05000301/LER-2010-004, Regarding Manual Reactor Trip During Startup
| ML110450683 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 02/14/2011 |
| From: | Meyer L Point Beach |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2011-0019 LER 10-004-00 | |
| Download: ML110450683 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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) |
| 3012010004R00 - NRC Website | |
text
February 14,201 1 NEXBera TM ENERGY@
POINT BEACH 7
NRC 201 1-001 9 10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Point Beach Nuclear Plant, Unit 2 Docket 50-301 Renewed License No. DPR-27 Licensee Event Report 30112010-004-00 Manual Reactor Trip During Startup Enclosed is Licensee Event Report (LER) 3011201 0-004-00 for Point Beach Nuclear Plant (PBNP), Unit 2. This LER documents the completion of a manual reactor trip during startup. Pursuant to 10 CFR 50.73(a)(2)(iv)(A), the event is reportable as any event or condition that resulted in manual or automatic actuation of the reactor protection system.
This submittal contains no new or revised regulatory commitments.
If you have questions or require additional information, please contact Mr. James Costedio at 9201755-7427.
Very truly yours, NextEra Energy Point Beach, LLC Site Vice President Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Point Beach Nuclear Plant, USNRC Resident Inspector, Point Beach Nuclear Plant, USNRC PSCW NextEra Energy Point Beach, LLC, 6610 Nuclear Road, Two Rivers, WI 54241
20.2203(a)(3)(i) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) subcritical. The manual reactor trip was initiated because rod control urgent and non-urgent alarms had been received with multiple control rods inserting freely, as indicated by individual rod position indicators and rod bottom lights. All systems functioned as expected following the trip, with all control rods fully inserting into the core.
Troubleshooting determined that a degraded field connection for the D-10 control rod was the cause of the event. The degraded connection was repaired. Unit 2 was returned to service on December 21, 201 0, at 0824 CST with no anomalies occurring during startup.
Additional corrective actions include inspections of the connections during each unit's 201 1 refueling outage. These actions are being tracked in the site's corrective action program.
This 60-day licensee event report is being submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of the reactor protection system (RPS).
NCR FORM 366 (1 0-201 0)
Event Description
On December 15, 201 0, at 0148 CST, control room personnel initiated a manual reactor trip to abort a startup in progress with the Unit 2 reactor [AC] subcritical.
During the performance of the Unit 2 reactor startup, both rod control urgent and non-urgent alarms were received. Shortly after receiving the alarms, multiple groups of control rods [AA] inserted freely into the reactor core as indicated by individual rod position indicators and rod bottom lights. Based on these indications, a manual reactor trip of Unit 2 was initiated. All systems functioned as expected following the trip, with all control rods fully inserting into the core.
This 60-day licensee event report is being submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of the reactor protection system (RPS).
Event Analysis
Unit 2 reactor startup was commenced on December 15, 2010, at 001 5 CST. While moving Control Bank D from 25 to 52 steps, panel rod control urgent and non-urgent alarms were received. Operators observed multiple rod bottom lights lit and individual rod position indications lowering. The control room alarm system recorder indicated that the control rods freely inserted into the core within 2 seconds. A manual reactor trip was initiated December 15, 201 0, at 01 48 CST. Both the A and B reactor trip breakers opened as designed and the remaining control rods fully inserted into the core.
In response to the event, troubleshooting included inspection or testing of rod drive control (RDC) logic cabinet cards; RDC power cabinet cards; Control rod drive mechanism (CRDM) cables and connectors; CRDM power supplies; CRDM coil and insulation resistances; RDC components such as resistors, diodes, and fuses; motor generator output voltage; and neutral bus to ground isolation.
Components that were repaired or replaced as a result of the troubleshooting included: numerous power supplies in the power cabinets; numerous logic cabinet and power cabinet cards; and the connections from the reactor vessel head to control rod D-10.
Following completion of the repairs, post-maintenance testing was completed satisfactorily, which included cycling each rod bank, analysis of coil current traces and withdrawal of all rods in a simulated startup with the rod selector switch positioned in manual.
Safety Significance
The reactor was subcritical when the rods inserted into the core. The reactivity transient was small and the potential for core damage was minimal. Thus, the safety significance of the event was low. There was no impact on the health and safety of the public because of this event. This is not a safety system functional failure.
Cause
The cause of the event was a short in the connection for the D-10 control rod between the rod and the reactor vessel head upgrade package patch panel. Both lift coil leads were found damaged with exposed conductors.
Corrective Actions
As described above, corrective actions included repair or replacement of numerous power supplies in the power cabinets, numerous logic cabinet and power cabinet cards, and the connections from the reactor vessel head upgrade package patch panel to control rod D-10.
In addition to the above, the following actions will be taken and are being tracked in the site's corrective action program:
Unit 1 and Unit 2 control rod drive mechanism (CRDM) head and patch panel connections will be inspected during each unit's respective 201 1 refueling outage.
MeggarJECAD testing will be added to the CRDM PM schedule.
Unit 1 24 V DC power supplies will be replaced during that unit's upcoming fall 201 1 refueling outage.
Previous Occurrences
None Failed Components Identified:
None