ML20290A822

HI-STORM 100 CoC Renewal Responses to Requests for Additional Information

ML20290A822
Person / Time
Site:	Holtec
Issue date:	10/16/2020
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards
Shared Package
ML20290A819	List: ML20290A820 ML20290A822 ML20290A824 ML20290A825
References
5014911
Download: ML20290A822 (25)

Text

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 RAI 21 Provide a justification for the exclusion of importanttosafety (ITS) systems, structures, and components (SSCs) from the aging management review for those cases where the SSCs were stated not to have an intended function in the period of extended operation. In lieu of a justification, revise the aging management review to include those SSCs.

The following subcomponents are identified as ITS in the respective tables of the renewal application:

Table 2.22 of the renewal application - Intended Safety Functions of MPC Subcomponents

• Vent and Drain Tube

• Vent and Drain Cap

• Vent and Drain Sleeve Inserts

• Vent and Drain Cap Seal Washer Table 2.23 of the renewal application - Intended Safety Functions of HISTORM Overpack Subcomponents

• Lid Stud Washer Table 2.24 of the renewal application - Intended Safety Functions of HITRAC Transfer Cask Subcomponents

• Fill Port Caps

• Transfer Lid Wheel Track

• Transfer Lid Door Stop Block

• Transfer Lid Door Stop Block Bolt The application indicates that the intended function for these ITS subcomponents is N/A, which is defined as the component does not have a function in the period of extended operation and is NITS

[not important to safety]. The renewal application does not provide a basis for these conclusions.

Furthermore, the staff notes that HISTORM 100 Final Safety Analysis Report (FSAR), HI2002444, Revision 18, Section 8.3.1 discusses the unloading operations that involve the general actions necessary to prepare the multipurpose canister (MPC) for unloading, flood the MPC cavity, remove the lid welds, unload the spent fuel assemblies, and recover the HITRAC and empty MPC. It is unclear to the staff how the functions of the MPC and HITRAC subcomponents during these activities were considered in the scoping evaluation.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Below are the responses pertaining to the components listed in RAI 21 from Table 2.22 of the renewal application:

Vent and Drain Tube, Vent and Drain Cap - The intended function for these ITS components has been updated in Table 2.22 to Retrievability since the components serve this function during potential system unloading operations in the period of extended operation. Additionally, these components have been added to Table 3.31 as part of the aging management review under the guidance of NUREG2214.

Vent and Drain Sleeve Inserts - This component has been removed from Table 2.22 of the renewal application since its evaluation is not required because it is not a component that is described in the Page 1 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 FSAR and is not a component included in any licensing drawing. The component was included in the initial application in error.

Vent and Drain Cap Seal Washer - The component safety classification was designated as ITS in error in the renewal application. As seen in FSAR Table 2.2.6, its safety classification is NITS, this has been updated in the license renewal application. Since the safety classification should be NITS, and the vent and drain cap seal washer does not impact any ITS component, these subcomponents are not inscope for aging management.

Below is the response pertaining to the component listed RAI 21 from Table 2.23 of the renewal application:

Lid Stud washer - The intended function for this ITS component has been updated in Table 2.22 to Structural Integrity for the period of extended operation. Additionally, this component has been added to Table 3.32 as part of the aging management review under the guidance of NUREG2214.

Below are the responses pertaining to the components listed RAI 21 from Table 2.24 of the renewal application:

Fill Port Caps - The intended function of the component has been updated in Table 2.24 to structural integrity which aligns with the function designation in Table 2.2.6 of the FSAR, as it was labeled N/A in error. Similar to the determination that there is susceptibility to general, pitting and crevice corrosion for the fill port plugs in Table 410 of NUREG2214, the fill port caps are now included in Table 3.34 of the renewal application as part of the aging management review.

Transfer Lid Wheel Track, Transfer Lid Door Stop Block, Transfer Lid Door Stop Block Bolt The intended functions of the components have been updated in Table 2.24 to Structural Integrity since the components serve this function during potential system unloading operations in the period of extended operation. Additionally, the components have been added to Table 3.34 as part of the aging management review to address their susceptibility to general, pitting and crevice corrosion as indicated in Table 410 of NUREG2214.

Below is the response pertaining to the designation of ITS subcomponents intended function as N/A:

There are no longer any ITS subcomponents in the scoping evaluation with the intended function designation of N/A.

Below is the response pertaining to unloading operations of MPC and HITRAC components listed in this RAI:

Any MPC components listed in RAI 21 that were determined to be inscope have been added to the evaluations in Chapter 3 to determine credible aging mechanisms and any needed aging management activities.

The HITRAC components listed in RAI 21 have all been included in the aging management review and will fall into the Transfer Cask AMP for detection of aging effects.

Page 2 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 RAI 22: Provide a justification for the exclusion of the Pedestal Plate for the Model 100 HISTORM overpack in the scoping and aging management review.

FSAR Table 2.2.6, Materials and Components of The HiStorm 100 System Overpack indicates that the Pedestal Plate (100) and Pedestal Baseplate (100S) are ITSB components. Table 2.23, Intended Safety Functions of HISTORM Overpack Subcomponents, of the renewal application identifies the component Pedestal Baseplate for the Model 100S only.

Based on the FSAR, it appears that the Pedestal Plate for the Model 100 is within the scope of renewal and should be assessed in the scoping and aging management review.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 2.23 has been updated to include the Model 100 and applicable licensing drawing in the Pedestal Baseplate row, incorporating the Model 100 Pedestal Baseplate into the scoping evaluation.

Since the Model 100 and Model 100S are both constructed using the same material options (SA51670 or SA51570), are the same thickness and are exposed to the same environment in the period of extended operation, no further changes are needed to the aging management review chapter as Table 3.32 includes the pedestal baseplate and does not specify between models of the overpack which inherently includes both models.

RAI 23: Provide a justification for the discrepancy between the HISTORM 100 FSAR and the renewal application on the safety classification for the 100S Lid Washer subcomponent of the Overpack.

FSAR Table 2.2.6 for the Overpack indicates that the 100S Lid Washer is an ITSB component. Table 2.23, Intended Safety Functions of HISTORM Overpack Subcomponents, of the renewal application identifies the component Lid Washer as a NITS component for the Model 100 and 100S overpacks.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 2.23 has been updated to distinguish between the safety classes for the 100 and 100S models.

The model 100 remains classified as NITS since it does not impact any ITS component in the period of extended operation and was not included in FSAR Table 2.2.6 since it is a NITS component. The Model 100 maintains the N/A designation and will not be included in the aging management review. The model 100S now has a separate line in Table 2.23 to clarify that the component for that model is ITS and its intended function in the period of operation has been changed to Structural Integrity. The component for this model has been included in Table 3.32 as part of the aging management review in accordance with Table 48 of NUREG2214.

RAI 24: Provide a scoping evaluation and, if necessary, an aging management review for HISTORM 100 storage system SSCs that were not addressed in the renewal application.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Several SSCs are identified as having an ITS function in HISTORM 100 FSAR Table 2.2.6; however, they do not appear to be addressed in the scoping evaluation. These include:

• 100S Version B Base Shield Block (ITSB, Overpack)

• Vent and Drain Tube, Optional (ITSC, MPC)

• Threaded Disc, Plug Adjustment (ITSC, MPC)

• Vent and Drain Plug (ITSC, MPC)

• Bottom Flange Gussets (HITRAC 100D and 125D only) (ITSB, HITRAC)

In addition, several nonITS SCCs in FSAR Table 2.2.6 also were not addressed in the scoping evaluation, including:

• Drain Line Guide Tube (NITS, MPC)

• Thread Shield Cap (NITS, MPC)

• Retaining Ring (NITS, MPC)

NUREG-1927, Revision 1 provides guidance that the scoping evaluation includes all SSCs identified in the designbases documents to ensure that they are properly differentiated as either within or not within the scope of renewal on the basis of either (1) having an ITS function or (2) they are NITS, but their failure affects an ITS function.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

100S Version B Base Shield Block - This component has been included in the scoping evaluation in Table 2.23 and the aging management review in Table 3.32 using the aging management guidance given for this component in Table 48 of NUREG2214.

Optional Vent and Drain Tube, Threaded Disc Plug Adjustment, Vent and Drain Plug, Drain Line Guide Tube, Thread Shield Cap, Retaining Ring These components have been included in the scoping evaluation in Table 2.22 and their intended function is listed as Retrievability since the components serve this function during potential system unloading operations in the period of extended operation.

Additionally, these components have been added to Table 3.31 as part of the aging management review under the guidance of NUREG2214.

Bottom Flange Gussets (HITRAC 100D and 125D only) This component has been included in the scoping evaluation in Table 2.24 and the aging management review in Table 3.34 using the aging management guidance given for the bottom flange in Table 410 of NUREG2214 since the bottom flange is made of the same material, exposed to the same environment and has the same ITS classification.

RAI 25: Revise the renewal application to reflect changes to the HISTORM 100 system in the classification of SSCs that have been identified during the NRC staffs review of Amendment No. 15 to the CoC.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Table 1.21 of the renewal application provides a description of the scope of the amendment, its approval time, identification of the FSAR which provides the licensing basis, and a pointer to where the aging management programs (AMPs) for different amendments are located in this application. The staff noted that Amendment No. 15 is still currently under NRC review. In addition, the staff noted that Table 2.22, Table 2.23 and Table 2.24 provide the intended safety functions of the MPC, Overpack and Transfer Cask subcomponents, and in some instances identifies the aspects of the HISTORM 100 systems addressed in Amendment No. 15.

In response to NRC RAI 81 for the HISTORM 100 CoC No. 1014 Amendment No. 15, in a letter dated April 28, 2020 (ADAMS Accession No. ML20128J292), the classification of the HITRAC MS lift blocks and attachment bolts were clarified to be ITS. However, it does not appear these components are included in the scoping evaluation performed in Section 2 of the renewal application.

For these and any additional safety classification changes made during the staffs review of Amendment 15 to the HISTORM 100 CoC, revise the renewal scoping and aging management review to accurately reflect the design bases of the storage system.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

As stated in the response to the NRC RAI referenced above (ML20128J292), the HITRAC MS lift blocks and their attachment bolts are ancillary components, not part of the licensed HITRAC. This is similar to the lift yokes, MPC lift cleats, and other ancillaries that outside the scope of license renewal, since they are not part of the license. The up to date versions of the licensing drawings from Amendment 15 were reviewed and confirmed that all subcomponents were included in the Section 2 renewal application tables.

RAI 26: Justify why the subgrade material surrounding the cavity enclosure container of the vertical ventilated module (VVM) was not scoped into the renewal review. Alternatively, include the subgrade in the renewal scope and provide an aging management review (AMR) and any corresponding AMPs or timelimited aging analyses (TLAAs) as necessary.

On sheet 3 of the licensing drawing 4501 for the HISTORM 100U storage system, the applicant identified the material surrounding the cavity enclosure container of the VVM module as subgrade.

This material is credited in the shielding analyses of the FSAR. However, the renewal application does not consider this material in its scoping analysis.

In Table 5.I.3 of the FSAR, the applicant identified this material as soil. NUREG1801, Generic Aging Lessons Learned (GALL) Report (ADAMS Accession No. ML103490041) and EPRI 1015078, Plant Support Engineering: Aging Effects for Structures and Structural Components (Structural Tools), identify the aging effects for soil, including loss of material due to erosion, loss of form due to settlement/cracking, and change in properties due to loss of moisture (desiccation). The information in the renewal application is not sufficient for the staff to assess if these aging effects impact the shielding function of subgrade material as part of the VVM.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 The staff needs this information to determine if the HISTORM 100U meets the regulatory requirements of 10 CFR 72.240(c).

Reference:

Electric Power Research Institute (EPRI). Plant Support Engineering: Aging Effects for Structures and Structural Components (Structural Tools). EPRI 1015078. Palo Alto, CA. 2007.

Holtec Response:

In accordance with NUREG1801 and NUREG2214, Table 3.32 of the renewal application has been updated to include the aging management review of the subgrade material surrounding the VVM. Table 2.23 of the renewal application has been revised to include subgrade as a component of the HISTORM 100U system.

Additionally, 100U Concrete AMP of the application has been revised to include monitoring of the sub grade using dose rate measurements.

RAI 27: Clarify and justify the design bases of the MPC Plugs for Drilled Holes and provide further information to support their aging management review.

MPCs include canister lid lift holes, which are plugged to provide radiation shielding. In its review of the renewal application, the staff identified potential inconsistencies in the design bases of the plugs and also identified the need for justification to support the conclusion that no aging management activities are required. As a result, the staff requests the following:

1. Clarify and provide the technical justification to support the safety classification of the plugs as NITS in Tables 2.22 and 3.31 of the renewal application.

The staff notes that HISTORM 100 FSAR Table 2.2.6 classifies the plugs as NITS; however, Drawing 3923, Sheet 9, identifies these items as ITS (for the optional lifting hole plug designs).

Both the renewal application and the FSAR identify the plugs as having a shielding function. The staff notes the top lid of the canister is modeled as a solid piece of steel in the MCNP model for the shielding analyses (within the HISTORM 100 FSAR), and the drilled holes on the lid were not modeled. As such, it appears the drilled hole plugs are credited in the shielding analyses.

2. Clarify if the plugs may be welded by design and/or have been welded in existing MPCs due to fabrication adjustments. The staff notes that Drawing 3923, Sheet 9, Note 2 appears to include an option for welding.

3. Provide additional support for the conclusion that no aging management activities are needed to manage the aging of the plugs.

Table 3.31 of the renewal application appears to identify a credible aging effect for the plugs (loss of material due to pitting, crevice, and microbiologically influenced corrosion); however, no aging management activity is proposed. Provide the basis for not managing this identified aging effect.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 In addition, if there may be welds associated with the plugs, provide justification to support the conclusion that stress corrosion cracking is not an aging effect requiring management. The staff notes that residual stresses associated with welds may make those locations susceptible to cracking, and, as a result, the example aging management program for canisters in NUREG2214 recommends that all known weld areas be monitored to ensure that the canister confinement function is maintained.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

1. The Plugs for Drilled Holes listed in Tables 2.22 and 3.31 of the renewal application reference the plugs described in Zone D4 of Drawing 3923, Sheet 7, and are accurately described as NITS in both FSAR Table 2.2.6 and in the renewal application. These plugs do have a shielding function in the initial storage period and the period extended operation, but are still considered NITS components as the components do not meet the criteria to qualify as an ITS A,B or C component per NUREG/CR6407.

The optional lifting hole plug displayed in Drawing 3923, Sheet 9, has been added as an ITS component to Table 2.22 as part of the scoping evaluation and Table 3.31 as part of the aging management review using the guidance provided in NUREC1927 and NUREG2214. These are repair plugs to be used for lifting in the instance of thread damage to the initially drilled lifting holes and their primary function is for structural integrity.

2. Note 2 of Drawing 3923, Sheet 9, is only applicable for optional lifting hole plugs to be used for transportation applications (Plug Design Option D). Alternatively, Plug Design Options A,B and C are applicable for storage operations and all of these plug design options are welded to the lid by design and in practice.

The Plugs for Drilled Holes described in Drawing 3923, Sheet 7 and in the response to (1.)

above are not welded by design or in practice.

3. Table 3.31 of the renewal application already includes MPC AMP as an aging management activity for the stress corrosion cracking aging mechanism for the Plugs for Drilled Holes. As stated in the response in (2.) above, the Plugs for Drilled Holes are not a welded component.

Although not a welded component, Section 3.2.2.5 of NUREG2214 provides language that acknowledges stress corrosion cracking requires the presence of tensile stress which commonly exists at the contacts between components and bolted structures for stainless steel components in a sheltered environment. This is the reasoning for including an aging management activity for stress corrosion cracking for the Plugs for Drilled Holes. Microbiologically influenced corrosion has been removed as an aging mechanism in Table 3.31 of the renewal application for this component since Section 3.2.2.4 of NUREG2214 concludes that aging management is not required during the 60year timeframe for stainless steel subcomponents in a sheltered environment. Additionally, MPC AMP has been included as an aging management activity for the pitting and crevice corrosion aging mechanisms since Section 3.2.2.2 of NUREG2214 informs that pitting and crevice corrosion are credible aging mechanisms for stainless steel components in a sheltered environment.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Furthermore, as seen in the response to (1.) above, the optional lifting hole plug displayed in Drawing 3923, Sheet 9, has been added to Table 3.31 of the aging management review. This plug is a welded item and Table 3.31 now includes stress corrosion cracking as a credible aging mechanism which requires MPC AMP as an aging management activity for this component.

Additionally, pitting and crevice corrosion aging mechanisms have been included as credible aging mechanism using the guidance provided in Section 3.2.2.2 of NUREG2214 and MPC AMP is now an aging management activity for these types of aging mechanisms for this component.

RAI 31: Identify any SSC subcomponents that have been excluded from further evaluation in the aging management review because they already have their condition monitored at some established frequency. Provide an evaluation of the credible aging effects and a justification that the existing monitoring activities are adequate to manage those aging effects.

Section 3.2 of the renewal application states, Any SSC subcomponents that do not perform or support an intended function or already have their condition monitored at some established frequency are excluded from further evaluation in the aging management review (emphasis added).

In accordance with 10 CFR 72.240, Conditions for spent fuel storage cask renewal, the safety analysis report must provide a description of the AMP for management of issues associated with aging that could adversely affect structures, systems, and components important to safety. The staff recognizes that existing site procedures can be a part of the aging management strategy; however, the renewal application should demonstrate the basis for the approach.

Thus, it is not clear to the staff which SSC subcomponents already have their condition monitored at some established frequency that were excluded from further evaluation in the aging management review, and if the monitoring of those subcomponents is adequate to manage the issues associated with aging.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

The language related to having their condition monitored at some established frequency related to the possibility of components that are already required to be replaced at some defined period. In some casks this might be a seal that is replaced every few years. This was considered in the scoping of the HI STORM 100 casks, however, no components on this particular cask design were determined to fall under this category.

RAI 32: Provide a justification that loss of material (precursor to stress corrosion cracking) due to pitting and crevice corrosion in a sheltered environment for the closure ring subcomponent of the MPC is not an aging effect requiring management.

Table 3.31 of the renewal application states cracking due to stress corrosion cracking (SCC) is a credible aging effect for the MPC; however, loss of material due to pitting and crevice corrosion is not identified as a credible aging effect. The staff notes that pitting and crevice corrosion are considered precursors to Page 8 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 SCC, and the MPC AMP relies on inspections for pitting and crevice corrosion to monitor the condition of the MPC confinement boundary. In addition, other MPC confinement boundary components in Table 3.31 (e.g., shell, baseplate) identify a credible corrosion aging mechanism. It is unclear to the staff why the closure ring appears to be managed in a unique manner.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Using the guidance given in Table 47 of NUREG2214 for the closure ring, Table 3.31 of the renewal application was updated to include loss of material due to pitting and crevice corrosion as an aging effect for the closure ring, and to include MPC AMP as an aging management activity for these types of corrosion.

RAI 33: Provide a justification that changes in dimension due to thermal creep of the high burnup fuel cladding in a helium environment is not identified as an aging effect requiring management.

The renewal application did not identify changes in dimension due to thermal creep in a helium environment as an aging effect requiring management.

The High Burnup Fuel Assembly AMP uses the joint EPRI and DOE High Burnup Dry Storage Cask Research and Development Project (HDRP), conducted in accordance with NUREG1927, Revision 1 to monitor the condition of the fuel cladding to ensure it maintains its designbasis configuration. One of the parameters monitored by that program is the change in cladding dimensions due to creep. As documented in NUREG2214, Section 3.6.1.3, the evidence to date that supports fuel cladding performance with respect to creep is based only on shortterm testing. Therefore, the staff issued guidance in Appendix D of NUREG1927, Revision 1 for the use of a demonstration program to provide confirmatory data that creep will not challenge the performance of the fuel cladding.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Using the guidance given in Table 425 and Section 3.61.3 of NUREG2214 and Appendix D of NUREG 1927, Table 3.33 of the renewal application has been updated to add thermal creep as an aging mechanism for high burnup fuel cladding in a helium environment and High Burnup Fuel AMP has been added as an aging management activity.

RAI 34: Provide a justification that the steel water jacket subcomponents in the HITRAC system exposed to a water environment, as identified in Table 3.34 of the renewal application, are not subject to loss of material due to general, pitting and crevice corrosion.

Table 3.34, Aging Management Review of HITRAC Subcomponents, of the renewal application includes the following steel subcomponents that are potentially exposed to a water environment and indicate that there are no aging effects requiring management per NUREG2214.

• Outer Shell

• Radial Ribs

• Water Jacket End Plate

• Lower Water Jacket Shell Page 9 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911

• Water Jacket Bottom Ring

• Water Jacket Top Plates

• Water Jacket Bottom Plate The staff noted that the NUREG2214 concluded that components in the HITRAC system exposed to demineralized water or 25% ethylene glycol solution may be susceptible to loss of material due to general, pitting and crevice corrosion, and should be managed for the effects of aging. NUREG2214 provides the generic conclusion that steel components exposed to moisture (including in sheltered or outdoor air environments) are susceptible to corrosion. Consequently, the NUREG2214 Example AMP, Transfer Casks indicates that aging management activities are necessary for subcomponents exposed continuously or intermittently to a liquid neutron shield. Thus, the applicants basis for indicating that these subcomponents exposed to a water environment are not subject to aging effects requiring management is not clear to the staff.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 3.34 of the renewal application has been revised to include pitting and crevice corrosion, and general corrosion as aging mechanisms for HITRAC steel subcomponents listed in RAI 34 which are exposed to a water environment. Additionally, HITRAC AMP has been included as an aging management activity for these components to address the potential aging mechanisms. The aging mechanisms and aging activity incorporated are in accordance with the guidance given in Table 410 of NUREG2214.

RAI 35: Clarify the discrepancy for the fabrication material between the renewal application and FSAR for the MPC Upper Fuel Spacer Bolt and the Overpack Lid Stud.

Table 3.31, Aging Management Review of MPC Enclosure Vessel Subcomponents, of the renewal application indicates that the Upper Fuel Spacer Bolt is fabricated from A192B8 or equivalent.

However, the staff noted that FSAR Table 2.2.6, MATERIALS AND COMPONENTS OF THE HISTORM 100 SYSTEM MPC indicates that the Upper Fuel Spacer Bolt is fabricated from A193B8 (or equiv.).

Table 3.32: Aging Management Review of HISTORM 100 Overpack Subcomponents, of the renewal application indicates that the Lid Stud, Tee Handle Bolt & Nut is fabricated from SA194, SA564640 and/or SA193B7. FSAR Table 2.2.6 indicates that the lid stud and nut component is fabricated from SA564630 or SA 193B7 (stud) and SA 1942H (nut). Based on these two examples, it appears to the staff that there is a discrepancy in the fabrication materials identified in the renewal application and the FSAR.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 3.31 has been updated to change the Upper Fuel Spacer Bolt material to A193B8 to match the material specification from FSAR Table 2.2.6 and Sheet 5 of licensing drawing 3923.

Table 2.22 and 3.32 have been updated to create separate lines to distinguish between the lid stud and lid stud nut. The material for the lid stud in Table 3.32 has been changed to SA 193B7/ SA 564630 to Page 10 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 match the material specification from FSAR Table 2.2.6 and licensing drawing BM1575. Likewise, the material for the lid stud nut in Table 3.32 has been changed to SA 1942H to match the material specification from FSAR Table 2.2.6 and licensing drawing BM1575.

RAI 36: Clarify the discrepancy regarding the two different aging management approaches for the two subcomponents made of HoltiteA. Provide additional justification for why cracking due to radiation embrittlement, loss of fracture toughness and loss of ductility due to thermal aging, and loss of shielding due to boron depletion are not credible aging effects for these HoltiteA components to be addressed by a timelimited aging analysis/aging management program or a supporting analysis.

Table 3.34: Aging Management Review of HITRAC Subcomponents, of the renewal application includes several AMR items for subcomponents fabricated from HoltiteA that are not evaluated in a consistent manner.

• For the AMR items associated with the Top Lid Shielding, the application does not identify a thermal or radiation related aging effect (on the basis of laboratory testing) and indicates that the current licensing basis does not include a specific timebased evaluation of the material, so there is no analysis to meet the requirements to be classified a TLAA. Therefore, the application concluded that no AMP or TLAA is required.

• For the AMR items associated with the Transfer Lid Door Shielding, the applicant proposed the HITRAC Holtite Material TLAA as the aging management activity to address radiation embrittlement, thermal aging, and boron depletion.

It is not clear to the staff what the basis is for the two different aging management activities for the two subcomponents which are made of the same material. Also, while the Transfer Lid Door Shielding line items reference the HITRAC Holtite Materials TLAA, that TLAA is not described anywhere in the application.

In addition, NUREG2214 identifies cracking due to radiation embrittlement, loss of fracture toughness and loss of ductility due to thermal aging, and loss of shielding due to boron depletion as credible aging effects for these HoltiteA components to be addressed by a timelimited aging analysis/aging management program or a supporting analysis.

Based on its review of Holtec Report HI2002420, HoltiteA: Results of Pre and PostIrradiation Tests and Measurements, Revision 1, it is not clear to the staff how the results from this study (1) demonstrate that the shielding function of these components are not challenged when considering the credible aging effects and (2) are bounding of the conditions these components are exposed to over the proposed period of extended operation in terms of radiation field/flux and temperatures.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

The aging management activity for the Transfer Lid Door Shielding subcomponent in Table 3.34 of the renewal application has been updated to keep it consistent with the aging management activity of Top Lid Shielding.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Reference [3.3.5] was added to the Section 3.6 references and referenced in paragraph 3.3.4.5 of the renewal app as a form of supporting analysis to address potential aging mechanisms for Holtite A, thus no longer requiring HITRAC Holtite Material TLAAs. Reference [3.3.5]and HI2002420, which is referenced in [3.3.5], summarize the qualification tests required to characterize the performance of HoltiteA as a shielding material. The reports show that HoltiteA demonstrated hydrogen retention after thermal aging and exposure to high temperature and neutron and gamma radiation, thereby proving to be effective for neutron shielding application in the cask. [

PROPRIETARY INFORMATION WITHHELD PER 10CFR2390

]Thus, the above referenced reports show bounding conditions for HoltiteA qualification tests in terms of radiation flux and temperature and conclude that HoltiteA is thermally stable for use in HISTORM 100 cask and is suitable for the radiation exposure expected throughout the period of extended operation.

RAI 37: Provide the language for the footnotes in Table 3.32 of the renewal application.

Table 3.32: Aging Management Review of HISTORM 100 Overpack Subcomponents, of the renewal application has a statement that this table includes footnotes. However, it does not appear to the staff that Table 3.32 of the renewal application provides the language for footnotes 1 through 3.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

The number of footnotes was reduced to 2 and language was provided in the footnotes for their applicability as follows:

Note 1: The term embedded refers to the fact that the individual component is mechanically sealed and is not exposed to any environment.

Note 2: The term general corrosion refers to loss of material due to corrosion, proceeding at approximately the same rate over a metal surface, also referred to as uniform corrosion.

RAI 38: Provide a justification that the insulation material for the HISTORM 100U system does not require aging management during the renewal period.

Table 3.32 Aging Management Review of HISTORM 100 Overpack Subcomponents, of the renewal application indicates that Insulation that is embedded (steel) is not subject to aging effects requiring management.

FSAR Section 3.I.4.1 indicates that this insulator material is either Kaowool ceramic fiber insulation or alternatively, a Holtec approved equivalent that meets the acceptance criteria set forth in FSAR Section 3.I.4.1.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 The renewal application does not provide a basis for why the insulation material for the HISTORM 100U system does not require aging management during the renewal period. Although the renewal application cites NUREG2214 as a basis for its conclusion, the staff noted that Table 48 of NUREG2214 indicates that cracking due to radiation embrittlement may be an aging effect requiring management for ceramic fiber insulation. Further, Section 3.5.2.1 of NUREG2214 provides guidance that a review of the radiation effects is performed on a casebycase basis of the insulation material and that the application addresses this potential aging effect.

This information is needed to evaluate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 3.32 of the renewal application has been updated to specify that Kaowool ceramic fiber insulation (or equivalent) is the insulation material being considered and using the guidance provided in Table 48 of NUREG2214, Table 3.32 of the renewal application has been revised to include radiation embrittlement as an aging mechanism. Supporting analysis for not performing a TLAA or AMP for the material has been provided in paragraph 3.3.2.5 of the renewal application.

RAI 39: For all AMR line items that identify corrosion as a credible aging mechanism that leads to loss of material, provide additional details on the specific corrosion mechanism(s) to be managed.

Tables 3.31, 3.32, and 3.34 of the renewal application include line items for loss of material due to corrosion. No detail on the specific corrosionrelated aging mechanism is provided. The AMPs incorporate these tables of the renewal application by reference to define the scope of the inspections.

As noted in NUREG1927, Revision 1, Section 3.1, it is often necessary to identify the aging mechanisms that are potentially at work to effectively manage an aging effect. For example, the identification of credible localized corrosion mechanisms may inform and prioritize how inspections seek out specific crevice locations or dissimilar metal contacts and how visual inspection parameters (e.g., lighting, distance) are established to ensure the degradation can be detected.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Tables 3.31, 3.32 and 3.33 of the renewal application have been revised to include credible aging mechanisms for loss of material. All the aging mechanisms incorporated are in accordance with the guidance provided in Tables 47, 48 and 410 of NUREG2214.

RAI 310: Provide a justification for the conclusion in Table 3.32 of the renewal application that the steel 100U Container Shell Bottom Plate, which is embedded in concrete, does not require aging management.

Table 3.32, Aging Management Review of HISTORM 100 Overpack Subcomponents, of the renewal application indicates that the steel Container Shell Bottom Plate is exposed to an embedded (concrete) environment and is not subject to aging effects requiring management. The applicant cites NUREG2214 as the basis for its conclusion.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 However, the staff noted that the NUREG2214 concluded that for this subcomponent exposed to an embedded (concrete) environment, may be subject to loss of material due to general, pitting and crevice corrosion when the concrete is subject to water ingress. Furthermore, NUREG2214 provides guidance that a TLAA/AMP or a supporting analysis for aging management. Thus, the applicants basis for not managing the effects of aging for the Container Shell Bottom Plate is not clear.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Using the guidance provided in Table 48 of NUREG2214, Table 3.32 the renewal application has been revised to include the recommended aging mechanisms for container shell bottom plate. Element 4, Overpack AMP Element 4 Detection of Aging Effects of the renewal application has been updated to include inspection of the ISFSI pad directly adjacent to the overpack, which gives indication if inaccessible surfaces of the overpack, including components like container shell bottom, will require additional inspections.

RAI 311: Provide an aging management review and, if necessary, the aging management approach that addresses the Overpack Baseplate and Pedestal Baseplate in contact with the concrete pad.

Table 3.32 of the renewal application includes an aging management review for the steel Overpack Baseplate and Pedestal Baseplate is exposed to a sheltered and airoutdoor environment, respectively.

However, it is unclear whether the AMR items in the renewal application address the portions of the baseplates that are in contact with the concrete pad. The staff notes that NUREG2214 concluded that steel embedded in concrete may be subject to loss of material due to general, pitting, and crevice corrosion if the environment may allow water ingress. Specifically, Table 64 Example Aging Management Program for Monitoring of Metallic Surfaces of NUREG2214 indicates that the condition of metallic surfaces in contact with concrete (i.e., overpack/cask bottoms) are assessed with visual inspections on a justified frequency and sample size.

If the aging management review identifies a credible aging effect, provide the approach, including a basis, that will be used to manage these surfaces (e.g., inspections of adjacent, accessible, surfaces; inspection of pad for signs of corrosion staining; periodic or opportunistic inspections of bottom surface).

Holtec Response:

In accordance with Holtec Drawing 3669, pedestal baseplate is not in contact with the concrete pad. Per Table 64 of NUREG2214, Overpack Aging Management Program in Appendix A of the renewal application has been revised to include inspection of overpack inaccessible surfaces and the ISFSI pad surrounding the overpack. Inspection of the ISFSI pad directly adjacent to the overpack provides indication that inaccessible surfaces of the overpack, including components like the overpack baseplate, may require additional inspections.

RAI 312: Provide a justification that loss of strength due to thermal aging of the aluminum Basket Shims and Solid Shims for the MPC68M/32M does not require aging management during the renewal period.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Table 2.22 indicates that the Basket Shims and Solid Shims for the MPC68M/32M have a structural integrity and heat transfer intended function. Further, Table 3.31 indicates that these subcomponents are fabricated from aluminum and there are no aging effects requiring management.

The staff noted that Section 3.2.3.7 of NUREG2214 indicates that the microstructures of many aluminum alloys may change, given sufficient time at temperature and is commonly called thermal aging. The effect of the thermal aging on mechanical properties will depend on the time at temperature and the microstructure and chemical composition of the aluminum components.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Per Subsections 3.4.4.3.1.8 and 3.3.2.6 of the FSAR and Subsection 3.III.4.12.2 of the renewal application, the aluminum alloy basket shims and solid shims used in the MPC do not bear any load under normal conditions of storage except for any shortterm operations when the cask is transferred horizontally and the shims are subjected to lateral acceleration from the fuel basket and contained fuel. Additionally, Table 2.22 of the renewal application has been revised to remove structural integrity as an intended function for basket shims and solid shims. From Table 32 of NUREG2214, thermal aging is only considered credible for loadbearing components. Since the basket shims and solid shims do not bear any load during the period of extended operation, thermal aging is not considered a credible aging mechanism for these components in the renewal application.

RAI 313: Provide a justification that loss of material due general, pitting and crevice corrosion of the steel HISTORM 100 Overpack Shield Shell component does not require aging management during the renewal period.

Table 3.32 of the renewal application indicates that the steel (SA51670) Shield Shell is exposed to a sheltered environment and is only subject to loss of material properties due to radiation. The staff noted that steel overpack components exposed to a sheltered environment may be subject to additional aging effects that require aging management during the renewal period. Specifically, the staff noted that NUREG2214 Sections 3.2.1.1 and 3.2.1.2 concluded that loss of material due general, pitting and crevice corrosion may be applicable aging effects for steel components exposed to a sheltered environment due to the potential presence of moisture in the sheltered environment.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Table 3.32 of the renewal application lists the environment of the shield shell as sheltered in error. The shield shell was removed from the design in June of 2001, and in older versions of licensing drawing 1495 it can be seen that the shield shell environment is actually embedded in concrete. Moreover, Table 48 of NUREG2214 specifies that the shield shell is embedded in concrete. As such, Table 3.32 of the renewal application has been updated to change the environment of the shield shell to Embedded (concrete).

For the potential aging mechanisms listed in RAI 313, the embedded concrete environment is fully encased and is not subject to water ingress which has the potential to cause general corrosion, pitting and crevice corrosion, and microbiologically influenced corrosion of the component. Therefore, these types of Page 15 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 corrosion have not been included as credible aging mechanisms in Table 3.32 of the renewal application for this component, which is in agreement with Table 48 of NUREG2214.

MPC and Overpack AMPs RAI #1: Provide a justification for the statement that, in lieu of a sitespecific inspection of the Dry Cask Storage System (DCSS), a site may choose to take credit for an inspection done at a different site. Otherwise, revise the renewal application such that the MPC AMP and Overpack AMP only take credit for site specific inspections of the HISTORM 100 System.

As described in the Appendix A of the renewal application, the MPC AMP and Overpack AMP indicate that in lieu of a sitespecific inspection of the Dry Cask Storage System (DCSS) a site may choose to take credit for an inspection done at a different site (i.e., surrogate inspections), as long as the inspection can be shown to have been performed on a reasonably comparable or bounding canister and overpack.

The NRC review of Nuclear Energy Institute (NEI) 1403 Revision 2, Format, Content and Implementation Guidance for Dry Cask Storage OperationsBased Aging Management (ADAMS Accession No. ML18325A207) states that the NRC does not believe there is substantial operating experience for canister examinations for the various susceptibility rankings to understand how the susceptibility assessments may be applied, and surrogates used, across the independent spent fuel storage installation fleet. For other SSCs (e.g., overpack), the NRC comments state that there are limited AMP inspection results and no industry guidance for determining which SSCs may be appropriate for the use of surrogate inspections. Both a guidance document that considers the effects of environmental and operational parameters on aging effects and operational experience gained from conducting AMP inspections are considered necessary for identifying potential surrogates for SSCs other than storage canisters.

Given the limited number of inspections that have been performed at sites that utilize the HISTORM 100 System, the applicants basis for taking credit for an inspection done at a different site as part of the MPC AMP and Overpack AMP is not clear to the staff.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

MPC AMP and Overpack AMP of the renewal application were updated to only take credit for sitespecific inspections of the HISTORM 100 system.

MPC AMP RAI #2:

Include examination methods in the MPC AMP that are capable of identifying and characterizing stress corrosion cracks or provide a justification for how the AMP is otherwise capable of managing this degradation mechanism. Further, describe and provide a justification for the criteria that will be used by the inspector to determine if selected areas of the MPC may be upgraded to a nondestructive examination technique that is capable of identifying and characterizing stress corrosion cracks.

Program Element 4, Detection of Aging Effects of the MPC AMP states, in part, the following methods will be used to manage pitting corrosion and stress corrosion cracking:

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 A visual inspection of the MPC surface shall be performed using a borescope (or equivalent)

This visual inspection shall meet the requirements of a VT3 Examination At the discretion of the inspector, the inspection of selected areas on the MPC may be upgraded to the VT1 standard, as described in ASME Section XI, Article IWA2200, to the extent practical.

The staff noted that the visual inspection methods, alone, are not generally considered to be capable of identifying and sizing pitting corrosion and stress corrosion cracking. In addition, the description of the MPC AMP does not explain or provide a justification for the criteria that will be used to by the inspector to determine if selected areas may be upgraded to a VT1 inspection.

NUREG2214 (see Table 62, Example Aging Management Program for Localized Corrosion and Stress Corrosion Cracking of Welded Stainless Steel Dry Storage Canisters) and Aging Management Guidance to Address Potential ChlorideInduced Stress Corrosion Cracking of Welded Stainless Steel Canisters, Report 3002008193, contains guidance to include a combination of visual inspections and followup surface or volumetric examinations to determine the presence and extent of pitting/crevice cession and stress corrosion cracking. In these guidance documents, visual inspections are not relied on to identify pitting/crevice corrosion and cracking. Rather, they are used to perform an initial screen for areas of corrosion that may be a precursor to cracking. Suspect areas are further examined with techniques capable of identifying and sizing cracks to support an engineering evaluation of canister integrity and confinement.

Absent an examination method capable of characterizing stress corrosion cracks, it is unclear to the staff how the proposed inspection activities will be capable of identifying and responding to cracking.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

In accordance with the guidance provided in Table 62 of NUREG2214, the MPC AMP of the renewal application has been updated to include the visual examination methods used to detect suspect areas that may require further evaluation and the volumetric, surface and visual (remote only) inspection techniques which are utilized for determining the presence and extent of localized pitting/crevice corrosion and stress corrosion cracking..

See Element 4 of MPC AMP, Detection of Aging Effects, for inclusion of volumetric and surface examinations to be conducted.

MPC AMP RAI #3: Provide a justification that the MPC AMP will only include inspections on one canister at each site that uses the HISTORM 100 System regardless of the susceptibility of the site to localized corrosion or SCC. Otherwise, revise the MPC AMP to include criteria for determining the inspection population based on susceptibility at a site, including criteria for reevaluating the inspection population.

Provide a justification that this susceptibility criteria provides adequate aging management of the MPCs.

Program element 4, Detection of Aging Effects, of the MPC AMP states that the inspection shall be performed on one canister at each site that uses the HISTORM 100 System and provides references that will be used for the selection criteria.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Table 62 of the MAPS Report states that for sites conducting a canister examination, there should be a minimum of one canister examined at each site. Preference should be given to the canisters with the greatest susceptibility for localized corrosion or SCC. The staff noted that ASME Code Case N860, Inspection Requirements and Evaluation Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems, provides criteria to determine the inspection population based on susceptibility at the site, including criteria for reevaluating the inspection population.

The staff noted that the MPC AMP does not provide susceptibility criteria for determining the inspection population of canisters at sites that are more susceptible to localized corrosion or SCC.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

MPC AMP of the renewal application has been revised to include a minimum of one canister for inspection without further analyzation. The MPC AMP already indicates that the selection criteria for the canister to inspect shall use the EPRI Technical Report 300200537 susceptibility criteria shall which provides a technical basis to evaluate and score canister and site susceptibility to localized corrosion (chloride induced SCC) which is considered to be the most credible and bounding aging mechanism that might challenge the structural integrity of the MPC. Additionally, the wording has been updated in the MPC AMP to specify the ASME Code Case N860 criteria for determining the inspection population.

MPC and Overpack AMPs RAI #4: Provide a justification that the trending of degradation identified by the MPC AMP and Overpack AMP is not required. In lieu of a justification, provide the criteria and basis, that an inspector will use to determine whether indications will be identified and documented for subsequent inspections, and identified for trending purposes.

Program element 5, Monitoring and Trending of the MPC AMP states changes to the size and location of any areas of discoloration, localized corrosion, and/or stress corrosion cracking should be identified and documented for subsequent inspections. (emphasis added)

Program element 6, Acceptance Criteria of the Overpack AMP states that for the overpack external and internal surfaces, minor rust spots or indications of degraded coatings do not require further evaluation since they do not compromise the ability of the overpack to maintain its function, but should be identified for trending purposes. (emphasis added) The staff noted that trending of degradation identified by the MPC AMP and Overpack AMP appears to be left to the discretion of the inspector, rather than ensuring these conditions are documented and trended to ensure their progression, if any, is monitored.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

The wording of MPC AMP and Overpack AMP of the renewal application was updated to specify the criteria and basis for the inspector to identify the indications and document them for subsequent inspections.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 MPC AMP RAI #5: Revise the MPC AMP to clarify if the examinations include known areas of the canister to which temporary supports or attachments were attached by welding and subsequently removed. If not, provide a technical justification for why these areas are not considered susceptible to chlorideinduced stress corrosion cracking.

Program element 3, Parameters Monitored/Inspected of the MPC AMP states that examinations of the MPC AMP focus on accessible canister welds and weld heataffectedzones. However, as noted in NUREG2214, other known areas of the canister to which temporary supports or attachments were attached by welding and subsequently removed (based on available fabrication records) may be susceptible to localized corrosion and chlorideinduced stress corrosion cracking.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

MPC AMP of the renewal application has been updated to include the inspection of areas of the canister to which temporary supports or attachments were attached by welding and subsequently removed in accordance with the guidance given in Table 62 of NUREG2214.

Overpack AMP RAI #1: Specify the extent (i.e., coverage area) of the examinations that will be performed for the normally accessible external and internal surfaces of the overpack and provide a justification that they will be sufficient to provide adequate aging management of the overpack.

Program element 3, Parameters Monitored / Inspected, and program element 4, Detection of Aging Effect of the Overpack AMP indicates that the overpack external AMP is a visual inspection in order to detect any aging effects and that visual inspection of the overpack annular space and the interior areas of the vents shall be performed using a borescope (or equivalent).

The staff noted that the Overpack AMP does not specify the extent (i.e., coverage area) of the examinations that will be performed for the accessible external and internal surfaces of the overpack. In addition, the staff noted that the Overpack AMP does not specify the examinations, including the extent, of the normally inaccessible surfaces/areas of the external and internal of the overpack. NUREG 2214 provides guidance associated with the aging management activities and inspections to be performed on the on the overpack.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Overpack AMP of the renewal application has been revised to include extent of the examination that will be performed on normally accessible and inaccessible surfaces of the overpack.

Per the updated Overpack AMP, all normally accessible external and internal surfaces of the overpack shall be visually inspected. Any inaccessible surfaces like container baseplate and cask bottoms shall be inspected if the ISFSI pad surrounding the cask shows any evidence of corrosion or degradation. Thus, the updated Overpack AMP provides an adequate aging management of the overpack.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Overpack and Transfer Cask AMPs RAI#2: Revise the Overpack AMP and Transfer Cask AMP to provide specific, actionable acceptance criteria against which the need for corrective actions will be evaluated.

The acceptance criteria for the Overpack AMP incorporates qualitative acceptance criteria (i.e., minor rust spots or indications). In addition, the acceptance criteria for the Transfer Cask AMP, in some instances, incorporates qualitative acceptance criteria (i.e., (1) All lid surfaces shall be relatively free of dents, scratches, gouges, or other damage, and (2) Lifting trunnions shall be free of deformation, cracks, damage, corrosion, and excessive galling); however, the staff noted that, when using qualitative criteria, they should be sufficiently clear to reasonably ensure that a singular decision is derived based on the observed condition, avoiding the use of ambiguous phrases (e.g., minor, significant, moderate). NUREG 1927, Revision 1, Section 3.6.1.6 notes that the AMP acceptance criteria should be achievable and actionable and avoid the use of nonquantifiable terms, and Appendix A notes that nonquantifiable terms used in reference to aging effects should be replaced by either quantitative information, if available, or further described or defined. NEI 1403, Revision 2, states:

If the AMP implementation procedures do not include actionable acceptance criteria, the subjective criteria for personnel to determine additional assessment or evaluation of a finding is required via the corrective action program should be sufficiently conservative to ensure virtually any unexpected finding is reviewed further.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

In accordance with the guidance given in NUREG1927 and NUREG2214, Overpack AMP and Transfer Cask AMP of the renewal application were revised to remove any nonquantifiable or ambiguous terms and include the specific actionable acceptance criteria for evaluation of corrective actions.

HITRAC AMP RAI #1: Provide clarifying information on how several HITRAC SSCs will be managed for aging.

The staff identified several aspects of the HITRAC AMP that require clarifying information in order to complete its review of the aging management approach for the transfer cask, as follows:

1. Clarify if the external surfaces monitored by the AMP include the entirety of the inside cavity of the transfer cask exposed to air (e.g., inner shell). If not, state how the AMP manages the aging of those SSCs.

2. If applicable (based on the response to RAI 34), state how the AMP manages the inaccessible portions of the transfer cask that are continuously or intermittently exposed to the liquid neutron shield.

3. In the Detection of Aging Effect program element, clarify if the program manages for trunnion wear, as indicated in Table 3.34 of the renewal application. This AMP element states only that the program manages for corrosion.

4. State how visual inspection parameters will be controlled to ensure that there is sufficient resolution and lighting. Given that the AMP does not use consensus code criteria that may have Page 20 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 such detail, describe either site operation practices or AMPspecific requirements that will be used to establish resolution and lighting requirements for the HITRAC inspections.

Program element 3, Parameters monitored/inspected of the Transfer Cask AMP states that the parameter inspected by the Transfer Cask AMP is visual evidence of degradation of external surfaces of the Transfer Cask and trunnions (emphasis added). In addition, program element 4, Detection of Aging Effects of the Transfer Cask AMP indicates that the program manages loss of material due to corrosion, predominately for coated steel components; however, the staff noted that the lifting trunnions may be subject to loss of material due to wear.

Table 66, Example Aging Management Program for Transfer Casks of the MAPS Report indicate that the program should monitor the condition of internal and external steel surfaces to identify general, pitting, crevice, and galvanic corrosion, and wear and that all transfer casks are to be inspected.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Responses to all the individual comments are provided below. In accordance with Table 66 of NUREG 2214 and Table 3.34 of the renewal applications, the following changes were made to the HITRAC AMP.

1. AMP was updated to include the interior cavity of the cask which will be monitored by the AMP.

2. Inspection of inaccessible areas of the transfer cask that are continuously or intermittently exposed to the liquid neutron shield, were included in the AMP.

3. Wear was included as an aging mechanism for lifting trunnions.

4. The AMP was updated to include the ASME requirements for visual inspection of accessible and nonaccessible areas of the transfer cask. The referenced ASME requirements provide details of lighting and resolution required during visual inspection.

High Burnup Fuel Assembly AMP RAI #1: Clarify what is meant by acceptable moisture content as described in the acceptance criteria for the High Burnup Fuel Assembly AMP. Provide a justification that this acceptance criteria is adequate for aging management of components within the scope of this program.

Program element 6, Acceptance Criteria of the High Burnup Fuel Assembly AMP states Moisture content - the moisture content in the canister (accounting for measurement uncertainty) should be determined to be acceptable.

Table 67, Example Aging Management Program for HighBurnup Fuel Monitoring and Assessment, of NUREG2214, Managing Aging Processes In Storage (MAPS) Report, indicates that the moisture content in the cask/canister, accounting for measurement uncertainty, should be less than the expected upperbound moisture content per the designbases drying process. It further states if the designbases drying process involves a vacuum drying method of evacuating a cask/canister to less than or equal to 3 torr and maintaining a constant pressure for 30 minutes after the cask/canister is isolated from the vacuum pump, the expected water content is about 0.43 grammole. The acceptance criteria for the High Burnup Fuel Assembly AMP related to moisture content is not clear and does not define what is considered acceptable.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Using the guidance given in Table 67 of NUREG2214, the moisture content acceptance criteria has been updated for the High Burnup Fuel Assembly AMP in the renewal application.

100U Concrete AMP RAI #1: (1) Provide a justification that groundwater chemistry monitoring of the 100U Concrete AMP can directly manage concrete degradation. Otherwise, revise the renewal application and clarify the purpose of the groundwater chemistry monitoring of the 100U Concrete AMP. (2) Provide and justify the acceptance criteria that will be used by the 100U Concrete AMP to determine whether the groundwater chemistry is aggressive, which may warrant corrective actions such as increased groundwater monitoring.

Program element 3, Parameters Monitored/Inspected, of the 100U Concrete AMP states for inaccessible areas, groundwater monitoring is performed every 5 years for evidence of concrete degradation. Program element 4, Detection of Aging Effects, of the 100U Concrete AMP states

[g]roundwater monitoring performed every 5 years will determine if any degradation of the system from inaccessible areas is occurring. Based on the description in these program elements, it appears to the staff that the 100U Concrete AMP is relying directly on groundwater monitoring to identify concrete degradation. Rather, the staff noted that the purpose of the groundwater chemistry monitoring is to identify conditions (i.e., aggressive environment) that is conducive to belowgrade (underground) aging mechanisms. Thus, it is not clear how the groundwater chemistry monitoring of the 100U Concrete AMP directly manages concrete degradation.

Program element 6, Acceptance Criteria of the 100U Concrete AMP states [a]ny groundwater indications of concrete degradation will be entered into the corrective action program. However, the staff noted that the applicant did not specify the criteria that will be used to determine whether the groundwater chemistry is considered aggressive and may warrant correctives actions, such as increased groundwater chemistry monitoring or other remedial steps. The staff also noted that NUREG2214 provides guidance for establishing acceptance criteria for groundwater chemistry monitoring.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

In accordance with the guidance provided in Table 63 of NUREG2214, 100U Concrete AMP of the renewal application has been revised to include the purpose of groundwater chemistry program and an acceptance criteria to determine whether groundwater chemistry is aggressive.

100U Concrete AMP RAI #2: Clarify whether the HISTORM 100 Underground System includes inspections of the inaccessible areas of the pad consistent with ACI 349.3R. If not, provide justification that this ACI code activity is not needed to manage the aging of the inaccessible surfaces.

Program Element 4, Detection of Aging Effects, of the 100U Concrete AMP states that the visual inspection is conducted annually by an individual meeting the qualification requirements of per ACI349, and includes all accessible areas on the pad. However, the renewal application did not address inspection coverage of the inaccessible areas of the pad.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 ACI 349.3R18, Report on Evaluation and Repair of Existing Nuclear SafetyRelated Concrete Structures, Chapter 6, Evaluation Frequency, indicates that, for structures with nonaggressive exposures, representative samples of belowgrade concrete be examined when excavated for any reason. Section 3.4 of ACI 349.3R states that the combination of soil/groundwater chemistry monitoring and opportunistic inspections of belowgrade concrete can verify that periodic inspections of accessible abovegrade structures can serve as a leading indicator of degradation.

Without opportunistic inspections of belowgrade concrete, it is unclear to the staff that the periodic AMP inspections of accessible concrete can be a leading indicator of belowgrade conditions.

This information is needed to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

In accordance with the guidance given in NUREG2214 and ACI 349.3R02, 100U Concrete AMP of the renewal application has been updated to include inspection of the inaccessible areas of the pad and cask.

RAI D1: Update the proposed FSAR supplement in Appendix D of the renewal application to include the following information:

1. Provide a summary of the TLAAs for Neutron Absorber Depletion and MPC Fatigue. The renewal application indicates that repeated lifting of the MPC may lower its fatigue life and that an analysis was performed to determine the allowable number of lifting cycles of the MPC over the 60year renewal period. In addition, the renewal application indicates that the original analysis for boron depletion was reperformed to support the 60year renewal period. These assessments are not adequately reflected in the proposed FSAR supplement in Appendix D of the renewal application.

2. Provide clear references to sections of the renewal application that are mentioned in the AMP summaries in the proposed Tables 9.A.11 through 9.A.15 of the FSAR supplement. The AMP summaries contain references to the renewal application that are not included in the proposed FSAR supplement. For example, Table 9.A.11 (MPC AMP), Element 1 (Scope of Program) notes, This program covers MPCs stored under the HISTORM 100 CoC, and the subcomponents identified in Table 3.31. However, Table 3.31 of the renewal application (Aging Management Review of MPC Enclosure Vessel Subcomponents) is not included in the FSAR supplement.

Therefore, the applicant should either include Table 3.31 of the renewal application in the FSAR supplement or include a clear reference to the renewal application Table 3.31 in the FSAR supplement.

3. Provide a clear timeframe for implementation of AMPs provided in Table 9.A.11 (MPC AMP) and Table 9.A.12 (Overpack AMP). For example, Table 9A.11 (MPC AMP), Element 4 (Detection of Aging Effects) notes that the first inspection should occur within 365 days of the 20th anniversary of initial overpack loading at the site or within 365 days of the issuance of the renewed license, whichever is later (emphasis added). Since of can indicate a time before or after the occurrence (of the anniversary of loading or issuance of the renewal), the timeframe for implementation is not clear. The AMP summaries in the FSAR should be clear in terms of the time before or after the occurrence for implementation by the general licensees.

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HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 Appendix D of the renewal application provides proposed FSAR change pages (FSAR supplement) to document the aging management information associated with the CoC renewal, per 10 CFR 72.240(c).

The CoC renewal will include a condition for the CoC holder to update the FSAR to reflect the changes and commitments resulting from the review and approval of the CoC renewal. The FSAR must clearly reflect the approved design bases, including aging management information in the period of extended operation if the renewal is approved. Therefore, the FSAR supplement in Appendix D of the renewal application must include all FSAR changes related to the renewal of the CoC.

This information is required to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

1) Information regarding the TLAAs has been added to the FSAR Appendix 9.A , and is highlighted for the staffs convenience.

2) Clear references to the renewal application have been added throughout the FSAR Appendix 9.A, and highlighted for the staffs convenience

3) The wording was chosen to provide an acceptable level of flexibility to the general licensees. If a site performs an inspection in accordance with the AMPs shortly before their anniversary of loading, this inspection should still be acceptable for meeting the AMP requirement. For planning purposes, the site may choose to do the inspection either before or after the exact date of the anniversary, and it is believed that there is no technical reason that either before or after is more appropriate. For those general licensees who will be in timely renewal and will be past the anniversary of their first loading, the AMP inspection will need to occur within 365 days after issuance of the CoC, so this has been updated.

RAI E1: Revise the proposed CoC condition #13 and the proposed TS 5.8/5.4 in Appendix E of the renewal application to include a clear timeframe for implementation by the CoC holder and general licensees. In addition, consider revising the proposed TS 5.8/5.4 to include a reference to the written evaluations required by 10 CFR 72.212(b).

Appendix E of the renewal application includes proposed CoC condition #13 for the CoC holder to submit an updated FSAR within 90 days of the effective date of the renewal (emphasis added).

Appendix E of the renewal application also includes proposed TS 5.8/5.4, Aging Management Program for general licensees to establish procedures for AMP implementation within 365 days of the effective date of the renewal of the CoC or 365 days of the 20th anniversary of the loading of the first dry storage system at its site, whichever is later (emphasis added). Since of can indicate a time before or after the occurrence (of the effective date of the renewal or the anniversary of loading), the timeframe for implementation is not clear. The conditions and TS should be clear in terms of the time before or after the occurrence for implementation by the CoC holder and general licensees. For example, within 90 days after the effective date of the renewal of the CoC.

Additionally, Appendix E of the renewal application includes proposed CoC condition #14 for general licensees to include in their written evaluations required by § 72.212(b), the new CoC terms, conditions, and specifications resulting from the CoC renewal (e.g., AMPs). The regulations in § 72.212(b) require, in part, that the written evaluations be performed before use and before applying the changes authorized by an amended CoC. Also, the specific regulation in 10 CFR 72.212(b)(11) requires general licensees to Page 24 of 25

HISTORM 100 CoC Renewal Responses to Requests for Additional Information Attachment 2 to Holtec Letter 5014911 comply with the CoC, including where the licensee has applied the changes of an amended CoC, which includes the requirements of AMPs put into effect as conditions of a renewed CoC. Therefore, pursuant to the regulations in § 72.212(b), general licensees are required to perform written evaluations before implementing the AMPs in a renewed CoC. Thus, the proposed condition #14 may not be necessary to include in the renewed CoC.

Furthermore, regarding timing of the § 72.212(b) written evaluations and the development of AMP implementing procedures, previous experience has shown that a general licensee would likely revise its

§ 72.212(b) evaluation report concurrent with its development of the AMP implementing procedures.

Therefore, as stated above, consider revising the proposed TS 5.8/5.4 to include a reference to the § 72.212(b) written evaluations to clarify for a general licensee that implementation and timing for the proposed TS 5.8/5.4 also includes the requirements in § 72.212(b).

This information is required to demonstrate compliance with 10 CFR 72.240(c).

Holtec Response:

Similar to RAI D1, the statements for general licensees to establish procedures within 365 days of the anniversary were intentionally chosen to give flexibility to the users. If a site were to establish procedures before actually crossing their 20th anniversary date, that should be acceptable under the CoC. For the conforming FSAR changes and for sites that have already crossed the 20th anniversary, these implementations will only take place after the issuance of the renewed CoC, so those locations have been modified, and are highlighted for staffs review.

Regarding the 72.212 written evaluations, Holtecs understanding is that the requirements of condition 14 and TS 5.4/5.8 are for two different steps in the process. The Condition 14 requirements are for simple compliance with the renewed CoC. When the NRC issues the renewed CoC, all users will have to update the 72.212 report to ensure they are referencing the renewed CoC, which supersedes the existing approved CoC, regardless of when that system was loaded. If this step is not performed, the site may be out of compliance with 72.214. The requirement in TS 5.4/5.8 was intended to cover the actual development of procedures and evaluations of the aging management program, which need to be implemented before the site enters the period of extended storage, but not necessarily at the same time that the renewed license is issued. It is believed that both steps are necessary to ensure general licensee compliance throughout the various scenarios which may apply.

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