View source for NUREG-1829, Example Xlpr LOCA Frequency Estimates Compared to NUREG-1829 Expert Elicitation Results

{{Adams
| number = ML22166A352
| issue date = 06/14/2022
| title = Example Xlpr LOCA Frequency Estimates Compared to NUREG-1829 Expert Elicitation Results
| author name = Homiack M
| author affiliation = NRC/RES
| addressee name = 
| addressee affiliation = 
| docket = 
| license number = 
| contact person = 
| document type = Meeting Briefing Package/Handouts, Slides and Viewgraphs
| page count = 11
}}

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{{#Wiki_filter:June         14, 2022 Example xLPR LOCA Frequency Estimates Compared to NUREG-1829 Exper t Elicitation Results Matthew Homiack Materials Engineer U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research Division of Engineering Reactor Engineering Branch Matthew.Homiack@nrc.gov
   +1 (301) 415-2427

Objective and Approach
 > Explore use of the Extremely Low Probability of Rupture (xLPR) probabilistic fracture mechanics code to generate loss-of-coolant accident (LOCA) frequency estimates and compare those estimates with the expert elicitation results from NUREG-1829
 > Review data and assumptions from NUREG-1829
 > Develop best-estimate xLPR inputs using latest data as applicable
 > Generate component-level LOCA frequency estimates from xLPR simulation and compare to NUREG-1829 base case results
 > Aggregate xLPR component-level estimates to arrive at system-level estimate and compare to NUREG-1829 expert elicitation results for piping system 2

Inputs and Modeling Assumptions W e s t i n g h o u s e R e a c t o r P r e s s u r e Ve s s e l ( R P V ) O u t l e t Nozzle Dissimilar Metal Weld (DMW) Analysis
   > Data re-used from                              > New data as compared to Dave Harris        > Notable modeling NUREG-1829                                     analysis                                      assumptions
           - Component geometry                        -   Material properties (similar)              - No fatigue, only primary
           - Capacity factor (80%)                     -   Loads                                          water stress-corrosion
           - LOCA definitions:                         -   Initial crack size (slightly deeper)           cracking
                                                       -   Leak rate detection (1 vs. 5 gpm)          - Use crack initiation model LOCA           Leak     Crack Opening Area Category       Rate (LR)         (COA)          -   Plant operation (80 vs. 60 years)          - No mechanical mitigation
: 1. Small-break (SB)   100 gpm         0.196 in2        -   Welding residual stresses (included        - Circumferential cracks only
: 2. Medium-break (MB) 1,500 gpm         1.77 in2            with uncertainties)
: 3. Large-break (LB)  5,000 gpm         7.07 in2        - Different inservice inspection schedule (more inspections) and probability of detection (details on Slide 11)                                          3

xLPR Westinghouse RPV Outlet Nozzle DMW LOCA Estimates Leakage Detection Inservice Inspection SMALL variation among SB, MB, and LB LOCA estimates MORE variation from LOCA definition (i.e., LR vs. COA) 4

xLPR Results vs. NUREG-1829 PWR-1 Base Case (1 of 3)
Leakage Detection Inservice Inspection
> xLPR estimates are h i g h e r, a s e x p e c t e d
> Much more variation among NUREG-1829 estimates 5

xLPR Results vs. NUREG-1829 PWR-1 Base Case (2 of 3)
Leakage Detection Inservice Inspection At 25 years, the xLPR results are within the range of the NUREG-1829 estimates At 60 years, the xLPR results show a higher increase relative to the NUREG-1829 estimates 6

xLPR Results vs. NUREG-1829 PWR-1 Base Case (3 of 3)
Leakage Detection Inservice Inspection NO LOCA EVENTS in xLPR simulation with a sample size of 100,000 realizations UPPER-BOUND estimated using rule of 3 approach consistent with NUREG/CR-7278, Section 4.3.6.4 7

Weld Residual Stress (WRS)
Sensitivity Study Results Leakage Detection          Inservice Inspection WRS Profile Comparison
> Linear WRS profile is unrealistic xLPR Results with Linear WRS Profile       8

xLPR Results vs. NUREG-1829 PWR Hot Leg Exper t Elicitation Westinghouse RPV Outlet Nozzle DMW  x  4 MBLOCA Results LBLOCA Results SBLOCA Results Leakage Detection       Inservice Inspection 9

Key Obser vations
> The xLPR code can be used to develop system- or plant-level LOCA frequency estimates using current capabilities
> The LOCA frequency estimates results are sensitive to the modeling inputs and assumptions, and these sensitivities can be studied
> Leak rate detection has a significant impact 1
10 0

Suppor ting Infor mation - Probability of Detection Cur ve Comparisons 11}}