05000261/LER-2014-002
| H. B. Robinson Steam Electric Plant, Unit No. 2 | |
| Event date: | 06-26-2014 |
|---|---|
| Report date: | 01-26-2015 |
| 2612014002R00 - NRC Website | |
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H. B. Robinson Steam Electric Plant, Unit No. 2 05000 261
PLANT IDENTIFICATION
Westinghouse. Pressurized Water Reactor
BACKGROUND
On 11/26/2014, with the plant operating at 100% power and no involvement of out-of-service structures, systems or components, it was discovered that the practice of utilizing ERFIS [CPU] (Emergency Response Facility Information System or ERFIS) to monitor Rod Position Indication (RPI) when the installed indicators [MTR] have been determined to have failed was not allowed by the current licensing basis.
TS 3.1.7 Required Actions A.1 or A.2 for one RPI inoperable require the determination of the affected rod's position using the incore detector system [IG] or reducing power to less than 50 percent rated thermal power (RTP). Either of these actions are required to be completed within eight (8) hours upon discovery of the failed RPI. Failing to satisfy Condition A would have required entry into Condition D (be in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />).
EVENT DESCRIPTION
On 11/26/2014, with the plant operating at 100% power, a discussion was held with the Senior Resident Inspector regarding the site's practice of utilizing the ERFIS display to credit RPI when an installed indicator was determined to have failed. This practice was not allowed per the current licensing basis (CLB).
A review of operator logs was performed and the only incident where this occurred in the previous three (3) years was 6/26/2014.
During a Reactor-Turbine Gauge Board (RTGB) [MCBD] walk-down by Licensed Control Room Operators on 6/26/2014, a condition was identified that Control Bank 'B' rod K-14 indicated 130 inches on the RTGB while the ERFIS indication was 140.81 inches. After a review of Technical Specification (TS) Limiting Condition for Operation (LCO) 3.1.7 and Operations Surveillance Test (OST)-020 procedural requirements for RPI operability, it was determined by the Licensed Operations Shift personnel that entry into the required actions for Limiting Conditions for Operation (LCO) 3.1.7 was not required. ERFIS was documented as an acceptable method for determining RPI system operability and all ERFIS RPI indications were normal and within limits.
The signal conditioner [IMOD] that input to the RPI indicator was replaced on 06/30/2014. The time required for this replacement was beyond the time allowed completion by the TS 3.1.7 Required Actions A.1 or A.2 and D. Since the RPI Indicator issue was not resolved within the allowed Completion Times for Conditions A and D, a violation of TS 3.1.7 occurred .
Upon determination that the practice of crediting ERFIS for RPI Indicator operability was not allowed by the CLB, Standing Instruction 14-023 was issued to suspend this practice. Procedure Revision Requests (PRRs) were initiated to revise procedures to remove language that supported operator actions to credit the ERFIS display. A Condition Report (CR) was initiated and a cause evaluation was conducted.
CAUSAL FACTORS
The cause of the failed RPI indicator was not determined.
Historical - In 1997, the H. B. Robinson Steam Electric Plant, Unit No. 2 (HBRSEP2) Engineering Service Request (ESR) 97- 00611 review process failed to recognize the need to initiate actions necessary to align the language between the ESR Revision 1 conclusion and the Technical Specification Bases (TSB) Documents for 3.1.4 — Rod Group Alignment Limits and TSB 3.1.7 — Rod Position Indication to include the details necessary to justify ERFIS was an acceptable means of rod position indication.
CAUSAL FACTOR (Continued) The team investigating the condition considered the revision of the OSTs in 1997 (based on the ESR Revision 1) allowing the use of ERFIS in lieu of RPI reinforced this as an acceptable practice. This common understanding of procedural allowance possibly established a sense of security that prevented any additional challenges since 1997 regarding the alignment of the TSB language and the supporting OST procedures. This misalignment recently surfaced due to plant conditions and operator actions and was challenged because the TSB defines system/component boundaries and does not specifically recognize ERFIS as a supplemental data source.
CORRECTIVE ACTIONS
Completed:
The RPI indicator that failed on 06/26/2014 was repaired by maintenance personnel on 06/30/2014. The signal conditioning card [IMOD] for the indication was replaced and calibrated. This restored compliance with TS 3.1.7.
Standing Instruction 14-023 was issued to stop the practice of crediting ERFIS for TS RPI when the installed indicator is found to have failed. Procedure Revision Requests (PRRs) were initiated to revise Operations Surveillance Test (OST) procedures to remove language that supported operator actions to credit the ERFIS display.
SAFETY ANALYSIS
Subsequent troubleshooting of the RPI system revealed that the output from the signal conditioning card that provides input to the RTGB indicator had failed and the output from the signal conditioning card for ERFIS display for the control rod in question was accurate with regards to its position; thus the control rod was within required limits. Other indications of rod misalignment (e.g.
quadrant power tilt ratio, axial flux difference, and core exit thermocouple temperatures [TE]) did not indicate any rod misalignment. The Rod At Bottom indicating light [IL] remained operable. If a reactor trip or other transient required the insertion of the control rods, the Licensed Reactor Operators would have had sufficient indication that the effected control rod was fully inserted. As a result, there were no safety impacts from this event.
ADDITIONAL INFORMATION
An Operating Experience (OE) search for related events at HBRSEP2 and across the industry was conducted. No relevant OE was found.
Energy Industry Identification System (EIIS) codes for systems and components relevant to this event are identified in the text of this document within brackets [ ].