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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E x a m p l e x L P R L O C A F r e q u e n c y E s t i m a t e s C o m p a r e d t o N U R E G - 1 8 2 9 E x p e r t E l i c i t a t i o n R e s u l t s J u n e 1 4, 2 0 2 2 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
> 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
O b j e c t i v e a n d A p p r o a c h
> 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 2
I n p u t s a n d M o d e l i n g A s s u m p t i o n s We 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 N o z z l e D i s s i m i l a r M e t a l We l d ( D M W ) A n a l y s i s
> Data re-used from NUREG-1829
> New data as compared to Dave Harris analysis Component geometry Capacity factor (80%)
LOCA definitions:
> Notable modeling assumptions No fatigue, only primary water stress-corrosion cracking Use crack initiation model No mechanical mitigation Circumferential cracks only 3
LOCA Category Leak Rate (LR)
Crack Opening Area (COA)
- 1. Small-break (SB) 100 gpm 0.196 in2
- 2. Medium-break (MB) 1,500 gpm 1.77 in2
- 3. Large-break (LB) 5,000 gpm 7.07 in2 Material properties (similar)
Loads Initial crack size (slightly deeper)
Leak rate detection (1 vs. 5 gpm)
Plant operation (80 vs. 60 years)
Welding residual stresses (included with uncertainties)
Different inservice inspection schedule (more inspections) and probability of detection (details on Slide 11)
x L P R W e s t i n g h o u s e R P V O u t l e t N o z z l e D M W L O C A E s t i m a t e s 4
SMALL variation among SB, MB, and LB LOCA estimates Leakage Detection Inservice Inspection MORE variation from LOCA definition (i.e., LR vs. COA)
x L P R R e s u l t s v s. N U R E G - 1 8 2 9 P W R - 1 B a s e C a s e ( 1 o f 3 )
5 Leakage Detection Inservice Inspection
> x L P R e s t i m a t e s a r e h i g h e r, a s e x p e c t e d
> M u c h m o r e v a r i a t i o n a m o n g N U R E G - 1 8 2 9 e s t i m a t e s
x L P R R e s u l t s v s. N U R E G - 1 8 2 9 P W R - 1 B a s e C a s e ( 2 o f 3 )
6 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
x L P R R e s u l t s v s. N U R E G - 1 8 2 9 P W R - 1 B a s e C a s e ( 3 o f 3 )
7 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
W e l d R e s i d u a l S t r e s s ( W R S )
S e n s i t i v i t y S t u d y R e s u l t s 8
Leakage Detection Inservice Inspection xLPR Results with Linear WRS Profile WRS Profile Comparison
> L i n e a r W R S p r o f i l e i s u n r e a l i s t i c
x L P R R e s u l t s v s. N U R E G - 1 8 2 9 P W R H o t L e g E x p e r t E l i c i t a t i o n 9
Leakage Detection Inservice Inspection SBLOCA Results MBLOCA Results LBLOCA Results x4 Westinghouse RPV Outlet Nozzle DMW
1 0
K e y O b s e r v a t i o n s 10
> T h e L O C A f r e q u e n c y e s t i m a t e s r e s u l t s a r e s e n s i t i v e t o t h e m o d e l i n g i n p u t s a n d a s s u m p t i o n s, a n d t h e s e s e n s i t i v i t i e s c a n b e s t u d i e d
> T h e x L P R c o d e c a n b e u s e d t o d e v e l o p s y s t e m - o r p l a n t - l e v e l L O C A f r e q u e n c y e s t i m a t e s u s i n g c u r r e n t c a p a b i l i t i e s
> L e a k r a t e d e t e c t i o n h a s a s i g n i f i c a n t i m p a c t
S u p p o r t i n g I n f o r m a t i o n - P r o b a b i l i t y o f D e t e c t i o n C u r v e C o m p a r i s o n s 11