ML22063A703

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Automatic Reactor Trip Due to High Reactor Coolant System
ML22063A703
Person / Time
Site: Calvert Cliffs 
Issue date: 03/03/2022
From:
Constellation Energy Generation
To:
Office of Nuclear Reactor Regulation
Shared Package
ML22063A701 List:
References
LER 2022-001-00
Download: ML22063A703 (4)
v • d • e


Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (08-2020)

LICENSEE EVENT REPORT (LER)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 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 estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U.S.

Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and the OMB reviewer at: OMB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk ail: oira_submission@omb.eop.gov. The NRC may not conduct or sponsor, and a person is 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 Calvert Cliffs Nuclear Power Plant, Unit 2
2. Docket Number 05000318
3. Page 1 OF 4
4. Title Unit 2 Automatic Reactor Trip Due to High Reactor Coolant System Pressure
5. Event Date
6. LER Number
7. Report Date
8. Other Facilities Involved Month Day Year Year Sequential Number Revision No.

Month Day Year Facility Name Docket Number 05000 01 03 2022 2022 - 001 -

00 03 03 2022 Facility Name Docket Number 05000

9. Operating Mode 1
10. Power Level 100
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) 50.36(c)(2) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2201(b) 20.2203(a)(3)(i) 50.46(a)(3)(ii) 50.73(a)(2)(v)(A) 10 CFR Part 73 20.2201(d) 20.2203(a)(3)(ii) 50.69(g) 50.73(a)(2)(v)(B) 73.71(a)(4) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) 73.71(a)(5) 20.2203(a)(2)(i) 10 CFR Part 21 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D) 73.77(a)(1)(i) 20.2203(a)(2)(ii) 21.2(c) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 73.77(a)(2)(i) 20.2203(a)(2)(iii) 10 CFR Part 50 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 73.77(a)(2)(ii) 20.2203(a)(2)(iv) 50.36(c)(1)(i)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(v) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)

OTHER (Specify here, in abstract, or NRC 366A).

12. Licensee Contact for this LER Licensee Contact Art Simpson, Principal Regulatory Engineer Phone Number (Include area code) 410 495-6913
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 B

TG TD W120 N

14. Supplemental Report Expected
15. Expected Submission Date Month Day Year No Yes (If yes, complete 15. Expected Submission Date)
16. Abstract (Limit to 1560 spaces, i.e., approximately 15 single-spaced typewritten lines)

On January 3, 2022, with the Unit 2 reactor operating at 100 percent power, a severe weather induced phase-to-ground fault occurred on a transformer feeder breaker from a 500 kilovolt switchyard bus, causing an electrical transient that affected frequency of the bus and Unit 2 main turbine speed. Main turbine speed increased above the setpoint for the Load Drop Anticipator function of the turbine control system, resulting in closure of the turbine control and intercept valves. With the valves travelling closed, reactor coolant pressure increased, and the Unit 2 reactor automatically tripped on high reactor coolant pressure. The cause was the configuration of the megawatt transducer circuit for the Unit 2 main turbine control system would activate the Load Drop Anticipator function of the system at turbine speeds for zero percent power instead of full power. Corrective action included a tuning change to the main turbine control system to activate the LDA function at the intended full power value of 1854 revolutions per minute while at full reactor power. Currently, plans are in place to replace the megawatt transducers in a future outage.

(See Page 3 for required number of digits/characters for each block)

(See NUREG1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (04-2018)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME
2. DOCKET NUMBER
3. LER NUMBER Calvert Cliffs Nuclear Power Plant, Unit 2

05000318 YEAR SEQUENTIAL NUMBER REV NO.

2022 001 00 NARRATIVE NRC FORM 366A (08-2020)

Page 2 of 4 PLANT AND SYSTEM IDENTIFICATION Calvert Cliffs Nuclear Power Plant, Unit 2, is a Combustion Engineering Pressurized Water Reactor with a licensed maximum power level of 2737 megawatts thermal. The Energy Industry Identification System code used in the text is identified as [TG].

A. CONDITION PRIOR TO EVENT Unit: 2 Date: January 3, 2022 Power level: 100 Mode: 1 The megawatt transducer circuit [TD] for the Unit 2 main turbine control system [TG] was out-of-service and contributed to this event.

B. DESCRIPTION OF EVENT On January 3, 2022, with the Unit 2 reactor operating at 100 percent power, a severe weather induced phase-to-ground fault occurred on a transformer feeder breaker [BKR] from the 500-kilovolt switchyard Red Bus [BU] B phase, causing an electrical transient that affected frequency of the bus and Unit 2 main turbine speed. At that time, the megawatt transducers installed in the megawatt transducer circuit for the Unit 2 main turbine Ovation control system were configured to activate the Load Drop Anticipator (LDA) function of the system if main turbine speed reached 1809 revolutions per minute (RPM) with the reactor at 100 percent power. The correct configuration of the megawatt transducer circuit should activate the LDA function of the system if main turbine speed reaches 1809 RPM at zero percent reactor power and if main turbine speed reaches 1854 RPM at 100 percent reactor power. As a result of the transient on January 3, 2022, Unit 2 main turbine speed increased above 1809 RPM to 1810 RPM and initiated the Load Drop Anticipator (LDA) function in the main turbine Ovation controls. Once the LDA was latched, the turbine control valves [FCV] and intercept valves [V] were forced shut to prevent a possible turbine overspeed condition. With the valves traveling closed, reactor coolant system (RCS)

[AB] pressure began to rise, resulting in an automatic Unit 2 reactor trip on high RCS pressure.

C. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES January 3, 2022 12:23:45 - Weather induced fault on switchyard breakers causes spike on turbine speed.

12:23:46 - Load Drop Anticipator actuated on turbine speed at 1809 RPM setpoint. Speed reached1810 RPM.

12:23:52 - Unit 2 automatic reactor trip on high RCS pressure.

12:24:18 - Main turbine generator breakers 61 and 63 open automatically.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (04-2018)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME
2. DOCKET NUMBER
3. LER NUMBER Calvert Cliffs Nuclear Power Plant, Unit 2

05000318 YEAR SEQUENTIAL NUMBER REV NO.

2022 001 00 NARRATIVE NRC FORM 366A (08-2020)

Page 3 of 4 January 5, 2022 16:29 - Unit 2 entered Mode 2.

19:44 - Unit 2 entered Mode 1.

January 6, 2022 01:40 - Tuning change to main turbine Ovation controls system completed.

20:47 - Unit 2 reactor restored to full power.

D. CAUSE OF EVENT The method of discovery for this event was self-revealing and is documented in the sites Corrective Action Program under IR 04469662. The cause of the event was the configuration of the megawatt transducer circuit was not corrected prior to the January 3, 2022 transient. Prior to start-up following the automatic trip, actions were taken to prevent the LDA from actuating during fluctuations like those experienced on January 3, 2022, with the reactor operating at full power. Specifically, a tuning change to the main turbine control system was performed to activate the LDA function at the intended full power value of 1854 revolutions per minute while at full reactor power.

E. SAFETY ANALYSIS The subject event satisfies the criteria in NUREG-1022, Revision 3, for any event or condition that resulted in manual or automatic actuation of any of the systems listed in 10 CFR 50.73 (a)(2)(iv)(B). The systems to which the requirements of 10 CFR 50.73 (a)(2)(iv)(A) apply includes the reactor protection system (RPS) including, reactor trip. The subject event resulted in valid actuation of the RPS, and the actuation did not result from a pre-planned sequence during testing or reactor operation. Therefore, this event is reportable pursuant to 10CFR 50.73(a)(2)(iv)(A).

This event did not result in any actual nuclear safety consequences.

F. CORRECTIVE ACTIONS Required corrective actions have been completed. To prevent the LDA from actuating during fluctuations like those experienced on January 3, 2022, a tuning change to the system was performed to activate the LDA function at the intended full power value of 1854 revolutions per minute while at full reactor power.

Plans are in place to replace the megawatt transducers in a future outage such that the circuit will operate as originally designed.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (04-2018)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME
2. DOCKET NUMBER
3. LER NUMBER Calvert Cliffs Nuclear Power Plant, Unit 2

05000318 YEAR SEQUENTIAL NUMBER REV NO.

2022 001 00 NARRATIVE NRC FORM 366A (08-2020)

Page 4 of 4 G. PREVIOUS OCCURRENCES No previous similar events have occurred at the site within the last five years.

H. COMPONENT FAILURE DATA Component IEEE 803 IEEE805 FUNCTION ID SYSTEM ID Main Turbine Controls Megawatt Transducer Circuit TD TG The Unit 2 main turbine control system manufacturer is Westinghouse.

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