05000397/LER-2004-006
| Columbia Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 3972004006R00 - NRC Website | |
Summary On August 17, 2004, with a plant startup in progress and with the plant in Mode 1 at approximately 20% power, a licensed control room operator improperly filled a feedwater (SJ) heater (HX) with condensate following maintenance. This improper filling evolution tripped the only running reactor feedwater pump (P) initiating a loss of feedwater transient. The reactor was scrammed manually prior to level reaching the automatic trip set point and water level was stabilized using the Reactor Core Isolation Cooling (RCIC) system and the recovered reactor feedwater pump.
Description of Event
On August 16, 2004, the plant was in Mode 2 with startup in progress. At 2020, the plant transitioned to Mode 1. During a walk down in the heater bay, a relief valve was found to be continuously lifting and a work request was generated to replace the valve. On August 17 at 0101, the Production Senior Reactor Operator (PSRO) authorized the clearance order to be hung in support of replacing the relief valve (RV). The scope of the tagout was to remove the associated feedwater heaters from service, open the condensate bypass valve, and isolate and drain the associated heaters.
On August 17, 2004 at approximately 0430, maintenance completed the relief valve replacement and the craft supervisor released the clearance order tags. The PSRO approved removal of the clearance order tags and informed the Control Room Supervisor (CRS) that replacement of the relief valve was complete. At 0440, a briefing with the Equipment Operator (without the Control Room Reactor Operator) was conducted to clear the tag. At the brief, the Equipment Operator was informed the heaters require a slow fill. The Equipment Operator completed the field portion of the tagout to close vents and drains and returned disconnects to the closed position. He then reported to the control room and transferred the clearance order lift document to a licensed Reactor Operator to complete the tag removal and restore the system.
The Reactor Operator did not adequately read the clearance order restoration instructions and did not retain them in his possession while proceeding. This Reactor Operator obtained a peer check from a second Reactor Operator who did not request the written clearance order instructions. These Reactor Operators incorrectly concluded that the instructions provided in Annunciator Response Procedure (ARP) applied to the current heater condition. This ARP presumes the feedwater heater is filled but isolated following a high level trip and provides direction to fully open the condensate valve to the heaters.
On August 17, 2004 at 0528, the Reactor Operator depressed the "OPEN" pushbutton for the valve to the feedwater heater, thereby fully opening the valve. Condensate flow was preferentially diverted from the feedwater pump suction to fill the heaters, which resulted in the low suction pressure trip on the operating feedwater pump. Control room operators manually scrammed the reactor due to the trip of the in-service feedwater pump.
Post scram information indicated the feedwater pump trip was the result of a low suction pressure condition, which was caused by the rapid refill of the first stage feedwater heater.
Cause of Event
Failure of the Reactor Operator to strictly adhere to written instructions resulted in uncontrolled filling of the feedwater heater and a momentary drop in condensate system pressure. The momentary drop in condensate system pressure directly resulted in a trip of the running feedwater pump on low suction pressure. The Reactor Operator's neglect in reading the clearance order restoration instructions represents task overconfidence.
Following Columbia Generating Station Outage R-16, a number of human performance errors occurred within the operations department and an expectation was initiated to have a supervisor or manager attend each clearance order brief. By late 2003, clearance order performance had improved. In early 2004, the expectation was relaxed and management oversight reduced significantly. Past operating crew performance improvements diminished with infrequent supervisor observations and the absence of expectation reinforcement.
The Reactor Operator involved in this event was on a performance improvement plan when the error occurred. This existing performance improvement plan did not adequately address behavior based performance shortfalls.
At the time of the event, redundant supervisory oversight barriers were diminished due to plant startup activities distracting focus from the heater restoration activities. The PSRO failed to include key control room personnel in the pre-evolution brief conducted prior to clearance order removal and system restoration. Though a more detailed plan for restoring the feedwater heaters existed, it was not included in the task for this evolution.
Safety Significance
This event posed no threat to the health and safety of the public or plant personnel. All safety equipment was available during this transient and performed as expected. The improper restoration of the feedwater heat exchangers directly resulted in an automatic trip of the in service feedwater pump due to low suction pressure causing a loss of feedwater flow to the reactor. The loss of feedwater flow resulted in a lowering RPV water level. The reactor was manually scrammed and the RPV water level was restored to normal using both the RCIC system and the recovered feedwater pump. The plant was stabilized in Mode 3 without further event.
Immediate Corrective Actions
Three immediate corrective actions were implemented in response to this event. The first two actions were implemented and communicated by initiation of a Night Order. The Night Order requires all Operations department briefs to be conducted by a Senior Reactor Operator (SRO) and all work order plant impacts to be independently verified by another SRO. The third immediate action was the administration of appropriate disqualification and discipline to four individuals involved.
Operations will conduct a review and resulting expectations will be incorporated into individual performance expectations.
The Night Order discussed under Immediate Corrective Actions will be reviewed to determine if required actions should be proceduralized and, if so, will be implemented accordingly.
Existing open individual performance improvement plans will be reviewed to ensure the aspects are behavior based versus results based. The Performance Improvement Program will also be revised to monitor improvement based on behaviors more than results.
The special instructions for recovering feedwater heaters following maintenance when the plant is on-line, which were developed during previous performance of this task, will be proceduralized.
A corrective action effectiveness assessment will be performed to ensure corrective actions are adequate to prevent recurrence.
Previous Similar Events
No previous similar events were identified in which a condition reportable pursuant to 10 CFR 10 CFR 50.73(a)(2)(iv)(A) existed due to a human performance error in filling feedwater heaters due to the operator failing to follow written instructions.
The conclusion from the search is that, although human performance errors have been documented, there were no events that would have driven Energy Northwest to question the ability of Columbia Generating Station Operators to read and follow written instructions.
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