections during installation. However, the installation of the No. I runner on the last several inches of the RCP shaft becomes a "blind" installation due to the tolerances between the outer shaft diameter and inner runner diameter clearances. The rolling or twisting of the o-ring in the event descrjbed in this LER is more indicative of a lack of lubrication at a certain section of the o-ring. As such, most of the o-ring will slide along the shaft sleeve where it lands or mates. The piece of o-ring that is not lubricated will subsequently roll rather than slide with the rest of the o-ring. Therefore, the prior corrective action would not have prevented recurrence.