ENS 41649
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.
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.
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) }}| ]] |
| 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
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 480302012-04-23T00:58:00023 April 2012 00:58:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Keowee Hydro Power Station Automatically Started Based on an Invalid Signal ENS 465442010-11-18T07:45:00018 November 2010 07:45:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Motor Driven Emergency Feedwater System ENS 451802009-05-19T20:09:00019 May 2009 20:09:00 10 CFR 50.73(a)(1), Submit an LER Invalid Feedwater System Actuation While Shutdown ENS 431462006-12-09T02:43:0009 December 2006 02:43:00 10 CFR 50.73(a)(1), Submit an LER Invalid Efw Actuations Due to an Issue in Sg Dryout Protection Circuit ENS 416492005-04-29T05:05:00029 April 2005 05:05:00 10 CFR 50.73(a)(1), Submit an LER Emergency Hydro Generators Auto Start - Unknown Cause ENS 406862004-03-20T19:59:00020 March 2004 19:59:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of the Motor Driven Emergency Feedwater Pumps 2012-04-23T00:58:00 | |