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Event Notification Report for September 11, 2006

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
09/08/2006 - 09/11/2006

** EVENT NUMBERS **

Power Reactor	Event Number: 42835
Facility: DUANE ARNOLD Region: 3 State: IA Unit: [1] [ ] [ ] RX Type: [1] GE-4 NRC Notified By: ELLIS VANN HQ OPS Officer: MARK ABRAMOVITZ	Notification Date: 09/08/2006 Notification Time: 10:30 [ET] Event Date: 09/08/2006 Event Time: 04:01 [CDT] Last Update Date: 09/08/2006
Emergency Class: NON EMERGENCY 10 CFR Section: 50.72(b)(3)(v)(D) - ACCIDENT MITIGATION	Person (Organization): BRUCE BURGESS (R3)

Unit	SCRAM Code	RX CRIT	Initial PWR	Initial RX Mode	Current PWR	Current RX Mode
1	N	Y	96	Power Operation	96	Power Operation

Event Text

CONTAINMENT ATMOSPHERIC DILUTION (CAD) SYSTEM INOPERABLE

"On September 8, 2006 at 04:01, DAEC declared CAD inoperable after determining SV-4332B, UPPER DRYWELL SPRAY CAD N2 OUTBOARD ISOLATION was inoperable while SV-4331B, LOWER DRYWELL SPRAY CAD N2 OUTBOARD ISOLATION was also inoperable. Actions to isolate both of these injection pathways as required by Technical Specifications made CAD injection into the Drywell unavailable. Day 1 of a 7 day LCO for Technical Specification 3.6.3.1 Condition A was entered. Per DAEC Technical Specifications bases, CAD is considered to be inoperable when both injection pathways into either the drywell or torus are not available. Since CAD is a single train safety system, this event is reportable as an 8 hour non-emergency event under 50.72(b)(3)(v)(D), any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident."

The licensee notified the NRC Resident Inspector.

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