05000440/LER-2011-003
| Perry Nuclear Power Plant, Unit 1 | |
| Event date: | 10-18-2011 |
|---|---|
| Report date: | 02-29-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4402011003R01 - NRC Website | |
Energy Industry Identification System (EllS) codes are identified in the text as [XX].
INTRODUCTION
During plant startup on October 18, 2011, at 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br />, the plant entered MODE 2 (Startup). At 1619 hours0.0187 days <br />0.45 hours <br />0.00268 weeks <br />6.160295e-4 months <br />, it was discovered that the manual disconnects [DISC] for yard breakers [BKR] S610 and S611 were open with danger tags installed. This switchyard configuration rendered one of two required offsite sources of power INOPERABLE.
Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.1 Condition A was entered for the loss of one source of offsite power. The manual disconnects were subsequently closed, restoring the second source of offsite power. During the time the manual disconnects were open, the delayed access circuit could not be credited for meeting TS LCO 3.8.1. The plant entered MODE 2 which was prohibited by TS LCO 3.0.4. While in MODE 2, before the disconnects were closed, TS LCO 3.8.1 was not met. This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plant's TS.
EVENT DESCRIPTION
On October 18, 2011, at 0012 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, with the plant in MODE 4 (Cold Shutdown), surveillance instruction (SVI) SVI-R10-T5227 "Off-Site Power Availability Verification" was completed to meet Surveillance Requirement (SR) 3.8.1.1 "verify correct breaker alignment and indicated power availability for each required offsite circuit" for all MODEs. Completion of the SVI was to meet TS 3.8.1, "AC Sources-Operating," and establish that two sources of offsite power were OPERABLE. At 0351, the plant entered MODE 2.
On October 18, 2011, at 1619 hours0.0187 days <br />0.45 hours <br />0.00268 weeks <br />6.160295e-4 months <br />, it was discovered that the manual disconnects for yard breakers S610 and S611 were open with danger tags installed. TS LCO 3.8.1 Condition A was entered for the loss of one source of offsite power. At 1646 hours0.0191 days <br />0.457 hours <br />0.00272 weeks <br />6.26303e-4 months <br />, Required Action A.1, Perform surveillance requirement (SR) 3.8.1.1 for OPERABLE required offsite circuit, was completed. At 1659 hours0.0192 days <br />0.461 hours <br />0.00274 weeks <br />6.312495e-4 months <br />, the manual disconnects for S611 were closed and by 1711 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.510355e-4 months <br />, the manual disconnects for S610 were closed. The second required source of offsite power became available upon closure of the four manual disconnects. At 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br />, the delayed access circuit was declared OPERABLE after verification of the switchyard lineup.
CAUSE OF EVENT
Switchyard equipment configuration, necessary to maintain reliable sources of offsite power, was not held to the same operational configuration standards required for plant controlled equipment. Policies governing switchyard equipment were less than adequate to ensure the operators knew the position of the manual disconnects. This is a latent organizational weakness that had not previously manifested itself due to the working relationship between the Perry switchyard coordinator and operations. The recent turnover of the switchyard coordinator position exposed the fact that configuration cognizance of switchyard equipment was overly reliant upon individual expertise and experience rather than being process based.
Processes normally utilized to maintain configuration of plant controlled equipment include; the LCO/ Potential Limiting Condition for Operation (PLCO) process, the clearance program, procedures, plant status control drawings, and the work management process. These processes were not considered necessarily applicable for use on switchyard equipment associated with offsite power supplies because the clearance, operation, and maintenance activities for this equipment was controlled and performed by non-station personnel.
EVENT ANALYSIS
During plant startup on October 18, 2011, with the plant in MODE 4, the unit one startup transformer [XFMR] [EA] was INOPERABLE. For operation in MODES 1, 2, or 3, the two required qualified circuits between the offsite transmission network and the onsite Class 1 E AC Electric Power Distribution System were the unit 2 startup transformer and the backfeed lineup through the unit one auxiliary transformer (delayed access circuit). Use of the delayed access circuit was allowed by approved License Amendment No. 160 until December 12, 2011.
On October 18, 2011, at 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br />, the plant entered MODE 2. At 1619, it was discovered that the manual disconnects for yard breakers S610 and S611 were open. The license amendment considers specific manual actions necessary to align the delayed access circuit to the plant's safety buses. These actions are contained in ONI-SPI F-1, "Off-Site Power Restoration," and ONI-SPF F-2, "Yard Inspection." These procedures do not provide direction on restoration of the manual disconnects for yard breakers S610 and S611. Therefore, the delayed access circuit was not OPERABLE when the plant entered MODE 2.
On October 18, 2011, at 1711 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.510355e-4 months <br />, the four disconnects for yard breakers S610 and S611 were closed. SVI-R10-T5227 was completed by 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> and the delayed access circuit was declared OPERABLE.
OPERABILITY requirements for two qualified offsite circuits between the offsite transmission network and the onsite Class 1E AC Electric Power Distribution System were not met for TS LCO 3.8.1 when the plant transitioned from MODE 4 to MODE 2. This was an operation prohibited by TS LCO 3.0.4 which prohibits MODE changes under certain conditions when an LCO is not met. In addition, between 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> and 1711 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.510355e-4 months <br /> on October 18, 2011, TS LCO 3.8.1 Required Action F.1 (be in MODE 3, Hot Shutdown, in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />) was not met.
This event has no quantitative change in the current core damage frequency as the Probabilistic Risk Assessment (PRA) model does not model the availability of the backfeed lineup for power restoration purposes.
From the qualitative probabilistic risk perspective, the additional time that would have been required to re-establish this backfeed alignment is viewed to have a non-risk significant effect as re-establishment of the offsite power through this source would not have prevented the transient or would have been utilized as part of the initial mitigating strategy. This alignment would most likely be utilized in the event of a loss of the remaining startup transformer. Had this failure occurred within the timeframe involved, all emergency diesel generators were available and would have been expected to provide onsite AC power. Re-establishment of offsite power in this event would not have been time critical or risk significant. Based on this analysis, this event is viewed as having small safety significance.
CORRECTIVE ACTIONS
A daily surveillance requirement check was established to check the position of the disconnect switches associated with the breakers in the yard. The check was performed twice per day when the delayed access circuit was relied upon as a qualified offsite source of power.
SVI-R10-T5227 was revised to add checks of components on the switchyard side of the main transformers when qualifying the auxiliary transformer as a delayed source.
Operations Night Order, "Switchyard Clearance and Switching Orders," was issued to ensure control room personnel have a complete understanding of switchyard configuration.
Operations Administrative Instruction (OAI) 0AI-1701, Tracking of LCOs, will be revised to provide specific guidance to generate an LCO if the alignment of switchyard components impacts (or has the potential to impact) the operability of an off-site power source. A policy will be created that delineates the expectations of switchyard configuration cognizance in order to ensure offsite power source reliability.
Licensed operators and shift engineers will be trained to Nuclear Operating Procedure (NOP) NOP-OP- 1003, Grid Reliability Protocol, as it relates to the importance of knowing the status of offsite power sources and related TS.
Licensed operators and staff that process mode restraints will be trained to this event and lessons learned to prevent the reoccurrence of closing a mode restraint prior to the issue being completely resolved.
Plant Equipment Rounds will be revised to include a daily inspection of the transmission yard.
PREVIOUS SIMILAR EVENTS
A review of Licensee Event Reports and the corrective action database for the past three years determined that two similar events had occurred.
leak on the Emergency Closed Cooling Water subsystem B (ECCW B) [CC]. When ECCW B was declared INOPERABLE, the completion time for TS LCO 3.7.10 "ECCW System," Condition B had been exceeded. This was a condition prohibited by TS.
The corrective actions associated with this event focused on revision of the prompt operability determination process and training on the event. These corrective actions would not have reasonably been expected to have prevented the event documented in LER 2011-003.
Startup Transformer Issues, documented two issues associated with the unit one startup transformer.
The issues were the inappropriate use of a delayed access circuit as a qualified source of offsite power and a transformer failure that resulted in a plant shutdown.
The corrective actions associated with these events focused on a license amendment and TS Bases revision to clarify available qualified sources of offsite power and replacement of the unit 1 startup transformer. These corrective actions would not have reasonably been expected to have prevented the event documented in LER 2011-003.
COMMITMENTS
There are no regulatory commitments contained in this report. Actions described in this document represent intended or planned actions, are described for the NRC's information, and are not regulatory commitments.