05000250/LER-2013-001
| Turkey Point Unit 3 | |
| Event date: | 1-3-2013 |
|---|---|
| Report date: | 3-1-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2502013001R00 - NRC Website | |
DESCRIPTION OF THE EVENT
On January 2, 2013 at approximately 1913 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.278965e-4 months <br />, Pressurizer [AB, PZR] Level Channel [JC, CHA] I, L-3- 459, was declared inoperable as Instrumentation and Control (I&C) Maintenance personnel commenced a surveillance test using a Fluke Model 8846A multimeter [MTR]. Use of this meter was contrary to the requirements of the procedure that specifically required use of a Fluke Model 8842A multimeter. Using the incorrect meter resulted in erroneous as-found readings, which drove recalibration. At approximately 2022 on January 2, 2013, Channel I was determined to be inoperable and placed in the tripped condition using the bistable trip switches [JC, HS] to comply with Technical Specification (TS) 3.3.1, Table 3.3-1, Functional Unit 9, Action 13. Channel I was calibrated using a Fluke Model 8846A multimeter and when complete Channel I was declared operable at approximately 1436 on January 3, 2013 and the bistables were restored to the non-tripped condition.
At approximately 1648 on January 3, 2013, Pressurizer Level Channel II, L-3-460, was declared inoperable to perform a surveillance test also using a Fluke Model 8846A multimeter. Channel II was found outside acceptance criteria and placed in trip at approximately 1720 on January 3, 2013. After Channel II was found out of specification, a Fluke Model 8842A multimeter was used to double-check Channel II and it was found within acceptance criteria. After initial investigation revealed that the Model 8842A multimeter was the correct instrument for this calibration and the differences in instrument characteristics resulted in incorrect readings the first time, Channel II was declared operable at approximately 0915 on January 4, 2013 and the bistable trip switches were restored to the non-tripped condition.
At approximately 2025 on January 4, 2013, Pressurizer Level Channel I was declared inoperable for calibration using a Fluke Model 8842A multimeter. Channel I was found outside acceptance criteria at approximately 2054 and placed in trip. After calibration, Channel I was declared operable at approximately 2205 on January 4, 2013 and the bistable trip switches were restored to the non-tripped condition.
At approximately 0135 on January 5, 2013, I&C Maintenance personnel completed surveillance of Pressurizer Level Channel III, L-3-461, satisfactorily without adjustment using a Fluke Model 8842A multimeter as required by the procedure. This confirmed that this channel had remained operable since the last surveillance test in October 2012.
As a result, Channel I was inoperable and not tripped for a period of approximately 30.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> in noncompliance with TS 3.3.1, Table 3.3-1, Functional Unit 9, Action 13, which requires an inoperable channel to be in the tripped condition within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of inoperability. In addition, during this 30.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period, Channel II was tripped and so inoperable as a result of not meeting acceptance criteria for a period of approximately 16.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />. Turkey Point TS do not provide an action for two channels being inoperable concurrently. The previously unrecognized conditions resulted in exceeding the time limits specified in TS 3.3.1, Table 3.3-1, Action 13 and having two channels inoperable should have resulted in entry into TS 3.0.3 and that time limit was also exceeded. This report is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition which was prohibited by the plant's TS. In addition, the report is submitted in accordance with 10 CFR 50.73(a)(2)(vii) because the use of the incorrect meter resulted in a common cause concurrent inoperability of independent channels.
CAUSES OF THE EVENT
The direct cause of the event is procedural noncompliance by I&C Maintenance personnel involved with the surveillance tests. Although a new multimeter was made available to I&C Maintenance personnel for use, the meter was put into service without an evaluation for acceptability for use in all applications. The surveillance procedures specified the use of a Fluke 8842A with no approved equivalent. Because the new Fluke 8846A multimeters were made available for use, I&C Maintenance personnel assumed that the equivalency evaluation was performed and that the procedure change was editorial in nature.
The root cause is I&C Maintenance personnel do not consistently adhere to standards for procedure use and have not internalized procedure use and adherence as a core fundamental.
Two contributing causes were identified:
1. There is no formal process for placing new or replacement Measuring and Test Equipment (M&TE) in service. The M&TE procedure does not require an equivalency evaluation that includes differences such as input impedance or other operating characteristics, the determination of affected procedures, and the need for training prior to making new M&TE available for use.
2. A knowledge gap exists in the I&C Maintenance Department regarding use of test equipment and how it can impact plant equipment (i.e., impedance affects on the EAGLE 21 system).
BACKGROUND INFORMATION
Instrument Function The Reactor Protection System (RPS) [JC] and Engineered Safety Features Actuation System (ESFAS) [JE] have digital electronics modules called EAGLE 21. The EAGLE 21 components are a digital replacement for analog temperature and pressurizer level processing circuitry that receive inputs from Reactor Coolant System (RCS) sensors and digitally process the information. EAGLE 21 is designed to function as a qualified part of the RPS sending outputs to indicators, plant computers, annunciators, RPS, and ESFAS.
EAGLE 21 operation for Pressurizer High Water Level is through the input from the Pressurizer level transmitters LT-459, LT-460, and LT-461 [AC, PRZ, LT]. Loop power supplies [RJX] provide power to the level transmitters and route the signal to the EAGLE 21 system. All three level transmitters function in identical fashion.
The Pressurizer High Water Level Trip is provided as a backup to the Pressurizer High Pressure Trip. The coincidence of two out of the three Pressurizer Level signals trips the reactor [RCT]. This function is not relied upon as a primary trip function in the plant safety analysis. It may perform as a backup trip for any significant heat-up transient which results in a large specific volume change in the RCS.
The TS Trip Setpoint for the Pressurizer High Water Level Trip is 5 92% of instrument span. The Allowable Value is 5 92.2% of instrument span.
Multimeter Characteristics The Fluke Model 8846A multimeter operates in a default low impedance mode and will more accurately measure the parameter of interest, provided the circuit is not affected by the low input impedance. The low input impedance of the Fluke 8846A will cause improper readings when utilized on the EAGLE 21 system.
While the Fluke 8846A also has a high impedance setting, it was not used due to unfamiliarity with the meter and a lack of knowledge of the need for high impedance on the EAGLE 21 system.
ANALYSIS OF SAFETY SIGNIFICANCE
After calibration with the incorrect multimeter, Pressurizer Level Channel I trip actuation would have occurred at 92.262% of instrument span exceeding the Allowable Value of 5 92.2% of instrument span.
As discussed in the DESCRIPTION OF THE EVENT section above, both Pressurizer Level Channels II and III remained available and were proven to be operable by the performance of their respective surveillance tests. With Channel I inoperable and Channel II in the tripped condition, Channel III provided trip coincidence. Therefore, the reactor trip safety function was not lost although the function was now susceptible to a single failure.
In addition, the Pressurizer High Water Level reactor trip is not a primary safety function in the safety analysis. It is a back up for any significant heat-up transient which results in a large specific volume change in the reactor coolant system.
Based on this analysis, the safety significance of this condition is considered to be low.
CORRECTIVE ACTIONS
Corrective actions are documented in AR 1836648 and include the following:
1. An Engineering Equivalency Evaluation was performed to assess use of the Fluke Model 8846A multimeter on the EAGLE 21 system and determined acceptable only if used in the high impedance mode.
2. The event was reviewed with Maintenance personnel.
3. Other usage of the Fluke Model 8846A on Units 3 and 4 equipment was reviewed to determine if rework is required. One Unit 4 application will be reworked prior to entry into Mode 4. Unit 4 has been in an extended power uprate outage.
4. Update EAGLE 21 procedures to include:
- Meter approved for use.
- If no equivalent meter is approved, then note that in the M&TE section of the procedure along with why a specific meter is required such as what is required for a system per the vendor's manual.
o Voltage o Frequency o Impedance o Accuracy o Range 5. Review and reinforce procedure AD-AA-100-1006, Procedure and Work Instruction Use And Adherence, with all Maintenance Department personnel.
6. Develop and administer a case study on procedure use and adherence. Include consistency of procedure adherence and what should be done when an unexpected system response is encountered.
7. Revise the M&TE procedure to define what M&TE requires an engineering equivalency evaluation and include specific guidance for processing new M&TE.
FAILED COMPONENTS IDENTIFIED: None PREVIOUS SIMILAR EVENTS: None