4-7-2017 | On February 8, 2017, at 1151 EST with Unit 1 at approximately 100 percent rated thermal power, the High Pressure Coolant Injection ( HPCI) suction and discharge pressure indicators were noted to be downscale during a main control room panel walk down. Upon further investigation, it was discovered that the output voltage of the DC to AC inverter was degraded. The HPCI DC to AC inverter supplies power to the HPCI flow controller and power supply. HPCI was therefore declared inoperable due to the degraded voltage condition.
The inoperable as found condition of the HPCI pressure indicators was due to degraded output voltage from the DC to AC HPCI inverter. The degraded inverter was removed and replaced and HPCI was returned to operable status. As part of an extent of condition review, the internals of the degraded inverter were inspected to determine what caused premature failure of the inverter. Based on the findings of this inspection, the preventative maintenance frequency for inverter replacement and calibration will be adjusted as necessary. |
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Category:Letter
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[Table view] Category:Licensee Event Report (LER)
MONTHYEARNL-20-0230, Edwin I. Hatch Nuclear Plant, Unit 2, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)2020-03-0202 March 2020 Edwin I. Hatch Nuclear Plant, Unit 2, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La) 05000366/LER-2020-0012020-03-0202 March 2020 LER 2020-001-00 for Edwin I. Hatch Nuclear Plant, Unit 2, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La) 05000321/LER-2017-0042017-08-24024 August 2017 Tornado Missile Vulnerabilities Result in Condition Prohibited by Technical Specifications, LER 17-004-00 for Edwin I. Hatch Regarding Safety Relief Valves' as Found Settings Resulted in Not Meeting Tech Spec Surveillance Criteria 05000366/LER-2017-0022017-04-13013 April 2017 Emergency Diesel Generator Start Due to Inadvertent Electrical Bus De-Energization, LER 17-002-00 for Edwin I. Hatch, Unit 2, Regarding Emergency Diesel Generator Start Due to Inadvertent Electrical Bus De-Energization 05000366/LER-2017-0032017-04-13013 April 2017 LER 17-003-00 for Edwin I. Hatch, Unit 2, Regarding Primary Containment Isolation Penetration Exceeded Overall Allowable Technical Specification Leakage Limits 05000321/LER-2017-0022017-04-0707 April 2017 High Pressure Coolant Injection System Declared Inoperable Due to Degraded Inverter, LER 17-002-00 for Edwin I. Hatch, Unit 1, Regarding High Pressure Coolant Injection System Declared Inoperable Due to Degraded Inverter 05000366/LER-2016-0042017-01-0303 January 2017 Condition Prohibited by Technical Specifications Due to Inoperable PCIV, LER 16-004-00 for Edwin I. Hatch Nuclear Plant, Unit 2, Regarding Condition Prohibited by Technical Specifications Due to Inoperable PCIV 05000366/LER-2016-0022016-07-13013 July 2016 Group I Isolation Received During Turbine Testing, LER 16-002-00 for Edwin I. Hatch, Unit 2, Regarding Group 1 Isolation Received During Turbine Testing 05000366/LER-2016-0012016-06-0808 June 2016 2C EDG Fuel Oil Relief Valve Leakage Caused Train Inoperability, LER 16-001-00 for E.I. Hatch, Unit 2, Regarding 2C EDG Fuel Oil Relief Valve Leakage Caused Train Inoperability 05000321/LER-2016-0042016-05-26026 May 2016 Safety Relief Valves As Found Settings Resulted in Not Meeting Tech Spec Surveillance Criteria, LER 16-004-00 for Edwin I. Hatch Nuclear Plant Unit 1 RE: Safety Relief Valves as Found Settings Resulted in Not Meeting Tech Spec Surveillance Criteria 05000321/LER-2016-0032016-04-14014 April 2016 Reactor Coolant System Piping Has Unacceptable Weld Indication Discovered During Refueling Outage, LER 16-003-00 for E.I. Hatch, Unit 1, Regarding Reactor Coolant System Piping Has Unacceptable Weld Indication Discovered During Refueling Outage 05000321/LER-2016-0022016-04-11011 April 2016 Performance of Operations With the Potential to Drain the Reactor Vessel (OPDRV) Without Secondary Containment, LER 16-002-00 for E.I Hatch, Unit 1, Regarding Performance of Operations With the Potential to Drain the Reactor Vessel (OPDRV) Without Secondary Containment 05000321/LER-2016-0012016-04-0808 April 2016 Performance of Fuel Movement with Inoperable Rod Position Indication System in Violation of Technical Specifications, LER 16-001-00 for Edwin I. Hatch, Unit 1, Regarding Performance of Fuel Movement With Inoperable Rod Position Indication System in Violation of Technical Specifications NL-08-1906, LER 08-S01-00, for Edwin I. Hatch, Failure to Report Arrest Results in Inappropriate Access to Protected and Vital Areas2008-12-19019 December 2008 LER 08-S01-00, for Edwin I. Hatch, Failure to Report Arrest Results in Inappropriate Access to Protected and Vital Areas ML1019404552008-05-0808 May 2008 Southern Nuclear Plant E. I. Hatch - Actions for Potential Groundwater Contamination Events NL-06-2726, LER 06-S01-00 for Edwin I. Hatch Nuclear Plant, Re Contract Employee Failure to Self-Disclose Material Information for Unescorted Access2006-12-0505 December 2006 LER 06-S01-00 for Edwin I. Hatch Nuclear Plant, Re Contract Employee Failure to Self-Disclose Material Information for Unescorted Access ML17252B4401976-04-15015 April 1976 LER 76-026-00 for Hatch, Unit 1 Regarding an Occurrence of Open Links in Panel H11-P601 Defeating the Starting of All RHR Pumps After They Had Been Stopped 2020-03-02
[Table view] |
Reported lessons learned are incorporated into the licensing process and fed back to industry Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001. or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regu atory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
3 LER NUMBER Edwin I. Hatch Nuclear Plant Unit 1 05000-321
Event Description
On February 8, 2017, at 1151 EST with Unit 1 at approximately 100 percent rated thermal power, the High Pressure Coolant Injection (HPCI) suction and discharge pressure indicators were noted to be downscale during a main control room panel walk down. Upon further investigation, it was discovered that the output voltage of the DC to AC inverter (EIIS Code INVT) was degraded. This inverter provides power to multiple HPCI control room indications as well as to the HPCI flow controller and power supply. HPCI was therefore declared inoperable.
Failed Components Information:
Master Parts List Number: 1E41K603 Manufacturer: Abacus Controls Inc.
Model Number: 452-4-120M9 Type: Inverter Event Cause Analysis The cause of the event is due to degradation of the output voltage of the DC to AC inverter. The HPCI DC to AC inverter supplies power to the HPCI flow controller and power supply. The flow controller maintains constant flow over the pressure range of HPCI system operation and automatically starts if HPCI system initiation is required. The power supply provides DC control power to the HPCI Turbine Speed Control logic.
Without the flow controller and the power supply, the HPCI Turbine would not be able to run if called upon, causing HPCI to be declared inoperable.
Safety Assessment This event is reportable per 10 CFR 50.73(a)(2)(v)(D) due to an event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident.
The HPCI system is a single train system designed to permit the unit to be shut down while maintaining sufficient reactor pressure vessel (RPV) water inventory. The system continues to operate until the RPV is below the pressure at which either operation of the Low Pressure Coolant Injection (LPCI) mode of the Residual Heat Removal or the Core Spray (CS) system will maintain core cooling. The HPCI system consists of a steam turbine that drives a constant flow pump, system piping, valves, controls, and instrumentation. Upon receipt of an initiation signal, the HPCI turbine stop valve and turbine control valve open simultaneously. The HPCI turbine then accelerates to a specified speed to provide necessary pump flow.
Upon a "small" or "intermediate" break resulting in a loss of coolant accident (LOCA), HPCI provides sufficient inventory to prevent the core from being uncovered. It performs a dual function by providing makeup water to the reactor pressure vessel (RPV) as well as supplementing the break in depressurizing the RPV. If HPCI is unavailable, the Automatic Depressurization System (ADS) is credited to depressurize Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
05000-321 a LER NUMBER the RPV to enable operation of the low pressure Emergency Core Cooling Systems (ECCS) (i.e., CS and LPCI). The Reactor Core Isolation Cooling (RCIC) system is also available to restore and maintain water level in the event HPCI is inoperable.
Although HPCI was declared inoperable, ADS, CS, LPCI, and RCIC were operable to provide core cooling in the event of a small or immediate break LOCA or a design basis accident (DBA) LOCA. Therefore, based on the ability of the station to mitigate the consequences of a potential loss of the HPCI system combined with a LOCA, this event is considered to have very low safety significance.
Corrective Actions
The degraded inverter was removed and replaced to return HPCI to operable status. As part of an extent of condition review, the internals of the degraded inverter were inspected to determine what caused premature failure of the inverter. Based on the findings of this inspection, the preventative maintenance frequency for inverter replacement and calibration will be adjusted as necessary.
Previous Similar Events
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05000366/LER-2017-001 | 1 OF 3 | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000366/LER-2017-002 | Emergency Diesel Generator Start Due to Inadvertent Electrical Bus De-Energization LER 17-002-00 for Edwin I. Hatch, Unit 2, Regarding Emergency Diesel Generator Start Due to Inadvertent Electrical Bus De-Energization | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000321/LER-2017-002 | High Pressure Coolant Injection System Declared Inoperable Due to Degraded Inverter LER 17-002-00 for Edwin I. Hatch, Unit 1, Regarding High Pressure Coolant Injection System Declared Inoperable Due to Degraded Inverter | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 05000366/LER-2017-003 | LER 17-003-00 for Edwin I. Hatch, Unit 2, Regarding Primary Containment Isolation Penetration Exceeded Overall Allowable Technical Specification Leakage Limits | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded | 05000321/LER-2017-004 | Tornado Missile Vulnerabilities Result in Condition Prohibited by Technical Specifications LER 17-004-00 for Edwin I. Hatch Regarding Safety Relief Valves' as Found Settings Resulted in Not Meeting Tech Spec Surveillance Criteria | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
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