ML25107A193
| ML25107A193 | |
| Person / Time | |
|---|---|
| Issue date: | 04/28/2025 |
| From: | Beverly Smith Office of Nuclear Regulatory Research |
| To: | John Tappert Office of Nuclear Regulatory Research |
| Shared Package | |
| ML25107A190 | List: |
| References | |
| Download: ML25107A193 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MEMORADUM TO:
John R. Tappert, Acting Director Office of Nuclear Regulatory Research FROM:
Brian Smith, Director Division of Risk Analysis Office of Nuclear Regulatory Research
SUBJECT:
TRANSMITTAL OF THE ACCIDENT SEQUENCE PRECURSOR PROGRAM 2024 ANNUAL REPORT This memorandum transmits the Accident Sequence Precursor (ASP) Program 2024 Annual Report. The ASP Program assesses licensee event reports (LERs) at U.S. nuclear power plants to identify potential precursors to core damage.
There were 165 LERs issued in calendar year 2024. From these LERs, 141 (approximately 85 percent) were screened out in the initial screening process and 24 events were selected and analyzed as potential precursors. The overall number of LERs and potential precursors remains near historical low levels.
Of the 24 potential precursors, 9 events were determined to exceed the ASP Program threshold and, therefore, are precursors. An additional precursor was identified for a degraded condition where no LER was issued. Greater-than-Green inspection findings accounted for 8 of the precursors identified in 2024, while 2 precursors were identified via independent ASP analyses.
No significant precursors (i.e., conditional core damage probability (CCDP) or increase in core damage probability (CDP) greater than or equal to 10-3) were identified in 2024. In addition, no important precursors (i.e., CCDP or CDP greater than or equal to 10-4) were identified.
A review of the trends over the past decade (2015-2024) reveals that there are no statistically significant trends for all precursors or most precursors subgroups (e.g., initiating events, degraded conditions, precursors at pressurized-water reactors, losses of offsite power, emergency diesel generator failures, etc.). A statistically significant decreasing trend was identified for precursors at boiling-water reactors during this same period. Although there is no statistically significant increasing trend for precursors associated with EDG failures, there has been an increase in these precursors in recent years. Specifically, the 16 EDG precursors identified in the past 3 years are tied for the most in a 3-year period in ASP Program history.
CONTACT:
Christopher Hunter, RES/DRA/PRB 301-415-1394 April 28, 2025 Signed by Smith, Brian on 04/28/25
J. Tappert The number of precursors identified remain at historically low valuesthe 74 precursors identified in the past decade is the lowest 10-year period total since the ASP Programs inception. The results of the ASP trends, including the ASP index, indicate that licensee risk management initiatives have been effective in maintaining a flat or decreasing risk profile for the industry and that current agency oversight programs and licensing activities remain effective. In addition, there are no indications of increasing risk due to the potential cumulative impact of risk-informed initiatives and no new component failure modes or mechanisms were identified.
Enclosure:
As stated
ML25107A193 (Memo); ML25107A192 (Enclosure)
OFFICE RES/DRA/PRB RES/DRA/PRB RES/DRA NAME C. Hunter J. Lane B. Smith DATE
BS JL CH DATE Annual ASP Report and Memo 2024 April 28, 2025 DISTRIBUTION:
CHunter, RES/DRA/PRB JLane, RES/DRA/PRB BSmith, RES/DRA JTappert, RES/DRA AKock, NRR DCollins, R-I/DRP MShuaibi, R-III RN.Felts, NRR/DRO PMcKenna, NRR/DRO DAird, NRR/DRO/IRAB RRodriguez, R-II/DORS/RPB6 SWeerakkody, NRR/DRA FArner, R-I/DRS ARosebrook, R-II/DORS/RPB6 RDeese, R-IV/DORS TStephen, R-II/DORS/OB1 MKing, NRR MFranovich, NRR/DRA JGroom, R-IV/ACES MMiller, R-II/ORA JLara, R-IV JMonninger, R-IV MKhanna, NRR/DRA SVasavada, NRR/DRA BBenney, NRR/DRO/IOEB AGarmoe, NRR/DRO/IRAB KCoyne, RES/DRA CBickett, R-I/DRS/EB2 SSandal, R-II/DORS/RPB6 LRodriguez, R-III/DRS/OB CYoung, R-IV/DRP/RPB-C ADAMS Accession No.: Memo ML25107A193 OFFICE RES/DRA/PRB RES/DRA/PRB RES/DRA NAME CHunter JLane BSmith DATE Apr 17, 2025 Apr 28, 2025 Apr 28, 2025 4
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