05000254/LER-2006-002

LER-2006-002, Quad Cities Nuclear Power Station Unit 1 05000254 1 of 3

Docket Number
Event date:	02-22-2006
Report date:	04-14-2006
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2542006002R00 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Quad Cities Nuclear Power Station Unit 1 05000254 NUMBER6 NUMBER (If more space is required, use additional copies of NRC Form 366A)(17)

PLANT AND SYSTEM IDENTIFICATION

General Electric - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in the text as [XX].

EVENT IDENTIFICATION

Automatic Reactor Scram From Turbine/Generator Load Reject due to Degraded Current Transformer Wiring on the Main Power Transformer CONDITION PRIOR TO EVENT A.

Unit: 1 Event Date: February 22, 2006 Event Time: 0122 hours0.00141 days <br />0.0339 hours <br />2.017196e-4 weeks <br />4.6421e-5 months <br /> Power Level: 085% Reactcr Mode: 1 Mode Name: Power Operation DESCRIPTION OF EVENT B.C On February 22, 2006, at 0122 hours0.00141 days <br />0.0339 hours <br />2.017196e-4 weeks <br />4.6421e-5 months <br />, an automatic reactor scram occurred on Quad Cities Nuclear Power Station Unit 1 in response to a turbine/generator [TG] load reject.

The event was initiated by a trip of the main power transformer (MPT) [XFMR][EL] `B'phase differential overcurrent relay [87]. The relay trip was caused by degraded wiring insulation, resulting in a ground in the current transformer (CT) `C'phase wiring at a box mounted on the MPT. The degraded wiring insulation resulted in a direct short to ground at or near the box in the associated conduit run and a resultant trip of the protective differential overcurrent relay.

All control rods inserted to the full-in position. The reactor was brought to the hot shutdown condition using normal methods and was maintained in hot shutdown during investigation and repair of the MPT issue until the reactor was returned to power operation on February 24, 2006. The plant operated as designed with no abnormal issues or failures, with one exception. The fire deluge on the MPT, expected to actuate during a differential overcurrent trip, did not actuate.

CAUSE OF EVENT C.

The degraded wiring insulation in the CT was caused by the fact that the MPT wiring design and installation of the wiring assembly (interconnection boxes, conduit, pull-boxes, and wiring) was not adequate to support design life of the transformer.

Vibration of certain conduits, pull-boxes, interconnection boxes, and control boxes resulted in abnormal wear of the wiring insulation.

The failure of the MPT deluge to activate was due to a cross-threaded screw on the deluge contact on the differential overcurrent relay that had become loose over time.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) (If more space is required, use additional copies of NRC Form 366A)(17)

D. SAFETY ANALYSIS

The safety significance of this event was minimal. All control rods inserted to the full-in position. The reactor was brought to the hot shutdown condition using normal methods and was maintained in hot shutdown during investigation and repair of the MPT issue until the reactor was returned to power operation.

An Emergency Notification System call was made at 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> on February 22, 2006, in accordance with 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System Actuation..

This report is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in manual or automatic actuation of the reactor protection system.

E. CORRECTIVE ACTIONS

Corrective Actions Completed:

New external CT wiring was routed and tested prior to reactor startup.

The MPT sudden pressure relay (SPR) trip wiring was inspected to the extent: possible and practical, and insulation degradation identified was repaired.

The wiring for the MPT coolers was inspected to the extent possible and practical, and insulation degradation identified was repaired.

The differential overcurrent relay was replaced.

Corrective Actions to be Completed:

Unit 1 MPT SPR and cooler group wiring will be re-wired to bypass the suspect wirinc

• . A spare Unit 2 MPT of a different design has been installed during the recent spring refueling outage; therefore the condition of the wiring on the Unit 2 MPT is not in question.

The design specifications for the Unit 1 MPT will be upgraded to ensure the MPT electrical assembly will operate for its design life.

F. PREVICUS OCCURRENCES

No reportable instances of worn wiring on an MPT were identified at Quad CLties Nuclear Power Station for the last three years. However, there have been non-reportable instances of evidence of damaged or degraded wiring since the installation of the Unit 1 MPT in March 2005. These instances were primarily in three specific cooling banks, and corrective actions specific to the events were implemented.

G. COMPONENT FAILURE DATA

The Unit 1 MPT is a new transformer that was manufactured by ABB at the Cordoba, Spain, factory (serial # 63006, manufacturing date 2002), and was installed at Quad Cities Nuclear Power Station in March 2005.