05000255/LER-2019-002, Automatic Reactor Trip and AFW System Actuation Due to the Loss of Power to the RPS Bd Matrix
| ML19059A136 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 02/28/2019 |
| From: | Hardy J Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PNP 2019-012 LER 2019-002-00 | |
| Download: ML19059A136 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2552019002R00 - NRC Website | |
text
w===-Entergy PNP 2019-012 February 28, 2018 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.
Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel 269 764 2000 Jeffery A. Hardy Regulatory Assurance Manager 10 CFR 50.73
Subject:
LER 2019-002 Automatic Reactor Trip and AFW System Actuation Due to the Loss of Power to the RPS SO matrix Palisades Nuclear Plant NRC Docket 50-255 Renewed Facility Operating License No. DPR-20 Entergy Nuclear Operations, Inc., hereby submits the enclosed Licensee Event Report (LER),
2019-002-00, for the Palisades Nuclear Plant. The LER describes an automatic actuation of the reactor protection system and an automatic actuation of the auxiliary feedwater system. The occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
This letter contains no new commitments and no revisions to existing commitments.
Should you have any questions concerning this report, please contact Mr. Jeffery Hardy, Regulatory Assurance Manager, at (269) 764-2011.
Enclosure:
LER 2019-002 Automatic Reactor Trip and AFW System Actuation Due to the Loss of Power to the RPS SO matrix CC Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC
Enclosure PNP 2019-012 LER 2019-002-00, Automatic Reactor Trip and AFW System Actuation Due to the Loss of Power to the RPS BD matrix 3 Pages Follow
NRC FORM 366U S NUCLEAR REGULATORY APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03131/2020 (02*2018)
, the NRC may not conduct or sponsor, and a person is not required to respond to the information collection.
- 1. Facility Name
~. Docket Number
- Page PALISADES NUCLEAR PLANT 05000255 10F3
- 4. Title Automatic Reactor Trip and AFW System Actuation due to the Loss of Power to the RPS SD matrix I
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year
~5000 01 09 2019 2019
- - 002
- - 00 02 28 2019 Facility Name Docket Number
~5000
- 9. operating Mode Abstract (Lim~ to 1400 spaces, i.e., approximately 14 single*spaced typewritten lines)
On January 9,2019, maintenance personnel were performing a calibration of NI-6, "Power Range Safety ChanneL" The plant was in mode 1 at 100% power. At approximately 10:28 EST, maintenance personnel removed the panel on EC-06, "Reactor Protection System (RPS) cabinet," and observed an arc in the vicinity of incoming AC power. It was immediately observed that the entire RPS S channel had lost power. Approximately six minutes after the loss of power to RPS S channel, the reactor tripped. Following the reactor trip, it was identified that the RPS D channel matrix SD power supply was not lit, indicating no output.
The required safety systems and shutdown equipment performed as expected, resulting in an uncomplicated trip. The condition was reported on January 9,2019 (Event Number 53819) in accordance with 10 CFR 50.72(b)(2)(iv)(S) and 10 CFR 50.72(b)(3)(iv)(A) for both a valid reactor protection system (RPS) actuation and an auxiliary feedwater actuation (AFW).
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in a valid actuation of both the RPS and the AFW.
The cause was attributed to shorted capacitors in the S RPS cabinet and a blown input fuse to the RPS D channel SD matrix power supply. Corrective actions were taken to replace the capacitors with insulated capacitors, and to replace the RPS D channel SD matrixpower sup my and fuse. (04-2017)
COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form htto:!lwww.nrc.aov/readina-rm/doc-collectionslnureas/staff/sr1 022/r3/\\
APPROVED BY OMB: NO_ 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to. the information collection.
- 3. LEA NUMBER YEAR PALISADES NUCLEAR PLANT 05000-255 SEQUENTIAL NUMBER REV NO.
2019
- - 002
- - 00
EVENT DESCRIPTION
On January 9, 2019, the plant was in mode 1 at 100% power. Maintenance personnel were performing RI-62B, "Power Range Safety Channel Alignment-Channel B." Part of this surveillance requires removal of a bottom panel [PL] on the drawer while it is pulled out of the RPS cabinet [CAB]. During the removal of this panel at 10:28 EST, maintenance personnel heard and observed an arc in the vicinity of the incoming AC power. Immediately, the entire RPS B channel lost power. Approximately six minutes after the loss of power to RPS B channel, the reactor [RCT] automatically tripped. The trip was uncomplicated with all rods fully inserted. The auxiliary feedwater system (AFW) actuated as designed in response to steam generator [SG]
water levels.
Troubleshooting was performed to determine the cause of the event. The delay between the initial loss of power to the RPS B channel and the reactor trip is indicative of two separate failures. The first failure was a short that tripped the RPS B breaker [BKR] while removing the bottom panel during surveillance testing. The leads of the capacitors [CAP] that were connected to the line and neutral wires were not insulated and were in close proximity to each other. During the removal of the drawer's bottom cover, the disc capacitors moved slightly such that the non-insulated leads on each of the two capacitors touched, causing the short circuit that tripped the RPS B breaker.
The second failure occurred approximately six minutes after the loss of the B channel power. Inspection of the RPS 0 channel indicated that the BO matrix power supply [JX] was not lit; indicating it had no voltage output. The RPS 0 channel BO matrix power supply experienced a subcomponent failure, resulting in an overcurrent condition and loss of power output. There were no other structures, systems, or components (SSCs) that were inoperable at the time that contributed to the event.
This condition is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in a valid actuation of both the RPS and the AFW.
Corrective actions were taken to replace the capacitors in the B RPS cabinet with insulated capacitors and replace the RPS 0 channel BO matrix power supply and fuse [FU]. Operability was restored and the plant returned to service on January 11, 2019.
Energy Industry Identification System (EllS) codes and component codes are identified in brackets above.
CAUSE OF THE EVENT
The direct cause of the loss of all power to the RPS BO matrix was the shorted capacitors (RPS B channel) and blown input fuse to the RPS 0 channel BO matrix power supply.
Loss of all power to the RPS BO matrix resulted in the four BO matrix relays de-energizing. This interrupted power to the four clutch power supplies causing all control rods to insert, tripping the reactor per RPS design.
NRC FORM 3668 (02-2018) (04-2017)
,........... \\
I~ i
\\~J U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1 022, R3 for instruction and guidance for completing this form htto:/Iwww.nrc_aov/readina-rm/doc-collections/nureas/staff/sr1022/r31l APPROVED BY OMB: NO_ 3150-0104 EXPIRES: 3131/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LEA NUMBER YEAR PALISADES NUCLEAR PLANT 05000-255 2019
ASSESSMENT OF SAFETY CONSEQUENCES
SEQUENTIAL NUMBER
- - 002 REV NO.
- - 00 The safety significance of the event was low. There were no consequences with regard to the safety of the public, nuclear safety, industrial safety, or radiological safety for this event. Loss of power within the RPS matrix is evidenced by alarms and loss of indication on the RPS matrix panel. Operators are trained to recognize these conditions and manually trip the reactor, if automatic RPS actuation does not occur.
CORRECTIVE ACTIONS
The RPS B channel capacitors were replaced with insulated capacitors. The remaining four range channels were inspected and verified to have insulated capacitors installed. The RPS D channel BD matrix power supply and fuse were replaced. Both the RPS D channel BD matrix power supply and fuse were sent to the vendor for failure evaluation. The results of the vendor failure evaluation will be used to determine any additional actions.
PREVIOUS OCCURENCES
A review of the Palisades Nuclear Plant (PNP) corrective action program database for events involving NI-6 and capacitors was completed. No similar events for PNP were previously identified.
A PNP corrective action database review was completed for RPS power failure events. RPS has a history of power supply failures including matrix power supplies. Due to this history, the RPS matrix power supplies were all replaced in early 2013. One matrix supply failed approximately two months after replacement with no impact on the plant as the other matrix power supply carried the load. The failed power supply was sent for detailed vendor analysis, though no specific cause was determined.