05000316/LER-2006-001

LER-2006-001, Failure to Comply with Technical Specification 3.6.2, Containment Air Locks

Docket Number
Event date:	03-13-2006
Report date:	05-11-2006
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
LER closed by
IR 05000315/2006010 (10 August 2006)
3162006001R00 - NRC Website

Conditions Prior to Event Unit 2 — Mode 1 at 100% power.

Description of Event

On March 14, 2006, at approximately 0941 hours0.0109 days <br />0.261 hours <br />0.00156 weeks <br />3.580505e-4 months <br />, with Donald C. Cook Nuclear Plant (CNP) Unit 2 in MODE 1, Maintenance test technicians conducted routine operability testing of the inner and outer airlock doors for the Unit 2 Lower Containment Airlock (2-AIRLOCK-C612) [AL]. The inner airlock door was tested first and successfully passed its operability test. The outer airlock door was subsequently tested and audible leakage was detected by test personnel. Indiana Michigan Power Company (I&M) immediately investigated the cause of the excessive leakage and determined that the airlock door latching mechanism was not fully engaged. The lack of full engagement resulted in insufficient seating of the equalizing air valve. Upon discovery, the outer airlock door was immediately sealed dosed. Upon obtaining proper closure of the outer airlock door, the outer airlock door was re-tested, resulting in a successful leak rate of 0.0 SCCM.

l&M performed a review of the usage for 2-AIRLOCK-C612 and determined that contract Maintenance personnel last used 2-AIRLOCK-C612 on March 13, 2006, at approximately 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />.

l&M reviewed Technical Specification 3.6.2, Containment Air Locks, and determined that the requirement of Required Action A.1, which for this event required the inner airlock door be verified closed within one hour, was not met. Therefore, this event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications. During the time period of this event the inner airlock door was closed and operable and 2-AIRLOCK-C612 was capable of performing its design function.

Cause of Event

The cause of this error has been determined to be improper operation of the airlock doors associated with 2-AIRLOCK-C612 by contract maintenance personnel.

Analysis of Event

The configuration of the partially closed outer airlock door meant that the outer airlock door for 2-AIRLOCK-C612 may not have been able to perform its design function. However, the inner airlock door was operable and properly dosed and capable of performing its designed safety function. The period of inoperability for the outer airlock door includes the time from the previous opening of the outer door on March 13, 2006, at approximately 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />, and continuing to the successful completion of the operability surveillance test on March 14, 2006, at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br />.

Each air lock door has been designed and tested to certify its ability to withstand pressure in excess of the maximum expected pressure following a Design Basis Accident in containment. As such, closure of a single door supports containment operability. Each of the doors contains double-gasketed seals and local leakage rate testing capability to ensure pressure integrity. To affect a leak-tight sea!, the air lock design uses pressure- seated doors (i.e., an increase in containment internal pressure results in increased sealing force on each door).

Consequently, it is judged that this event would not have resulted in any airlock leakage from containment during an accident, and the airlock remained fully functional during this time because the inner door was in the proper closed position.

Corrective Actions

Actions Taken:

The outer airlock door of 2-AIRLOCK-C612 was immediately sealed dosed and successfully leak tested.

The inner airlock door for 2-AIRLOCKC612 and the inner and outer airlock doors for the Unit 2 upper airlock were satisfactorily tested.

Both the inner and outer airlock doors for the upper and lower Unit 1 airlocks were satisfactorily tested.

The individuals who failed to correctly seal dosed the outer door of 2-AIRLOCK-C612 were instructed on the proper method of dosing and verifying dosed the doors associated with 2-AIRLOCK-C612.

l&M issued a lessons learned (required reading) to all Maintenance personnel to alert them of the error and to refresh their knowledge of the proper operation of the airlock doors associated with 2-AIRLOCK-C612.

and Unit 2 to provide guidance on the proper operation of the airlock doors.

l&M has expanded the distribution of the lessons learned to include all Operations, Radiation Protection, and Engineering personnel.

l&M has provided copies of Lessons Learned #40 to the Work Control Center Senior Reactor Operator and incorporated them into the Unit 1 and Unit 2 Containment Entry Logbooks.

Action To Be Taken:

l&M will add the information contained in Lessons Learned #40 to the Indoctrination Training given to contractors as they come on site.

Previous Similar Events

None.