05000306/LER-2018-001, For Prairie Island Nuclear Generating Plant, Unit 2, Automatic Actuation of Emergency Diesel Generator D5
| ML18197A413 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 07/16/2018 |
| From: | Sharp S Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-PI-18-037 LER 2018-001-00 | |
| Download: ML18197A413 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(iv)(A), System Actuation 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3062018001R00 - NRC Website | |
text
1717 Wakonade Drive Welch, MN 55089 Xcel Energy R E S P O N S I B LE B Y N AT U RE 800.895.4999 xcelenergy.com JUL \\ 6 2018 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant, Unit 2 Docket No. 50-306 Renewed Facility Operating License No. DPR-60 L-Pl-18-037 10CFR50.73 Licensee Event Report 50-306/2018-001-00, Automatic Actuation of Emergency Diesel Generator D5 Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), encloses Licensee Event Report (LER) 50-306/2018-001-00, Automatic Actuation of Emergency Diesel Generator D5.
Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
,PJ9 Scott Sharp Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company-Minnesota Enclosure cc:
Regional Administrator, Region Ill, USNRC Project Manager, Prairie Island Nuclear Generating Plant, USNRC Resident Inspector, Prairie Island Nuclear Generating Plant, USNRC State of Minnesota
Document Control Desk Page 2 ENCLOSURE Licensee Event Report 50-306/2018-001-00 5 Pages Follow
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) htt12://www.nrc.gov/reading-rm/doc-collections/nuregs/stafflsr1022/r3D the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 13. PAGE Prairie Island Nuclear Generating Plant Unit 2 05000-306 1 OFS
- 4. TITLE Automatic Actuation of Emeraencv Diesel Generator D5
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR NUMBER NO.
05000 5
17 2018 2018
- - 001
- - 00 7
16 2018 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
Unit 2 Mode 1
- 20.2201(b)
D 20.2203(a)(3)(i)
- 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
- 20.2201(d)
D 20.2203(a)(3)(ii)
- 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
- 50.36(c)(1)(i)(A)
[8J 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(ii)
- 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5)
Unit 2 100%
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1)
D 20.2203(a)(2)(v)
- 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi)
- 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(C)
- OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT IILEPHONE NUMBER (Include Area Code)
!Frank Sienczak
~12-342-8987 CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORT AS LE FACTURER TOEPIX FACTURER TOEPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR 0 YES (ff yes, complete 15. EXPECTED SUBMISSION DATE)
[8J NO SUBMISSION DATE
~BSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On May 17, 2018, at 11: 15 Central Daylight Time (CDT), with Unit 2 in Mode 1 at 100% power, the station experienced an auto-start of Emergency Diesel Generator (EOG), D5. The Bus 25 Potential Transformer fuse drawer was opened by a supplemental worker, causing Breaker 25-16 to open and de-energize Bus 25. Operators were able to manually close the EOG D5 output breaker to re-energize Bus 25. All equipment functioned as designed. EOG D5 was restored to a normal condition on May 17, 2018, at 16:44. This event was reported in accordance with 10 CFR 50. 72(b)(3)(iv)(A) as an event that results in a valid actuation of the EOG.
The Root Cause for this event was that Prairie Island Open Phase Project was inadequately challenged to recognize and understand the risk associated with transitioning work activities from the 2R30 Outage to the Online schedule.
Corrective Actions, include Revising the "Online Scheduling Procedure" to include a requirement for a challenge board to be held for Outage to Online decisions involving Modifications. Labeling PT drawers with equipment ID and locking device and caution to instruct operator approval prior to opening drawer and contain a physical barrier such as a lock or zip tie to discourage opening.
NRG FORM 366 (04-2017)
DESCRIPTION OF EVENT
SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 On May 17, 2018 at 11: 15 Central Daylight Time (CDT), with Unit 2 in Mode 1 at 100% power, the station experienced an auto-start of Emergency Diesel Generator1 (EOG), D5. During the 4kV2 Bus Modification for the Open Phase project, installation activities were being performed by supplemental workers in the Bus 25 room. During the performance of work activities, the Bus 25 Potential Transformer (PT) fuse drawer was opened. The circuits associated with this PT drawer provide the voltage signal to the Bus 25 Load Sequencer undervoltage relays. With the PT drawer open, degraded, under voltage and loss of voltage signals were detected. An actual abnormal voltage condition did not exist prior to opening the PT drawer. This caused Breaker 25-16 to open and de-energized Bus 25.
This event was initiated by human error, whereby a supplemental worker took action to open the PT drawer in an effort to complete work activities. The worker believed the component was isolated as part of the work clearance but did not perform adequate verification to ensure that Fuse/Bus 25 Potential Transformer (FU/825 25-16POT) was included on the tag-out list prior to taking action. The crew had reviewed the copy of a tag affixed to fuses removed from Fuse/ 2RY Potential Transformer (FU/2RY 25-16POT) (included in the tag-out list and located in cubicle 25-14), noted the "25-16" in the Equipment ID and were in a mindset that the fuses they observed were from the equipment they were about to manipulate. The equipment ID for the PT drawer in cubicle 25-16 was not labeled and the worker believed the fuses were for the PT drawer. However, this PT drawer was actually FU/B25 25-16POT which senses power to Bus 25.
As a result, when the PT drawer above Breaker 25-16 was opened, degraded voltage, undervoltage, and loss of voltage signals were detected and the Load Sequencer proceeded with the voltage restoration program. This program gives a trip signal to all source breakers. Upon receipt of the trip signal, breaker 25 "CT12 Source to Bus 25" opened as designed and the Load Sequencer performed as expected to re-energize the bus via the D5 EOG output breaker (25-2) approximately 8 seconds later. However, because the PT Drawer remained open after the completion of sequencing, voltage restoration to Bus 25 was not indicated to the Load Sequencer. The Load Sequencer then opened EOG D5 output breaker BKR 25-2 as designed. With no power to Bus 25, Bus 25 was inoperable. Operators were able to manually close the D5 EDG output breaker 25-2 to re-energize Bus 25. All equipment functioned as designed.
Bus 25 was re-energized from EOG D5. Technical Specification (TS) 3.8.9. Condition A, Distribution Systems-Operating was exited on May 17, 2018 at 12:07 (52 minutes). Bus 25 was restored to offsite source on May 17, 2018 at 15:30. Operations shutdown and secured EOG D5 on May 17, 2018 at 16:44.
This event was reported on May 17, 2018 at 18:33 CDT, (Event Notification53408), in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the EOG.
EVENT ANALYSIS
EDG, is a backup to the normal standby AC power supply, it is capable of sequentially starting and supplying the power requirements to one of the redundant sets of engineered safety features for the associated reactor Unit. In addition, in the event of a station blackout (880) condition, each EOG is capable of sequentially starting and supplying the power requirements of the hot shutdown (Mode 3, Hot Standby in TS) loads for its unit, as well as the essential loads of the 1 EIIS System Code - EK 2 EIIS System Code - EA blacked out unit, through the use of manual bus tie breakers interconnecting the 4kV Buses.
NRC FORM 3668 (04-2017)
Page 2 of 5 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3.for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3D
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LER NUMBER YEAR Prairie Island Nuclear Generating Plant 05000-306 Unit 2 2018 SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 Plant management determined that the work could be performed online and removed the modification for the Open Phase project from the 2R30 outage scope. The risk assessment, job planning and preparation of the work order operation allowed the workers to enter the field with an approved work order and clearance that was inadequate for the required work. Reviews, consultations and walkdowns failed to recognize that the work order activities placed the workers in the immediate vicinity of energized 4kV equipment that interfered with the proposed cable routing per the design drawing.
Adequate cable routing detail was not included in the work order because the cubicle internals were not considered in the planning walkdown. The work order was planned at risk and completed prior to the approval of PT design. This lack of detail contributed to a less than adequate understanding of the scope of work by the Operations Planner when completing the clearance tag-out and plant impact statement. The Operations Planner did not identify the clearance as "exceptional" or perform a walkdown to identify all hazards associated with the work.
A walkdown should have been performed and the isolation should have been made both complex and exceptional in accordance with the fleet tagging procedure. A clearance is considered exceptional when the normal requirements of the tagging process cannot be fully implemented. Permission to work must be approved by Operations Management and documented in the clearance order. An explanation for the reason the clearance is exceptional and the compensatory actions stated. A face to face brief with Operations is required prior to signing the clearance. If energy is discovered during the zero energy test, stop work and contact Operations.
Operators responded to the alarm response procedures addressing the Bus 25 undervoltage condition and transitioned to re-energizing the 4kV, Bus 25 per the Abnormal Operating Procedure (AOP) using D5 EOG. The PT fuse drawer was verified to be re-installed and applicable relays reset on the Bus 25 Load Sequencer. The Bus 25 Load Sequencer was returned to service per the associated AOP. Operators shutdown EOG D5 per Operating Procedures. This event is being reported under 10 CFR 50. 73(a)(2)(iv)(A) as an event that resulted in valid/automatic actuation of an EOG.
Bus 25 is required to be operable in modes 1 through 4 by TS 3.8.9, Distribution Systems - Operating, and in modes 5 and 6 when required by TS 3.8.10, Distribution Systems - Shutdown. The Bus 25 Voltage Instrumentation is required to be operable by TS 3.3.4, 4kV Safeguards Bus Voltage Instrumentation, in modes 1 through 4 or when the associated EDG is required to be operable by LCO 3.8.2, AC Sources - Shutdown.
SAFETY SIGNIFICANCE
There were no radiological, environmental, or industrial impacts associated with the auto-start of EOG D5, and the health and safety of the public were not affected. The plant was placed in an unplanned TS under 3.8.1 Condition D, for having both EDG D5 and 2RY (Offsite AC source) were inoperable. Bus 25 was de-energized requiring entry into TS 3.8.9 Condition A, Distribution Systems-Operating on May 17, 2018 at 11 :15. Operators were able to manually close the EOG D5 output breaker to re-energize Bus 25. Bus 25 was re-energized from EOG D5. TS 3.8.9. Condition A, was exited on May 17, 2018 at 12:07 (52 minutes). Bus 25 was restored to offsite source on May 17, 2018 at 15:30. Operations shutdown and secured EOG D5 on May 17, 2018 at 16:44.
There was a momentary loss of component cooling on the loss of 21 ComponentCooling (CC) pump due to low pressure in the CC system. The 22 CC pump auto started as designed and restored system pressure with a minimum impact on the CC system.
This event was reportable per 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the EOG.
The auto-start of the EOG D5 did not challenge nuclear safety as all plant systems responded as designed. This event did not affect Bus 26 and there was no auto start of EOG D6. Both Bus 26 and EOG D6 were operable during this event.
As a result, there was no loss of safety function. Page 3 of 5 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readinq-rm/doc-collections/nuregs/staff/sr1022/r3[)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the Information collection.
- 3. LER NUMBER Prairie Island Nuclear Generating Plant Unit 2 05000-306 YEAR 2018 SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00
- 4. Revise supplemental oversight procedure to implement a review committee for the Supplemental oversight plans.
PREVIOUS SIMILAR EVENTS
A review of the Prairie Island LE Rs for the past five found no other similar events. Page 5 of 5