05000285/LER-2008-001, Reactor Trip Due to Turbine Control System Failure
| ML081420025 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 05/13/2008 |
| From: | Nellenbach T Omaha Public Power District |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LIC-08-0046 LER 08-001-00 | |
| Download: ML081420025 (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 |
| 2852008001R00 - NRC Website | |
text
k MGaha PibiPowe:; Disrijci 1946 - 2006 Fort Calhoun Station P.0. Box 550 Fort Calhoun, NE 68023 LIC-08-0046 May 13, 2008 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Reference:
Docket No. 50-285
Subject:
Licensee Event Report 2008-001 Revision 0 for the Fort Calhoun Station Please find attached Licensee Event Report 2008-001, Revision 0, dated May 13, 2008.
This report, isbeingsubmitted pursuant to 10CFR50.73(a)(2)(iv)(A).
The root cause information contained; in this,report is preliminary; therefore, the Omaha Public Power District.;plans to.provide.a supplement describing the final root cause by August 8, 2008. If you should have any questions, please contact me.
Sincerely, T. R. Nellenbach Division Manager - Nuclear Operations TRN/EPM/epm Attachment c:.. -
E. E. Collins, -NRC Regional. Administrator;, Region.IV *.
M. T -Ma key,NF N
Se1nr S
roect Mann. e J. D. Hanna, NRC Senior Resident Inspector
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NRC FORM 366 U.S. NUCLEAR REGULATORYCOMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Fort Calhoun Station 05000285 1
OF 3
- 4. TITLE Reactor Trip Due to Turbine Control System Failure
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTI REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR AL REV MONTH DY YA 50 NUMBER NO 05000 FACILITY NAME000 03 15 2008 2008
- - 001 -
00 05 13 2008 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 0 20.2201 (b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 01 0
20.2201 (d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 0 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A) 10 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A)
X 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)
- 10. POWER LEVEL 0
20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) 85 0
20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 0 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 During the trip, the letdown system automatically isolated. The letdown system was manually restored at about 0903 CDT. A relief valve located between the containment isolation valves for the letdown system was noted to be leaking. (FCS LER 2008-002 will provide a detailed report of this situation.)
The emergency diesel generators (EDGs) automatically started as required on the reactor trip. EDG-1 was secured at 1007 CDT. EDG-2 was secured at 1020 CDT.
The operators transitioned from EOP-00 to EOP-02 "Loss of Off-Site Power Loss of Forced Circulation,"
due to the loss of power to a non-vital electrical bus during the trip. At 0958 the operators entered the plant shutdown procedure, OP-3A. The plant was maintained in Mode 3 for the duration of the outage.
Discrepancies noted during the plant trip were entered into the station's corrective action system for disposition. The corrective action document for the plant trip is CR 2008-1592 At 1019 CDT, the NRC Headquarters Operations Office (HOO) was notified of the event per 10 CFR 50.72(b)(2)(iv)(B) and meeting the requirements of 10 CFR 50.72(b)(3)(iv)(A). This event is reportable per 10 CFR 50.73(a)(2)(iv)(A).
CONCLUSION The apparent cause of the reactor trip was the failure of a circuit board in the EHC control system resulting in the closure of turbine control valves CV-1 and CV-3. Closure of these valves results in a pre-emptive trip of the reactor due to the loss of load. A failure analysis of the circuit board is in progress. In addition, the root cause analysis (RCA) of the trip is in progress. A supplement to this LER will be made based on the findings of the RCA.
CORRECTIVE ACTIONS
The failed circuit board was replaced. Post maintenance testing was performed on the EHC system to ensure its reliability. Additional corrective actions will be implemented by the station's corrective action program.
SAFETY SIGNIFICANCE
Loss of Load is an analyzed plant transient and plant response was within the predicted response parameters. All control rods were inserted into the reactor core as required. Decay heat removal by the main steam and feedwater systems was available as required for the transient by plant procedures. While this event resulted in an actuation of the Reactor Protective System due to the Loss of Load from the turbine generator, it did not pose a threat to the health and safety of the public.
SAFETY SYSTEM FUNCTIONAL FAILURE This event does not result in a safety system functional failure in accordance with NEI-99-02.
PREVIOUS SIMILAR EVENTS
FCS has not had any previous similar reactor trips due to failures of the turbine control circuitry.PRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPER