ML24157A339
| ML24157A339 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/05/2024 |
| From: | Horton T Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08807-TAH/JJM LER 2024-001-00 | |
| Download: ML24157A339 (1) | |
Text
Todd A. Horton Senior Vice President Nuclear Regulatory & Oversight
Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7605 Tel: 623.393.6418 102-08807-TAH/JJM June, 2024
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station Unit 3 Docket No. STN 50-530 /Renewed License No. NPF-74 Licensee Event Report 2024-001-00
Enclosed, please find the Licensee Event Report (LER) 50-530/2024-001-00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER reports an event in which Unit 3 had a loss of power to both channels of the Boron Dilution Alarm Monitoring System with subsequent Technical Specification Violation of 3.3.12.
In accordance with 10 CFR 50.4, copies of this LER are being forwarded to the Nuclear Regulatory Commission (NRC) Regional Office, NRC Region IV, and the Senior Resident Inspector.
No new commitments are being made to the NRC by this letter. Should you need further information regarding this submittal, please contact Matthew S. Cox, Department Leader, Nuclear Regulatory Affairs, at (623) 393-5753.
Sincerely, Horton, Todd Digitally signed by Horton, Todd (Z10098)
(Z10098) Date: 2024.06.05 11:25:26 -07'00'
TAH/JJM/cr
Enclosure:
Unit 1 Licensee Event Report 2024-001-00 cc: J. Monninger NRC Region IV Regional Administrator W. T. Orders NRC NRR Project Manager for PVNGS L. N. Merker NRC Senior Resident Inspector for PVNGS
A member of the STARS Alliance, LLC
Callaway
- Diablo Canyon
- Palo Verde
- Wolf Creek ENCLOSURE
Unit 2 Licensee Event Report 2024-001-00 NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons
learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U. S. Nuclear Regulatory (See Page 2 for required number of digits/characters for each block) Commission, Washington, DC 20555-0001, or by email to Infocollects.Resource@nrc.gov, and the OMB reviewer at: OMB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory (See NUREG-1022, R.3 for instruction and guidance for completing this form Commission, 725 17th Street NW, Washington, DC 20503. The NRC may not conduct or sponsor, and a person is http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) not required to respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid OMB control number.
- 1. Facility Name 050 2. Docket Number 3. Page Palo Verde Nuclear Generating Station (PVNGS) Unit 3 00530 31 OF 052
- 4. Title Inoperable Boron Dilution Alarm System(BDAS) with Technical Specification Violation
- 5. Event Date 6. LER Number 7. Report Date 8. Other Facilities Involved
Month Day Year Year Sequential Revision Month Day Year Facility Name Docket Number Number No. 050
04 09 2024 2024 001 00 06--052024Facility Name052Docket Number
- 9. Operating Mode 10. Power Level 50
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 10 CFR Part 20 20.2203(a)(2)(vi) 10 CFR Part 50 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 73.1200(a)
20.2201(b) 20.2203(a)(3)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 73.1200(b)
20.2201(d) 20.2203(a)(3)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 73.1200(c)
20.2203(a)(1) 20.2203(a)(4) 50.36(c)(2) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 73.1200(d)
20.2203(a)(2)(i) 10 CFR Part 21 50.46(a)(3)(ii) 50.73(a)(2)(v)(A) 10 CFR Part 73 73.1200(e)
20.2203(a)(2)(ii) 21.2(c) 50.69(g) 50.73(a)(2)(v)(B) 73.77(a)(1) 73.1200(f)
20.2203(a)(2)(iii) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) 73.77(a)(2)(i) 73.1200(g)
20.2203(a)(2)(iv) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D) 73.77(a)(2)(ii) 73.1200(h)
20.2203(a)(2)(v) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)
OTHER (Specify here, in abstract, or NRC 366A).
- 12. Licensee Contact for this LER
Licensee Contact Phone Number (Include area code)
Matthew S. Cox, Department Leader Nuclear Regulatory Affairs (623) 393-5753
- 13. Complete One Line for each Component Failure Described in this Report
Cause System Component Manufacturer Reportable to IRIS Cause System Component Manufacturer Reportable to IRIS
- 14. Supplemental Report Expected Month Day Year
- 15. Expected Submission Date No 08 23 2024Yes (If yes, complete 15. Expected Submission Date)
- 16. Abstract (Limit to 1326 spaces, i.e., approximately 13 single-spaced typewritten lines)
On 4/9/2024 at 1100, while in a refueling outage at zero percent power, Unit 3 control room experienced an unplanned partial loss of power to annunciator windows in the Control Room due to a planned down power of an elec trical power supply for the performance of maintenance. The contr ol room entered Technical Specification (TS ) Limited Condition for Oper ation (LCO) 3.3.12 Boron Dilution Alarm System (BDAS) Condition A and B. Personnel from the Chem istry Department obtained samples until power was restored and the BDAS returned to OPERABLE 4/9/2024 at 1233 when the TS LCO was exited.
On 4/13/2024 at approximately 0630, it was discovered that the sample was obtained from an incorrect sample location.
Further TS LCO 3.3.12 Condition B was not met as redundant sam ples were not taken. The NRC resident inspec tors were notified of this event.
The investigation is on going and a supplemental LER will be submitted once complete.
No similar event has occurred at PVNGS in the last three years.
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments LICENSEE EVENT REPORT (LER) regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U. S.
Nuclear Regulatory Commission, Washington, DC 20555-0001, or by email to CONTINUATION SHEET Infocollects.Resource@nrc.gov, and the OMB reviewer at: OMB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, (See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503. The NRC may not conduct or sponsor, and a person is not required to http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid OMB control number.
- 1. FACILITY NAME 2. DOCKET NUMBER 3. LER NUMBER 050 YEAR SEQUENTIAL REV Palo Verde Nuclear Generating Station NUMBER NO.
(PVNGS) Unit 3 00530 2024 001 00052 --
NARRATIVE All times are Mountain Standard Time and approximate unless otherwise indicated.
- 1. REPORTING REQUIREMENT(S):
This Licensee Event Report is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B): Any operation or condition which was prohibited by the plant's Technical Specification. TS LCO 3.3.12 Conditions A and B were entered on 4/9/2024 and required actions were not met.
- 2. DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S):
Non-Class 125 VDC (EIIS:EE) and Non-Class 1E instrument 120 VAC (EIIS:EE) provides primary and alternate power, respectively, to the control room Annunciators on boards 2, 3, 4, 6, and 7(EIIS:IB). Board 4 contains an alarm point for the BDAS (EIIS:IG) monitoring alarm. BDAS provides two independent and redundant channels (Channels 1 and 2) to ensure detection and alarm of a boron dilution event while in hot standby, hot shutdown, cold shutdown, and refueling, Modes 3 through 6, respectively.
The BDAS is credited in the Updated Final Safety Analysis Report (UFSAR) Chapter 15 safety analysis with alerting operators to an inadvertent boron dilution 15 minutes prior to achieving criticality assuming the maximum dilution rate while in modes 3, 4, and 5, and within 30 minutes in Mode 6. This allows the operator time to diagnose and terminate the boron dilution prior to criticality.
The BDAS receives and monitors two neutron flux signals (one per BDAS channel) from the startup channel nuclear instrumentation. When these neutron flux signals increase during shutdown to equal to or greater than the calculated alarm set-point, alarm signals are generated. The BDAS provides two separate and independent alarm signals (one signal per BDAS channel) to the plant annunciation system upon determination of a boron dilution event. Each alarm signal will cause the annunciator window "Possible Inadvertent Boron Dilution" to alarm, which then relays an alarm to the control room via the Annunciator on Board 4.
- 3. INITIAL PLANT CONDITIONS:
On 4/9/2024, Palo Verde Unit 3 was in Mode 5 Cold Shutdown at 0 percent power. Unit 3 was in Refueling Outage 3R24.
Reactor Coolant System (RCS) was intact with RCS temperature at 98.2 degrees Fahrenheit and RCS pressure at 78 pounds per square inch absolute (PSIA).
- 4. EVENT DESCRIPTION:
On 4/9/2024 Unit 3 was in a Refueling Outage and planned maintenance was being performed on the alternate power supply. Since the normal power supply was inoperable, the control room experienced an unanticipated loss of power to the annunciators on boards 2, 3, 4, 6, and 7 at 1100. Operations then declared both channels of BDAS inoperable due to the loss of annunciation and entered TS LCO 3.3.12 Conditions A and B. The Operations Department contacted the Chemistry Department to get the required boron samples to meet TS LCO requirements. This required collection of two independent RCS boron samples. At 1233, power was restored and the TS LCO conditions were exited.
NRC FORM 366A (04-02-2024) Page 2 3of NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments LICENSEE EVENT REPORT (LER) regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U. S.
Nuclear Regulatory Commission, Washington, DC 20555-0001, or by email to CONTINUATION SHEET Infocollects.Resource@nrc.gov, and the OMB reviewer at: OMB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, (See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503. The NRC may not conduct or sponsor, and a person is not required to http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid OMB control number.
- 1. FACILITY NAME 2. DOCKET NUMBER 3. LER NUMBER 050 YEAR SEQUENTIAL REV Palo Verde Nuclear Generating Station NUMBER NO.
(PVNGS) Unit 3 00530 2024 001 00052 --
NARRATIVE On 4/13/2024, the Chemistry Supervisor was reviewing the samples and realized that the samples were obtained from a different sample point than specified in plant procedures for the conditions of the RCS system being in Shutdown Cooling (SDC) at the time of the event. Furthermore, the Chemistry Supervisor noticed the samples were not obtained redundantly to validate boron concentration as required by TS LCO 3.3.12 Condition B. The supervisor contacted the control room of the findings.
Units 1 and 2 were unaffected by the event and both remained in MODE 1 at 100% power.
- 5. ASSESSMENT OF SAFETY CONSEQUENCES:
Operability of the BDAS channels are necessary to meet the assumptions of the safety analyses to mitigate the consequences of an inadvertent boron dilution event as described in the UFSAR Chapter 15, Revision 22. Unit 3 was in MODE 5 on 4/9/2024 when both channels of the BDAS became inoperable. There were no MODE changes and no inadvertent boron dilutions during the time BDAS was inoperable.
An investigation of the event is in progress. Information on the safety consequences will be provided in a supplement to this LER.
- 6. CAUSE OF THE EVENT:
The investigation of the specific causes of this event is in progress. This LER will be supplemented when the investigation is complete.
- 7. CORRECTIVE ACTIONS:
Immediate actions included the restoration of power supplies to the annunciator panels which subsequently restored BDAS to OPERABLE status.
Corrective actions for this event are still being evaluated and will be identified in the supplement to this LER.
- 8. PREVIOUS SIMILAR EVENTS:
No similar events have occurred in the prior three years.
NRC FORM 366A (04-02-2024) Page 3 3of