NUREG-1829, Example Xlpr LOCA Frequency Estimates Compared to NUREG-1829 Expert Elicitation Results
| ML22166A352 | |
| Person / Time | |
|---|---|
| Issue date: | 06/14/2022 |
| From: | Matthew Homiack Office of Nuclear Regulatory Research |
| To: | |
| References | |
| Download: ML22166A352 (11) | |
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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