Global Nuclear Fuel

Verification of LS-DYNA Finite Element Impact

Analysis by Comparisonto Test Data and Classic First

Principle Calculations

Andy Langston and Victor SmithPATRAM 20103-8 October, 2010, London, England, UK

Introduction

Licensing History:

•Licensed in Japan in the mid 1990’s.

•Licensed in USA in 2005 as replacement for GNF and AREVA first generation packages.

•2007 – Present, GNF and Westinghouse licensing package in EU. During the licensing review additional information requested concerning the impact performance of the package with respect to IAEA TS-R-1.

Development:

•RAJ-II BWR fresh fuel transport package developed in Japan as replacement for first generation design.

•Drop tested in Japan for METI certification.

•Drop tested in USA at Oak Ridge, TN facility forNRC SAR.

•Drop tested in France by Japanese tovalidate loose rod container.

LS-DYNA ModelSolid Model:

•Solid model developed in AutoDesk Inventor.

•Model developed from fabrication drawings.

•Crushable materials modeledas solid objects.

•Sheet metal modeled as Surfaces.

Presentation3

LS-DYNA Model

FEA Model:

•Solid model imported into ANSYS Workbench.

•Model meshed with Workbench meshing tools.

•LS-DYNA keyword file createdIn ANSYS Mechanical.

•Crushable materialsmodeled with solid elements.

•Sheet metal modeled with shell elements.

•Total of 534853 nodes and 442331 elements

Package Assembly

Space Frame

Inner Container with Honeycomb

Block

Rigid Fuel Bundle Payload

LS-DYNA Model

Material Properties:

•Honeycomb and Ethafoamproperties obtained through laboratory testing.

•Three temperature ranges test including –40°C, 21°C, and 77°C that represents cold, ambient, and hot conditions.

•LS-DYNA material types *MAT_HONEYCOMB and *MAT_CRUSHABLE_FOAM

Honeycomb Engineering Stress-

Strain Properties

True Stress Versus True Strain for 304 SS

Ethafoam Engineering Stress-Strain Properties.

0

50

100

150

200

250

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Str

ess

(psi

)

Strain (in/in)

Nominal (21°C) Hot (77°C) Cold (-40°C)

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Tota

l Tru

e St

ress

(ps

i)

Plastic True Strain (in/in)

0

10

20

30

40

50

60

70

80

90

100

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160

Stre

ss (p

si)

Strain (in/in)

Nominal (21°C) Hot (77°C) Cold (-40°C)

LS-DYNA Model

Benchmark with Test Results:

•LS-DYNA honeycomb material property defines an instantaneous modulus of elasticity that accounts for the column buckling of the honeycomb cell.

•The instantaneous modulus of elasticity was adjusted until the initial peak acceleration matched the French top drop test results.

•The French drop test represents the best recorded data for any of the RAJ-II test programs.

Benchmark of LS-DYNA with Drop Test Results

-100

-50

0

50

100

150

200

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 0.005

Acce

lerati

on (g

)

Time (s)

RAJ-III Top Drop 21°C

Analysis Results

Side Drop:

•Maximum accelerations occur when lightest fuel bundles is coupled with coldest temperature (-40°C). Accelerations increase 5%.

•Heaviest fuel bundle coupled with hot conditions results in 9% decrease in accelerations.

•The peak acceleration is 340g at 500 Hz.

Side Drop Accelerations(Cold, Ambient and Hot Conditions)

-100

-50

0

50

100

150

200

250

300

350

400

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016A

ccel

erat

ion

(g)

Time (s)

Side Ambient Nominal Side Hot Heavy Side Cold Lite

Analysis Results

Top Drop:

•Like the side drop maximum accelerations occur when lightest fuel bundles is coupled with coldest temperature (-40°C).

•The peak acceleration is 186g at 500 Hz.

Top Drop Accelerations(Cold, Ambient and Hot Conditions)

-50

0

50

100

150

200

0 0.0025 0.005 0.0075 0.01 0.0125 0.015 0.0175 0.02 0.0225 0.025Ac

cele

ratio

n (g

)

Time (s)

Top Ambient Nominal Top Hot Heavy Top Cold Lite

Analysis ResultsSlap-down/Whiplash:

•The analysis results show that the RAJ-II is more efficient during the slap-down event than the flat top drop.

•During slap-down, honeycomb surface area is initially only available at the point impact and gradually increases as the impact progresses.

•Due to the geometry of the packaging, the initial peak acceleration is much higher during the flat top or side events.

Top Drop versus Slap-down Accelerations

-20

0

20

40

60

80

100

120

140

160

0 0.0025 0.005 0.0075 0.01 0.0125 0.015 0.0175 0.02 0.0225 0.025

Acce

lera

tion

(g)

Time (s)

Slap Down Top Ambient Nominal

Benchmarking

• The RA-3D package is a first generation design similar to the RAJ-II

• RA-3D drop tests included natural uranium bundles of common designs to perform the regulatory testing.

Comparison of LS-DYNA and RA-3D Test

Comparison with Historic Test Results:

•To benchmark the LS-DYNA analysis results, comparison to historic drop test is used.

• Good agreement between the RAJ-II LS-DYNA analysis results and RA-3D test results including the impact duration. The peak acceleration of the RA-3D is higher than that of the RAJ-II because of increased honeycomb surface area during the initial impact.

Benchmarking

LS-DYNA, RA-3D Test, and Hand Calculations

Impact Predictions with Classic First Principle Calculations:

•To further benchmark these results, a hand calculation predicts the peak acceleration.

• Benchmarking possible because of the simple geometry of the RAJ-II and RA-3D honeycomb design.

• Methodology developed by Mindlin established the basis for predicting acceleration of packaged items. • Using this methodology able to

provide reasonable estimate.

‐100

0

100

200

300

400

500

600

0 0.003 0.006 0.009 0.012 0.015

Acce

lera

tion (

g)

Time (s)RAJ-II LS-DYNA Side Drop RA-3D Side Drop RA-3D EstimateRAJ-II Estimate RAJ-II Side Filtered

RAJ‐II Prediction (229g)

RA‐3D Prediction  (391g)

VerificationIndependent Verification using Classic First Principle Calculations:

•To further benchmark these results, a hand calculation predicts the peak acceleration.

• Using the Mindlinmethod, independent verification was performed to predict the initial and secondary impact during slap-down.

• The load was considered to be carried by only the cross section of the honeycomb block supported by the bottom of the container parallel to the acceleration.

• The estimate of the peak acceleration during the initial impact is within 2g of the acceleration predicted by LS-DYNA. The hand calculation estimates a lower acceleration for the secondary peak as compared to LS-DYNA. However, the hand calculation values closely corresponds to the values predicted by the computer model.

LS-DYNA Slap-Down Results Comparedto Hand Calculations

Conclusions

• This evaluation shows that testing, finite element analysis, and first principle calculations are all good methods for evaluating the performance of a package.

• With all methods, the key to good results is having well defined geometry and materials.

• When all three methods are utilized, it is possible to benchmark analytical models that can be used to further improve packaging design.