05000313/LER-2013-001, Regarding Collapse of a Main Generator Stator Temporary Lift Assembly Results in a Fatality, Multiple Injuries, a Plant Scram, a Notification of Unusual Event, and Dual Unit Structural Damage
| ML13144A220 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/24/2013 |
| From: | Jeremy G. Browning Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 0CAN051303 LER 13-001-00 | |
| Download: ML13144A220 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(b)(5) |
| 3132013001R00 - NRC Website | |
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0CAN051303 May 24, 2013 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report 50-313/2013-001-00 Unit-1 Main Generator Stator Temporary Lift Assembly Failure Arkansas Nuclear One Unit 1 and Unit 2 Docket Numbers 50-313 and 50-368 License Numbers DPR-51 and NPF-6
Dear Sir or Madam:
Pursuant to the reporting criteria of 10CFR 50.73, attached is the subject Licensee Event Report (LER) concerning the collapse of a temporary lift assembly while removing the Arkansas Nuclear One (ANO) Unit 1 Main Generator Stator. This report will address the reporting requirements for both ANO Unit 1 and Unit 2, and satisfies the requirements for a written report within sixty (60) days of a reportable occurrence. Event investigation and cause determination activities for this event are on-going at this time. Therefore, additional information required by 10CFR 50.73 will be provided in a supplemental report, tentatively expected by September 15, 2013.
This document contains a new regulatory commitment which is identified in attachment 2.
Should you have any questions concerning this issue, please contact Stephenie Pyle, Licensing Manager, at 479-858-4704.
Sincerely, Original signed by Mike Chisum for Jeremy Browning JGB/slc
- Licensee Event Report 50-313/2013-001-00 : List of Regulatory Commitments 10CFR 50.73 Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Jeremy G. Browning Site Vice President Arkansas Nuclear One
0CAN051303 Page 2 of 2 cc:
Mr. Arthur T. Howell Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 LEREvents@inpo.org
NRC FORM 366 (10-2010)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Arkansas Nuclear One - Unit 1
- 2. DOCKET NUMBER 05000313
- 3. PAGE 1 OF 4
- 4. TITLE Collapse of a Main Generator Stator Temporary Lift Assembly Results in a Fatality, Multiple Injuries, a Plant Scram, a Notification of Unusual Event, and Dual Unit Structural Damage
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME Arkansas Nuclear One-Unit 2 DOCKET NUMBER 05000368 03 31 2013 2013
- - 001 -
00 05 24 2013 FACILITY NAME DOCKET NUMBER
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
- 9. OPERATING MODE 6
- 10. POWER LEVEL 0
20.2201(b) 20.2201(d) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(2)(v) 20.2203(a)(2)(vi) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 20.2203(a)(4) 50.36(c)(1)(i)(A) 50.36(c)(1)(ii)(A) 50.36(c)(2) 50.46(a)(3)(ii) 50.73(a)(2)(i)(A) 50.73(a)(2)(i)(B) 50.73(a)(2)(i)(C) 50.73(a)(2)(ii)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(iii) 50.73(a)(2)(iv)(A) 50.73(a)(2)(v)(A) 50.73(a)(2)(v)(B) 50.73(a)(2)(v)(C) 50.73(a)(2)(v)(D) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x) 73.71(a)(4) 73.71(a)(5)
OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME Stephenie L. Pyle, Licensing Manager TELEPHONE NUMBER (Include Area Code) 479-858-4704 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
CAUSE
SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX NA NA NA NA NA MONTH DAY YEAR
- 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO
- 15. EXPECTED SUBMISSION DATE 09 15 2013 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On March 31, 2013, at approximately 0750 CDT, during lifting and removal of the Arkansas Nuclear One Unit 1 (ANO-1) original Main Generator Stator, the temporary lift assembly collapsed, resulting in the Stator falling onto the turbine deck (386' elevation) and rolling down into the ANO-1 train bay (354' elevation) adjacent to Arkansas Nuclear One Unit 2 (ANO-2). The event resulted in one fatality and multiple injuries.
At the time of the event, ANO-1 was in refueling MODE 6 and ANO-2 was in MODE 1 at approximately 100 percent power. The event resulted in a loss of offsite power for ANO-1, with both Emergency Diesel Generators (EDGs) starting to supply safety loads. ANO-1 decay heat removal was lost for approximately four minutes. ANO-2 automatically tripped off-line after the vibration from the dropped Stator resulted in the actuation of relays in the ANO-2 switchgear located adjacent to the train bay, subsequently tripping a reactor coolant pump motor breaker. After the reactor trip, emergency feedwater was manually initiated by ANO-2 control room operators. As debris fell into the train bay, an 8-inch firewater pipe was ruptured and the Alternate AC Diesel Generator electrical tie to ANO-1 was severed. At 0923 CDT that same day, water intrusion from the ruptured firewater piping into a 4160 volt breaker resulted in an ANO-2 Startup Transformer lockout, de-energizing a safety bus. An EDG automatically started as designed and supplied the affected safety bus. An ANO-2 Notification of Unusual Event was declared at 1033 CDT due to fire or explosion caused by the electrical fault in the 4160 volt switchgear with indications of bus damage. After damage assessment and repairs, ANO-2 returned to power operation on April 28, 2013. ANO-1 recovery efforts, formal event investigation and cause determination are currently in progress.
NRC FORM 366 (10-2010)
A. Plant Status At the time of the event, ANO-1 was in refueling MODE 6 with decay heat removal in service and offsite power available. ANO-2 was in MODE 1 at approximately 100 percent power.
B. Event Description
On March 31, 2013, at approximately 0750 CDT, during lifting and removal of the Arkansas Nuclear One Unit 1 (ANO-1) original Main Generator Stator [TB][GEN] (weighing in excess of 500 tons), the temporary lift assembly collapsed, resulting in the Stator falling onto the turbine deck floor (386' elevation), then rolling down into the ANO-1 train bay (354' elevation) adjacent to Arkansas Nuclear One Unit 2 (ANO-2) and landing on the Stator transportation vehicle parked in the train bay. Upon the failure of the lift assembly, the structural members fell onto the ANO-1 and ANO-2 turbine deck floor resulting in the fatality of one individual and multiple other injuries. As debris fell into the train bay, an 8 inch firewater pipe [KP] was ruptured and the Alternate AC Diesel Generator (AACDG) [EK][BU] electrical tie to ANO-1 was severed, rendering the AACDG unavailable to either ANO-1 or ANO-2.
ANO-1: When the Stator impacted the ANO-1 turbine deck floor, part of the concrete and steel floor structure collapsed onto electrical buses beneath the turbine deck, resulting in a loss of all offsite power to ANO-1. Both ANO-1 Emergency Diesel Generators (EDGs) [EK][DG]
automatically started and connected to their respective 4160 volt safety buses as designed.
ANO-1 decay heat removal [BP] flow was re-established after being lost for approximately 4 minutes. Offsite power was restored to ANO-1 on April 6, 2013.
ANO-2: Vibration from the dropped Stator resulted in the actuation of relays in the ANO-2 switchgear located adjacent to the train bay, subsequently tripping the 2P-32B Reactor Coolant Pump (RCP) motor breaker [EA][BKR], which in turn resulted in a Core Protection Calculator (CPC) [ID] signal to automatically trip the ANO-2 reactor. The initial plant response to the trip was normal. An anomaly with one of the Main Feedwater Regulating Valves [SJ][FCV] required the ANO-2 Control Room Operators to secure a Main Feedwater Pump [SJ][P] and manually initiate and use the Emergency Feedwater System [BA] for approximately twenty minutes. At 0923 CDT that same day, water intrusion from the ruptured firewater piping into a 4160 volt feeder breaker [EA][BKR] from the ANO-2 Startup Transformer 3 (SU3) [EA][XFMR] resulted in a SU3 lockout, de-energizing one of two safety buses (2A-4) [EB][BU]. The 2K-4B EDG [EK][DG] automatically started as designed and connected to the affected safety bus. The redundant safety bus (2A3) transferred to Startup Transformer 2 [EA][XFMR], and remained connected to offsite power. A Notification of Unusual Event was declared on ANO-2 at 1033 CDT due to fire or explosion caused by the electrical fault in the 4160 volt switchgear with indications of bus damage. With the loss of SU3, 6900 volt buses 2H-1 and 2H-2 de-energized, resulting in a loss of the remaining RCPs and the one running Circulating Water Pump. This resulted in the need to commence a natural circulation cooldown on ANO-2 using the Atmospheric Dump Valves to remove heat from the Steam Generators. ANO-2 achieved MODE 5 (Cold Shutdown) at 0213 CDT on April 3, 2013. (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL NUMBER REV.
NO.
Arkansas Nuclear One - Unit 1 05000313 2013
- - 001 -
00 3 OF 4 Event Description - continued As a result of the ANO-1 Stator drop, systematic walkdowns and evaluations of ANO-2 structural damage was initiated to determine the extent of damage, and to determine requirements for the restart of ANO-2. After necessary evaluations and repairs were completed, ANO-2 returned to power operation on April 28, 2013.
C. Event Cause
A Root Cause investigation is currently in progress; therefore the cause(s) of the event have not been determined. Additional information will be provided in a supplemental report as appropriate.
D. Corrective Actions
Major corrective actions completed to date:
The evaluation and repair of ANO-2 equipment was completed and ANO-2 has returned to full power operation.
The capability to power ANO-2 buses from the AACDG has been restored.
A temporary off-site power supply has been provided for ANO-1.
Necessary fire water equipment to support plant operation has been restored.
The Stator and lift assembly debris have been removed from the turbine building.
Recovery and repair actions are currently in progress to restore ANO-1 to power operation.
E. Safety Significance Evaluation This event resulted in significant industrial safety consequences, with one fatality and multiple other injuries.
There was no actual radiological threat to the health and safety of the general public during this event. Plant equipment responded as designed to mitigate the event.
Further evaluation of the safety significance of the event will be available after the Root Cause Evaluation has been completed and will be provided in a supplemental report as appropriate. (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL NUMBER REV.
NO.
Arkansas Nuclear One - Unit 1 05000313 2013
- - 001 -
00 4 OF 4 F. Basis For Reportability This event is reported pursuant to the following criteria:
(A) Any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section.
(B) The systems to which the requirements of paragraph (a)(2)(iv)(A) of this section apply are:
(1) Reactor protection system including: reactor scram or reactor trip (ANO-2 reactor trip)
(6) PWR auxiliary or emergency feedwater system (ANO-2 emergency feedwater manual actuation)
(8) Emergency ac electrical power systems, including: emergency diesel generators (ANO-1: Both EDGs actuated on loss of offsite power)
(ANO-2: "B" EDG actuated) 10CFR 50.73(a)(2)(v)
Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to:
(B) Remove residual heat; (ANO-1 Decay Heat Removal)
(D) Mitigate the consequences of an accident.
(ANO-1 Loss of offsite power)
G. Additional Information
10CFR 50.73(b)(5) states that this report shall contain reference to any previous similar events at the same plant that are known to the licensee. NUREG-1022 reporting guidance states that term "previous occurrences" should include previous events or conditions that involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.
A review of the ANO corrective action program and Licensee Event Reports revealed no relevant similar events.
Energy Industry Identification System (EIIS) codes and component codes are identified in the text of this report as [XX].
Event investigation and cause determination activities for this event are on-going at this time.
Therefore, additional information required by 10CFR 50.73 will be provided in a supplemental report, tentatively expected by September 15, 2013.
to 0CAN051303 List of Regulatory Commitments
to 0CAN051303 Page 1 of 1 List of Regulatory Commitments The following table identifies those actions committed to by Entergy in this document.
Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.
TYPE (Check one)
COMMITMENT
ONE-TIME ACTION CONTINUING COMPLIANCE SCHEDULED COMPLETION DATE (If Required)
Provide a supplemental revision to Licensee Event Report 50-313/2013-001-00 X
September 15, 2013