ENS 41649

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v t e ENS Event
05:05 Apr 29, 2005
Title	Emergency Hydro Generators Auto Start - Unknown Cause
Event Description	{{#Wiki_filter:Event: At 01:05 on 4-29-05, Oconee Nuclear Station received an Emergency Start of both Keowee Hydro Unit emergency power sources. An investigation is in progress to determine the cause of the system actuation. Plant conditions currently do not indicate the need for actuation of the Keowee Hydro Unit emergency power sources. However, this system actuation is being conservatively reported until it can be positively determined whether a valid actuation occurred. Initial Safety Significance: Units 2 and 3 remain at 100% power with no issues following the Keowee Hydro Unit emergency start. Unit 1 remains in Mode 5 (refueling outage). No units were affected by the safety system actuation. Plant conditions currently do not indicate the need for actuation of the Keowee Hydro Unit emergency power sources. No other safety systems actuated or exhibited abnormal behavior. Therefore, the safety significance of this condition is LOW. At the time of this notification, the Keowee units were still running unloaded. The licensee notified the NRC Resident Inspector. * * UPDATE FROM L. GENTRY TO M. RIPLEY 0958 EDT 06/16/05 * * * This report is being made under � 50.73(a)(2)(iv)(A) INVALID SPECIFIC SYSTEM ACTUATION At 1:05 AM on 4/29/05 an unplanned emergency start of both Keowee Hydro Units occurred. These units are specifically called out in � 50.73(a)(2)(iv) (B) (8) as " hydroelectric facilities used in lieu of EDGs at the Oconee Station." Each Keowee Hydro Unit can supply emergency power to the three Oconee Units via either of two emergency power paths (Overhead path or Underground path). This event was initially reported as: - 50.72(b)(3)(iv)(A) - VALID SPECIFIC SYSTEM ACTUATION - Event Number: 41649 - Notification Date: 04/29/2005 - Notification Time: 05:22 [ET] - Event Date: 04/29/2005 - Event Time: 01:05 [EDT] Unit status as stated in that notification: - Unit 1: 0% RP, Mode 5 for a refueling outage - Unit 2: 100% RP, Mode 1 - Unit 3: 100% RP, Mode 1 Keowee Emergency Start Channel A actuated. By design, each Emergency Start Channel starts both Keowee Hydro Unit 1 and 2. Both Keowee units did respond and came to rated speed and voltage. It was determined from the alarms received and from direct visual inspection that the signal for the Keowee Units to emergency start came from the actuation of the KA relay located in Emergency Start Channel A cabinet. Investigation and troubleshooting of this event was unable to identify the actual cause of the actuation of relay KA. The investigation confirmed that no valid condition existed which would or should have resulted in an automatic signal and there is no evidence of intentional or unintentional actuation using manual actuation switches. Therefore the actuation is determined to be 'invalid'. At the time of the event, Oconee Unit 1 was in an outage and a routine Engineered Safeguard Actuation System (ES) Channel 2 surveillance test was in progress. By design ES Channel 2 initiates Keowee Emergency Start Channel B, so DC control power was removed from Keowee Emergency Start Channel B during that test to prevent an unnecessary Keowee Emergency Start signal. Troubleshooting confirmed that the start which occurred was not due to this test in progress. However, the test affected the event slightly in that ES channel 2 also provides a permissive signal which allows Breaker SK-2 to close to connect the underground path to Standby Bus 2. Following the unintentional start, breaker SK-2 closed as designed, which energized Standby Bus 2, as soon as the Keowee Unit connected to the Underground Path achieved adequate voltage. Because there was no actual loss of power on any of the Oconee Units, there was no demand signal to connect Standby Bus 2 to any unit's Main Feeder Bus. 50.73(a)(2)(iv)(A) requires the following information: (a) The specific train(s) and system(s) that were actuated - Keowee Emergency Start Channel A actuated. By design, each Emergency Start Channel starts both Keowee Hydro Unit 1 and 2. Both Keowee units responded and came to rated speed and voltage. Each Keowee Hydro Unit can supply emergency power to the three Oconee Units via either of two emergency power paths (Overhead path or Underground path). They are aligned so that one unit will supply the overhead path and the other unit will supply the underground path. (b) Whether each train actuation was complete or partial - Other systems, such as the Emergency Power Switching Logic system, must also actuate to automatically connect an emergency power path to a Main Feeder Bus and power Oconee loads. Since this was not a valid event, conditions did not require connection of emergency power to any loads. No complete power train/path alignment was established, therefore the actuation was considered partial. (c) Whether or not the system started and functioned successfully - The Keowee Hydro Units both started and functioned successfully. As stated above, due to the existence of a signal during an unrelated test, one additional component, breaker SK2, was challenged and operated as designed. Therefore, all challenged components functioned successfully. The licensee notified the NRC Resident Inspector. Revised the 10 CFR Section designation in the report header according to the update, and notified R2 DO (T. Decker) }}[[Event description::Description::{{#Regex_clear:Event: At 01:05 on 4-29-05, Oconee Nuclear Station received an Emergency Start of both Keowee Hydro Unit emergency power sources. An investigation is in progress to determine the cause of the system actuation. Plant conditions currently do not indicate the need for actuation of the Keowee Hydro Unit emergency power sources. However, this system actuation is being conservatively reported until it can be positively determined whether a valid actuation occurred. Initial Safety Significance: Units 2 and 3 remain at 100% power with no issues following the Keowee Hydro Unit emergency start. Unit 1 remains in Mode 5 (refueling outage). No units were affected by the safety system actuation. Plant conditions currently do not indicate the need for actuation of the Keowee Hydro Unit emergency power sources. No other safety systems actuated or exhibited abnormal behavior. Therefore, the safety significance of this condition is LOW. At the time of this notification, the Keowee units were still running unloaded. The licensee notified the NRC Resident Inspector. * * UPDATE FROM L. GENTRY TO M. RIPLEY 0958 EDT 06/16/05 * * * This report is being made under � 50.73(a)(2)(iv)(A) INVALID SPECIFIC SYSTEM ACTUATION At 1:05 AM on 4/29/05 an unplanned emergency start of both Keowee Hydro Units occurred. These units are specifically called out in � 50.73(a)(2)(iv) (B) (8) as " hydroelectric facilities used in lieu of EDGs at the Oconee Station." Each Keowee Hydro Unit can supply emergency power to the three Oconee Units via either of two emergency power paths (Overhead path or Underground path). This event was initially reported as: - 50.72(b)(3)(iv)(A) - VALID SPECIFIC SYSTEM ACTUATION - Event Number: 41649 - Notification Date: 04/29/2005 - Notification Time: 05:22 [ET] - Event Date: 04/29/2005 - Event Time: 01:05 [EDT] Unit status as stated in that notification: - Unit 1: 0% RP, Mode 5 for a refueling outage - Unit 2: 100% RP, Mode 1 - Unit 3: 100% RP, Mode 1 Keowee Emergency Start Channel A actuated. By design, each Emergency Start Channel starts both Keowee Hydro Unit 1 and 2. Both Keowee units did respond and came to rated speed and voltage. It was determined from the alarms received and from direct visual inspection that the signal for the Keowee Units to emergency start came from the actuation of the KA relay located in Emergency Start Channel A cabinet. Investigation and troubleshooting of this event was unable to identify the actual cause of the actuation of relay KA. The investigation confirmed that no valid condition existed which would or should have resulted in an automatic signal and there is no evidence of intentional or unintentional actuation using manual actuation switches. Therefore the actuation is determined to be 'invalid'. At the time of the event, Oconee Unit 1 was in an outage and a routine Engineered Safeguard Actuation System (ES) Channel 2 surveillance test was in progress. By design ES Channel 2 initiates Keowee Emergency Start Channel B, so DC control power was removed from Keowee Emergency Start Channel B during that test to prevent an unnecessary Keowee Emergency Start signal. Troubleshooting confirmed that the start which occurred was not due to this test in progress. However, the test affected the event slightly in that ES channel 2 also provides a permissive signal which allows Breaker SK-2 to close to connect the underground path to Standby Bus 2. Following the unintentional start, breaker SK-2 closed as designed, which energized Standby Bus 2, as soon as the Keowee Unit connected to the Underground Path achieved adequate voltage. Because there was no actual loss of power on any of the Oconee Units, there was no demand signal to connect Standby Bus 2 to any unit's Main Feeder Bus. 50.73(a)(2)(iv)(A) requires the following information: (a) The specific train(s) and system(s) that were actuated - Keowee Emergency Start Channel A actuated. By design, each Emergency Start Channel starts both Keowee Hydro Unit 1 and 2. Both Keowee units responded and came to rated speed and voltage. Each Keowee Hydro Unit can supply emergency power to the three Oconee Units via either of two emergency power paths (Overhead path or Underground path). They are aligned so that one unit will supply the overhead path and the other unit will supply the underground path. (b) Whether each train actuation was complete or partial - Other systems, such as the Emergency Power Switching Logic system, must also actuate to automatically connect an emergency power path to a Main Feeder Bus and power Oconee loads. Since this was not a valid event, conditions did not require connection of emergency power to any loads. No complete power train/path alignment was established, therefore the actuation was considered partial. (c) Whether or not the system started and functioned successfully - The Keowee Hydro Units both started and functioned successfully. As stated above, due to the existence of a signal during an unrelated test, one additional component, breaker SK2, was challenged and operated as designed. Therefore, all challenged components functioned successfully. The licensee notified the NRC Resident Inspector. Revised the 10 CFR Section designation in the report header according to the update, and notified R2 DO (T. Decker) }}\| ]]

ENS 41649 +/-
Where
Oconee South Carolina (NRC Region 2)
Reporting

10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
Time - Person (Reporting Time:+0.28 h0.0117 days <br />0.00167 weeks <br />3.83544e-4 months <br />)
Opened:	David Nix 05:22 Apr 29, 2005
NRC Officer:	Mark Abramovitz
Last Updated:	Jun 16, 2005
41649 - NRC Website
v • d • e

v t e Emergency Notification System
Oconee with 10 CFR 50.73(a)(1), Submit an LER
WEEKMONTHYEAR2012-04-23T00:58:00 [Table view]
[ENS list for Oconee]

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