ML19210D273
| ML19210D273 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 07/26/2019 |
| From: | Sharp S Northern States Power Company, Minnesota, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML19217A311 | List: |
| References | |
| L-PI-19-009 | |
| Download: ML19210D273 (233) | |
Text
1717 Wakonade Drive Welch, MN 55089 July 26, 2019 L-PI-19-009 10 CFR 72.56 ATTN: Document Control Desk Director, Division of Spent Fuel Management Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Prairie Island Independent Spent Fuel Storage Installation Docket 72-10 Materials License No. SNM-2506 License Amendment Request: Expand the Storage Capacity of the Independent Spent Fuel Storage Installation (ISFSI)
Pursuant to 10 CFR 72.56, Northern States Power Company, a Minnesota Corporation, doing business as Xcel Energy (hereafter NSPM), hereby requests a license amendment to Renewed Special Nuclear Materials (SNM) License No. SNM-2506 to increase the maximum amount of spent fuel that may be possessed and stored at the Prairie Island Independent Spent Fuel Storage Installation (PI ISFSI) as well as approval of the design of an additional concrete pad to be built within the confines of the existing facility utilizing alternate methods from those described in the existing PI ISFSI Safety Analysis Report (SAR) and Addendum, as described in Enclosure 1. The proposed change does not impact or request any changes to the type or characteristics of cask technology or spent fuel types authorized under SNM-2506 that may be stored within the PI ISFSI.
provides NSPMs evaluation of the proposed change. Attachment 1 to Enclosure 1 provides the markup of the PI ISFSI Renewed License SNM-2506 page. Attachment 2 to provides PI ISFSI SAR and Addendum pages for information only. Enclosure 2 provides a supplement to the PI ISFSI Environmental Report.
NSPM requests approval of the proposed amendment by August 26, 2020, with an implementation period of 90 days to support planning milestones for the construction of the expanded facility in 2021 and placement of additional casks in the PI ISFSI in 2022.
NSPM is notifying the State of Minnesota of this request by transmitting a copy of this letter and enclosures to the designated State Official.
Please contact Mr. Peter Gohdes at (612) 330-6503 or Peter.Gohdes@xenuclear.com if there are any questions or if additional information is needed.
fl Xcel Energy*
RESPONSIBLE BY NATURE~
Document Control Desk Page 2 Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
I declare under penalty of perjury, that the foregoing is true and correct.
Executed on July 2'=,, 2019.
~~9 Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (2) cc:
Administrator, Region Ill, USNRC Project Manager, Nuclear Material Safety and Safeguards, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota President of the Prairie Island Indian Community Tribal Council
ENCLOSURE 1 PRAIRIE ISLAND INDEPENDENT SPENT FUEL STORAGE INSTALLATION Evaluation of Proposed Change License Amendment Request Expand the Storage Capacity for the Independent Spent Fuel Storage Installation 1.0
SUMMARY
DESCRIPTION............................................................................................ 2 2.0 DETAILED DESCRIPTION............................................................................................. 2 2.1 Facility Description............................................................................................... 2 2.2 ISFSI Design and Operation................................................................................ 3 2.3 Current Licensing Basis Requirements................................................................ 4 2.4 Reason for the Proposed Change........................................................................ 6 2.5 Description of the Proposed Change................................................................... 6
3.0 TECHNICAL EVALUATION
............................................................................................ 9 3.1 Maximum Amount of Spent Fuel Assemblies....................................................... 9 3.2 Soil Liquefaction Analysis................................................................................... 13 3.3 Soil Structure Interaction Analysis...................................................................... 15 3.4 Structural Analysis............................................................................................. 23 3.5 Cask Heat Transfer Evaluation.......................................................................... 29
4.0 REGULATORY EVALUATION
..................................................................................... 34 4.1 Applicable Regulatory Requirements/Criteria..................................................... 34 4.2 Conclusions........................................................................................................ 37
5.0 ENVIRONMENTAL CONSIDERATION
........................................................................ 38
6.0 REFERENCES
............................................................................................................. 38 ATTACHMENTS
- 1.
Renewed License No. SNM-2506 (Markup)
- 2.
PI ISFSI Safety Analysis Report (Markup - For Information Only)
L-PI-19-009 NSPM Page 2 of 40 License Amendment Request Expand the Storage Capacity for the Independent Spent Fuel Storage Installation 1.0
SUMMARY
DESCRIPTION Pursuant to 10 CFR 72.56, Northern States Power Company, a Minnesota Corporation, doing business as Xcel Energy (hereafter NSPM), hereby requests a license amendment to Renewed Special Nuclear Materials (SNM) License No. SNM-2506 to increase the maximum amount of spent fuel to 1,049.60 TeU, equivalent to 64 fully-loaded Transnuclear, Inc. (TN)
TN-40/TN-40HT casks that may be possessed and stored at the Prairie Island Independent Spent Fuel Storage Installation (PI ISFSI) as well as approval of the design of an additional concrete pad to be built within the confines of the existing facility utilizing alternate methods from those described in the existing PI ISFSI Safety Analysis Report (SAR), as described in this enclosure. The proposed change does not impact or request any changes to the type or characteristics of cask technology or spent fuel types authorized under SNM-2506 that may be stored within the PI ISFSI.
2.0 DETAILED DESCRIPTION 2.1 Facility Description NSPM owns and operates the Prairie Island Nuclear Generating Plant (PINGP), which is a two unit plant located on the right bank of the Mississippi River within the city limits of Red Wing, Minnesota. Unit 1 began commercial operation on December 16, 1973, and Unit 2 began commercial operation on December 21, 1974. The PINGP Units 1 and 2 Renewed Facility Operating Licenses expire August 9, 2033, and October 29, 2034, respectively.
Discharged spent fuel assemblies from PINGP, Units 1 and 2, were originally intended to be stored on-site in a spent fuel pool. However, based on the fuel cycle management strategy and the limited spent fuel pool capacity, storage capacity was projected to be exhausted by 1994.
Consequently, NSPM requested permission on August 31, 1990, to build and operate an on-site ISFSI in compliance with 10 CFR 72. The NRC issued the original 20-year PI ISFSI site-specific license SNM-2506 on October 19, 1993 with an expiration of October 31, 2013.
On October 20, 2011, NSPM submitted an application pursuant to 10 CFR 72.42 for renewal of the site-specific PI ISFSI license. The NRC issued the renewed license on December 9, 2015.
The renewed license authorizes operation of the PINGP ISFSI in accordance with the provisions of the renewed license and its technical specifications. The renewed license expires on October 31, 2053.
Additionally, the Minnesota Public Utility Commission (MPUC) issued a Certificate of Need (CoN) on December 18, 2009, for the storage of up to 64 TN-40/TN-40HT casks to support
L-PI-19-009 NSPM Page 3 of 40 continued operation of PINGP Units 1 and 2 through the end of the renewed operating licenses.
2.2 ISFSI Design and Operation 2.2.1 Existing Facility The PI ISFSI consists of an approximately 5.5-acre area located west of the cooling towers within the PINGP owner controlled area. The ISFSI is surrounded by 8 ft. security and nuisance chain link fences. Within the storage area, casks are stored on two reinforced concrete pads which are nominally 36 ft. wide by 216 ft. long by 3 ft. thick. Each pad provides for two parallel rows of 12 casks, for a total of 24 casks per pad and 48 casks within the PI ISFSI. The concrete pads are surrounded by a gravel area that has been compacted to allow for movement and positioning of the Cask Transport Vehicle (CTV). In addition, a 17 ft. high earthen berm surrounds the ISFSI, except for the access road opening.
The Transnuclear, Inc., (TN) TN-40 and TN-40HT dry cask storage systems are authorized to be used at the PI ISFSI, in accordance with Renewed License SNM-2506 and its associated technical specifications. The TN-40HT cask is a modified version of the TN-40 dry cask and is designed for high enrichment and high burnup fuel. Both cask designs are capable of holding up to 40 spent fuel assemblies. There are 29 TN-40 casks and 15 TN-40HT casks located on the two existing ISFSI pads at the time of this application. Note that while a combination of TN40 and TN-40HT casks are stored in the PI ISFSI, the environmental report and related analyses used to support the ISFSI license renewal conservatively assumed the ISFSI stores 48 TN40HT casks, filled with design basis spent fuel. This assumption is bounding, as discussed in Section 4.11.2 of the NRC Final Environmental Assessment (Reference 1) associated with the PI ISFSI license renewal.
2.2.2 Expanded Facility Within the existing protected area of the PI ISFSI, NSPM will construct a third concrete storage pad. While the expansion entails constructing an additional concrete storage pad and an increase in the quantity of spent fuel stored in the PI ISFSI, the proposed change does not change the cask technology or spent fuel types authorized under PI ISFSI license SNM2506.
Consistent with the design of the existing pads, the new pad will have the design capacity to store 24 TN40/40HT casks arranged in two parallel rows of 12 casks. The new pad will be located within the existing ISFSI facility, approximately 38 ft. south of the existing eastern pad (Figure 2.2-1). The new pad will have a nominal thickness of 36 in. and will utilize a design consistent with the existing pads. The new pad will be the same length as the existing pads, but will be 40 ft. wide as opposed to the 36 ft. for the existing pads to allow for flexibility for application for and storage of alternate cask technologies in the future. However, the casks will be spaced and centered on the new pad the same as for the existing pads. The subgrade preparation for the new pad is the same as for the existing pads. The new ISFSI pad will be safety-related, Seismic Category I, consistent with the classification of the existing pads. The new ISFSI pad will include duct banks, underground conduits, and pull boxes for cask cover-seal pressure monitoring consistent with the existing ISFSI pads.
L-PI-19-009 NSPM Page 4 of 40 The design of the expanded ISFSI and supporting analyses described in this enclosure were performed by NSPM vendor Sargent & Lundy (S&L). The software used was validated per software verification and validation procedures which meet S&Ls 10 CFR 50 Appendix B Quality Assurance requirements.
Figure 2.2-1: Ariel View of the Location of the New ISFSI Pad Therefore, as the new pad design is consistent with the design of the existing pads, there is no impact to the associated design functions for the ISFSI pads or to any of the associated accident analyses described in the PI ISFSI SAR and Addendum.
2.3 Current Licensing Basis Requirements 2.3.1 Maximum Amount of Spent Fuel Assemblies NSPM is currently authorized to possess 715.29 TeU (metric tons of enriched Uranium) worth of spent fuel in the PI ISFSI. Renewed License No. SNM-2506, License Condition 8, describes the Maximum Amount That Licensee May Possess at Any One Time Under This License.
The maximum amount under License Condition 8 is currently limited to:
A.
715.29 TeU of spent fuel assemblies This corresponds to storage of 1,920 spent fuel assemblies in 48 TN-40/TN-40HT casks. The current total capacity of spent fuel allowed to be stored at the PINGP ISFSI of 715.29 TeU is based on storage of 482 Westinghouse standard assemblies (0.4 TeU/each), 481 Exxon t'i (1
I Ii J -* i
..... -...... ~"';... -... *--'....
L-PI-19-009 NSPM Page 5 of 40 standard and TOPROD assemblies (0.37 TeU/each), and 957 Westinghouse optimized design assemblies (0.36 TeU/each).
2.3.2 Soil Liquefaction Analysis Section 2.5.4, Stability of Subsurface Materials, of the ISFSI SAR, describes that a soil liquefaction analysis was performed for the existing ISFSI site based on standard penetration tests (SPT) borings from 1991 and a procedure developed by Seed, Seed, and Idriss (Committee on Earthquake Engineering, Commission on Engineering and Technical Systems, National Research Council, Liquefaction of Soils During Earthquakes, National Academy Press, Washington, D.C., 1985).
2.3.3 Soil Structure Interaction Analysis Section 4.2.1.2, Dynamic Analysis, of the ISFSI SAR describes that the soil structure interaction (SSI) analysis of the existing ISFSI pads used a set of soil springs to model the dynamic soil-structure interaction.
2.3.4 Structural Analysis Section 4.2.1, Structures, of the ISFSI SAR and Section A4.2.1, Structures, of the ISFSI SAR Addendum describe the structural analysis of the existing concrete pads. The finite element analysis verified that the strength of the pad was adequate to prevent unacceptable cracking or differential settlement and that the casks would not tip under design loads was performed using the finite element analysis computer program, IMAGES 3D, Version 1.6. The loads and load combinations were based on the guidance of ANSI/ANS-57.9-1984, Design Criteria for an Independent Spent Fuel Storage Installation (Dry Storage Type), (Reference 2),
as modified and described in the ISFSI SAR. The ISFSI SAR describes elements of the finite element analysis model and provides a description of the modelling approach. The ISFSI SAR also states that a maximum concrete compressive strength of 4,000 psi was used in the cask drop and tip accidents and that the concrete for the existing pads was designed for a nominal compressive strength of 3,000 psi at 28 days.
2.3.5 Cask Heat Transfer Evaluation Section A3.3.2.2.4.1.1, Storage Array Radiant Heat Transfer Evaluation, of the ISFSI SAR Addendum describes the methodology used to evaluate the change in radiant heat transfer due to a decreased view factor by comparing a simplified storage array model and the TN40HT detailed cask model. The SAR explains that a three dimensional model of TN-40HT casks in a storage array was developed using ANSYS in order to investigate the effects of the cask view factor on the thermal performance.
2.3.6 Aging Management Section 9.8, Aging Management, of the ISFSI SAR and Section A9.8, Aging Management, of the ISFSI SAR Addendum describe the aging management considerations for the ISFSI
L-PI-19-009 NSPM Page 6 of 40 conducted as part of the ISFSI License Renewal. An Aging Management Review (AMP) was conducted to identify the potential aging effects for structures, systems, and components (SSCs) including concrete pads, casks, and spent fuel assemblies. These SSCs are identified in the ISFSI Inspection and Monitoring Activities Program and the Time-Limited Aging Analysis (TLAA). As summarized in Section 9.8.3, Time-Limited Aging Analysis, of the ISFSI SAR, no TLAAs were identified for the TN-40 cask design, spent fuel assemblies stored in the casks, or concrete pads.
As summarized in Section A9.8.3, Time-Limited Aging Analysis, a review of the TN-40HT cask design and the spent fuel assemblies stored in the TN-40HT cask identified no TLAA for the spent fuel assemblies stored in the TN-40HT casks. However, two analyses for the TN-40HT cask design were identified as having all six attributes of a TLAA. The first TLAA is an analysis of the basket aluminum components deadweight compressive stresses taking into account the effects of material creep. The second TLAA is an evaluation of neutron damage of the cask metallic components due to fast neutron irradiation. The evaluations conducted demonstrated that the TLAAs are valid for the period of extended operation.
2.4 Reason for the Proposed Change The proposed amendment would increase the amount of uranium that NSPM may possess in the PI ISFSI. This increase reflects the change in the licensed life of the PINGP Units from an initial 40 years of operation to 60 years of operation. The original amount of uranium that may be possessed under this license was based on 40 years of operation of the PINGP Units.
Originally, 48 TN-40/TN-40HTs were planned to accommodate these fuel assemblies.
However, additional spent fuel assemblies will be generated during the additional 20 years of licensed operation. A federal repository remains unavailable at the time of this amendment request. There remains uncertainty regarding when Department of Energy (DOE) will be able to take possession of the spent fuel assemblies. Given the delays in developing a permanent repository, NSPM has utilized the existing spent fuel pools at PINGP to the extent practicable and provided a separate dry fuel storage facility in order to maintain safe storage of the spent fuel assemblies until their acceptance by DOE for transportation offsite. To ensure adequate fuel storage for the remainder of the licensed operating life of the PINGP Units, the additional storage capacity is being added to the PI ISFSI.
2.5 Description of the Proposed Change 2.5.1 Maximum Amount of Spent Fuel Assemblies NSPM requests NRC approval to allow for expansion of the PI ISFSI by increasing the maximum amount of spent fuel allowed under Renewed License No. SNM-2506 to an equivalent capacity of 64 TN40HT casks fully loaded with design basis spent fuel. Specifically, the proposed change increases the maximum amount of spent fuel allowed under Renewed License No. SNM-2506 to 1,049.60 TeU, by revising License Condition 8 as follows:
A.
715.29 1,049.60 TeU of spent fuel assemblies
L-PI-19-009 NSPM Page 7 of 40 This results in an increased total storage capacity to 2,560 spent fuel assemblies. As shown in the ISFSI SAR Addendum, Table A7.2-1, Prairie Island Fuel Assembly Design Characteristics, the Westinghouse Standard 14x14 fuel contains the maximum TeU per fuel assembly at 0.41 TeU/assembly. Therefore, taking this maximum calculated initial Uranium content of the fuel assemblies for which the TN-40HT cask is designed to accommodate and multiplying by the maximum number of fuel assemblies for 64 casks (2,560 fuel assemblies) results in the proposed total capacity of 1,049.60 TeU.
See Attachment 1 to this enclosure for the proposed markup to Renewed License No.
SNM2506. See Attachment 2 to this enclosure for the proposed markup to the PI ISFSI SAR and Addendum provided for information only.
2.5.2 Soil Liquefaction Analysis NSPM requests NRC approval to use an alternate method for the performance of the soil liquefaction analysis for the new pad that differs from the method described in the ISFSI SAR used in the design of the existing ISFSI. Alternatively, NSPM used an NRC-approved methodology in accordance with the guidance in NRC Regulatory Guide (RG) 1.198, Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites, Revision 0 (Reference 3), for performance of the soil liquefaction analysis of the new ISFSI pad.
A new section will be added to the ISFSI SAR describing the alternate methodology for the soil liquefaction analysis in the design of the new ISFSI pad. See Attachment 2 to this enclosure for the proposed markup to the PI ISFSI SAR and Addendum provided for information only.
2.5.3 Soil Structure Interaction Analysis NSPM requests NRC approval to use an alternate method for the performance of the SSI analysis, and supporting analyses, for the new pad that differs from the analyses described in the ISFSI SAR for the existing ISFSI. Alternatively, NSPM used NRC-approved methods consistent with NUREG0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 3.7.1, Seismic Design Parameters, Revision 4 (Reference 4), and Section 3.7.2, Seismic System Analysis, Revision 4 (Reference 5), as well as NUREG/CR-6865, Parametric Evaluation of Seismic Behavior of Freestanding Spent Fuel Dry Cask Storage Systems, (Reference 6), Appendix D of RG 1.132, Site Investigations for Foundations of Nuclear Power Plants. (Reference 7), RG 1.61, Damping Values for Seismic Design of Nuclear Plants, Revision 1 (Reference 8), and RG 1.92, Combining Modal Responses and Spatial Components in Seismic Response Analysis, Revision 3 (Reference 9), for performance of the SSI analysis and supporting analyses for the new ISFSI pad.
The Response Spectrum Generator (RSG), SHAKE2000, and SASSI2010 computer programs were used in the generation of artificial acceleration input motions, the free-field site response analysis, and the SSI analysis.
L-PI-19-009 NSPM Page 8 of 40 A new section will be added to the ISFSI SAR describing the alternate methodology for the SSI analysis, and supporting analyses, used in the design of the new ISFSI pad. See Attachment 2 to this enclosure for the proposed markup to the PI ISFSI SAR and Addendum provided for information only.
2.5.4 Structural Analysis NSPM requests NRC approval to use an alternate method for performance of the structural analysis of the new ISFSI pad. Additionally, NSPM also requests NRC approval to take exception to the 4,500 psi minimum compressive strength stipulated by ACI 318 for concrete durability.
In addition to meeting the requirements of the existing ISFSI pads, as described in the ISFSI SAR and Addendum, NSPM used the updated guidance in NUREG1536, Revision 1 (NUREG-1536), Standard Review Plan for Spent Fuel Dry Storage Systems at a General License Facility (Reference 10), as well as NUREG-1567, Standard Review Plan for Spent Fuel Dry Storage Systems (Reference 11), to develop the finite element analysis method model for performance of the structural analysis for the new ISFSI pad. These NUREGs provide details of loads, load combinations, and codes required for the design of the new pad.
Consistent with guidance in NUREG-1536, the new ISFSI pad design is based on the requirements in American Concrete Institute (ACI) codes, including ACI 318-08 (ACI 318),
Building Code Requirements for Structural Concrete and Commentary (Reference 12).
ACI 318 requires a minimum compressive strength requirement of 4,500 psi for concrete durability in Table 4.3.1, for Exposure Class F2. However, Section 4.2.1 of the ISFSI SAR contains a maximum concrete compressive strength requirement of 4,000 psi, which is subsequently used in Section 8.2.8, Hypothetical Cask Drop Accident. Alternatively, the compressive strength of the new pad was designed consistent with the existing pads, such that the specified compressive strength of the new ISFSI pad is between a minimum of 3,000 psi and a maximum of 4,000 psi. NSPM applied the requirements of ACI 201.2R-16, Guide to Durable Concrete, (Reference 13) to ensure the durability of the new ISFSI pad while still meeting the cask drop analysis requirements.
The computer program IMAGES 3D was used to perform the finite element analysis for the structural analysis of the existing ISFSI pads, as described in the ISFSI SAR. As IMAGES 3D is no longer maintained, the finite element analysis for the new pad was performed using computer program SAFE, Version 12.3.1. SAFE is a program used for designing flat slabs, foundation mats, spread footings, and combined footings based on the finite element method.
New sections will be added to the ISFSI SAR and SAR Addendum describing the alternate methodology for the structural analysis in the design of the new ISFSI pad. See Attachment 2 to this enclosure for the proposed markup to the PI ISFSI SAR and Addendum provided for information only.
L-PI-19-009 NSPM Page 9 of 40 2.5.5 Cask Heat Transfer Evaluation NSPM requests NRC approval to use an alternate method for performing the cask heat transfer thermal evaluation to analyze the expanded ISFSI. Alternatively, the thermal analysis uses computer program STARCCM+, Version 12.02, to utilize a computational fluid dynamics (CFD) model to evaluate the radiation heat transfer between the casks, ground, and environment. The STAR-CCM+ CDF model did not model air flow around the cask, similar to how the existing ANSYS model evaluated radiant heat transfer to account for the change in geometry due to the addition of the new pad to the PI ISFSI.
A new section will be added to the ISFSI SAR describing the alternate methodology for use of the CFD model to evaluate the impact on cask heat transfer due to the expansion of the storage capacity of the PI ISFSI. See Attachment 2 to this enclosure for the proposed markup to the PI ISFSI SAR and Addendum provided for information only.
3.0 TECHNICAL EVALUATION
3.1 Maximum Amount of Spent Fuel Assemblies 3.1.1 Criticality The proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI. Therefore, the construction of a new ISFSI pad and the increase in spent fuel to be stored at the PI ISFSI does not impact the criticality evaluation as described in the PI ISFSI SAR and Addendum.
3.1.2 Confinement Barriers and Systems The proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI. The new ISFSI pad will be provided with duct banks, underground conduits, and pull boxes for cask cover-seal pressure monitoring consistent with the existing ISFSI pads. Therefore, the construction of a new ISFSI pad and the increase in spent fuel to be stored at the PI ISFSI does not impact the confinement barrier and systems evaluation, as described in the PI ISFSI SAR and Addendum.
3.1.3 Thermal While the proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI, it does involve increasing the quantity of spent fuel stored within the PI ISFSI. Analyses have been performed to address the thermal impact of the addition of a third ISFSI pad, fully loaded with TN-40HT casks, on the existing ISFSI pads, fully loaded with TN-40HT casks. The analyses concluded that the increase in external temperature due to the expanded ISFSI would be less than 5 °F (see Section 3.5 of this enclosure for further detail). From existing analyses, the available margin for existing limiting temperatures per structure from existing cask thermal analyses:
L-PI-19-009 NSPM Page 10 of 40 Table 3.1-1: Cask Internal Component Thermal Acceptance Criteria Component Criterion:
Normal Max Allowable Temp
(°F)
Analysis Result:
Existing Analysis Temp.
(°F)
Difference:
Available Margin
(°F)
Seals 536 185 351 Neutron Shield 300 285 15 Fuel Cladding 752 680 72 Therefore, due to the existing margins for the selected representative internal cask components given in Table 3.1-1, the increase in internal temperature is not above allowable limits. Therefore, while the construction of a new ISFSI pad and the increase in spent fuel to be stored in the PI ISFSI results in an update to the thermal evaluation to account for the increase in temperature, the existing conclusions described in the PI ISFSI SAR and Addendum are not impacted.
3.1.4 Radiation Protection While the proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI, it does involve increasing the quantity of spent fuel stored within the PI ISFSI. As the TN-40/TH-40HT cask technology utilized in the PI ISFSI is not impacted by the proposed change, the cask technology will continue to meet NRC design criteria for direct radiation. Also, the engineering features and operating procedures for the ISFSI will ensure that occupational exposures remain ALARA. Analyses have been performed to address the radiological impact due to the addition of 16 TN-40HT casks in the ISFSI. Consistent with the existing dose analysis, the dose analysis performed for the ISFSI expansion utilizes the TN40HT cask and the bounding design basis source term.
The analysis concluded that the radiation dose to the general public will continue to meet regulatory limits during both normal and anticipated occurrences.
3.1.4.1 Dose Impact from the Increased ISFSI Storage Capacity A dose analysis has been performed to evaluate the radiation dose impact of increasing the maximum amount of spent fuel assemblies stored in the PI ISFSI. This analysis determined the offsite doses for the ISFSI given the storage of the 16 additional TN-40HT casks filled with design basis spent fuel, loaded in sets of four (4) casks every two (2) years. This is the same cask loading schedule as is applied to the analysis for the existing ISFSI.
As indicated in Section A3.3.5.3 of the ISFSI SAR Addendum, there are no credible events associated with use of the TN40HT casks which could result in releases of radioactive products or unacceptable increases in direct radiation. This determination remains true for the ISFSI with an increased total storage capacity to 64 TN-40HT casks. Therefore, the analysis for the addition of 16 TN40HT casks does not consider dose contributions due to radioactivity releases from the fuel-loaded and sealed casks during normal, off-normal, or accident situations. As such, the additional 16 casks will have no impact on the existing analyses.
L-PI-19-009 NSPM Page 11 of 40 In addition, the existing confinement analysis assumes only one cask is in the off-normal or accident condition. Since the TN-40HT cask with the design basis source term is also used for the expanded ISFSI, the existing confinement analysis does not need to be re-performed to allow the storage of spent fuel in TN-40HT casks on the expanded ISFSI. Therefore, the accident dose limits associated with 10 CFR 72.106 are not affected as a result of this analysis.
As dose contributions due to radioactivity releases from the fuel-loaded and sealed casks during normal, off-normal, or accident situations and the confinement analysis are not impacted by the proposed change, the only dose impact is to normal offsite doses. The offsite dose analysis for the expanded ISFSI determined the total normal operation radiation dose values at the nearest site boundary and at the nearest resident when including the dose contribution due to storage of the additional 16 casks in the expanded ISFSI (i.e., for a total of 64 TN-40/TN-40HT casks on the existing and expansion ISFSI pads). The results of this analysis demonstrate that the total normal operation radiation doses will be in compliance with regulatory requirements, as follows:
Table 3.1-2: Summation of 10 CFR 72.104(a) and 40 CFR 190.10(a)
Annual Dose (Nearest Resident)
Source Dose Contribution (mrem/yr)
Total (mrem/yr)
Limit (mrem/yr)
Margin (mrem/yr)
Existing ISFSI Capacity (Fully Loaded - 48 Casks) 2.38E+00 3.39 25.00 21.61 Additional ISFSI Capacity (16 Loaded Casks) 9.92E-01 Planned Discharges1 1.50E-02 1 Based on the PINGP, Units 1 and 2, 2017 Annual Radioactive Effluent Report (Reference 14). Note that discharges are not due to the ISFSI; no effluent releases are associated with the ISFSI.
Table 3.1-3: Summation of 10 CFR 20.1301(a)(1) Annual Dose (Nearest Resident)
Source Dose Contribution (mrem/yr)
Total (mrem/yr)
Limit (mrem/yr)
Margin (mrem/yr)
Proposed Licensed Operation (48 casks for the existing ISFSI with 16 additional casks for the ISFSI expansion, and planned plant discharges for PINGP, Units 1 and 2) 3.39 3.39 100.00 96.61
L-PI-19-009 NSPM Page 12 of 40 Table 3.1-4: Summation of 10 CFR 20.1301(a)(2) Dose Rate (Site Boundary)
Source Dose Contribution (mrem/hr)
Total (mrem/hr)
Limit (mrem/hr)
Margin (mrem/hr)
Existing ISFSI at Capacity (Fully Loaded - 48 Casks) 2.80E-01 0.40 2.00 1.60 Additional ISFSI Capacity (16 Loaded Casks) 1.19E-01 Other Sources1 0.00E+00
- 1. Other sources of radiation located on the PINGP site which could add to the radiation level at the ISFSI controlled area boundary are considered to be insignificant when compared to the radiation level associated with the spent fuel storage casks. This is consistent with the existing analysis.
Therefore, as the calculated dose values at the nearest site boundary and at the nearest resident meet the regulatory limits of 10 CFR 72.104(a), 40 CFR 190.10(a), and 10 CFR 20.1301(a), the addition of 16 TN-40HT casks to the PI ISFSI is considered to be acceptable with respect to the radiation levels at the nearest site boundary and at the nearest resident.
As a measure of additional conservatism, it was assumed in the dose analysis that the location of the new pad and additional casks is at the center of the existing ISFSI facility, between the two existing ISFSI pads. As the actual location of the new ISFSI pad will be further from the nearest resident than the center of the existing ISFSI facility, there will be no impact on the results of this analysis due to any chosen cask loading scheme. Therefore, this analysis will bound any distribution of 64 TN-40HT (or TN-40) casks across the 72 available storage locations of the three ISFSI pads.
Lastly, the NRC has previously considered the radiological impact from ISFSI expansion to accommodate up to 98 casks and concluded that such an expansion would not have a significant incremental contribution to cumulative impacts, as discussed in Section 4.14, Cumulative Impacts, of the NRC Final Environmental Assessment associated with Renewed License SNM-2506 (Reference 1). Therefore, the impacts considered in Reference 1 bound the proposed change to increase the maximum amount of spent fuel to an equivalent of 64 casks in this license amendment request.
3.1.5 Operations The proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI. The new ISFSI pad and additional spent fuel and casks have been evaluated and will be added to the ISFSI aging management program. Therefore, the aging management program is the only impact that the construction of a new ISFSI pad and the increase in spent fuel in additional casks to the PI ISFSI will have on the operations evaluation, as described in the PI ISFSI SAR and Addendum.
3.1.5.1 Aging Management The proposed change to increase the storage capacity of the PI ISFSI has been evaluated for aging management effects to manage the effects of the environment. While the proposed
L-PI-19-009 NSPM Page 13 of 40 change to increase the storage capacity of the PI ISFSI involves increasing the amount of spent fuel assemblies, adds additional casks, and involves construction of a new concrete pad, the additional spent fuel assemblies and casks are unchanged from those in the existing ISFSI and the new concrete pad is consistent with the existing ISFSI pads. Therefore, consistent with Section 1.4.6 of NUREG-1927, Standard Review Plan for Renewal of Specific Licenses and Certificates of Compliance for Dry Storage of Spent Nuclear Fuel, Revision 1 (Reference 15),
NSPM has determined that the in-scope SSCs and (associated subcomponents) described in the proposed change are already encompassed in the TLAAs and AMPs included in the specific-license renewal.
3.1.6 Maintenance The proposed change does not involve modification of the types of spent fuel or cask technology licensed to be stored within the PI ISFSI. Therefore, the construction of a new ISFSI pad and the increase in spent fuel in additional casks to the PI ISFSI, does not impact the maintenance evaluation, as described in the PI ISFSI SAR and Addendum.
3.2 Soil Liquefaction Analysis A soil liquefaction analysis was performed for the new pad in accordance with the guidance in RG 1.198, Revision 0, Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites, to reevaluate the potential for soil liquefaction at the PI ISFSI given an SSE. The analysis was based on the data of four sets of cone penetration tests (CPTs) from a new subsurface investigation performed in July 2018, data from the 1991 standard penetration tests (SPT) borings which were conducted for the existing ISFSI site, and data from a boring performed in August 2014 to support construction of the nearby FLEX Equipment Storage Building. The use of CPTs is an acceptable alternative method for obtaining subsurface information and evaluating liquefaction in accordance with the requirements in RG 1.198.
3.2.1 Design Inputs Two of the CPTs from the new subsurface investigation were taken at the location of the proposed new concrete pad southeast of the existing eastern pad. The other two CPTs were taken west of the location of the proposed new concrete pad and south of the existing western pad.
The following additional key design inputs were used in the development of the structural analysis:
- At each of the four CPT locations, the first six feet of the ground was vacuum excavated to avoid any underground utilities. Although the vacuum holes were backfilled with excavated soils, the ground condition was disturbed and the CPT data within the upper six feet was discarded. The maximum sounding depths for the four CPTs were to depths of up to 55.91 ft.
L-PI-19-009 NSPM Page 14 of 40
- The CPTs were supplemented with 1991 SPT boring data from a geotechnical investigation using soil borings that was performed for the existing ISFSI pads and as documented in the ISFSI SAR. Five of the original STP soil borings were located adjacent to the new ISFSI pad. These borings revealed the soil condition to a depth up to 60 ft.
- Additionally, the CPTs and 1991 SPT data were further supplemented with the borings conducted for the 2014 FLEX Equipment Storage Building. These were considered as the boring depth was to a maximum of 101 ft.
- The groundwater level was encountered at an elevation of 681 ft. based on the CPT data obtained in 2018.
- Based on the PI ISFSI SAR, the safe shutdown earthquake (SSE) event uses 0.12g as the peak horizontal ground acceleration, which was used in liquefaction analysis. Per a letter from the NRC to NSPM dated December 15, 2015, the NRC Staff Assessment confirmed that the SSE is defined at the surface (Reference 16).
3.2.2 Supporting Analysis and Acceptance Criteria The potential for the saturated subsoils to liquefy depends on its constituents, relative density, groundwater level, and the intensity of the earthquake. RG 1.198 provides procedures and criteria for assessing liquefaction potential at nuclear power plant sites.
The soil at the ISFSI site was screened using the bases contained within RG 1.198 to determine which soils were susceptible to liquefaction or not. For the PI ISFSI project site, the screening determined that potentially liquefiable soil types were present and that they could become saturated at some future date.
A numerical analysis was performed to establish the factor of safety (FS) against liquefaction.
In accordance with RG 1.198, the ratio of the shear resistance (CRR) of the soil under repetitive loading to earthquake-induced shear stresses (CSR) at various depths was calculated using both the CPT and SPT data. The ratio of CRR to CSR was then used to determine the factor of safety against liquefaction. In general, a site with subsoils having FS against liquefaction potential over 1.4 is acceptable. Otherwise, further evaluation and/or site mitigation would be required.
Post-earthquake settlement of sandy soils was also considered. The volumetric strain in soil layers due to the earthquake was determined followed by the settlement of each layer which was computed as the product of the volumetric strain and the layer thickness. The post-earthquake volumetric strain was determined as a function of factor of safety against liquefaction or maximum shear strain, and the relative density or CPT tip resistance.
L-PI-19-009 NSPM Page 15 of 40 3.2.3 Results and Conclusions Based on the results of the soil liquefaction analysis, the FS against liquefaction was calculated to be approximately 2.0 and greater in the subsurface profile based on the CPT method and greater than 1.65 with the SPT method using conservative approaches. All results were above the RG 1.198, Section 4.2, acceptance criteria of FS 1.4. Also, as the settlements of the dry sand layers were small (not subject to liquefaction), they were not factored into the analysis. Therefore, the new pad location was determined to not be susceptible to liquefaction and acceptable.
By taking into account the calculated factors of safety for the site, seismic induced settlement was considered to be minimal, such that the site is not considered to be susceptible to liquefaction and no further evaluation or site mitigation is required. However, for design, a conservative estimate of 0.5 in. of seismic induced settlement was considered to account for variations in the soil profile between test locations in the structural design analysis.
NSPM has concluded that the use of CPT and SPT data, in accordance with the methodology in RG 1.198, is an acceptable alternate method for obtaining subsurface information and evaluating soil liquefaction potential for the intended application. Note that site characterization and the evaluation of liquefaction potential is independent of the purpose of the structure at the site (i.e., whether it is a seismically-qualified ISFSI pad or some other seismically-qualified plant structure at the site).
Additionally, it is noted that the NRC found use of an approach consistent with RG 1.198 for the evaluation of soil liquefaction to be acceptable for ISFSIs, as documented in Section 2.1.6.4 of the Safety Evaluation Report (SER), dated November 2005, for the Humboldt Bay ISFSI (Reference 17). The methodology of RG 1.198 was also used to perform the evaluation of soil liquefaction potential for other ISFSIs, such as the Calvert Cliffs ISFSI per Section 2.6.4 of the Calvert Cliffs ISFSI Updated Safety Analysis Report (Reference 18).
3.3 Soil Structure Interaction Analysis Section 4.2.1.2, Dynamic Analysis, of the ISFSI SAR describes how the SSI analysis of the existing ISFSI pads used a set of soil springs to model the dynamic soil-structure interaction.
The design of the new ISFSI pad used updated NRC-approved methods in accordance with the guidance in NUREG0800, Standard Review Plan [SRP] for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Section 3.7.1, Seismic Design Parameters, Revision 4; and Section 3.7.2, Seismic System Analysis, Revision 4; as well as NUREG/CR6865, Parametric Evaluation of Seismic Behavior of Freestanding Spent Fuel Dry Cask Storage Systems; Appendix D of RG 1.132, Site Investigations for Foundations of Nuclear Power Plants; RG 1.61, Damping Values for Seismic Design of Nuclear Plants, Revision 1; and RG 1.92, Combining Modal Responses and Spatial Components in Seismic Response Analysis, Revision 3.
L-PI-19-009 NSPM Page 16 of 40 3.3.1 Design Inputs The RSG, SHAKE2000, and SASSI2010 computer programs were used in the generation of artificial acceleration input motions, the free-field site response analysis, and the SSI analysis.
The following key design inputs were used in the development of the SSI analysis:
- The nominal pad dimensions were used and the cask arrangement was 12 casks in 2 rows with a center-to-center cask spacing of 18 ft. in either direction. An average concrete compression strength of 3,500 psi was used for the SSI analysis based on discussion in Section 3.4.1 of this enclosure.
- The TN-40HT cask parameters were used as they bound the TN40. As described in Section A4.2.1.1 of the ISFSI SAR Addendum, the weight of the loaded TN-40HT cask was taken as 250,000 lbf.
- The design snow load is 50 psf per Section 3.2.4 of the ISFSI SAR. In accordance with SRP 3.7.2, the mass equivalent to 75% of the design snow load should be included in a SSI model. Therefore, the snow load of 37.5 psf was added to the weight of the pad in the SSI model.
- Recorded acceleration data from the Pacific Earthquake Engineering Research (PEER)
Strong Motion Database was used as seed input motions for generating the SSE response spectra consistent acceleration input motions.
- The SSE ground motion for the ISFSI pad are defined by a maximum ground acceleration of 0.12g in the horizontal direction and 0.08g in the vertical direction, as described in Section 3.2.3 of the ISFSI SAR.
- Sandstone bedrock is at 164 ft below grade per the PINGP USAR, Page E.2-4. The unit weight for the bedrock is taken as 148 lbs/ft3 per the PINGP USAR, Plate 4.1. The soil column used in this analysis is defined to 179 ft below grade.
- The groundwater level was encountered at an elevation of 681 ft according to soil analysis.
- As summarized in Section 3.2 of this enclosure, the ISFSI expansion pad site is not susceptible to liquefaction. Accordingly, the SSI analyses were performed without considering the effect of soil liquefaction.
L-PI-19-009 NSPM Page 17 of 40 3.3.2 Supporting Analyses and Acceptance Criteria 3.3.2.1 Generating Acceleration Input Motions The artificial (synthetic) acceleration input motions (two horizontal and one vertical) were generated per Approach 2, Option 1 of SRP 3.7.1 and general guidelines in Section 1.B of SRP 3.7.1.
Artificial (synthetic) acceleration input motions in the three orthogonal directions were generated from recorded seismic acceleration data from a PEER website and steps (3) through (7) described in Section 4.1.4, Time Histories for the Three Spectral Shapes, from NUREGCR/6865. NUREG-CR/6865 has additional steps regarding rotating horizontal seed input motions to the principal major and minor directions. However, this was not considered necessary in developing artificial acceleration input motions based on SRP 3.7.1 and the seed motions were used without rotating directions.
The acceleration input motion generation was performed using the RSG program. To avoid errors in the velocity/displacement input motions during integration of the acceleration records, the baseline corrections of acceleration input motions were performed in RSG based on the segmental baseline adjustment procedure in Nathan M. Newmark Consulting Engineering Services, A Study of Vertical and Horizontal Earthquake Spectra (Reference 19). Step 7 from NUREG-CR/6865 for cross correlation check was performed manually.
3.3.2.2 Free-Field Site Response The purpose of the free-field response analysis was to determine the SSE induced soil strain-compatible shear modulus and damping values at various soil depths. These strain-compatible soil properties were generated to be used in the subsequent SSI analysis of the new ISFSI pad. The analysis was performed using computer program SHAKE2000, Version 9.95.
SHAKE2000 was used to calculate the response of a horizontally layered linear viscoelastic system due to the vertical propagation of shear waves. Each layer was homogeneous and isotropic.
The control point elevation of the SSE input motions of the PINGP site is defined at the ground surface as defined in an NSPM "L-PI-14-028, PINGP Seismic Hazard and Screening Report (CEUS Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from [[Topic" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Accident|letter dated March 27, 2014]], in response to an NRC Request for Information (Reference 20). Accordingly, the free-field SSE time histories in two horizontal directions were applied at the ground elevation as an outcrop motion. The strain-compatible soil properties (shear modulus and damping) were obtained by averaging the corresponding properties obtained from the two analyses. For the vertical earthquake component (vertical SSE), the compression wave velocity for each layer was determined using the following equation:
= 2 2 1 2
L-PI-19-009 NSPM Page 18 of 40 Where:
= Poissons ratio of soil
= compression wave velocity
= strain-dependent shear modulus (or shear wave velocity)
The soil damping for the compression wave velocity (vertical direction excitation) was considered the same as the damping obtained from vertically propagating shear waves (horizontal direction excitations).
For soil below the groundwater table, the lower bound value of the compression wave velocity was used which was the compression wave velocity of water, equal to 4800 ft/sec. For soil above the groundwater table, when the computed values for the compression wave velocity of soil were smaller than 4800 ft/sec, adjustments were made to the Poissons ratio to achieve a compression wave velocity of 4800 ft/sec. However, the SASSI2010 recommends that a Poissons ratio greater than 0.48 must be avoided. Therefore, if a Poissons ratio greater than 0.48 was required to achieve a compression wave velocity of 4800 ft/sec, the Poissons ratio was set to 0.48 and the compression wave velocity was adjusted accordingly.
The free-field site response analysis was performed for the lower bound (LB), best estimate (BE), and upper bound (UB) soil properties. In accordance with SRP 3.7.2, the upper and lower bound values of the soil shear modulus were be defined using the following equations:
=
1 +
= (1 + )
Where:
= soil shear modulus best estimate
= soil shear modulus lower bound
= soil shear modulus upper bound
= coefficient of variation COV has a value of 0.5 for well-investigated sites and 1.0 for sites that are not well-investigated per SRP 3.7.2.
The relationship between the shear modulus and shear wave velocity was determined by the following equation:
=
/
L-PI-19-009 NSPM Page 19 of 40 Where:
= shear modulus
= unit weight
= gravity acceleration Per Appendix D, Spacing and Depth of Subsurface Explorations for Safety Related Foundations, of RG 1.132, at least one boring is required for each safety-related structure. For larger and heavier structures, at least one boring is required per 10,000 ft2. The number of boreholes for the new ISFSI pad site satisfies the requirements for larger and heavier structures in RG 1.132, and the soil profiles from the boreholes are consistent without anomalies or discontinuities (mostly clean sandy soils). Therefore, the PI ISFSI pad site is considered to be a well-investigated site and a COV of 0.5 is used in this analysis.
The estimated soil properties at low strain level for all three soil cases (LB, BE and UB), were used as inputs for SHAKE analyses. The low strain soil properties for the LB and UB cases were used as inputs for the SHAKE runs and the strain-dependent soil properties for the horizontal input motions were calculated by an iterative procedure from the SHAKE runs.
The strain-dependent shear moduli and damping values obtained from the free-field analysis were checked against the following requirements in SRP 3.7.2:
In no case should the LB shear modulus be less than that value consistent with standard foundation analysis that yields foundation settlement under static loads exceeding design allowables. The UB shear modulus should not be less than the BE shear modulus defined at low strain and as determined from the geophysical testing program. In no case should the material soil damping as expressed by the hysteretic damping ratio exceed 15 percent (NUREG/CR-1161).
The final soil column properties were subsequently used in the SSI analysis.
3.3.2.3 Soil Structure Interaction Analysis Soil-structure interaction analyses were performed using the SASSI2010 program, which computes the dynamic responses of a structure and soil during an earthquake, taking into account the radiation of energy of the wave propagating into the soil region around the structure. The SASSI2010 program has been previously used by the nuclear industry to evaluate the SSI effects on seismic response of the seismic Category I structures. The direct method (or flexible volume method) was used in the SSI analysis. From the SSI analysis, dynamic responses of freestanding casks were determined and the stability of casks was evaluated.
The SASSI2010 analyses were performed for the two horizontals and the vertical input motions separately. Accordingly, three directional responses were obtained from each analysis in one direction of earthquake motion.
L-PI-19-009 NSPM Page 20 of 40 To take into account the variations of the number and arrangement of casks on the new ISFSI pad, three cask loading patterns were considered in the analyses. Model 1 was for the case of a fully loaded pad to its design capacity (24 casks). Model 2 was for the case of the pad at half of its design capacity with the 12 casks all located on one side of the pad. Model 3 was for the case of a single cask on the corner of the pad. Models 2 and 3 were used to account for various stages of cask installation. Model 3 for the single cask on the corner of the pad was determined to be the governing loading case.
3.3.2.3.1 SASSI2010 Structural Model The HOUSE Module within SASSI2010 contained a structural model containing the concrete pad and casks with interaction nodes between the pad and soil.
The new ISFSI pad was modeled by 4-node thick shell elements. The mesh was proportioned to accommodate the layout of cask models with four points of contact at exterior edges of the cask base. The average mesh size was 2.25 ft. by 2.50 ft. The pad was meshed to have a minimum of four elements at the bottom of a cask and between adjacent casks and to have aspect ratios less than 2.0.
A material damping value of 2% was used according to Table 12.2-8 of the PINGP USAR. The PINGP USAR states that the damping value is applicable to both the operational basis earthquake (OBE) and the design basis earthquake (or SSE). However, this damping value is lower than the OBE damping for reinforced concrete in Table 2 of RG 1.61, which is 4%.
Section 1.2 of RG 1.61 provides a discussion on the use of SSE and OBE damping values for dynamic analyses and concludes that the use of OBE damping values is acceptable without further review. Therefore, the use of 2% damping for the pad satisfies both requirements of the PINGP USAR and RG 1.61.
The TN-40HT cask was modeled as a vertical massless beam element connecting the cask base node to Center of Gravity (CG) of cask. A lumped mass element was applied at the CG node with the fully loaded cask weight. No mass was assigned to beam elements.
Since the cask is treated as a rigid body with the lateral frequency of 57 Hz per Section A3.2.3.1 of PI SAR, the sectional properties of the beam element were calculated based on a natural frequency of 57 Hz. From the base node, four rigid spread beams span to the edge of the cask and were connected to the pad nodes. The spread beam elements were modeled as rigid beams. The spread beams were released at all four pad nodes in all three rotational degrees of freedoms to ensure that they did not provide any artificial rigidity to the pad under the cask. Similarly to the pad, the material damping value for the cask was conservatively set to the lower value of 2%.
3.3.2.3.2 SSI Analysis Cases A total of twenty-seven SSI analysis cases (three structural models, three soil profiles, and three directions of input motion) were analyzed for an uncracked concrete pad condition. In addition, nine SSI analysis cases (three structural models, UB soil profile, and three directions
L-PI-19-009 NSPM Page 21 of 40 of input motion) were analyzed for a cracked concrete pad condition. It was determined that the results of analysis runs with an uncracked concrete pad condition indicate that the UB soil profile is the governing soil profile. Based on this observation, only the UB soil profile was considered for the cracked pad condition.
3.3.2.3.3 Inequality Checks for Sliding and Overturning of Casks Inequality checks were used to prevent incipient sliding and overturning of the casks, which are consistent with Section A3.2.3.2 of the ISFSI SAR Addendum. Therefore, the FS for sliding and overturning were calculated using the following:
= ()
= ()
Where:
= weight of cask on a pad
= horizontal acceleration of the casks, which is calculated as the vector sum of two horizontal Zero Period Accelerations (ZPAs) from the analysis
= vertical acceleration of the cask, which is calculated as the vertical ZPA of casks at the center of gravity location
= coefficient of friction between cask in an upright position and concrete
= vertical distance to the center of gravity of casks
= radial distance to the center of gravity of casks In accordance with the ISFSI SAR, the FS against overturning and sliding shall be greater than 1.0. The comparison of the FS equations showed that the sliding check governs the stability checks. Accordingly, the inequality check for sliding was used to evaluate the seismic stability of the casks.
3.3.2.3.4 Pad Sliding Additionally, the FS for sliding equation in Section 3.3.2.3.3 of this enclosure was used to check the case of pad sliding.
3.3.2.3.5 Structure-Soil-Structure Interaction Effect on Existing Pad In order to determine the structure-soil-structure interaction (SSSI) effect between new and existing ISFSI pads, two interaction nodes were added in the SSI model at locations at the edge and center locations of the closest existing pad. Response spectra with 5% damping were developed at these interaction nodes for the critical soil profile and compared to provide a measure of the SSSI effect between the two pads. The selection of nodes on the closest existing pad (north-east pad) envelops any node on the further existing pad (north-west pad).
L-PI-19-009 NSPM Page 22 of 40 3.3.2.3.6 Additional Guidance The guidance of RG 1.92 was utilized to algebraically sum co-directional accelerations.
3.3.3 Results and Conclusions Thirty-six (36) SSI analyses using SASSI2010 were performed for the new ISFSI pad to assess the stability of TN-40HT casks stored on the pad during SSE and to determine the maximum accelerations of the pad and casks.
Results of the analyses are as follows:
(1)
Cask responses in terms of stability and maximum accelerations are governed by UB soil profile.
(2)
The minimum FS based on the inequality checks using maximum absolute accelerations are 1.494 and 1.300 for uncracked and cracked pad conditions, respectively. The calculated FS are conservative and meet the acceptance criteria of the ISFSI SAR.
(3)
Maximum seismic accelerations of the cask are 0.125g and 0.128g in the horizontal directions and 0.079g in the vertical direction.
(4)
Maximum seismic accelerations of the new ISFSI pad in the horizontal directions were enveloped by the peak ground accelerations. Accordingly, maximum seismic accelerations of the pad are 0.120g, 0.118g and the horizontal directions and 0.080g in the vertical.
(5)
Pad sliding was evaluated and the FS determined to be 2.19. Therefore, the pad was determined to not slide relative to the soil.
(6)
The SSSI effects between the new and existing pads were evaluated by comparing 5%
response spectra at the edge and center locations of the existing pad with the free field response spectra. Overall the response spectra for the edge and center locations of the existing pad match well with the response spectra for the free field and the exceedances greater than 10% occur at narrow frequency ranges where maximum amplifications are not expected. Therefore, the SSSI effect will not affect the free-field seismic response of the existing pads.
Based on the above information, NSPM has concluded the use of current nuclear industry programs to perform more advanced SSI analyses, consistent with the current NRC guidance, is an acceptable approach to perform the SSI and supporting analyses for the design of the new ISFSI pad.
L-PI-19-009 NSPM Page 23 of 40 Additionally, although programs such as SASSI2010 and SHAKE2000 have not explicitly been approved by the NRC for use in the design of ISFSI pads, their use to perform SSI and supporting analyses for Seismic Category I structures has been acceptable to the NRC for new reactor combined operating license applications (COLAs), based on the Safety Evaluations for Fermi 3 and North Anna 3, and for the construction permit for SHINE medical radioisotope production facility (References 21, 22 and 23). Note that the regulatory guidance discussed above (e.g., SRP Section 3.7.1) has been used in the approval of cask designs. For example, Sections 3.4.3.7 and 3.5 of the NRC SER for the HI STORM UMAX Canister Storage System discuss the use of SHAKE2000 and LS-DYNA to perform SSI analysis and how the structural analyses were acceptable to the staff, respectively (Reference 24). It is also noted that the use of SASSI (an older version of SASSI2010) to perform SSI analysis was previously considered acceptable, as discussed in the NRC SER for the HI STORM 100 Cask System (Reference 25).
3.4 Structural Analysis The purpose of the static analysis was to design and to demonstrate the structural adequacy of the new ISFSI pad to support the loads associated with the storage of the casks, movement of the CTV carrying spent fuel casks, and loads associated with the applicable natural phenomena and man-made accidents for the PINGP site. As described in the PI ISFSI SAR, the static analysis of the existing ISFSI pads was conducted using the finite element analysis computer program, IMAGES 3D, Version 1.6. As IMAGES 3D is no longer maintained, the SAFE program, v12.3.1, was used for the design of the new pad. In addition to meeting the requirements of the ISFSI SAR for the existing ISFSI, the design of the new ISFSI pad used the updated guidance in NUREG-1536, Revision 1, Standard Review Plan for Spent Fuel Dry Storage Systems at a General License Facility, and NUREG-1567, Standard Review Plan for Spent Fuel Dry Storage Systems.
3.4.1 Design Inputs SAFE is a computer program used for designing flat slabs, foundation mats, spread footings, and combined footings based on the finite element method.
In accordance with Section 5.4.3.2 of NUREG-1567, the storage pad was designed and will be constructed as a foundation. Consistent with the guidance in NUREG-1536, Revision 1, the new ISFSI pad design is based on the requirements in ACI 349 and ACI 318. Specifically, ACI 349-13, Code Requirements for Nuclear Safety-Related Concrete Structures and Commentary (Reference 26), and ACI 318-08, Building Code Requirements for Structural Concrete and Commentary, were used in the design of the new ISFSI pad.
The new ISFSI pad was designed to 3,000 psi and 4,000 psi minimum and maximum compressive strengths. Section 4.5, Classification of Structures, Systems and Components, of the ISFSI SAR states, in part, [t]hose items related to the concrete storage pads which are classified as safety related are designed, installed, inspected and tested in accordance with the specific requirements of the American Concrete Institute (ACI) and American Society for Testing and Materials (ASTM). However, the specific ACI codes used to design the existing
L-PI-19-009 NSPM Page 24 of 40 ISFSI pads are not described in the ISFSI SAR or its addendum. As discussed in ISFSI SAR Section 4.2.1, the cask drop analyses for the TN-40 and TN 40HT cask designs, respectively, are based on a maximum compressive strength of 4,000 psi. As described in the PI ISFSI SAR, the existing ISFSI pads were designed with a specified minimum concrete compressive strength of 3,000 psi at 28 days. For the new ISFSI pad with an exposure rating of F2, ACI 318 specifies in Table 4.3.1 a minimum compressive strength of 4,500 psi for durability. As the cask drop analysis for the TN-40HT cask design is based on a maximum compressive strength of 4,000 psi, exception is taken to the 4,500 psi minimum compressive strength, such that the specified compression strength of the new ISFSI pad is 3,000 to 4,000 psi. The lower bound compressive strength of 3,000 psi was used in the structural analysis. As an alternative to the ACI 318 durability requirements, NSPM applied the requirements of ACI 201.2R-16, Guide to Durable Concrete, to ensure the durability of the new ISFSI pad while still meeting the cask drop analysis requirements.
ACI 201.2R is the current state-of-the-art with regards to concrete durability design and it provides more detail on concrete durability than ACI 318 and ACI 349, though these take considerations from the ACI 201 Committee into account. Per ACI 201-2R, durability against freeze-thaw is primarily controlled by three items: reducing freezable water (lowering water-cement ratio), entraining air to provide voids for water to expand into while freezing, and detailing to avoid standing water. The new ISFSI pad design follows the durability suggestions of ACI 201-2R for Exposure Class F2 freeze-thaw protection and provides a reasonable approach to ensure durability while still meeting the cask drop analysis requirements. Note that the air entrainment requirements of ACI 201-2R exceed those of ACI 318. Additionally, as discussed in Section 3.1.5.1 of this enclosure, the new ISFSI pad will be included in the ISFSI aging management program. As such, exception to the 4,500-psi minimum compressive strength stipulated by ACI 318 for concrete durability is acceptable.
The following additional key design inputs were used in the development of the structural analysis:
- The TN-40HT cask parameters were used in the design of the new pad as they bound the TN40. As described in Section A4.2.1.1 of the ISFSI SAR Addendum, the weight of the loaded TN-40HT cask was taken as 250,000 lbf.
- The empty weight of the CTV was factored into the analysis at 140,000 lbf. Note that Section 4.2.1.1, Static Analysis, of the ISFSI SAR describes how the original analysis used a weight of 150 kips for the CTV. The original CTV has recently been replaced, so the weight used in the new analysis is the weight of the new CTV.
- Soil parameters beneath the ISFSI pad for both static and dynamic (seismic) load cases were used. As there is no liquefaction potential for the ISFSI site, no reduction in soil modulus was required. The static subgrade modulus is used for all load cases. It is recognized that use of the static subgrade modulus for transient loading is conservative since transient loads have a higher subgrade modulus, which would lead to lower forces and moments in the pad.
L-PI-19-009 NSPM Page 25 of 40
- Reinforcing bar diameters and areas were determined using Appendix E of ACI 318-08.
- Results of the SSI analysis for the new pad and the surrounding soil were used. The enveloped accelerations determined from the SSI analysis of the pad and casks were conservatively increased to provide added margin. Therefore, the maximum horizontal and vertical accelerations used in the structural analysis were both 0.25 g.
3.4.2 Supporting Analysis and Acceptance Criteria The finite element analysis design model consisted of slab elements supported by subgrade springs. The slab elements were modeled as four-node, isotropic, rectangular thick-plate shell elements that combined membrane and plate-bending behavior. The finite element mesh was defined to have maximum dimensions of 2ft. x 2ft. which were automatically generated by SAFE. Shell elements were used for modeling the concrete pad and subgrade springs were used for the modeling of the supporting soil, which is consistent with the analysis approach in Section 4.2.1 of the ISFSI SAR.
The casks were not explicitly modeled in the SAFE design model. Instead, vertical forces and overturning moments induced by the casks were calculated and applied directly as vertical pressures to the concrete pad. Since wind or seismic loading does not cause uplift or tipping of the casks, the bearing pressure distribution under the casks due to wind or seismic loading was considered to vary linearly. However, for the case when lateral forces from a horizontal tornado missile impact cause uplift of a cask, the cask was considered to be tilted about its outer edge and the loaded pad area is reduced to a smaller area accordingly.
A total of four different cask load configurations were considered in order to envelope the worst-case moment, shear, and settlement in the new pad. Cask load configurations representing unbalanced cask loading patterns, which are critical for developing unbalanced moment and shear forces, were considered. Also, included were single and full cask loading configurations. Cumulatively, the cask loading patterns considered bound any other cask loading pattern.
The CTV locations were chosen to maximize shear and moment on the pad. For the tornado load cases, the tornado missile loads were also placed at the same cask location as the CTV loads.
3.4.2.1 Description of Loads The loads required for the new ISFSI pad design were as specified Table 3-2 of NUREG-1536.
Table 3.4-1 below contains the applicable loads from NUREG-1536 that were used in the structural analysis:
L-PI-19-009 NSPM Page 26 of 40 Table 3.4-1: Summary of Load Terms for ISFSI Pad Design Load Symbol Load Term Load Description D
Dead Load Weight of reinforced concrete pad Loads due to differential settlement L
Live Load Weight of storage cask(s) (effects of variations in case storage patterns is considered)
Weight of CTV Normal and offnormal impact load due to cask setdown Rain, snow, and ice loads W
Wind Loads Wind loads produced by normal and offnormal maximum winds Wt Tornado Loads Loads due to tornado wind pressure and tornadogenerated missiles T
Thermal Load
- Thermal loads resulting from thermal gradient within the pad Expansion & contraction joint temperature changes F
Hydrological Loads Loads due to flooding caused by extreme natural phenomena E
Earthquake Loads Seismic loads due to safeshutdown earthquake (SSE)
A Accident Loads Loads due to postulated cask drop accidents Loads due to nearby explosions H
Lateral Soil Pressure Static lateral soil pressure resulting from groundwater, weight of earth, and loads external to the structure transmitted to the structure by lateral earth pressure Does not include earthquake lateral loads included in E Ta Accident Level Thermal Loads Thermal loads resulting from accident, fire, or natural phenomenon 3.4.2.2 Load Combinations The load combinations were as specified in Table 3-3 of NUREG-1536 and used load factors that aligned with Appendix C of ACI 349. Therefore, the reduction factors in Appendix C of ACI 349 were used. Removing the duplicate load combinations and the load combinations with lower load factors, the final load combinations used in the pad design were:
Normal Events Accident-Level Events
> 1.4+ 1.7
> + +
> + + *
> + +
Where:
= reinforced concrete available strength
- For the case with upward vertical seismic acceleration, a 0.9 factor was applied to the dead load to create the worst-case uplift on the pad per NUREG-1536, Table 3-2.
L-PI-19-009 NSPM Page 27 of 40 Additionally, Table 3-3 of NUREG-1536 specifies several load combinations for evaluation of overturning and sliding (O/S). An additional load combination per Section 4.2.1 of the ISFSI SAR was also considered to check O/S for the flooding condition. The O/S load combinations used in the pad design were:
Accident-Level Events
/1.1(+ + )
/1.1(+ ++ )
/1.5(+ + )
These final load combinations were permutated to account for the various cask configurations, wind directions, tornado missile directions, and/or SSE seismic input forces. All permutations of each combination were then input into the SAFE design models.
3.4.2.3 Design for Shear and Flexure The design of the new pad for shear and flexure was performed by running the SAFE finite element model for the various cask load configurations and combinations. The shears and moments were calculated within the SAFE model based on user-defined design strips. The design strips can be defined up to an effective width of approximately 13 ft. Design strips were defined to be centered on the ISFSI casks in the SAFE model, similar to how column strips are defined for floor slab systems. Moment and shear forces acting in middle strips between column strips were not considered in the pad design since the forces in the middle strips are less critical than those in the column strips.
The design strip method used in SAFE averages shears and moments across the effective width of the design strip. Consideration of an uncracked section results in a stiffer slab in the SAFE model. With a continuous soil support, a stiffer slab will collect more load and moment, which will produce localized areas of concentrated shear and moment. Uncracked section properties were used in the SAFE model.
The factored shears and moments for all load combinations and design strips were output from SAFE in order to be evaluated against the shear capacity and moment capacity of the slab.
The design moments were calculated by the Concrete Design function in SAFE, which took into account the Wood-Armer method, as shown in the following equations:
,= +/-+/-
,= +/-+/-
Where:
= design moment for design strips aligned in the north-south direction,
= factored bending moment for design strips aligned in the north-south direction
L-PI-19-009 NSPM Page 28 of 40
= factored twisting moment for design strips aligned in the north-south direction
= design moment for design strips aligned in the east-west direction
= factored bending moment for design strips aligned in the east-west direction
= factored twisting moment for design strips aligned in the east-west direction In accordance with NUREG-1536, the acceptance criterion for the design of the pad for shear and flexure was that the capacity/demand > 1.00.
3.4.2.4 Maximum Soil Bearing Pressure Evaluation The maximum soil bearing pressure was evaluated to ensure that it is less than the allowable soil bearing pressure capacity provided in the analysis completed to determine the soil parameters beneath the new ISFSI pad for both static and dynamic cases. Maximum soil bearing pressure was determined from the SAFE output for all load combinations, but with factors of 1.0 used on all load terms (soil bearing pressure is an allowable stress criterion).
3.4.2.5 Sliding and Overturning (Pad and Casks)
The ISFSI pad was previously evaluated for sliding due to lateral forces caused by the SSE in the SSI analysis and concluded the pad and casks do not slide or uplift during an SSE.
For the tornado wind cases (ignoring missile impact), Section A3.2.1.2.1 of the ISFSI SAR Addendum states that tornado wind will not slide the cask or cause it to tip. For missile impact, Section A3.2.1.2.2 of the ISFSI SAR Addendum states that the cask will slide approximately 1.1 in. or tilt 0.3° (the center of gravity lifts about 0.3 in.). Since these displacements are much less than the spacing between casks, tornado missile impact is acceptable from a cask stability standpoint.
Tornado wind pressure was determined to govern over accidental explosion overpressure.
Therefore, the cask is also stable when impacted by accidental explosion overpressure.
3.4.3 Results and Conclusions The tabulated results of the analysis are as follows in Table 3.4-2:
L-PI-19-009 NSPM Page 29 of 40 Table 3.4-2: Summary of Results for New ISFSI Pad Failure Mode Interaction Coefficients Applied Allowed Through-Thickness Shear of Pad 0.52 17.3 kip/ft 33.4 kip/ft Moment, Bottom Face Reinforcement, North-South 0.58 115.4 kip-ft/ft 199.1 kip-ft/ft Moment, Bottom Face Reinforcement, East-West 0.64 134.6 kip-ft/ft 209.0 kip-ft/ft Moment, Top Face Reinforcement, North-South 0.39 53.8 kip-ft/ft 136.5 kip-ft/ft Moment, Top Face Reinforcement, East-West 0.71 100.0 kip-ft/ft 141.6 kip-ft/ft Static Bearing Pressure 0.53 2100 psf 4000 psf Transient Bearing Pressure 0.29 2300 psf 8000 psf The analysis concluded that the new pad is acceptable for its design loading. Sliding and overturning analysis results are also acceptable, there is no net uplift on the pad for any loading condition, and the pad stability is maintained for the maximum differential settlement.
Additionally, the cask drop parameters evaluated for the existing ISFSI pads are met by the new ISFSI pad as the new pad will represent a target of similar or lesser stiffness than the original ISFSI pads. Therefore, the existing cask drop analysis remains valid for the new ISFSI pad.
Additionally, a benchmark was also performed that analyzed the existing ISFSI pads using SAFE and the results were compared to the IMAGES 3D results in the analysis of record. The SAFE model was developed using the same parameters and finite element mesh layout as the IMAGES 3D model, except for a small difference in the modeling technique used for the construction joints. To allow moment release along joints, the IMAGE 3D model used springs with an arbitrary stiffness in three orthogonal directions to connect coincident nodes. On the other hand, the SAFE model uses the moment release capability of SAFE program. Because of the difference in the modeling techniques for construction joints, small difference in the analysis results is anticipated. The pad was analyzed using three cask loading configurations.
The comparison of the maximum concrete stresses in a critical element shows that the differences in stresses are negligible and, therefore, the PC program SAFE results are comparable to those from the IMAGE 3D program.
An older version of the SAFE program was used in the analyses to support the South Texas 3 and 4 combined operating license application (COLA) (Reference 27) and the associated verification and validation documentation was audited by the NRC (References 28 and 29).
3.5 Cask Heat Transfer Evaluation Analyses to address the thermal impact of the new ISFSI pad, fully loaded with TN40HT casks, on the existing ISFSI pads, fully loaded with TN40HT casks, were performed. These
L-PI-19-009 NSPM Page 30 of 40 new analyses are based on the location of the new ISFSI pad being 38 ft. south of the existing east ISFSI pad with a minimum new cask centerline to existing cask centerline distance of 58 ft.
3.5.1 Design Inputs The effect on the average cask surface temperature due to the addition of a new ISFSI pad was analyzed using a CFD model developed in STAR-CCM+, Version 12.02. STAR-CCM+ is a commercially available computer code developed by Siemens Product Lifecycle Management Software Inc.
The following key design inputs were used in the development of the SSI analysis:
- These new analyses are based on the location of the new ISFSI pad being at least 38 ft.
south of the existing east ISFSI pad with a minimum new cask centerline to existing cask centerline distance of 58 ft.
- The TN40HT cask parameters are bounding with respect to fuel burnup and decay heat and used in the analysis.
- Per the existing ISFSI thermal analysis, the film temperature of air in proximity of the side of the casks is approximately (100°F + 300°F)/2 = 200°F. Thus, properties of air at 200 °F were used in the model for the computation of the natural convection heat transfer coefficient.
- For both casks and ground, as the effective actual thermal conductivity is not known, the analyses considered three parametric runs with values ranging from 0.5 W/m-K to 5.0 W/m-K in order to envelop typical expected values.
3.5.2 Supporting Analysis and Acceptance Criteria The effect on the average cask surface temperature due to the addition of a new ISFSI pad was analyzed using a CFD model developed in STAR-CCM+. This model evaluated the radiation heat transfer between the casks, ground and environment and did not model air flow around the cask, similar to how the ANSYS model evaluated radiant heat transfer.
L-PI-19-009 NSPM Page 31 of 40 Figure 3.5-1: Cask 5 Relative to Emitting Cask (from ISFSI SAR Addendum Figure A3.3-20)
A review of the existing cask thermal analyses concluded that the addition of the new ISFSI pad results in a reduction of the view factor used in determining the radiation heat transfer coefficient from the cask to the atmosphere, which increases the emitting cask temperature.
The thermal analysis for the existing ISFSI determined the view factor for a cask alignment of two rows of infinite length, which is conservative for the existing configuration. As shown in Figure 3.5-1 taken from the ISFSI SAR Addendum Figure A3.3-20 in part, and as described in the existing analyses, the view factors from the emitting cask to the casks beyond the fifth offset cask (cask 5 in Figure 3.5-1) are less than 0.002 and are therefore not considered in the analysis due to their negligible effect. Note that the distance from the emitting cask to the fifth offset cask bounds the distance between the closest cask on the existing north-west ISFSI pad and the new ISFSI pad. Therefore, the new ISFSI pad installation does not affect the calculated view factors in the detailed TN40HT cask model.
Consistent with the methodology used in existing thermal analysis, a CFD model was created to model the radiation heat transfer between the casks, ground, and environment. Convection was also modeled as a boundary condition, i.e., air flow around the cask was not modeled.
Although heat conduction through the casks and ground was also included in the models, only the temperature distributions on the outer surfaces of the casks were to be regarded as valid results since the internal details of the casks and conduction heat transfer through solid casks were modeled in a simplified manner. Since internal details of the casks were not considered in the existing analysis, a simplified model using solid cylinders was generated for the CDF model. For both casks and ground, the effective actual thermal conductivity is not known, so this analysis considered three parametric runs with values ranging from 0.5 W/m-K to 5.0 0 0 0 0 8 0 00 o
- 80 0 0 40 sO 18' Emitting Cask 0
Receiving Cask Q Covered Cask
L-PI-19-009 NSPM Page 32 of 40 W/mK in order to envelop typical expected values. The CFD model was discretized in approximately 300,000 cells and considered the following two models:
- 1.
One set of two rows of casks,
- 2.
Two sets of two rows of casks with pads spaced 38 ft. apart.
The purpose of the first model was to create a model similar to the main body of the existing ISFSI thermal analysis to benchmark against the results documented in the existing ISFSI thermal analysis.
The natural convection heat transfer coefficient on the side of the casks and on the ground was based on the definition of the Rayleigh number:
= 3
Where:
= gravitational acceleration
= air thermal expansion coefficient
= difference between the surface temperature and free stream air temperature
= characteristic length of the surface
= gravitational acceleration
= air thermal diffusivity The heat transfer coefficients for a vertical flat plate (casks side) and a hot horizontal plate facing upward (ground) are specified through the Nusselt number based on the following definitions:
Vertical plate:
= 0.131/3 when Ra>109 (turbulent)
Cold horizontal plate facing downward: = 0.151/3 when Ra>107 (turbulent)
Using these relationships and an average temperature difference of approximately 100 °F to 200 °F between air and cask/ground temperature, the natural convection heat transfer coefficient is computed as follows:
=
= 1/3 Where:
= air thermal conductivity
= characteristic length of the surface
= constant that can be estimated from the CFD results
L-PI-19-009 NSPM Page 33 of 40 For h in W/m2-K and T in K, the following heat transfer coefficients are derived and specified for the cask sides and ground, respectively:
= 1.32()1/3
= 1.53()1/3 The acceptance criteria used was based off comparison to the results of the existing thermal analysis. From the storage array model results used for the existing thermal analysis, the maximum cask outer shell temperature is 276 °F and the average cask outer shell temperature is 260 °F.
The results of the CFD model to evaluate the increase in the cask exterior temperature for a different geometry of casks were subsequently used to scale the results of existing analyses.
3.5.3 Results and Conclusions The results of the CFD analysis are summarized below:
Table 3.51: CFD Results Thermal Conductivity of Cask /
Ground (W/m-K)
Cask Maximum Temperature
(°F)
Casks Average Temperature
(°F)
Temperature Difference (°F)
Cask Maximum Cask Average One set of two rows 0.5 271.8 257.2 Reference Value Reference Value Two sets of two rows
- 38 ft. apart 0.5 274.6 258.7
+2.8
+1.5 One set of two rows 2.5 270.7 257.0 Reference Value Reference Value Two sets of two rows
- 38 ft. apart 2.5 273.5 258.5
+2.8
+1.5 One set of two rows 5.0 269.7 257.0 Reference Value Reference Value Two sets of two rows
- 38 ft. apart 5.0 272.3 258.4
+2.6
+1.4 The increase in the average and maximum cask temperature between the two models is due to the addition of the new pad as when a second set of two rows is placed next to the first set, the maximum and average outer cask temperature increases. Due to the simplifications made in the CFD models, the acceptability of the ISFSI expansion is based on subtracting the difference in the average / maximum cask temperature from the available temperature margin for the various cited TN40/TN40HT components.
L-PI-19-009 NSPM Page 34 of 40 When compared to the benchmark case (one set of two rows), the maximum cask surface temperature in the main body of the existing ISFSI thermal analysis is 276.0°F which compares well with 269.7°F, 270.7°F and 271.8°F when the thermal conductivity of the cask/ground is equal to 5.0, 2.5 and 0.5 W/m-K, respectively. The average cask temperature (260.0°F) from the existing ISFSI thermal analysis also compares well with the computed values (257.0 to 257.2°F) with various thermal conductivities.
From Table 3.5-1, the maximum temperature differences with respect to the cask maximum exterior temperature is 2.8°F and the average exterior temperature is approximately 1.5°F. As demonstrated by these results, the cask surface temperature increase over the results documented in the existing ISFSI thermal analyses is less than 5 °F. Therefore, as discussed in Section 3.1.3 of this enclosure, due to existing margins for the selected representative internal cask structures, the increase in internal temperature is not above allowable limits.
4.0 REGULATORY EVALUATION
4.1 Applicable Regulatory Requirements/Criteria The applicable regulatory requirements associated with this LAR include the following:
10 CFR 72.44, License Conditions 10 CFR 72.44 defines the requirements for license conditions included with license issued under Part 72. Specifically, 10 CFR 72.44(a) states:
Each license issued under this part shall include license conditions. The license conditions may be derived from the analyses and evaluations included in the Safety Analysis Report and amendments thereto submitted pursuant to § 72.24.
License conditions pertain to design, construction and operation. The Commission may also include additional license conditions as it finds appropriate.
This license amendment request proposes a change to a license condition under SNM-2506 pertaining to operation of the PI ISFSI. The technical evaluation in this enclosure concluded that the proposed change to the license condition is technically justified, acceptable and will not exceed regulatory limits. Thus with the changes proposed in this license amendment request, the requirements of 10 CFR 72.44 continue to be met.
10 CFR 72, Subpart F - General Design Criteria 10 CFR 72 Subpart F provides general design criteria for storage of high level nuclear wastes of which some apply to independent spent fuel storage facilities. The PI ISFSI provides for storage of dry spent fuel casks within a licensed storage facility. The proposed change requests increase in the maximum of spent fuel and approval of the design of an additional concrete pad utilizing alternate methods, but does not alter the cask design or the manner in which spent fuel is stored within the casks. Table 4.11 below lists the sections of Part 72
L-PI-19-009 NSPM Page 35 of 40 which contain general criteria and identifies if the section is affected by the changes proposed in this amendment request. For those sections which are affected, more detailed discussion is provided.
Table 4.1-1: ISFSI General Design Criteria Reviewed for the Proposed Amendment Regulation Title Affected by this Amendment 72.120 General consideration No 72.122 Overall requirements Yes 72.124 Criteria for nuclear criticality safety No 72.126 Criteria for radiological protection No 72.128 Criteria for spent fuel, high-level radioactive waste, and other radioactive waste storage and handling No 72.130 Criteria for decommissioning No 10 CFR 72.122, Overall Requirements 10 CFR 72.122 defines criteria applicable to dry spent fuel storage casks including quality standards, protection against environmental conditions and natural phenomena, fires and explosions, confinement barriers and systems, instrumentation and controls, and retrievability. Specifically, 10 CFR 72.122(e) states:
Proximity of sites. An ISFSI or MRS located near other nuclear facilities must be designed and operated to ensure that the cumulative effects of their combined operations will not constitute an unreasonable risk to the health and safety of the public.
The PI ISFSI will continue to meet the requirements of 10 CFR 72.122 with the increase in ISFSI storage capacity and will specifically in regards to 10 CFR 72.122(e) ensure that the cumulative effects of their combined operations will not constitute an unreasonable risk to the health and safety of the public.
Thus with the changes proposed in this license amendment request, the requirements of 10 CFR Part 72, Subsection F continue to be met.
10 CFR 72.102, Geological and Seismological Characteristics for Applications before October 16, 2003 and Applications for Other than Dry Cask Modes of Storage 10 CFR 72.102(c) and (d) defines requirements geological and seismological characteristics for applications made prior to October 16, 2003, which states in part:
(c) Sites other than bedrock sites must be evaluated for their liquefaction potential or other soil instability due to vibratory ground motion.
(d) Site-specific investigations and laboratory analyses must show that soil conditions are adequate for the proposed foundation loading.
L-PI-19-009 NSPM Page 36 of 40 The geological and seismological requirements of 10 CFR 72.102(c) and (d) continue to be met with the increase in the ISFSI storage capacity. The requirements of 10 CFR 72.102 apply as the PI ISFSI was sited prior to October 16, 2003. Thus, with the changes proposed in this license amendment request, the requirements of 10 CFR 72.102(c) and (d) continue to be met.
10 CFR 72.104, Criteria for Radioactive Materials in Effluents and Direct Radiation from an ISFSI or MRS 10 CFR 72.104(a) defines criteria for annual dose equivalents to individuals located beyond the controlled area, including ISFSIs, which states in part:
(a) During normal operations and anticipated occurrences, the annual dose equivalent to any real individual who is located beyond the controlled area must not exceed 0.25 mSv (25 mrem) to the whole body, 0.75 mSv (75 mrem) to the thyroid and 0.25 mSv (25 mrem) to any other critical organ The calculated dose values continue to meet the acceptance criteria of 10 CFR 72.104(a) with the increase in ISFSI storage capacity. Thus with the changes proposed in this license amendment request, the requirements of 10 CFR 72.104 continue to be met.
40 CFR 190.10, Standards for Normal Operations 40 CFR 190.10(a) defines criteria for operations that limits annual dose equivalents (a) The annual dose equivalent does not exceed 25 millirems to the whole body, 75 millirems to the thyroid, and 25 millirems to any other organ of any member of the public as the result of exposures to planned discharges of radioactive materials, radon and its daughters excepted, to the general environment from uranium fuel cycle operations and to radiation from these operations.
The calculated dose values continue to meet the acceptance criteria of 40 CFR 190.10(a) with the increase in ISFSI storage capacity. Thus with the changes proposed in this license amendment request, the requirements of 40 CFR 190.10 continue to be met.
10 CFR 20.1301, Dose Limits for Individual Members of the Public 10 CFR 20.1301(a) defines criteria for dose equivalents to individuals located beyond the controlled area, including ISFSIs:
(a) Each licensee shall conduct operations so that (1) The total effective dose equivalent to individual members of the public from the licensed operation does not exceed 0.1 rem (1 mSv) in a year, exclusive of the dose contributions from background radiation, from any administration the individual has received, from exposure to individuals administered radioactive
L-PI-19-009 NSPM Page 37 of 40 material and released under § 35.75, from voluntary participation in medical research programs, and from the licensee's disposal of radioactive material into sanitary sewerage in accordance with § 20.2003, and (2) The dose in any unrestricted area from external sources, exclusive of the dose contributions from patients administered radioactive material and released in accordance with § 35.75, does not exceed 0.002 rem (0.02 millisievert) in any one hour.
The calculated dose values continue to meet the acceptance criteria of 10 CFR 20.1301(a)(1) and (a)(2) with the increase in ISFSI storage capacity. Thus with the changes proposed in this license amendment request, the requirements of 10 CFR 20.1301 continue to be met.
10 CFR 72.106, Controlled Area of an ISFSI or MRS Part 72.106(b) defines criteria for dose equivalents to individuals located beyond the controlled area:
(b) Any individual located on or beyond the nearest boundary of the controlled area may not receive from any design basis accident the more limiting of a total effective dose equivalent of 0.05 Sv (5 rem), or the sum of the deep-dose equivalent and the committed dose equivalent to any individual organ or tissue (other than the lens of the eye) of 0.5 Sv (50 rem). The lens dose equivalent may not exceed 0.15 Sv (15 rem) and the shallow dose equivalent to skin or any extremity may not exceed 0.5 Sv (50 rem). The minimum distance from the spent fuel, high-level radioactive waste, or reactor-related GTCC waste handling and storage facilities to the nearest boundary of the controlled area must be at least 100 meters.
As described in Section 3.1.4.1 of this enclosure, the existing confinement analysis is not impacted by the proposed change. As the existing confinement analysis is not impacted and has not changed, the dose values therein continue to meet the acceptance criteria of 10 CFR 72.106(b). Therefore, the requirements of 10 CFR 72.106 continue to be met with the increase in ISFSI storage capacity.
4.2 Conclusions In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
L-PI-19-009 NSPM Page 38 of 40
5.0 ENVIRONMENTAL CONSIDERATION
NSPM reviewed the ISFSI Environmental Report and identified sections in which the information is directly affected by the proposed expansion of the ISFSI storage capacity.
Therefore, NSPM has prepared a supplement to the ISFSI Environmental Report in accordance with 10 CFR 51.45 which is provided as Enclosure 2 to this letter.
6.0 REFERENCES
- 1.
NRC Final Environmental Assessment, Final Environmental Assessment for the Proposed Renewal of U.S. Nuclear Regulatory Commission License No. SNM-2506 for Prairie Island Independent Spent Fuel Storage Installation, dated June 2015 (ADAMS Accession No. ML15098A026)
- 2.
American National Standard ANSI/ANS-57.9-1984, Design Criteria for an Independent Spent Fuel Storage Installation (Dry Storage Type), dated December 31, 1984
- 3.
NRC Regulatory Guide 1.198, Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites, Revision 0, dated November 2003 (ADAMS Accession No. ML033280143)
- 4.
NRC NUREG-0800, Section 3.7.1, Seismic Design Parameters, dated December 2014 (ADAMS Accession No. ML14198A460)
- 5.
NRC NUREG-0800, Section 3.7.2, Seismic System Analysis, dated September 2013 (ADAMS Accession No. ML13198A223)
- 6.
NRC NUREG/CR-6865, Parametric Evaluation of Seismic Behavior of Freestanding Spent Fuel Dry Cask Storage Systems, dated February 2005 (ADAMS Accession No. ML051120008)
- 7.
NRC Regulatory Guide 1.132, Site Investigations for Foundations of Nuclear Power Plants, Revision 2, dated October 2003 (ADAMS Accession No. ML032800710)
- 8.
NRC Regulatory Guide 1.61, Damping Values for Seismic Design of Nuclear Plants, Revision 1, Revision 1, dated March 2007 (ADAMS Accession No. ML070260029)
- 9.
NRC Regulatory Guide 1.92, Combining Modal Responses and Spatial Components in Seismic Response Analysis, Revision 3, dated October 2012 (ADAMS Accession No. ML12220A043)
- 10.
NRC NUREG-1536, Standard Review Plan for Spent Fuel Dry Storage Systems at a General License Facility, Revision 1, dated July 2010 (ADAMS Accession No. ML101040620)
L-PI-19-009 NSPM Page 39 of 40
- 11.
NRC NUREG-1567, Standard Review Plan for Spent Fuel Dry Storage Facilities, dated March 2000 (ADAMS Accession No. ML003686776)
- 12.
ACI Standard ACI 318-08, Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary, dated January 2008
- 13.
ACI Standard 201.2R-16, Guide to Durable Concrete, dated June 2008
- 14.
Letter (L-PI-18-021) from NSPM to the NRC, 2017 Annual Radioactive Effluent Report and Offsite Dose Calculation Manual, dated May 14, 2018 (ADAMS Accession No. ML18134A310)
- 15.
NRC NUREG-1927, Standard Review Plan for Renewal of Specific Licenses and Certificates of Compliance for Dry Storage of Spent Nuclear Fuel, Revision 1, dated June 2016 (ADAMS Accession No. ML16179A148)
- 16.
Letter from the NRC to NSPM, Prairie Island Nuclear Generating Plant, Units 1 and 2 -
Staff Assessment of Information Provided Pursuant to Title 10 of the Code of Federal Regulations Part 50, Section 50.54(f), Seismic Hazard Reevaluations for Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident and Staff Closure of Activities Associated with NTTF Recommendation 2.1, Seismic (TAC Nos. MF3784 and MF3785), dated December 15, 2015 (ADAMS Accession No. ML15341A162)
- 17.
NRC Safety Evaluation Report, Enclosure 2, Humboldt Bay Independent Spent Fuel Storage Installation, dated November 2005 (ADAMS Accession No. ML053140041)
- 18.
Calvert Cliffs ISFSI Updated Safety Analysis Report, Chapter 2, Site Characteristics, Revisions 24 and 25, dated November 15, 2016 (ADAMS Accession No. ML16333A264)
- 19.
Atomic Energy Commission WASH-1255, A Study of Vertical and Horizontal Earthquake Spectra, dated April 1973 (ADAMS Accession No. ML13203A235)
- 20.
NSPM Letter (L-PI-14-028) to the NRC, PINGP Seismic Hazard and Screening Report (CEUS Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f)
Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 27, 2014 (ADAMS Accession No. ML14086A628)
- 21.
NRC Safety Evaluation Report for Fermi 3 Combined Operating License Application, Chapter 3, Design of Structures, Components, Equipment and Systems, dated November 18, 2014 (ADAMS Accession Nos. ML14258B088)
L-PI-19-009 NSPM Page 40 of 40
- 22.
NRC Safety Evaluation Report for North Anna 3 Combined Operating License, Chapter 3, Design of Structures, Components, Equipment and Systems, dated January 18, 2017 (ADAMS Accession No. ML16305A135)
- 23.
NRC Safety Evaluation Report for SHINE Medical Technologies Facility, Related to the SHINE Medical Technologies, Inc. Construction Permit Application for a Medical Radioisotope Production Facility, dated October 2015 (ADAMS Accession No. ML15288A076)
- 24.
NRC Safety Evaluation Report for the HI STORM UMAX Canister Storage System, Docket No. 72-1040 HI-STORM UMAX Canister Storage System Holtec International, Inc. Certificate of Compliance No. 1040, dated April 2, 2015 (ADAMS Accession No. ML15093A510)
- 25.
NRC Safety Evaluation Report for the HI-STORM 100 Cask System, Safety Evaluation Report Docket No. 72-1014 HI-STORM 100 Cask System Holtec International, Inc.
Certificate of Compliance No. 1014 Amendment No. 7, dated December 28, 2009 (ADAMS Accession No. ML093620075)
- 26.
American Concrete Institute (ACI) Standard ACI 349-13, Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349-13) and Commentary, dated June 2014
- 27.
Letter from Nuclear Innovation North America LLC (NINA) to the NRC, Submittal of Final Safety Analysis Report Revision 13, Tier 2, Chapter 3C, Computer Programs Used in the Design and Analysis of Seismic Category I Structures, dated April 5, 2016 (ADAMS Accession No. ML16137A345)
- 28.
Letter from the NRC to NINA, Regulatory Audit Summary of South Texas Project, Units 3 and 4 Combined License Application - Seismic Design and Analyses, dated May 16, 2011 (ADAMS Accession No. ML111260469)
- 29.
Letter from the NRC to NINA, Regulatory Audit Summary of South Texas Project Units 3 and 4 Combined License Application - May 23 through May 27, 2011, dated January 2, 2013 (ADAMS Accession No. ML12346A389)