05000311/LER-2007-002

LER-2007-002, RReactor Trip Due to a Breach in the Condensate System

Docket Number
Event date:	05-24-2007
Report date:	07-23-2007
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3112007002R00 - NRC Website

PLANT AND SYSTEM IDENTIFICATION

Westinghouse — Pressurized Water Reactor (PWR/4) Condensate Demineralizer System / sight glass {SF/LG}* * Energy Industry Identification System {EllS} codes and component function identifier codes appear as {SS/CCC}

IDENTIFICATION OF OCCURRENCE

Event Date: May 24, 2007 Discovery Date: May 24, 2007

CONDITIONS PRIOR TO OCCURRENCE

Salem Unit 2 was in Operational Mode 1 at 100% reactor power.

No structures, systems or components were inoperable at the time of the discovery that contributed to the event.

DESCRIPTION OF OCCURRENCE

At 1450 on May 23, 2007, the 24 Demineralizer Vessel (DMV) was placed in standby to regenerate the resin, a routine evolution to maintain system chemistry within design parameters. The vessel was removed from service and the resin bed transfers were completed at 2230.

Following the resin refill, a purge rinse was commenced on the DMV to verify proper effluent chemistry prior to placing the vessel in-service. Normal condensate flow is used as the influent and the effluent is returned to the condenser hotwells until all effluent chemistry parameters are within specifications. This evolution typically takes approximately six to eight hours.

Approximately three hours into the evolution, at 0230 on May 24, 2007, the 24 DMV upper sight glass window {SF/LG} experienced a catastrophic failure at steady state condensate operating pressure and temperature. A feedwater trouble warning light was received, followed by a low Steam Generator Feedwater Pump (SGFP) suction pressure alarm in the control room. The 21 SGFP tripped as a result of the low suction pressure, resulting in the 22 SG level decreasing to the low-low level set point (14%) and generating a reactor trip.

This event is reportable in accordance with 10CFR50.73 (a)(2)(iv)(A), "any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section.

�NRC FORM 366 (6-2004) PRINTED ON RECYCLED PAPER

PREVIOUS OCCURRENCES

A review of LERs at Salem Station identified no similar events reported to the NRC within the last three years caused by the rupture of a condensate DMV sight glass or related to the control of vendor document information.

CAUSE OF OCCURRENCE

The cause of the low SG level was a trip of 21 SGFP due to significant loss of condensate inventory and pressure. This was caused by the failure of the 24 DMV upper sight glass.

The root cause for the 24 DMV upper sight glass failure is attributed to having inadequate guidance in vendor documents pertaining to the installation and maintenance of these sight glass windows. Failure to incorporate the vendor's recommendations resulted in the re-use of the sight glass windows following gasket replacement and the application of excessive torque during the installation process. These errors resulted in localized stress concentrations that over time compromised the ability of the sight glass window to withstand the systems' normal operating pressure.

SAFETY CONSEQUENCES AND IMPLICATIONS

There were no actual safety consequences associated with this event; sufficient core cooling was always maintained. The plant remained within safety limits throughout the event. The Auxiliary Feedwater pumps started as expected. The safety systems responded to the low SG level as designed. There were no structures, systems, or components that were inoperable at the time of the event that contributed to this condition.

The spilled condensate contained low levels of tritium, which flowed out of the Condensate Polishing Building into the switchyard and subsequently into the yard drains. The maximum tritium result sampled of the contained water was below the level required to report. The condensate became mixed with rainwater from a prior storm and was accounted for via normal means of discharge.

A review of this event determined that a Safety System Functional Failure (SSFF) as defined in NEI 99-02, Regulatory Assessment Performance Indicator Guidelines, did not occur. There was no condition that alone could have prevented the fulfillment of a safety function of a system needed to remove residual heat

CORRECTIVE ACTIONS

1. Completed a prompt investigation of event and subsequent root cause evaluation.

2. All DMV sight glass windows were replaced using the latest vendor guidance. The Unit 2 sight glasses were replaced prior to placing the DMV's in-service. The Unit 1 DMV sight glasses were replaced as the DMV's were removed from service during routine operation.

3. The applicable vendor manual will be updated to include the appropriate installation instructions and maintenance procedures for the sight glasses.

COMMITMENTS

No commitments are made in this LER.