ML23100A002
| ML23100A002 | |
| Person / Time | |
|---|---|
| Site: | 07201004 |
| Issue date: | 04/05/2023 |
| From: | TN Americas LLC |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML23095A100 | List: |
| References | |
| E-62170 | |
| Download: ML23100A002 (1) | |
Text
Enclosure 5 to E-6 2170
Proposed Amendment 18, Revision 6 Changes to the Standardized NUHOMS System Updated Final Safety Analysis Report (Public Version)
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-3 P.3.8.7.2 Aluminum Components - Long Term Storage Deadweight Bearing Stress
The aluminum R90 rails are designed to resist the bearing loads due to the deadweight of the loaded basket for 80 years while stored in the HSM. A review of the R90 transition rail stresses shows that for the 1g deadweight loading, the R90 rail carries most of the loading. The aluminum R45 rails take some of the bearing load but are not controlling. For long-term creep effects, where loading on the aluminum transition rail redistributes over time, an average bearing stress is a more appropriate value to consider. The stresses calculated in Section P.3.8.6.6 are compared to allowable stress values that are reduced to limit the effect due to creep:
Component Bearing Stress Allowable Creep Stress Stress Ratio Aluminum Rail 0.046 ksi 0.758 ksi 0.0594 Aluminum Plate 0.0013 ksi 0.254 ksi 0.0051
Since the aluminum bearing stresses are significantly lower than allowable creep stresses, creep under long term storage conditions is not an issue.
P.3.8.7.3 Results for Analysis of 75g Accident Side Loading
75g accident side drop loads are analyzed using the ANSYS model described in Section P.3.8.6.1. Equivalent static elastic-plastic analyses are performed for computing the equivalent plastic strains.
Basket grid plate equivalent plastic strain results for accident 75g side drop loads are shown in Table P.3.8-6. Results based on the updated model for the bounding orientation of 210°, as well as the sensitivity analysis results based on the model including the nominal gap at the intersecting plate slots and without bolts and tie rods, are shown in Table P.3.8-7. An ANSYS strain contour plot corresponding to the bounding equivalent plastic strain values is shown in Figures P.3.8-6 and P.3.8-7 for with bolts and tie rods and without bolts and tie rods, respectively. A strain contour plot corresponding to the sensitivity analysis is shown in Figure P.3.8-8. The tabulated results show that all strains meet the corresponding allowable strain limits.
Side drop accelerations beyond 75g are considered and the last converged load step is considered the buckling load, which is compared with 75g, the required g-load for accident conditions. The buckling analysis results are shown in Table P.3.8-8 and results based on the updated model for the bounding orientation of 210°, as well as the results for the sensitivity analysis, are shown in Table P.3.8-9. The minimum factor of safety is 1.25.
The only significant stress in the basket aluminum rails is a bearing type stress where the transition rail is compressed between the basket grid plates and the inside surface of the DSC.
Since bearing stresses are not required to be evaluated for accident conditions, no further evaluation of the basket transition rails is required.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-7 P.3.8.7.4 75g Accident End Drop Loading Calculations
Compressive stress associated with the 75g end drop condition is calculated using conservative loads and geometry. For the 75g end drop load condition, the steel grid plates are assumed to carry their own weight plus the weight of all of the aluminum components. The fuel assembly loads are applied directly to the cover plates/shield plugs of the DSC shell assembly and not to the basket assembly. The basket weight considered below bounds the weight summarized in Section P.3.2. The axial stress calculated below represents the general membrane stress in the steel grid plates. The local bearing and peak stresses at the intersections of the slots are not required to be evaluated for accident conditions. There is no significant out-of-plane bending in the grid plates for the 75g end drop condition.
axial_75g = 75(Wbasket)/As
where Wbasket = 32.0 kips (conservative)
As = 135.2 in2
Therefore,
axial_75g = 17.75 ksi
This stress value is well below the yield stress, such that the 75g end drop load condition strains do not control and no further evaluation is required.
However, a buckling evaluation is performed in accordance with Reference [3.47]. The bottom basket grid plates are subjected to the greatest compressive stress during an end drop condition and, therefore, are considered in the buckling evaluation. Two different configurations, representing different dimensions and boundary conditions for a given grid plate, are analyzed for buckling. The first configuration consists of a grid plate representing a single span of a compartment. This configuration is considered as a plate simply supported on the loaded sides and is connected to the plates of adjacent compartments through middle portions of the unloaded edges, as shown in Section P.1.5 on Drawings NUH24PTH-L-5012-SAR, NUH24PTH-S-5012-SAR, and NUH24PTH-S-LC-5012-SAR. Since the plate is connected with adjacent plates through a portion of the unloaded edges, the plate is considered simply supported on that portion of the edge and free on the rest of the edge. The buckling load is determined by an eigenvalue buckling analysis performed by ANSYS using the model shown in Figure P.3.8-9. The resulting buckling stress is 102.7 ksi, and the allowable stress accounting for the safety factor of 2/3 is 68.45 ksi, which is substantially greater than the compressive stress of 17.75 ksi.
The second configuration consists of the top cantilever portion of the plate in the first configuration, which is considered as a plate with two free unloaded edges. The elastic buckling stress of such a plate based on the most conservative effective length factor of 2.1 is 47.59 ksi.
The allowable stress is, therefore, 31.73 ksi, which is substantially greater than the compressive stress of 17.75 ksi. As such, no part of the 24PTH Type 3 basket plates will buckle under accident end drop loading.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-8 P.3.8.7.5 Adjacent Fuel Compartment Relative Displacements
The maximum relative perpendicular displacement from one fuel compartment plate to another is determined from the ANSYS results for the accident side drops. These differences are addressed in the criticality evaluations to ensure that the fuel assembly array pitch does not significantly change due to the accident side drop. Maximum relative displacements for those adjacent compartments that have moved closer together are tabulated in Table P.3.8-10.
Maximum relative displacements based on the updated model for the bounding orientation of 210° are shown in Table P.3.8-11. The summary table includes results for analyses with bolts and tie rods modeled and for analyses without bolts and tie rods modeled. Maximum relative displacements corresponding to the sensitivity analysis including the nominal gap at slots is also shown in Table P.3.8-11.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-8a Table P.3.8-6 24PTH Type 3 Basket Grid Plate Strain - Side Drops with Bolts and Tie Rods Side Drop Load Strain(1) Maximum Strain Allowable Strain Case Fastener Status Category (in/in) (in/in) 75g, 0° Side Drop with Bolts and Tie m 0.00000 0.01 Rods m + b 0.00175 0.03 75g, 180°Side Drop with Bolts and Tie m 0.00000 0.01 Rods m + b 0.00433 0.03 75g, 210° Side Drop with Bolts and Tie m 0.00000 0.01 Rods m + b 0.00777 0.03 75g, 225° Side Drop with Bolts and Tie m 0.00000 0.01 Rods m + b 0.00487 0.03 75g, 270° Side Drop with Bolts and Tie m 0.00000 0.01 Rods m + b 0.00243 0.03 Notes:
(1) Equivalent plastic strain
Table P.3.8-7 24PTH Type 3 Basket Bounding Grid Plate Strain from the Updated Model - Side Drops with and without Bolts and Tie Rods Side Drop Load Fastener Status Strain(1) Maximum Strain Allowable Strain Case Category (in/in) (in/in) with Bolts and Tie m 0.00000 0.01 75g, 210° Side Rods m + b 0.00664 0.03 Drop without Bolts and m 0.00000 0.01 Tie Rods(2) m + b 0.00673 0.03 75g, 210° Side without Bolts and m 0.00000 0.01 Drop with Grid Tie Rods(2) + 0.01048 0.03 m b Plate Slot Gaps Notes:
(1) Equivalent plastic strain (2) Bolts and tie rods are removed from the model for this analysis, assuming that they fail.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-15 Table P.3.8-8 24PTH Type 3 Basket Buckling Analysis Results Summary
Load condition Last Converged Actual Maximum Factor of Load (g)(1) Load(g) Safety 75g 0° drop with bolts 94.0 75.0 1.25 and tie rods 75g 180° drop with 94.0 75.0 1.25 bolts and tie rods 75g 210° drop with 94.0 75.0 1.25 bolts and tie rods 75g 225° drop with 94.0 75.0 1.25 bolts and tie rods 75g 270° drop with 94.0 75.0 1.25 bolts and tie rods Notes:
(1) A maximum load of 94g is applied. Therefore, the buckling load and factor of safety may be greater.
Table P.3.8-9 24PTH Type 3 Basket Bounding Buckling Analysis Results from the Updated Model Load condition Last Converged Actual Maximum Factor of Load (g)(1) Load(g) Safety 75g 210° drop with 94.0 75.0 1.25 bolts and tie rods 75g 210° drop without 94.0 75.0 1.25 bolts and tie rods 75g, 210° Side Drop without bolts and tie 94.0 75.0 1.25 rods, with Grid Plate Slot Gaps Notes:
(1) A maximum load of 94g is applied. Therefore, the buckling load and factor of safety may be greater.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-16 Table P.3.8-10 24PTH Type 3 Basket Maximum Adjacent Fuel Compartment Relative Displacements
Drop Maximum Absolute Relative Displacement (in)
Load Condition Orientation With bolts and tie rods ux uz 0° 0.035810 0.096722 75g Accident Side 180° 0.043568 0.095689 Drop 210° 0.069562 0.11426 225° 0.093409 0.095402 270° 0.091852 0.034103
Table P.3.8-11 24PTH Type 3 Basket Bounding Maximum Adjacent Fuel Compartment Relative Displacements from the Updated Model Load Condition Drop Maximum Absolute Relative Displacement (in)
Orientation With bolts and tie rods Without bolts and tie rods(1) ux uz ux uz
75g Accident Side 210° 0.066351 0.11468 0.067193 0.11634 Drop 75g, 210° Side Drop with Grid Plate Slot 210° N/A(2) N/A(2) 0.077034 0.13108 Gaps Notes:
(1) Bolts and tie rods are removed from the model for this analysis, assuming that they fail.
(2) The sensitivity analysis only considers the bounding case without bolts and tie rods.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-17 April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.8-25 3.47. NUREG/CR-6322 Buckling Analysis of Spent Fuel Basket, U.S. Nuclear Regulatory Commission, May 1995.
April 2023 Revision 6 72-1004 Amendment No. 18 Page P.3.9-4 Enclosure 6 to E-62170
Listing of Computer Files Contained in Enclosure 7
Disk ID No. Discipline System/Component File Series (topics) Number (size) of files Appendix P.3.8 24PTH Type 3 Basket Structural Hard drive Analysis - Accident Conditions with grid plate slot gaps Structural Structural 24PTH Type 3 Basket Folder: \\ Structural 6 Folder Input and output files for ANSYS analysis of accident side drop - 2 10° orientationwith grid (5.43 G B) plate slot gaps and without bolts and tie rods
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