05000354/LER-2012-001
| Docket Numbersequential Revmonth Day Year Year Month Day Year N/Anumber No. | |
| Event date: | |
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| Report date: | |
| 3542012001R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Reactor Recirculation (BB)— EIIS Identifier {AD/P}* APRM Flow Units (SC) — EIIS Identifier {IG/FQT} *Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: March 6, 2012 Discovery Date: March 6, 2012
CONDITIONS PRIOR TO OCCURRENCE
Hope Creek was in Operational Condition 1 at 35 percent rated thermal power (RTP). The unit was in single loop operation with the B Reactor Recirculation loop out of service when the miscalibration took place. No other structures, systems or components contributed to the event.
DESCRIPTION OF OCCURRENCE
On 3/1/2012, at 3:19 p.m., the "B" Reactor Recirculation pump {AD/P} tripped unexpectedly causing entry into single loop operation (SLO). The plant remained in SLO for several days to affect repairs to the pump.
On 3/4/2012, at 12:25 a.m., l&C technicians were performing the weekly channel calibration, HC.IC-CC.SE 0032, "Average Power Range Monitor (APRM) Flow Unit Summers," to fulfill the weekly technical specification surveillance requirement. The calibration procedure directs the l&C technician to obtain the value of Total Recirculation Drive Flow (WD) from the Plant Process Computer (PPC) OD-3 and OD-3d report to calculate the desired output voltage of the APRM Flow Unit {IG/FQT}. In SLO, the drive flow (WD) point in the PPC has a "Bad" point quality due to the unavailability of drive flow in the inactive loop. Since the WD value was not available, the l&C technicians obtained a value for WD from the Reactor Engineer and calculated the desired output voltage. The APRM Flow Units were found to be out of the desired voltage range. Adjustments were then made to bring all four Flow Units into the desired voltage range.
On 3/5/2012, at 4:34 a.m., after repairs were completed, the "B" Reactor Recirculation pump was placed back in service. The operators began to raise reactor power.
On 3/6/2012, at 1:20 p.m., with the reactor at 92 percent RTP, the Control Room received an Overhead Alarm C6-D1 "APRM/RBM FLOW REF OFF NORMAL" and "ROD OUT MOTION BLOCK" with computer point CO28. In addition, the 'D' APRM Flow Unit UPSCALE light was illuminated. The Control Room entered abnormal procedure HC.OP-AB.IC-0004, "Neutron Monitoring," and performed the subsequent actions to bypass the 'D' Flow Unit. Upon preliminary assessment, it was discovered that all of the Flow Units were reading abnormally high for the current plant condition.
� The Control Room performed Surveillance Test, HC.OP-ST.BB-0001(Q), "Recirculation Jet Pump Operability — Daily" (Section 5.2 only, Recirculation Loop Flow (APRM Percent Flow) to Total Core Flow) to validate the condition and concluded three of six RPS APRM had failed the channel check in a non conservative direction.
The Control Room entered Technical Specification (TS) 3.3.1 (action a) for the number of OPERABLE channels being less than the required minimum OPERABLE channels for one trip system. The one hour action statement for the limiting condition for operation (LCO) required one Reactor Protection System (RPS) channel be placed in the tripped condition with an additional action to be in START UP in six hours.
The I&C Department promptly performed HC.IC-CC.SE-0032, "APRM Flow Unit Summer," and discovered that all four APRM Flow Units were out of tolerance. The Control Room declared all of the APRMs INOPERABLE at 3:05 p.m., and entered TS 3.3.1 (action b) for the number of OPERABLE channels being less than the required minimum OPERABLE channels for both trip systems. The technicians immediately completed HC.IC-CC.SE-0032 satisfactorily restoring all APRM Flow Units to within calibration tolerances.
Subsequent to this, HC.OP-ST.BB-0001 was performed to retest the all the APRM Flow to Total Core Flow correlation. The test was completed satisfactorily, the APRM Flow Units were declared OPERABLE, and the LCO and AB procedure were exited at 3:24 p.m., on 3/6/12.
CAUSE OF EVENT
An apparent cause evaluation (ACE) was performed. The ACE determined that the cause of the APRM Flow Unit setpoints being non-conservative was inadequate procedural guidance or instructions to provide the technicians with the proper percent recirculation drive flow numbers for the surveillance. The formula provided in the APRM Flow Unit Summer procedure (HC.IC-CC.SE-0032) that calculated the drive flow (WD) was incorrect. The formula proyided in the procedure was for dual loop operation, not for single loop operation.
SAFETY CONSEQUENCES AND IMPLICATIONS
Evaluation determined that the APRM Flow Biased Simulated Thermal Power — Upscale High Flow Clamp at 113.5 percent of rated thermal power was always OPERABLE. The evaluation also determined that the allowable value for the APRM Flow Biased Simulated Thermal Power — Upscale Flow Biased Limiting Safety System Setpoint (LSSS) was exceeded. Although this LSSS is part of the Hope Creek design configuration and TS, the APRM flow biased simulated thermal power scram is not credited in any Hope Creek safety licensing analyses.
A review of this event determined that a Safety System Functional Failure (SSFF) did not occur as defined in Nuclear Energy Institute (NEI) 99-02.
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PREVIOUS OCCURRENCES
A review of Licensee Event Reports for the past three years at Hope Creek was performed to determine if a similar event had occurred. No similar events were noted.
CORRECTIVE ACTIONS
(1) HC.IC-CC.SE-0032 was completed satisfactorily restoring all APRM Flow Units to within calibration tolerances.
(2) Revise procedure HC.IC-CC.SE-0032 to provide guidance for Single Loop Operation Total Recirculation Drive Flow (WD).
COMMITMENTS
This LER contains no regulatory commitments.
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