20.08.2015   Estimating Loss-of-Coolant Accident (LOCA) Frequencies Through the Elicitation Process

Summary of Input Data and Results

Tables D.22 and D.23 summarize the input data to the LOCA frequency calculation. Tables D.24 through D.26 give the results at T = 25, 40 and 60 years, respectively. Consistent with the LOCA frequency elicitation structure, Table D.27 is summary of mid values (MV, or 50th percentiles) at T = 25 years rather than mean values, however. Figure D.41 shows the time-dependent LOCA frequencies. Figure D.42 shows selected weld failure rates. Figures D.43 through D.46 show the contribution to LOCA frequency by respective Base Case. Note that Figure D.45 includes the contribution to LOCA frequency by PWR-1 (Reactor Coolant System Hot Legs; all 3 loops are accounted for in this figure) and PWR-2 (Pressurizer Surge Line). Note that the Base Case results used in Table 4.1 in the main body can be obtained from Tables D.16, D.17, and D.20 in this report.

Table D.22 Summary of Key BWR Base Case Input Data

Base Case

Input

BWR-1

BWR-2

Data

NPS12

NPS22

NPS28

NPS12

NPS14

NPS20

Weld count

50

16

56

63

5

53

Weld failure rate Dominant [1/Reactor-yr.]

6.50E-05

1.54E-04

1.44E-04

2.20E-06

2.20E-06

1.58E-06

Weld failure rate Minimum [1/Reactor-yr.]

2.37E-05

3.32E-05

1.29E-05

1.77E-07

1.77E-07

1.73E-07

Table D.23 Summary of Key PWR Base Case Input Data

Input Data

Base Case

PWR-1

PWR-2

PWR-3

NPS30

NPS14

NPS3-%

Weld count

50

14

9

Weld failure rate Dominant [1/Reactor-yr.]

7.64E-05

1.56E-06

6.56E-04

Weld failure rate Minimum [1/Reactor-yr.]

1.05E-06

4.60E-08

1.58E-06

Table D.24 Calculated LOCA Frequencies (T = 25 Years)

LOCA Frequency — Statistical Mean [per Reactor-year]

Base

Flow Rate Threshold Value [gpm

Case

Catl

Cat2

Cat3

Cat4

Cat5

Cat6

V > 100

V > 1,500

V > 5,000

V > 25,000

V > 100,000

V > 500,000

BWR-113

9.46E-06

1.22E-06

4.60E-07

1.53E-07

3.05E-08

N/A14

BWR-215

2.54E-06

3.36E-07

1.25E-07

4.09E-08

7.33E-09

N/A

PWR-116

7.42E-07

7.62E-08

2.93E-08

1.09E-08

3.77E-09

1.26E-09

PWR-2

1.29E-07

1.50E-08

5.40E-09

1.56E-09

5.31E-10

N/A

PWR-317

1.60E-05

2.32E-06

9.22E-07

N/A

N/A

N/A

Table D.25 Calculated LOCA Frequencies (T = 40 Years)

Base

Case

LOCA Frequency — Statistical Mean [per Reactor-year]

Flow Rate Threshold Value [gpm

Catl V > 100

Cat2 V > 1,500

Cat3 V > 5,000

Cat4

V > 25,000

Cat5

V > 100,000

Cat6

V > 500,000

BWR-1

1.14E-05

1.47E-06

5.54E-07

1.84E-07

3.78E-08

N/A

BWR-2

2.56E-06

3.39E-07

1.26E-07

4.13E-08

7.40E-09

N/A

PWR-1

8.96E-07

9.20E-08

3.54E-08

1.32E-08

4.55E-09

1.45E-09

PWR-2

1.60E-07

1.86E-08

6.70E-09

1.93E-09

6.59E-10

N/A

PWR-3

1.95E-05

3.30E-06

9.44E-07

N/A

N/A

N/A

Table D.26 Calculated LOCA Frequencies (T = 60 Years)

Base

Case

LOCA Frequency — Statistical Mean [per Reactor-year]

Flow Rate Threshold Value [gpm

Cat1 V > 100

Cat2 V > 1,500

Cat3 V > 5,000

Cat4

V > 25,000

Cat5

V > 100,000

Cat6

V > 500,000

BWR-1

1.88E-05

2.43E-06

9.16E-07

3.05E-07

6.07E-08

N/A

BWR-2

2.56E-06

3.39E-07

1.26E-07

4.13E-08

7.40E-09

N/A

PWR-1

9.74E-07

1.00E-07

3.85E-08

1.43E-08

4.95E-09

1.57E-09

PWR-2

1.77E-07

2.06E-08

7.41E-09

2.14E-09

7.29E-10

N/A

PWR-3

1.96E-05

3.32E-06

9.50E-07

N/A

N/A

N/A

13 BWR-1 is the combination of RR Loop A and B.

14 N/A = not applicable.

15 The results are for FW Loop A and B.

16 The results are for 3-of-3 RC hot legs.

17 The results are for 2-of-2 HPI/NMU lines.

Base

Case

Median (MV) LOCA Frequency [per Reactor-year]

Flow Rate Threshold Value [gpm

Cat1 V > 100

Cat2 V > 1,500

Cat3 V > 5,000

Cat4

V > 25,000

Cat5

V > 100,000

Cat6

V > 500,000

BWR-1

8.23E-06

1.08E-06

4.03E-07

1.29E-07

2.19E-08

N/A

BWR-2

1.09E-06

1.35E-07

5.03E-08

1.65E-08

2.10E-09

N/A

PWR-1

1.54E-07

2.25E-08

8.33E-09

2.85E-09

8.53E-10

1.58E-10

PWR-2

1.37E-08

1.39E-09

5.15E-10

1.54E-10

5.46E-11

N/A

PWR-3

6.87E-06

1.15E-06

2.14E-07

N/A

N/A

N/A

image077

0 10 20 30 40 50 60 70

Years

Figure D.41 Time-Dependent Cat 1 LOCA Frequencies

Подпись: Weld Failure Rate [1/Reactor-yr.]

RR NPS28 Pipe-to — RR NPS28 Elbow-to — RR NPS12 Pipe-to — RC-HL NPS30 Nozzle — RC-HL NPS30 Elbow — RC Surge Line HPI/NMU (NPS 3-3/4) Safe-end Pipe Reducer to-Safe-end to-Pump (NPS14) Nozzle-to — Pipe-to-Nozzle Safe-

Safe-end end

 

1.0E-04

 

1.0E-05

 

1.0E-06

 

image079

image080

Figures D.48 (BWR) and D.49 (PWR) show the influence of in-service inspection on the time-dependent LOCA frequency; no ISI and ISI with POD = 0.5 and 0.9, respectively.

Подпись: Cat1 LOCA Frequency [1/Reactor.Yr] image082

Figure D.48 Influence of ISI on Time-Dependent BWR-1 Cat 1 LOCA Frequency

Figure D.49 Influence of ISI on Time-Dependent PWR-1 Cat 1 LOCA Frequency