ML24053A151

MD 8.3 24-001- Farley Unit 2 Manual Trip- Loss of Letdown

ML24053A151
Person / Time
Site:	Farley
Issue date:	02/16/2024
From:	Mark Franke Division Reactor Projects II
To:
References
MD 8.3 24-001
Download: ML24053A151 (9)

Text

Issue Date: 10/28/11 E1-1 0309 Decision Documentation for Reactive Inspection (Deterministic and Risk Criteria Analyzed)

MD 8.3 24-001 PLANT: Farley Unit 2 EVENT DATE: Feb.16, 2024 EVALUATION DATE: Feb. 16, 2024 Brief Description of the Significant Operational Event or Degraded Condition:

On February 16, 2024, at approximately 00:35 CST, control room operators entered AOP-16, Malfunction due to Loss of Letdown after they received multiple alarms for the loss of normal letdown and charging flow. Water level in the volume control tank started decreasing because vital DC breaker (LA08) unexpectedly opened which resulted in a partial loss of various vital DC loads including normal reactor coolant system (RCS) make-up (charging) and letdown. The valves for normal charging and letdown failed closed when power was loss to the solenoids. The operators also entered AOP-6 Loss of Instrument Air because the instrument air (IA) supply valve to containment went closed. The loss of IA to containment was also a result of the partial loss of vital DC power on unit 2. The power operated relief valves (PORV) were used to maintain pressurizer pressure because pressurizer spray valves (air operated-fail close) were unavailable for pressure control due to the loss of IA to containment. At approximately 00:48 CST, Farley unit 2 was manually tripped from 100% power due to the loss of normal reactor makeup and letdown. VCT water level was at approximately ten percent at the time of the trip. After the trip, operators verified that RCS makeup auto swapped to the reactor water storage tank (RWST) at five percent. The unit transitioned to Mode 3 (hot standby) with decay heat being removed using auxiliary feedwater and atmospheric relief valves. The condenser could not be used for decay heat removal because the steam dumps were not available due the loss of vital DC. Following the trip, operators entered AOP-4.1 Abnormal RCP Seal Leakage and secured the B RCP (reactor coolant pump) after receiving a control room alarm (DC1) for

1. 1 seal leak off low flow. The A and C RCPs remained in service to maintain normal RCS circulation. At approximately 01:45 CST the plant entered Technical Specification (TS) 3.4.9 condition A (Pressurizer Water Level) because the pressurizer level went above the TS limit (92 percent). At approximately 02:09 CST the operators restored instrument air to containment by blocking open the supply valve. At approximately 04:32 CST the licensee reestablished normal makeup and letdown to the RCS after closing the vital DC breaker. At 4:54 CST Farley exited TS 3.4.9 because pressurizer level was 63.9 percent and decreasing.

The senior resident inspector responded to the control room following the reactor trip to monitor plant conditions. The residents will continue monitor the licensees investigation and will review the licensees post trip review. The licensee has preliminarily determined that the DC breaker had a degraded sigma trip device internal to the breaker which caused premature opening in response to high current. The licensee replaced the degraded LA08 breaker with a new breaker and restarted unit 2.

Issue Date: 10/28/11 E1-2 0309 DETERMINISTIC CRITERIA

a. Involved operations that exceeded, or were not included in, the design bases of the facility N

Remarks: Did not involve operations that exceeded or were not included in the design bases.

b. Involved a major deficiency in design, construction, or operation having potential generic safety implications N

Remarks: Did not involve a major deficiency having potential generic safety implications.

c. Led to a significant loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of a nuclear reactor N

Remarks: Did not lead to a significant loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of the reactor.

d. Led to the loss of a safety function or multiple failures in systems used to mitigate an actual event.

N Remarks: Did not lead to the loss of a safety function or multiple failures in systems used to mitigate an actual event.

e. Involved possible adverse generic implications N

Remarks: Did not involve a possible adverse generic implication.

f. Involved significant unexpected system interactions N

Remarks: Did not involve a significant unexpected system interaction. All systems responded as expected.

g. Involved repetitive failures or events involving safety-related equipment or deficiencies in operations.

N Remarks: Did not involve repetitive failures or deficiencies in operations. This event did involve the failure of a safety related vital DC breaker. The failure of the vital DC breaker LA08 caused the loss of normal makeup to the RCS and letdown. This also caused the loss of instrument air to containment and the inability to use normal pressure control in the pressurizer via the pressurizer spray valves. The failure of DC breaker also prevented operators from using the steam dumps for decay heat removal following the reactor trip. The licensee has preliminarily determined that the DC breaker had a degraded sigma trip device internal to the breaker which caused premature opening in response to high current. The degraded LA08 breaker was replaced with a new breaker. Routine

Issue Date: 10/28/11 E1-3 0309 baseline inspection follow-up is recommended to monitor the licensees investigation and review the licensees post trip review.

h. Involved questions or concerns pertaining to licensee operational performance N

Remarks: Did not involve concerns pertaining to licensee operational performance.

CONDITIONAL RISK ASSESSMENT RISK ANALYSIS BY: N/A DATE: February 16, 2024 Brief Description of the Basis for the Assessment (may include assumptions, calculations, references, peer review, or comparison with licensees results):

N/A There were no questions that had YES answers and therefore, no risk analysis is required.

RESPONSE DECISION USING THE ABOVE INFORMATION AND OTHER KEY ELEMENTS OF CONSIDERATION AS APPROPRIATE, DOCUMENT THE RESPONSE DECISION TO THE EVENT OR CONDITION, AND THE BASIS FOR THAT DECISION DECISION AND DETAILS OF THE BASIS FOR THE DECISION:

Residents responded to the site under IP 71153. Routine baseline inspection will be performed as needed.

BRANCH CHIEF REVIEW/DATE: Alan Blamey DIVISION DIRECTOR REVIEW/DATE: Mark Franke ADAMS ACCESSION NUMBER:ML24053A151 EVENT NOTIFICATION REPORT NUMBER (as applicable):

E-mail to NRR_Reactive_Inspection@nrc.gov Signed by Blamey, Alan on 02/22/24 Signed by Franke, Mark on 02/26/24

Issue Date: 10/28/11 E1-4 0309 - Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)

Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)

PLANT: Farley Unit 2 EVENT DATE: Feb. 16, 2024 EVALUATION DATE: Feb 16, 2024 Brief Description of the Significant Operational Event or Degraded Condition:

See Above REACTOR SAFETY Y/N IIT Deterministic Criteria Led to a Site Area Emergency N

Remarks: No EAL criteria were exceeded.

Exceeded a safety limit of the licensee's technical specifications N

Remarks: No safety limit was exceeded.

Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission N

Remarks: Did not involve complex or unique circumstances.

Y/N SI Deterministic Criteria Significant failure to implement the emergency preparedness program during an actual event, including the failure to classify, notify, or augment onsite personnel N

Remarks: No EAL thresholds were exceeded that would have required execution of the emergency preparedness program.

Involved significant deficiencies in operational performance which resulted in degrading, challenging, or disabling a safety system function or resulted in placing the plant in an unanalyzed condition for which available risk assessment methods do not provide an adequate or reasonable estimate of risk.

N Remarks: Did not involve significant deficiencies in operational performance.

Issue Date: 10/28/11 E1-5 0309 RADIATION SAFETY Y/N IIT Deterministic Criteria Led to a significant radiological release (levels of radiation or concentrations of radioactive material in excess of 10 times any applicable limit in the license or 10 times the concentrations specified in 10 CFR Part 20, Appendix B, Table 2, when averaged over a year) of byproduct, source, or special nuclear material to unrestricted areas N

Remarks: There was no significant radiological release.

Led to a significant occupational exposure or significant exposure to a member of the public. In both cases, significant is defined as five times the applicable regulatory limit (except for shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

N Remarks: There was no significant occupational exposure or significant exposure.

Involved the deliberate misuse of byproduct, source, or special nuclear material from its intended or authorized use, which resulted in the exposure of a significant number of individuals N

Remarks: Did not involve the deliberate misuse of byproduct, source or special nuclear material.

Involved byproduct, source, or special nuclear material, which may have resulted in a fatality N

Remarks: Did not result in a fatality.

Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission N

Remarks: Did not involve complex or unique circumstances.

Y/N AIT Deterministic Criteria Led to a radiological release of byproduct, source, or special nuclear material to unrestricted areas that resulted in occupational exposure or exposure to a member of the public in excess of the applicable regulatory limit (except for shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

N Remarks: Did not lead to a radiological release of byproduct, source, or special nuclear material to unrestricted areas.

N Involved the deliberate misuse of byproduct, source, or special nuclear material from its intended or authorized use and had the potential to cause an exposure of greater than 5 rem to an individual or 500 mrem to an embryo or fetus

Issue Date: 10/28/11 E1-6 0309 Remarks: This was not the result of deliberate misuse of nuclear material.

Involved the failure of radioactive material packaging that resulted in external radiation levels exceeding 10 rads/hr or contamination of the packaging exceeding 1000 times the applicable limits specified in 10 CFR 71.87 N

Remarks: Did not result in the failure of radioactive material packaging.

Involved the failure of the dam for mill tailings with substantial release of tailings material and solution off site N

Remarks: Did not result in the failure of a mill tailing dam.

Y/N SI Deterministic Criteria May have led to an exposure in excess of the applicable regulatory limits, other than via the radiological release of byproduct, source, or special nuclear material to the unrestricted area; specifically occupational exposure in excess of the regulatory limits in 10 CFR 20.1201 exposure to an embryo/fetus in excess of the regulatory limits in 10 CFR 20.1208 exposure to a member of the public in excess of the regulatory limits in 10 CFR 20.1301 N

Remarks: Did not lead to an exposure in excess of the applicable regulatory limits.

May have led to an unplanned occupational exposure in excess of 40 percent of the applicable regulatory limit (excluding shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

N Remarks: Did not lead to an unplanned occupational exposure.

Led to unplanned changes in restricted area dose rates in excess of 20 rem per hour in an area where personnel were present, or which is accessible to personnel N

Remarks: Did not lead to unplanned changes in restricted area dose rates in excess of 20 rem per hour in an area where personnel were present, or which is accessible to personnel.

Led to unplanned changes in restricted area airborne radioactivity levels in excess of 500 DAC in an area where personnel were present or which is accessible to personnel and where the airborne radioactivity level was not promptly recognized and/or appropriate actions were not taken in a timely manner N

Remarks: Did not lead to unplanned changes in restricted area airborne radioactivity levels in excess of 500 DAC.

Issue Date: 10/28/11 E1-7 0309 Led to an uncontrolled, unplanned, or abnormal release of radioactive material to the unrestricted area for which the extent of the offsite contamination is unknown; or, that may have resulted in a dose to a member of the public from loss of radioactive material control in excess of 25 mrem (10 CFR 20.1301(e)); or, that may have resulted in an exposure to a member of the public from effluents in excess of the ALARA guidelines contained in Appendix I to 10 CFR Part 50 N

Remarks: Did not lead to a release of radioactive material.

Led to a large (typically greater than 100,000 gallons), unplanned release of radioactive liquid inside the restricted area that has the potential for groundwater, or offsite, contamination N

Remarks: Did not result in the unplanned release that has the potential for groundwater, or offsite contamination.

Involved the failure of radioactive material packaging that resulted in external radiation levels exceeding 5 times the accessible area dose rate limits specified in 10 CFR Part 71, or 50 times the contamination limits specified in 49 CFR Part 173 N

Remarks: Did not result in the failure of radioactive material packing.

Involved an emergency or non-emergency event or situation, related to the health and safety of the public or on-site personnel or protection of the environment, for which a 10 CFR 50.72 report has been submitted that is expected to cause significant, heightened public or government concern N

Remarks: Did not involve an emergency or non-emergency event or situation, related to the health and safety of the public or on-site personnel or protection of the environment.

SAFEGUARDS/SECURITY Y/N IIT Deterministic Criteria Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission N

Remarks: This is not considered a complex or unique issue.

Failure of licensee significant safety equipment or adverse impact on licensee operations as a result of a safeguards-initiated event (e.g., tampering).

N Remarks: The event did not involve tampering.

Issue Date: 10/28/11 E1-8 0309 Actual intrusion into the protected area N

Remarks: Did not involve an intrusion into the protected area.

Y/N AIT Deterministic Criteria Involved a significant infraction or repeated instances of safeguards infractions that demonstrate the ineffectiveness of facility security provisions N

Remarks: Did not involve safeguards.

Involved repeated instances of inadequate nuclear material control and accounting provisions to protect against theft or diversions of nuclear material N

Remarks: Did not involve inadequate nuclear material control.

Confirmed tampering event involving significant safety or security equipment N

Remarks: The event did not involve tampering.

Substantial failure in the licensees intrusion detection or package/personnel search procedures which results in a significant vulnerability or compromise of plant safety or security N

Remarks: Was not a failure of the intrusion detection or package/personnel search procedures.

Y/N SI Deterministic Criteria Involved inadequate nuclear material control and accounting provisions to protect against theft or diversion, as evidenced by inability to locate an item containing special nuclear material (such as an irradiated rod, rod piece, pellet, or instrument)

N Remarks: Did not involve nuclear material control and accounting.

Involved a significant safeguards infraction that demonstrates the ineffectiveness of facility security provisions N

Remarks: Did not involve safeguards.

Confirmation of lost or stolen weapon N

Remarks: Did not involve the loss of a weapon.

Unauthorized, actual non-accidental discharge of a weapon within the protected area N

Remarks: Did not involve a weapon.

Substantial failure of the intrusion detection system (not weather related)

N Remarks: Did not involve the intrusion detection system.

Issue Date: 10/28/11 E1-9 0309 Failure to the licensees package/personnel search procedures which results in contraband or an unauthorized individual being introduced into the protected area N

Remarks: Did not involve the package/personnel search procedures.

Potential tampering or vandalism event involving significant safety or security equipment where questions remain regarding licensee performance/response or a need exists to independently assess the licensee=s conclusion that tampering or vandalism was not a factor in the condition(s) identified N

Remarks: Did not involve tampering.

RESPONSE DECISION USING THE ABOVE INFORMATION AND OTHER KEY ELEMENTS OF CONSIDERATION AS APPROPRIATE, DOCUMENT THE RESPONSE DECISION TO THE EVENT OR CONDITION, AND THE BASIS FOR THAT DECISION DECISION AND DETAILS OF THE BASIS FOR THE DECISION:

Residents responded to the site under IP 71153. Routine baseline inspection will be performed as needed.

BRANCH CHIEF REVIEW/DATE: Alan Blamey DIVISION DIRECTOR REVIEW/DATE: Mark Franke ADAMS ACCESSION NUMBER: ML24053A151 EVENT NOTIFICATION REPORT NUMBER (as applicable):

E-mail to NRR_Reactive_Inspection@nrc.gov Signed by Blamey, Alan on 02/22/24 Signed by Franke, Mark on 02/26/24