05000255/LER-2006-005

LER-2006-005,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(A), System Actuation
2552006005R00 - NRC Website

U.S. NUCLEAR REGULATORY COMMISSION Palisades Nuclear Plant 05000-255 2006 -- 005 -- 00

EVENT DESCRIPTION

On May 10, 2006, an unexpected quadrant power tilt was identified during reactor [RCT;AB] core startup physics testing. At the time of discovery, plant power was being maintained at approximately 22% following initial power ascension from a recently completed refueling outage.

On May 11, 2006, subsequent analysis of core power distribution data determined the most probable cause of the quadrant power tilt to be Control Rod 33 [ROD;AA] fully inserted into the core as opposed to being fully withdrawn as indicated.

Based on this conclusion, Off Normal Procedure ONP-5.1, "Control Rod Drop" was conservatively entered and a shutdown to Mode 5 was initiated to facilitate further troubleshooting. The reactor was manually tripped from approximately 11% power in accordance with procedural guidance.

On May 13, 2006, investigation determined that Control Rod 33 was uncoupled from its drive assembly, having not been successfully coupled during the refueling outage. Consequently, Control Rod 33 had remained fully inserted into the core throughout plant startup from the refueling outage.

Prior to discovery, the upward mode changes into Mode 2 and Mode 1 that occurred on May 9 and May 10, 2006, respectively, were performed in violation of Technical Specification (TS) 3.0.4, since the intent of TS 3.1.4.D.1 is to prevent a reactor startup with an immovable control rod.

Consequently, this event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as operation which was prohibited by Technical Specifications. In addition, the manual reactor protection system [JC] actuation is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).

CAUSE OF THE EVENT

The failure to couple Control Rod 33 involved deficiencies in performance of the coupling procedure, as well as deficiencies in verification and oversight of the activity.

CORRECTIVE ACTIONS

Control Rod 33 was coupled to its drive assembly.

The activity of coupling control rods will be strengthened through a combination of procedural enhancements, personnel qualification improvements, and additional administrative controls.

U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) PAGE (3) LER NUMBER (6) DOCKET NUMBER (2) Palisades Nuclear Plant 05000-255 2006 -- 005 -- 00

SAFETY SIGNIFICANCE

The safety significance of this occurrence is considered minimal. Since the inserted control rod was identified prior to exceeding 25% power, TS required actions for one misaligned and immovable control rod were already satisfied without further action.

For the manual reactor trip, the reactor protection system functioned as expected.

This event does not involve a safety system functional failure.

PREVIOUS SIMILAR EVENTS

None