Semantic search

On June 30, 2003 at approximately 1545 (CDT) it was identified that a High Energy Line Break (HELB) door separating Divisional Motor Control Centers was not latched as required. It was determined that this condition existed for a maximum of 15 minutes. This condition is being reported as an event or condition that could have prevented the fulfillment of a safety function in accordance with 10 CFR 50.72(b)(3)(v). The licensee notified the NRC Resident Inspector and the State Emergency Management Agency.

• * *RETRACTION on 08/27/03 at 1215 EDT from R. Sand to John MacKinnon * * *

Because plant safety was not significantly degraded, this event is not reportable under the unanalyzed condition criteria based on: (1) the door in either event was in an uncontrolled condition for less than one minute, (2) the door was not materially affected, only operated improperly, (3) the PRA significance of the event was low, and (4) the HELB Barrier door was not open for a period than is allowed by station procedural guidance. R3DO (C. Miller) notified. The station continues to review the events in the station's corrective action program. The NRC Resident Inspector was notified of this retraction by the licensee.

Potential break of Fire Water Main in Admin Bldg could cause both divisions of Safe Shutdown equipment to be inoperable by flooding the battery rooms for #11 & 12 125VDC Batteries. Vulnerable section of piping has been isolated to eliminate the flooding concern. Fire Protection compensatory actions have been established in accordance with the site Fire Protection Program. The licensee informed the NRC resident inspector.

• * * RETRACTION FROM PFEFFER TO GOTT AT 1242 ON 11/7/03 * * *

Monticello is retracting the event reported based on evaluations which indicate that the fire main is not considered a potential flooding source. Additional evaluations are ongoing, and issues will be entered into the station's corrective action program. The licensee has notified the NRC Resident Inspector. Notified R3DO (Hills)

On 11/10/2003 at 07:20 CST it was discovered, during a control room panel walk-down, that Dresden U2 had primary containment valves 2-1601-56 Torus Purge valve and 2-1601-21 DW (drywell) Purge valve open simultaneously. This valve alignment created a flow path from the Drywell to the Torus, effectively bypassing the pressure suppression function of the torus water volume during a LOCA (Loss of Coolant Accident) condition. This condition placed U2 containment in an unanalyzed condition, not capable of performing the intended design function, which is to mitigate the consequences of a LOCA. The proper valve alignment was restored at 07:26 CST which restored U2 primary containment to operable status per TS (Tech. Spec) 3.6.1.1. A review of plant data identified that this valve arrangement, which bypassed primary containment, had been in effect when U2 entered Mode 2 (Startup) from Mode 4 (Cold Shutdown) at 12:01 on Nov 9, 2003. In addition, this valve line-up existed for a duration greater than that allowed by TS 3.6.1.1 A.1 and B.1 (1 hour). The NRC Resident Inspector was notified of this event by the licensee.

• • • • Retraction on 12/31/03 at 1430 EST by J. Welch taken by MacKinnon ****

Dresden has performed an engineering evaluation that bounds the plant conditions that existed while the two valves were simultaneously open. The evaluation concluded that the valves would have automatically closed in sufficient time to prevent exceeding the design limits of the primary containment during a postulated Design Basis Accident. Therefore, Dresden retract the ENS call associated with this event. This event will be the subject of an Licensee Event Report in accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), 'Any event or condition which was prohibited by the plant's Technical Specifications.'" R3DO (Ken Riemer) notified. The NRC Resident Inspector was notified of the above retraction by the Licensee.

At 1049 EST on January 14, 2004 the Control Room was notified that 78% (87 out of 112) Emergency Sirens failed a 'Quiet Test.' The Quiet test is a status check between the Emergency Offsite Facility and each individual siren. Further investigation revealed that 53 sirens would not operate as required and 34 were experiencing some degree of degradation. Indications point toward amplifier problems within each affected siren. Efforts are ongoing to troubleshoot and repair the effected sirens. Contingency plans are in place for alternate notification. The resident inspector has been notified. This condition was discovered during routine monthly testing. The sirens were upgraded about a year ago using equipment supplied by Federal Signal.

* * * UPDATE ON 1/20/04 AT 1422 EST FROM RANDY HAISLET TO GERRY WAIG * * *

The following was received via facsimile: This is a follow up to event report 40448 concerning a loss of 53 sirens. As of this morning, 105 of the 112 sirens are considered operable. Six of the 7 inoperable sirens are due to rotational problems. The remaining siren is inoperable due to the impact of a vehicle on it's pole. Work is currently on going to restore these sirens. The siren failures reported in event report are believed to be the result of a manufacturing defect which resulted in temperature sensitivity. A temporary means of heating the subject equipment has been put in place. Investigation is continuing. Notified R1DO (Clifford Anderson)

This report is being made in accordance with 10 CFR 50.72(b)(3)(v)(B). On 04/24/2004 at 06:03 (CDT), Dresden Unit 2 was using the Isolation Condenser to control reactor pressure following a Unit Scram. The isolation condenser operated properly until 10:50 (CDT) when the Isolation Condenser 2-1301-3 valve could not be opened to the full open position. ISO Condenser was declared INOPERABLE and Technical Specification Limiting Condition of Operation 3.5.3. Condition 'A' was ENTERED. High Pressure Coolant Injection has been administratively verified OPERABLE. Reactor Pressure is being maintained 550-1000 psig and being maintained with Reactor Water Clean Up Flow and Gland Seal System. Investigation into the cause of the valve failure is in-progress. Unit 2 had been operating approximately 30 days prior to the scram reported previously in EN #40702. The licensee informed the NRC Resident Inspector.

• * * RETRACTION ON 6/23/04 AT 2036 EDT FROM GLEN MORROW TO ARLON COSTA * * *

On April 24, 2004, Dresden made an ENS call due to the failure of Isolation Condenser valve 2-1301-3 to fully open and the subsequent determination that the Isolation Condenser was inoperable. The ENS call was made based on the decision that this was required by 10CFR50.72(b)(3)(v)(B), 'Any event or condition that at the time of discovery could have prevented fulfillment of the safety function of structures or systems that are needed to remove residual heat.' Isolation Condenser System operation is not credited in Dresden's accident analyses. Transients and Events treated as transients are listed under section 15.0.2.1 of the UFSAR. Accidents are described and analyzed under section 15.0.2.2 of the UFSAR. The isolation condenser is not credited for fulfilling safety function of removal of residual heat of any accident as described in section 15.0.2.2, Accidents. In accordance with the guidance contained in NUREG 1022, 'Event Reporting Guidelines 10CFR50.72 and 10CFR50.73,' Section 3.2.7, 'Event or Condition That Could Have Prevented Fulfillment of a Safety Function,' a functional failure of the Isolation Condenser System is not reportable under 10CFR50.72(b)(3)(v)(B). Therefore, Dresden is retracting this ENS call. This Isolation Condenser System event will be described in a Licensee Event Report in accordance with 10CFR50.73(a)(2)(i)(B), 'Any event or condition which was prohibited by the plant's Technical Specifications' The licensee notified the NRC Resident Inspector. Notified R3DO (Kozak).

The Station declared an Unusual Event (at 01:30 CDT) due to a felt earthquake and confirmation from other sites. The site seismic recorder did not register an event. No damage has been noted at this time. Inspections will continue. The licensee notified the NRC Resident Inspector and State authorities. NOTE: See related EN#40845 and EN#40846.

• * * UPDATE ON 06/28/04 @ 0726 BY RILEY RUFFIN TO C GOULD * * *

Plant walk downs were performed and no damage was observed during the walk downs. The UE was terminated at 0555 CDT. The licensee notified the NRC Resident Inspector, the State and local authorities. Notified by e-mail: Susan Frant (IRO), Thomas Kozak (R3 DO), Frank Gillespie (NRR EO), Pat Hiland (Reg3), and Geoffrey Grant (R3). Also notified FEMA (Erwin Casto) and DHS (Andy Akers).

On November 25, as of 1545 hours, the Station's Plant Process Computer (PPC) had been in a failed state for greater than eight hours. Previous to this, at 0745 hours, the PPC experienced an unexpected hardware failure. This computer feeds the Safety Parameter Display System (SPDS) for both Units. This failure is considered a major loss of emergency assessment capability. Troubleshooting and repairs are in progress. This failure affects the transmission of ERDS data and applicable emergency response personnel have been notified of the change in their reporting status if an emergency event is declared due to the loss of ERDS. The licensee notified the NRC Resident Inspector.

• * * UPDATE PROVIDED BY DARIN TO JEFF ROTTON AT 1205 EST ON 11/26/04 * * *

At 1040 CST on 11/26/04, Information Technology personnel restored the Station's PPC to the point where the SPDS and ERDS are both fully functional for both units. The licensee notified the NRC Resident Inspector.

The licensee provided via facsimile the following report:

During an extent of condition review of the corrective actions associated (with) Event Notification #41374, the Monticello Nuclear Generating Plant (MNGP) engineering staff made the following discovery.  On February 22, 2005 at 12:00 hours, MNGP discovered a potential vulnerability with Alternate Shutdown System (ASDS) isolation design which could result in Bus 16 being locked out in the event of a Control Room or Cable Spreading Room fire.  The Monticello Appendix R Safe Shutdown Analysis for Control Room/Cable Spreading Room fire assumes a loss of control of Division I and II equipment from the Control Room, however, safe shutdown is achieved remotely from the ASDS panel.  ASDS design is such that a Control Room/Cable Spreading Room fire would not impede the ability to safely shutdown and maintain the plant in a shutdown condition.  

Contrary to the ASDS design, it was discovered that an un-isolated metering circuit from the 1AR transformer could result in Bus 16 being locked out in the event of a Control Room or Cable Spreading Room fire. The bus lockout relay from the 1AR transformer is not isolated by the ASDS transfer switches, therefore, this condition could result in failure of Bus 16 to re-energize during the implementation of the Shutdown Outside Control Room procedure. Since the Bus 16 feeder breaker from the 1AR transformer is not required at this time, it has been isolated from the safeguards bus to preclude occurrences of this event. The event is being reported as a potential loss of safety function (10CFR50.72(b)(v)(A,B and D) and as a degraded or unanalyzed condition (10CFR50.72(b)(3)(ii)(B)). The licensee informed NRC Resident Inspector.

The following information was obtained from the licensee via facsimile (licensee text in quotes): Minimum Switchyard Voltage Requirements Not Met On March 24, 2005, at 0930 hours, Quad Cities was notified that the switchyard voltage was below that required to ensure that offsite power would remain available following a design basis accident. Both sources of off-site power were declared inoperable. The appropriate Technical Specification required actions were taken for both units. The ability of the Emergency Diesel Generators to perform their design function is not affected by this condition. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function given the predicted post-LOCA switchyard voltage. A preliminary engineering assessment indicates that one source of offsite power was available. Additional confirmatory reviews are being performed to determine if the safety function was preserved. At this time, grid/switchyard voltage has been restored. Minimum switchyard voltage required is 348.4 KV. The analyzed minimum voltage which prompted notification to the NRC was 347.5 KV. Switchyard voltage at the time of this report was ~359 KV. The licensee has notified the NRC Resident Inspector.

• * * RETRACTION FROM C. STEFFES TO M. RIPLEY 1556 EDT 04/13/05 * * *

The purpose of this report is to retract the following ENS reports: 1) ENS # 41524 on March 24, 2005; 2) ENS # 41562 on April 4, 2005; and 3) ENS # 41587 on April 11, 2005. These reports were made following notification to Quad Cities that the switchyard voltage was below the required value necessary to ensure that offsite power would remain available following a design basis accident. For each event, both sources of offsite power were declared inoperable, the appropriate Technical Specification required actions were taken for both units, and an ENS notification was made for a condition that could have prevented fulfillment of a safety function. The events occurred when Unit 1 was in a refueling outage and Unit 2 was operating at 85% power. Subsequent Engineering analysis has determined that with a unit shutdown, and the large 4 Kv loads on that unit not running, the required minimum post-accident switchyard voltage is reduced to 339.3 kV (for the shutdown unit). Given the new minimum post-accident switchyard voltage, it was confirmed that there was a source of off-site power available to the Station. Specifically for all three events, the projected post-accident switchyard voltage (which ranged between 343 kV to 347.5 kV) was higher than the required minimum post-accident switchyard voltage (339.3 kV) for the shutdown unit. As a result, there was no condition present that could have prevented fulfillment of a safety function, and thus these events are not reportable. The licensee notified the NRC Resident Inspector. Notified R3 DO (J. Madera)