05000413/LER-2004-004, Regarding Spurious Moisture Separator Reheater High Level Actuation Resulting in an Automatic Turbine Trip and Reactor Trip
| ML050470241 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 02/02/2005 |
| From: | Jamil D Duke Energy Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 04-004-00 | |
| Download: ML050470241 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| 4132004004R00 - NRC Website | |
text
P Duke OrPowere A Duke Energy Company D.M. JAMIL Vice President Duke Power Catawba Nuclear Station 4800 Concord Rd. / CN01 VP York, SC 29745-9635 803 831 4251 803 831 3221 fax February 2, 2005 U. S. Nuclear Regulatory Commission ATTENTION:
Document Control Desk Washington, DC 20555-0001
SUBJECT:
Duke Energy Corporation Catawba Nuclear Station Unit 1 Docket No. 50-413 Licensee Event Report 413/2004-004 Revision 0 Spurious Moisture Separator Reheater High Level Actuation Resulting in an Automatic Turbine Trip and Reactor Trip Attached please find Licensee Event Report 413/2004-004 Revision 0, entitled "Spurious Moisture Separator Reheater High Level Actuation Resulting in an Automatic Turbine Trip and Reactor Trip".
This Licensee Event Report does not contain any regulatory
commitments
This event is considered to be of no significance with respect to the health and safety of the public.
Questions regarding this Licensee Event Report should be directed to G. K. Strickland at 803-831-3585.
Sincerely,
~',-fUa D. M. Jamil Attachment www. dukepower. cornm,L 04
U.S. Nuclear Regulatory Commission February 2, 2005 Page 2 xc:
W. D. Travers U. S. Nuclear Regulatory Commission Regional Administrator, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 S. E. Peters (addressee only)
U. S. Nuclear Regulatory Commission Mail Stop 0-8 G9 Washington, DC 20555-0001 E. F. Guthrie Senior Resident Inspector (CNS)
U. S. Nuclear Regulatory Commission Catawba Nuclear Site INPO Records Center 700 Galleria Place Atlanta, GA 30339-5957
Abstract
On December 5, 2004, at 2135 hours0.0247 days <br />0.593 hours <br />0.00353 weeks <br />8.123675e-4 months <br />, with Catawba Unit 1 operating in Mode 1 at 100% power, an automatic reactor trip occurred due to a turbine trip above P-9 (69% power).' The turbine trip was due to an invalid high water level indication from two of the three level switches for the 1B moisture separator reheater.
The root cause of the reactor trip was due to micro-switch mechanisms on the two level switches being out of adjustment, concurrent with external vibration to the switches.
The plant response to the reactor trip remained within the limits of the Updated Final Safety Analysis Report.
Major plant equipment operated as expected.
This event was of no significance with respect to the health and safety of the public.
Corrective actions for this event included inspecting all Unit 1 and Unit 2 micro-switch positions, and adjusting or replacing the switch mechanisms as necessary.
NRC FORM 366 (6-2004)
NRC FORM 368A U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
DOCKET (2)
FACILITY NAME (1)
NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL l REVISION YEAR l
NUMBER l NUMBER Catawba Nuclear Station, Unit 1 05000413 2004 004 00 2
OF 6
NARRATIVE
(if more space is required, use additional copies of (If more space Is required, use additional copies of NRC Form 3664) (17)
Based on interviews, these activities were not believed to be the cause of the level switch actuation.
12/5/04 2205 Plant conditions stabilized at no load conditions. The plant response to the trip remained within the limits of the Final Safety Analysis Report.
reactor Updated Major plant equipment operated as expected.
The following minor issues were noted:
Steam generator IC power operated relief valve [EIIS: PSV] lifted briefly at 1116 psig.
Steam generator lB main feedwater control valve [EIIS: LCV) ICF37 did not indicate fully closed.
The valve automatically responded to its correct, closed position.
Four hour notification to the NRC completed.
Team assembled to investigate the reactor trip.
Unit 1 reactor critical Unit 1 main generator-on line.
12/6/04 0017 12/6/04 12/7/04 0257 12/7/04 0816 12/7/04 2124 Unit 1 at 100% power CAUSAL FACTORS An automatic reactor trip occurred due to a turbine trip above 69%
power.
The turbine trip was due to an invalid high water level indication from two of the three level switches for the lB moisture separator reheater.
(If more space Is required, use additional copies of NRC Fonn 3684) (17)
The root cause of the reactor trip is due to micro-switch mechanisms on the two level switches being out of adjustment, concurrent with external vibration to the switches.
The cause of the switch mechanisms being out of adjustment is inconclusive; however, the two probable causes are either 1) the switch mechanisms were obtained from the manufacturer out of adjustment, or 2) inadequate procedural guidance was provided to ensure the successful replacement / adjustment / testing of the switches.
The second probable cause for inadequate procedural guidance is believed to be the more likely cause.
CORRECTIVE ACTIONS
Immediate:
- 1. Plant conditions were stabilized at no-load conditions.
Subsequent:
l.All Unit 1 and Unit 2 MSR level switches were inspected.
Switches were repaired or adjusted as necessary.
- 2. Personnel barriers were initially placed around Unit 1 and Unit 2 MSR level switches to prevent accidental bumping of the switches.
Caution signs were later placed in the vicinity of the switches and the personnel barriers were removed.
3.Valve indication for the 1B main feedwater control valve 1CF37 was repaired.
Planned:
- 1. Revise the applicable maintenance procedure to include appropriate guidance for switch adjustments.
- 2. Replace all of the current Unit 1 and Unit 2 switch mechanisms with manufacturer adjusted switch mechanisms.
- 3. Evaluate other, same-vendor, critical level switch applications for applicability.
(If more space Is required, use additional copies of (If more space Is required. use additIonat copies of NRC Form 366A) (17)
The reactor trip event has been evaluated quantitatively for risk significance considering the following:
- A reactor trip initiating event
- No additional Probabilistic.Risk Assessment modeled equipment out of service The conditional core damage probability (CCDP) for this event is calculated to be approximately 2.5E-07.
The conditional large early release probability (CLERP) is calculated to be about 3.8E-09.
These values are less than the accident sequence precursor thresholds of 1.OE-06 and 1. OE-07, respectively.
The dominant base case large early release frequency (LERF) sequences for Catawba involve steam generator tube rupture, interfacing systems LOCA, and seismic-initiated sequences. The reliability of the important containment safeguards systems (containment spray and hydrogen mitigation) was not impacted by the reactor trip.
This event was of no significance with respect to the health and safety of the public.
ADDITIONAL INFORMATION
Within the last three years, five other reactor trip events occurred from power operation at Catawba Unit 1 and Unit 2. None of these previous events involved spurious level switch actuation or improper level switch adjustments.
Therefore, this event was determined to be non-recurring in nature.
Energy Industry Identification System (EIIS) codes are identified in the text as [EIIS: XX].
The level switch is an EPIX program reportable equipment failure.
This event does not reflect a manual reactor trip with a loss of secondary heat removal capability as monitored by the NRC performance indicator.
This event did not involve a Safety System Functional Failure.
There were no releases of radioactive materials, radiation exposures, or personnel injuries associated with this event.