ML24276A069
| ML24276A069 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 09/23/2024 |
| From: | Erin Carfang, Blake Welling Division of Operating Reactors |
| To: | |
| References | |
| MD 8.3 IR 2024003 | |
| Download: ML24276A069 (1) | |
Text
Issue Date: 12/14/23 Encl1-1 0309
- Decision Documentation for Reactive Inspection (Deterministic and Risk Criteria Analyzed)
Decision Documentation for Reactive Inspection (Deterministic and Risk Criteria Analyzed)
PLANT:
FitzPatrick EVENT DATE: 09/23/2024 EVALUATION DATE: 09/23/2024 Brief Description of the Significant Event or Degraded Condition:
On 09/23/2024 at approximately 0720, FitzPatrick experienced a reactor SCRAM due to a turbine control valve closure following a localized grid disturbance. The station preliminary determined the cause of grid disturbance was the Nine Mile Point Unit 2 (NMP2) SCRAM that occurred at nearly the same time. The NMP2 SCRAM occurred due to a high-pressure signal that resulted from a normal plant response to a main generator-turbine trip. The main generator-turbine trip is attributed to an electrical transient caused by the main generator exciter breaker failure at approximately 0720. At this time, both events will be assessed separately.
FitzPatrick operator and plant response to the SCRAM was without complication. All control rods inserted. A subsequent reactor pressure vessel (RPV) low water level (LO-LO at 126) resulted in a group 2 isolation and Reactor Core Isolation Cooling (RCIC) and High-Pressure Coolant Injection (HPCI) initiation. RCIC injected into the reactor momentarily before being secured by reactor operators. There was no injection from HPCI as expected due to rapid RPV water level recovery using the A feed water pump. All ECCS and electrical response was satisfactory due to not reaching any initiation setpoints.
Condensate and feedwater remained available and maintained RPV water level as expected.
Offsite power remained stable and available. The main steam isolation valves remained open and the main condenser was available for decay heat removal and reactor pressure control via the turbine bypass valves.
Review of MVAR data showed small swings following by a large MVAR drop from NMP2 that caused a large demand in NMP1 and FitzPatrick. This demand in MVAR resulted in an overvoltage condition for NMP1 and FitzPatrick. The stations have a breakover diode, which functions as an overvoltage trip associated with the AVR. The overvoltage trip is set at 800V for FitzPatrick and 1200V for NMP1. Additionally, NMP1 has had a generator rewind recently, unlike FitzPatrick, which would show differences in generator capabilities.
Y/N DETERMINISTIC CRITERIA N
Involved operations that exceeded, or were not included in, the design bases of the facility Remarks: No design bases were exceeded during this event N
Involved a major deficiency in design, construction, or operation having potential generic safety implications
Issue Date: 12/14/23 Encl1-2 0309 Remarks: For this event, there was no identified design, construction, or operating having potential generic safety implications.
N Led to a significant loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of a nuclear reactor Remarks: There was no impact or challenge on the integrity of the fuel or primary containment boundary N
Led to the loss of a safety function or multiple failures in systems used to mitigate an actual event Remarks: This event did not lead to loss of a safety function or cause any failures in systems used to mitigate an actual event.
N Involved possible adverse generic implications Remarks: Based on current knowledge of the cause of the event, there are no adverse generic implications.
Y Involved significant unexpected system interactions Remarks: The NMP2 exciter breaker failure led to a SCRAM of NMP2. FitzPatricks localized grid disturbance and time of SCRAM corresponded to NMP2s breaker failure. NMP1, NMP2 and FitzPatrick are co-located. The voltage fault initiated from NMP2 (localized grid disturbance) and a lower set point on the FitzPatrick generator protection relays provide a plausible explanation for the FitzPatrick SCRAM. The plant trip was potentially unexpected based on FSAR Section 8.3.4, Transient Stability Performance at the FitzPatrick Plant, stating, in part, for a loss of NMP2, FitzPatrick's unit remains stable and 345 kv and 115 kv sources remain stable.
N Involved repetitive failures or events involving safety-related equipment or deficiencies in operations Remarks: The event did not involve repetitive failures N
Involved questions or concerns pertaining to licensee operational performance Remarks: Based on current knowledge of the event, there were no questions or concerns pertaining to operational performance.
Issue Date: 12/14/23 Encl1-3 0309 CONDITIONAL RISK ASSESSMENT RISK ANALYSIS BY: David Werkheiser DATE: 9/24/2024 Brief Description of the Basis for the Assessment (may include assumptions, calculations, references, peer review, or comparison with licensees results):
A senior reactor analyst (SRA) evaluated the reactor trip event using the FitzPatrick SPAR model 8.82 and SAPHIRE program version 8.2.11.
The IE-TRANS basic event was set to a probability of 1.0 with all other initiating events set to 0.0. No mitigating systems were out of service. Additionally, test and maintenance basic events were set to zero. The resulting mean conditional core damage probability (CCDP) was estimated at 5E-7 (5% 1E-8, 95% 2E-6).
The dominant core damage sequences involved a reactor trip with failure of offsite electrical power and on-site emergency power, failure of high-pressure injection systems during station blackout conditions, and failure of operators to depressurize to support low pressure injection.
The estimated conditional core damage probability (CCDP) is 5E-7 and places the risk in the range of No Additional Inspection.
Issue Date: 12/14/23 Encl1-4 0309 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:
Table 1, Deterministic Criterion 6, Involved Significant Unexpected Interactions, was met. A risk assessment was performed resulting in the no additional inspection range with a CCDP of 5E-7.
Based on the known facts at this time and risk, no reactive inspection is planned at this time.
Follow up will be through baseline inspection, IP 71153.
BRANCH CHIEF REVIEW:
DIVISION DIRECTOR REVIEW:
ADAMS ACCESSION NUMBER: ML24276A069 EVENT NOTIFICATION REPORT NUMBER (as applicable):
Note: The above tables are provided as examples only. The regions have discretion to modify these tables in their implementing procedures or office instructions.
ERIN CARFANG Digitally signed by ERIN CARFANG Date: 2024.10.02 12:57:16 -04'00' BLAKE WELLING Digitally signed by BLAKE WELLING Date: 2024.10.02 13:17:10 -04'00'
Issue Date: 12/14/23 Encl2-1 0309
- Decision Documentation for Reactive Inspection and Examples (Deterministic-only Criteria Analyzed)
Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)
PLANT: FitzPatrick EVENT DATE: 9/23/24 EVALUATION DATE: 9/23/24 Brief Description of the Significant Event or Degraded Condition:
See description in Enclosure 1 (above)
REACTOR SAFETY Y/N IIT Deterministic Criteria N
Led to a Site Area Emergency Remarks:
N Exceeded a safety limit of the licensee's technical specifications Remarks:
N 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 Remarks:
Y/N SI Deterministic Criteria N
Significant failure to implement the emergency preparedness program during an actual event, including the failure to classify, notify, or augment onsite personnel Remarks:
N 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.
Remarks:
Issue Date: 12/14/23 Encl2-2 0309 RADIATION SAFETY Y/N IIT Deterministic Criteria N/A 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 Remarks:
N/A 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)
Remarks:
N/A 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 Remarks:
N/A Involved byproduct, source, or special nuclear material, which may have resulted in a fatality Remarks:
N/A 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 Remarks:
Y/N AIT Deterministic Criteria N/A 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)
Remarks:
Issue Date: 12/14/23 Encl2-3 0309 N/A 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 Remarks:
N/A 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 Remarks:
N/A Involved the failure of the dam for mill tailings with substantial release of tailings material and solution off site Remarks:
Y/N SI Deterministic Criteria N/A 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 Remarks:
N/A 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)
Remarks:
N/A 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 Remarks:
N/A 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 Remarks:
Issue Date: 12/14/23 Encl2-4 0309 N/A 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 Remarks:
N/A Led to a large (typically greater than 100,000 gallons), unplanned release of radioactive liquid inside the restricted area that has the potential for ground-water, or offsite, contamination Remarks:
N/A 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 Remarks:
N/A 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 Remarks:
Issue Date: 12/14/23 Encl2-5 0309 SAFEGUARDS/SECURITY Y/N IIT Deterministic Criteria N/A 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 Remarks:
N/A Failure of licensee significant safety equipment or adverse impact on licensee operations as a result of a safeguards initiated event (e.g., tampering).
Remarks:
N/A Actual intrusion into the protected area Remarks:
Y/N AIT Deterministic Criteria N/A Involved a significant infraction or repeated instances of safeguards infractions that demonstrate the ineffectiveness of facility security provisions Remarks:
N/A Involved repeated instances of inadequate nuclear material control and accounting provisions to protect against theft or diversions of nuclear material Remarks:
N/A Confirmed tampering event involving significant safety or security equipment Remarks:
N/A 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 Remarks:
Issue Date: 12/14/23 Encl2-6 0309 Y/N SI Deterministic Criteria N/A 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)
Remarks:
N/A Involved a significant safeguards infraction that demonstrates the ineffectiveness of facility security provisions Remarks:
N/A Confirmation of lost or stolen weapon Remarks:
N/A Unauthorized, actual non-accidental discharge of a weapon within the protected area Remarks:
N/A Substantial failure of the intrusion detection system (not weather related)
Remarks:
N/A Failure to the licensees package/personnel search procedures which results in contraband or an unauthorized individual being introduced into the protected area Remarks:
N/A 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 licensees conclusion that tampering or vandalism was not a factor in the condition(s) identified Remarks:
Issue Date: 12/14/23 Encl2-7 0309 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: No deterministic criteria were met. A reactive inspection is not planned, based on the criteria evaluated.
BRANCH CHIEF REVIEW:
DIVISION DIRECTOR REVIEW:
ADAMS ACCESSION NUMBER: ML24276A069 EVENT NOTIFICATION REPORT NUMBER (as applicable):
Note: The above tables are provided as examples only. The regions have discretion to modify these tables in their implementing procedures or office instructions.
ERIN CARFANG Digitally signed by ERIN CARFANG Date: 2024.10.02 12:58:04 -04'00' BLAKE WELLING Digitally signed by BLAKE WELLING Date: 2024.10.02 13:17:44 -04'00'