ML24263A284
| ML24263A284 | |
| Person / Time | |
|---|---|
| Site: | HI-STORM 100 |
| Issue date: | 09/19/2024 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML24263A279 | List: |
| References | |
| 5021079 | |
| Download: ML24263A284 (1) | |
Text
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 1-9
1.1 INTRODUCTION
HI-STORM UMAX is a dry, in-ground spent fuel storage system consisting of any number of Vertical Ventilated Modules (VVM) each containing one canister. The HI-STORM UMAX is designed to be fully compatible with all HI-TRAC transfer casks and multi-purpose canisters (MPC) presently certified under USNRC Docket No. 72-1014 and 72-1032. Safety analyses documented herein treat all MPCs listed in Table 1.2.1. However, as would be expected, the largest canisters, i.e., those licensed in the HI-STORM FW docket are governing in terms of structural and thermal margins. These largest canisters, namely MPC-37 and MPC-89 are termed Licensing Basis MPCs and the certification request for storage in HI-STORM UMAX is limited to these MPCs only. For completeness, the permissible contents from the HI-STORM FW docket are excerpted in Chapter 2 herein and also reproduced in the Technical Specification applicable to the CoC. The safety analyses summarized in this FSAR are intended to demonstrate that the HI-STORM UMAX System can safely store PWR or BWR fuel assemblies, in the MPC-37 or MPC-89, respectively. The MPC is identified by the maximum number of fuel assemblies it can contain in the fuel basket. As presently licensed in the HI-STORM FW docket, the standard MPC external diameters are identical to allow the use of a single overpack design; however the height of the MPC is varied to accord with the SNF to be loaded.
The HI-STORM UMAX Version B VVM is a variant of the HI-STORM UMAX design with its own licensing drawing listed in Section 1.5. Version B utilizes an enhanced HI-STORM UMAX closure lid design and includes optional seismic restraint features, for use if needed to meet structural requirements for design-basis site earthquakes. The optional seismic restraint features are referred to as MSE (Most Severe Earthquake) features. The HI-STORM UMAX Version B accepts the same MPCs and fuel types as the standard HI-STORM UMAX and the basic structural, shielding, and thermal-hydraulic characteristics remain unchanged. Hereafter in this FSAR, reference to HI-STORM UMAX is construed to also apply to the HI-STORM UMAX Version B variant. Where necessary, the text distinguishes among the different overpack designs.
The HI-STORM UMAX Version B1 and Version B2 are variants of the HI-STORM UMAX design with their own licensing drawing listed in Section 1.5. Version B1 and Version B2 are similar to Version B, with the vent sizes being the only difference between them and are only applicable to the MSE (Most Severe Earthquake) options. Version B1 and Version B2 utilize thermally qualified different heat loads which can be found in Chapter 2. Version B1 and Version B2 both include seismic restraint features referred to as MSE (Most Severe Earthquake) features. Version B1 and B2 accept MPC-37 and MPC-37 Type 1 for the MPC type, as well as 16x16 A for the fuel type. Hereafter in this FSAR, reference to HI-STORM UMAX is construed to also apply to the HI-STORM UMAX Version B1 and B2 variants.
The MPC is an integrally welded pressure vessel designed to meet the stress limits of the ASME Boiler and Pressure Vessel Code,Section III, Subsection NB [1.1.1]. The MPC defines the Confinement Boundary for the stored spent nuclear fuel assemblies. Regardless of the storage cell count, the construction of the MPC is fundamentally the same; the basket is a honeycomb structure comprised of cellular elements. This is positioned within a circumscribing cylindrical canister shell. The egg-crate construction and cell-to-canister shell interface employed in the MPC basket impart the structural stiffness necessary to satisfy the limiting load conditions to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 1-39 1.5 FIGURES AND DRAWINGS The licensing drawing for the HI-STORM UMAX System, pursuant to the requirements of 10CFR72.24(c)(3), is provided in this section. The material list on the licensing drawing contains sufficient information to articulate major design features and general operational characteristics of UMAX. Further, it is intended to serve as the control information to guide the preparation of the documents required to manufacture the components under Holtecs Quality Assurance Program. Holtecs Quality Assurance Program requires that the entire array of manufacturing documents must remain in complete conformance with the Licensing Drawing Package at all times.
The MPC and HI-TRAC drawings listed below are excerpted from the HI-STORM FW docket.
Drawing Package Number Description Revision 8446 HI-STORM UMAX Canister Storage System 22 10017 HI-STORM UMAX Version B Canister Storage System Proposed Rev 7A 6514 HI-TRAC VW - MPC-37 15 6799 HI-TRAC VW - MPC-89 11 6505 MPC-37 ENCLOSURE VESSEL 29 6506 MPC-37 FUEL BASKET 16 6512 MPC-89 ENCLOSURE VESSEL 31 6507 MPC-89 FUEL BASKET 16
[PROPRIETARY DRAWINGS WITHHELD IN ACCODRDANCE WITH 10 CFR 2.390]
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-21 2.1 SPENT FUEL TO BE STORED AND SERVICE LIMITS 2.1.1 Determination of the Design Basis Fuel A central object in the design of the HI-STORM UMAX System is to ensure that all SNF discharged from the U.S. reactors can be stored in the HI-STORM UMAX MPC upon meeting the burn up, cooling time and content conditions requirements set forth in this FSAR. Publications such as references [2.1.1] and [2.1.2] provide a comprehensive description of fuel discharged from U.S. reactors.
The cell openings in the fuel baskets have been sized to accommodate BWR and PWR assemblies. The cavity length of the MPC will be determined for a specific site to accord with the fuel assembly length used at that site, including non-fuel hardware and damaged fuel containers, as applicable.
Table 2.1.1 summarizes the authorized contents for the HI-STORM UMAX System.
Tables 2.1.2 and 2.1.3, which are referenced in Table 2.1.1, provide the fuel characteristics of all groups of fuel assembly types determined to be acceptable for storage in the HI-STORM UMAX System. Any fuel assembly that has fuel characteristics within the range of Tables 2.1.2 and 2.1.3 and meets the other limits specified in Table 2.1.1 is acceptable for storage in the HI-STORM UMAX System. The groups of fuel assembly types presented in Tables 2.1.2 and 2.1.3 are defined as array/classes as described in further detail in Chapter 6 of HI-STORM FW FSAR. Table 2.1.4 lists the BWR and PWR fuel assembly designs which are found to govern for three qualification criteria, namely reactivity, shielding, and thermal, or that are used as reference assembly design is those analyses. Additional information on the design basis fuel definition is presented in the following subsections.
2.1.2 Undamaged SNF Specifications Undamaged fuel is defined in the Glossary.
2.1.3 Damaged SNF and Fuel Debris Specifications Damaged fuel and fuel debris are defined in the Glossary.
Damaged fuel assemblies and fuel debris will be loaded into damaged fuel containers (DFCs) (Figure 2.1.6) that have mesh screens on the top and bottom. The DFC will have a removable lid to allow the fuel assembly to be inserted. In storage, a latch or other physical constraint will be used to ensure the lid remains in place. DFCs used to move fuel assemblies will be designed for lifting with either the lid installed or with a separate handling lid and retrievability guidance described in ISG-2 [2.7.1]. DFCs used to handle fuel and the associated lifting tools will be designed in accordance with the requirements of NUREG-0612. The DFC will be fabricated from structural aluminum or stainless steel.
The appropriate structural, thermal, shielding, criticality, and confinement evaluations have been performed to account for damaged fuel and fuel debris and are described in to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-23 requirements are performed in site-specific calculations. The evaluations here are therefore performed with reference fuel assemblies, and with parameters that result in reasonably conservative dose rates. The reference assemblies given in Table 1.0.4 of the HI-STORM FW FSAR are the predominant assemblies used in the industry.
The design basis dose rates can be met by a variety of burnup levels and cooling times.
Table 2.1.1 provides the acceptable ranges of burnup, enrichment and cooling time for all of the authorized fuel assembly array/classes. Table 2.1.5 and Figures 2.1.3 and 2.1.4 provide the axial distribution for the radiological source terms for PWR and BWR fuel assemblies based on the axial burnup distribution. The axial burnup distributions are representative of fuel assemblies with the design basis burnup levels considered. These distributions are used for analyses only, and do not provide a criteria for fuel assembly acceptability for storage in the HI-STORM UMAX System.
Non-fuel hardware, as defined in the Glossary, has been evaluated and is also authorized for storage in the PWR MPCs as specified in Table 2.1.1.
2.1.7 Criticality Parameters for Design Basis SNF The criticality analyses for the MPC-37 are performed with credit taken for soluble boron in the MPC water during wet loading and unloading operations. Table 2.1.6 provides the required soluble boron concentrations for this MPC.
2.1.8 Summary of Authorized Contents Tables 2.1.1 through 2.1.3 specify the limits for spent fuel and non-fuel hardware authorized for storage in the HI-STORM FW System. The limits in these tables are derived from the safety analyses described in the following chapters of this FSAR.
2.1.9 Permissible Heat Load for MPC-37 and MPC-89 MPC-89 (BWR) and MPC-37 (PWR) canisters are previously licensed in Docket 72-1032 for storage of spent fuel and are permitted for storage in HI-STORM UMAX with permissible heat loads as specified in Table 2.1.7. As shown in Figures 2.1.7 and 2.1.8 for MPC-37 and MPC-89 respectively, each storage location is associated with a unique cell identification number. The permissible heat loads for each cell in the canister for storage in the HI-STORM UMAX VVM are given in Figure 2.1.19 and Figures 2.1.12 through 2.1.18 for MPC-89 and MPC-37 respectively.
The permissible aggregate heat load for storage in MPC-37 and MPC-89 are provided in Tables 2.1.8 and 2.1.9 respectively. Table 2.1.13 and Table 2.1.15 provide the maximum permissible heat loads under long term storage for MPC-37 with HI-STORM UMAX Version B1 and HI-STORM UMAX Version B2 respectively. Figures 2.1.27 and 2.1.29 provide the permissible heat loads for each cell in the canister for the HI-STORM UMAX Version B1 and HI-STORM UMAX Version B2, respectively.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-24 MPC-37 Type 1 permissible aggregate heat load is provided in Table 2.1.12 and the permissible per cell heat load is shown in Figure 2.1.26. MPC-37 Type 1 permissible aggregate heat load is provided in Table 2.1.14 for HI-STORM UMAX Version B1 and Table 2.1.16 for HI-STORM UMAX Version B2. Figure 2.1.28 and Figure 2.1.30 provides the permissible heat loads for each cell in the canister of the MPC-37 Type 1 for HI-STORM UMAX Version B1 and HI-STORM UMAX Version B2 respectively.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-44 TABLE 2.1.8 HI-STORM UMAX MPC-37 PERMISSIBLE HEAT LOADSNote 5 Fuel Type (see Table 2.1.7 for length data)
Description Helium Backfill Pressure Option (Notes 2)
Heat Load per Storage Cell (Note 3)
Permissible Aggregate Heat Load (Note 1), kW Short Fuel Heat Load Chart 1 1
Figure 2.1.12 33.88 Heat Load Chart 2 2
Figure 2.1.14 33.70 Heat Load Chart 3 1
Figure 2.1.16 33.53 Standard Fuel Heat Load Chart 1 1
Figure 2.1.12 33.88 Heat Load Chart 2 2
Figure 2.1.14 33.70 Heat Load Chart 3 1
Figure 2.1.17 35.30 Long Fuel Heat Load Chart 1 1
Figure 2.1.13 35.76 Heat Load Chart 2 2
Figure 2.1.15 35.57 Heat Load Chart 3 1
Figure 2.1.18 37.06 Short Fuel Sub-Design Heat Load 3
Figure 2.1.19 34.28 Threshold Heat Load 3
Figure 2.1.21 33.46 Standard Fuel Sub-Design Heat Load 3
Figure 2.1.19 34.28 Threshold Heat Load 3
Figure 2.1.21 33.46 Long Fuel Sub-Design Heat Load 3
Figure 2.1.20 36.19 Threshold Heat Load 3
Figure 2.1.21 33.46 16x16A Fuel (see Table 2.1.2)
Intact Fuel in up to 37 DFCs (Note
- 4) 3 Figure 2.1-25 32.3 Note 1: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
However, the CoC restricts the permissible aggregate heat load to the value specified in this table.
Note 2: The helium backfill range is in Table 4.4.6.
Note 3: Decay heat limits must be met for all contents in a fuel storage location (i.e., fuel and non-fuel hardware, as applicable).
Note 4: This may include undamaged fuel both in DFCs and not, and damaged fuel in DFCs.
These heat load limits apply with one or more undamaged fuel assemblies stored in DFCs.
Note 5: MPC-37 Type 1 Heat Load Limits given in Table 2.1.12. to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-45 Note 6: For MPC-37, and MPC-37 Type 1 stored in HI-STORM UMAX Version B1 and B2 systems, Tables 2.1.13, 2.1.14, 2.1.15 and 2.1.16 contain additional Heat Load restrictions.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-48 TABLE 2.1.12 HI-STORM UMAX MPC-37 TYPE 1 PERMISSIBLE HEAT LOADS Fuel Type (see Table 2.1.7 for length data)
Description Helium Backfill Pressure Option (Notes 2)
Heat Load per Storage Cell (Note 3)
Permissible Aggregate Heat Load (Note 1), kW Standard Fuel Option 1 Figure 2.1.26 32.3 Note 1: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
Note 2: The helium backfill range is in Table 4.4.6.
Note 3: Decay heat limits must be met for all contents in a fuel storage location (i.e., fuel and non-fuel hardware, as applicable).
Note 4: See Tables 2.1.13, 2.1.14, 2.1.15, and 2.1.16 for further restrictions regarding HI-STORM UMAX B1 and B2 Systems.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-49 Table 2.1.13 HI-STORM UMAX Version B1 MPC-37 PERMISSIBLE HEAT LOADS MPC Type Fuel Type (See Table 2.1.7 for length data)
Fuel Assembly Array and Class Heat Load per Storage Cell (Note 1)
Permissible Aggregate Heat Load (Note 2),
kW MPC-37 Standard Fuel 16x16 A Figure 2.1.27 38.51 Note 1: See Figure 2.1.27 for more details about cell heat load.
Note 2: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-50 Table 2.1.14 HI-STORM UMAX Version B1 MPC-37 Type 1 PERMISSIBLE HEAT LOADS MPC Type Fuel Type (See Table 2.1.7 for length data)
Fuel Assembly Array and Class Heat Load limit per Storage Cell (Note 1)
Permissible Aggregate Heat Load (Note 2),
kW MPC-37 Type 1
Standard Fuel 16x16 A Figure 2.1.28 31.44 Note 1: See Figure 2.1.28 for more details about cell heat load.
Note 2: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-51 Table 2.1.15 HI-STORM UMAX Version B2 PERMISSIBLE HEAT LOADS MPC Type Fuel Type (See Table 2.1.7 for length data)
Fuel Assembly Array and Class Heat Load limit per Storage Cell (Note 1)
Permissible Aggregate Heat Load (Note 2),
kW MPC-37 Standard Fuel 16x16 A Figure 2.1.29 11.65 Note 1: See Figure 2.1.29 for more details about cell heat load.
Note 2: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-52 Table 2.1.16 HI-STORM UMAX Version B2 PERMISSIBLE HEAT LOADS MPC Type Fuel Type (See Table 2.1.7 for length data)
Fuel Assembly Array and Class Heat Load limit per Storage Cell (Note 1)
Permissible Aggregate Heat Load (Note 2),
kW MPC-37 Type 1
Standard Fuel 16x16 A Figure 2.1.30 9.50 Note 1: See Figure 2.1.30 for more details about cell heat load.
Note 2: The aggregate heat load is defined as a sum of all stored fuel assemblies. Thermal evaluations in Chapter 4 are performed with maximum per storage cell heat load in all locations.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-79 1
1.090 2
0.795 3
1.090 4
1.040 5
1.210 6
1.310 7
1.210 8
1.040 9
1.090 10 1.210 11 0.870 12 0.870 13 0.870 14 1.210 15 1.090 16 0.795 17 1.310 18 0.870 19 0.575 20 0.870 21 1.310 22 0.795 23 1.090 24 1.210 25 0.870 26 0.870 27 0.870 28 1.210 29 1.090 30 1.040 31 1.210 32 1.310 33 1.210 34 1.040 35 1.090 36 0.795 37 1.090 Figure 2.1.27: HI-STORM UMAX B1 MPC-37 Permissible Heat Load for Standard Fuel 16x16A Legend Cell ID Heat Load, kW to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-80 1
0.705 2
0.825 3
0.705 4
0.640 5
1.030 6
1.195 7
1.030 8
0.640 9
0.705 10 1.030 11 0.830 12 0.830 13 0.830 14 1.030 15 0.705 16 0.825 17 1.195 18 0.830 19 0.280 20 0.830 21 1.195 22 0.825 23 0.705 24 1.030 25 0.830 26 0.830 27 0.830 28 1.030 29 0.705 30 0.640 31 1.030 32 1.195 33 1.030 34 0.640 35 0.705 36 0.825 37 0.705 Figure 2.1.28: HI-STORM UMAX B1 MPC-37 Type 1 Permissible Heat Load for Standard Fuel 16x16A Legend Cell ID Heat Load, kW to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-81 1
0.330 2
0.240 3
0.330 4
0.315 5
0.365 6
0.395 7
0.365 8
0.315 9
0.330 10 0.365 11 0.265 12 0.265 13 0.265 14 0.365 15 0.330 16 0.240 17 0.395 18 0.265 19 0.175 20 0.265 21 0.395 22 0.240 23 0.330 24 0.365 25 0.265 26 0.265 27 0.265 28 0.365 29 0.330 30 0.315 31 0.365 32 0.395 33 0.365 34 0.315 35 0.330 36 0.240 37 0.330 Figure 2.1.29: HI-STORM UMAX B2 MPC-37 Permissible Heat Load for Standard Fuel 16x16A Legend Cell ID Heat Load, kW to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-82 1
0.215 2
0.250 3
0.215 4
0.195 5
0.310 6
0.360 7
0.310 8
0.195 9
0.215 10 0.310 11 0.250 12 0.250 13 0.250 14 0.310 15 0.215 16 0.250 17 0.360 18 0.250 19 0.085 20 0.250 21 0.360 22 0.250 23 0.215 24 0.310 25 0.250 26 0.250 27 0.250 28 0.310 29 0.215 30 0.195 31 0.310 32 0.360 33 0.310 34 0.195 35 0.215 36 0.250 37 0.215 Figure 2.1.30: HI-STORM UMAX B2 MPC-37 Type 1 Permissible Heat Load for Standard Fuel 16x16A Legend Cell ID Heat Load, kW to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 2-117 Table 2.4.1 LOAD CASES AND ACCEPTANCE CRITERIA Load Case I.D.
Bounding Loading Affected Sub-Component Applicable Data Acceptance Criterion Magnitude of Loading Reference Coincident Metal Temperature (Deg. F) 06 VVM loaded by the overhead transfer cask and Mating Device during the transfer operation Container Shell 150 Service A stress limit for NF Class 3 plate and shell structure and buckling stress limits for the VVM shell must be met.
07 Design Basis Flood Container Shell 125 feet of water head 150 The hoop stress in the Container Shell shall be below the minimum material yield strength without taking credit for the action of the surrounding subgrade.
Note 1. Structural loads and acceptance criteria for each load case are further explained in Section 2.4.
Note 2: Materials of construction are identified in Table 2.6.2.
Note 3: Design attributes of the VVM are explained in Chapter 1 and details are presented in the drawings in Section 1.5.
Note 4: The limiting value of coincident metal temperature is used to establish material properties and allowable stress (or stress intensity) when applicable. The reference coincident metal temperatures apply to all HI-STORM UMAX VVMs, except for the Container Shell of HI-STORM UMAX Versions B1 and B2. For the B1 and B2 Versions, the reference metal temperature for the Container Shell is 400°F for Load Cases 01 and 03 only.
Note 5: Load cases applicable to MPC and HI-TRAC VW are presented in Tables 2.2.6, 2.2.7, 2.2.13 and 3.1.1 of the HI-STORM FW FSAR.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 4-9 Table 4.1.3 PEAK CLADDING TEMPERATURE RESULTS FOR DIFFERENT HI-STORM UMAX DESIGN VERSIONS**
UMAX Versions Temperature oC (oF)
Standard 367 (693)*
Version B 367 (693)
Version B1 348 (659)
Version B2 289 (552)
Version B1 (with MPC-37 Type 1) 331 (628)***
- The PCT results tabulated herein are for normal storage condition of HI-STORM UMAX design versions under quiescent (no wind) conditions.
UMAX Standard and Version B designs are loaded with short MPC-37 under Heat Load Chart 1. UMAX Version B1 and Version B2 are loaded with MPC-37 and MPC-37 Type 1 containing 16x16A fuel under heat loads defined in Table 2.1.13, Table 2.1.13, Table 2.1.14 and Table 2.1.16.
- Standard version is adopted to perform all the licensing basis calculations for HI-STORM UMAX System in this safety report.
- The PCT result for Version B2 loaded with MPC-37 is bounded by Version B1, therefore, only Version B1 loaded with MPC-37 Type 1 is reported herein.
to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 4-24 4.4.4.2 Evaluation of HI-STORM UMAX Version B Design
[
PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10 CFR 2.390
]
4.4.4.3 Evaluation of HI-STORM UMAX Version B Design variants*
[
PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10 CFR 2.390
] to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 4-59 4.6 OFF-NORMAL AND ACCIDENT EVENTS The safety evaluation of off-normal and accident conditions described in Section 2.5 is presented in this section. Thermal analysis of the HI-STORM UMAX System is performed for the governing thermal configuration, i.e. MPC-37 with short fuel under heat load Chart 1, identified by the analysis in Section 4.1.
4.6.1 Off-Normal Events 4.6.1.1 Off-Normal Environmental Temperature To evaluate the effect of off-normal weather conditions, an off-normal ambient temperature (Table 2.3.6) is postulated to persist for a sufficient duration to allow the HI-STORM UMAX system to reach steady state conditions. Because of the large mass of the HI-STORM UMAX system, with its corresponding large thermal inertia and the limited duration for the off-normal temperatures that arise in real life, this assumption is conservative. Starting from a baseline condition evaluated in Section 4.4 (normal ambient temperature and limiting fuel storage configuration) the temperatures of the HI-STORM UMAX system are conservatively assumed to be elevated by the difference between the off-normal and normal ambient temperatures. The HI-STORM UMAX extreme ambient temperatures computed in this manner are reported in Table 4.6.1. The co-incident MPC pressure is also computed (Table 4.6.5) and compared with the off-normal design pressure (Table 2.3.5), which shows a positive safety margin. The results are confirmed to be below the corresponding limits in Chapter 2.
4.6.1.2 Partial Blockage of Air Inlets The HI-STORM UMAX system is designed with debris screens installed on the inlet and outlet openings. These screens ensure the air passages are protected from entry and blockage by foreign objects. However, as required by the design criteria presented in Chapter 2, it is postulated that the HI-STORM UMAX air inlet vents are 50% blocked*. The resulting decrease in flow area increases the flow resistance of the inlet ducts. The effect of the increased flow resistance on fuel temperature is analyzed assuming that steady state conditions have been reached for the governing thermal configuration established by a series of thermal analyses in Section 4.4 in the foregoing. The computed temperatures and pressures are reported in Tables 4.6.1 and 4.6.5 respectively. The results are confirmed to be below the allowable limits for both internal pressure and temperature limits presented in Tables 2.3.5 and 2.3.7 respectively.
4.6.1.3 Off-Normal Pressure This event is defined as a combination of (a) maximum helium backfill pressure permitted, (b) 10% fuel rods rupture, (c) governing thermal configuration, and (d) normal ambient temperature
- The off-normal condition with partial blockage of air inlet vents is not applicable to HI-STORM UMAX Version B2 design as it has 100% blocked inlet vents. to Holtec Letter 5021079
HOLTEC INTERNATIONAL COPYRIGHTED MATERIAL HI-2115090 Proposed Rev. 87 4-77
[4.4.11] [PROPRIETARY INFORMATION WITHHELD IN ACCORDANCE WITH 10 CFR 2.390]
to Holtec Letter 5021079