05000397/LER-2007-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No 0500 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3972007001R00 - NRC Website | |
Plant Conditions
At the time of discovery, Columbia Generating Station was operating in mode 1 at 100% power. There were no other structures, systems, or components inoperable at the time that contributed to the condition.
Event Description
On March 21st, 2007, at approximately 0214, it was discovered that a pressure sensing instrument [PS] had been isolated and out of service during the time it was required to be operable by plant Technical Specifications. The instrument provides a low pressure Emergency Core Cooling System (ECCS) [BO] pump running permissive signal for initiation of Division I of the Automatic Depressurization System (ADS) and is specified in Function 4.e of Table 3.3.5.1-1 in Technical Specifications Limiting Condition for Operation (LCO) 3.3.5.1.
The instrument was discovered isolated during surveillance testing and maintenance records indicate it had potentially been isolated for as long as 32 days. This is longer than the 8-day Completion Time allowed for Required Action G.2 of Technical Specifications LCO 3.3.5.1 to restore operable status.
Immediate Corrective Action The pressure instrument was promptly restored to service upon discovery of the condition.
Correct pressure instrument valve configuration was verified for all channels in both divisions of ADS.
Cause
Several instances associated with surveillance testing were identified which presented opportunities for the instrument to be isolated by plant technicians or operators. However, no specific evidence or interview information could exclude or identify the specific instance when the inadvertent isolation occurred. Because of this, further cause analysis to identify the specific human error and its causes is not possible.
The cause of the required pressure sensing instrument being inadvertently isolated and out of service is considered to be related to human performance. A discussion pursuant to 10 CFR 50.73(b)(2)(ii)(J) to support understanding of human performance factors to the extent they apply is provided.
Procedural deficiencies associated with the mispositioned valve included an inservice test procedure that had human factor deficiencies because it did not provide specific valve manipulation instructions or specify a location for connecting and disconnecting a test gauge used for measuring pump discharge pressure. Additionally, a surveillance procedure was found to have human factor deficiencies in that the noun identifier in the procedure for the instrument isolation valve was different 26158 R3 A minor human-system interface deficiency was noted in that the mis-positioned isolation valve had two labels. One label displayed the valve number and one displayed the noun name of the valve.
This creates an additional step when applying the touch-read-read error prevention tool.
Circumstantial aspects of this event are that the personnel involved are non-licensed equipment operators and instrument technicians and there was no indication of any time or situational pressures involved with the testing activities.
Assessment of Safety Consequences
There were no safety consequences associated with this event.
During the entire time the pressure instrument was inadvertently isolated and out of service, redundant instruments were operable to provide initiation capability of both ADS subsystems.
Further Corrective Actions Actions will be taken to correct the human factor deficiencies in the procedures and the human-system interface deficiency associated with the valve labeling.
Previous Similar Events
There have been no previous similar events in which an instrument providing an input to the ECCS system actuation logic had been inadvertently valved out of service for a period of time that exceeded Technical Specifications requirements.
EIIS Information (Denoted as (XX1) Emergency Core Cooling System [BO] Pressure Switch [PS] 26158 R3