ML25097A075
| ML25097A075 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 03/31/2025 |
| From: | Jason Schussler, Blake Welling Division of Operating Reactors |
| To: | |
| References | |
| Download: ML25097A075 (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: Nine Mile Point Unit 1 EVENT DATE: 03/30/2025 EVALUATION DATE: 03/31/2025 Brief Description of the Significant Event or Degraded Condition: During plant reassembly and preparation for startup near the end of refueling outage N1R28, Nine Mile Point Unit 1 was shut down with the reactor vessel head tensioned and reactor water level above the reactor head flange. Preparations for reactor coolant system pressure testing, which involved opening the block valves upstream of the electromatic relief valves (ERVs), was commenced. At the same time, the ERV pilot valves were gagged open when they were thought to be in a gagged closed condition. This configuration resulted in the inadvertent establishment of a flow path through the ERVs to the torus when the upstream block valves were opened. As a result, reactor water was inadvertently drained from the vessel through the main steam lines to the torus, lowering level at a rate of 3 in/min. Operators recognized the decreasing water level and isolated the unintentional flow path. Reactor water level dropped approximately 3 feet over approximately 12 minutes and was subsequently restored using a control rod drive pump.
Core cooling remained in service via the shutdown cooling system throughout the event, which relies on suction and discharge paths below the reactor water level in question and was therefore not impacted during the event. Time to boil was approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, and no appreciable heat-up occurred during this event. No other equipment considered significant to the circumstances of this event was impacted or out of service during the event (i.e. offsite power sources, ECCS makeup, etc. were available throughout). Because the inadvertent flow path was through the main steam lines, there was no risk of uncovering fuel as a result of this event.
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 Remarks: For this event, there was no identified design, construction or operation 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. The primary coolant pressure boundary was temporarily opened as part of the activity and was re-established following identification of the drain path. No significant loss of integrity of any barrier occurred.
Issue Date: 12/14/23 Encl1-2 0309 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 and human performance aspects of the event, there are no adverse generic implications.
N Involved significant unexpected system interactions Remarks: There were no significant unexpected system interactions. In the context of the event, all systems functioned as expected. ERVs were able to be closed to appropriately isolate the drain path.
N Involved repetitive failures or events involving safety-related equipment or deficiencies in operations Remarks: Did not involve repetitive failures or events.
N Involved questions or concerns pertaining to licensee operational performance Remarks: This was a human performance and configuration control event.
Operators failed to adequately recognize the ERV configuration that was in place due to a discrepancy in valve configuration tracking and implemented a planned work activity that established an inadvertent flow path. However, operators monitored water level and expected an initial lowering of level as part of the planned work activity. The operators recognized that the rate and amount of inventory decrease was greater than the expected range for the work activity and stopped the work, directing the flow path to be isolated.
The flow path and height location of the main steam lines (the lowest it could have drained if not isolated) is significantly higher than the reactor fuel and important shutdown cooling and inventory makeup system lines.
Therefore, given the operators attention to the water level, bias toward stopping the inventory reduction, and the inherently low risk of the specific flow path created, the NRC staff does not have significant questions or concerns related licensee operational performance as a result of the event, and believes that this deterministic criterion was not met.
CONDITIONAL RISK ASSESSMENT RISK ANALYSIS BY: N/A DATE:
N/A - No deterministic criteria met.
Issue Date: 12/14/23 Encl1-3 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:
Because no deterministic criteria were met, this operational event will be inspected via baseline inspection. No reactive inspection.
BRANCH CHIEF REVIEW:
DIVISION DIRECTOR REVIEW:
ADAMS ACCESSION NUMBER: ML25097A075 EVENT NOTIFICATION REPORT NUMBER (as applicable): N/A JASON SCHUSSLER Digitally signed by JASON SCHUSSLER Date: 2025.04.07 12:34:15 -04'00' BLAKE WELLING Digitally signed by BLAKE WELLING Date: 2025.04.07 15:02:14 -04'00'
Issue Date: 12/14/23 Att1-1 0309 : Decision Documentation for Reactive Inspection and Examples (Deterministic-only Criteria Analyzed)
Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)
PLANT: Nine Mile Point Unit 1 EVENT DATE: 03/30/2025 EVALUATION DATE: 03/31/2025 Brief Description of the Significant Event or Degraded Condition:
See enclosure 1.
REACTOR SAFETY Y/N IIT Deterministic Criteria N
Led to a Site Area Emergency Remarks: No emergency declaration was made.
N Exceeded a safety limit of the licensee's technical specifications Remarks: No safety limit was exceeded.
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: No, this operational event was not complex.
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: The licensee did not meet the criteria to declare an event.
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: No significant deficiencies in operational performance resulting in degrading, challenging, or disabling a safety system function or placing the plant in an unanalyzed condition.
Issue Date: 12/14/23 Att1-2 0309 RADIATION SAFETY Y/N IIT Deterministic Criteria N
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: No radiological release was involved.
N 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: No occupational or public exposure was involved.
N 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: No deliberate misuse or exposure was involved.
N Involved byproduct, source, or special nuclear material, which may have resulted in a fatality Remarks: No involvement of nuclear material which may have resulted in a fatality.
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: This event did not involve complex circumstances warranting Commission interest.
Y/N AIT Deterministic Criteria N
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: No radiological release of nuclear material exceeding regulatory limits.
Issue Date: 12/14/23 Att1-3 0309 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 Remarks: No deliberate misuse of materials was involved.
N 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: Did not involve radioactive material packaging.
N Involved the failure of the dam for mill tailings with substantial release of tailings material and solution off site Remarks: Did not involve mill tailings.
Y/N SI Deterministic Criteria N
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: No exposure in excess of the applicable regulatory limits was involved.
N 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: Little unplanned occupational exposure was involved, significantly lower than 40% of regulatory limits. The small amounts of occupational exposure that occurred were associated with field operator component manipulations to isolate the flow path (re-closing the block valves, etc.).
N 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: No unplanned change in restricted area dose rate was involved.
N 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: No unplanned change in airborne radioactivity was involved.
Issue Date: 12/14/23 Att1-4 0309 N
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: No uncontrolled, unplanned, or abnormal releases of radioactive material to the unrestricted area were involved.
N 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: No release of radioactive water to ground-water or offsite contamination was involved.
N 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: Did not involve radioactive material packaging.
N 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: The event was not reportable under 10 CFR 50.72.
Issue Date: 12/14/23 Att1-5 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: Not a safeguards/Security related event.
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: Not a safeguards/Security related event.
N/A Actual intrusion into the protected area Remarks: Not a safeguards/Security related event.
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: Not a safeguards/Security related event.
N/A Involved repeated instances of inadequate nuclear material control and accounting provisions to protect against theft or diversions of nuclear material Remarks: Not a safeguards/Security related event.
N/A Confirmed tampering event involving significant safety or security equipment Remarks: Not a safeguards/Security related event.
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: Not a safeguards/Security related event.
Issue Date: 12/14/23 Att1-6 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: Not a safeguards/Security related event.
N/A Involved a significant safeguards infraction that demonstrates the ineffectiveness of facility security provisions Remarks: Not a safeguards/Security related event.
N/A Confirmation of lost or stolen weapon Remarks: Not a safeguards/Security related event.
N/A Unauthorized, actual non-accidental discharge of a weapon within the protected area Remarks: Not a safeguards/Security related event.
N/A Substantial failure of the intrusion detection system (not weather related)
Remarks: Not a safeguards/Security related event.
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: Not a safeguards/Security related event.
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: Not a safeguards/Security related event.
Issue Date: 12/14/23 Att1-7 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:
Based upon no deterministic criteria being met, the branch recommends resident follow-up and continued baseline inspection.
BRANCH CHIEF REVIEW:
DIVISION DIRECTOR REVIEW:
ADAMS ACCESSION NUMBER: ML25097A075 EVENT NOTIFICATION REPORT NUMBER (as applicable): N/A JASON SCHUSSLER Digitally signed by JASON SCHUSSLER Date: 2025.04.07 12:44:32 -04'00' BLAKE WELLING Digitally signed by BLAKE WELLING Date: 2025.04.07 15:02:48 -04'00'