05000341/LER-2010-001, For Fermi 2, Regarding Automatic Reactor Shutdown Due to Generator Current Transformer Wiring Failure
| ML101400553 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/19/2010 |
| From: | Plona J Detroit Edison |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-10-0043 LER 10-001-00 | |
| Download: ML101400553 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3412010001R00 - NRC Website | |
text
Joseph H. Plona Site Vice President 6400 N, Dixie Highway, Newport, MI 48166 Tel: 734,586.5910 Fax: 734.586.4172 10CFR50.73 May 19, 2010 NRC-10-0043 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555-0001 Reference: Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Licensee Event Report No. 2010-001, "Automatic Reactor Shutdown due to Generator Current Transformer Wiring Failure" Pursuant to 10 CFR 50.73(a)(2)(iv)(A), Detroit Edison is hereby submitting the enclosed Licensee Event Report (LER) No. 2010-001. This LER documents an automatic reactor shutdown that occurred on March 25, 2010 due to a failure of the generator output current transformer wiring resulting in a main generator trip with a subsequent main turbine trip and automatic reactor shutdown.
No commitments are made in this LER.
Should you have any questions or require additional information, please contact Mr.
Rodney W. Johnson of my staff at (734) 586-5076.
Sincerely, cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 4, Region III Regional Administrator, Region III Supervisor, Electric Operators, Michigan Public Service Commission Joseph H. Plona Site Vice President fi400 N. Dixie Highway, Newport, MI 481GG Tel: 734.586.5910 Fax: 784.58(j.4172 May 19, 2010 NRC-1O-0043 u. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington DC 20555-0001 Reference: Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43 10CFR50.73
Subject:
Licensee Event Report No. 2010-001, "Automatic Reactor Shutdown due to Generator Current Transformer Wiring Failure" Pursuant to 10 CPR 50.73(a)(2)(iv)(A), Detroit Edison is hereby submitting the enclosed Licensee Event Report (LER) No. 2010-001. This LER documents an automatic reactor shutdown that occurred on March 25, 2010 due to a failure of the generator output current transformer wiring resulting in a main generator trip with a subsequent main turbine trip and automatic reactor shutdown.
No commitments are made in this LER.
Should you have any questions or require additional information, please contact Mr.
Rodney W. Johnson of my staff at (734) 586-5076.
cc: NRC Project Manager NRC Resident Office Sincerely, Reactor Projects Chief, Branch 4, Region III Regional Administrator, Region III Supervisor, Electric Operators, Michigan Public Service Commission
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: No. 3150-0104 Expires 8/31/2010 (9/2007)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE Fermi 2 05000341 1 OF 3
- 4. TITLE Automatic Reactor Shutdown due to Generator Current Transformer Wiring Failure
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO 05000 03 25 2010 2010 001 00 05 19 2010 FACILITYNAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 1 20.2201(b) 0 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii)
]
20.2201(d) 0 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A)
]
20.2203(a)(1) 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
_ _ 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii)
Q 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL O 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)
[
50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)
[] 20.2203(a)(2)(iii) 50.36(c)(2)
[
50.73(a)(2)(v)(A) 73.71 (a)(4) 63%
0 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER 0
20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in abstract below or in (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
Initial Plant Conditions
Mode 1 Reactor Power 63 percent Description of the Event I
REVISION NUMBER 00
- 3. PAGE 2 OF 3 At 16:27 EDT on March 25, 2010, the reactor mode switch [HS] was taken to shutdown following an automatic scram due to a main turbine [TA] trip. The Operations Department was in the process of raising power prior to the event. The Main Turbine Trip relays actuated causing a turbine control valve fast closure which initiated a scram signal. Investigation determined that the Main Turbine Trip relays actuated due to a generator differential current relay trip in the Main Generator Z phase protection circuit. The Z phase relay actuation was caused by a shorted current transformer wire in the Main Generator Z phase line terminal bushing enclosure.
The scram was uncomplicated. The reactor protection system (RPS) [JD] performed as expected, and all control rods were fully inserted into the core. Reactor water level reached a low of approximately 135 inches above top of active fuel and recovered to normal level of 173 to 214 inches automatically with the reactor feedwater system [SJ] following the scram without operator intervention. Reactor water Level 3 isolations occurred and Reactor water level was maintained above Level 2 as expected. No primary containment isolations or safety injection system initiations associated with Level 2 occurred.
Reactor pressure control was maintained by the turbine bypass valves. The peak Reactor Pressure was 1000 psig, within normal pressure control limits and no safety relief valves (SRVs) actuated.
There was no maintenance or testing in progress that would affect generator differential relaying. Safety related plant equipment responded as expected to the reactor scram. At the time of the scram, all Emergency Core Cooling Systems (ECCS) and Emergency Diesel Generators (EDGs) [DG] were operable.
This report is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an event that resulted in an unplanned manual or automatic actuation of the reactor protection system (RPS) when the reactor was critical.
Significant Safety Consequences and Implications
This event posed no significant safety implications because the reactor protection and safety related systems functioned as designed following the automatic reactor trip. Important safety-related and non-safety related equipment performed as discussed in the description of the event, and plant response was as expected. There was no significant increase in reactor pressure, and the reactor core was adequately covered and cooled throughout the event.
Therefore, the health and safety of the public were not affected by this event. U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Fermi 2 05000341 NUMBER NUMBER 3 OF 3 2010 001 00 This event is being reported under 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in automatic actuation of the reactor protection system and a reactor scram. A 4-hour non-emergency notification was made to the NRC Operations Center at 18:18 EDT on March 25, 2010 (EN 45789) in accordance with 10 CFR 50.72(b)(2)(iv)(B) for an actuation of the reactor protection system.
Cause of the Event
The automatic reactor scram was due to Main Turbine Trip relays actuating causing a turbine control valve fast closure. Investigation determined that the Main Turbine Trip relays actuated due to a generator differential current relay trip in the Main Generator Z phase protection circuit. The cause of the Z phase relay actuation was the result of a shorted current transformer (CT) wire in the Main Generator Z phase line terminal bushing enclosure.
One of the wires connected to the generator differential protection current transformer, installed on the Main Generator Z phase line terminal bushing, shorted to ground inside the CT/bushing enclosure. The impedance/current imbalance in the Z phase differential protection circuit, caused by the ground short condition, resulted in actuation of the Z-87G protection relay, energizing the Main Turbine Trip relays and causing the turbine control valve fast closure logic to initiate an automatic reactor scram.
The CT wire failure was due to abrasion at the conduit entrance to the CT/bushing enclosure. The conduit bulkhead connecter utilizes a nylon insulated throat that was found degraded at the location where the wire shorted to ground.
Corrective Actions
The shorted CT wire was located and repaired in accordance with plant design specifications. Protective layers of tape were added to this and other similar generator CT wiring in locations where the wiring interfaces with the conduit entries as a preventive measure for all output and neutral phases. This event is documented and evaluated in the Fermi 2 corrective action program. Other actions are being considered to address this event. These actions will be tracked and implemented by the corrective action program.
Additional Information
A.
Failed Components: The conduit that failed was a Thomas & Betts (T&B) insulated throat fitting used for jacketed flexible liquid tight conduit entry.
B.
Previous LERs on Similar Problems: NoneNRC FORM 366A (9-2007)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET I
YEAR Fermi 2 05000341 2010
- 6. LER NUMBER SEQUENTIAL NUMBER 001 I
REVISION NUMBER 00
- 3. PAGE 3 OF 3 This event is being reported under 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in automatic actuation of the reactor protection system and a reactor scram. A 4-hour non-emergency notification was made to the NRC Operations Center at 18: 18 EDT on March 25, 2010 (EN 45789) in accordance with 10 CFR 50.72(b)(2)(iv)(B) for an actuation of the reactor protection system.
Cause of the Event
The automatic reactor scram was due to Main Turbine Trip relays actuating causing a turbine control valve fast closure. Investigation determined that the Main Turbine Trip relays actuated due to a generator differential current relay trip in the Main Generator Z phase protection circuit. The cause of the Z phase relay actuation was the result of a shorted current transformer (CT) wire in the Main Generator Z phase line terminal bushing enclosure.
One of the wires connected to the generator differential protection current transfonner, installed on the Main Generator Z phase line terminal bushing, shorted to ground inside the CT/bushing enclosure. The impedance/current imbalance in the Z phase differential protection circuit, caused by the ground short condition, resulted in actuation of the Z-87G protection relay, energizing the Main Turbine Trip relays and causing the turbine control valve fast closure logic to initiate an automatic reactor scram.
The CT wire failure was due to abrasion at the conduit entrance to the CT/bushing enclosure. The conduit bulkhead connecter utilizes a nylon insulated throat that was found degraded at the location where the wire shorted to ground.
Corrective Actions
The shorted CT wire was located and repaired in accordance with plant design specifications. Protective layers of tape were added to this and other similar generator CT wiring in locations where the wiring interfaces with the conduit entries as a preventive measure for all output and neutral phases. This event is documented and evaluated in the Fermi 2 corrective action program. Other actions are being considered to address this event. These actions will be tracked and implemented by the corrective action program.
Additional Information
A.
Failed Components: The conduit that failed was a Thomas & Betts (T&B) insulated throat fitting used for jacketed flexible liquid tight conduit entry.
B.
Previous LERs on Similar Problems: None