11/12/08 presentations by holtec international regarding ... · • structural otis discussed...

11/12/2008 1

HOLTECINTERNATIONAL

HI-STAR 180 OTIs

Presentation to NRCNovember 12, 2008

11/12/2008 2

HOLTECINTERNATIONALAgenda

• Introduction• Impact Limiter Benchmarking• Metamic HT Testing Update• Structural OTIs• Closure OTIs• Other OTIs Chapter 1, 7 and 8• Discussion / Closing

11/12/2008 3

HOLTECINTERNATIONAL

LS-DYNA Impact Limiter Benchmarking

Dr. Stefan Anton, Dr. John Zhai


11/12/2008 4

HOLTECINTERNATIONALOverview

• 1997: HI-STAR 1/4 scale drop tests• 1998: Analytical 2-D approach to simulate drop

conditions, used for HI-STAR 100 approval• 2007: 3-D transient FEM calculations to

benchmark LS-DYNA for Impact Limiter Qualification based on 1/4 scale drop tests

• June 2008: OTIs on HI-STAR 180, including comments on Impact Limiter Benchmarking

• September 2008: Holtec proposes an improved approach on LS-DYNA benchmarking

• Today: Presentation of Final Results

11/12/2008 5

HOLTECINTERNATIONAL

Unresolved HI-STAR 180 OTIs related to HI-STAR 100 Benchmarking

• 2-3 Hexahedron vs. Tetrahedron Elements• 2-4, 2-5 Material Properties• 2-6 Mesh Sensitivity• 2-7 Material Coordinate Systems• 2-9 Robust Model• 2-10 Overpack Connection• 2-11 through 2-14 Bolts

11/12/2008 6

HOLTECINTERNATIONALRevised Benchmarking

• Hexahedron vs. Tetrahedron Elements• Mesh Sensitivity• Material Properties• Component Benchmarking• Material Coordinate Systems

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HOLTECINTERNATIONALHex vs. Tet Elements

• Initial Model (TetElements)

11/12/2008 8

HOLTECINTERNATIONALHex vs. Tet Elements

• Revised Model (Hex Elements)

11/12/2008 9

HOLTECINTERNATIONALMesh Sensitivity

• Three simple impact problems, which characterize the various loading conditions of the impact limiter honeycomb– Normal Compression– Off-Axis Compression– Shear Load

• Each problem simulates a honeycomb block impacted by a rigid body dropped from 30 ft.

• Each problem is simulated multiple times, with different element sizes

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Normal Compression

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Off-Normal and Shear

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HOLTECINTERNATIONALMesh Sensitivity - Results

• Crush behavior is very insensitive to element size, even for extreme shear deformation

• Lower bound element sizes selected for full impact limiter models

• Using different impact orientations make results applicable to all honeycomb impact limiter – no further mesh sensitivity studies required

11/12/2008 13

HOLTECINTERNATIONALMaterial Properties

• Orthotropic material properties are used in the honeycomb LS-DYNA material model.

• Secondary strength properties of honeycomb are derived, or are based on the supplier’s estimates.

• The studies with a wide range of parameter variations show that those secondary properties have an insignificant effect on the impact limiter performance.

11/12/2008 14


Note: The a-, b-, and c-directions in the material model are equal to T-(or T1-), L-(or T2-), and W-directions of the honeycomb, respectively.

DerivedEstimated by SupplierLCCD- Shear strength in ca-direction

DerivedAvailableLCBC- Shear strength in bc-direction

DerivedAvailableLCAB- Shear strength in ab-direction

AvailableEstimated by SupplierLCC- Compressive strength in c-direction

AvailableEstimated by SupplierLCB- Compressive strength in b-direction

AvailableAvailableLCA- Compressive strength in a-direction

Bi-directionalcore

Unidirectionalcore

Required Properties for Honeycomb Material Model

11/12/2008 15


4.193.944.00Crush Depth (in)

155168.14165.45Maximum

Deceleration (g’s)

MeasuredUpper-Bound Properties

Lower-Bound PropertiesItem

Effects of Secondary Strength Properties on ¼-Scale HI-STAR 100 Drop Simulation Results (C.G.Over Corner)

11/12/2008 16

HOLTECINTERNATIONALComponent Benchmarking

• Standard honeycomb compressive and plate shear tests are simulated for the honeycomb material model component benchmarking. Load is applied slow enough to avoid significant inertial loads

• Component benchmarking is performed for various LS-DYNA Material Model/Element Form combinations and the best combination for HI-STAR 100 Benchmarking is identified.

11/12/2008 17

HOLTECINTERNATIONALComponent Benchmarking

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HOLTECINTERNATIONALMaterial Coordinate Systems

• The improved benchmarking model specifies the material coordinate system for each honeycomb block based on the orientation of the block.

• Results show an effect of a few percent difference in peak deceleration compared with the single material coordinate system approach used in the old benchmarking model.

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HOLTECINTERNATIONALMaterial Coordinate Systems

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HOLTECINTERNATIONALResults

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HOLTECINTERNATIONALConclusions

• LS-DYNA Benchmarking calculations completed successfully using the improved approach.

• No significant changes in results compared to earlier appraoch

• Benchmarks qualify LS-DYNA for determination of Rigid Body Acceleration and Impact Limiter Deformation.

11/12/2008 22

HOLTECINTERNATIONAL

METAMIC HT Update


11/12/2008 23

HOLTECINTERNATIONALMETAMIC HT Update

• Testing in process according to detailed test plan presented in June and September

• Slight delays in schedule, partly due to sample irradiation process

• All tests are expected to be finalized within 30 days

• Testing Results confirm the previously used parameters

HOLTECINTERNATIONAL

HI-STAR 180 STRUCTURAL OPEN TECHNICAL ISSUES

(USNRC Docket No. 71-9325)A Presentation to the SFST

byChuck Bullard

Principal EngineerHoltec InternationalNovember 12, 2008

November 12, 2008 2

HOLTECINTERNATIONALHistory

• Initial application submitted in January 2007

• Received NRC Letter with Open Technical Issues (OTI) in June 2008

• Structural OTIs discussed during NRC meetings held on 6/27/08 and 9/2/08

November 12, 2008 3

HOLTECINTERNATIONALOverview

• Structural qualification of HI-STAR 180 Package relies on transient LS-DYNA analyses and static ANSYS analyses– LS-DYNA is used to predict peak rigid body

decelerations and impact limiter crush behavior

– ANSYS is used to determine stress/strain levels in the cask components by applying peak decelerations from LS-DYNA

November 12, 2008 4

HOLTECINTERNATIONALOverview (cont.)

• LS-DYNA impact limiter model for HI-STAR 180 is consistent with latest HI-STAR 100 benchmark analysis– Identical material model for aluminum

honeycomb crush material (different property values)

– 100% hexahedral elements– Comparable mesh size– Locally oriented coordinate axes for each

aluminum honeycomb block

November 12, 2008 5


• LS-DYNA drop models account for maximum possible gaps between containment boundary and internal contents per the design drawings

• LS-DYNA model is also used to evaluate penetration as a result of the 1-meter puncture test

November 12, 2008 6


• ANSYS model is consistent with approved methodology for HI-STAR 100– Includes cask body, closure lids, closure bolts, fuel

basket, fuel basket shims, and fuel– Loading applied as global acceleration vector and/or

equivalent static pressure– Fixed boundary conditions simulate contact between

impact limiters and cask body• SAR will report stress and displacement results

from ANSYS and LS-DYNA solutions for comparison

November 12, 2008 7

HOLTECINTERNATIONALOTI 2-1

• OTI– Predictions from 3 to 5 accelerometers sufficient for

benchmarking of LS-DYNA model?• Path forward

– Staff agrees it is sufficient for rigid body deceleration and impact limiter crush predictions

– Static FEA is performed using ANSYS to determine stresses and displacements in cask and fuel basket based on peak decelerations from LS-DYNA simulations

November 12, 2008 8


• OTI– Different result if acceleration output filtered rather

than differentiated velocity output filtered• Path forward

– With flexible bodies, acceleration response has additional high frequency components from the numerical solution. Similar conclusion has been reached by others (www.ohiocae.com/ls-dyna-transport-cask.htm). Excerpt provided below:

November 12, 2008 9

HOLTECINTERNATIONALOTI 2-2 (cont.)

• “The displacements and velocities usually do not contain significant noise in the time histories. However, the accelerations usually produce a significant level of noise. Since the accelerations are related to the forces acting on the elements, and the elements have a significant level of oscillations, These oscillations give no indication of the accelerations associated with either deformation of the cask or the rigid body response of the cask ends”

November 12, 2008 10


– Rather than filtering acceleration response at a low enough value to remove numerically induced high frequency oscillations, Holtec used differentiation of velocity (which had minimal oscillations)

– This approach successfully eliminated high frequency oscillations associated with acceleration response solely due to numerical analysis.



• OTI– Justify the use tetrahedral elements for aluminum

honeycomb impact limiter material• Path forward

– Benchmark analysis of HI-STAR 100 impact limiter has been reperformed in LS-DYNA using 100% hex elements

– HI-STAR 180 model also uses 100% hex elements



• OTI– Justify the selective use of material properties for the aluminum

honeycomb impact material• Path forward

– HI-STAR 100 benchmark analysis has been revised to properly account for the compressive and shear strength properties of honeycomb material in three directions

– Conservative upper and lower bound strength properties are analyzed where physical test data is not available for a particular crush/shear direction

– Similar approach is used for HI-STAR 180 drop analyses; upper and lower bound properties are used as necessary based on the results of the HI-STAR 100 benchmark analysis



• OTI– Justify the use of isotropic material properties for the

aluminum honeycomb• Path forward

– HI-STAR 100 benchmark analysis has been revised so that the material properties for the aluminum honeycomb are uniquely specified in 3 orthogonal directions

– Same approach is used for HI-STAR 180 drop analyses



• OTI– Mesh sensitivity of aluminum honeycomb material

• Path forward– A mesh sensitivity study has been performed as part

of the revised HI-STAR 100 benchmark analysis– Mesh size for HI-STAR 180 impact limiter model is

based on the findings from the HI-STAR 100 mesh sensitivity study



• OTI– Demonstrate that the use of globally oriented material axes is

appropriate for bechmark analysis• Path forward

– Previous benchmark model used global cartesian coordinate system that moved with the elements (confirmed by Livermore software)

– HI-STAR 100 benchmark model has been revised to include a locally oriented cartesian coordinate system for each block of aluminum honeycomb material

– Use of a cylindrical coordinate system is not correct since, in practice, “wedges” are cut from a rectangular block

– Same approach is used for HI-STAR 180 impact limiter model



• OTI– Does precrush alter properties?

• Path forward– Precrushing is performed only for a thin layer of material near

target contact surface and is part of manufacturer’s production process

– No change to global response of impact limiter as demonstrated by 1/8 scale tests during HI-STAR 100 test series

– Once spike is overcome, response is like elastic-perfectly plastic material until lock-up. This is the material behavior that has been modeled in LS-DYNA. The following figures are reproduced from the HI-STAR 100 SAR.





• OTI– Is impact limiter material model robust enough to simulate range

of honeycomb materials likely to be used?• Path forward

– HI-STAR 100 benchmark analysis has been updated to include a component benchmarking of aluminum honeycomb material which demonstrates that the material model chosen is capable of reproducing the manufacturer’s test data

– Impact limiter material model used for the HI-STAR 100 is also used for the HI-STAR 180

– Honeycomb materials to be used must lie within the range of acceptability defined by the SAR and supported by the analyses



• OTI– Provide a more thorough explanation of the

methodology used to connect the impact limiters to the overpack model

• Response– Impact limiters are attached to overpack model

through the impact limiter attachment bolts, which are explicitly modeled





• OTI– Mesh sensitivity of bolt model. Is there a “hard spot” caused by

abrupt mesh change that causes premature failure? • Path forward

– Existing bolt model for the benchmark analysis is adequate sinceit remains intact or fails consistent with the HI-STAR 100 drop tests. However, it is no longer the intent of the benchmark analysis to validate the attachment bolt model. Therefore, the mesh size of the bolt model is not critical.

– In the HI-STAR 100 drop tests, the impact limiter attachment bolts failed due to shear. However, in the HI-STAR 180 design, the attachment bolts do not resist shear loads because of the presence of oversized thru holes in the impact limiter backbone.

– See OTI 2-13 for consideration of axial bolt loads



• OTI– Justify use of minimum reduction of area values in

stage 3 benchmark for impact limiter bolts• Path forward

– Impact limiter attachment bolts no longer rely on benchmarking. See OTIs 2-11 & 2-13.



• OTI– Justify statement in HI-STAR 180 SAR or provide the

results of benchmarking the bolt model• Path forward

– SAR statement will be deleted– HI-STAR 180 impact limiter is being modified so that

the impact limiter attachment bolts are not in the primary load path during a drop accident at any orientation and remain elastic under all conditions



• OTI– Demonstrate how an un-validated bolt model

in LS-DYNA assures greater confidence and assurance than a physical test w.r.t. seal integrity

• Path forward– SAR statement referenced in the OTI will be

deleted



• OTI– Provide control processes and inspection for Metamic

• Path forward– Commitment is made to achieve certain critical

characteristics for Metamic (minimum guaranteed values).

– SAR will be updated to include a description of the manufacturing control processes and inspection steps



• OTI– Justification of methodology change from tetrahedral

element mesh to all hexahedral element mesh.• Path forward

– HI-STAR 100 benchmark analysis has been reperformed using 100% hex elememts for the impact limiter model

– HI-STAR 180 impact limiter model uses 100% hex elements consistent with the benchmark analysis



• OTI– Impact limiter attachment bolt mesh change

between HI-STAR 100 stage III benchmark report and HI-STAR 180

• Response– Impact limiter attachment bolts no longer rely

on benchmarking. See OTIs 2-11 & 2-13.


HOLTECINTERNATIONALOTIs 2-18/2-19

• OTI– Explanation of severe local panel deformations and

strains observed• Path forward

– Severe local panel deformations were caused by the reduction in cross section adjacent to the mouse holes.

– Fuel basket has been strengthened by eliminating “mouse holes” and increasing thickness of exterior panels.

– New HI-STAR 180 submittal will include fuel basket stress/strain results from LS-DYNA and ANSYS models



• OTI– Provide a discussion explaining why consideration of

gaps in an end drop are not applicable for evaluation of the fuel basket

• Path forward– HI-STAR 180 drop analyses are reperformed based

on maximum possible gaps between the cask containment cavity and its contents (fuel, fuel basket, fuel basket shims) for each drop orientation.

– Additionally, fuel rods are analyzed with a methodology based on NUREG-1864



• OTI– Provide 30 ft side drop LS-DYNA output files

considering maximum gaps• Path forward

– Revised analyses use maximum gaps– Computer output files will be provided



• OTI– Provide an analysis considering maximum gaps

between internal package contents in accordance with design drawings

• Path forward– Drawings will be revised to reduce maximum possible

gaps to the extent practical.– HI-STAR 180 drop analyses are reperformed based

on maximum possible gaps between the cask containment cavity and its contents (fuel, fuel basket, fuel basket shims) for each drop orientation.



• OTI– Provide justification for using visual examination of

contour plot fringe levels to report results• Path forward

– For the new HI-STAR 180 drop analyses, nodal averaging is turned off prior to generating stress contour plots in LS-DYNA

– The maximum reported stress for a particular component is based on the upper bound fringe level for the highest stressed element (as appropriate for the stress category).



• OTI– Provide additional justification that the numerical solutions are

converged• Path forward

– A mesh convergence study has been performed for the aluminum honeycomb impact limiter material as part of the HI-STAR 100 benchmark analysis. Mesh size for HI-STAR 180 impact limiter model is based on the findings from the benchmark analysis.

– Mesh convergence of impact limiter attachment bolts addressed in OTIs 2-11 & 2-13.

– Mesh convergence of fuel basket addressed in OTIs 2-30 & 2-31– Mesh convergence of monolithic shield cylinders addressed in

OTI 2-25



• OTI– Revise puncture drop analysis. Are shield cylinder

layers separate entities?• Path forward

– Puncture model is revised to incorporate finer mesh for puncture bar and monolithic shield cylinders at the point of impact.

– Amount of hourglassing energy has been minimized.– Shield cylinder layers are separate entities, which are

only joined along their outside diameter (where a weld is specified).



• OTI– Justify design life of 40 years

• Path forward– Holtec is not seeking certification of 40 year design

life. Certification is requested for 5 years.– SAR statement asserting “40 year design life” of the

HI-STAR 180 system will be deleted.– Holtec will continue to develop substantiating

information to support renewal of license in the future.



• OTI– Justify statement regarding use of polymeric material

with the same crush properties• Path forward

– Cited statement will be removed from the SAR when resubmitted



• OTI– Justify 7 degree slapdown angle

• Response– A 2-D parametric analysis has been

performed for the HI-STAR 180 to establish that the most adverse slapdown angle is 7-degrees.


HOLTECINTERNATIONALOTI 2-30/2-31

• OTI– Justify use of single layer thick shells with two

integration points• Path forward

– Characteristic width to panel thickness is 206mm/15mm =13.73, which qualifies the panel as a thin plate (per ASME Code).

– A comparison with a classical closed form plate solution is used to demonstrate mesh size convergence using the LS-DYNA thick shell element (see next slide).

– Number of integration points thru the thickness is increased to 10 (maximum permitted by LS-DYNA)


HOLTECINTERNATIONALOTI 2-30/2-31 (cont.)



• OTI– Justify 2 thru-thickness integration points in

thin shell elements in LS-DYNA models• Response

– Thin shell elements are used to model the impact limiter cover, ribs, and backbone structure.

– In the revised HI-STAR 180 drop analyses, the number of integration points thru the thickness is increased to 10 (maximum permitted by LS-DYNA)



• OTI– Why no failure strain limit imposed for Metamic?

• Path forward– Engineering failure strain is 6-8%; true failure strain is

approximately 20%– Previously LS-DYNA did not have the capability to

include a failure strain limit for thick shell elements. Latest version of LS-DYNA enables user to specify failure strain limit.

– Updated simulations use latest program version with appropriate failure strain limit.



• OTI– Provide analysis demonstrating that removing

fabrication welds in basket model is conservative

• Response– New structural model is consistent with

revised fuel basket drawings in all respects.



• OTI– Discussion of 10CFR 71.43(e), (g), and (h)

• Response– Sec. 1.1 answers 71.43(e) and 71.43(h).– Sec. 1.2.1.1.d and Table 3.1.1 answers 71.43(g)



• OTI– Fracture toughness requirements for lid bolts

• Path forward– SA564-630 has been chosen as final material for

bolts with SB637-N07718 as an option. Other bolt materials currently listed in tables, etc. will be removed.

– Charpy tests and ductility requirements will be added to the SAR for the SA564-630 material.



• OTI– Justify 15 ft-lb as Charpy energy for SA352-LCC

• Path forward– Holtec has well established procedure

• Use LS-DYNA to create a Charpy impact test specimen consistent with ASME Code requirements

• Perform iterative solution to determine failure strain limit that causes specimen to break at specified absorbed energy value

• Introduce the same size crack in monolithic shield shell in the most damaging location, apply the bounding puncture load, and demonstrate no crack propagation.

HOLTECINTERNATIONAL

HI-STAR 180 TYPE B(U) TRANSPORTATION PACKAGE

General/Misc. OTIs

Presentation to the USNRCby

Holtec International

November 12, 2008

2November 12, 2008

HOLTECINTERNATIONAL

Agenda

• OTI 1-1: 10CFR71 and 10CFR72• OTI 1-2: Seal Dimensions and Surface Finish• OTI 1-3: Canopy Type Personnel Barrier• OTI 7-4: Torque Numerical Values• OTI 7-7: Use of Appropriate Seal Material• OTI 7-9: Time-to-Boil and Fuel Drying Evaluation

3November 12, 2008

HOLTECINTERNATIONAL

OTI 1-1: 10CFR71 and 10CFR72• Holtec is not requesting storage approval under 10CFR72.• Holtec does seek to show in the SAR that the cask remains

transportable after a period of storage because the cask will indeed store fuel for up to 40 years before actual shipment as a transportation package.

• A total storage time of 40 years will still be observed if the cask is transported from one storage facility to another.

• Certification for transport is requested for 5 years. License renewal will include additional substantiating information as required yet the following considerations are already addressed in the cask design

– Closure seal materials are specified for transport and long-term storage – Inert helium environment between closure lids adds to corrosion protection– All seals are metallic seals (no elastomeric seals)– Heat load reduces significantly during 40 years of storage– No adverse effect of long-term storage prior to transport for all safety

functions.

4November 12, 2008

HOLTECINTERNATIONAL

OTI 1-2: Seal Dimensions and Surface Finish

• Drawings currently specifies seals as follows:– Inner Lid Main Seals: Seal and Seal Groove ID and OD and

Seal Groove Depth– Outer Lid Main Seals: Seal and Seal Groove ID and OD and

Seal Groove Depth– Same dimensions for all other containment boundary and

important to safety seals and corresponding grooves– Note 15 specifies seal finish to be 0.4 μm Ra (16 RMS) in a

circular lay patter.

– NRC to clarify what additional information is sought

5November 12, 2008

HOLTECINTERNATIONAL

OTI 1-3: Canopy Type Personnel Barrier

• The canopy type personnel barrier could potentially influence heat transfer from the cask (possibly more than a mesh type personnel barrier); therefore Holtec will include a thermal evaluation in the SAR.

6November 12, 2008

HOLTECINTERNATIONAL

OTI 7-4: Torque Numerical Values

• Table 7.1.1 specifies numerical values for both inner and outer closure lid bolts.

• Table 7.1.1 will be revised to specify numerical values for all other containment boundary and important to safety fasteners and plugs instead of “per seal manufacturer recommendation”. However, a note will be added to indicate that torque values are subject to change per seal manufacturer recommendation.

7November 12, 2008

HOLTECINTERNATIONAL

OTI 7-7: Use of Appropriate Seal Material

• SAR Section 2.2.1.1.6 specifies Nickel alloy cladding for seal shell material for transport after an extended storage period of 20 years or more.

• Chapter 7 will be revised to include the administrative checks/operational steps needed to verify that the appropriate seal type is installed prior to transport.

8November 12, 2008

HOLTECINTERNATIONAL

OTI 7-9: Time-to-Boil and Fuel Drying Evaluation

• A method of evaluating site-specific Time-to-Boil criteria and operational steps for users will be provided as requested.

• A thermal analysis will be performed to determine cladding temperature limits, time limits, and additional controls as necessary to ensure cladding integrity.

HOLTECINTERNATIONAL

HI-STAR 180 TYPE B(U) TRANSPORTATION PACKAGE

CLOSURE SYSTEM SAFETY FUNCTION, OPERATION, AND MAINTENANCE

Presentation to the USNRCby

Holtec International

November 12, 2008

2November 12, 2008

HOLTECINTERNATIONAL

Agenda

• HI-STAR 180 Containment and Closure System Overview

• Original Approach of Safety Function• Revised Approach of Safety Function

3November 12, 2008

HOLTECINTERNATIONAL

Overview of Containment Boundary• All containment boundary steels have high fracture toughness at very

low temperatures• ASME B&PV Code, Section III, Subsection NB for Design and

Manufacture

Outer Closure Lid and One Access Port(w/ bolts and seals)Inner Closure Lid

and Two Access ports(w/ bolts and seals)

Closure Flange

Containment Shell

Containment Baseplate

4November 12, 2008

HOLTECINTERNATIONAL

Overview of Double Lid Closure System

Outer Closure Lid

Inner Closure LidClosure Flange

• Metal to metal contact joints provide maximum protection against leakage under impulsive loading

• The double lid system facilitates monitoring of the leak tightness of the cask primary closure lid during long-term storage

68 bolts(each closure lid)

Space between inner and outer closure lids filled with 99.9% purity helium

5November 12, 2008

HOLTECINTERNATIONAL

Overview of Main Seals and Test Ports

Inter-Seal Test Port Plugwith Metallic Seal

Outer Closure Lid

• Each closure lid is equipped with two independent metallic seals• All metallic seals are highly corrosion resistant and seat on stainless

steel surfaces.

Lid Outer Seals

Stainless Steel Overlay

Inner Closure Lid Lid Inner Seals

All seals are specified with silver plated/clad stainless steel shell with nickel alloy springs (SAR Section 2.2.1.1.6). Nickel alloy shell required for extended storage periods (20 or more years) for conservatism.

6November 12, 2008

HOLTECINTERNATIONAL

Original Approach of Safety Function

• Leak-tight Containment – One lid must be leak-tight (ANSI N14.5)

• Moderator Exclusion – (10 CFR 71.55(e))– Both lids must be water-tight (criteria specified in SAR Section

8.1.4.2)• ALARA Oriented Operations and Maintenance

– All outer closure lid seals require pre-shipment leakage test (SAR Section 8.2.2 and Table 8.2.1).

– Pre-shipment leakage test however is not strictly required for innerclosure lid seals due to the protection against corrosion afforded by the helium in the inter-lid space (SAR Section 8.2.2 and Table 8.2.1).

– Still the Inner Lid seals can be tested without the need to remove the secondary lid by the secondary lid (SAR Section 7.4).

7November 12, 2008

HOLTECINTERNATIONAL

Revised Approach of Safety Function

• Leak-tight Containment – Both lids must be leak-tight (ANSI N14.5) (although there is no

basis for double containment boundary)– However, in the case that leakage occurs from Inner Closure Lid

(lid seals), the cask would need to be shipped to a repair facility for seal replacement; therefore, we need the relaxed water-tight acceptance criteria instead and a limited time period for shipment (4 months proposed).

• Moderator Exclusion – (10 CFR 71.55(e))– Both lids must be water-tight

• ALARA Oriented Operations and Maintenance– Outer Closure Lid seals require pre-shipment leakage test (SAR

Section 8.2.2 and Table 8.2.1).– Inner Closure Lid seals require pre-shipment leakage test (SAR

Section 8.2.2 and Table 8.2.1). The inner lid can still be tested without the need to remove the secondary lid by the secondary lid.

– Will clarify operations for testing Inner Closure Lid.

8November 12, 2008

HOLTECINTERNATIONAL

OTIs Impacted

• The following NRC OTIs on Chapters 7 (Operating Procedures) and Chapter 8 (Acceptance Criteria and Maintenance Program) are impacted by the revised approach.– OTI 7-5: Independent closure system– OTI 7-6: Acceptable Integrity of Inner Closure Lid– OTI 8-1: Adequate description of leakage rate tests– OTI 8-2: Independent closure system– OTI 8-3: Test Sensitivity of Pre-Shipment Leakage Tests– OTI 8-4: Pre-Shipment Testing Consistent with ANSI-N14.5

11/12/08 presentations by holtec international regarding ... · • structural otis discussed...

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