ML25008A104
| ML25008A104 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 12/13/2024 |
| From: | NRC/RGN-III/DORS/RPB3 |
| To: | |
| References | |
| MD 8.3 | |
| Download: ML25008A104 (1) | |
Text
MD 8.3 Evaluation Decision Documentation for Reactive Inspection (Deterministic and Risk Criteria Analyzed)
PLANT:
MONTICELLO NUCLEAR GENERATING PLANT EVENT DATE:
06/27/2024 DETERMINISTIC CRITERIA EVALUATION DATE:
12/13/2024 Brief Description of the Significant Operational Event or Degraded Condition:
On 6/27/2024, while performing RHR Water Fill Verification, the division 1 outboard LPCI injection valve (MO-2012) failed in mid-stroke and the valve was discovered to be inoperable. The motor turned in the open and closed directions, but the clutch mechanism would not engage to stroke the valve. Manual valve operation was likewise impeded. The failure of MO-2012 in mid-stroke prevented both LPCI divisions from fulfilling their safety functions. On 6/28/2024, the licensee declared both LPCI divisions inoperable and entered a 72-hour shutdown LCO. The licensee documented the issue in their corrective action program and commenced troubleshooting and repair activities. Troubleshooting revealed that a broken spring in the MOV declutching mechanism had lodged in a position that precluded valve movement. The valve was repaired, tested, and returned to service. The licensee exited the 72-hour shutdown LCO on 6/29/2024.
On 7/1/2024, the Region III DORS branch chiefs discussed the issue stated above and determined that no MD 8.3 was needed. The branch chiefs did not see this equipment failure as a significant operational event, but as a degraded condition. Based on the information that was available the degraded condition appeared to be an isolated case.
On 8/7/2024, further licensee investigation found motor shaft damage and an undersized motor pinion set screw was found to be installed. The correct motor pinion set screw was subsequently installed, reducing the potential for a repeat failure for MO-2012.
The licensees Organizational Effectiveness Worksheet in the RCR was completed on 10/11/2024. Included in the RCR was information that the other train outboard LPCI injection valve (MO-2013) also had similar issues that were identified in 2017, and the incorrect set screw was found installed, and repaired in 2019. However, the licensee did not look at the other train.
Furthermore, it was determined that both valves had the incorrect set screws installed since 1993.
NRC INFORMATION NOTICE 2003-15: Importance of Followup Activities in Resolving Maintenance Issues, addressed concerns that Monticello was experiencing with these two valves and possibly others.
Based on this new information the issues were deemed MD 8.3 worthy.
Y/N DETERMINISTIC CRITERIA
- 1. Involved operations that exceeded, or were not included in, the design bases of the facility N
Remarks: The situation did not exceed the design basis of the facility
2
- 2. Involved a major deficiency in design, construction, or operation having potential generic safety implications N
Remarks: Did not involve a major deficiency in design, construction, or operation having potential generic safety implications.
- 3. Led to a significant loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of a nuclear reactor N
Remarks: No loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of a nuclear reactor occurred.
- 4. Led to the loss of a safety function or multiple failures in systems used to mitigate an actual event N
Remarks: No loss of a safety function or multiple failures in systems used to mitigate an actual event occurred.
- 5. Involved possible adverse generic implications N
Remarks: Did not involve possible adverse generic implications. Involved possible adverse generic implications.
- 6. Involved significant unexpected system interactions N
Remarks: Did not involve significant unexpected system interactions.
- 7. Involved repetitive failures or events involving safety-related equipment or deficiencies in operations Y
Remarks: Based on the information provided in the licensees RCR, it was determined that repetitive failures with the same cause happened for both MO-2012 and MO-2013.
- 8. Involved questions or concerns pertaining to licensee operational performance N
Remarks: Did not involve questions or concerns pertaining to licensee operational performance.
3 CONDITIONAL RISK ASSESSMENT RISK ANALYSIS BY: Josh Havertape DATE: 12/11/2024 Brief Description of the Basis for the Assessment (may include assumptions, calculations, references, peer review, or comparison with licensee=s results):
A regional senior reactor analyst (SRA), using SAPHIRE version 8.2.11, and the Monticello SPAR model version TLU1, completed a condition assessment for the degraded condition associated with the low-pressure core injection (LPCI) loop A injection valve, MOV-2012. The SRA determined that modification to the SPAR model was needed to represent the interaction of the degraded condition and the LPCI loop select logic, which may isolate either LPCI loop A or B, depending on the scenario. The SRA worked with Idaho National Lab to make these changes and represented the degraded condition with the basic event for failure of MOV-2012 to open on demand, LCI-MOV-CC-2012, set to TRUE. The basis for this assumption was that for events involving high drywell pressure or low reactor vessel level, MOV-2012 is expected to shut due to the LPCI LOOP select function aligning to reactor recirculation loop B unless there is a loss of coolant event on the B loop. Due to the nature of the degraded condition, MOV-2012 was assumed to be capable of closing on demand, but unable to subsequently re-open making the loop A injection path unavailable. The SRA determined that there was uncertainty associated with the exposure period because the component may be subjected to additional stresses during accident conditions (i.e., full flow) relative to surveillance test conditions (i.e., no flow) that may have caused the degraded condition to reveal itself earlier had it been demanded during a plant event. To address this uncertainty the SRA evaluated an exposure period of 8 days and 1 year to determine a CDP range. This assumption was based on:
Seven days had elapsed since the last successful operation of the valve during surveillance conditions, plus one day of repair time, per Section 2.3 of Risk Assessment of Operational Events Handbook (RASP), Volume 1 - ML17348A149.
Approximately 3 years had elapsed since the valve first showed signs of degradation as indicated by NRC Information Notice 2003-15, Importance of follow-up activities in resolving maintenance issues - ML032480905, (i.e.. the manual valve operator was difficult to operate and did not position the valve as expected during declutching operations in April 2021) and the time of failure could not be determined. Assuming an exposure time of T = t/2 + repair time per Section 2.4 of RASP, Volume 1, this would give 18 months.
However, RASP, Section 2.7, limits exposure period to one year.
The estimated CDP range was determined to be 4.1E-9 to 1.9E-7 and places the risk in the range of no additional inspection outside of ROP baseline inspection follow-up. This assessment did not include contributions from external hazards. The most significant risk contributors to the evaluation were scenarios that resulted in a loss of high-pressure injection, followed by successful depressurization and a failure of low-pressure injection leading to core damage.
4 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 on the review and associated the risk in the range of no additional inspection outside of ROP baseline inspection follow-up, the decision is to have the resident to follow-up on the issue.
BRANCH CHIEF: Richard Skokowski DATE: 01/08/2025 SRA: Josh Havertape DATE: 01/08/2025 DIVISION DIRECTOR: Jason Kozal DATE: 01/10/2025 DIVISION DIRECTOR:
DATE:
RA (if reactive inspection is initiated)
DATE:
ADAMS ACCESSION NUMBER: ML25008A104 ADAMS PACKAGE ACCESSION NUMBER: ML25013A166 EVENT NOTIFICATION REPORT NUMBER (as applicable):
Internal Distribution List is at the end of this document.
Szwarc, Dariusz signing on behalf of Skokowski, Richard on 01/08/25 Signed by Havertape, Joshua on 01/08/25 Dickson, Billy signing on behalf of Kozal, Jason on 01/10/25
5 Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)
PLANT:
MONTICELLO NUCLEAR GENERATING PLANT EVENT DATE:
06/27/2024 EVALUATION DATE:
Brief Description of the Significant Event or Degraded Condition:
REACTOR SAFETY Y/N IIT Deterministic Criteria 1.
Led to a Site Area Emergency Remarks: No emergency declaration was made.
2.
Exceeded a safety limit of the licensees technical specifications Remarks: No safety limits were exceeded.
3.
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 sufficiently complex issue.
Y/N SI Deterministic Criteria 4.
Significant failure to implement the emergency preparedness program during an actual event, including the failure to classify, notify, or augment onsite personnel Remarks: Licensee did not meet the criteria to declare an event.
5.
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 concerns with the performance of operators
6 RADIATION SAFETY Y/N IIT Deterministic Criteria 1.
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.
2.
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.
3.
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 and no exposure.
4.
Involved byproduct, source, or special nuclear material, which may have resulted in a fatality Remarks: Did not involve nuclear material which may have resulted in a fatality.
5.
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 sufficiently complex circumstances warranting Commission interest.
Y/N AIT Deterministic Criteria 6.
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.
7 7.
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.
8.
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: No failure of radioactive material packaging was involved.
9.
Involved the failure of the dam for mill tailings with substantial release of tailings material and solution off site Remarks: No failure of a dam for mill tailings was involved.
Y/N SI Deterministic Criteria
- 10. 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.
- 11. 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: No unplanned occupation exposure was involved.
- 12. 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 changes in restricted area dose rates were involved.
- 13. 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 changes in airborne radioactivity levels were involved.
8
- 14. 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.
- 15. 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 large, unplanned release of radioactive liquid inside the restricted area was involved.
- 16. 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: No failure of radioactive materials packaging was involved.
- 17. 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: There was no 10 CFR 50.72 report submitted nor expected for this event.
SAFEGUARDS/SECURITY Y/N IIT Deterministic Criteria 1.
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: The circumstances surrounding the event did not involve safeguards.
9 2.
Failure of licensee significant safety equipment or adverse impact on licensee operations as a result of a safeguards initiated event (e.g., tampering).
Remarks: No safeguards initiated event was involved.
3.
Actual intrusion into the protected area Remarks: No intrusion into the protected area.
Y/N AIT Deterministic Criteria 4.
Involved a significant infraction or repeated instances of safeguards infractions that demonstrate the ineffectiveness of facility security provisions Remarks: No infractions demonstrating ineffectiveness of facility security provisions were involved 5.
Involved repeated instances of inadequate nuclear material control and accounting provisions to protect against theft or diversions of nuclear material Remarks: No instances of inadequate nuclear material control and accounting provisions were involved.
6.
Confirmed tampering event involving significant safety or security equipment Remarks: No tampering was involved.
7.
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: No failures in the licensees intrusion detection or package/personnel search procedures were involved.
10 Y/N SI Deterministic Criteria 8.
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: No inadequate nuclear material control and accounting provisions were involved.
9.
Involved a significant safeguards infraction that demonstrates the ineffectiveness of facility security provisions Remarks: No safeguards infractions were involved.
- 11. Unauthorized, actual non-accidental discharge of a weapon within the protected area Remarks: No discharge of a weapon occurred.
- 12. Substantial failure of the intrusion detection system (not weather related)
Remarks: There were not failures of the intrusion detection system.
- 13. Failure to the licensees package/personnel search procedures which results in contraband or an unauthorized individual being introduced into the protected area Remarks: No failures of package/personnel search procedures were involved.
- 14. 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: No tampering or vandalism was involved.
11 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:
BRANCH CHIEF: Richard Skokowski DATE: 01/08/2025 SRA: Josh Havertape DATE: 01/08/2025 DIVISION DIRECTOR: Jason Kozal DATE: 01/10/2025 DIVISION DIRECTOR:
DATE:
ADAMS ACCESSION NUMBER: ML25008A104 ADAMS PACKAGE ACCESSION NUMBER: ML25013A166 EVENT NOTIFICATION REPORT NUMBER (as applicable):
Distribution: Alejandro.Alen@nrc.gov; Scott.Morris@nrc.gov; Jason.Carneal@nrc.gov; John.Giessner@nrc.gov; Mohammed.Shuaibi@nrc.gov; Blake.Welling@nrc.gov; Ray.McKinley@nrc.gov; Mark.Franke@nrc.gov; Gregory.Suber@nrc.gov; Laura.Pearson@nrc.gov; LaDonna.Suggs@nrc.gov; Ravi.Penmetsa@nrc.gov; Jason.Kozal@nrc.gov; Billy.Dickson@nrc.gov; David.Curtis@nrc.gov; Jared.Heck@nrc.gov; Geoffrey.Miller@nrc.gov; Nick.Taylor@nrc.gov; Michelle.Garza@nrc.gov; Doris.Chyu@nrc.gov; Joshua.Havertape@nrc.gov; Lionel.Rodriguez@nrc.gov; Steven.Alferink@nrc.gov; NRR_Reactive_Inspection.Resource@nrc.gov; Dariusz.Szwarc@nrc.gov Szwarc, Dariusz signing on behalf of Skokowski, Richard on 01/08/25 Signed by Havertape, Joshua on 01/08/25 Dickson, Billy signing on behalf of Kozal, Jason on 01/10/25