05000331/LER-2005-002

LER-2005-002,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
Initial Reporting
ENS 41785	10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
3312005002R00 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Duane Arnold Energy Center 05000331 YEAR NUMBER�NUMBER

I. Description of Event:

On June 20, 2005, with the plant operating at 96% power in Mode 1, during the performance of the monthly 10-hour testing of the 'B' Standby Gas Treatment (SBGT) train, it was discovered that the flow-indicating controller was not controlling flow at the required setpoint. As a result, the 'B' SBGT train was declared inoperable at 0308 on June 20, 2005. As part of this testing, the 'A' SBGT train Mode Select switch wasin Manualmith..the inlet.damper_closed_rendering the�-- SBGT train inoperable. During the short period of time (approximately 4 minutes) between the discovery of the 'B' SBGT controller failure and the return of the 'A' SBGT train to an operable condition, both SBGT trains were inoperable which is a condition that could prevent the fulfillment of the safety function of the SBGT system to control the release of radioactive material.

The 'A' SBGT train was restored to operable status at 0312 on June 20, 2005 when its inlet damper was reopened and its Mode Select switch was returned to AUTO per the surveillance test.

II. Assessment of Safety Consequences:

A 10CFR50.72(b)(3)(v)(C), "Control the release of radioactive material" notification was made on June 20, 2005 and is listed as event number EN 41785. This report is being submitted pursuant to 10CFR50.73(a)(2)(v)(C).

This event did not affect the availability of other systems needed to maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident.

Therefore, there were no actual safety consequences associated with this event. There was no effect on public health and safety as a result of this event.

This event resulted in a Safety Systern_Functional Failure of SBGT._�_

III. Cause of Event:

The cause of this event was the failure of a capacitor in the 'B' SBGT flow controller.

IV. Corrective Actions:

The 'A' SBGT train was restored to operable status at 0312 on June 20, 2005 when its inlet damper was reopened and its Mode Select switch was returned to AUTO per the surveillance test.

The failed capacitor in the 'B' SBGT flow controller was replaced on June 20, 2005.

CA 40481 is tracking the replacement of both the 'A' and 'B' SBGT flow controllers with a newer, more reliable model. This action is scheduled to be completed by March 31, 2006.

FACILITY NAME (1)�

• DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Duane Arnold Energy Center 05000331 YEAR EIIS System and Component Codes:

BH — Emergency/Standby Gat Treatment System.

V. Additional Information:

._Previous Similar Occurrences:

A review of LERs at the DAEC over the last 3 years identified no LERs with similar causes.