ML24107B131
| ML24107B131 | |
| Person / Time | |
|---|---|
| Issue date: | 04/25/2024 |
| From: | Christian Araguas, Christopher Hunter NRC/RES/DRA/PRB |
| To: | John Tappert Office of Nuclear Regulatory Research |
| Shared Package | |
| ML24107B128 | List: |
| References | |
| Download: ML24107B131 (1) | |
Text
J. Tappert UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MEMORADUM TO:
John R. Tappert, Acting Director Office of Nuclear Regulatory Research FROM:
Christian J. Araguas, Director Division of Risk Analysis Office of Nuclear Regulatory Research
SUBJECT:
TRANSMITTAL OF THE ACCIDENT SEQUENCE PRECURSOR PROGRAM 2023 ANNUAL REPORT This memorandum transmits the Accident Sequence Precursor (ASP) Program 2023 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 138 licensee LERs issued in calendar year 2023. From these LERs, 119 (approximately 86 percent) were screened out in the initial screening process and 19 events were selected and analyzed as potential precursors. The overall number of LERs and potential precursors remains at historical low levels.
Of the 19 potential precursors, one event was determined to exceed the ASP Program threshold and, therefore, is a precursor. An additional four precursors were identified for degraded conditions where no LER was issued. All five precursors identified in 2023 were the result of greater-than-Green inspection findings. 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 2023. 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 (2014-2023) reveals statistically significant decreasing trends for all precursors and some precursors subgroups (e.g., initiating events and precursors at boiling-water reactors). No statistically significant trends were identified for the other precursor subgroups (e.g., degraded conditions, precursors at pressurized-water reactors, losses of offsite power, emergency diesel generator degraded conditions, etc.) during this same period.
These ASP trends, along with the results of the ASP index, indicate that NRC oversight and licensing activities remain effective and that licensee risk management initiatives are not resulting in an increasing risk profile for the industry.
CONTACT:
Christopher Hunter, RES/DRA/PRB 301-415-1394 April 25, 2024 Signed by Araguas, Christian on 04/25/24
J. Tappert 2
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
ML24107B128; ML24107B131 OFFICE RES/DRA/PRB RES/DRA/PRB RES/DRA NAME CHunter JLane CAraguas DATE Apr 18, 2024 Apr 23, 2024 Apr 25, 2024