05000397/LER-2004-008
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3972004008R00 - NRC Website | |
I. Event Description
On November 22, 2004 Columbia Generating Station (Columbia) was in Mode 1 with the reactor operating at approximately 100 percent of rated thermal power. At approximately 17:30 PST, the Reactor Core Isolation Cooling System (RCIC) steam supply line outboard containment isolation valve (RCIC-V-63) closed. This caused RCIC to become inoperable.
The closure of RCIC-V-63 occurred while performing procedure ICP-RCIC-Q901, "RCIC Isolation on RCIC Steam Flow High Div 2 - CFT/CC" (Channel Functional Test/Channel Calibration). Procedure ICP- RCIC-Q901 provides instructions for the channel functional test and channel calibration of the RCIC steam line flow high instrument channel associated with RCIC-DPIS-7B.
Two technicians were setting up to perform a channel functional test/channel calibration of differential pressure indicating switch RCIC-DPIS-7B. RCIC-DPIS-7B senses steam flow in the steam supply piping to the RCIC turbine. The switch contacts on RCIC-DPIS-7B close on high steam flow conditions (normally open contacts) to make up RCIC-V-63 isolation logic, close RCIC-V-63, and activate an annunciator in the control room.
The procedure calls for isolating RCIC-DPIS-7B, connecting water pots to its test valves, and connecting a pressure source and test gauge to the high pressure side water pot. Then the procedure calls for connecting a digital multi-meter (DMM) across terminals AA1 and AA2. The purpose of the DMM is to indicate when the high steam relay flow contacts close during the test. Once the pressure source is connected to the high pressure side water pot, and the DMM is connected, the procedure calls for opening the breaker to the RCIC-V-63 motor operator so the valve will not close when RCIC-DPIS-7B is actuated during the test.
The DMM that was connected across terminals AA1 and AA2 had been taken to the instrument rack with its test leads stacked. That is, the banana jack leads were connected to each other (stacked) at the negative terminal of the DMM. This is typical of how DMM's are transported by the technicians. The technicians connected the leads to terminals AA1 and AA2 without un-stacking the leads at the DMM. This effectively jumpered out the contact, actuated RCIC-DPIS-7B, closed RCIC-V-63 and caused an alarm in the control room.
Control room operators declared RCIC inoperable, entered the appropriate Technical Specification Required Actions, and directed that technicians back out of the procedure.
II. Cause of Event
The immediate cause of this event was a personnel error by one of the I&C technicians performing the procedure. The technician who connected the DMM across contacts AA1 and AA2 of RCIC-DPIS-7B failed to use proper self-checking techniques to ensure that the DMM was properly configured before connecting the DMM across the contacts. This effectively jumpered out the contact the technicians were attempting to monitor during performance of the procedure and resulted in an actuation of RCIC-DPIS-7B and isolation of RCIC-V-63.
A root cause analysis was performed regarding this event. The root cause analysis determined the following:
- There was an over-reliance on self-checking and peer-checking during performance of the procedure.
- The procedure did not contain precautionary information associated with performing steps in the specified sequence or the potential for a single human error to cause a safety system isolation.
- There was no direct field supervision of the work.
- There was no pre-work review to identify the potential risk or consequences.
III. Safety Significance
The RCIC system is designed to operate either manually or automatically following reactor pressure vessel (RPV) isolation accompanied by a loss of coolant flow from the feedwater system to provide adequate core cooling and control of RPV water level. Under these conditions, the High Pressure Core Spray (HPCS) and RCIC systems perform similar functions. After the loss of RCIC, control room operators entered Technical Specification (TS) Action 3.5.3.A, which requires that with the RCIC system inoperable, the HPCS system must be verified operable immediately and the RCIC system must be restored to an operable status within 14 days. Since HPCS was verified to be operable and the total duration of this event was approximately two hours and three minutes, the TS requirements were satisfied. Therefore, this event posed no threat to the health and safety of the public or plant personnel.
This event is reportable under 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." There were no structures, systems or components that were inoperable at the start of the event that contributed to the event.
IV. Immediate Corrective Actions Control room operators entered and complied with TS Action Statement 3.5.3.A, by verifying that HPCS was operable. Operators then proceeded to take action to protect HPCS. Control room operators directed the I&C technicians to back-out of the procedure and restore all components to their normal line-up. After all components were restored to their normal line-up, RCIC was placed in a normal line-up, with RCIC-V 63 open, and declared operable two hours and three minutes after the isolation occurred.
V. Further Corrective Actions A stand-down briefing was conducted on the day after the event to explain the event to Electrical and I&C craft and supervisors.
S.
- Reduce the consequences of a single human error by changing the status of the system or equipment such that it cannot be inadvertently actuated or isolated while hooking up test equipment, or;
- Add appropriate cautions which will enhance worker awareness regarding risk, consequence, and mitigating actions.
Formal expectations for functional testing of test equipment and self-checking and peer-checking of test equipment set-up prior to connecting to in-service systems will be added to management and job observation forms.
Specific expectations for depth and quality of supervisory field oversight for medium and high risk activities will be added to existing expectations.
Plant Procedure Manual (PPM) 1.3.76, Integrated Risk Management, is a relatively new procedure at Columbia. This procedure establishes administrative controls for the oversight of risk significant activities in Modes 1, 2, and 3. PPM 1.3.76 has been in a pilot period and utilized only for a select number of work activities. This procedure was not used for the performance of ICP-RCIC-Q901 on November 22, 2004.
This procedure is currently in the process of being fully implemented.
VI. Previous Similar Events
A search of the Columbia Problem Evaluation Request (PER) database and LER database was conducted.
The search covered the period from 1999 to the date of this event and identified one similar event involving an RCIC-V-63 isolation due to personnel error. The event is documented in LER 397-2003-008. A Condition Report was initiated (2-04-06501) to document that the corrective actions associated with LER 397-2003-008 were not effective in preventing the recurrence of this similar event. The corrective actions listed above were developed to minimize recurrence of similar events in the future.
VII. EIIS Information Text Reference� System�Component Reactor Core Isolation Cooling System� BN High Pressure Core Spray System� BG RCIC-DPIS-7B� BN� PDIS RCIC-V-63 BN ISV 26158 R2