Event Notification Report for June 16, 2010

LOSS OF EMERGENCY SIRENS

"On June 16, 2010, at approximately 1015 hours (CDT), the Monticello Nuclear Generating plant determined that there was a loss of 48 out of 106 Emergency Preparedness sirens. No counties other than Sherburne County were affected. Availability of less than 70% of the total number of sirens is considered to be a loss of emergency off-site response capability and is reportable under 10 CFR 50.72(b)(3)(xiii), 'Loss of Emergency Preparedness Capabilities.' Notification to the public in the event of an emergency has not been compromised since a back-up notification method is provided in the station's Emergency Plan. At this time there is no estimated return to service time for the sirens.

"The station is working on restoration of the sirens. A follow-up notification of the return to service of the sirens will be provided once the issue is corrected.

"Sherburne County, the State of Minnesota, and the NRC Resident [Inspectors] have been informed of this event.

"Updated Information:

"At 1320 hours on June 16, 2010, sirens have been returned to service. Siren activation capability has been restored via the secondary method of activation. Investigation and repair of the primary method of siren activation continues."

OFFSITE NOTIFICATION TO THE NEBRASKA DEPARTMENT OF ENVIRONMENTAL QUALITY

"Notification was made to the Nebraska Department of Environmental Quality regarding the inability to conform to the NPDES permit, since the discharges from the sludge pond to the Missouri River are uncontrolled at this time. As a result of high Missouri River levels, the sludge pond was overtopped. The discharges into this pond are subject to NPDES Requirements. The inputs into the sludge pond are described in the NPDES permit as low volume wastewater. There are three outfalls which discharge into the pond. Outfall 002B is described as Clearwell Discharge plus Outfall 004 Emergency Overflow. Outfall 002C is described as Floor Drains. Outfall 004 is described as Reverse Osmosis Reject and Boiler Blowdown Waste streams.

"Additionally, the high river levels have resulted in media inquiries regarding potential changes in plant operation. Public information personnel and management have responded to these inquiries with information on the impact of river level and preparations for additional actions should conditions warrant additional protective actions. The responses to these inquiries have been referenced in some publications. At the present time, the river appears to be at its crest, with no additional rise forecast. The current level is approximately 3.8 feet below the crest of the 1993 flood, which was the highest flood recorded at the site, and 5 feet below grade elevation. A press release is not planned at this time."

The sludge pond does not contain any contaminated material.

The licensee will notify the NRC Resident Inspector.

MANUAL REACTOR TRIP AFTER TWO CONTROL RODS DROPPED

"At 1710 EDT, Unit 1 was manually tripped due to two dropped control rods. All CEAs [Control Element Assemblies] fully inserted on the trip. Steam generator level control responded as expected and no pressurizer or power operated relief valves opened. RCS heat removal is being maintained by main feedwater and steam bypass control systems. All other systems functioned normally and the plant has stabilized at normal operating temperature and pressure in Mode 3. This non-emergency notification is being made pursuant 10 CFR 50.72(b)(2)(iv)(B) due to manual actuation of RPS."

The licensee characterized the manual trip as uncomplicated. The second rod dropped within a very short time of the first rod. The cause of the rod drops is still under investigation. The licensee noted that no activities involving the rod control system were in progress when the event occurred. The licensee was at 45% as part of its post outage power ascension unrelated to the rod drop. The manual reactor trip action was taken per procedure when the second rod dropped. The reactor trip had no impact on Unit 2 operation.

The NRC Resident Inspector has been notified.

HIGH PRESSURE COOLANT INJECTION INOPERABLE

"On 06/16/10 at 1320 CDT, while performing 2-SR-3.3.6.1.6(3), HPCI Time Delay Relay Calibration, HPCI was discovered to be isolated. After review of the Integrated Computer System (ICS), HPCI [steam supply valve] had isolated at 1258 CDT. Cause of isolation is unknown with investigation in progress.

"This incident is reportable as an 8-hour ENS notification under 10CFR 50.72 (b)(3)(v) as '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.'

"It also requires a 60 day written report. The NRC Resident Inspector has been notified."

AUTOMATIC REACTOR TRIP DUE TO A LIGHTNING STORM

"On 6-16-2010 at 1920 hours, Unit 2 experienced an automatic reactor trip/turbine trip from 98% power. A severe lightning storm was in progress at the time of the trip and a lightning strike appears to be the cause of the event. The reactor trip was actuated from Channel 1 and Channel 2 Over Temperature Delta T. All control rods fully inserted into the core during the trip. The control room staff responded to the trip in accordance with plant procedures and the unit is stable in Mode 3. This event is reportable per 10CFR50.72(b)(2)(iv)(B).

"The Auxiliary Feedwater pumps started as designed following the reactor trip and steam generator inventory was restored to normal operating level. The Auxiliary Feedwater pumps have been secured and returned to automatic. This event is reportable per 10CFR50.72(b)(3)(iv)(A) due to the ESF actuation.

"Decay heat is being removed by the condenser steam dump system. The 'A' loop wide range hot and cold leg thermocouples remain failed high and the 'B' loop wide range cold leg thermocouple also failed high during the event. The plant is in a normal shutdown electrical lineup."

The licensee has notified the NRC Resident Inspector and will notify the local authorities. See EN #41898 for similar occurrence.

EARLY WARNING SYSTEM FOUND NON-RESPONSIVE DURING TESTING

"During performance of the Early Warning System (EWS) Polling Function Test the sirens did not respond. At 0859 hours [EDT] on June 16, 2010, the polling function test of the sirens was started. After four (4) sirens did not respond to the polling, the test was suspended and the Telecommunications group was notified. With Telecommunications monitoring the EWS primary base radio, the polling function test was run again. It was determined the audio signals from the status logger were being transmitted to the EWS primary base radio, however, the radio was not keying or transmitting the audio signal to the sirens. A check of the keying signal from the processor to the primary base radio was noted to be operating properly, however, the primary base radio was still not transmitting the audio signal to the sirens. Therefore, activation of the EWS by the state or local agencies would not have been possible. At 0925 hours, the EWS was switched to the back-up radio base station and tested satisfactory for proper radio function. The polling function test was performed with all 68 sirens responding as designed. All 68 sirens polled satisfactory during the last performance of the EWS Polling Function Test on June 2, 2010."

The licensee has notified the State and the NRC Resident Inspector. Local agencies will also be informed.