ML082530363

Vermont Yankee July 2008 Evidentiary Hearing - Applicant Exhibit E4-21-VY, INPO Report OE-20127 (Calvert Cliffs)

ML082530363
Person / Time
Site:	Calvert Cliffs, Vermont Yankee
Issue date:	07/21/2008
From:	Entergy Nuclear Operations, Vermont Yankee
To:	NRC/SECY/RAS
SECY RAS
References
06-849-03-LR, 50-271-LR, Entergy-Applicant-E4-21-VY, RAS M-336
Download: ML082530363 (2)

Text

SUBJECT:

0E20127 - Required Shutdown of Calvert Cliffs Unit 1 to Repair a Steam Leak on the Steam Vent Header Piping of 11 Moisture Separator Reheater Drain Tank

SUBJECT:

Required Shutdown of Calvert Cliffs Unit 1 to Repair a Steam Leak on the Steam Vent Header Piping of 11 Moisture Separator Reheater Drain Tank ABSTRACT:

On February 28, 2005 Calvert Cliffs shutdown Unit 1 to repair a steam leak on the 6-inch GB-20-1005 steam vent header of 11. Moisture Separator Reheater Drain Tank. The cause of the steam leak was a small through wall leak at the end of an elbow. This elbow had a backing ring installed during original construction. This caused vortexing which led to-very localized flow accelerated corrosion (FAC) through the top of the elbow at the weld. The backing ring was found split at the top of the elbow where flow velocity was likely highest. This was an original plant construction weld. The affected section of piping was replaced and the Unit returned to power.

REASON FOR MESSAGE:

This OE is being issued to inform the industry of the unscheduled shutdown of Unit 1 due to a steam leak.

EVENT DATE:

02/26/2005 UNIT NAME:

Calvert Cliffs Unit 1 NSSS/A-E:

CE/Bechtel TURBINE MANUFACTURER:

GE/Westinghouse U.S. NULWG E R ML-AI*%r RY N3,01 mg, I]

MAINTENANCE RULE APPLICABILITY:

Yes Inothe at No  ; .'/ ,

bA) _ .I c-Docket*No. -- -- _ Off1dhl Exhibit No.E4 -Z1- V*'

COMPONENT INFORMATION (AS APPLICABLE):

OFFERED by' V tervenor MANUFACTURER: Other Piping IDNT onNRC Staff MODEL NUMBER: on4)0witness/Panei-~J~

6 inch Schedule 40 pipe and elbows Acfionak,(M REETD rDW PART NUMBER:

N/A DESCRIPTION:

On February 26, 2005, a site technician identified steam emanating from under the lagging on the 11 Moisture Separator Reheater (MSR) Drain Tank vent line.

An engineering team was immediately assembled to evaluate the issue and determine corrective actions. The investigation determined that the steam leak was on a 6-inch Steam Vent Header Schedule 40 piping that connects the 11 Moisture Separator Drain Tank to the Hot Reheat Header.

Degradation of this piping was a known condition. The piping was scheduled for replacement in the upcoming Unit 1 Refueling Outage scheduled for the spring of 2006.

Access to the turbine building was restricted. The Unit was brought off-line to replace all affected piping.

All repairs were completed and the Unit returned to full power.

CAUSES:

Investigation determined the cause of the steam leak was a small through wall leak at the end of an elbow. The elbow had a backing ring installed during original construction. -The backing ring had a gap on the outside of the ring and the inner wall of the elbow. This allowed FAC to erode the elbow-to-pipe weld.

CORRECTIVE ACTIONS:

Corrective Actions included:

The Control Room implemented the appropriate Emergency Response Plan for a steam leak (compensatory measure).All access to the turbine building was restricted until the Unit was .removed from service for repairs (compensatory measure) .All affected piping was replaced prior to returning Unit 1 to service.All associated piping-on 12 Moisture Separator Reheater Drain Tank was inspected and required no repairs.

SAFETY SIGNIFICANCE:

There were no personnel or public safety issues as a result of this event. Unit 1 was shutdown and all repairs were successfully completed.

INFORMATION CONTACT:

Mark Hunter 410.495.4003 Mark. T. Hunter@constellation.com

REFERENCE:

IRE-003-553 DOCKETED USNRC August 12, 2008 (11:00am)

OFFICE OF SECRETARY RULEMAKINGS AND ADJUDICATIONS STAFF