ML20326A008

Attachment 2 - Response to Requests for Additional Information Part 6

ML20326A008
Person / Time
Site:	HI-STORE
Issue date:	11/20/2020
From:	Holtec
To:	Office of Nuclear Material Safety and Safeguards
Shared Package
ML20326A005	List: ML20326A006 ML20326A008 ML20326A009
References
5025061
Download: ML20326A008 (50)

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HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 17: Clarify the distance between the ISFSI and the controlled area boundary and revise the calculation for the dose at the controlled area boundary and the dose rate versus distance, as necessary.

Table 1.0.1 of the HISTORE SAR states that the distance from the nearest loaded UMAX VVM to the controlled area boundary is 400 meters. However, Section 7.4.2.1 of the SAR also states that: []The nearest residence is 1.5 miles from the HISTORE CIS Facility. The dose calculations conservatively assume a fulltime resident (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />s/year) is only 1000 meters from the nearest loaded HISTORM UMAX VVM. In the case of this nearest residence, the dose is calculated to be below the 25 mrem annual dose limit prescribed in 10 CFR 72.104. From these statements, the staff is unable to verify the calculated controlled area boundary dose as presented in Table 7.4.3 of the SAR because it is not clear whether the controlled area boundary is 400 meters or 1000 meters.

This information is needed to determine compliance with 10 CFR 20.1301(a)(1), 10 CFR 72.104 and 72.106.

Holtec Response:

The controlled area boundary is shown in the site layout drawing 10940, and the distance is indicated in Table 1.0.1 as a minimum of 400 meters from the nearest UMAX VVM. 10 CFR 72.104 provides a criterion for normal operations for the annual dose equivalent to any real individual who is located beyond the controlled area. Updated total annual dose at the controlled area boundary is provided in Table 7.4.7.

Another set of assumptions is used for a real individual at the nearest residence beyond the controlled area boundary, assuming the nearest home is 1000 meters from the nearest HISTORE radiation source.

Currently, the nearest home is 1.5 miles from the HISTORE CIS Facility, so this assumption of 1000 meters to the nearest residence, with full time occupancy (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />s/year) is conservative. Annual dose for a real individual at the nearest residence is provided in Table 7.4.8.

RAI 51: Provide a basis for how the seismic analysis for stackup, with respect to the UMAX location, is the bounding case as compared to the cask transfer facility (CTF) location. Include a response spectrum and/or supporting calculations demonstrating that the dynamic behavior of the UMAX is bounding for both forces and displacements and update any results/tables as necessary.

Section 2.0 of Supplement 5 to Holtec Report No. HI2177585, Structural Calculation Package for HI STORE CIS Facility, states:

[] Therefore, the only differences between stackup at the CTF and UMAX locations is the free length (i.e. unthreaded length) of the anchor bolts (approximately 4.5 inches and 13.5 inches, respectively). The longer free length of the bolts will introduce more flexibility into the system and potentially larger rocking displacements and loads in the stack. Hence, stackup at the UMAX location is considered bounding and the bolted connection points between the CEC and HT are included in the model []

It is not clear how a more flexible system due to longer bolts would be bounding in terms of loading or displacements, since the response of the structure is dependent on the response spectrum of the site.

That is, a stiffer structure may observe larger demands on certain components than a flexible system

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 and viceversa, given the characteristics of the site described by the response spectrum, which has not been provided.

This information is necessary to determine compliance with 10 CFR 72.92, and 72.103(a)(2).

Holtec Response:

The stackup at the UMAX ISFSI pad is the limiting configuration for seismic response analysis, as compared to the stackup at the CTF, because (a) both locations are subject to the same design basis seismic motion and (b) the rocking frequency of the stackup at the UMAX ISFSI pad is less than the rocking frequency of the stackup at the CTF (owing to the longer bolt length associated with the former configuration), which means that the stackup at the UMAX ISFSI pad is subject to higher spectral accelerations and therefore higher demand loads. This is further explained below.

The design basis seismic events for the HISTORE CIS Facility, which includes the HISTORM UMAX ISFSI and the CTF inside the Cask Transfer Building, are defined in Table 4.3.3 of the HISTORE SAR. As discussed in SAR Section 4.3.6, the stackup configuration is a ShortTerm Operation, and therefore it is only required to be analyzed for OBE loading. However, for conservatism the stackup analysis performed in Supplement 5 to HI2177585, and also discussed in SAR Section 5.4.1.4, considers the Design Extended Condition Earthquake (DECE) as input. Per SAR Table 4.3.3, the DECE is defined as a RG 1.60 earthquake having a ZPA value of 0.25g in all three orthogonal directions (2 horizontal and 1 vertical). In summary, there is no difference between the two stackup locations with respect to the design basis seismic motion, and a bounding earthquake (DECE) is used as input to the seismic analysis for stackup.

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PROPRIETARY INFORMATION WITHHELD PER 10CFR2390

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For the reasons above, the seismic analysis of the stackup at the UMAX ISFSI pad bounds the seismic response of the stackup at the CTF.

RAI 52: Verify the density values for the materials used in the LSDYNA model, used for stack up to simulate the Design Extended Condition Earthquake (DECE) event. Update and submit any results/calculations as necessary.

According to the licensing drawings (DWG 10865), BOM 9 is made of ASTM A516 Grade 70, which typically has a mass density of around 7.280e004 slugs/in^3, but is reported as 9.330e004 slugs/in^3 in LSDYNA simulations. Higher density values for materials could lead to erroneous results, as the response of the structure may be significantly altered.

This information is necessary to determine compliance with 10 CFR 72.92 and 72.122(b)(2)(i).

Holtec Response:

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The density of the shield gate top plate is intentionally increased to account for the weight of miscellaneous shield gate components (e.g., the hydraulic actuating system) not explicitly modeled in the stackup analysis LSDYNA model in Supplement 5 of HI2177585. Since those miscellaneous components are all located below the shield gate top plate, including their weight at the top plate conservatively increases the overall center of gravity of the stackup for the seismic analysis. Therefore, it is not required to update the analyses as the current ones remain conservatively bounding.

RAI 53: Justify the claim that the weight used to model the HITRAC CS in LSDYNA is conservative with respect to seismic demands. Include a discussion of when the HITRAC CS is fully loaded versus partially loaded. Update, as needed, any seismic calculations related to the simulation of the HITRAC CS using LSDYNA.

Page 117 of Holtec Report No. HI2177585, Structural Calculation Package for HISTORE CIS Facility claims that a weight of 380,000 lbs for the HITRAC CS is conservative with respect to seismic analysis.

However, this claim is not justified given that a higher weight may not necessarily indicate a more severe seismic response depending on the response spectrum that typifies the site, which has not been provided. That is, a partially loaded MPC may produce higher demands on certain components of the HI TRAC CS depending on the response spectrum of the site and dynamic behavior of the HITRAC CS.

This information is necessary to determine compliance with 10 CFR 72.92 and 72.122(b)(2)(i).

Holtec Response:

Designed to have a very stiff structure, the HITRAC CS cask itself will behave like a rigid body (i.e., with a natural frequency above 33 Hz.) in a seismic event. However, the smallest natural frequency of the anchored HITRAC CS stackup system is controlled by the relatively flexible anchoring bolts. Using the bounding cask weight in the seismic analysis can capture the lowerbound natural frequency of the system. Because the seismic response of the RG. 1.60 earthquake reduces with the increase of frequency after 2.5 Hz, it is conservative to use the upper bound cask weight in the seismic analysis of the HITRAC CS stackup system whose minimum natural frequency is shown in the following calculation to be 19.0 Hz.

A partially loaded MPC would increase the natural frequency of the stackup system and therefore reduce the seismic response of the stackup. In summary, using the bounding weight is conservative. Unless noted, all the input data used in the following natural frequency calculation is taken from Holtec Report No. HI2177585R0 and Holtec Drawing No. 10868R0.

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HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 PROPRIETARY INFORMATION WITHHELD PER 10CFR2.390

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RAI 54: Define the duration of a work shift as it pertains to seismic qualification.

Section 4.3.6 of the HISTORE SAR states, in part:

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Following the universally practiced lift and set rule at nuclear power plants, transient activities such as upending of a cask, attaching of slings or installation of fasteners, are treated as transient activities that are not subject to a seismic qualification. For clarity of application, any activity that spans less than a work shift is deemed to be seismicexempt.

Since seismic qualification of important handling operations, such as cask upending, attaching of slings, or installation of fasteners, which may include important to safety components, is not performed based on a work shift, a work shift should be clearly defined.

This information is necessary to determine compliance with 10 CFR 72.122(b)(2)(i).

Holtec Response:

The term work shift has been added to the Glossary in the HISTORE SAR and given the following definition:

Work Shift is any continuous 8hour time interval during which work is carried out at HISTORE CIS Facility.

RAI 55: Describe the condition of the loaded HITRAC CS when carried by the vertical cask transporter and transiting or performing downloading operations from the cask transfer building to a designated ventilated vertical module while subjected to a tornado or lightning strike.

Section 5.5.2 of the SAR describes the scenario where the vertical cask transporter and related equipment is carrying the HITRAC CS under seismic loading. However, it is unclear how the same system responds to a lightning strike or tornado while traveling to the ventilated vertical module and performing downloading operations. Provide justification and/or supplemental calculations and update the SAR, as necessary, showing that the transported canister will not be breached by a missile strike or a tip over of the vertical cask transporter. If the tip over scenario is credible, the structural, shielding, thermal, and confinement analyses should be updated to consider the damage from that event.

This information is necessary to determine compliance with 10 CFR 72.92 and 72.106.

Holtec Response:

The calculations performed in Supplement No. 2 to HI2177585 demonstrate that a freestanding HI TRAC CS, completely independent from the vertical cask transporter (VCT), will not tipover as a result of the design basis tornado wind and missile impact. The calculations also show that the HITRAC CS adequately protects the MPC against penetrant missiles due to a tornado event.

When the HITRAC CS is being carried by the VCT, the aspect ratio (i.e., ratio of c.g. height to minimum base dimension) decreases significantly, which enhances stability. The physical presence of the VCT also serves as an additional barrier against missile impact on the HITRAC CS. In summary, the tornado wind and missile evaluations for the freestanding HITRAC CS, which are documented in Supplement No. 2 to HI2177585, are bounding for the VCT carrying a loaded HITRAC CS.

Regarding a lightning strike, the HITRAC CS contains over 75,000 lb of highly conductive carbon steel with over 600 square feet of external surface area. Such a large surface area and metal mass is adequate

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 to dissipate any lightning that may strike the HITRAC CS. There are no combustible materials on the HI TRAC CS surface. Therefore, lightning will not impair the structural performance of the HITRAC CS. A lightning strike on the VCT could cause an electrical system failure preventing further transit of the HI TRAC CS, but a load drop of the HITRAC CS from the VCT would not result since the VCT has redundant drop protection features.

RAI 56: Confirm the values provided in Table 5.4.8 of the HISTORE SAR, as needed, for the type of material used in the lifting trunnions of the HITRAC CS.

Table 5.4.8 of the HISTORE SAR indicates that the maximum number of fatigue cycles for the lifting trunnions is 7,500 for SB637 N07718 material. It appears that SA564 Gr. 630 H1100 material was intended to be described instead.

This information is necessary to determine compliance with 10 CFR 72.122(b).

Holtec Response:

The values in Table 5.4.8 are correct. However, there was a typographical error associated with one of the item descriptions. As noted in the above RAI, the item description corresponding to 7,500 cycles was previously listed incorrectly as Lifting Trunnions (SB637 N07718). Consistent with the fatigue evaluations documented in Supplement 10 of Holtec Report No. HI2177585, the lifting trunnion material that corresponds to a maximum of 7,500 loading cycles is SA564 Gr. 630 H1100. Table 5.4.8 of the HISTORE SAR has been revised accordingly to correct the item description, so that it now appears as Lifting Trunnions (SA564 Gr. 630 H1100).

RAI 57: Confirm the weight of the HISTAR 190 transportation package to be lifted by the horizontal lift beam.

According to Supplement 9 to Holtec Report No. HI2177585, the maximum weight of the MPC to be lifted by the horizontal lift beam is 110 kips; however, the HISTAR 190 FSAR, Revision 0C (Document No.

HI2146214) indicates that the maximum weight of the MPC is 116,400 lbs Confirm the actual weight to be lifted, and revise any calculations related to the design of the horizontal lift beam.

This information is necessary to determine compliance with 10 CFR 72.122(b).

Holtec Response:

The maximum weight of the HISTAR 190 transportation package used in Supplement 9 of Holtec Report No. HI2177585 is confirmed to be valid and correct. In particular, the maximum MPC weight of 110 kips used as input in Supplement 9 is correct since it accords with the maximum loaded MPC weight per Table 3.2.1 of the HISTORM UMAX FSAR. While it is true that a HISTAR 190 transport cask can transport a MPC37 that weighs as much as 116,400 pounds, such an MPC cannot be stored at the HI STORE CISF Facility since it would not satisfy with the design basis requirements of the HISTORM UMAX FSAR and CoC, which limit the maximum MPC weight to 110 kips. Therefore, since a MPC weighing more than 110 kips cannot be accepted for storage at the HISTORE CISF Facility, there is no need to analyze the horizontal lift beam for a higher load. That being said Supplement 9 of Holtec Report No. HI 2177585 qualifies the horizontal lift beam for a total lifted load of 418 kips, including HISTAR 190 cask,

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 impact limiters, loaded MPC, and miscellaneous rigging, and determines that the lifting device has a minimum safety factor of 1.283 (or 28.3% margin) over and above NURE0612 and ANSI N14.6 requirements. This means that, although it is not permissible from a design and licensing standpoint, the horizontal lift beam is capable of carrying significantly more weight (i.e., an additional 100 kips) without exceeding its design stress limits.

RAI 58: Provide a basis for the assumption that the vertical cask transporter (VCT) is essentially a rigid body when transporting a loaded HITRAC CS and how the use of the peak ground acceleration (PGA) alone, for calculations involving tipping and sliding, is conservative. Confirm the rigid body nature of the system, incorporate the response spectrum of the site based on the actual dynamic behavior of the system, and update the calculations used to determine tipping and sliding. 1 to Report No. HI2177585, Rev. 0, details the calculations used to determine the amount of sliding and tipping that the loaded VCT may experience. The methodology used from ASCE Standard 4305 assumes that while carrying the HITRAC CS, the VCT is a rigid body. Two concerns related to the assumption that the system is a rigid body are:

1. The fundamental period of the VCT has not been provided. When empty, the VCT weighs approximately 210,000 lbs and weighs an additional 375,000 lbs when carrying a fully loaded HI TRAC CS. The loaded VCT is expected to have a fundamental period that is 67% larger relative to the unloaded VCT, which could allow the fully loaded VCT to experience larger seismic demands.

The demand is unclear as the response spectrum of the site has not been provided.

2. The VCT, while carrying the HITRAC CS, appears to have at least 2 dominant periods given that the MPC can sway independently from VCT during an earthquake. This would violate the rigid body assumption of ASCE Standard 4305.

Accordingly, the use of the PGA for sliding and tip over calculations is questionable since its use was intended for rigid bodies. In addition, clarify how the use of the PGA is conservative for calculation purposes since its magnitude relative to the response spectrum of the site is unclear.

This information is necessary to determine compliance with 10 CFR 72.122(b)(2)(i).

Holtec Response:

The HITRAC CS is physically secured against the chassis of the VCT using a tensioned restraint strap while it is in transit. This prevents the HITRAC CS from swaying with respect to the VCT. Also, by bracing the HITRAC CS against the VCT, the flexible beam modes associated with the VCT lift towers are diminished since the massive HITRAC CS is restrained against lateral motion (relative to VCT). The VCT chassis is a large welded steel structure with a substantial crosssection, which behaves like a rigid body under seismic loading.

The design basis ground response spectra for the site are specified in SAR Table 4.3.3. The OBE, DBE, and DECE spectra are all RG 1.60 spectra with ZPA values of 0.10g, 0.15g, and 0.25g, respectively. Per Subsection 4.3.6 of the SAR, OBE applies to the ShortTerm Operations required to load the arriving canisters at HISTORE, including transit of the HITRAC CS using the VCT. Supplement 6 to HI2177585,

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 however, conservatively considers the most severe DECE as input to the seismic stability analysis of the VCT. Based on the shape of the RG 1.60 spectra, the input acceleration of 0.25g (based on DECE) is equivalent to a response frequency between 12Hz and 14Hz with respect to the OBE response spectra.

Therefore, the seismic stability analysis performed for the VCT in Supplement 6 to HI2177585 remains bounding even if the VCT is slightly nonrigid.

59: Justify the impact loads on the HITRAC CS transfer cask due to collapse of the cask transfer building (CTB) and/or provide additional justification that the scenario where the impact from the W40 x 324 beam is the bounding accident scenario for a building collapse.

The cask transfer building (CTB) has been classified as not important to safety. Its collapse onto the HI TRAC CS transfer cask and HISTAR 190 transportation package has been postulated as an accident scenario and detailed in Report No. HI2177585 R0. In the structural calculation package, it is assumed that a W40 x 324 beam from the building strikes either the HISTAR 190 package or the HITRAC CS transfer cask, which was simulated using LSDYNA. However, the application does not provide detailed drawings or details of the CTB, so it is not possible to confirm if the loading that the HITRAC CS transfer cask or HISTAR 190 transportation package would experience as a result of building collapse is bounding. Its possible that a smaller object, such as a pipe driven by heavy load behind it or some other object, may be a more damaging scenario than the collapse of a beam onto the system.

This information is necessary to determine compliance with 10 CFR 72.122(b)(2)(ii).

Holtec Response:

The safety classification for the Cask Transfer Building (CTB) has been revised from not important to safety (NITS) to ITSC, which is now reflected in SAR Table 4.2.1 and throughout the HISTORE SAR. As a result, the CTB will be designed to withstand the applicable wind and seismic loads at the site, which will preclude a building collapse as a credible event. Although the SAR has been updated to eliminate the CTB collapse as a credible event, the postulated impact scenarios analyzed in Supplement 14 to HI 2177585 using LSDYNA remain part of the calculation package for defenseindepth.

510: Confirm the fatigue life of the HITRAC CS, vertical cask transporter (VCT), and associated lifting ancillaries and relate it to anticipated canister deployments. Update fatigue calculations with both high and low stress cycle information and relate it to canister deployments so that the VCT, HITRAC CS, and lifting ancillaries can be adequately maintained and operated in a safe manner.

Holtec Report No. HI2177585 R0, Structural Calculation Package, provides calculated estimates of fatigue life for the HITRAC CS and associated lifting ancillaries, referred to as components for the purposes of this RAI. The report estimates the number of fatigue cycles a component of the HITRAC CS and associated lifting ancillaries may observe based on the maximum bounding allowable stress the component may experience during its lifetime. While fatigue cycles based on maximum stress of this nature are useful, they dont capture the complete fatigue life of the component since low stress, high cycles observed during handling and movement by the VCT have been ignored. In addition, calculated fatigue cycles have not been linked to a periodic inspection, maintenance, repair, or replacement of the VCT, HITRAC CS, lifting ancillaries etc. Fatigue life should relate to the number of canister deployments or some other measure, where a canister deployment is defined for purposes of

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 discussion as the movement of a canister upon initial receipt from rail car to its ventilated vertical module (VVM) location, or from the VVM back to the rail car.

For a given canister deployment, the HITRAC CS, VCT, and associated lifting ancillaries will observe a combination of high stress and low stress cycles, which should be combined to calculate the fatigue life of the component via a cumulative damage model such as Miners rule. High stress cycles are expected during lifting operations while low stress cycles are expected when being handled by the VCT as it travels from the rail car to the VVM. The number of low stress cycles and stress itself will depend on the vibrational characteristics of the VCT while carrying the HITRAC CS, the weight of the canister being moved, the distance the HITRAC CS is carried (which depends on the VVM location), etc.

This information is necessary to determine compliance with 10 CFR 72.122(b).

Holtec Response:

Supplement 10 to HI2177585 will be revised to address low stress cycles for the various lifting equipment and correlate the resulting fatigue life to a number of canister deployments.

515: Provide an explanation and justification for the excessive amounts of hour glassing energy observed during seismic simulations during stackup analysis. Update the model and any results in the HISTORE SAR, as necessary.

Comparison of hour glassing energy to internal energy for the Design Extend Condition Earthquake (DECE) seismic simulation of the CS Stackup analysis at the CTF and UMAX (via LSDYNA) reaches 16%

during the simulation, indicating that the model is potentially exhibiting unrealistic behavior and likely leading to erroneous stress and strain output of the analyzed components. Similar behavior was also noted for the Safe Shutdown Earthquake (SSE) scenario.

This information is necessary to determine compliance with 10 CFR 72.24(c)(2) and 72.122(b)

Holtec Response:

The time histories of the total internal energy and the total hourglass energy of the DECE simulation are shown in the following plot (Figure 5151) which is reproduced from the LSDYNA analysis supporting Supplement 5 of HI2177585. Although the ratio of the hourglass energy to the internal energy is relatively large over a small duration (i.e., between 8.0 and 9.0 seconds), the magnitudes of the two types of energies are very small relative to the internal energies at other times during the simulation. As demonstrated in Figure 5152, where the total kinetic energy (i.e., seismic energy) of the stackup is plotted along with the total internal energy and the total hourglass energy, the hourglass energy is shown to be extremely small and can be considered as noise when compared with the kinetic energy of the stack up. The same behavior is observed in the SSE simulation. In conclusion, there is no need to update the analyses.

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HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 PROPRIETARY INFORMATION WITHHELD PER 10CFR2.390

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HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 516: Clarify how closure lid handling holes are designed. Provide supporting calculations and update the licensing drawings and HISTORE SAR, as necessary.

Note 7 on Sheet 1 of 6, Drawing No. 10875, states:

THE BOUNDING CLOSURE LID WEIGHT IS DEFINED IN TABLE 3.2.1 OF THE FSAR. CLOSURE LID HANDLING HOLES ARE DESIGNED TO MEET THE REQUIREMENTS OF TABLE 2.4.1 OF THE FSAR.

However, supporting calculations do not appear to have been provided for this ITS component.

This information is necessary to determine compliance with 10 CFR 72.24(c)(3) and 72.120(b).

Holtec Response:

The details of the closure lid handling holes are provided on Sheet 6 of Drawing No. 10875 (see Detail DD). The lifting evaluation for the HISTORM UMAX closure lid, including the handling holes, is discussed in Subsection 3.4.3.2 of the HISTORM UMAX FSAR [1.0.6]. Moreover, the results in Table 3.4.1 of [1.0.6]

demonstrate that the closure lid handling holes meet the requirements in Table 2.4.1 of [1.0.6] for Load Case I.D. 04 (i.e., Closure lid handling).

518: Clarify the drawing details of the cask transfer building (CTB) floor slab relative to the cask transfer facility (CTF) building and describe the structural stability of the shell liner of the CTF during stackup as depicted in that view. Interaction of lateral loads due to the vertical cask transporter and earth pressure in conjunction with the vertical loads from the loaded transfer cask and mating device should be considered simultaneously in the buckling analysis of the shell and the SAR should be updated, as needed.

Sheet 1 of 4, of Drawing No. 10895, depicts an isometric view of the CTF that does not appear to include the details of the cask transfer building floor slab shown on Sheet 2 of 2 of Drawing No. 10912.

Additionally, it is unclear if the fill surrounding ITS BOM part 1 (shell) on Sheet 1 of 4, of Drawing No.

10895 is earth or concrete as drawn.

Also, it appears that the shell (BOM 1) was not analyzed for the case that includes the lateral earth pressure exerted by the vertical cask transporter (VCT), which weighs 180,000 lbs (Table 3.2.1 of Chapter 3 of the UMAX FSAR) during stack up operations. It was noted that Calculation 8 for the CEC of the UMAX system (Attachment 12 to Holtec Letter 5025012) appears to be applicable to the shell; however, buckling of the shell is most likely to occur in the direction of the surrounding earth pressure, where the shell may buckle inwards in the ventilated vertical module cavity rather than outwards as assumed in 2.

This information is necessary to determine compliance with 10 CFR 72.24(c)(3) and 72.120(b).

Holtec Response:

The details of the floor slab relative to the building are not relevant to any analysis supporting Chapter 5 of the SAR. Per Holtec drawing No. 10912, the shell liner of the CTF is backed by CLSM, which is fairly stiff with a minimum compressive strength of 1200 psi and thus would not deform like soil to develop significant lateral earth pressure to the CTF shell under the weight of the crawler.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The isometric section view of the CTF does not show the details of the CLSM and floor slab in Holtec Drawing No. 10895, where the focus is the CTF design while the rest is simplified and included for the purpose of illustration. However, a note will be added to the Sheet 1 of the drawing for clarification.

The CTF shell liner is essentially identical to the UMAX CEC shell in terms of material and thickness but has a significantly enhanced buckling resistance due to the rigid connections between the shell and the vent pipes embedded in the surrounding CLSM and concrete floor slab. Calculation 8 in Attachment 12 to Holtec Letter 5025012 concludes that the UMAX CEC shell can take 400,000 lbf compressive load with a safety factor of almost 150. As noted previously, the CTF shell would not experience any significant lateral pressure from the stiff CLSM due to the 180,000 lbf crawler. Therefore, buckling of the CTF shell is not a realistic concern.

RAI 519: Clarify the material properties and their temperature dependency used for the lifting trunnions of the HITRAC CS, HITRAC CS lift links, and the MPC lift attachment.

Lifting trunnions (BOM 4) on Licensing Drawing 10868 are identified as being made of either SB637 N07718 or SA 564 H1100 Gr. 630. However, calculations in Holtec Report No. HI2177585 assume that the trunnions are only made of SA564 Gr. 630 H1100. The trunnions are assumed to sustain a temperature of 350°F, although in Holtec Report No. HI2177553 the concrete in which the trunnions are embedded is reported to sustain 642 deg. F, while Table 4.4.1 of the HISTORE SAR reports a concrete temperature of 572 deg. F for the HITRAC CS. According to Holtec Report No. HI2177585, the HITRAC CS lift links, which are in direct contact with the trunnions, are assumed to only reach 300 deg.

F and the MPC lift attachment is only assumed to observe 500 deg. F.

The SAR should verify that the most limiting material properties for the lifting trunnions has been used, that the correct temperature is being used for the lifting trunnions of the HITRAC CS, HITRAC CS lift links, and the MPC lift attachment, and that the calculations as updated or revised as necessary.

This information is necessary to determine compliance with 10 CFR 72.122(b).

Holtec Response:

The material properties and the metal temperatures used as input to the stress analyses for the HITRAC CS lifting trunnions, the HITRAC CS lift links, and the MPC lift attachment are valid and conservative for normal handling conditions. In particular, the following input data have been confirmed:

1) The stress analysis of the HITRAC CS lifting trunnions is based on the strength properties of SA 564 630 H100, which is the weaker of the two material options (i.e., SB637 N07718 and SA564 630 H1100) specified on Licensing Drawing 10868. From Supplement 1 to HI2177585, SA564 630 H100 has yield and ultimate strength values of 100 ksi and 138 ksi, respectively, at 350°F.

SB637 N07718 has yield and ultimate strength values of 139.5 ksi and 172 ksi, respectively, at 350°F per Table 3.3.4 of the HISTORM FW FSAR [1.3.7].

2) The permissible temperature limit for the shielding concrete in the HITRAC CS for shortterm operations is 300°F per Table 4.4.1 of the SAR. According to Note 1 to Table 4.4.1, shortterm operations include all activities in the CTB and at the ISFSI to effectuate canister transfer and

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 onsite translocation (e.g., lifting and handling of the HITRAC CS). In addition, the maximum calculated temperature of the HITRAC Concrete, during normal onsite transfer, is 271°F per Table A.7.1 of HI2177553. This validates the use of 350°F as a bounding metal temperature for the HITRAC CS lifting trunnions. The higher temperatures referenced in RAI 519, namely 572°F and 642°F, are associated with accident conditions, not shortterm operations (i.e., lifting and handling).

3) The HITRAC CS lift links are analyzed in Supplement 12 to HI2177585 based a bounding metal temperature of 300°F. This is conservative since it exceeds the calculated temperature (200°F) of the HITRAC outer shell per Table A.7.1 of HI2177553, and it matches the permissible temperature limit for the HITRAC CS concrete for shortterm operations.

4) The MPC lift attachment is analyzed in Supplement 7 to HI2177585 based a bounding metal temperature of 500°F. This is conservative since it exceeds the maximum calculated temperature of 482°F for the MPC closure lid as reported in Section 4.4 of the HISTORM UMAX FSAR [1.0.6]. It also exceeds the maximum calculated temperature of 495°F for the MPC lid while inside the HISTAR 190 at the CTF, as reported in Table 6.4.5 of the HISTORE SAR.

In summary, the material strength properties and the metal temperatures used to inform the stress analyses for the HITRAC CS lifting trunnions, the HITRAC CS lift links, and the MPC lift attachment are valid and supported by the thermal analysis results.

RAI 520: Specify the size of weld(s) 51, 52, 53, 54, 55, and 56 shown on Sheet 5 of Licensing Drawing 10868 used to construct the shield gate of the HITRAC CS.

The shield gate, identified as ITS, is made of multiple plates which supports the MPC during transfer operations. Calculations in Holtec Report No. HI2177585 assume these plates act in unison (composite action) with respect to bending thanks to these welds (51, 52, 53, 54, 55, and 56 ), which help ensure composite action when supporting the MPC as shown on Section 5A5A, Section 5B5B, and Detail 5D of Licensing Drawing 10868. However, the size of these welds is unspecified, and are expected to carry significant transverse shear stress, particularly at the neutral axis of the composite section. The SAR should clarify the size of these welds to ensure that composite action is ensured, or reevaluate the section as noncomposite, and the licensing drawings and calculations should be updated, as necessary.

This information is necessary to determine compliance with 10 CFR 72.24(c)(3) and 72.120(b).

Holtec Response:

The structural calculation of the shield gate, which is performed in Supplement 1 to Report HI2177585, only credits the bottom 3 minimum thick plate of the plate assembly, which is shown in Detail 5D. The upper three thinner plates are required for shielding purpose only, not for any actual structural need. The entire structure is classified as ITS as shown in the Bill of Material on Sheet 1 due to its combined structural and shielding safety functions. However, the welds mentioned in this RAI are not ITS welds although the plates are ITS items. Even if all those welds fail, all plates are still laterally constrained through inserts (BOM 18) and are expected to move together to maintain the function of the shield gate.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 521: Provide stressstrain curves based on material testing for SA516 Gr. 70 at 400 degrees F.

Supplement 5 to Report No. HI2177585 provides stressstrain curves with guessed material properties (n and k coefficients) for SA516 Gr. 70 at 400 deg. F, which is used in seismic simulations of the HITRAC CS. Material properties used in ITS equipment should be well defined and based on physical testing as seismic evaluations of ITS equipment cannot be verified otherwise. Seismic evaluations are only as good as the material properties that go into them, and the seismic response may be very different than observed when material properties are assumed arbitrarily.

This information is necessary to determine compliance with 10 CFR 72.24(c)(3) and 72.122(b)(2)(i)

Holtec Response:

The truestresstruestrain curve of material SA516 Gr. 70 is derived using Mathcad in Report HI2177585.

[

PROPRIETARY INFORMATION WITHHELD PER 10CFR2.390

] In addition, the minimum engineering strengths required by the ASME B&PV Code at 400F are conservatively used to develop the true stressstrain curve of the material. Therefore, there is no need to perform testing at 400F to experimentally obtain the true stressstrain curve for material SA516 Gr. 70.

RAI 522: Describe the margins of safety for the tilt frame and saddle with respect to buckling while supporting a transportation cask.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Calculations have been provided for the tilt frame and saddle, however, margins of safety that describe the buckling of web plates and beams (BOM 2, 7, 12) of the tilt frame and saddle have not been provided. Update the calculations as necessary.

This information is needed to ensure compliance with 10 CFR 72.122(b).

Holtec Response:

The structural calculation of the tilt frame and saddle, which is performed in Supplement 13 to Report HI 2177585, appropriately considers the buckling of the Wbeam (item 2 of Holtec Drawing 10899) and the beam side plate (item 7 of Holtec Drawing 10899). The Wbeam and the beam side plate of the tilt frame, hereafter referred to as boxed beam are evaluated for buckling (a.k.a compressive) loads in combination with the bending loads during the upending/downending operations. The combined compression and bending evaluation of the boxed beam is performed per the guidance in ASME NF Subsection NF3322.1(c) and (e). The limiting margin of safety against compression and bending for the boxed beam is 1.073 as listed on page 1325 of Supplement 13 to Report HI2177585.

The saddle web plates (item 12 of Holtec Drawing 10899) are 1 inch thick plates, which are well supported by the gusset plates (item 16, 17, and 21 of Holtec Drawing 10899) on either side. These gusset plates are placed at equal intervals over the full width of the web plates and are welded to the web plates over the entire height of the gusset plates. As a result, the buckling of the saddle web plate is not a credible failure mode and therefore has not been explicitly evaluated. Additionally, the vonMises stress plot for the saddle (shown in Figure 13.33 of Supplement 13 to Report HI2177585) also confirms that the stresses on the saddle web plates are negligible, and the saddle assembly is primarily subjected to bearing loads.

Notwithstanding the above, a critical buckling load for the saddle web plate is conservatively calculated below. The margin of safety against the conservatively estimated critical buckling load for the saddle web plates is greater than 2.0 as shown below.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061

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PROPRIETARY INFORMATION WITHHELD PER 10CFR2.390

]

RAI 523: Clarify the margins of safety for members of the Transport Cask Horizontal Lift Beam with respect to buckling when lifting a transportation cask, and how it will behave and interact with its surroundings during a seismic event.

Figure 3.1.1 of the HISTORE SAR depicts the Transport Cask Horizontal Lift Beam handling a transportation cask. From this depiction, and the calculations in Holtec Report No. HI2177585, it is unclear what the margins of safety are for BOM members 13, which are subjected to buckling loads due to the slings applying compressive loads. The SAR references an ANSYS evaluation that was provided in the application, but buckling checks have not been performed.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The orientation of the slings (cable pitch) can greatly influence the buckling load on these members and should be placed on the licensing drawings or technical specifications to avoid overloading these members and should correspond to what has been provided in the calculations.

In addition, it is unclear how the slings while attached to the Transport Cask Horizontal Lift Beam will behave when subjected to seismic loads and how the Transport Cask Horizontal Lift Beam will avoid hitting the crane and or building while in such a scenario. The SARs calculations and licensing drawings should be updated, as necessary.

This information is necessary to determine compliance with 10 CFR 72.24(c)(3) and 72.122(b)(2)(i).

Holtec Response:

The orientation of the slings when they are connected to the Transport Cask Horizontal Lift Beam is shown on Sheet 3 of Drawing No. 10894. The sling angles modeled in Supplement 9 to HI2177585 are consistent with those depicted on the drawing.

With regard to buckling loads, the fact that the Horizontal Lift Beam is designed to meet the increased safety factors per NUREG0612 and ANSI N14.6 insures that the compressive stresses in the lifting device will not cause a buckling failure. This conclusion is based on the following line of reasoning. Figure 5 in Supplement 9 to HI2177585 demonstrates that primary stresses in the Horizontal Lift Beam are less than onesixth of the material yield strength (i.e., Sy/6) under the maximum lifted load. This result can be compared against the allowable compressive stress for a lineartype support per NF3322.1(c)(1)(a) of the ASME Code,Section III, Subsection NF, which is expressed as:

1 2 53 3 8 8 In the limit, when the slenderness ratio of the support member (Kl/r) is equal to the critical slenderness ratio (Cc), the allowable compressive stress reaches its minimum value of (6/23) x Sy. Since (6/23) x Sy is greater than Sy/6, the compressive stress limit for lineartype supports is automatically satisfied and, therefore, buckling is not a concern. Lastly, the slenderness ratios of the main components under compression (i.e., BOM Items 1, 2 and 3 on Drawing No. 10894) have been confirmed to be less than the critical slenderness ratio for their materials of construction. This additional information will be documented in the next revision to Supplement 9 to HI2177585.

If a seismic event were to occur while the Horizontal Lift Beam was being used to handle the HISTAR 190 Transport Cask, it would not result in a lifting device failure or a load drop. This is because the design safety factors for the Horizontal Lift Beam and the slings are high in relation to the seismic amplification factors associated with the site design basis earthquake. In quantitative terms, the Horizontal Lift Beam is designed with increased safety factors of 6 and 10, respectively, against the yield strength and ultimate strength of the construction materials. Meanwhile, the slings must have a minimum safety factor of 10 against their ultimate load. By comparison, the peak vertical acceleration

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 associated with the most severe Design Extended Condition Earthquake (DECE), which is defined in SAR Table 4.3.3 as a RG 1.60 earthquake with a ZPA value of 0.25g in three orthogonal directions, is only 0.75g. This means that the seismic amplification factor is not more than 1.75. Therefore, even if a seismic event were to occur, the primary stresses induced in the Horizontal Lift Beam would remain well below the material yield strength, and the slings would still maintain at least a 5:1 margin with respect to their ultimate load.

RAI 524: Justify the how the title frame, saddle, Transport Cask Horizontal Lift Beam, slings, and other lifting equipment used to lift a transportation cask are seismically exempt.

Supplement 13 to Holtec Report No. HI2177585R0 states that seismic analysis of these components is not performed because they are seismic exempt as per the document Licensing report on the HISTORE CIS Facility, HI2167374, Revision 0 (i.e., the HISTORE SAR). The SAR states, in part, that: [f]ollowing the universally practiced lift and set rule at nuclear power plants, transient activities such as upending of a cask, attaching of slings or installation of fasteners, are treated as transient activities that are not subject to a seismic qualification. For clarity of application, any activity that spans less than a work shift is deemed to be seismicexempt.

There is no reference where the lift and set rule is stated and approved by the NRC for use. In addition, as written, it appears as if only one handling operation will ever occur at the facility. However, an undetermined number of operations (work shifts) are expected to occur at the facility, and the duration of a shift is not specified. These should be considered in a duration approach argument and should be documented clearly in the technical specifications. Nonetheless, the regulations do not exempt a seismic evaluation of these components. Specifically, 10 CFR 72.122(a)(2)(i) states:

(i) Structures, systems, and components important to safety must be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, lightning, hurricanes, floods, tsunami, and seiches, without impairing their capability to perform their intended design functions. The design bases for these structures, systems, and components must reflect:

(A) Appropriate consideration of the most severe of the natural phenomena reported for the site and surrounding area, with appropriate margins to take into account the limitations of the data and the period of time in which the data have accumulated, and (B) Appropriate combinations of the effects of normal and accident conditions and the effects of natural phenomena.

The provisions of 10 CFR Part 72 do not exempt this equipment from being seismically qualified. Thus, ITS equipment such as the title frame, saddle, Transport Cask Horizontal Lift Beam, slings, and other lifting equipment used to lift, and transport spent nuclear fuel have to be designed with seismic loading.

This information is necessary to determine compliance with 10 CFR 72.122(b)(2)(i)

Holtec Response:

The occurrence of an earthquake during a singular lifting operation is an extremely low probability event, and therefore it may warrant consideration as noncredible. However, the staff correctly notes that a multitude of lifting operations are expected to occur at the HISTORE CIS Facility on an annual

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 basis, and therefore Holtec agrees that the possibility of an earthquake occurring during a repeated lifting operation cannot be ruled out.

That being said, the HISTORE CIS Facility is a low intensity earthquake site, which means that the load increase associated with an earthquake event is offset by the increased design factors for the lifting equipment and/or the increase in allowable stress that is associated with an accident level event. The seismic qualification of the Transport Cask Horizontal Lift Beam and its sling attachments is discussed specifically in the response to RAI 523. The same general rationale applies to the HISTAR 190 Lift Yoke, the HITRAC CS Lift Yoke, the MPC Lift Attachment, and the HITRAC CS Lift Links, as they are all designed and analyzed as ANSI N14.6 special lifting devices with minimum safety factors of 6 and 10 against the material yield strength and the ultimate tensile strength, respectively. The HISTAR 190 Tilt Frame and Saddle are further discussed below.

Per Subsection 4.3.6 of the SAR, the applicable earthquake event for ShortTerm Operations, which includes all lifting and handling operations from the time the transport package is received at site until the canister is placed in a HISTORM VVM for interim storage, is the Operating Basis Earthquake (OBE).

Per SAR Table 4.3.4, the OBE event is defined as a 2% damped RG 1.60 earthquake with a ZPA value of 0.10g in three orthogonal directions. Accordingly, the peak acceleration associated with the OBE vertical response spectrum is 0.405g, which means that the demand load on the Tilt Frame and Saddle would increase by no more than 40.5% under OBE conditions. On the other hand, the percentage increase in allowable stresses between ASME NF Level A (normal) and ASME NF Level B (offnormal) is 33% per Table NF3251.21. These two percentage factors can be used to make a conservative estimate of the minimum safety factor for the Tilt Frame and Saddle under OBE conditions.

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PROPRIETARY INFORMAITON WITHHELD PER 10CFR2.390

]

Thus, the Tilt Frame and Saddle have the required structural capacity to resist the maximum loads during an OBE event, which is the applicable earthquake for ShortTerm Operations per the SAR.

RAI 525: Clarify the margin of safety of the lift yoke with respect to lateral torsional buckling when lifting a fully loaded MPC.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Licensing Drawing 10900 depicts two strong back plates (BOM 1) which act in unison when performing lifting operations. During lifting operations, these two plates will be subjected to bending moments with unbraced compression flanges, which could undergo lateral torsional buckling. It is noted that thin rods (spacers) that link these two plates are depicted on the licensing drawings, but their ability to brace these two components is unknown, and their dimensions and material properties have not been provided. An evaluation of lateral torsional buckling for the lift yoke was not provided. The calculations and licensing drawings should be updated, as necessary.

This information is necessary to determine compliance with 10 CFR 72.92 and 72.122(b)(2)(i).

Holtec Response:

Supplement 4 to HI2177585 will be revised to address lateral torsional buckling of the strong back plates associated with the Lift Yoke for the HITRAC CS.

RAI 526: Demonstrate that the proposed UMAX ISFSI storage pad design at the proposed CIS Facility would not fail due to sliding under dynamic loading.

The UMAX ISFSI pad design creates a new interface between Space A and Space C in the subgrade material (Figure 4.3.1 of the HISTORE SAR). Due to significant differences in material stiffnesses (Controlled Low Strength material in Space A is stiffer than the materials in Space B or C, which are native soil), a seismic event may cause a failure due to slippage or sliding along this interface and/or along a critical failure surface within the material in Space B or Space C. The assessment should establish that the shear resistance provided by the interface and the materials in Space B would be able to resist such sliding of the pads. Therefore, an analysis is needed to ensure that the proposed storage pads would not fail by sliding under the anticipated dynamic loads. Alternatively, the applicant may provide a reference to specific bounding analyses from the HISTORM UMAX FSAR, if any, that consider and analyze this scenario or bounds it.

This information is necessary to determine compliance with 10 CFR 72.24(a), 72.103, and 72.122.

Holtec Response:

The HISTORE system is licensed for regions of mild earthquakes. As shown in Table 4.3.3 of the HI STORE SAR, the ZPAs of the 10,000year return earthquake (i.e., the Design Basis Earthquake) of the HI STORE site are not greater than 0.15g. As a result, the ratio of the seismic inertia force applied to Space A to the total weight of Space A is smaller than the static friction coefficient between Space A (CLSM) and Space C (soil) (which is greater than 0.3). Therefore, an earthquake induced sliding between Space A and Space C is not credible at the HISTORE site. The above conclusion is also consistent with the NUREG/CR6896, which concludes that separation between embedded nuclear power plant structure and the surrounding soil is not expected for seismic inputs with ZPAs less than 0.3 g.

RAI 66: Clarify how long an MPC will remain within the HITRAC CS transfer cask if the UMAX heat removal system is declared inoperable.

Technical Specification Bases B.3.1.1 C.2.2 (Page 16.A12 of HISTORE SAR) indicates that a MPC can be stored within a HITRAC CS, but does not specify a time period within which it would be required to return the MPC back to a storage condition. There was no corresponding time period specified for the

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 MPC to remain within the HITRAC CS, recognizing that a number of analyses (e.g., thermal, structural) are typically performed to ensure safe operation during longterm storage. The SAR should provide an analysis to specify a time limit that the MPC can remain within the transfer cask.

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

Technical Specification Bases B.3.1.1 C.2.2 states that placing the MPC into a HITRAC CS will ensure adequate fuel cooling until actions to correct the heat removal system inoperability can be completed (emphasis added). The duration is, therefore, not limited to any particular value but is the duration that is necessary to restore the UMAX to operable status. This qualitative duration is acceptable because the thermal evaluation for normal onsite transfer in the HITRAC CS is a steadystate evaluation, and therefore bounds any possible duration.

Temperatures and internal pressure for cask components and the cladding of intact fuel assemblies at the designbasis maximum decay heat load under steadystate conditions in the HITRAC CS are reported in Table 6.4.6 of the HISTORE SAR. The HISTORE SAR adopts longterm temperature and pressure limits for the MPC and fuel assemblies from Revision 3 of the HISTORM UMAX FSAR. Allowable temperatures for HITRAC CS components are given in Table 4.4.1 of the HISTORE SAR. The following table compares the steadystate temperatures and pressure with their corresponding allowable values.

Component Temperature, °F LongTerm Limit from ShortTerm HISTORM UMAX Operations Limit from FSAR, °F HISTORE SAR, °F Fuel Cladding 669 752 -

Fuel Basket 615 752 -

Basket Shims 507 752 -

MPC Shell 461 650 -

MPC Lid 416 752 -

MPC Baseplate 343 752 -

HITRAC Inner Shell 352 - 600 HITRAC Concrete 271 - 300 HITRAC Outer Shell 200 - 600 MPC Internal Cavity 96 100 -

These results and comparisons to limits show that there is no limit to time the MPC may remain in the HI TRAC CS while the UMAX heat removal system is restored to operable status.

RAI 67: Update the draft Design Feature Technical Specification to indicate the minimum HISTORM UMAX module pitch justified by the thermal analysis.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The minimum HISTORM UMAX pitch spacing, which is an important parameter for thermal performance and safe operation of the system, was not included in the proposed Technical Specifications.

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

The pitch of 15 feet 6 inches, shown in Holtec Drawing 10875 in HISTORE SAR Section 1.5 and evaluated in Holtec Report HI2177591, has been added to Section 4.2.3 of Appendix A of the proposed Technical Specifications. The incorrect pitch in Table 1.1.1 has also been corrected.

RAI 68: Update the Technical Specification Surveillance requirement SR 3.1.2 so that it considers the 32 hour3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br /> time period to reach allowable limits, as stated in Section B 3.1 C.2.1 (HISTORE SAR Chapter 16, page 16.A11).

The proposed Technical Specifications (SR 3.1.2) suggests that a vent could be blocked for 54 hours6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br />, based on the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO 3.1.1 to restore the system to operable status and the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (plus 25%

factor, per SR 3.0.2) SR 3.1.2, 24hour surveillance frequency.

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

The storage module deployed at HISTORE is the UMAX, which has already been reviewed and certified by the NRC on Docket 721040 and this proposed technical specification is identical to LCO 3.1.2 in Appendix A to the HISTORM UMAX CoC issued by the NRC. To date it has not been required to include the surveillance interval (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) or the tolerance on the surveillance interval (1.25 times) into the event duration.

RAI 69: Clarify that installed temperature monitoring equipment is to be designated as Important to Safety if it is used as part of surveillance requirements to fulfill Technical Specifications.

The proposed Technical Specification SR 3.1.2 indicates that VVMs installed with temperature monitoring equipment can be used as part of the surveillance requirements to ensure SFSC integrity, rather than periodic visual surveillance. However, Section 3.4 of the HISTORE SAR indicates that temperature monitoring equipment is not important to safety.

This information is needed to determine compliance with 10 CFR 72.26 and 72.128(a)(1).

Holtec Response:

Following the precedent of the HISTORM UMAX generic license (Docket 721040) the temperature monitoring equipment is only designated as Important to Safety If the temperature elements and associated temperature monitoring instrumentation are used as the sole means of surveillance.

Subsection 3.4.1 of the HISTORE SAR has been modified to reflect this.

RAI 610: Specify and provide the basis for the criteria associated with the proposed Technical Specification SR 3.1.2.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 There is no clear basis provided in the SAR for the 91 deg F temperature difference between the average VVM air outlet duct temperature and the ISFSI ambient temperature mentioned in the proposed Technical Specification SR 3.1.2. In addition, a LCO criteria was not specified in the proposed Technical Specification Basis SR 3.1.2 in Chapter 16 of the HISTORE SAR.

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

The 91 deg F temperature difference is the difference between the normal ambient temperature given in HISTORE SAR Table 2.7.1 and the UMAX average air outlet temperature given in HISTORE SAR Table 6.4.3. This basis has been added to SR 3.1.2 in Chapter 16 of the HISTORE SAR.

RAI 611: Update the proposed Technical Specification LCO 3.1.1 to state that operability is defined as 50% or more of the inlet vent duct areas and 100% of the outlet vent areas are unblocked and available for flow.

Currently, proposed Technical Specification LCO 3.1.1 states that the SFSC Heat Removal System is operable when 50% or more of the inlet vent duct areas are unblocked and available for flow. However, Section 4.6.1.2 of the HISTORM UMAX FSAR, which is incorporated by reference, only indicated the results for thermal performance when the HISTORM UMAX air inlet vents were 50% blocked (no mention of outlet vents).

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

The storage module deployed at HISTORE is the UMAX, which has already been reviewed and certified by the NRC on Docket 721040. As such, the accident 100% vent blockage scenario for the HISTORE is intended to be the same as that for the UMAX, namely a 100% blockage of the inlet vents. Any HISTORE SAR text referring to blockage of the outlet vents is, therefore, inadvertent. All HISTORE SAR text concerning the vent blockage accident condition, including the description of proposed Technical Specification LCO 3.1.1, has been clarified to state that the outlet vent area is at least 50% unblocked and available for flow.

There are two primary reasons why blockage of the storage module outlet vents is not considered a credible event for the HISTORE. First, ventilation air exiting the outlet vents is incapable of drawing items into the vents. Airflow toward an inlet vent could entrain lightweight materials like plastic sheeting or fallen leaves, drawing it up against and holding it against the vent screen. But airflow away from an outlet vent would tend to push such items away. Second, as described in Section 2.3.1 of the HISTORE SAR, snowfall significant enough to block the outlet vents is not credible. The bottom edge of the outlet vents is over 12 above the top of the lid horizontal surface that could accumulate snowfall (shown on Sheet 3 of Holtec Drawing 10875 in HISTORE SAR Section 1.5). This exceeds the largest ever recorded snowfall for the site, 10 inches in February 1956, described in the SAR Subsection 2.3.1. Moreover, heated air exiting the outlet vents would melt snow as it falls, further reducing accumulation.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Additionally, the magnitude of impact on cask heat removal resulting from 100% blockage of both inlet and outlet vents has been estimated for the Holtec HISTORM FW storage cask (Docket 721032). The HI STORM FW is an aboveground cask, but like the UMAX to be deployed at HISTORE cooling air is still introduced near the bottom of the MPC within and heated air still exits above the top of the MPC. As stated in Subsection 4.6.2.4 of the HISTORM FW FSAR:

The amount of heat removed from the MPC external surfaces by natural circulation of air is reduced to less than 7% of that under normal conditions (i.e. when inlet and outlet vents completely unblocked). Therefore, in an unlikely event of complete blockage of both inlet and outlet vents, that small additional heat removal capability by air through outlet vents is also lost.

This will result in a small temperature rise compared to the large available temperature margins (greater than 80°C) established from the transient study of complete inlet vents blockage.

Due to the fact that the cooling air enters the cask below the MPC and exits above the MPC in both the HISTORM FW and the UMAX, and due to the UMAX also having significant margin (for example, greater than 50°C for the fuel cladding), it is reasonable to conclude that the margin is sufficient to accommodate the temperature rise due to a coincident 50% outlet duct blockage.

RAI 612: Provide the maximum ambient temperature limit for conducting short term operations in the Technical Specifications.

Proposed Technical Specification 4.2.4 indicates that operations should not be performed if ambient temperatures are below 0 deg F. There was no corresponding maximum temperature limit for conducting short term operations and no transfer analyses, for example, at accidentlevel ambient temperatures. The maximum ambient temperature analyzed for short term operations was reported as 91 deg F in Table 6.4.1 of the HISTORE SAR and Table 1.1 of Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask. However, the HISTORE SAR, including in Table 2.7.1, indicates that ambient temperatures could be above that value (e.g., 108+ deg F).

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

The restriction on performing short term operations at ambient temperatures below 0 deg F is necessary to protect against freezing of water (water with antifreeze below 32 deg F) in a transfer cask containing very little decay heat. Due to the considerable thermal inertia of the HITRAC CS transfer cask, which will prevent the it from rapidly responding to instantaneous ambient temperature variations, the appropriate maximum ambient temperature limit for conducting short term operations is the three day average ambient of 91 deg F reported in Table 6.4.1 of the HISTORE SAR and used in HI2177553. It is not necessary to apply a similar restriction on maximum instantaneous ambient temperatures, which can be up to 108 deg F as reported in Table 2.7.1 of the HISTORE SAR.

RAI 613: Update the proposed Technical Specification Design Feature 4.2.1 to indicate that the design of the HISTORM UMAX modules are limited to Type SL and Type XL of the UMAX Version C module.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Holtec Report No. HI2177591, Thermal Evaluation of HISTORM UMAX at HISTORE CIS Facility, states that MPCs of certain heights are to be installed in Type SL or Type XL UMAX Version C modules with storage cavity depths made at two discrete dimensions. The thermal analyses and performance of the system are based on these design aspects, but they were not included in the Technical Specifications.

This information is needed to determine compliance with 10 CFR 72.26 and 72.122(b).

Holtec Response:

Proposed Technical Specifications Section 4.2.1 has been updated to indicate that the design of the HI STORM UMAX modules are limited to Type SL and Type XL of the UMAX module.

RAI 614: Provide the Holtec Engineering Change Order (ECO) 502124, Revision 0, and its corresponding 10 CFR 72.48 evaluation.

Section 2 of Holtec Report No. HI2177591, Thermal Evaluation of HISTORM UMAX at HISTORE CIS Facility, states that the thermal model is based on ECO 502124, but this was not provided in the application.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The ECO referenced was fully incorporated into the HISTORM UMAX FSAR Revision 4, and all subsequent revisions, which have been submitted on the HISTORM UMAX docket.

RAI 615: Provide additional discussion that explicitly describes the analysis principles and methodology for the thermal analyses found in Holtec Report No. HI2177553.

Section 2 of Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask, broadly states that the analysis principles and methodology for the calculations are adopted from the HISTORM FW FSAR and HISTORM UMAX FSAR. The principles and methodology relevant to the HITRAC CS should be described or specific sections/paragraphs of the HISTORM FW FSAR and HISTORM UMAX FSAR should be referenced for staff to evaluate the thermal analyses of the HITRAC CS.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The thermal analyses principles and detailed methodology adopted for HITRAC CS are described in Section A.2 and Section B.2 of Holtec Report HI2177553 for normal and accident conditions respectively.

While these principles and methodologies are based on Section 4.4.1 of HISTORM UMAX and Section 4.4.1.1 (iii) of the HISTORM FW FSAR, the detailed methodologies in context of HITRAC CS evaluations are included in the respective appendices.

RAI 616: Provide the mass and energy residuals, mass and energy balances, DO balances, and justification of grid convergence for the thermal analyses mentioned in Section 6 of the HISTORE SAR and those provided in Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask;

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Holtec Report No. HI2177591, Thermal Evaluations of HISTORM UMAX at HISTORE CIS Facility; and Holtec Report No. HI2177597, HISTORE CTF Thermal Evaluation.

The abovementioned numerical criteria, which are part of computational best practices (e.g. NUREG 2152) are needed to confirm that the results provided in the referenced thermal analyses are relevant to the review.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

To address the regulators comment, numerical residuals, energy balance and mass balances are now included in the respective calculations packages to demonstrate numerical convergence of the results. It is verified that the energy and mass balances are essentially 100% and that the peak cladding temperature and numerical residuals have stabilized. This is consistent with the approach adopted in other dry storage license applications such as HISTORM UMAX FSAR (USNRC Docket No. 721040) and the HISTAR 190 SAR (USNRC Docket No. 719373).

As an example, the numerical residuals from the normal storage condition evaluations of HISTORM UMAX documented in HI2177591 are shown below. The numerical residuals for HITRAC CS and HISTAR in CTF evaluations are added to HI2177553 and HI2177597 respectively.

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RAI 617: Provide additional information about the air pathway geometry through the bottom of the HI TRAC CS shield gates while the HITRAC CS and HISTAR 190 are within the Canister Transfer Building and clarify how the air pathway area is correctly represented in the thermal models.

Holtec HITRAC CS Licensing Drawing 10868, Revision 0 (referenced in Section 7.0 of Holtec Report No.

HI2177553, Thermal Analysis of HITRAC CS Transfer Cask) does not clearly call out the air pathway or its dimensions. This information is needed to determine the appropriateness of the thermal model during canister transfer described in Holtec Report No. HI2177553.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Holtec Response:

The airflow pathway within the shield gate is shown in the following regions of the HITRAC CS Licensing Drawing (Holtec Drawing 10868, Revision 0):

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The above details in the licensing drawing 10868 provide the necessary geometric information and dimensions for the thermal model. To provide further clarity to the reviewer, additional figures showing the as modelled airflow paths through the HITRAC CS shield gate and respective computed path lines are added in the revised thermal report (HI2177553). The design dimensions and modelled dimensions are also tabulated in Appendix A of the revised report.

While, the HITRAC CS is placed above the HISTAR 190 cask in the CTF, the shield gates are in the open position, allowing direct flow path through the HITRAC cavity as shown in Figure 6.4.3 of the HISTORE FSAR and is reproduced below. Since the shield gates are in fully open position, they do not have any impact on the thermal evaluations of HISTAR 190 in CTF presented in HI2177597.

WARM AIR OUT

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Figure 6.4.3 of HISTORE FSAR: Ventilation Path when the HITRAC CS is Arrayed on Top of the CTF RAI 618: Clarify the relation between the MPC shells inner and outer diameters and the width of the gap between the MPC shell and HITRAC CS cask (Item 5 in Section A.3 of Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask).

Holtec Report No. HI2177553 does not provide the actual gap and modeled gap between the MPC shell and HITRAC CS cask. Staff needs this information to determine if the thermal model conservatively estimates the temperature limits.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

As indicated in Flag Note 31 of the MPC37 Licensing Drawing (Reference [9] in Report HI2177553), a higher MPC shell thickness (and therefore a larger MPC OD of 76) is permitted for use in HISTORM UMAX System. When an MPC with increased shell thickness is placed in the HITRAC CS, the annular gap between HITRAC and MPC is reduced as compared to a smaller diameter MPC.

The primary mode of heat dissipation from the MPC in the HITRAC CS system is via natural convection.

Using a lower bound annular gap is conservative for thermal evaluation as it offers more resistance to natural convection flow through the annulus. Therefore, the reduced annular gap corresponding to the MPC with higher shell thickness is adopted for the licensing basis evaluation to ensure bounding temperatures and pressures are computed. The reference gap and bounding gap adopted in the analyses are provided in the below table for clarity.

Nominal annular gap and modelled annular gap between HITRAC and MPC

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RAI 619: Justify the heat transfer boundary conditions that are used during the Canister Transfer Building (CTF) collapse accident scenario.

Many of the details, assumptions, and justifications for the heat transfer boundary conditions described in Section B.2.2 of Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask, and Section 1.0 of Holtec Report No. HI2177597, HISTORE CTF Thermal Evaluation were not provided.

The response should address the following:

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 a) the basis for only a 25% penalty on the heat transfer coefficient, recognizing that a typical buoyant flow pattern around a vertical cylinder would be disturbed by a collapsed structure; b) the basis of certain radiation heat transfer parameters, such as the reported 30% penalty of surface emissivity, the external ambient temperature from a locally close structure (used for radiation heat transfer calculations), view factor, solar flux on the building; c) confirmation that the shield gate inlets are the only air inlet to the HITRAC CS ventilated flow and that those are 100% blocked; d) the basis for 10% of the exit air area remains unblocked and clarify the exit areas (HITRAC CS, CTF pipe vents, CTF cavity top) of HITRAC CS and CTF (refer to HISTORE SAR Figure 6.4.3);

e) explanation of how the 10% exit area remaining unblocked, whereas page B7 of HI2177553 states that 100% of the top opening of the HITRAC CS cavity is assumed to be blocked in the thermal model; f) the justification for the assumption (Holtec Report No. HI2177597) that excluding the HI TRAC CS from being placed in the stackup position is bounding, considering that Section 6.1 of the HISTORE SAR states that the limiting thermal condition occurs when the canister is loaded in the transfer cask and its shield gate is closed.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

Note, that the CTB design has been revised to be a hardened concrete structure, and due to its security related functions, building collapse is no longer credible. However, for completeness, the response to the reviewers question is provided below.

Thermal evaluation of HITRAC CS under CTB collapse accident is evaluated with certain reasonable assumptions as explained below:

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RAI 620: Clarify whether Equation B.2.1 (Section B.2.1.2 of Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask) is meant to provide the temperature rise due to the solid phase fire or the total temperature rise. In addition, provide the temperature rise and thermal load due to the solid phase fire and the temperature rise and thermal load due to the liquid phase fire and explain how the T was applied to the model to determine the values reported in Table B.6.1.1.

The text preceding Equation B.2.1 states that the equation is to provide the temperature rise due to the solid phase fire; however, the equation uses the subscript total, rather than solid, which is then used in the subsequent terminology section (possibly there is a typographical error in the equation). Based on the above, the staff does not understand the intent of the equation as written and, therefore, how its results factor in the values reported in Table B.6.1.1.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

There is a typographical error in Section B.2.1.2 of Holtec report HI2177553. The temperature rise (T) computed here is the total temperature rise due to liquid and solid phase fires combined. The computed T is added to the initial condition to obtain the maximum temperatures during postfire cool down. This is corrected in the revised thermal report.

The thermal load due to the solid phase and liquid phase fires combined is added in Appendix B of the report. The total temperature rise ratio (Ttotal/Tliquid) is also presented in Table B.2.1. Since this ratio is close to unity (1.0048), it is concluded that the additional temperature rise due to heat flux contribution from the solid phase fire is negligible, which is also stated in Section B.6.1.1 of the report.

RAI 621: Clarify the 640 deg F HITRAC CS concrete temperature during the CTB collapse accident scenario, reported in Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask, considering that HISTORE SAR Table 4.4.1 has a 572 deg F allowable local maximum temperature limit under accident conditions.

In the response to RAI 1710, the allowable accident temperature of the shielding concrete in HISTORE SAR Table 4.4.1 was revised to align with the Holtec Position Paper DS289. However, the HITRAC CS concrete temperature during the CTB collapse accident scenario was calculated to be significantly above the revised limit for accident conditions.

The inconsistency between the calculated concrete temperature and the allowable temperature limit should be addressed. If the allowable temperature will be exceeded, provide a technical basis that demonstrates that the temperature exposure will not degrade the concrete to an extent that could prevent it from fulfilling its intended functions.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The NRC staff is correct that the maximum local temperature of the HITRAC CS concrete exceeds the revised accident temperature limit of 572oF under the hypothetical CTB collapse accident. However, it must be noted that portion of the cask concrete that exceeds this limit is accounted for by using reduced concrete density (See Table 7.3.1 of the HISTORE SAR) in shielding evaluations (Holtec Report HI 2177599). Consistent with the UST criteria, the amount of concrete that exceeds 554oF1 under this accident is added to Appendix B of the revised Thermal Report HI2177553.

RAI 622: Confirm that the thermal analyses presented in Chapter 6 of HISTORE SAR; Holtec Report No.

HI2177597, HISTORE CTF Thermal Evaluation; Holtec Report No. HI2177553, Thermal Analysis of HITRAC CS Transfer Cask; and Holtec Report No. HI2177591, Thermal Evaluations of HISTORM UMAX at HISTORE CIS Facility, are based on the bounding content to be stored at the HISTORE CISF.

1 The UST criteria set forth in Chapter 6 of HISTORE SAR suggests a minimum of 10oC margintolimit.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Several references in the license application provide differing descriptions of the bounding content assumed in the thermal analyses. For example, Calculation Package HI2177597 refers to Fort Calhoun fuel (Page 9 of 26) as bounding content. Section 6 of the HISTORE SAR states that the heat load in any canister cannot exceed that in the transport cask (i.e., HISTAR 190), and Page 1 (4 of 31) of Calculation Package HI2177591 states that the content at the site is for those approved in HISTORM FW FSAR and HISTORM UMAX FSAR. Likewise, Section 6.4.2.3 of the HISTORE SAR refers to Section 4.4 of the HI STORM UMAX FSAR as providing bounding content but Note 5 of Table 6.4.1 of HISTORE SAR refers to Appendix 7.C of the HISTAR 190 SAR as the bounding heat load. Bounding content should be analyzed in order to determine bounding temperature and pressure conditions.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The reviewers comment is addressed below in two parts.

Heat Load: Consistent with the statement in Section 6.0 of the HISTORE SAR, bounding heat load approved in the HISTAR 190 SAR (Appendix 7.C), is adopted for all the evaluations presented in the HI STORE SAR, as well as the supporting calculation packages - HI2177585, HI2177553 and HI2177591.

The heat load patterns 1 through 6 and the bounding pattern (pattern 1) provided in Table 4.1.1 of the HISTORE SAR is the same as that provided in Table 7.C.7 of the HISTAR 190 SAR. Therefore, the bounding pattern established in the HISTAR 190 SAR is adopted for all the evaluations presented in Chapter 6 of the HISTORE SAR and the supporting calculation packages listed above.

Fuel Assembly: As described in Section 4.4 of HISTORM UMAX FSAR (Docket 721040), PWR short fuel (sometimes referred to as Ft. Calhoun in Holtec reports), is established as the bounding fuel assembly type for thermal evaluations in the HISTORM UMAX FSAR for pressurized MPCs with thermosiphon effect.

Therefore, PWR Short Fuel is also adopted for all the evaluations presented in HISTORE SAR as well as Holtec reports listed above.

Therefore, the thermal evaluations presented in Chapter 6 of the HISTORE SAR adopts bounding content as explained above.

RAI 623: Provide details of the pedestal and corresponding cutouts to ensure an appropriate design is modeled within the CTF thermal analyses.

Licensing Drawing 10895 does not provide design details of the pedestal, but rather notes that [t]he pedestal shall be made to meet the required heat transfer requirements in the CTF. In addition, there are no bases for certain aspects of the pedestal that are briefly mentioned in Section 2.0 of Holtec Report No. HI2177597, HISTORE CTF Thermal Evaluation. For example, there is no basis for the bounding nature of the 1 W/mK thermal conductivity, no description of the relative sizes between the pedestal and cutouts, which would affect heat transfer, and no discussion to indicate how the thermal models correctly represent the pedestal design.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 To address the NRC staffs comment, the pedestal design is now presented in the drawing 10895.

The thermal evaluations in Report HI2177597 models the pedestal as a solid cylinder with an understated thermal conductivity. The pedestal design in drawing 10895, has a higher metal volume fraction and therefore higher effective thermal conductivity than that adopted in evaluations presented in report HI 2177595. The evaluations also conservatively neglect radiative heat transfer between the pedestal and the ground, as well as natural convection in the gas spaces within the pedestal shell.

The description in Section 2.0 of Holtec Report HI2177597 has been revised to include the above information.

RAI 624: Clarify that the maximum pressures for the short term CTF normal operation (e.g., Table 6.3 of Holtec Report No. HISTORE CTF Thermal Evaluation) and the CTB collapse accident scenario are based on having the maximum initial backfill pressure for the pressure range reported in Section 2.0 of HI 2177597, Methodology and Assumptions.

The calculation package states that the minimum backfill pressure is used in the thermal analyses to understate the thermosiphon effect within the MPC. However, the determination of maximum pressure, which should be reported, is based on the maximum backfill pressure for normal, offnormal, and accident conditions.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

Yes, the maximum initial helium backfill pressure values are used in computing the MPC cavity pressure under all scenarios presented in the report. This has also been stated in Section 6.3 of report HI2177597.

RAI 625: Confirm that the component temperatures in the HISTORE SAR and Holtec Report No. HI 2177597, HISTORE CTF Thermal Evaluation; Holtec Report No. HI2177553, Thermal Analysis of HI TRAC CS Transfer Cask; and Holtec Report No. HI2177591, Thermal Evaluations of HISTORM UMAX at HISTORE CIS Facility, satisfy the unconditionally safe threshold (UST) after considering the effects due to modeling uncertainties (e.g., grid convergence uncertainty).

The acceptability of component temperatures should be reviewed considering that the HITRAC CS concrete after the CTB collapse accident scenario appears to indicate that the 640 deg F temperature may not satisfy the unconditionally safe threshold (UST) defined in Section 6.0 of the HISTORE SAR, which did not address the effects due to grid convergence uncertainty.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The computational grids adopted for the thermal evaluations presented in Holtec Reports HI2177553, HI2177591 and HI2177597 are consistent with the converged mesh established in past thermal evaluations.

HI2177553 (HITRAC CS): The computational mesh for MPC37 is exactly that adopted for the licensing basis calculations performed in HISTORM UMAX FSAR (Docket No. 721040). The computational mesh

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 density adopted for the HITRAC geometry, particularly in the annular gap is similar to that adopted in the NRC approved licensing basis evaluations performed for HISTORM UMAX under Docket No. 721040. The grid convergence index for this grid is therefore expected to be in the same order as that for the HISTORM UMAX thermal evaluations which is ~1.07%. Since there are robust margins (>10oC) for all components, it can be concluded to satisfy the unconditionally safe threshold. As outlined in RAI 621 and addressed in the revised thermal report HI2177553, the portion of HITRAC concrete that exceed the temperature limit already considers the UST criteria and adopts a 10oC penalty.

HI2177597 (HISTAR 190/CTF): The computational mesh adopted for evaluation the HISTAR 190 cask with MPC37 canister in the CTF at HISTORE CISF is same as that presented in the licensing basis evaluations presented in in HISTAR 190 SAR (719373). The computational grid for the CTF components and the air volume around the HISTAR cask follows best practice guidelines such as maintain y+ below 4.

Considering the large margins on component temperatures and pressure available under both normal and accident scenarios, it is concluded that the thermal evaluations in HI2177597 satisfy the unconditionally safe threshold.

HI2177591 (HISTORM UMAX): The computational mesh adopted in the thermal evaluations documented in HI2177591 is the same as that adopted for all licensing basis evaluations presented in Section 4.4 of the HISTORM UMAX SAR. Additionally, due to the lower allowable decay heat loads and more favorable ambient conditions in HISTORE SAR (than that for HISTORM UMAX qualified under docket 721040),

robust margins (>10oC) are available to the HISTORM UMAX/MPC37 temperature limits at HISTORE CISF. The GCI established under docket in Chapter 4 of HISTORM UMAX FSAR (Docket No. 721040) is 1.07% on the peak cladding temperature. Therefore, it can be concluded that the thermal evaluations presented in HI215591 meets the UST criteria set forth in Chapter 6 of the HISTORE CISF FSAR.

RAI 626: Provide the HISTAR 190 Oring minimum and maximum temperature limits and its temperature for the building collapse scenario.

The application did not include the allowable temperature limits for the Orings. In addition, Table 6.2 of Holtec Report No. HI2177597, HISTORE CTF Thermal Evaluation, listed HISTAR 190 component temperatures but did not include the Oring.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The maximum temperature limit of the HISTAR 190 Oring under normal and accident conditions is provided in Table 4.4.4 of the HISTORE CISF FSAR. This Oring is rated to a minimum temperature of 40oF since it is also used in transport condition (see Chapter 3 of USNRC Docket No. 719373).Under the hypothetical CTB collapse evaluation, the HISTAR cavity is assumed to be filled with nitrogen/air i.e. no credit is taken for the presence of helium within the HISTAR cavity. The sealing functionality of the HI STAR lid is not relied upon under this scenario and therefore the Oring temperature is not reported. To address reviewers specific request on the Oring temperatures, the temperature of Oring under this accident has been postprocessed and found to be 243oC.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 627: Clarify in Chapter 3 of the HISTORE SAR that the HISTAR 190 is the only transportation package that is used to ship content to the HISTORE CISF.

Chapter 3 (Page 33) of the HISTORE SAR states that transportation packages other than the HISTAR 190 would be used to transport content. However, the thermal analyses that are provided to demonstrate compliance with site specific parameters and design features are based only on the HI STAR 190 package.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The NRC reviewer is correct that the HISTORE CISF application and basis for evaluation is currently limited to the use of the HISTAR 190 transportation cask for receiving loaded canisters. Revisions have been made to Chapters 1 and 3 to clarify this further. See response to RAI 31 for further details.

RAI 628: Specify the time limits associated with the corrective actions associated with the blockage of air flow malfunction specified in Item 8 of Section 10.3.3.5 of the HISTORE SAR.

The operations procedure mentions the need to perform a corrective action associated with blockage of air flow, but a transient HITRAC thermal analysis with blocked airflow and a time limit to perform the corrective action were neither listed nor provided.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

First, it should be stated that the closure of the shield gates and removal of the HITRAC is not a malfunction but is a planned step. This condition is bounded by the burial under debris event in Paragraph 4.6.2.3 of Revision 3 of the HISTORM UMAX FSAR, which provides an equation for determining an allowable duration. That equation is used to with the maximum allowable decay heat and the minimum allowable component rise to the shortterm operations temperature limit to determine the allowable duration for the HITRAC to be removed from atop the UMAX.

The initial condition for this determination is the steadystate MPC in HITRAC condition. The maximum decay heat is 32.15 kW from Table 4.1.2 of the HISTORE SAR. The minimum temperature rise is for the fuel cladding, which is the difference between the calculated value from HISTORE SAR Table 6.4.6 and the limit of 390°C (400°C from ISG11 Rev. 3 minus 10°C per SAR Section 6.0), or 734°F - 669°F = 65°F or 36°C. The UMAX weight and specific heat capacity are from Table 4.6.8 of the HISTORM UMAX FSAR. For these inputs the allowable blockage time is:

46000 419 36 21582 6.0 32150 If the HITRAC cannot be removed from atop the UMAX within this time, this would be considered an accident condition and would be bounded by the 100% vent blockage event. Paragraph 6.5.2.5 of the HI STORE SAR incorporates Paragraph 4.6.2.3 of the HISTORM UMAX FSAR for this accident condition.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 This discussion has been added to Section 6.4 of the HISTORE SAR.

Finally, it is noted that the caution note refers to time limits described in Section 4.5, which is a typographical error. The caution note following Item 6 in Section 10.3.3.5 has been corrected to refer to time limits described in Section 6.4.

RAI 629: Specify the changes introduced in HISTORM UMAX Version C system that are noted in Table 15.0.1 of HISTORE CIS SAR Chapter 15 and confirm there are no impacts to the thermal model or performance.

The HISTORE SAR states there are changes in the UMAX system from that previously analyzed.

However, descriptions of those changes were not provided such that assessments by technical disciplines could not be performed.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The minor design differences between the HISTORM UMAX Version C and the HISTORM UMAX licensed under docket 721040 are provided in Sections 1.2.1 and 6.4.1 of the HISTORE CISF SAR. To summarize, they are:

1. HISTORM UMAX Version C does not contain the ultrahigh earthquakerestraint options present in the design licensed in USNRC Docket No 721040. The most severe earthquake (MSE) option under docket 721040 has specially engineered locking wedges between MPC and the UMAX divider shell at 8 circumferential locations. This feature (or absence thereof) has no impact on the thermal performance of the system.

2. UMAX cavity depth is fixed to two discrete values and not variable as permitted in the design licensed in USNRC Docket No. 721040. As also has been described in Section 6.4.1, thermal performance of UMAX Version C is either the same or improved.

As stated therein, neither of these design changes adversely affect thermal performance of this system, nor have any impact on the thermal models presented in Chapter 6 of the HISTORE CISF SAR.

RAI 630: Clarify the applicability of the reference to Paragraph 4.6.2.3 of the HISTORM UMAX FSAR for the 100% blockage of air inlets and outlet HISTORE UMAX scenario.

Table 6.0.1 of HISTORE SAR indicates that Paragraph 4.6.2.3 of the HISTORM UMAX FSAR provides information that applies for the scenario of 100% blockage of air inlets and outlet. However, Paragraph 4.6.2.3 discusses the scenario of 100% blockage of air inlets only.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

See response to RAI611 above.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 631: Clarify the definition of maximum section average temperature and bulk average temperature denoted in the notes to Table 6.4.3 and Table 6.4.5 of the HISTORE SAR.

The definitions are required for staff to have a clear understanding of the temperatures reported in the tables.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

Section average temperature is defined as the lineal average temperature through the thickness of a component. Maximum section average temperature, therefore, is the largest section average temperature of all sections through a component. Bulk average temperature is the spatially integrated average of temperatures of an entire component volume. These definitions have been added to the glossary of terms in the beginning of the HISTORE SAR.

RAI 632: Clarify the effects of thermal stresses on the sites SSCs (including UMAX module/VVM, HI TRAC CS, and CTF) due to the temperature gradients from the heat generated by the contents decay heat.

There was no mention of thermal stresses in Chapter 5 of the HISTORE SAR, even though many of the SSCs are new (e.g., HITRAC CS, CTF) or have new designs (e.g., module). Thermal stresses are expected to impact safety margins already calculated (e.g., seismic and tornadic wind effects) since they exist in the analysis of the SSCs a priori. That is, they should be considered concurrently with both seismic and tornadic effects. Update any relevant calculations as necessary.

This information is needed to determine compliance with 10 CFR 72.24(d) and 72.128(a).

Holtec Response:

The welded steel portions of the HISTORM UMAX VVM, the HITRAC CS, and the CTF are all designed to meet the stress limits given in ASME Section III, Subsection NF for Class 3 supports. As such, thermal stresses within the support need not be evaluated, as explicitly stated in note (5) to Table NF3251.21.

The structural design criteria for the HITRAC CS and the CTF are summarized in Paragraphs 4.3.3.1 and 4.3.5.1 of the HISTORE SAR, respectively. The applicable stress limits for the metallic components of the HISTORM UMAX VVM are confirmed in Section 2.6 of the HISTORM UMAX FSAR.

RAI 633: Identify the potential onsite sources of fire or explosion events in SAR Chapter 6, Thermal Evaluation.

The SAR does not describe the source(s) of different fuels needed for operating onsite vehicles, such as the Vertical Cask Transporters and heavy haul tractor/trailers (SAR Section 3.1.4.7, Maintenance Operations), or those used for heating and other operational purposes. Existence or presence of large fuel source(s) (e.g., a fuel storage tank or a tanker truck) near important to safety structures could be a potential hazard that needs to be assessed.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The information should, at a minimum, include the following:

a) Confirm whether the proposed CISF would have any onsite storage tanks for gasoline, diesel, natural gas, or other combustible materials needed for operation; b) Describe how the storage tanks will be replenished periodically, including the frequency, and the routes within the facility that would be taken by the supply vehicle(s) to reach the storage tanks; c) Specify the nearest distance to the important to safety structures and systems from the storage tanks and supply vehicles routes; and, d) Confirm that the storage tanks and the supply vehicles would not pose any safety hazards to the important to safety structures and systems and a loaded cask transporter enroute to the cask storage pad area.

This information is necessary to determine compliance with 10 CFR 72.24, 72.90(a) through (d), 72.94, and 72.122.

Holtec Response:

a) The HISTORE facility site plan includes a single 2500 gallon capacity diesel fuel storage tank, no gasoline storage or propane storage tanks and no natural gas pipelines. See Holtec Drawing 10940 in HISTORE SAR Section 1.5.

b) The diesel fuel storage tank will be refilled as necessary, but probably no more than once per month. A supply truck to refill the diesel fuel storage tank would travel from U.S. Highway 62/180 (about 1 mile away) to Lea County Route 55 to the entrance to the HISTORE facility. The diesel fuel storage tank is approximately 250 feet inside the entrance to the HISTORE facility. See Holtec Drawing 10940 in HISTORE SAR Section 1.5.

c) The diesel fuel storage tank is outside the security fence so there are no combustible materials stored near the casks. The minimum distance from the diesel fuel storage tank to a storage cask is over 1700 feet. A supply truck to refill the diesel storage tank will not need to be any closer than approximately 1650 feet from a storage cask. See Holtec Drawing 10940 in HISTORE SAR Section 1.5.

d) With such large separation distances neither the diesel fuel storage tank nor a supply truck refilling it would pose any safety hazard to a storage cask. Transport truck delivering transportation casks to the HISTORE facility enter the facility and drive past the diesel fuel storage tank, so refueling will be prohibited whenever a transport cask is entering or exiting the facility. This requirement will be implemented in written operating procedures.

RAI 71: Justify how the shielding performance of the ISFSI will be improved under earthquake events or revise the shielding calculation and the SAR to make the shielding calculation consistent with the result of the structural analyses for design basis accident conditions of the system.

Section 1.2.1 of the SAR states that: [t]he height of the lateral seismic restraint at the top of the canister is adjusted to accord with the height of the canister that will be stored in the cavity, and a second set of seismic restraints are situated between the Divider Shell and Cavity Enclosure Container (CEC) at the same height and location as the lateral seismic restraint. As a result, the structural performance of the

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 system remains unaffected and other safety metrics such as shielding and thermal (heat rejection) are either unaffected or improved (depending on the height of the canister being stored). However, the staff notes that these statements seem to show a discrepancy. If the design basis earthquake will not affect the structural performance of the Vertical Ventilated Module (VVM), there should not be any impact on the performance of the thermal and shielding functions of the system. More importantly, the staff does not understand how the shielding function can be improved by the damages resulting from an earthquake event either. The analysis should discuss how the shielding function will not be affected or improved if the canister ends up leaning to one side of the VVM and forms a bigger gap between the canister and the VVM wall that results in a bigger streaming path for radiation. The staffs understanding is that the dose rate at the top of the VVM may increase because the increased streaming path on one side of the canister and the VVM. The analysis should provide additional discussion of how design basis earthquakes will not affect the shielding performance or revise the analyses to make models for shielding analyses consistent with the results of the structural analyses for the system under design basis accident conditions.

This information is necessary to determine compliance with 10 CFR 72.106.

Holtec Response:

To remove an unnecessary point of contention and confusion, the wording is changed to remove the claim that shielding or thermal performance could be improved as a result of an earthquake.

RAI 72: Clarify if any high burnup fuel will be authorized for storage at the HISTORE CISF.

Section 7.1.2 of the HISTORE SAR states that: Assemblies with higher burnups[:] Those would also have correspondingly higher cooling times to meet transport requirements. However, Table 7.1.1 of the HI STORE SAR states that the maximum burnup is 45 GWd/MTU. It is not clear if this statement implies that spent fuel with burnups higher than 45 GWd/MTU will be stored at the CISF. Since the UMAX design allows for storage of fuel with a maximum burnup of 68.2 GWd/MTU for PWR fuel assemblies and 65 GWd/MTU for BWR assemblies( ML14202A032, UMAX FSAR), the applicant should clarify this discrepancy between the burnup limit used in the shielding analysis and these SAR statements.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(b).

Holtec Response:

The high burnup fuel is being authorized for storage at the HISTORE CISF.

The permissible contents for the HISTORE CIS facility is described in Subsection 4.1.1 of the HISTORE SAR, where the authorized materials are incorporated by reference from Section 2.1 of the HISTORM UMAX FSAR. The authorized contents include fuel with a maximum burnup of 68.2 GWd/mtU for PWR fuel assemblies and 65 GWd/mtU for BWR assemblies. To demonstrate compliance with the regulatory requirements, the shielding analysis is revised using the bounding source terms. For additional details about the source terms, the reviewer is referred to the responses to RAIs 73 and 74.

RAI 73: Provide specific minimum cooling time for higher burnup fuel to demonstrate that fuel with higher burnup will meet the design basis source terms limit of the HISTORE CISF.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Section 7.1.2 of the HISTORE SAR, states that: Assemblies with higher burnups[:] Those would also have correspondingly higher cooling times to meet transport requirements. However, the applicant did not provide specific minimum cooling time requirement for each fuel burnup and enrichment limit. Without specific minimum cooling times for burnup and enrichment combination, the staff cannot verify if the higher burnup fuel meets the design basis source terms used in the HISTORE CISF dose analyses.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(b).

Holtec Response:

Since the canisters arrive at the HISTORE CIS facility in a NRCcertified transport cask such as HISTAR 190, the fuel specifications for the HISTAR 190 transport cask, presented in Tables 7.C.7 through 7.C.10 of the HISTAR 190 SAR, are used as the basis of the shielding analysis and they are explicitly provided in Chapter 7 of the HISTORE CISF SAR.

RAI 74: Justify that the calculated source terms considered in the HISTORM UMAX FSAR are applicable to the HISTORE CISF design or revise the shielding analyses accordingly.

Table 7.1.1 of the HISTORE SAR provides the parameters for the design basis (DB) fuel assembly used to perform the shielding evaluation for the HISTORE CISF. Specifically, Table 7.1.1 states that the DB fuel has a burnup of 45 GWd/MTU, 8 years of cooling time, and an initial U235 enrichment of 3.2 weight percent (wt%). Section 7.1.2 of HISTORE SAR further states that the DB source terms for the HISTORM UMAX System were used in the sitespecific shielding analyses for the HISTORE CISF. However, Table 5.2.2 of the UMAX FSAR shows that the DB source terms for the MPC37 canister were calculated based on 45 GWd/MTU burnup and 4.5 year cooling time, but does not state the minimal initial enrichment.

Instead, the UMAX FSAR states that its design basis source terms are the same as those from the HI STORM FW FSAR. The HISTORM FW FSAR referenced in the HISTORM UMAX FSAR states that the source terms calculated for the design basis PWR fuel are based on a WE 17x17 fuel, with 45 GWd/MTU burnup, 4.5 years of cooling time, and an initial enrichment of 3.6 wt%.

These parameters do not match the design basis fuel parameters presented in Table 7.1.1 of the SAR for the HISTORE CISF.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(b).

Holtec Response:

To demonstrate compliance with the regulatory requirements, the shielding analysis is revised using the bounding source terms based on the fuel specifications for the HISTAR 190 transport cask, presented in Tables 7.C.7 through 7.C.10 of the HISTAR 190 SAR. Specifically, for each basket loading region of the MPC37 and MPC89 baskets, the maximum decay heat load is determined from Tables 7.C.7 and 7.C.9:

Maximum Decay Heat Load per Assembly (kW)

Description Region 1 Region 2 Region 3 MPC37 0.95 1.70 0.84/1.1 MPC89 0.35 0.62 0.35

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Then, for each region, all the applicable burnup, enrichment and cooling time combinations in Tables 7.C.8 and 7.C.10 of the HISTAR 190 SAR are considered, and the maximum source strength for each energy group of neutrons/gammas and the maximum cobalt activity are determined using the design basis source terms for the PWR WE 17x17, PWR CE 16x16 and BWR GE 10x10 fuel assemblies, as applicable. The established artificial but conservative source terms that bound the entire fuel specification up to the maximum allowable burnup are used in the shielding analysis for the HISTORE CISF.

RAI 75: Justify the adequacy of the 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> occupancy assumption in the calculation of the annual dose at the controlled area boundary.

Section 7.4.2.1 of the HISTORE SAR states that: [t]he maximum controlled area boundary dose rate (assuming an occupancy of 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> per year) is below the 25 mrem annual dose limit of 10 CFR 72.104. However, the SAR does not provide the basis for assuming 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> occupancy of a real individual at the controlled area boundary.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c).

Holtec Response:

Occupancy assumptions of a real individual located beyond the controlled area boundary are now changed, clarified, and justified to the extent practicable as described in more detail in response to RAI 17.

RAI 76: Justify that the calculated annual dose at 1000 meter is appropriate for demonstrating compliance with the requirements of 10 CFR 72.104 and 72.106.

Section 7.4.2.1 of the HISTORE SAR states that: [t]he nearest residence is 1.5 miles from the HISTORE CIS Facility. The dose calculations conservatively assume a fulltime resident (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />s/year) is only 1000 meters from the nearest loaded HISTORM UMAX VVM. However, Table 1.0.1 of the SAR, Overview of the HISTORE Facility, states that the distance from nearest loaded UMAX VVM to Site Boundary (Controlled Area Boundary) is 400 meters. These statements suggest that there is a discrepancy in the assumptions used to calculate the annual dose for a real individual at the controlled area boundary.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(a), (b) and (c).

Holtec Response:

Occupancy assumptions of a real individual located beyond the controlled area boundary are now changed, clarified, and justified to the extent practicable as described in more detail in response to RAI

17. Table 7.4.4 provides bounding HISTORE CIS Facility site accident conditions dose at 100 meters to meet the requirements of 10CFR72.106.

RAI 77: Demonstrate that the HISTORE CIS storage system design is sufficiently similar to that of the HISTORM UMAX design so that the analyses for HISTORM UMAX are applicable to the HISTORE CIS system.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Section 7.2.2.1 of the HISTORE SAR states that: [t]he version of the HISTORM UMAX storage system used here is slightly different from that described in [1.0.6]. However, the differences are minor, and do not affect the principal design features of the system. A discussion of the shielding design features of the storage system see Subsection 5.1.1 in [1.0.6]. This Subsection is incorporated here by reference.

However, there is no detailed comparison between design features of these two systems with respect to shielding design, particularly with respect to: (1) the authorized contents (e.g., PWR fuel burnup of 68.2 GWd/MTU for UMAX vs 45 GWd/MTU for HISTORE CIS), (2) the VVM design dimensions, (3) the materials used in the backfill materials (Controlled LowStrength Material (CLSM) in HISTORE CIS vs concrete and soil for UMAX (Table 5.3.2 of UMAX FSAR (ML14202A029)), and top cover shielding design, including the streaming paths formed by inlet and outlet vents.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(a) and (b).

Holtec Response:

The source terms used in the updated report bound the authorized contents of the HISTAR 190 SAR Appendix 7.C with respect to burnup, initial enrichment and cooling time, which is further detailed in Section 7.1 and Reference [7.1.1]. High burnup fuel, as it is allowed in the regionalized loading patterns in the HISTAR 190 SAR Appendix 7.C, is considered in the updated shielding analyses.

The design of the HISTORM UMAX Version C is provided in the licensing drawing package, drawing 10875, in Section 1.5 Licensing Drawings of the HISTORE SAR. The HISTORM UMAX Version B is considered in the UMAX Shielding calculations and yields lower dose rates than the UMAX Version A, which has dose rate tables in the UMAX SAR [1.0.6]. The UMAX Version B VVM and Version C VVM are geometrically identical, with the key difference being that the Version B uses stainless steel for certain items while these items for the Version C are carbon steel that may be painted or coated.

RAI 78: Justify that the dose rate calculations under accident conditions for the HISTORM FW HITRAC under accident conditions are applicable to the sitespecific HITRAC CS to be used at the HISTORE CISF.

Section 7.4.2.2 of the HISTORE SAR states that: [t]he only offnormal or accident condition applicable to the HISTORM UMAX storage system is the missile impact during construction next to a loaded canister. This condition is analyzed and modeled in Section 5.1 and 5.3 of the HISTORM UMAX FSAR.

However, the HITRAC CS for the HISTORE CIS uses concretefilled steel annular shells structure, whereas the shielding design of the HITRAC transfer cask described in the HISTORM UMAX System FSAR, referenced from the HISTORM FW FSAR, is comprised of a lead, water jacket, and steel shell structure. Therefore, the same accident may result in different damage modes and hence different dose rates for these two transfer cask designs. .

The staff also notes that Section 7.4.2.2 states that a separate shielding calculation for the HITRAC CS with assumption of substantially degraded concrete was performed. However, the SAR does not discuss the amount of concrete degradation assumed. The SAR should explicitly discuss and justify the amount of concrete degradation assumed in the shielding calculations for the HITRAC CS to demonstrate compliance with the regulatory requirements of 10 CFR 72.106.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(a) and (b).

Holtec Response:

The HITRAC VW analyzed in the HISTORM FW SAR, which has radial layers of steelleadsteelwater steel, is not used at the HISTORE CISF; therefore, accident conditions dose rates of the HITRAC VW are not applicable at the HISTORE CISF. The HITRAC CS, which has radial layers of steelconcretesteel is used at the HISTORE CISF, so accident conditions related to this transfer cask are relevant to the HI STORE CIS Facility SAR. For the bounding accident condition for the HITRAC CS, which is either burial under debris or a fire accident, any concrete that exceeds 1100oF is considered degraded, as mentioned in Chapter 4 and 6, and is not credited for shielding under accident conditions. Under the fire accident conditions, less than 1% of the total concrete volume is considered degraded, and under burial conditions less than 10% of the total concrete volume is considered degraded, which is detailed further in Reference [6.5.4] of the SAR. Although concrete degradation is not uniform down the length of the side of the HITRAC under the thermal accident, there are no localized radiation streaming paths that could increase dose rates beyond what is analyzed with the reduced concrete density in the accident conditions HITRAC CS model. Conservatively, the shielding analysis assumes a substantial loss of concrete areal density following the fire accident, with the density reduced from 3.05 g/cc (normal conditions) to 2.4 g/cc (accident conditions) or a decrease in total concrete areal density of 21.3% for accident conditions. HITRAC CS bounding accident conditions dose results demonstrating compliance with 10 CFR 72.106 are presented in Table 7.4.4.

RAI 79: Provide an assessment of the amount of Carbon14 that can be generated by neutron radiation of the air passing through the annular space between the canister and the VVM and an estimate of its contribution to the controlled area boundary dose.

Carbon14 (C14) is a radioactive material that can be produced by neutron irradiation of Nitrogen14, Oxygen16, and Oxygen17 that exists in the atmospheric air. For small ISFSIs, the generation of C14 is generally insignificant and, accordingly, the staff has not been concerned with its potential contribution to the dose to the general public and occupational workers inside or outside the controlled area boundary. However, larger spent fuel storage facilities, such as that proposed for the HISTORE CISF, could generate higher amounts of C14 during its operation. Accordingly, the SAR should provide an assessment or estimate of the amount of C14 that can be generated during its operation to determine its contribution to the total dose to workers and the general public.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), and (c).

Holtec Response:

The dose rate versus distance as a result of C14 production from a HISTORM UMAX system is documented in the new report HI2200954 R0. The results are used in HISTORE dose versus distance report (HI2177599 R2), and occupational dose report (HI2177600 R2), and discussed in the HISTORE storage SAR.

RAI 710: Provide justification for excluding the manufacturing tolerances for important to safety structures and components in the shielding analyses for the HISTORE CISF.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 The HISTORE CISF incorporates by reference the shielding analyses from the HISTORM UMAX System, specifically those in Chapter 5 of HISTORM UMAX FSAR, Rev. 1 (Holtec Report HI2115090). Section 5.3 of the HISTORM UMAX FSAR states that, [t]he nominal dimensions in these drawings were used to create the MCNP models used in the radiation transport calculations. However, the HISTORE SAR does not provide a justification for why this assumption is acceptable. More importantly, the HISTORE CISF VVMs and the HITRAC CS transfer cask (TC) have different geometries and dimensions than those assumed in the HISTORM UMAX FSAR. Specifically, the VVM storage module has different top lid design and the HITRAC CS TC is a new concrete shield design instead of a lead and water layer shield design of the HITRAC TC for the UMAX system.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(a) and (b).

Holtec Response:

For the staffs information, the following tolerances are standard manufacturing tolerances that are contained on Holtec fabrication drawings:

[

PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10CFR2390

]

These tolerances are controlled in manufacturing under Holtecs NRC approved QA program. The manufacturing drawings including these tolerances are similarly controlled, and any changes are evaluated under Holtecs process, which includes any necessary reviews by technical disciplines (i.e.,

shielding) and licensing.

These tightly controlled tolerances should provide reasonable assurance that there will be no drastic reduction in shielding, and keeping these tolerances on controlled manufacturing drawings and not in the FSAR is consistent across Holtec storage systems.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 711: Justify neglecting the contribution to the controlled area boundary dose from ISFSI loading and unloading operations or revise the estimated annual dose that includes the contribution from these operations.

The HISTORE SAR provides an estimate of the annual dose from the ISFSI loaded with 500 design basis casks. However, it is not clear why the dose estimates at the controlled area boundary do not consider the contribution to dose of ISFSI loading and unloading operations. Because the HISTORE CISF is designed to store up to 500 canisters in the initial phase, the SAR should provide a justification for why the doses from ISFSI loading operations, including loading of the canister into the transfer cask, moving the loaded transfer cask to the VVM, and unloading the canister into the VVM, do not make a substantial contribution to the dose at the controlled area boundary.

This information is necessary to determine compliance with 10 CFR 72.104(a), (b), (c) and 72.106(a) and (b).

Holtec Response:

Loading operations are now taken into account. The dose contribution from two loaded HITRAC CS transfer casks, and HISTAR 190 transportation casks are calculated and added to the annual dose sum to a real individual beyond the controlled area boundary in Section 7.4.

RAI 712: Clarify the statement in Section 7.4.2.2 of the HISTORE SAR regarding the offnormal and accident condition scenarios considered in the shielding analyses for the HISTORE CISF.

Section 7.4.2.2 of the HISTORE SAR states that: [t]he only offnormal or accident condition applicable to the HISTORM UMAX storage system is the missile impact during construction next to a loaded canister. This condition is analyzed and modeled in Section 5.1 and 5.3 of the HISTORM UMAX FSAR.

However, Section 15.2 and 15.3 of the HISTORE SAR lists all of the offnormal and accident scenarios that were considered and analyzed for the HISTORE CISF. The statement should be revised to either clarify that the scenario of missile impact during construction next to a loaded canister was the bounding scenario considered in the shielding analyses, or to otherwise reference that all other off normal and accident scenarios listed in Section 15.2 and 15.3 were bounded by it.

This information is necessary to determine compliance with 10 CFR 72.106(b).

Holtec Response:

The text is clarified in Section 7.4.2.2 to state that the scenario of missile impact during construction next to a loaded canister is the bounding accident scenario for the UMAX VVM.

RAI 111: Justify the exclusion of a sitespecific dose estimate for ISFSI excavation activities at the CISF.

Table 11.0.1 of the HISTORE SAR references the specific aspects of the HISTORM UMAX FSAR Radiation Protection evaluations that are incorporated by reference, as well as those that require additional site specific evaluations. Specifically, Table 11.0.1 states that [i]n the event, it is desired to expand the HI STORE CIS Facility's HISTORM UMAX VVM ISFSI, radiation protection of the excavation activities is achieved on a sitespecific level using the same prescription as in the generic case (i.e. prescribing a minimum distance between the excavation area and the loaded VVMs, as well as radiological monitoring

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 of the excavation area. The shielding design basis accident dose presented in the HISTORM UMAX FSAR for the HISTORM UMAX system demonstrates compliance with 10 CFR 72.106 [1.0.5] for the HISTORE CIS Facility. However, the staff could not find a sitespecific radiation protection evaluation and dose assessment for this type of site operation, especially with respect to a minimum distance between the excavation area, distance between pads and the loaded VVMs, as well as radiological monitoring of the excavation area, including whether the design basis accident dose presented in the HISTORM UMAX FSAR is still applicable to the HISTORE CISF.

This information is needed to determine compliance with 10 CFR 72.104(a), (b), (c), and 72.106(a) and (b).

Holtec Response:

The following text is added to the quoted section in the RAI of Table 11.0.1. All 500 UMAX VVMs will be constructed prior to loading any canisters into these storage systems. If at some point in the future, the facility plans to expand beyond 500 UMAX VVMs, an updated license application will be required to be filed with the NRC, which will consider radiation protection of the excavation activities.

RAI 112: Provide additional details and clear markings on the site map for the boundary of the Restricted Area, Radiation Areas, and High Radiation Areas and discuss specific access controls to these areas with radiation protection requirements.

Section 11.2.1 of the SAR states that, [c]ertain areas within the Restricted Area are designated as Radiation Areas, and specific locations within the Radiation Area share the potential to be High Radiation Areas and are posted and controlled in accordance with applicable requirements of 10 CFR

20. The applicant needs to clearly delineate the designated Radiation Areas, the boundary of Restricted Area, and the specific location for the High Radiation Areas in the site map.

This information is needed to determine compliance with 10 CFR 20.1302, 10 CFR 72.122(h), and 10 CFR 72.104.

Holtec Response:

The following text is added in section 11.2.:

The Protected Area perimeter is marked as the Restricted Area. The Cask Transfer Building is marked as a radiation area or high radiation area per 10 CFR 20 limits. The parking area for the loaded transportation casks, and the UMAX VVM ISFSI are marked as radiation areas. HISTAR Access controls is used to prevent unauthorized access to the Restricted Area for the purpose of radiation protection.

Physical barriers such as fencing and gates are used to prevent access to the Restricted Area with details outlined in the Physical Security Plan [3.1.1]. The provisions of 10 CFR 20.203 (b) or 10 CFR 20.1902 (a)

(b) [7.4.1] require that each radiation area and high radiation area be conspicuously posted with a sign or signs bearing the radiation caution symbol and the words: "CAUTION, RADIATION AREA" or CAUTION, HIGH RADIATION AREA, respectively. The restricted area and radiation areas are shown in Figures 11.2.1 and 11.2.2.

Access control is discussed further in Section 11.2.2.

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 RAI 141: Justify the assumption that no lowlevel radioactive wastes will be produced during site operations.

Section 14.1 of the HISTORE SAR states that: [r]adioactive wastes typically generated during operations at an ISFSI fall into the categories below. However, as discussed in Sections 14.3, 14.4, and 14.5, the HISTORE CIS does not generate radioactive wastes in any form during operations. Therefore, implicitly, the HISTORE CISF complies with the radioactive wastes and radiological impact criteria in 10 CFR 20 and 10 CFR 72. However, Chapter 3 and 10 of the SAR both state that specific surfaces of the canister and transportation cask will be swiped and tested for contamination. The wastes generated from these activities may create small amounts of lowlevel radioactive wastes and measures to ensure proper management and disposal of these wastes should be discussed in the SAR.

This information is needed to determine compliance with 10 CFR 72.44(d)

Holtec Response:

Holtec agrees that contamination surveys of the shipping cask and canister, which are performed during receipt inspection to verify surveys performed prior to shipment, have the potential to generate small amounts of lowlevel solid radioactive waste. This waste would be in the form of paper, cloth or other material used to perform checks for loosesurface contamination. The stated assumption that no low level radioactive wastes can be produced during site operations in therefore not correct. Facilities and procedures are therefore required to be established at the HISTORE CIS site to collect and prepare this potential solid waste for shipment to a licensed disposal facility. Sections 14.0, 14.1, and 14.4 of Chapter 14 are therefore revised as follows:

Section 14.0, First Paragraph:

Sig_,nificant uanhhes of radioactive wastes are not ex ected to be generated as ..a _result . of handling and storage oeerations for spent fuel or high-level waste @LW at the HI-STORE CIS site. Small volumes of solid low-level radioactive waste may be produced from routin contamination surveys and potential decontamination of transpo1tation casks and other equi ment surfaces. The canisters bearing SNF and other approved contents for storage in HI-STORM UMAX systems at the HI-STORE CIS serves as the confinement system during storage and related operations, as noted in Chapter 9 of this repo1t. There is no breaching or opening of the confinement canister during storage operations. The integrity of the confinement system has been proven via analysis to be maintained during normal, off-normal and hypothetical accident conditions as discussed in Chapters 9 and 15 of this report.

Section 14.1, First Paragraph:

HISTORE Consolidated Interim Storage Facility Requests for Additional Information Part 6 Attachment 2 Holtec Letter 5025061 Radioactive wastes typically generated during operations at an ISFSI fall into the categories ~

and b) below. As discussed in Sections 14.3, 14.4 and 14.5, the HI-STORE CIS bas the potential to generate small volumes of low-level solid radioactive waste from contamination smveys conducted durin o erations. There are no other sources for significant radioactive wastes. The HI-STORE CIS complies. with the radioactive wastes and radiol,o gical impact criteria in 10CFR20 and 10CFR72, as gaseous or liquid effluents are not generated onsite and provisions are made for the packaging of site-generated low-level solid waste in a form suitable for storagg onsite awaiting transfer to disQ_osal sites.

Section 14.4, First and Second Paragraphs:

As explained in Subsection 14.3, liquid waste (radioactive or non-radioactive) is not generated f!~..

a.result of facility normal operations and off-normal events as defined in Chapters 9 and 15 of this repo11. As such, solidified wastes esulting from liquid waste stream(s) are not generated at the HI-STORE CIS.

Transportation casks and canisters received at the site are expected to be free of loose surface contamination but are nonetheless smveyed for confirmation. Although unlikely, solid low-level adioactive wastes may therefore be generated at the HI-STORE CIS. typically consisting of paper or cloth swipes, paper towels, protective clothing, and other similar solid materials.

Subsequent to contamination surveys and confirmation of canister integrity during receipt, canisters ar transferred to the HI-STORM UMAX VVM usin a Q_rocess that at no time req!!_ires the canister o b opened and waste handled or treated. If breach of the canister is detected during receipt leak testing of the transpo1t cask and loaded canister, the package is transported back to the site of origin or other site authorized to handle the radioactive contents of the package for unloading and other remediation activities. Therefore, it is not expected that an)'l solid radioactive wastes will b generated as . a. result .of CIS facility operations. However, any low-level solid adioactive wastes that might be generated will be collected in containers and temporarily stored in an appropriate repository in the CTB. Small volumes of solid radioactive wastes are anticipated. These low activity wastes will be transpo1ted to, and disposed of at, a low-level

waste disposal facility licensed in accordance with 10CFR61 and in compliance with other applicable federal and state regulations.