05000263/LER-2011-011
| Monticello Nuclear Generating Plant | |
| Event date: | 12-01-2011 |
|---|---|
| Report date: | 01-26-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2632011001R00 - NRC Website | |
EVENT DESCRIPTION
On November 30, 2011, the plant was in MODE 4 (cold shutdown) with the Reactor Mode Switch [JC/JD] in Refuel position for a Control Rod Drive (CRD) [AA] exercise. The CRD exercise testing was being performed under Special Operations Technical Specification (TS) 3.10.4, "Single Control Rod Withdrawal - Cold Shutdown" using the procedure 0074, "Control Rod Drive Exercise." CRDs are exercised to ensure they are properly vented prior to manipulation for startup.
At 1523 hours0.0176 days <br />0.423 hours <br />0.00252 weeks <br />5.795015e-4 months <br /> on November 30, 2011, Special Operations TS 3.10.4 was entered to begin the CRD exercise. Special Operations TS 3.10.4 permits the withdrawal of a single control rod [ROD] for testing or maintenance, while in cold shutdown, by imposing certain restrictions. TS Limiting Condition for Operation (LCO) 3.10.4 requires TS LCO 3.9.2, "Refuel Position One- Rod-Out Interlock" to be met. One of the Surveillance Requirements (SR) for TS 3.9.2, SR 3.9.2.1, requires verification every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> that the Mode Switch is locked in the Refuel position. The TS Bases for SR 3.9.2.1 defines "locking" the Mode Switch as removing the reactor mode switch key from the console. Locking the Reactor Mode Switch is an additional administrative control to preclude operator errors.
At 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on December 1, 2011, a scheduled Control Room shift change was made. During a panel walkdown at 2142 hours0.0248 days <br />0.595 hours <br />0.00354 weeks <br />8.15031e-4 months <br />, the new Control Room crew found the Reactor Mode Switch was unlocked in the Refuel position. The crew recognized that this was not in conformance with the TS Bases for SR 3.9.2.1, and declared LCO 3.9.2 and LCO 3.10.4 not met. The Mode Switch was locked in the Refuel position at 2145 hours0.0248 days <br />0.596 hours <br />0.00355 weeks <br />8.161725e-4 months <br />. Failure to lock the Mode Switch in the Refuel position during the Control Rod Drive exercises was not in compliance with SR 3.9.2.1, and TS LCO 3.10.4.
No structures, systems, or components were inoperable at this time that contributed to this event.
EVENT ANALYSIS
Per 10 CFR 50.73(a)(2)(i)(B), an Operation or Condition Prohibited by Technical Specifications requires a Licensee Event Report. There is no requirement for reporting in accordance with 10 CFR 50.72 for this event. This event is not considered a safety system functional failure.
SAFETY SIGNIFICANCE
The one-rod-out interlock is designed to ensure that no more than one control rod may be withdrawn at a time, in order to prevent the reactor from becoming critical during refueling operations. The Mode Switch remained in the Refuel position during all Control Rod movements, so the one-rod-out interlock remained capable of preventing more than one Control Rod from being withdrawn. Additionally, no more than one Control Rod was withdrawn at any time. Therefore, there was no safety significance to this event.
CAUSE
The cause of the event was Operator work practices. A contributing cause to the event is that procedures placed Operators in knowledge-based performance and did not include adequate information necessary to consistently ensure that the TS Surveillance Requirements for SR 3.9.2.1 were met (i.e., removing the reactor mode switch key).
CORRECTIVE ACTION
The following corrective actions have been completed:
- Individuals involved have been coached and counseled on their role in this event.
Tabletop exercises were completed to ensure the individuals involved in the event demonstrate expected behaviors.
- The applicable procedures were revised to ensure consistent implementation of the TS surveillance requirements.
- Additional just-in-time training for Operations was developed and implemented to include potential faults that could occur during start-up activities.
PREVIOUS SIMILAR EVENTS
In April 2007, Monticello failed to enter a required Technical Specification Action during Control Rod Drive exercising (LER 05000263/2007-003-01). Operators failed to recognize that the Control Rod full in position indicator for 26-35 was not operable during performance of a CRD exercise under TS 3.10.4 with the plant in Mode 4. Consequently, Operators failed to enter TS Action 3.9.2.A and testing was performed on an additional control rod. This resulted in non- compliance with TS 3.9.2 since the one-rod-out interlock was inoperable and control rod withdrawal was not immediately suspended.
Additionally, on November 27, 2011, while performing the Rod Worth Minimizer (RWM) Operability Test as part of startup activities, it was discovered that the RWM control switch was in the Bypass position (LER 05000263/2011-010-00). With the control switch in the Bypass position, the RWM was inoperable and did not enforce the pre-determined control rod withdrawal sequence. This resulted in non-compliance with TS 3.3.2.1, "Control Rod Block Instrumentation," since the control rod block was inoperable during startup preparation activities.
ADDITIONAL INFORMATION
Energy Industry Identification System (EIIS) codes are identified in the text within brackets [ ].