ML14149A089

NRR E-mail Capture - STP-GSI-191 Presentation

ML14149A089
Person / Time
Site:	South Texas
Issue date:	05/21/2014
From:	Harrison A South Texas
To:	Balwant Singal Division of Operating Reactor Licensing
References
STP-GSI-191, TAC MF2400, TAC MF2401
Download: ML14149A089 (46)

Text

1 NRR-PMDA-ECapture Resource From:

Harrison Albon <awharrison@STPEGS.COM>

Sent:

Wednesday, May 21, 2014 11:03 AM To:

Singal, Balwant Cc:

Kee, Ernie; Blossom, Steven; Murray, Michael

Subject:

STP Sensitivity Presentation Attachments:

STP-GSI-191 Presentation May 222014.pdf

Balwant,

Ourpresentationisattached.Also,AlionconfirmedtheSWRIpresentationhasnoproprietaryinformation.

Wayne

CASA Grande Sensitivity Studies May 22,2014

Introductions

• Presenters Mike Murray Wayne Harrison Ernie Kee David Morton Bruce Letellier 2

Introductions

• Contributors Steve Blossom Zahra Mohaghegh Seyed Reihani Jeremy Tejada Don Wakefield 3

Summary

• Summarize approach to sensitivity analyses

• Demonstrate the approach on several parameters

• Review and explain counterintuitive results observed with certain parameters 4

Development Status and Potential Application o Development Status o NOT being proposed for NRC review/approval as part of the Risk-Informed Pilot Application o Will require appropriate validation and verification o Potential Applications o Facilitate evaluation of emergent plant conditions Facilitate identification/prioritization of compensatory actions Quantitative assessment may be required to formalize evaluation o Evaluation of plant modifications 5

Potential Application and Development Status, cont.

o Current and Potential Features (Ref. ML14072A211) o One-way sensitivity, tornado plots (Step 6) o One-way sensitivity studies, UQ plots (Step 7) o One-way sensitivity: Spider Plots (Step 8) o Two-way (two at a time) sensitivity studies (Step 9) o Meta models (Step 10) (response surface correlation)

To support multi-attribute sensitivity and simplified analysis of plant response o Compliance with standard software quality assurance o Importance o Helps show the relative importance of parameters o Helps to identify potential errors (counterintuitive results) and thereby contributes to analysis quality 6

CASA Grande Sensi-vity Studies

John Hasenbein David Morton Jeremy Tejada Alex Zolan May 22, 2014 7

Sensitivity Studies

• Approach

• Boron fuel limit

• Fiber penetration function

• Head loss studies 8

10-Step Sensitivity Analysis Process

• Step 1: Define the Model

• Step 2: Select Outputs of Interest

• Step 3: Select Inputs of Interest

• Step 4: Choose Nominal Values and Ranges for Inputs

• Step 5: Estimate Model Outputs under Nominal Input Values

• Step 6: One-Way Sensitivity Analysis: Sensitivity Plots & Tornado Diagrams

• Step 7: One-Way Sensitivity Analysis: UQ Plots

• Step 8: One-Way Sensitivity Analysis: Spider Plots

• Step 9: Two-way Sensitivity Analysis: Two-way Sensitivity Plots

• Step 10: Metamodels & Design of Experiments 9

Step 1: Define the Model

• We wont detail CASA Grande here (Volume 3)

• Use CASA Grande to estimate probability of sump failure and boron fiber limit failure, conditional on small, medium & large breaks

• Estimate change in core damage frequency (CDF) in events/year due to GSI-191 issues using these failure probability estimates and corresponding frequencies

• All results here are conditional on all pumps working 10

Step 2: Select Outputs of Interest

• Change in core damage frequency (CDF)

• Sometimes, we report ratio of CDF estimate for a scenario to CDF estimate for baseline and call this the risk ratio

• Use stratified sampling on initiating frequency

• Use IID replications within each cell of stratification

• Use common random numbers across scenarios; i.e., use CRNs across specified changes in input parameters 11

Step 2: Outputs: Estimating CDF Indices and Sets:

i = 1,..., F index for cells stratifying frequency replications k = 1,..., N index for set of pump states Events:

SL, ML, LL small, medium, large LOCA PSk pumps in state k Fi initiating frequency in cell i S

sump failure B

boron "ber limit failure CD core damage Parameters:

fSL, fML, fLL frequency (events/CY) of a small, medium, large LOCA P(PSk) probability mass of PSk P(Fi) probability mass of Fi P(SlLOCA, Fi, PSk) estimate of probability of S given LOCA = SL, ML, orLL, Fi, PSk P(BlLOCA, Fi, PSk) estimate of probability of B given LOCA = SL, ML, orLL, Fi, PSk RBASE non-GSI-191 core damage frequency (events/CY)

RCD estimate of core damage frequency (events/CY) 12

Step 2: Outputs: Estimating CDF We report results with:

- fSL, fML, fLL from Volume 2s Table 4-1

- P(all pumps working)=1

- P(Fi ): Bounded Johnson fit to NUREG-1829 We form a variance estimate for the above estimator CDF

=

RCD RBASE

=

F X

i=1 N

X k=1 P(Fi)P(PSk)

• h fSL

• P(SlSL, Fi, PSk) + fSL

• P(BlSL, Fi, PSk)

+fML

• P(SlML, Fi, PSk) + fML

• P(BlML, Fi, PSk)

+fLL

• P(SlLL, Fi, PSk) + fLL

• P(BlLL, Fi, PSk) i 13

Step 3: Select Inputs of Interest Amount of Latent Fiber in Pool: Existing dust/dirt in containment, based on plant measurement. Assumed to be in the pool at start of recirculation, uniformly mixed. During fill up, latent debris available to penetrate sump screen.

Boron Fiber Limit: Refers to threshold where boron precipitation occurs for cold leg breaks. Fiber limit comes from vendor testing that shows no pressure drop occurs with full chemical effects. Assume all fiber that penetrates sump screen deposits uniformly on core.

Debris Transport Fractions in ZOI: Refers to debris transport fractions involving three-zone ZOI. Each insulation type has characteristic ZOI divided in three sections to account for type of damage within each zone.

14

Step 3: Select Inputs of Interest Chemical Precipitation Temperature: CASA Grande assumes that, once a thin bed of fiber forms on strainer, chemical head loss factors apply when pool temperature reaches precipitation temperature.

Total Failure Fraction for Debris Outside the ZOI: CASA Grande uses table of total failure fractions applied to transport logic trees. Fraction of each type (fiber, paint and coatings, etc.) that passes to the pool are used to understand what is in the pool as a function of time during recirculation.

Chemical Head Loss Factor: Used as a multiplier on conventional head loss calculated in CASA Grande. Multiplier is applied if thin bed is formed and pool temperature is at or below precipitation temperature.

15

Step 3: Select Inputs of Interest Fiber Penetration Function: Fraction of fiber that bypasses the ECCS sump screen as a function of the amount of fiber on the screen.

Size of ZOI: ZOI defined as direct function (multiplier) of break size and nominal pipe diameter; e.g., for NUKON fiber, ZOI is 17 times break diameter. ZOI is spherical unless break is not DEGB, in which case it is hemispherical. Truncated by any concrete walls within the ZOI.

Time to Turn Off One Spray Pump: If three spray pumps start, then by procedure one is secured. Time to secure the pump is governed by operator acting on the conditional action step in procedure.

16

Step 3: Select Inputs of Interest Time to Hot Leg Injection: Similar to the spray pump turn off time, the time to switch one or more trains to hot leg injection operation is governed by procedure.

Strainer Buckling Limit: Limit is the differential pressure across ECCS strainer at which strainer is assumed to fail mechanically. This limit is based on engineering calculations that incorporate safety factor.

Water Volume in the Pool: Depending on break size, amount of water in pool, as opposed to amount in RCS and other areas in containment, varies. Smaller breaks tend to result in less pool volume than larger breaks.

17

Step 3: Select Inputs of Interest Debris Densities: Depends on amount and type of debris that arrives in pool. These densities are used in head loss correlations to calculate, for example, debris volume.

Time Dependent Temperature Profiles: Temperature of water in sump affects air release and vaporization during recirculation. Time-dependent temperature profile comes from coupled RELAP5-3D and MELCOR simulations depending on break size.

Spray Failure Fraction for Debris Outside ZOI: CASA Grande uses a table of failure fractions applied to transport logic trees. Fractions of each type of debris that passes to pool are used to understand what is in pool as function of time during recirculation. The spray failure fraction is fraction of failed coatings that wash to pool during spray operation.

18

Step 4: Nominal Values and Ranges for Inputs Input Parameter

Level 1

Level 2

Level 3

Level 4

Latent Fiber (63)

12.5

6.25

25

50

Boron Fiber Limit (g/FA)

7.5

4

15

50

Debris Transport Inside ZOI

Base

Low

High

Water Volume in Pool

Base

-10%

+10%

Chemical Precipita-on Temp (oF)

140o

160o

Total Failure Frac-on Outside ZOI

Base

Low

Chemical Head Loss Factor

Base

+50%

Fiber Penetra-on Func-on

Base

High

ZOI Size

Base

-33%

Turn o 1 Spray Pump (min.)

20

1440

Hot Leg Injec-on (min.)

345

450

Strainer Buckling Limit (6. H2O)

9.35

9.6

Debris Density (lbm/63)

Base

+25%

Temperature Pro"les (oF)

Base

-5%

Spray Transport Frac-on

6%

12%

19

Step 5: Estimate Outputs Under Nominal Values of Inputs Sensi7vity Measure

Expected

Direc7on Mean CDF

95% CI

Half-Width

95% CI

Low Limit

95% CI

Upper Limit

CI HW  %

of Mean

0 Baseline

None

1.817E-08

1.914E-09

1.626E-08

2.009E-08

10.53%

20

Step 6: One-Way Sensitivity Analysis Sensi7vity Measure

Expected

Direc7on

Mean CDF

0.95-level CI HW  % of

Mean

0

Baseline

N/A

1.817E-08

10.53%

1 Latent Fiber Low (6.25 6^3)

Decrease

1.905E-08

10.12%

2 Latent Fiber High (25 6^3)

Increase

1.669E-08

10.61%

3 Latent Fiber Very High (50 6^3)

Increase

3.394E-08

42.63%

4 Boron Low (4.0 g/FA)

Increase

1.690E-06

67.79%

5 Boron Very High (50 g/FA)

Decrease

1.308E-08

10.80%

6 Boron High (15 g/FA)

Decrease

1.329E-08

10.65%

7 Debris Transport Inside ZOI High

Increase

7.896E-08

28.50%

8 Debris Transport Inside ZOI Low

Decrease

1.241E-08

12.03%

9 Chemical Temp High

Increase

1.905E-08

10.17%

10 Debris Transport Outside ZOI Low

Decrease

1.770E-08

10.61%

11 Chemical Head Loss Factors High

Increase

2.287E-08

8.85%

12 Penetra-on: Low Envelope of Filtra-on Func-on

Increase

1.552E-07

10.93%

13 ZOI Size Small

Decrease

6.795E-09

12.18%

14 Turn O 1 Spray Longer

Decrease

1.569E-08

11.23%

15 Hot Leg Injec-on Longer

Increase

1.962E-08

9.96%

16 Strainer Limit Higher

Decrease

1.639E-08

10.99%

17 Water Volume Low

Increase

2.001E-08

10.13%

18 Water Volume High

Decrease

1.655E-08

10.73%

19 Debris Density High

Increase

2.567E-08

9.17%

20 Temperature Pro"les Low

Increase

1.963E-08

10.14%

21 Debris Transport Outside ZOI High

Increase

1.798E-08

10.65%

21

Step 6: One-Way Sensitivity Analysis 0.10

1.00

10.00

100.00

1,000.00

Boron Fuel Limit (4.0 g/FA - 50 g/FA)

Penetra-on Low Envelope

Debris Transport Inside ZOI

ZOI Size Small

Latent Fiber (6.25 6^3 - 50 6^3)

Debris Density High

Chemical Head Loss Factors High

Water Volume

Turn O 1 Spray Longer

Strainer Limit Higher

Temperature Pro"les Low

Hot Leg Injec-on Longer

Chemical Temp High

Total Failure  % Outside ZOI Low (80%)

Spray Transport  % Outside ZOI High (12%)

Ra-o of Risk under the Scenarios to Risk under Nominal Parameter Values

Scenario Descrip-ons

Tornado Diagram: Total CDF

Decreased Parameter Values

Increased Parameter Values

Increasing Risk

Decreasing Risk

22

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

100.0

1000.0

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

Risk Ra-os

Boron Fuel Limit (g/FA)

CDF (Total)

Mean Risk

Baseline

Increasing Risk

Decreasing Risk

23

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

100.0

1000.0

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

Risk Ra-os

Boron Fuel Limit (g/FA)

CDF (Vessel)

Mean Risk

Baseline

Increasing Risk

Decreasing Risk

24

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

Risk Ra-os

Boron Fuel Limit (g/FA)

CDF (Sump)

Mean Risk

Baseline

Increasing Risk

Decreasing Risk

25

Step 6: One-Way Sensitivity Analysis 0.55$

0.6$

0.65$

0.7$

0.75$

0.8$

0.85$

0.9$

0.95$

1$

0$

500$

1000$

1500$

2000$

2500$

3000$

3500$

4000$

Filtra'on*

Strainer*Mass*in*Grams*

Test$1:$353gpm$

Test$2:$353gpm$

Test$3:$353gpm$

Test$5:$358gpm$

Test$7:$220gpm$

Fit$

Upper$Envelope$

Lower$Envelope$

Filtration Function Envelope 26

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

100.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Risk Ra-os

Fiber Envelope (0-Lower, 1-Upper)

CDF (Total)

Mean Risk

Increasing Risk

Decreasing Risk

27

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

100.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Risk Ra-os

Fiber Envelope (0-Lower, 1-Upper)

CDF (Vessel)

Mean Risk

Baseline

Increasing Risk

Decreasing Risk

28

Step 6: One-Way Sensitivity Analysis 0.1

1.0

10.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Risk Ra-os

Fiber Envelope (0-Lower, 1-Upper)

CDF (Sump)

Mean Risk

Baseline

Increasing Risk

Decreasing Risk

29

Step 6: One-Way Sensitivity Analysis

• Alternative distributions used for chemical head loss factor:

1.

No chemical head loss 2.

Factors constant at 1x mean (S=2.25/M=2.50/L=3.00) 3.

Factors constant at 2x mean (S=3.50/M=4.00/L=5.00) 4.

Factors constant at 3x mean (S=4.75/M=5.50/L=7.00) 5.

Truncated exponential (S=6/M=3.5/L=2.25) at tail probability of 1E-5 6.

Truncated exponential (S=3/M=2.5/L=2.25) at tail probability of 1E-5 7.

Truncated normal (Mean, St Dev = 3x Mean)

Means have base case values of (S=2.25/M=2.50/L=3.00) 30

Step 6: One-Way Sensitivity Analysis 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Ra-o of Total CDF to Base Case

Distribu-on of Chemical Head Loss Factor

Total CDF

Min Temp 140

No Minimum Temp

Baseline

Increasing Risk

Decreasing Risk

31

1.000

0.500

0.333

0.167

0.000

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

4.0

5.0

6.0

7.0

8.5

Filtra7on Func7on

CDF

Fiber Penetra7on Limit (g/FA)

CDF (Total) as a Func7on of Fiber Penetra7on Limit and Filtra7on Func7on

1.E-09-1.E-08

1.E-08-1.E-07

1.E-07-1.E-06

1.E-06-1.E-05

1.E-05-1.E-04

Step 9: Two-Way Sensitivity Analysis 0 - 1.E-08

32

1.000

0.500

0.333

0.167

0.000

4.0

5.0

6.0

7.0

8.5

Filtra7on Func7on

CDF

Fiber Penetra7on Limit (g/FA)

CDF (Total) as a Func7on of Fiber Penetra7on Limit and Filtra7on Func7on

1.E-09-1.E-08

1.E-08-1.E-07

1.E-07-1.E-06

1.E-06-1.E-05

1.E-05-1.E-04

0 - 1.E-08

Step 9: Two-Way Sensitivity Analysis 33

1.000

0.500

0.333

0.167

0.000

4.0

5.0

6.0

7.0

8.5

Filtra7on Func7on

CDF

Fiber Penetra7on Limit (g/FA)

CDF (Vessel) as a Func7on of Fiber Penetra7on Limit and Filtra7on Func7on

1.E-09-1.E-08

1.E-08-1.E-07

1.E-07-1.E-06

1.E-06-1.E-05

1.E-05-1.E-04

0 - 1.E-08

Step 9: Two-Way Sensitivity Analysis 34

ExplainingSubtleModelingTrends BruceLetellier-AlionScience JeremyTejada-UniversityofTexasAustin 35

Nonintuitive Trends ExtensiveusageofCASAGrandeforparameterstudiesrevealsfour(4) subtlenonintuitive trendsinquantitativerisk TwoissueswereopenedasErrorReports.Twoissueswereinvestigated duringparameterstudy.Alldispositioned usingcasestudyanalysis:

- ER01-UnqualifiedCoatingsSprayFraction

• IncreasingthefractionofUCtransportundersprayleadstoslight reductioninrisk

- ER03-FiberInventoryMassConservation

• Overtime,fibermassincreasesslightly

- PS01-LatentFiberEffectatT0

• Increasinglatentfiberslightlydecreasesrisk

- PS02-TimeStepEffect

• Decreasingtimestepcansignificantlydecreaserisk 36

ER01 - Unqualified Coatings Spray Fraction Parameterstudiesoftransportfractionsindicatethatincreasingthe6%

spraywashdown fractionto12%forfailedepoxyslightlyreducesrisk (1%Reduction).

Spreadsheetcalculationsforassumedinventoryoffailedcoatings showsverydefinitereductioninSV forincreasedsprayfractionfrom6%

to25%.

Holdsforbothlinearmassandvolumeweightingandforquadratic volumeweighting.Simplycompetitionbetweenparticulateproperties.

SV istheamountofdragareaperunitsoliddebrisvolume.SV is independentofporosity.MoredebrisdoesnotimplyhigheraverageSV.

Aproperformalismwouldusetotalsurfacearearatherthanaverage surfacetovolumeratiosothatmoreofanythingalways addsdrag.

37

ER01-UnqualifiedCoatingsSpray Fraction(example)

Spherical Diam Material Density (kg/m3)

Initial Mass (kg)

Initial (m1)

Final Mass (kg)

Final (m1) 1 10 1490 100 100 2

150 1986 25 30 512,000 1581 V

S

• Surfacetovolumeratiocandecreasewhentheproportion oflargerparticlesincreases(volumeincreasesfasterthan area)

• TrueatSTPforsprayfractionsbecauselargeinventoryof 10menamelhaszerosprayfraction(otherparticulates increaseinproportionandSV decreases) 38

ER03 - Fiber Inventory Mass Conservation

• Parameterstudiesandcodeverification exercisesshowthatfiberinventoryincreases slightlyoverthe36hcalculation

• Explicittimeforwardintegrationuses leadingconcentrationsforeachtimestep.

Coarseresolutiondeliversartificialmassat eachtimestepthataccumulatesaboveinitial inventory.

• Smallertimestepsreducethiseffect.

39

PS01 - Latent Fiber Effect at T0

• Parameterstudiesoflatentfiberquantityshow thatincreasinglatentfiberslightlydecreasesrisk.

• Fiberfiltrationandsheddingmodelaccountsfor improvedfiltrationwithincreasingdebrisload.

• Morelatentfiberinitializesslightlyhigher filtrationatbeginningofrecirculation

• Useroptionaddedtoallowsomefractionof latentfibertopassthroughthestrainer.

40

PS01 - Latent Fiber Effect at T0 (cont) 1.0E08 1.5E08 2.0E08 2.5E08 3.0E08 3.5E08 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 TotalCoreDamageFrequency LatentFiber(ft3)

SensitivityPlot:CommonRandomNumbers Mean Risk Decreasing Risk IncreasingRisk 41

PS02 - Time-Step Effect

• Reductionoftimestepfrom5minto1minfoundto reducequantitativeriskbyafactorof1.5.

• Explicttimeforwardintegrationintroducesnumerical diffusionthatadvancesdebristothestrainerartificially rapidly.

• NPSHrelatedfailuresoccurbeforereductionin temperatureregainsmargin.

• Possiblenonconservatismmaybeintroducedby improvedfiltrationonthedebrisbedthatprotectscore.

Nonumericalevidencethatthisdominates.

42

PS02-TimeStepEffectTrend 43

Summary:

• Thefournonintuitiveobservationsdiscussedhere havebeenexplainedatafundamentallevel

• Changesinnumericalapproximationsandphysical descriptionscaneliminateundesiredbehavior

• Subtletrendsrevealedinmodelinteractions

• Essentialtoconfirmingorcorrectingengineeringintuition

• SensitivitystudiescreateessentialQAopportunities toexercisephysicalmodelsoverfullparameter ranges

- Identifyinputerrors

- Identifycodelevelerrors 44

Conclusions

• Summarized approach to sensitivity analyses

• Demonstrated the approach on several parameters

• Reviewed and explained counterintuitive results observed with certain parameters 45