An Unusual Event was declared at 1021
CST due to toxic, corrosive, flammable gasses in amounts that have or could adversely affect normal plant operations. Licensee estimated that a plume of
hydrogen gas 20 feet high was leaking in the Turbine Building at the North Generator Bearing. Licensee entered
EAL HU3.1. There was no release above normal operating limits (0.1 Mr/hr at EAB). No offsite response required. Gas is being dissipated via emergency degassing of Main Generator. Presently, the Main Generator degas has been completed and no flammable environments remain. The Unusual Event will stay in effect until the area is accessible to personnel, as evaluated by chemistry.
There was no fire or personnel injury related to this event. The Plant was already in Mode 3 due to an earlier event requiring a Technical Specification Action 3.3.2.Q shutdown.
The licensee has notified the NRC Resident Inspector, and local, state and other government agencies. No media press release was anticipated.
The hazard was eliminated by 1055 on 2/19/2008. The Unusual Event was closed out at 1115. The state and counties (Callaway, Gasconade, Montgomery, and Osage) were notified of the event closeout at 1126. A news release will be made by Ameren Corporate Communications.
The licensee has notified the NRC Resident Inspector. Notified R4DO (Powers),
DHS ( Cassandra McKentry) and
FEMA (Mike Eaches).
