This 60-day telephone notification is being made under reporting requirements specified by
10CFR50.73(a)(2)(iv)(A) to describe an invalid actuation of a containment isolation signal affecting more than one system.
At 2043 on April 14, 2011, with the Duane Arnold Energy Center (DAEC) operating at 100% power, an invalid Group 3 isolation on the 'A' side of the Primary Containment Isolation System occurred. Group 3 isolation signals were generated for Primary Containment Isolation Valves for Drywell and Torus Ventilation, and Purge, Containment Nitrogen Compressor Suction and Discharge, Recirculation Pump Seals, and Post Accident Sample System.
This event was caused by a high resistance contact on connectors in the detector circuitry for the 'A' Reactor Building Vent Shaft Radiation Monitor.
All equipment responded in accordance with the plant design. Specifically, all actuations were complete and successful.
There were no safety consequences or impacts on the health and safety of the public. The event was entered into DAEC's corrective action program for resolution.
The licensee notified the NRC Resident Inspector.
