2015 revision of the favor* probabilistic fracture ... · pdf file17.06.2015 ·...

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2015 Revision of the FAVOR* Probabilistic Fracture Mechanics

Computer Program (v15.1)

Presented by Mark KirkNRC/RES/DE/CIB

Richard Bass, Terry Dickson, and Paul Williams

ORNL/NRC ProSaMM Program Oak Ridge National Laboratory

NRC/Industry MeetingJune 2-4, 2015

*FAVOR – Fracture Analysis of Vessels – Oak Ridge

2 Quality of Science_1408

Presentation Overview

• Background on FAVOR

• Current work to verify changes to draft FAVOR v15.1- Re-analysis of problem set from EPRI draft report*- Analysis of infinite-flaw verification matrix (16 problems);

compare ABAQUS vs FAVOR solutions- Confirmation of backward compatibility with previous

results

• Plans for release of FAVOR v15.1/rc1

*Gamble et al, EPRI – Sensitivity Study for the Effect of Vessel R / t and Flaw Aspect Ratio on CPF For Small Circumferential Inside Surface Flaws in Reactor Pressure Vessels(DRAFT August 4, 2014)


BACKGROUNDFracture Analysis of Vessels – Oak Ridge (FAVOR)

The NRC-sponsored FAVOR code performs deterministic and risk-informed probabilistic fracture analyses of nuclear reactor pressure vessels (RPVs) based on linear-elastic fracture mechanics (LEFM).

FAVOR addresses• normal operational transients

(e.g., start-up/shutdown/leak tests)

• upset conditions (e.g., pressurized thermal shock events),

• Inner-surface, embedded, and outer-surface flaws, and

• Cladding effects

Monte Carlo

Kernel


BACKGROUND: Range of conditions addressed by FAVOR SIFICs (stress intensity factor influence coefficients) for surface-breaking flaws (FAVOR version 15.1)

• semi-elliptical flaws with 0.01 a/t 0.5 normalized flaw depths and 2 L/a 10 aspect ratios

• infinite axial and circumferential 360-degree continuous flaws with 0.01 a/t 0.95

• inner and outer surfaces of RPV wall

• Ri /t ≈ 10 (PWR) and Ri /t ≈ 20 (BWR)

• inside surface cladding layer included

(embedded flaws not discussed here)

a = flaw depth; t = wall thickness; L = flaw length; Ri = inner radius of RPV


CURRENT WORK: Overview of revisions to FAVOR v15.1 that were motivated by results from studies in 2014-15 (EPRI and ORNL)Finite-length flawsCoding error - or “bug” - was identified using results found in EPRI report (requiring a fix to FAVOR)

Bug affects calculation of applied KI factors for inner surface-breaking flaws for R/t in the interval 10 < R/t ≤ 20, i.e., does NOT affect R/t = 10• Only an issue for surface breaking flaws

Bug does not alter previous results that did not use interpolation• PTS re-evaluation studies• Recent shallow-flaw report for Appendix G

Infinite/continuous flawsImproved FAVOR v15.1 by addressing deficiencies in original SIFICs identified while investigating “bug”

Calculation of new KI factors for ∞ flaws (requiring significant code enhancements and new SIFIC database)


CURRENT WORK [1]: Error in a pointer was identified & fixed

Crack Depths where SIFICs calculated

Applied KI* Fraction of wall thickness (a/t) crack depth (inches)*for (R / t) = 10 for (R / t) = 20 for (R / t) = 10 for (R / t) = 20

.010 .010 0.073 0.073 1.460.0184 0.0255 0.134 0.186 2.33.050 .050 0.365 0.365 3.29.075 .075 0.548 0.548 4.060.10 0.10 0.731 0.731 4.660.20 0.20 1.461 1.461 6.930.30 0.30 2.192 2.192 9.100.50 0.50 3.652 3.652 13.43*Values specific to problem illustrated in figure 23 in draft EPRI report

For ( Ri /t ) = 20, instead of selecting (a/t) = 0.0255, the code incorrectly selected (a/t) = 0.0184, i.e., the value for ( Ri /t ) = 10

Existing FAVOR calculations of KI for shallow flaws in vessels which require interpolation on Ri /t did not correctly position the flaw in the vessel wall.

For calculations involving the interpolation of SIFICs, the FAVLOAD module did not correctly account for the different relative flaw depths in the second position of the flaw depth vectors for Ri / t = 10 and Ri / t = 20 in the SIFIC databases .


Example: “Bug fix” removed inconsistency (crossover) illustrated in Fig. 23 of EPRI Report, for shallow, finite-length flaws with 10 < R / t ≤ 20

CURRENT WORK [2]: Entire problem set described in EPRI draft report being re-analyzed to verify that changes to FAVOR v15.1 resolve outstanding issues

FAVOR 15.1 resolves crossover illustrated in EPRI figure 23

crack depth (inches)

0.0 0.2 0.4 0.6 0.8pr

essu

re-in

duce

d K

I - a

spec

t rat

io 1

0

1

2

3

4

5

R / t = 10 R / t = 15 R / t = 20

finite length flaw aspect ratio = 10

FAVOR 12.1: EPRI figure 23 illustrates KI(x) for R / t = 20 crosses over KI(x) for R / t = 10


0.0 0.2 0.4 0.6 0.8

pres

sure

-indu

ced

KI -

ase

pct r

atio

= 1

0

1

2

3

4

5

R / t = 20

R / t =10 finite length flaw aspect ratio = 10

BEFORE AFTER


CURRENT WORK [3]: Implementation of new SIFIC database for ∞ circ. & axial inner surface-breaking flawssubjected to verification studies• Deficiencies identified in the original FAVOR methodology for calculating

KI factors for ∞ flaws• Old SIFIC solutions (handbook solutions) selected for comparison were

as much as 10% below ABAQUS solutions• Old SIFICs did not adequately account for cladding

• SIFICs for ∞ flaws now include cladding effects consistent with technique used for finite-length flaws

• 240 ABAQUS models/analyses performed to generate the new SIFIC database

• Implementation currently being verified through applications to • EPRI problem set • comprehensive analysis matrix (comparing ABAQUS and FAVOR

solutions)


CURRENT WORK [4]: Improved methodology for SIFICs for infinite flaws resolves issues raised by EPRI report Example: Cross-over inconsistency (i.e., R/t=15 not between R/t = 10 & 20) illustrated in Fig. 24 of EPRI report is resolved due to more consistent methodology for calculation of SIFIC for infinite flaws.

FAVOR 12.1: EPRI figure 24 illustrates crossover


0.0 0.2 0.4 0.6 0.8

Pres

sure

- In

duce

d K

I at

T =

60

F (t

= 80

0 m

inut

es) )

0

1

2

3

4

5

R / t = 15

R / t =20

R / t =10

infinite length circumferential flaw

FAVOR 15.1 resolves crossover illustrated in EPRI figure 24


0.0 0.2 0.4 0.6 0.8

Pres

sure

- In

duce

d K

I at

T =

60

F (t

= 80

0 m

inut

es)

0

1

2

3

4

5

R / t = 10 R / t = 15 R / t = 20

infinite length circumferential flaw

BEFORE AFTER


CURRENT WORK [5]: Verification studies compare ABAQUS and FAVOR v15.1 solutions for various geometric parameters to ensure accuracyAnalysis matrix includes variations in flaw orientation/depth, clad thickness, and Ri /t

Verification Nominal Flaw Aspect Flaw Depth ActualTest Matrix Ri/t Orientation Ratio a/t t clad t R i a R i/tCase No. (‐) (‐) (‐) (‐) (inches) (inches) (inches) (inches) (‐)

1 10 axial 0.035 0.156 8.5 86 0.2975 10.1182 10 axial 0.035 0.25 8.5 86 0.2975 10.1183 10 axial 0.5 0.156 8.5 86 4.25 10.1184 10 axial 0.9 0.25 8.5 86 7.65 10.1185 10 circumferential continuous 0.035 0.156 8.5 86 0.2975 10.1186 10 circumferential continuous 0.035 0.25 8.5 86 0.2975 10.1187 10 circumferential continuous 0.5 0.156 8.5 86 4.25 10.1188 10 circumferential continuous 0.9 0.25 8.5 86 7.65 10.1189 20 axial 0.035 0.156 6.125 126.4 0.2144 20.63710 20 axial 0.035 0.25 6.125 126.4 0.2144 20.63711 20 axial 0.5 0.156 6.125 126.4 3.0625 20.63712 20 axial 0.9 0.25 6.125 126.4 5.5125 20.63713 20 circumferential continuous 0.035 0.156 6.125 126.4 0.2144 20.63714 20 circumferential continuous 0.035 0.25 6.125 126.4 0.2144 20.63715 20 circumferential continuous 0.5 0.156 6.125 126.4 3.0625 20.63716 20 circumferential continuous 0.9 0.25 6.125 126.4 5.5125 20.637


PLANS: A few steps remain before issuing FAVOR v15.1

• Complete verification studies described in foregoing slides

• Complete studies to confirm backward compatibility with previous results for internal, external and embedded flaws

• Revise the Theory Manual to reflect changes in the code

Release FAVOR v15.1 at end of June 2015

2015 revision of the favor* probabilistic fracture ... · pdf file17.06.2015 ·...

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