05000446/LER-2002-002
| Docket Numbers | |
| Event date: | |
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| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4462002002R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
Any operation or condition prohibited by the plant's Technical Specifications.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
On June 19, 2002, Comanche Peak Steam Electric Station (CPSES) Unit 2 was in Mode 1, Power Operation, operating at 99.5 percent power.
C. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE
INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO
THE EVENT
There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND
APPROXIMATE TIMES
CPSES Technical Specification Surveillance Requirement (SR) 3.3.2.5 for Table 3.3.2-1, Item 5b, requires the performance of a Channel Operational Test (COT) every 92 days on the Steam Generator High-High Water Level instrumentation in order to provide protection against excessive feedwater flow. A COT is performed on each required channel to ensure that the entire channel (EIES:(CHA)) will perform its intended safety function.
On June 19, 2002, at 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, while investigating a previous circuit card failure, Engineering department personnel (utility, non-licensed) discovered that the COT procedure for a Steam Generator Narrow Range Level failed to verify the Steam Generator High-High level actuation function on the NPL card, a required trip function in the Technical Specifications. The absence of this verification in the procedure constituted a missed surveillance (SR 3.3.2.5.5b).
This condition applies to twelve Unit 2 Steam Generator level COT procedures (three procedures on each of four Steam Generators). The condition does not apply to Unit 1 due to differences in design and testing methodology. The Unit 1 design utilizes lead-lag circuit cards versus NPL timer (EIIS:(TMR)) cards to affect the necessary time delay.
Facility Name (I) COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2 LER Number (6) I-1 Year I Sequential Number 02 � 002 Docket Page(3) Revision Number The NPL card involved is a dual input, dual logic, single timer, dual output card, which means that the timer on the card is shared between two circuits. These two circuits are the Steam Generator High-High Level Turbine Trip/Feedwater Isolation signal circuit and the Steam Generator Low-Low Level Reactor Trip/Auxiliary Feedwater Pump Start signal circuit.
The circuit configuration and required test methodology for the Westinghouse 7300 Series Process Instrument Loops was changed as a result of a modification which was installed in Unit 2 in April 1996 during the unit's second refueling outage. These changes resulted in the setpoints being sensed at a different point in the circuit. Prior to implementation of the modification, setpoints were sensed downstream of the NPL card thereby verifying continuity for both the High-High and Low-Low portions of the card. Subsequent to the modification, the High-High setpoint was sensed upstream of the NPL card. Only the Low-Low setpoint was sensed both upstream and downstream of the NPL card.
To incorporate the 1996 modification, the affected COT procedures were revised to inject a test signal through the Steam Generator Low-Low Level circuitry portion of the NPL card in order to verify timer functionality. By virtue of its design, injecting a test signal through either the Steam Generator High-High Level or the Steam Generator Low-Low Level circuitry of the NPL card would verify the functionality of the timer. Therefore, injecting a test signal through both the High-High and Low-Low circuitry of the card was viewed as redundant by the author of the procedure revisions, and this approach was not taken.
Although it is true that the timer function of the card was adequately verified by injecting the test signal through only the Low-Low circuitry portion of the card, this test methodology failed to verify continuity through both logic circuits of the NPL card itself and therefore failed to satisfy the strict definition for Channel Operational Test in the CPSES Technical Specifications.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE,
OR PROCEDURAL OR PERSONNEL ERROR
During investigation into a failed circuit card in the Engineered Safety Feature Actuation System, Engineering personnel (utility, non-licensed) discovered that a component on the card was not covered by an approved surveillance procedure. This constituted a missed Technical Specification surveillance.
II. COMPONENT OR SYSTEM FAILURES
A. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT
Not applicable — No component or system failures were identified during this event.
B. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE
Not applicable — No component or system failures were identified during this event.
C. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE
OF COMPONENTS WITH MULTIPLE FUNCTIONS
Not applicable — No component or system failures were identified during this event.
D. FAILED COMPONENT INFORMATION
Not applicable — No component or system failures were identified during this event.
III. ANALYSIS OF THE EVENT
A. SAFETY SYSTEM RESPONSES THAT OCCURRED
Not applicable - no safety system responses occurred as a result of this event.
B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
Not applicable - no safety system train was deemed inoperable.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT
The Steam Generator High-High level function (including the NPL card) was verified via Response Time Testing on October 3, 2000 for six of the twelve channels, and on April 3, 2002 for the remaining six channels.
Facility Name (I) COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2 Docket LER Number (6) Page(3) Year IfAEi Sequential Number Revsion Number During the time period that these surveillances were not fully performed, a plant transient or event that would have required these channels to operate did not occur. Also, all of the affected channels were subsequently tested, and this testing demonstrated that the channels would have performed their intended safety function, if required. There were no safety system functional failures associated with this event.
Based on the above, it is concluded that the event of June 19, 2002 did not adversely impact the safe operation of CPSES or the health and safety of public.
IV. CAUSE OF THE EVENT
TXU Energy believes that the cause of the event was less than adequate attention to detail on the part of both the preparer and technical reviewer of the Unit 2 Steam Generator Level Channel Operational Test procedure revisions that incorporated the 1996 Westinghouse 7300 System Design Modification.
The procedure revisions did not specifically verify the continuity of PROM logic cards in the Westinghouse 7300 Series Process Instrumentation System. This verification of continuity is necessary to satisfy the strict definition for "Channel Operational Test" in the CPSES Technical Specifications, and this resulted in the failure to satisfy Technical Specification Channel Operational Test surveillance requirements.
V. CORRECTIVE ACTIONS
The twelve affected surveillance testing procedures have been revised to incorporate verification of High-High level actuation function through the NPL card and all of the affected Technical Specification surveillance tests were successfully completed per the revised procedures.
Westinghouse 7300 Series Process Instrument Loop drawings were reviewed to determine whether there are any other instances where logic cards are located downstream of a bistable. The review identified no instances where circuitry installed downstream of a bistable was not adequately tested. A Lessons Learned regarding this event has been issued to procedure writers and test personnel involved with testing of safety-related logic circuits in order to reinforce the importance of verifying card continuity in order to satisfy Technical Specification requirements.
VI. PREVIOUS SIMILAR EVENTS
There have been other previous events related to missed surveillances. However, the causes for those events were sufficiently different from this event such that the corrective actions would not have prevented this event.