ML19119A275
| ML19119A275 | |
| Person / Time | |
|---|---|
| Issue date: | 04/23/2019 |
| From: | Michael Cheok NRC/RES/DRA |
| To: | Raymond Furstenau Office of Nuclear Regulatory Research |
| C. Hunter 301-415-1394 | |
| Shared Package | |
| ML19119A274 | List: |
| References | |
| Download: ML19119A275 (2) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 23, 2019 MEMORADUM TO: Raymond V. Furstenau Director of Nuclear Regulatory Research FROM: Michael C. Cheok, Director /RA/
Division of Risk Analysis Office of Nuclear Regulatory Research
SUBJECT:
TRANSMITTAL OF THE ACCIDENT SEQUENCE PRECURSOR PROGRAM 2018 ANNUAL REPORT This memorandum transmits the Accident Sequence Precursor (ASP) Program 2018 Annual Report. The ASP Program assesses licensee event reports at U.S nuclear power plants to identify potential precursors to core damage.
Six events were determined to exceed the ASP Program threshold and, therefore, are precursors.
Two of these precursors had late-2017 event dates and, therefore, are included in the 2017 precursor counts for trending purposes. Of these 6 precursors, 3 events were identified by ASP analyses and 3 events used Significance Determination Process results. This annual count of precursors is near historic lows. No significant precursors were identified in 2018. In addition, no precursors with conditional core damage probability or increase in core damage probability greater than or equal to 10-5 were identified for the first time in ASP history.
A review of the trends over the past decade (2009-2018) reveals statistically significant decreasing trends for all precursors and most precursors subgroups (e.g., initiating events, degraded conditions, losses of offsite power, precursors at pressurized-water reactors, etc.).
However, no statistically significant trends were identified for precursors at boiling-water reactors and emergency diesel generator degraded conditions during this same period. Since 2009, the ASP Program has documented 138 precursors (90 involving degraded conditions and 48 resulting from initiating events). Emergency diesel generator failures are the most frequent cause of degraded condition precursors, while 35 percent of initiating event precursors are the result of natural phenomena (e.g., severe weather, seismic, etc.).
The decreasing 10-year precursor trends, along with the decreasing overall risk from precursors as shown in the integrated ASP index, demonstrate that current agency oversight programs and licensing activities remain effective. A review of precursor data and trends do not reveal any gaps in licensee performance areas not currently covered by the Reactor Oversight Process. The ASP Program results also continue to show that licensee risk management initiatives are effective in helping to maintain a flat or decreasing risk profile for the industry. In the area of licensing activities, the risk profiles and trends from the ASP Program do not indicate an increase in risk due to the potential cumulative impact of risk-informed initiatives.
Enclosure:
As stated CONTACT: Christopher Hunter, RES/DRA/PRB 301-415-1394
ML19119A274 OFFICE RES/DRA/PRB RES/DRA/PRB RES/DRA NAME C. Hunter F. Gonzalez M. Cheok DATE 4/19/2019 4/19/2019 4/23/2019