05000397/LER-2003-005

LER-2003-005,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3972003005R00 - NRC Website

Event Description

On June 16, 2003, Columbia Generating Station (Columbia) was in Mode 4 (cold shutdown) with the reactor coolant temperature at approximately 112 degrees Fahrenheit. At approximately 1330 PDT, an isolation of Residual Heat Removal (RHR) Shutdown Cooling (SDC) common suction header occurred when the outboard primary containment isolation valve, RHR-V-8 closed. The RHR SDC isolation occurred while performing surveillance procedure TSP-CONT/ISOL-B501, 'Containment Isolation LSFT," (Logic System Functional Test] section 7.6, Manual Initiation. Step 7.6.42 of this surveillance procedure required depressing the manual Nuclear Steam Supply Shutoff System (NSSSS) initiation logic B pushbutton (MS-RMS-S25B). Depressing this pushbutton causes an isolation signal to 16 NSSSS isolation valves, including RHR-V-8.

At the time of the event, RHR SDC subsystem A was operating in the shutdown cooling mode and RHR SDC subsystem B was available for SDC service, but not in operation. Reactor Recirculation Pump 1B (RRC-P-IB) was running to support reactor core circulation and was unaffected by the RHR SDC isolation. The condensate system was available as an alternate means of decay heat removal by injection into the RPV with heat rejection to the main condenser.

The SDC isolation was caused by closure of RHR-V-8, the outboard primary containment isolation valve in the common suction line for both RHR SDC subsystems. Closure of RHR-V-8 subsequently tripped RHR SDC pump 2A (REIR-P-2A). Operators entered abnormal condition procedure ABN- RHR-SDC-LASS, "Loss of Shutdown Cooling," and the appropriate Technical Specification (TS) Required Action (TS 3.4.10.A). Technical Specification Required Action 3.4.10.A.1 requires verification that an alternate source of decay heat removal is available for each inoperable RHR SDC subsystem within one hour.

All isolation signals were reset and RHR SDC was restored approximately 12 minutes after RHR-V-8 closed. During the time that RHR SDC was out of service, reactor coolant temperature increased from approximately 112 to 113 degrees Fahrenheit.

Cause of Event

The primary cause of this event was an inadequate procedure. Surveillance procedure TSP- CONT/ISOL-B501, section 7.6, should have contained a description of the expected valve isolations that would occur when the manual pushbutton for NSSSS initiation logic B was depressed. Other sections of this procedure do contain descriptions of expected isolations, while section 7.6 does not.

A contributing cause was inadequate preparation by the operators performing the test. Even though the surveillance procedure was weak in describing the impact on the plant when performing section 7.6, a more thorough review to understand the impact of the test being performed may have prevented this event.

26158 R2 r

Safety Significance

This event posed no threat to the health and safety of the public or plant personnel. The RHR SDC system was restored to service in approximately 12 minutes with an increase in reactor coolant temperature of approximately one degree Fahrenheit. A reactor recirculation pump was in operation throughout the event (RRC-P-1B) to provide reactor coolant circulation. Alternate methods for removal of residual heat were available from condensate injection with heat removal via the main condenser and through abnormal condition procedure, ABN-RHR-SDC-LOSS, "Loss of Shutdown Cooling," which provides instructions to restore (manually) RHR shutdown cooling.

This event is reportable in accordance with 10 CFR 50.73 (a)(2)(vXB).

Immediate Corrective Actions

Control Room Operators entered abnormal condition procedure ABN-RHR-SDC-LOSS and reviewed TSP-CONT/ISOL-B501 to determine what step was being performed at the time the SDC isolation occurred. In addition, the Shift Manager verified that the operator performing the surveillance test had depressed the correct pushbutton. The NSSSS isolation signal was reset, and RHR SDC subsystem A was placed in service.

The applicable drawings were reviewed to confirm that the actuations/isolations that occurred should have been expected.

Further Corrective Actions Surveillance procedure TSP-CONT/ISOL-B501 has been modified to specify the isolations that will occur when performing section 7.6. All valves that Isolate are listed prior to the steps requiring the manual depressing of an NSSSS initiation logic pushbutton.

The pre-job briefing sheet for surveillance procedure TSP-CONT/ISOL-B501, section 7.6, has been modified to reflect that an NSSSS isolation will occur when section 7.6 is performed.

Previous Similar Events

A review of the Problem Evaluation Request database from 1997 to present found the following similar events:

containment isolation valve RHR-V-9. This event occurred during a planned maintenance activity and was caused by maintenance personnel performing work on the wrong relay when replacing a relay wire lug.

2615882 4-04:7 An isolation of shutdown cooling occured on June 8, 2001 when the RHR suction outboard isolation valve closed during planned maintenance. However, this event was determined not to be reportable under 10 CFR 50.72 or 73 reporting requirements.

ElIS Information Text Reference � System � Component RHR SDC Isolation Valve, RHR-V-8 � BO � ISV RHR SDC Pump RHR-P-2A � BO Reactor Recirculation Pump (RRC-P-1B) � AD Nuclear Steam Supply Shutoff System � BD 26158 R2