05000324/LER-2005-001
| Telephone Number (Include Area Code) | |
| Event date: | 03-31-2005 |
|---|---|
| Report date: | 05-23-2005 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3242005001R00 - NRC Website | |
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
INTRODUCTION
On March 31, 2005, operators were dispatched to disarm Control Rod Drive (CRD) System Hydraulic Control Units (HCUs) [AA/HCU] in accordance with the Technical Specification (TS) in support of CRD replacement activities. During the disarming effort, an error was made that resulted in the failure to disarm one of the required CRDs, which ultimately resulted in the failure to comply with TS Required Actions.
This condition was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as an operation or condition prohibited by the TS.
EVENT DESCRIPTION
Initial Conditions Unit 2 was in day 26 of refueling outage B217R1, operating in Cold Shutdown (i.e., Mode 4), at 0 percent rated thermal power. Control rod (CR) 46-43 could not be properly coupled to its control rod drive mechanism (CRDM), so activities were underway to replace the CRDM, requiring the associated control rod to be fully withdrawn from the reactor core.
Discussion TS Limiting Condition for Operation (LCO) 3.10.4, "Single Control Rod Withdrawal-Cold Shutdown," allows the reactor mode switch position to be changed from Shutdown to Refuel while operating in Mode 4 and operation considered not to be in Mode 2 (i.e., Startup) to allow withdrawal of a single CR and subsequent removal of the associated CRD provided the following requirements are met:
a. All other CRs are fully inserted; b. 1. LCO 3.9.2, "Refuel Position One-Rod-Out Interlock," and LCO 3.9.4, "Control Rod Position Indication,"
OR
2. A CR withdrawal block is inserted; c. 1. LCO 3.3.1.1, "Reactor Protection System (RPS) Instrumentation," Mode 5 requirements for Functions 1.a, 1.b, 7, 10, and 11 of Table 3.3.1.1-1, and LCO 3.9.5, "Control Rod OPERABILITY—Refueling,"
OR
2. All other CRs in a five by five array centered on the CR being withdrawn are disarmed; at which time LCO 3.1.1, "SHUTDOWN MARGIN (SDM)," Mode 4 requirements, may be changed to allow the single CR withdrawn to be assumed to be the highest worth CR.
EVENT DESCRIPTION (continued) On March 31, 2005, in support of replacing CRDM 46-43, operations personnel implemented the requirements of TS LCO 3.10.4. Rerndval of the associated CRDM results in inoperability of the associated CR and loss of position indication for that rod. In order to perform the required CRDM 4643 removal, the following actions were taken.
Time Action TS Compliance 0545 Initiated the disarming of a five by five array of LCO 3.10.4 c.2. versus c.l.
CRDs centered on CR 46-43 1749 CR 46-43 fully withdrawn LCOs 3.10.4 a., 3.10.4 b.1., and 3.10.4 c.1. met 2205 Established a clearance to deactivate HCU 46-43 and N/A thus rendered the associated control rod inoperable 2208 Inserted control rod withdrawal block LCO 3.10.4 b.2. versus b.l.
With the completion of these actions, CRDM 4643 removal activities began.
At 2245 hours0.026 days <br />0.624 hours <br />0.00371 weeks <br />8.542225e-4 months <br />, during walkdown activities, operations personnel identified that an error had occurred during disarming of the CRDs to establish the required five by five array. Specifically, CRD 34-47 had been disarmed versus CRD 3847. Therefore, from 2205 until 2245 hours0.026 days <br />0.624 hours <br />0.00371 weeks <br />8.542225e-4 months <br />, the plant was in TS 3.10.4, Condition B, (i.e., LCO 3.10.4 c.2. was not met due to failure to disarm the 5 by 5 array), without having implemented the associated Required Actions. The failufe to establish the conditions required by TS resulted in a reportable condition in �with 10 CFR 50.73(a)(2)(i)(B) as an operation or condition prohibited by the Technical Specifications.
Upon discovery of the error, operators immediately initiated actions to disarm CRD 3847 and independently verified that no other discrepancies existed that could have prevented compliance with TS 3.10.4 requirements.
EVENT CAUSE
The cause of this occurrence is attributed to the lack of adequate barriers within the configuration control process used to disarm the CRD five by five array. A contributing cause is the failure of the individuals involved with the disarming activity to meet the work standards as established in procedures and through management expectations for ensuring adequate configuration control.
OAI-58.2, "Equipment Control, Test Status and Caution Tagging," governs the use of equipment control (EC) sheets and tagging. This process did not include provisions for independent verification of EC tags and thereby, relied upon the performance of a single individual to complete an activity required to satisfy TS requirements.
Review of the factors affecting human performance during the disarming activity determined that the auxiliary operator with primary responsibility for establishing the EC tag for HCU 38-47 had (1) not attended the pre job brief conducted for the activity and thus was not fully aware of the potential to affect TS compliance and (2) did not comply with the practice as established in 001-01.02, "Shift Routines and Operating Practices," Attachment 19, "Operations Performance Standards," for signing off steps in the process as the steps were completed.
CORRECTIVE ACTIONS
As an interim corrective measure, a Standing Instruction was issued to require independent verification of EC tag hanging on components and systems important to safety.
OAI-58.2 will be revised to require independent verification of EC activities implemented to ensure compliance with TS or other regulatory requirements.
The individuals involved with establishing the 5 by 5 array were coached on tag hanging practices and related expectations as delineated in 001-01.02.
A review of the lessons learned from this event will be conducted with appropriate operations shift personnel.
SAFETY ASSESSMENT
The significance of this occurrence is considered minimal in that the noncompliance with the TS occurred for approximately 40 minutes and during that time, no CR manipulations were made. During the period that the disarming error existed, a CR withdrawal block had been established as part of the actions taken to comply with TS LCO 3.10.4 and thus prevented the possibility of manipulating another CR. In considering the potential consequences of this occurrence, even if CR 38-47 had been manipulated during the period of concern, strongest-CR-out testing performed prior to this occurrence confirms that an inadvertent criticality event would not have occurred.
PREVIOUS SIMILAR EVENTS
A review of events occurring within the past three years has not identified any previous similar occurrences.
Although previous non-reportable occurrences involving work performance and problems encountered during execution of the equipment control process were identified, none of these occurrences were considered significant in relation to the occurrence reported herein (i.e., the corrective actions taken for the earlier events could not be reasonably expected to have prevented this occurrence).
COMMITMENTS
No regulatory commitments are contained in this report. Those actions discussed in this submittal will be implemented in accordance with corrective action program requirements.