05000249/LER-2007-001

LER-2007-001, Unit 3 High Pressure Coolant Injection System Declared Inoperable

Docket Number
Event date:	03-02-2007
Report date:	05-01-2007
Reporting criterion:	10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
2492007001R00 - NRC Website

Dresden Nuclear Power Station (DNPS) Unit 3 is a General Electric Company Boiling Water Reactor with a licensed maximum power level of 2957 megawatts thermal. The Energy Industry Identification System codes used in the text are identified as [XX].

A. Plant Conditions Prior to Event:

Unit: 03 Event Date: 3-2-2007 Reactor Mode: 1 Mode Name: Power Operation Power Level: 100 percent Reactor Coolant System Pressure: 1000 psig

B. Description of Event:

On March 2, 2007, at 1912 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.27516e-4 months <br /> (CST), with Unit 3 at approximately 100 percent power, DNPS control room personnel were notified of a very small through wall steam leak on the Unit 3 High Pressure Coolant Injection (HPCI) [BG] System Inlet Drain Pot drain piping [DRN] downstream of valve 3-2301-55. To repair the leaking location, the piping was isolated which resulted in the isolation of the Unit 3 HPCI System. The Unit 3 HPCI System was declared inoperable and Technical Specification (TS) 3.5.1, "ECCS Operating," was entered. Non Destructive Examination of the HPCI System piping identified a pinhole leak 5/8 inches downstream of the valve 3-2301-55 weld toe. The piping containing the pinhole leak was replaced.

An ENS call was made on March 2, 2007, at 2133 hours0.0247 days <br />0.593 hours <br />0.00353 weeks <br />8.116065e-4 months <br /> (CST) for the above-described event. The assigned ENS event number was 43209.

The Unit 3 HPCI System was declared operable on March 3, 2007, at 0403 hours0.00466 days <br />0.112 hours <br />6.66336e-4 weeks <br />1.533415e-4 months <br /> (CST).

This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D), "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident." HPCI is a single train system and is credited in mitigating the consequences of an accident.

C. Cause of Event:

High Pressure Coolant Injection System Inlet Drain Pot drain piping that was susceptible to Flow Accelerated Corrosion (FAC).

DNPS had previously generated five Work Orders (WO) to schedule and perform the replacement of carbon steel piping susceptible to FAC with A-335 P-11 chrome-moly piping. Four of the five WO's were performed after 2002 and contained sufficient closeout documentation to clearly identify the piping that was replaced and the material used. The remaining WO was performed in 1997 and the closeout documentation did not clearly identify the work performed. The scope of this WO included the HPCI System carbon steel piping associated with this event. A review of the performance of the 1997 WO identified that numerous revisions and work scope changes were made, resulting in WO closure documentation that did not clearly document that not all of the original work scope was completed. As a result, several sections of Unit 2 and 3 HPCI System piping susceptible to FAC that were not replaced were incorrectly removed from the FAC Inspection Program.

D. Safety Analysis:

The safety significance of the event is minimal. TS 3.5.1 allows Unit 3 to remain at power for 14 days with an inoperable HPCI if the Isolation Condenser System (IC) is operable. Unit 3 was in compliance with TS 3.5.1 during this event as the IC was operable and HPCI was inoperable for approximately 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.

E. Corrective Actions:

Unit 3 HPCI System Inlet Drain Pot drain piping with the pinhole leak was replaced.

Unit 2 and 3 HPCI System carbon steel piping susceptible to FAC has been identified, evaluated for acceptance of the degraded condition until replacement and scheduled for replacement in future outages.

The Work Control process has been significantly enhanced since 1997 to ensure sufficient closeout documentation including the use of a computerized process (PASSPORT) for entering closeout documentation, implementation of procedure MA-AA-716-011, 'Work Execution and Closeout," and the use of First Line Supervisors to enter work documentation notes.

F. Previous Occurrences:

A review of DNPS Licensee Event Reports (LERs) for the last three years did not identified any LERs associated with piping that was found with a through wall leak and susceptible to FAC.