ML19158A517

Responses to NRC Second Request for Additional Information (Rais)

ML19158A517
Person / Time
Site:	07109375
Issue date:	06/07/2019
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards
Shared Package
ML19158A519	List: ML19158A515 ML19158A516 ML19158A517 ML19158A518 ML19158A529
References
2404013-NRC, EPID L-2019-LRM-0006
Download: ML19158A517 (43)

Text

Chapter 1 - General Information NRC RAI 1-1 Clarify the location of the elastomeric seals in the package.

Detail FG on Sheet 3 of Drawing 9786 indicates a general region where the elastomeric seals (BOM 7) are located in the flange (BOM 2). However, it is unclear where the seals are located relative to the flange itself.

The applicant's response to RAI 2-13, dated August 9, 2017, indicates that the elastomeric seals are located at 1.25 inches from the edge of the flange. Knowing the location of the seals with respect to the flange is important to demonstrate that containment requirements have been met, and that the package description is complete.

This dimension is critical, and should be depicted on the licensing drawings, since the applicant has recognized that the seal region experiences inelastic deformations, which may challenge sealing and containment of the package (see RAI 4-1 ).

This information is needed by the staff to determine compliance with 10 CFR 71.33.

Holtecs Response to RAI 1-1 Location of seals are indicated on Sheet 4 of licensing drawing 9786R5, which provides the details for the HI-STAR ATB 1T cask closure lid.

to Holtec Letter 2404013-NRC Page 1 of 43

Chapter 2 - Structural and Materials Evaluation NRC RAI 2-1 Clarify how the components in the containment boundary will not exceed ASME Section Ill NB values for normal conditions of transport (NCT).

RAI 2-14, dated August 9, 2017, requested the applicant to confirm that stress limits within the lid of the ATB 1T package do not exceed the values set forth by ASME for the 1-ft bottom end drop simulation for NCT conditions. However, the LS-DYNA simulations show that the inner base plate (and other components that are also part of the containment boundary) also undergo plastic deformation, as shown in the Figure below for the 1-ft NCT Bottom CG over corner drop.

Specifically, there is inelastic strain 3 inches away from the edge of the part on the surface.

Since inelastic deformations indicate that ASME stress levels are exceeded, the applicant shall (i) reconfirm that all containment boundary components do not exceed stress intensity values, according to ASME Section Ill NB, for all NCT drop and penetration simulations, and (ii) update tables and calculations in the application, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7).

to Holtec Letter 2404013-NRC Page 2 of 43

Holtecs Response to RAI 2-1 The NCT drop analyses are revised based on the improved cask design, and the results are shown to meet the Level A stress limits per ASME Section III Subsection NB. The allowable stress limits are in compliance with the Reg. Guide 7.6.

to Holtec Letter 2404013-NRC Page 3 of 43

NRC RAI 2-2 Explain and justify the parameters used to model concrete in LS-DYNA for the 1/4-scale prototype.

In response to RAI 2-9 dated August 9, 2017, the applicant stated that "the essential characteristics of the target, viz., the concrete thickness, its compressive strength, the top HY Armor 80 steel material and its thickness, are obtained from SNL", and that "the concrete material model used in the LS-DYNA ~-scale drop simulations is consistent with the one used for numerous other dry storage applications including HI-STORM FW, HI STORM 100.

Specifically, the concrete pad behavior is characterized using the same LS-DYNA material model (i.e., MAT_PSEUDO_TENSOR or MAT_016) as for the end drop and tipover analyses of the HI-STORM 100 storage cask and the tipover analysis of the HI-STORM FW storage overpack".

While the modeling approach has been used in other applications, Holtec has not demonstrated that this modeling approach is applicable to the site conditions found at Sandia National Laboratories. Specifically, the applicability of the parameters used in the LS-DYNA model of the concrete properties, as cited in Witte, M., et a/., "Evaluation of Low-Velocity Impacts Tests of Solid Steel Billet onto Concrete Pads, and Application to Generic ISFSI Storage Cask for Tipover and Side Drop", Lawrence Livermore National Laboratory, UCRL-/D-126295, Livermore, California, March 1997", to those found at the Sandia test site, has not been made.

Billet drop tests were performed on a concrete pad alone at LLNL, while the target at Sandia incorporates a steel plate on top of a concrete mass.

The applicant shall justify that the parameters used in the MAT_PSEUDO_ TENSOR model for the ATB 1 T package are representative of the concrete properties used at the Sandia site.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7),

71.73(c)(1), and 71.73(c)(3).

Holtecs Response to RAI 2-2 The parameters used for the target are considered reasonable given the LS-DYNA benchmark analysis showed excellent agreement between the physical tests and the computer simulation results. to Holtec Letter 2404013-NRC Page 4 of 43

NRC RAI 2-3 Clarify the material properties cited in Tables 2.2.1A and Table 2.2.1 B of the application.

Values reported in Tables 2.2.1A and Table 2.2.18 of the application for the yield strengths of SA-240 304 material appear to be inconsistent ((26.7 ksi and 30 ksi at 150°F, respectively) while the applicant claims to ensure that better than minimum material values can be expected from the material (Table 2.2.1 B ).

Confirm which values are correct and update the application, and any calculations, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.33(a)(5).

Holtecs Response to RAI 2-3 The material property tables in Section 2.2 have been updated consistent with the new package design. The material strength properties for SA-240 304 stainless steel now appear in Table 2.2.4, and the yield strength at 150°F is correctly listed as 26.7 ksi.

to Holtec Letter 2404013-NRC Page 5 of 43

NRC RAI 2-4 Clarify the material properties used for the trunnions on the drawings.

The licensing drawings do not indicate the material used to construct the trunnions, only that they must meet a minimum yield (106.3 ksi) and ultimate strength of 140 ksi (see flag note 5, sheet 1 of 5, on Drawing No. 9786). However, lifting results (Table 2.5.1) are based on a specific material (SA-182 FXM-19).

Clarify the safety factors in Table 2.5.1, as they are not based on the minimum material properties specified on the licensing drawings. Revise any related calculations using the material properties specified on the licensing drawings, as necessary, and update the application.

This information is needed by the staff to determine compliance with 10 CFR 71.45(a) and 10 CFR 71.33(a)(5).

Holtecs Response to RAI 2-4 Drawing No. 9786 is revised to clearly indicate the trunnion materials. The solid shaft is made from SB-637 N07718, and the hollow shaft is made from SA-182 FXM-19. The analysis accordingly uses the minimum yield and ultimate strength properties for these materials, as given in Tables 2.2.2 and 2.2.3.

to Holtec Letter 2404013-NRC Page 6 of 43

NRC RAI 2-5 Clarify the effective plastic strain reported for the top end puncture simulation.

Table 8.3 of the report, "Drop Analysis of the HI-STAR ATB 1T Transport Package" indicates that the maximum strain in the lid is 14.13%. However, from the files submitted, the maximum effective plastic strain is reported to be as high as 22.9%, as shown below on staff's plot using the applicant's model.

Verify this value, and others like this one in similar tables of this report, ensure all values in the application match the values in the models, and update the tables as necessary.

This information is needed by the staff to determine compliance with 1 0 CFR 71.73(c)(3).

Holtecs Response to RAI 2-5 All drop analyses have been re-performed based on the new package design. In addition, the strain-based acceptance criteria in Appendices EE and FF of the ASME Code Section III are no longer used to qualify the containment system under Hypothetical Accident Conditions (HAC).

Instead the Level D stress intensity limits per ASME Section III Subsection NB are used to qualify the containment boundary components under HAC. The latest results are presented in Section 2.7 of the SAR and the supporting calculation package (HI-2177539 Rev. 2). to Holtec Letter 2404013-NRC Page 7 of 43

NRC RAI 2-6 Clarify the effective plastic strain reported for the containment base plate and containment weld for the CG over corner followed by puncture simulation for hypothetical accident conditions (HAC).

The applicant indicates there is an effective plastic strain of 40% for the containment base plate (BOM 1) and of 35% for the adjoining containment weld. However, from the files submitted, the maximum effective plastic strain is reported to be as high as 67.8% for the containment base plate and 57.1% for the adjoining containment weld, respectively. Table 2.4 shows the allowables for the material which are exceeded in this case. Both of these effective plastic strain values exceed the values tabulated in Table 8.3 of the application.

Verify that these values are correct and revise the application, and any supporting calculations, as necessary. Note that all simulations should be re-examined and the application updated, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.73(a), 10 CFR 71.73(c)(1), and 10 CFR 71.73(c)(3).

Holtecs Response to RAI 2-6 to Holtec Letter 2404013-NRC Page 8 of 43

All drop analyses have been re-performed based on the new package design. In addition, the strain-based acceptance criteria in Appendices EE and FF of the ASME Code Section III are no longer used to qualify the containment system under Hypothetical Accident Conditions (HAC).

Instead the Level D stress intensity limits per ASME Section III Subsection NB are used to qualify the containment boundary components under HAC. The latest results are presented in Section 2.7 of the SAR and the supporting calculation package (HI-2177539 Rev. 2).

to Holtec Letter 2404013-NRC Page 9 of 43

NRC RAI 2-7 Clarify the location of effective peak plastic strains and related numerical singularities reported in the application.

Note (3) of Table 2.7.2 and Table 8.3 of the application and the drop analysis report, respectively, state that peak "effective strain accounting for triaxiality factor excludes the hot spots (points of numerical singularity)", as recommended by paragraph FF-1142 from ASME BPVC Section III - Appendices. Note 45 in paragraph FF-1142 states: "Not applicable to points of numerical singularity in the finite element model as justified in the final Design Report". This is related to containment components (baseplate in this case), and the applicant shall address numerical singularities using the strain based acceptance criteria.

Clarify:

(a) How the location of the "numerical singularity" is determined, as it can contain peak effective plastic strains above the allowable strain limit?

(b) What are the corresponding elements of the peak effective plastic strain being reported in the containment baseplate and the containment baseplate weld? It is unclear which elements are specifically being used for the peak effective plastic strains being reported and the ensuing through thickness effective plastic strains.

(c) Why the effective plastic strain for elements 720468 and 721135 (50.03% and 49.47%, respectively), in the containment baseplate, after completion of Simulation 9, are larger than the peak effective plastic strain of 40%? Justify how the argument of a "numerical singularity" can be made for element 720468, which has a peak effective plastic strain of 50.03% after accounting for triaxiality, as defined in Appendix B of the "Drop Analysis of the HI-STAR ATB 1T Transport Package" report.

This information is needed by the staff to determine compliance with 10 CFR 71.73(a),

10 CFR 71.73(c)(1), and 10 CFR 71.73(c)(3).

Holtecs Response to RAI 2-7 The drop calculation package is revised based on the new package design. The structural acceptance criteria for the package is switched to the conventional stress based criteria in compliance with Reg. Guide 7.6. The above comment becomes moot based on the complete reanalysis.

to Holtec Letter 2404013-NRC Page 10 of 43

NRC RAI 2-8 Verify that closure of the package is maintained during drop simulations by justifying the statement: "element erosion is not enough to cause any of the components to dislodge or shift position".

In response to RAI 2-6, dated August 9, 2017, the applicant stated that: "Per the updated drop simulations, the closure lid locking wedges (BOM 9 and 1 0) and the wedge blocks (BOM 11) experience very limited element erosion and only during the top down CGOC drop. The element erosion is not enough to cause any of the components to dislodge or shift position. Therefore, the use of standard (non-eroding) surface-to-surface contact elements is adequate for the closure lid locking wedges and wedge blocks, and it has no adverse effect on the results".

It is unclear how standard non-eroding surface-to-surface contact elements are justified when elements in these closure components are clearly eroding, as represented in the simulations for the closure lid locking wedges (BOM 9 and 10), and the cask wedge blocks.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7),

71.73(c)(1), and 71.73(c)(3).

Holtecs Response to RAI 2-8 The drop calculation package is revised based on the new package design. The contacts are revised, as appropriate, to support the new design and updated drop analyses. The conventional surface_to_surface and eroding_surface_to_surface are appropriately used in the revised analysis. It shall be noted that the closure lid locking wedges and the wedge blocks are not subject to erosion or failure in the revised analysis.

to Holtec Letter 2404013-NRC Page 11 of 43

NRC RAI 2-9 Clarify the values used to model identical materials in the LS-DYNA drop simulation files.

The licensing drawings state that BOM items 9-11, 29, 43, and 45 are made of Nitronic 50 (SB637-N07718). LS-DYNA simulations indicate that there are two different materials used to model these components, MID 2 and 3. These materials models are similar, but have different strain rate values and scale factors.

Staff is concerned that Holtec simulations may be producing erroneous results since the material models used are not consistent. Holtec has to provide material data supporting Nitronic 50 strain rates used in the simulations. Holtec has to clarify why these material values are different for the same material and update the LS-DYNA simulations and results, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7),

71.73(c)(1), and 71.73(c)(3).

Holtecs Response to RAI 2-9 The drop calculation package is revised based on the new package design. A single material model (MID 5 in LS-DYNA) is now used to characterize the material behavior for all cask components made from SB-637 N07718.

to Holtec Letter 2404013-NRC Page 12 of 43

NRC RAI 2-10 Clarify the stress limit values used to describe Nitronic 50 material, SB637-N07718, as reported in the application.

Table 2.1.4 of the application tabulates stress limits (such as 2 times Sm for bending) for SB-637 N07718 material as coming from ASME NB-3220. However, the values cited do not appear to come from this section of the code. Some of the values appear to come from Section II, Part D, Subpart 1, Table 4, via subparagraph NB-3232.1. Stress limits for this material should come from Part D Mandatory Appendix 2 for materials other than bolting (Tables 2A and 2B) to determine the appropriate Sm value.

It appears that the applicant is using the wrong stress limits (ASME limits) for this material, and as such, the reported safety factors/margin are most likely bigger (non-conservative, as a result).

The applicant needs to revise or explain these values with respect to safety margins, clarify and/or justify the stress limits in table 2.1.4 for this material, and revise the application, as well as the report HI-2177539, and any calculations that utilize this table, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.31(c).

Holtecs Response to RAI 2-10 The allowable stress intensity limits for SB-637 N07718 have been reviewed and updated, as appropriate, and they are now summarized in Tables 2.1.5 and 2.1.6 of the SAR for various service levels (Design, A, B, and D).

The stress limits for this material are derived based on Part D Mandatory Appendix 2 for materials other than bolting (Tables 2A and 2B) to determine the appropriate Sm value.

to Holtec Letter 2404013-NRC Page 13 of 43

NRC RAI 2-11 Confirm that the packaging coatings and consumable chemical products are nonflammable.

Section 2.2.7 of the application mentions that the cask closure system lubricants and hydraulic fluid are nonflammable. However, it does not specify whether the coatings, adhesives, and lubricants on secondary packaging are non-flammable nor does it provide their auto-ignition temperatures.

Therefore, staff cannot determine whether additional heat source terms should be taken into account in the thermal models.

This information is needed by the staff to determine compliance with 10 CFR 71.43(d).

Holtecs Response to RAI 2-11 All packaging coatings and consumable chemicals mentioned in subsection 2.2.4 (formerly section 2.2.7) are non-flammable. To clarify, Section 2.2.4 is updated with marking these coatings and consumable chemicals as nonflammable. The allowed amount is also clarified in the Notes section of subsection 2.2.4.

Below a short summary is provided for each chemical:

Adhesives Loctite 243: Loctite(R) 243 Threadlocker Medium Strength - Anaerobic Sealant. Only a trace amount (<5g per package) of this adhesive is used therefore this material would not impact thermal models. On the HMIS scale (The Hazardous Materials Identification System) this material is classified in category 1: Materials that must be preheated before ignition will occur.

Includes liquids, solids and semi solids having a flash point above 212 °F (100 °C) [1].

Grafex Crinkle Tape: Solid metallic seal with graphite coating. Temperature range 40 to 1832F

(-40 to 1000 °C) [2].

Lubricants Multifak AFB2: Lubricating lithium grease. Only a very small amount of this material is used in the package (< 40 grams) therefore it is not expected that this material would significantly affect thermal properties of the cask. Semi solid material with a flash point of > 392F (200 °C) [3].

Grafoil GTS / Loctite 8013: either Grafoil GTS or Loctite 8013 is found in ATB1T package. One of those two lubricants is used to lubricate the bolts that fasten the top cover to the tanks.

Relatively small amounts of material is used for these bolts (32 to 85 cm3 (i.e. < 3 oz ) per package). LOCTITE 8013 is a specially formulated metal-free anti-seize lubricant and is suitable for applications up to 2400F (1315°C) [4]. Grafoil GTS is a Graphite Thread Sealant paste made to Holtec Letter 2404013-NRC Page 14 of 43

from a combination of nuclear grade graphite and a nuclear quality petroleum based carrier.

Grafoil maintains its properties up to 1175F (635 °C) [5].

Coatings INERTA PRIMER 5a, Teknoplast HS 150A and Teknozinc 90SE A - Epoxy based coatings -

based on the information from the manufacturer and general description of epoxy paints the self-ignition point is typically above 662F (350 °C) [6].

Carboguard 890 - ATB-1T cask surfaces maybe coated or painted by Carboguard 890, a highly chemical resistant epoxy coating. Self-priming, tightly adherent and suitable for application over most existing coatings. Non flammable with temperature resistance up to 350F (177 C) [7] and a flash point above 752F (400 °C) [7]

References:

[1] MSDS sheet for Loctite 243. Document no: 53419711-ENG-1, 3/25/2004;

[2] Specification sheet for Grafex Crinkle tape. Tektrade Baltic, tektrade.ee;

[3] MSDS sheet for 00940 MULTIFAK AFB 2.

[4] Technical Data Sheet for Loctite 8013; January 2016;

[5] Technical data sheet for Grafoil GTS, TDS 21, Rev. 3.

[6] Technical information from the manufacturer (Mr. Tero Ojala) received by email on 8/23/2018.

[7] MSDS sheet for Carboguard 890, March 2019.

[8] Technical information from the manufacturer (Brian McHale, Carboline) received by email (2/21/2019) : Determination of the Autoignition Temperature for Carboguard 890 Paint Chips and Carbocoat 115/Carbocoat 140 Paint Chips, Report No.: FAI-2016-1411, 2016.

to Holtec Letter 2404013-NRC Page 15 of 43

NRC RAI 2-12 Clarify and/or provide additional material property data for SA-182, Grade FXM-19 (Nitronic

50) material and update any related LS-DYNA drop simulations as necessary.

Table 2.1.5, of the application, Stress Limits for Top Flange Material at Reference Temperature of 150oF (66oC) - Level A Service Condition and Table 2.2, Material Properties of Cask Top Flange do not provide all of the necessary material data needed for the use of Nitronic 50 with the strain based acceptance criteria (SBAC), as outlined in Non-Mandatory appendices EE and FF. Specifically, true stress strain curves, as a function of strain rate and temperature, true uniform strain limits, and true fracture strains should be provided.

True uniform strain limit and true fracture strain requirements can be found in ASME Section III, EE-1220 and EE-1221 of Non-Mandatory Appendix EE - Strain-based Acceptance Criteria Definitions and Background Information, and Non-Mandatory Appendix FF - Strain-based Acceptance Criteria for Energy-limited Events, as well as ASME Section II, Part D, Mandatory Appendix 5 - Guidelines on the Approval of New Materials under the ASME B&PV Code.

The requested material properties are essential to the performance of those components fabricated from Nitronic 50 for NCT and HAC drop test simulations in LS-DYNA. Update all Nitronic 50 material models used by LS-DYNA to simulate package drops for NCT and HAC, and revise any applicable calculations in the application, as necessary.

This information is needed by the staff to determine compliance with 10 CFR 71.31(c),

71.71(c)(7), 71.73(c)(1), and 71.73(c)(3).

Holtecs Response to RAI 2-12 The new/improved package design has a machined top flange which is integral to the cask containment walls, and it is made of SA-517 material. In the new design, the Nitronic 50 material is not used for the cask containment boundary. Furthermore, the package structural qualification is now based on conventional stress based criteria (i.e., ASME III NB).

to Holtec Letter 2404013-NRC Page 16 of 43

Chapter 3 - Thermal Evaluation NRC RAI 3-1 Specify the seals' maximum continuous allowable operating temperature and maximum short term allowable operating temperature (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) so that a review of the package containment seal can be performed.

(a) Table 2.2.2 does not provide the continuous and short term maximum allowable operating seal temperatures. The reported allowable seal temperatures should refer to objective measurements rather than referencing the thermal numerical analyses. It is noted that there should be sufficient margin between the seal's normal and accident condition operating temperatures and the allowable temperatures to account for uncertainties and assumptions in the analyses.

(b) Calculation package report Hl-2156585 states that the temperature during vacuum drying operation will be similar to that under NCT and will be bounded by the fire accident condition; this text implies that the seal during vacuum drying could have excessive temperatures. The application should clarify that the seal during vacuum drying will not exceed the continuous allowable operating temperature.

This information is needed by the staff to determine compliance with 10 CFR 71.51 (a).

Holtecs Response to RAI 3-1 (a) Table 2.2.2 is revised as shown below to indicate manufacturers recommended continuous-use operating temperatures for the inner and outer seal materials. These temperatures bound the temperature requirements of Table 3.1.1 with significant margin. Additional testing has been performed to support the maximum short-term operating temperature (post-fire, per Table 3.1.2). Further discussion and justification is provided in Chapter 3.

Note: Table 2.2.2 is revised to Table 2.2.6 in revision 2 of the SAR.

Table2.2.6:CriticalCharacteristicsforCaskContainmentSeals(Sheet1of2)

Seal Characteristics Seal Location INNER (ITS)

OUTER (NITS)

Material FFKM fluorocarbon (See Note 1)

EPDM (See Note 2)

O-ring type (See Note 3)

Hollow Hollow O-ring outer diameter (inch) 0.312 +/-0.012 0.250 +/- 0.007 to Holtec Letter 2404013-NRC Page 17 of 43

O-ring inner diameter (inch) 0.192 +/- 0.008 0.125 +/- 0.005 Shore-A Durometer Value (ASTM D2240) 80 +/- 5 75 +/- 5 Maximum expected compression set at normal transport conditions (ASTM D395 Method B)

See Note 4 Minimum Useful Springback mm (in.)

1.8 (0.07 in.)

(See Note 5)

Not applicable (See Note 6)

Maximum Load on seals required to compress seals and achieve metal-to-metal contact at lid/flange interface, combined inner and outer seals (See Note 7) 60 lbf/inch Minimum continuous operating temperature (ASTM D1329)

-40°C (-40°F)

Maximum continuous operating temperature 275°C (527°F)

(See Note 8) 121°C (250°F)

(See Note 9)

Maximum short term operating temperature, 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 300°C (608°F)

(See Note 10)

Not applicable Minimum Tensile Strength (ASTM D1414 or ASTM D412) 1350 psi 1350 psi Compatible with radiation environment (107 rad)

Fair (See Note 11)

Fair (See Note 11)

Compatible with Boric Acid and water (i.e., no degradation in Borated water environment)

Yes Yes NOTES Note1:Parkerfluorocarbon(FFKM)compoundFF40080hasbeenidentifiedasanoringcompoundthatmeets thecriticalsealcharacteristicsspecifiedinthistable.Testingofmaterialcompositionandcriticalmaterial characteristicswillbeperformedtoverifyvendordata.Inspectionandverificationofsuppliedmaterial compositionanddimensionalrequirementswillbeperformedoneachoring.

Note2:Parkerethylenepropylene(EPDM)E074075hasbeenidentifiedasanoringcompoundthatmeetsthe criticalsealcharacteristicsforthisNITScomponent.

Note3:RefertolicensingdrawingsperSection1.3forsealgroovedesigndetails.Thesealgroovedesignand tolerancesareengineeredtoprovidetherequiredusefulsealspringbackwhenusedwithasealthat meetsthecriticaloringdesignparametersdescribedinthisTable.

Note4:Compressionsetforinnerandoutersealsisconsideredinsignificantforlongtermoperationatthe relativelylownormaltransporttemperaturesspecifiedinTable3.1.1.Compressionsetatshorttermfire accidentconditionsofTable3.1.2doesnotaffectthesealingcapabilityoftheoring.

Note5:Minimumusefulspringbackforinner(ITS)sealisbasedonprovidingsealagainstaminimumof25psig internalorexternalpressure,overfullrangeofnormaltransportandaccidentconditions.

Note6:Usefulspringbackforouter(NITS)sealisnotapplicableforprovidingcontainment.Outersealprovides redundantcontainmentbarrierduringnormalconditionsoftransportonly.

Note7:Sealmaterialstobetestedtoconfirmthattheloadrequiredtocompressthesealstoachievemetalto metalcontactatthesealinterfaceislessthanthevaluegiveninthetable.Thetablevalueisbasedona minimumcasklidweightof22,500poundsandaverageoringlengthof375inchessuchthattheself to Holtec Letter 2404013-NRC Page 18 of 43

weightofthelidissufficienttofullycompresstheseal.Theloadvaluegiveninthetableistobe distributedbetweenbothseals.

Note8: Maximumcontinuousoperationtemperaturebasedonmanufacturersrecommendedtemperaturerange forParkerfluorocarbon(FFKM)compoundFF40080material.Thistemperatureboundsthemaximum temperaturefornormaltransportinTable3.1.1.

Note9: Maximumcontinuousoperationtemperaturebasedonmanufacturersrecommendedtemperaturerange forParkerethylenepropylene(EPDM)E074075material.Thistemperatureboundsthemaximum temperaturefornormaltransportinTable3.1.1.

Note10:MaximumshorttermoperationtemperatureanddurationbasedonmanufacturerstestingofParker fluorocarbon(FFKM)compoundFF40080materialinthespecifiedhollowcrosssectioninaccordance withASTMD1414.Thisboundsthemaximumpostfireinnersealtemperature,forthespecified duration,inTable3.1.2 Note11:Basedonpublishedvendorliterature,thesematerialsareconsideredacceptableforstaticsealingina radiationenvironmentinexcessofthemaximumexpectedexposureinthistransportcask,forthe maximumpermissibleseallifedefinedinTable8.2.1.

(b) As explained in Section 6.4 of HI-2156585 Revision 2, the cask closure lid is not installed during vacuum drying. The cask loading operation steps are provided in Chapter 7 of the SAR. In Section 7.1.2, a radiation shielded drying cover is placed on the cask and the vacuum drying system is connected to the drying cover to perform vacuum drying operation.

In Section 7.1.3 of the SAR, the cask lid is installed for cask closure. Therefore, the cask lid is installed after vacuum drying. There is no concern on seal temperatures during vacuum drying.

to Holtec Letter 2404013-NRC Page 19 of 43

NRC RAI 3-2 Provide the HAC thermal model results that consider the effect of a puncture test at the seal location, a non-uniform decay heat positioned at the seal, and the change in the package closure lid locker so that a bounding condition at the seals can be analyzed.

Based on the response to RAI 4-2 dated August 9, 2017, it appears that the seal temperatures are near, or very close to, their allowable values. However, the current thermal model did not address conditions that could affect seal temperatures:

(a) The application shows that plastic deformation exists at the seal and closure region after the 1 foot NCT drop and 30 feet HAC drop. Additional plastic deformation is expected in the seal region as a result of the HAC puncture test, where the puncture pin strikes the lid of the package, as suggested by the 1 Meter top puncture simulation that assumed the puncture pin was located towards the center of the lid. Staff believes the testing was not conducted in accordance with 71. 73(c)(1) since higher local deformations at HAC could result if the puncture pin had been positioned to strike the package directly over a seal region that already has been plastically deformed, rather than the center of the lid.

(b) Recognizing that the BFA-Tank Cassette is modeled with simplifying assumptions as part of the structural hypothetical accident drop and puncture tests, the thermal input due to the potential for local placement of the source's decay heat at the seal (due to potential failure of the Cassette) was not included. Rather, the package cavity is "... simplified to be a solid volume with uniform heat generation" and internal component temperatures during the thermal accident condition are increased by 160° C from normal conditions. In addition, the calculation for using 160° C was not provided nor was it justified as being bounding for determining the seal temperature.

(c) The revised calculation package Hl-2156585 (Section 6.5) indicates that the change in the closure lid locker was not modeled even though it could have an impact on the seal temperature.

This information is needed by the staff to determine compliance with 10 CFR 71.51 (a), and 71.73.

Holtecs Response to RAI 3-2 (a) Thermal evaluations have been performed to include the damage to cask subsequent to drop and puncture accidents. The evaluations have been performed with the latest cask design presented in Revision 2 of the SAR.

(b) According to part (iii) in Section 2.1.2.2 of the SAR, the BFA-Tank provides secondary packaging to the non-fuel waste. The BFA-Tank walls including the top and bottom plates must not be subject to gross failure under the postulated normal and hypothetical accidental drop conditions. It implies that the walls including the top and bottom plates must not be to Holtec Letter 2404013-NRC Page 20 of 43

subjected to buckling (gross yielding) under the inertial loads from drop accidents. Therefore, only waste in particle sizes may be leaked from the damaged weld of the BFA-Tank after the drop accident. The influence of the waste particles attached on the cask cavity surface is expected to be insignificant since the decay heat of the particles is small.

It is noted that the entire cask cavity surface is in contact with heat source in the fire simulation. In the fire simulation, the cask cavity is simplified to be solid volume with uniform heat generation and effective thermal conductivity. The effective thermal conductivity of the cavity solid volume is 0.21W/m-K. The uniform volumetric heat generation rate is 169W/m3, which is applied throughout the cask cavity. Thus, the cask cavity surface is in contact with heat source in consideration of the potential waste particles attached on the cask cavity surface.

In addition, it is observed that the total heat absorbed by the cask is more than 100 times the decay heat released from the waste when the seal temperature reaches its maximum.

Therefore, the decay heat of the waste has negligible impact on the temperature increase of the cask under the fire accident.

As explained in Section 3.4.3.2 of the SAR, the cask cavity is modeled as a solid volume with effective thermal properties due to the uncertainty of the BFA-Tank position and the waste position after the drop accident. During fire and post-fire cooldown, the increase in the average temperature of the cask cavity is expected to be smaller than the increase in the average temperature of the cask containment boundary components since the heat from the fire is transferred from outside to inside. The increase in the volumetric average temperature of the cask containment wall and baseplate is 159oC, i.e. from 57oC to 216oC as shown in Table 3.1.2 of the SAR. Similarly, the increase in the volumetric average temperature of the closure lid is 119oC, i.e. from 62oC to 181oC as shown in Table 3.1.2 of the SAR.

It is noted that the cask components including the cask closure lid seals are explicitly modeled in the fire simulation. As shown in Table 3.1.2 of the SAR, the maximum temperature of the cask closure lid inner seal during post-fire is 278oC, which is 217oC higher than its temperature under normal transport condition.

(c) Thermal evaluations have been revised with the latest cask design presented in Revision 2 of the SAR.

to Holtec Letter 2404013-NRC Page 21 of 43

NRC RAI 3-3 Clarify the boundary conditions used for the thermal model during the hypothetical accident conditions 30 minute fire.

According to the FLUENT model, a mixed thermal boundary condition was applied to the package's external surface. This mixed thermal boundary condition included the convection heat transfer due to the fire, radiative heat transfer input due to the fire with an emissivity of 0.9, and a fire temperature of 1475° F, and heat transfer from the package surface with an emissivity of 0.9 at the package surface temperature.

However, the response to RAI 3-5 stated that a unit absorptivity was adopted. Therefore, the two stated boundary conditions are inconsistent, and it is not certain if the bounding scenario was modeled.

This information is needed by the staff to determine compliance with 10 CFR 71.51 (a), and 71.73(c)(4).

Holtecs Response to RAI 3-3 According to ANSYS FLUENT Users Guide, the external heat radiation is calculated as (Eq331) where istheemissivityoftheexternalwallsurface,whichistheinputofexternalemissivityin

FLUENT, isStefanBoltzmannconstant, isthesurfacetemperatureofthewall, isthetemperatureoftheradiationsourceorsinkontheexteriorofthedomain,whichisthe inputofexternalradiationtemperatureinFLUENT.

Thermal evaluations of hypothetical accident condition (HAC) in revision 2 of the SAR have been performed assuming a fire emissivity of 0.9 as prescribed in 10CFRPart71 regulations. For the cask absorptivity during fire, 10CFR71 provides the following guidance:

For purposes of calculation, the surface absorptivity coefficient must be either that value which the package may be expected to possess if exposed to the fire specified or 0.8, whichever is greater; Since the exposed surfaces of the cask are made of stainless steel with an absorptivity lower than that of 0.8, an absorptvitiy of 0.8 is adopted as prescribed in 10CFRPart71 regulations. Based on the above, the boundary condition adopted in the FLUENT thermal model during 30-minute fire accident is 0.9*0.8 = 0.72 in rev 2 of the SAR.

to Holtec Letter 2404013-NRC Page 22 of 43

Chapter 4 - Containment Evaluation NRC RAI 4-1 Provide evidence that demonstrates the package will meet regulatory release during normal conditions and hypothetical accident conditions.

The responses to RAI 2-13 and RAI 4-1 indicate that plastic deformation occurs at the seal and closure region during normal and hypothetical accident conditions. Plastic deformation at the seal and closure region after the 30 ft drop is further shown in the LS-DYNA plot below (seal region of the top flange). However, there was no demonstration that a resulting leakage rate from the package would ensure there would be no loss or dispersal of radioactive contents limited to that described in 71.51(a).

It is also noted that the seals spring back would not necessarily be sufficient to ensure containment.

This information is needed by the staff to determine compliance with 10 CFR 71.51(a).

to Holtec Letter 2404013-NRC Page 23 of 43

Holtecs Response to RAI 4-1 The improved cask design considers crushable attachments (energy absorbers), high strength material for the containment boundary and the structural qualification uses a more robust stress based design criteria.

With the above improvements, the structural evaluation demonstrates that the primary stresses in the sealing grooves and the seal seating surfaces on the closure lid and the top machined flange are within the material elastic limit. This, in addition to the acceptable seal relaxation, ensures that the containment of the package is well maintained with high level of confidence.

to Holtec Letter 2404013-NRC Page 24 of 43

NRC RAI 4-2 Provide additional discussion on the seal short term temperature tests so that a review of the results can be performed.

As provided in the response to RAI 4-2, the Parker report titled "Effects of Short-term Temperature Spike on FF400 Compression Set" briefly described results of FF400 0- rings at 300° C and 320° C. According to Table 1, the Test 1 sample was heated to 200°C for 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> and resulted in a 22% compression set. Likewise, Table 1 appears to indicate that the Test 2 sample was heated to 300° C for 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> (resulting in a 24% compression set) and the Test 3 sample was heated to 320° C for 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> (resulting in a 34% compression set).

However, the "Methods" portion of the report appears to indicate that the 300° C and 320° C test period lasted only one hour (not 70 hours8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br />). Likewise, the report was not clear in specifying the exposure period for Test 4 sample and Test 5 sample, which resulted in compression sets of 7%

and 9%, respectively.

a) How long were the 0-rings exposed to the 300° C and 320° C for Test 2, Test 3, Test 4, and Test 5?

b) What is the difference between the Test 2 and Test 4 samples (both at 300° C) and the Test 3 and Test 5 samples (both at 320° C)?

c) Why do Test 4 and Test 5 sample results have much lower compression sets compared to the Test 2 and Test 3 sample results and which compression set values are considered acceptable?

This information is needed by the staff to determine compliance with 10 CFR 71.51 (a), and 71.73 Response to RAI 4-2 To provide more application-specific data on the compression set of the FF400 material, additional testing has been performed. The results of this testing, summarized below, are more specifically indicative of seal performance and are therefore referenced in the design evaluation rather than the "Effects of Short-term Temperature Spike on FF400 Compression Set" report that has been initially provided.

Test Summary:

• Testing was performed on FF400 material extruded in the hollow o-ring configuration used in the ATB 1T design, with a representative o-ring groove. to Holtec Letter 2404013-NRC Page 25 of 43

• Testing was performed at a temperature of 300°C for a maximum of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, which bounds (with margin) the maximum expected temperature and duration of the seal following the postulated fire accident.

• Resulting mean compression set of 43% at 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is considered acceptable to maintain a positive seal interference.

• Resulting mean compression set of 13% at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> bounds the expected temperature and duration of the post-fire accident condition.

to Holtec Letter 2404013-NRC Page 26 of 43

Parker Parker Hannifin Corporation 0-Ring Division 2360 Palumbo Drive lexington, KY 40509 Office 859 269 2351 Fax 859 268 5128 RESEARCH & DEVELOPMENT REPORT PREPARED BY:

TITLE FF400-80 EVALUATION AT 300°C EXCURSION Aaron Howard R&D Manager DATE March 12, 2019 Unless otherwise noted, these da1a and other information (collectively "lnformationj contained herein are based on typical values from a limited number of tests conducted using the cited test methods. The Information is provided solely for users having technical expertise and should not be used for establishing specification limits. Before you select or use any material, component, or system, It is important that you analyze aH aspects of your application. The user, through its own analysis and testing, is solely responsible for making the final selection of the system and components and assuring that all performance, endurance, maintenance, safety and warning requirements of the application are mel The user must analyze all aspects of the application, follow applicable industry standards, and follow the information concerning the product in the current product catalog and in any other materials provided from Parker or its subsidiaries or authorized distributors. Final acceptance and approval of the material, component or system must be made by the user after testing its performance and endurance in the entire application under all conditions which might be encountered. Although the Information is believed to be reliable, Parker makes no warranty or representation whatsoever, either express or implied, including, but not limited to merchantability or fitness for a particular purpose, concerning the information. Improper use of the information can cause death, personal injury and property damage. You are solely responsible for making proper use of the infonnation. In no event shall Parker be liable for any damages of any kind whatsoever, including any special, indirect, or consequential damages, relating to the use of this site or the information, or the inability to use the information. The user agrees to defend, indemnify and hold hannless Parker, its parents, affiliates, licensees and their respective directors, officers, employees and agents from and against all losses, liabilities, claims, damages, and expenses, including attorneys' fees, arising out of your use the Information, or your violation or alleged violation of the terms of this notice. The provision of the Information should not be taken as an inducement to infringe any patent or to violate any law, safety code, or other regulation. The recording of false, fictitious, or fraudulent statements or entries on this certificate may be punishable as a relony under federal law.

This document contains information that is confidential and proprietary to the 0-Ring division of Parker Hannifin. This document is furnished on the understanding that the document and the information It contains will not be copied or disclosed to others or used for any purpose other than conducting business with Parker. That it will be returned and all further use discontinued upon request by Parker, copyright Parker, year of copyright is first year indicated on this document AI rights reserved.

Recommendations on application design and material selection are based on available technical data and are offered as suggestions only. Each user should make his own tests to detennine the suitability for his own particular use. Parker offers no express or implied warranties concerning the form, fit, or function of a product in any application.

UNLESS OTHERWISE NOTED, THESE ARE TEST VALUES FROM A LIMITED NUMBER OF TEST SAMPLES AND SHOULD NOT BE USED FOR ESTABLISHING SPECIFICATION LIMITS.

Page 1 of 5 to Holtec Letter 2404013-NRC Page 27 of 43

Parker TITLE:

OBJECTIVE:

METHODS:

RESULTS:

Research & Development Laboratory Report FF400-80 Evaluation at 300°C Excursion March 12, 2019 FF400-80 Evaluation at 300°C Excursion To evaluate the effect on FF400-80 hollow o-ring segments at 300°C excursion temperatures.

The test performed will be a modified version of the compression set testing prescribed in ASTM 01414 (which references ASTM 0395 for further details of the test method). The modification to 01414 will be the use of a machined gland to control deflection of the seal (rather than spacers) to more accurately mimic the final application. 3 samples will be tested at each time with the median compression set value reported. Time and temperature combinations to be tested are:

2hrs@ 300°C 4hrs@ 300°C 8hrs@ 300°C After the time and temperature exposures above, the specimens will immediately be removed from the test fixture, allowed to cool for a minimum of 30 minutes on a non-conductive surface, then the final measurement of compressed height as per ASTM 0395 Method B will be recorded.

The samples to be tested will be hollow tubing manufactured from Parker compound FF400-80. The design ID of the tubing will be 0.192 +/- 0.008 and the OD of the tubing will be 0.312 +/-

0.012.

Modified test fixtures with production intent gland dimensions to be supplied by the customer.

Testing on each sample was performed as prescribed above.

The depth of the gland in the fixture was measured at 0.233 inches, and the cross section of each sample ranged from 0.310 to 0.313 inches. Overall this gave a compression of -25% for each sample at room temperature. During the test, it was noted that one sample on the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> test was partially split along the ID of the tube. The split is visible in the pictures detailing the test below.

This document ccntains inbmation that is confidential and proprietary to the D-Ring division of Pari<er Hannifin. Tlis document is furnished on the underslanding that the document and the information it ccntains win not be copied or disclosed to others or used for any purpose other than conducting business with Pafker. That it woll be returned and all futlher use discontinued upon request by Parker, oopyright Parker, year of oopyright is first year indicated on ttis document All rights reserved.

Recommendations on application design and material selection are based on available technical data and are offered as suggestions only. Each user should make his own tests to determine the suitability for his own partkUar use. Pari<er offers no expess <<implied wananties oonceming the fam. fit <<function of a product in any application.

UNLESS OTHERWISE NOTED, THESE ARE TEST VALUES FROM A UMITED NUMBER OF TEST SAMPLES AND SHOULD NOT BE USED FOR ESTABLISHING SPECIFICATION UMITS.

Page2of5 to Holtec Letter 2404013-NRC Page 28 of 43

Parker Research & Development Laboratory Report FF400-80 Evaluation at 300°C Excursion March 12, 2019 This document contains information that is confidential and proprietary to the 0-Ring division of Parker Hannifin. This document is fumished on the understanding that the document and the information it contains will not be copied or cisclosed to olhers or used for any purpose other than conducting business with Parker. That it will be retumed and all further use discontinued upon request by Parker, copyright Parker, year of copyright is first year indicated on this document All rights reserved.

Raccmmendations on application design and material selection are based on available technical data and are offered as suggestions only. Each user shot.Cd make his own tests to detemine the suitability for his own partirular use. Parker offers no expRISS or implied warranties concernng the form, fit, or function of a product in any appfK:ation.

UNLESS OTHERWISE NOTED, THESE ARE TEST VALUES FROM A LIMITED NUMBER OF TEST SAIIAPLES AND SHOULD NOT BE USED FOR ESTABLISHING SPECIFICATION LIMITS.

Page 3of5 to Holtec Letter 2404013-NRC Page 29 of 43

Parker Research & Development Laboratory Report FF400-80 Evaluation at 300°C Excursion March 12, 2019 ure 3: 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after test One sample after the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> exposure exhibited a minor axial crack radiating from the ID to the OD during the test. The crack appears to have propagated less than half way through the thickness of the wall, and approximately two thirds the length of the sample. This sample did not show higher compression set than the other samples. No other cracks are visible the samples.

This document contains information that is confidential and proprietary to the 0-Ring dillision of Parker Hannifin. This document is furnished on the understanding that the document and the information it contains will not be copied or dsdosed to others or used for any purpose olher than condudlng business wilh Parker. That it will be returned and all further use d"ISCOntinued upon request by Parker. copyright Parker, year of copyright is first ~r indicated on lhis document. All rights reserved.

Recommendations on application design and material selection are based on available technical data and are offered as suggestions only. Each user should make his own tests to determine the suitabir.ty for his own partirular use. Parker offers no e>cpi'8SS or implied warranties concerning the form, fit, or function of a product in any application.

UNLESS OTHERWISE NOTED. lliESE ARE TEST VALUES FROM A ~IMITED NUMBER OF TEST SAMPLES AND SHOULD NOT BE USED FOR ESTABLISHING SPECIFJGATJON LIMITS.

Page4 of5 to Holtec Letter 2404013-NRC Page 30 of 43

Parker Research & Development Laboratory Report FF400-80 Evaluation at 300°C Excursion March 12, 2019 At completion of each test, the samples were removed from the fixture and allowed to cool to room temperature as prescribed in ASTM 0395. After a minimum of 30 minutes, the height was measured and the pennanent set was calculated.

Table 1: Compression set results 2 Hours @ 300°C ) 4 Hours @ 300°C ) 8 Hours @ 300°C

%Set Sample 1 13%

21%

40%

%Set Sample 2 13%

25%

43%

%Set Sample 3 13%

23%

43%

% Set Median 13%

23%

43%

CONCLUSIONS:

After exposure at 300°C for durations up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, the measured compression set of the FF400-80 samples were within accepted design guidelines and maintained a positive interference with the gland. This is a good indicator that there will be continued sealing function provided by the seals after these exposure times at this extreme temperature spike.

One sample did crack during the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> test. FFKM seals are more susceptible to cracking during elevated temperature testing due to high cross link density and this situation is exacerbated by high compression of the seal due to thennal expansion. This can typically be eliminated by reducing the compression in the design.

However, in this application that would likely be counterproductive as that would also reduce the size of the gap between mating components that can be effectively sealed and the temperature at which this cracking occurred is an extreme situation with low probability of occurrence. Furthennore, because the crack radiated from the seaiiD and did not propagate to the outer surface, the sealing surface, it is very unlikely seal perfonnance would be compromised.

This document contains information that is confidential and proprietary to the 0-Ring division of Parker Hannifin. This document is furnished on the understanding that the document and the information it contains will not be copied or cisclosed to others or used for any purpose other than conducting business with Parker. That it will be returned and all further use discontinued upon request by Parker, copyright Parker, year of copyright is first year indicated on this document. All righls reserved.

Recommendations on application design and material selection are based on available technical data and are offered as suggestions only. Each user should make his own tests to determine the suitability for his own partia.olar use. Parker offers no express or implied warranties concerning the form, fit, or function of a product in any application.

UNLESS OTHERWISE NOTED, THESE ARE TEST VALUES FROM A LIMITED NUMBER OF TEST SAMPLES AND SHOULD NOT BE USED FOR ESTABLISHING SPECIFICATION LIMITS.

Page 5 of5 to Holtec Letter 2404013-NRC Page 31 of 43

Chapter 5 - Shielding Evaluation NRC RAI 5-1 Justify that the package containing fixed surface contamination or CRUD meet the regulatory dose rate limits.

RAI 5-1, dated August 9, 2017 requested that the applicant provide additional information on the allowable contents other than the activated stainless steel or lnconel that are not represented by the analysis within the application. The applicant stated, in its response "the ceramic mesh screens are not directly activated by the neutron flux in the core. The ceramic mesh screens may have surface contamination present (from contaminated spent fuel pool water), but this is no different from the surface contamination that may be present on other waste content." This describes the ceramic mesh screens specifically, but does not provide a limit for other materials.

The applicant also added a specific limit for "maximum permissible Co-60 activity of nonfixed surface contamination" to Table 7.1.2 of the application. This information however is insufficient to define the contents. For example, CRUD and the ceramic mesh screens from contaminated spent fuel pool water may contain transuranic materials.

The response to the RAI does not address the staff's concern and the content specification is still not clearly and concisely defined. The staff requests that the applicant provide the additional follow-up information:

a) A clarification within the allowable contents description (Section 1.2.2 of the application) that all radioactive contents are activated stainless steel or lnconel and that any other allowable radioactive contents that are not made from stainless steel or lnconel are only contain CRUD and surface contamination. If this is not the case the staff requests that applicant clarify any contents that are not neutron activated stainless steel or lnconel and provide an analysis demonstrating that these contents meet regulatory external dose rates or are bounded by the activated stainless steel lnconel analyses within Chapter 5 of the application.

b) A discussion on how the specific activity is evaluated for the fixed surface contamination and CRUD. The applicant needs to demonstrate that stainless steel and lnconel bound the self-shielding properties, per mass, of any other contaminated components not made of stainless steel or lnconel (such as mesh filter screens).

c) A shielding analyses to explicitly model components with CRUD and/or surface contamination to demonstrate that the package meets the regulatory dose rate limits. Since fixed surface contamination and CRUD are, by definition, on the surface, the staff finds that the analysis discussed within Chapter 5 of the SAR is not representative as the applicant models a uniformly activated component. This is non-conservative as the analysis assumes that there is activity at the center of a self-shielded component when in reality the activity is toward the surface.

to Holtec Letter 2404013-NRC Page 32 of 43

d) A limit for neutron emitting source material. Section 5.2 of the application states: "Neutron radiation - this source is negligible for activated steel components, and is therefore not considered in the dose analyses." Although the primary contribution to external dose from CRUD and surface contamination is from Co-60, transuranic neutron emitting materials are present. The staff requests that the applicant establish a minimum value for neutron emitting material and demonstrate that this amount would be sufficiently low as to not contribute to external dose.

Section 5.5.2, "Radiation Shielding" of NUREG-1609, states: "Confirm that the contents used in the shielding analysis are consistent with those specified in the General Information section of the application. If the package is designed for multiple types of contents, ensure that the contents producing the highest external dose rate at each location are clearly identified and evaluated."

This information is needed by the staff to determine compliance with 10 CFR 71.47(b)(1),

71.47(b)(2), 71.47(b)(3), and 71.51(a)(2).

Holtecs Response to RAI 5-1 a) The following text has been added to Section 1.2.2, Radioactive contents are activated stainless steel or Inconel. Any contents not made from stainless steel or inconel (like ceramic mesh screens) do not contain induced activity, i.e. have not been subject to a neutron flux from the reactor core, and only contain CRUD and surface contamination.

b) The specific activity of the CRUD and fixed surface activity has been (or is required to be) calculated by the user as stipulated in Note 2 below SAR Table 7.1.2. The shielding configuration where all waste content is assumed to be the maximum allowed specific activity stainless-steel bounds any configuration where some ceramic mesh screens are present since the ceramic mesh is not activated by the reactor core (i.e. there is no induced activity in the ceramic mesh screens) and the ceramic mesh screens have the same surface contamination as the other waste components. We have looked at our clients waste information and it appears that 99% of the total activity of reactor internals, including the highest specific activity waste items designated for the BFA-200 Tank, takes the form of induced activity, with CRUD and fixed surface activity contributing less than 1%. We do not fully understand exactly what the RAI is requesting with a demonstration of bounding self-shielding properties, but we have provided a bounding shielding analysis that provides the maximum dose rates of the allowable content as required by NUREG-1617. Also, see Response to 5-1(c) below.

c) The specific activity of the CRUD and fixed surface activity has been (or is required to be) calculated by the user as stipulated in Note 2 below SAR Table 7.1.2. The maximum specific activity, which may be located on the outermost portion of waste items is assumed for the full volume of the waste content which is a conservative assumption that yields to Holtec Letter 2404013-NRC Page 33 of 43

bounding dose rates. If the analysis took an average specific activity value of the waste and homogenized the waste source region then this would be non-conservative; but the analysis took the maximum allowed specific activity (not the average specific activity) so the dose rate results provided in Chapter 5 remain conservative and bounding. For example, if there is an inner region and an outer region for a particular waste component, it may be possible to model two source regions, one outer region with the maximum specific activity, and an inner region with reduced specific activity. Since BFA tanks are loaded with numerous waste items with varying geometries, the modeling is conservatively simplified by homogenizing the waste content with the maximum allowed specific activity for the entire volume of the waste content to yield bounding dose rates. The following text has been added to Paragraph 5.3.1.2, NUREG-1617 states a common practice in shielding analyses is to homogenize the source region rather than develop a detailed heterogenous model Similarly, NUREG-1536 also discusses how homogenization is a common practice to facilitate shielding calculations. The HI STAR ATB 1T shielding models homogenize induced activity, CRUD, and fixed surface contamination in the source region. The shielding analyses presented in this chapter use a bounding homogenous source region for each of the waste package types (Waste Package A, B, C, D, and E).

While not all components are activated uniformly, the most activated portion of any single waste item is required to be below the specific activities listed in Table 7.1.2, ensuring that bounding dose rates are calculated and presented in this chapter.

Also, see Response to 5-1(b) above.

d) Section 1.2.2 lists the allowable contents which can be summarized as GTCC (non-fuel) waste. There are not any provisions in the allowed contents for radioactive neutron sources beyond the negligible amount that may be present from surface contamination. To prevent worrisome neutron sources, like Californium, or Americium-Beryllium, or Polonium-Beryllium neutron sources, from being loaded into the HI-STAR ATB 1T, Table 7.1.2 has an added row listing the maximum allowable neutron source per unit mass (20 n/s/kg). Section 5.2 has been updated to consider a maximum allowable neutron source.

The second part of the NRC request asked for demonstration that this maximum allowed neutron source would be sufficiently low as to not contribute to external dose. Dose rates are calculated for the maximum allowed neutron source with results presented in Table 5.4.5 demonstrating that the dose rates from content with the maximum allowed neutron content to be sufficiently low as to not contribute significantly to external dose rates.

to Holtec Letter 2404013-NRC Page 34 of 43

NRC RAI 5-2 Provide more specific instructions in footnote 4 on Table 7.1.2 of the application for the user to determine the most activated portion of any single waste item.

In RAI 5-4, the staff requested information justifying the uniform distribution of the source. In its response the applicant added a condition to Table 7.1.2 of the application that states: "The limits for maximum specific activity of contents for each Waste Package Type in Table 7.1.2 have to be met by the most activated portion of any single waste item." Because this this statement could be misinterpreted by a user, the applicant needs to revise the footnote to provide more specific instructions that show the user how to determine the "most activated portion of any single waste item."

Section 5.5.3.2, "Material Properties," of NUREG-1609 states: "If the shielding model considers a homogenous source region (rather than a detailed heterogeneous model of the contents),

ensure that such an approach is justified."

This information is needed by the staff to determine compliance with 10 CFR 71.47(b)(1),

71.47(b)(2), 71.47(b)(3), and 71.51(a)(2).

Holtecs Response to RAI 5-2 The sentence making up footnote 4 has been moved to the last sentence of footnote 2. An additional sentence is added to footnote 2 indicating, Pre-calculated specific activity values for any single waste item shall ensure that the most activated portion of any single waste item is less than the corresponding specific activity limit in Table 7.1.2. Table 7.1.2 takes the form of requirements rather than instructions.

to Holtec Letter 2404013-NRC Page 35 of 43

NRC RAI 5-3 Evaluate HAC dose rates using a bounding model of the bottom BTC (BFA-Tank Cassette) plate or restrict contents so that the source cannot relocate outside the BTC plates.

For the HAC model, the applicant assumed that the 30ft drop of the package would cause the bottom plate to relocate. The applicant assumed that the plate would rotate 45 degrees and expose a section of the contents approximately 300 mm wide. The applicant modeled this by ignoring the rotation and creating a 300 mm missing section of the bottom plate with it fixed in its original location at the bottom of the package. The applicant assumed that the missing volume is filled with contents at the maximum specific activity. In RAI 5-5, the staff requested that the applicant justify that the contents remain within the BTC and BFA-tanks under HAC. In its response, the applicant added some discussion in Section 5.3.1.1.2 of the application and revised the dose rate analysis to add a point source in the amount equivalent to the allowable non-fixed contamination at the missing section of the bottom plate.

Non-fixed contamination is not the only source that could relocate. As discussed in first round RAI 5-5, the contents are not restricted in geometry. Section 1.2.2 of the application states:

"Generally BTCs will not be loaded with segments of exactly the same geometry. Segments are not stabilized in the BTC, and will move if the BFA-Tank is upset. II The applicant states on page 5-17 of the application that "it is assumed that the plate rotates 45 degrees, which exposes a section about 300 mm wide along the entire length of the tank. II Therefore the contents could relocate to outside of the BTC plates. This scenario was not analyzed and the staff finds that the applicant's model is non-conservative. The applicant needs to provide an analyses to determine the dose rate under this scenario and demonstrate that the package meets the regulatory requirements of 10 CFR 71.51 (a)(2).

The staff performed a confirmatory evaluation and compared the dose rates with a similar modeling assumption of the bottom BTC plate as done in the application (i.e. in the same location but partially removed) and compared it to a model with the BTC plate rotated by 45 degrees. The staff found that the BTC plate rotated by 45 degrees would result in a significant increase in HAC dose rates that exceed the limit in 10 CFR 71.51 (a)(2). The staff's model assumed that the contents with maximum specific activity relocated to the other side of the plate (see Figure 5-3-1 below).

In addition, Section 2.2.8 of the application states that "the materials used to construct the BFA-Tanks and the BFA-Tank Cassettes, which are loaded inside the HI-STAR ATB 1T transport cask, do not require fracture toughness testing for the following reasons...A relocation of the top or bottom plates of the BFA-Tank Cassette, on the other hand, cannot be entirely ruled out based on geometric considerations. Therefore, as described in Section 5.3.1.1.2, a sensitivity study has been performed in Chapter 5 to determine the external dose rate at 1-meter assuming that roughly one quarter of the BTC bottom plate is conservatively removed from the analytical to Holtec Letter 2404013-NRC Page 36 of 43

model. As shown in Table 5.4.4, the calculated dose for this extremely conservative geometry is less than the regulatory limit by a factor of almost 2. II However, the staff finds that removing a part of the BTC bottom plate is not conservative as compared to rotating the plate and assuming that source material relocates to the other side based on the staff's calculations.

The applicant needs to either:

Restrict the contents so that it cannot relocate to the other side of the BTC plates under HAC, or Calculate external dose rates under HAC for contents with consideration of the potential content relocation assuming bounding configuration for the bottom BTC plate and justify the modeling assumptions are bounding.

Section 5.5.3.1, "Configuration of Source and Shielding," of NUREG-1609 states:

"Ensure that any changes in configuration (e.g., displacement of source or shielding, reduction in shielding) resulting under normal conditions of transport or hypothetical accident conditions have been included, as appropriate. This information is needed by the staff to determine to Holtec Letter 2404013-NRC Page 37 of 43

compliance with 10 CFR 71.51 (a)(2).

Figure 5-3-1: HAC Model of ATB-1T with Rotated BTC bottom plate Holtecs Response to RAI 5-3 To ensure that accident dose rates are below the regulatory requirements of 10CFR71.51(a)(2) an additional 5/8 inches thickness of steel is added to the bottom of the HI-STAR ATB 1T transportation cask. Drawing 9786R5 is also updated with this dimensional change. The shielding accident model is updated to assume that the cassette bottom plate, if dislodged during an accident, is not credited with providing any additional shielding. Assuming the cassette bottom plate is completely gone is more conservative than the model shown in the NRC provided RAI Figure 5-3-1, and alleviates the need of analyzing different configurations where the tilt of the cassette plate may be at different angles, or may not even be in contact with the bottom plate of the BFA Tank after the accident. Table 5.1.3 is updated with accident conditions dose rates that include the case with the cassette bottom plate completely removed from the Source Material 1metertoHACdosepoints BottomBTCPlate to Holtec Letter 2404013-NRC Page 38 of 43

shielding accident conditions model. Additional description/justification is added to Sub-Paragraph 5.3.1.1.2. Figure 5.3.10 is added to show the accident configuration where the BTC bottom plate is not credited.

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Chapter 8 - Acceptance Test and Maintenance Program Evaluation NRC RAI 8-1 Provide acceptance criteria to ensure the seals (that have been removed from the CLLS) do not have an excessive compression set that could affect seal performance.

As part of the response to RAI 8-4, dated August 9, 2017, Table 8.2.1 and Section 8.2.4(v) of the revised application state the seals that have been removed from the CLLS will be visually inspected to ensure that the seal projects past the plane of the top seating surface of the seal groove. This criterion may not be sufficient because O-ring performance is dependent on having sufficient size and flexibility to deform within the groove when pressurized.

This information is required by the staff to determine compliance with 10 CFR 71.43(d)(f), and 71.51(a).

Response to RAI 8-1 The specifications and critical characteristics (i.e. size, material, springback, temperature limits, etc.) for the O-rings are provided in Table 2.2.2 and licensing drawing package in Section 1.3 of the SAR. The acceptance criteria provided in Section 8.2.4(vi) and Table 8.2.1 provide assurance that during usage and post maintenance activities the leakage criterion continues to be met, indicating the seals critical characteristics or properties have not degraded so as to compromise the safety function, and ensuring compliance with 10 CFR 71.43(d)(f) and 71.51(a). Visual inspection of the seals is one of three layers of acceptance or replacement criteria provided in Section 8.2.4 for safety. Specifically, visual inspections are considered a preventative and defense-in-depth indicator for ALARA purposes, since pre-shipment leakage testing (SAR Section 8.1.4) of the seals which follows the inspection of the seals and installation/locking of CLLS is the go or no-go indicator with respect to package allowable leakage. Similar approach has been approved by NRC for the HI-STAR 190 (USNRC Docket 71-9373).

Visual inspection of the seals is a qualitative check to ensure they do not exhibit excessive compression set or other damage. The NRC comment is correct that, as a stand-alone acceptance criteria, an inspection to confirm that the seal projects past the plane of the top seating surface of the seal groove is not sufficient to ensure effective o-ring performance. This text is therefore replaced with no evidence of closure seal compression set, such as flattening of the visible seal surface which provides a more expansive qualitative inspection criteria, beyond the originally specified criteria.

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NRC RAI 8-2 Explain the rationale for not replacing a pre-qualified gasket in Note 2b in Table 8.1.1.

The response to RAI 8-5, dated August 9, 2017, indicated that Note 2 was added to Table 8.1.1.

However, the rationale for Note 2b (i.e. the prequalified gasket was never replaced) is not clear for the staff. Therefore, staff is unable to evaluate whether the operation/maintenance of the ITS component will result in the appropriate sealing that will meet 10 CFR 71.51.

This information is required by the staff to determine compliance with 10 CFR 71.51(a).

Response to RAI 8-2 Note 2 was added to Table 8.1.1 of the SAR in accordance with Section 7.6.4 of ANSI N14.5 (2014). Section 7.6.4 of ANSI N14.5 states acceptance criterion for pre-shipment leakage rate testing shall be either (1) a leakage rate of not more than the reference air leakage rate, or (2) no detected leakage when tested to a sensitivity of at least 1x10-3 refcm3/s. It further requires that reusable seals that have been replaced shall demonstrate leakage rate according to reference air leakage rate criterion. Therefore the alternative leakage criterion in Note 2b of Table 8.1.1 for no detected leakage when tested to a sensitivity of at least 1x10-3 refcm3/s is applicable only to reusable prequalified gaskets that are not replaced.

For clarity, Note 2 in Table 8.1.1 is changed to:

Per ANSI N14.5 (para. 7.6.4), pre-shipment acceptance testing of gaskets may be based on acceptance criteria of No Leakage Detected when tested to a sensitivity of 1x10-3 ref-cm3/s under the following condition:

a. Joint gasket has been previously installed and accepted based on testing to a leak rate not more than the reference air leakage rate specified in this Table;

b. Joint gasket has not been replaced subsequent to acceptance testing;

c. Joint gasket is reusable (e.g. elastomeric seal).

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NRC RAI 8-3 Clarify that the Level III Specialist described in Section 8.1.4 is trained for the leak testing examination method.

The revised language in Section 8.1.4 mentions the role of the American Society for Nondestructive Testing (ASNT) Level III Specialist but does not specify that the individual is to be trained in the leak testing examination method.

This information is required by the staff to determine compliance with 10 CFR 71.51(a).

Response to RAI 8-3 Section 8.1.4 of the HI-STAR ATB 1T (Proposed Rev. 2C) SAR has been revised in accordance with Section 8.8 of ANSI N14.5 (2014) to state that the ASNT Level III Specialist approving leak testing procedures shall be qualified and certified in the nondestructive method of leak testing for which procedures are written.

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NRC RAIs 8-4 through 8-10 These RAIs are related to the QA programs for BFA-Tanks and Cassettes not manufactured by Holtec. Holtec has added Condition 8 to the proposed CoC and a requirement to Section 8.1.1 of the SAR, which mandate that for casks to be transported in the USA, BFA-Tanks and BFA-Tanks Cassettes shall be manufactured under a US NRC approved QA program. Therefore, responses to these RAIs are not required.

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