05000277/LER-2009-001
| Peach Bottom Atomic Power Station Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2772009001R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 2 was operating at 100% of rated thermal power when the condition prohibited by Technical Specifications occurred. There were no other structures, systems or components out of service that contributed to this event.
Description of the Event
On 2/13/09 at approximately 0933 hours0.0108 days <br />0.259 hours <br />0.00154 weeks <br />3.550065e-4 months <br />, Operations personnel (Utility, Licensed) discovered that a non-compliance existed with Technical Specifications (TS) when a TS Required Action for an inoperable Control Rod (Control Rod 10-51) was found to be not implemented. This discovery was based on a report by Operations personnel performing a plant walkdown in preparation for venting of Control Rod Drive (EIIS:AA) Hydraulic Control Units (HCUs).
TS Limiting Condition for Operation (LCO) 3.1.3, Control Rod Operability Required Action C.2 requires that for an inoperable Control Rod (EIIS: JC), the associated Control Rod Drive (CRD) must be disarmed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the Control Rod becoming inoperable. The method for disraming the CRD is typically to deenergize the Directional Control Valves associated with the associated CRD HCU. Contrary to this requirement, Control Rod 10-51 was inoperable since 2/11/09 at approximately 0604 hours0.00699 days <br />0.168 hours <br />9.986772e-4 weeks <br />2.29822e-4 months <br />, yet the Control Rod was discovered to be armed at 0933 hours0.0108 days <br />0.259 hours <br />0.00154 weeks <br />3.550065e-4 months <br /> on 2/13/09.
Control Rod 10-51 was being considered inoperable due to a safety clearance applied to perform maintenance on the HCU (EIIS:HCU) associated with Control Rod 10-51. Although the maintenance on the HCU was completed on 2/12/09, the Control Rod was still considered inoperable pending post-maintenance surveillance testing. A safety clearance had been in place to maintain the Control Rod inserted and disarmed in order to comply with LCO 3.1.3 Required Actions C.1 (Control Rod fully inserted) and C.2 (disarmed associated CRD).
This condition prohibited by TS occurred when the associated CRD for Control Rod 10-51 was incorrectly re-armed due to an operator error (Utility, Non-licensed) associated with the performance of a safety clearance in preparation for HCU venting. This error was made by an Equipment Operator (EO) on 2/12/09 at approximately 0530 hours0.00613 days <br />0.147 hours <br />8.763227e-4 weeks <br />2.01665e-4 months <br />.
This report is being submitted pursuant to:
10CFR 50.73(a)(2)(i)(B) — Condition Prohibited by TS — This occurrence is reportable under this criterion since the TS LCO 3.1.3 Required Action C.2 was not complied with for an inoperable Control Rod.
� Description of the Event, continued Once the condition prohibited by TS was discovered on 2/13/09 at approximately 0933 hours0.0108 days <br />0.259 hours <br />0.00154 weeks <br />3.550065e-4 months <br />, prompt action was taken to disarm the associated CRD for Control Rod 10-51. This prompt action was completed by approximately 0942 hours0.0109 days <br />0.262 hours <br />0.00156 weeks <br />3.58431e-4 months <br /> on 2/13/09, thereby exiting the period of non-compliance.
Analysis of the Event
There were no actual safety consequences associated with this event.
The Control Rod and drive mechanism provides control of reactor power, including the ability to provide a sufficiently rapid insertion of control rods (scram) so that no fuel damage results from any abnormal operating transient and limits fuel damage under accident conditions. The 185 control rods are located uniformly throughout the core. The Control Rods are operated by CRD mechanisms. The CRD hydraulic system HCU supplies and controls the pressure and flow requirements to the CRDs. The HCUs provide hydraulic power to be able to position Control Rods in the Reactor core. HCU scram accumulators are designed with a limited nitrogen ,pressure and volume, which are sufficient to initiate control rod scram motion.
During the event, Control Rod 10-51 remained fully inserted into the Reactor core. Although the HCU directional control valves were not re-armed at the appropriate time (i.e., not yet ready to perform the post-maintenance test on Control Rod 10-51), the HCU was restored to a condition, where it was able to perform its described safety design function. Had the Control Rod been inadvertently withdrawn during the period of non-compliance, the hydraulic portion of the HCU was capable of initiating a scram of the Control Rod. Subsequent post-maintenance surveillance testing performed on 2/14/09 demonstrated operability of this Control Rod. There were no other Control Rods adversely affected by this non-compliance.
This event is not considered risk significant.
Cause of the Event
The primary cause of this event was due to a failure to properly follow the associated safety clearance performance requirements. An Equipment Operator (Utility, Non-licensed) was directed by the Work Execution Center Supervisor (Utility, Licensed) to perform the next step of the associated clearance for HCU 10-51. This step of the clearance would allow for the HCU to be hydraulically restored in preparation for post-maintenance surveillance testing that was planned to be conducted during a unit load reduction on 2/14/09. The clearance directed HCU restoration in accordance with a System Operation (SO) procedure (SO 3.7.C-2, Venting A Hydraulic Control Unit for Return to Service) up through step 4.6.5. Contrary to this direction, � Cause of the Event, continued the Equipment Operator performed SO 3.7.C-2 through step 4.7, which included rearming (i.e., re-energization) of the HCU direction control valves. This resulted in the negation of the controls put in place to ensure that TS LCO Required Action C.2 was satisfied.
Contributing causes included inadequate oversight of the Equipment Operator actions by the Work Execution Center Supervisor and an inadequate pre-job brief / independent verification.
Corrective Actions
Qualifications of individuals involved with this event were removed pending remediation.
The lessons learned from this human performance issue will be shared with other personnel in accordance with the site Corrective Action Program.
Other management interventions were performed to strengthen administrative programs including procedural place-keeping and pre-job briefs.
Other actions are being pursued in accordance with the Corrective Action Program.
Previous Similar Occurrences There were no previous LERs identified relating to inappropriate clearance control, where a TS Required Action was negated.
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