ML23254A384
| ML23254A384 | |
| Person / Time | |
|---|---|
| Site: | Triso-X |
| Issue date: | 09/29/2023 |
| From: | Matt Bartlett NRC/NMSS/DFM/FFLB |
| To: | Triso-X |
| Shared Package | |
| ML23254A381 | List: |
| References | |
| Download: ML23254A384 (4) | |
Text
AGhosh - Chapter 1 (Geotechnical) - RAIs Geotechnical Request for Additional Information for the TRISO-X License Application Review RAI-1 Locations of the geotechnical borings with respect to the Process Building and Correction of geologic cross-sections:
Regulatory Basis:
This information is necessary to satisfy the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 70.22(a)(7), which states in part that applicants must provide A description of equipment and facilities which will be used by the applicant to protect health and minimize danger to life or property. In addition, 10 CFR 70.65(b)(1) and (2) state that the integrated safety analysis summary must contain (1) A general description of the site with emphasis on those factors that could affect safety (i.e.,
meteorology, seismology); and (2) A general description of the facility with emphasis on those areas that could affect safety, including an identification of the controlled area boundaries.
Describe Issue:
The locations of certain borings are unclear as to whether they are within or outside the footprint of the Process Building. For example, License Application (LA) Figure 1-5 (Cross Section 2) shows that Boring B-23 is outside the Process Building footprint whereas Figure 1-7 shows that B-23 is inside the footprint. In addition, the log of Boring B-3 given in Cross Section 1 (LA Figure 1-4) do not match with the log given in Cross Section 5 (LA Figure 1-8). All Rock Quality Designation (RQD) values are 54 in Cross Section 5. Additionally, the RQD values reported at deeper depths (e.g., below 720 ft elevation) of Boring B-23, shown in Cross Section 2 (LA Figure 1-5) and Cross Section 4 (LA Figure 1-7), do not match. Similarly, RQD values at deeper depths of Boring B-27 do not match in Cross Section 2 (LA Figure 1-5) and Cross Section 5 (LA Figure 1-8).
Information Needed:
Provide an updated LA Figure 1-3 of the geotechnical boring locations superimposed on the footprint of the Process Building. Additionally, update the cross-sections provided in LA Figures 1-4 through 1-8.
RAI-2 Backfill and site work:
Regulatory Basis:
This request for additional information (RAI) has the same regulatory basis as RAI 1.
Describe Issue:
Based on the five cross-sections of the site (Figures 1-4 through 1-8 of LA), a major portion of the footprint area of the Process Building is below the proposed top of the building foundation 811 ft above mean sea level (MSL). Consequently, major site work including use of significant amount of backfill or engineered material(s) would be necessary to bring the top of subsurface at the 811 ft above MSL grade level to Enclosure 1
AGhosh - Chapter 1 (Geotechnical) - RAIs construct the foundation for the Process Building. Currently, high plasticity clay and low plasticity clay are present in the subsurface at depths from 3.6 to 18 ft below the existing ground surface within the Process Building footprint. Presence of fat clay with swelling potential in presence of moisture may affect the stability of the overlying foundation.
Information Needed:
Describe the characteristics that would be suitable for use as the backfill to raise the level of the surface to the desired elevation of the Process Building foundation. Confirm whether fat clays would be part of the backfill or part of the subsurface of the Process Building. Describe the plan to improve the subsurface soil characteristics, if any, to increase the load bearing capacity of the subgrade and minimize the potential settlement.
RAI-3 Foundation of the Process Building:
Regulatory Basis:
This RAI has the same regulatory basis as RAI 1.
Describe Issue:
The proposed foundation system of the Process Building will be a large mat foundation with a Rigid Inclusion (RI) and associated Load Transfer Platform (LTP). This composite matrix foundation system with overall improved engineering properties is relied upon to:
(1) support the loads of the Process Building (i.e., adequate bearing capacity under both static and seismic loads), (2) reduce settlement given the characteristics of the in situ soil and backfill, and presence of the karst environment (e.g., voids present in the subsurface, as evidenced in LA Figures 1-4 through 1-8), and (3) minimize differential settlement within the design specifications of the Process Building. In addition, the Standard Penetration Test blow counts N measured in the subsurface clay layers, present at depths between 3.6 and 18 ft below the existing ground surfaces within the footprint of the Process Building, are low, as shown in the boring logs (LA Figures 1-4 through 1-8). Minimum N of 2 was measured in Boring B-1. Maximum N recorded was 35 in Boring B-25. Majority of the N values are below 20. LA Section 1.1.1.4 provides the concept of the foundation system, i.e., a composite matrix foundation with the RI and the LTP; however, a description of the foundation system design (e.g., size and thickness of the mat foundation, size and thickness of the LTP including the material(s) characteristics, and size, number, and pattern of the cement grout columns of the RI) along with its capability to withstand the anticipated loads with minimum foundation settlement is currently lacking.
Information Needed:
Describe the foundation system (mat foundation, LTP, and RI) of the Process Building (e.g., dimensions, materials of construction, strength, stiffness, etc.). Description of the LTP should include, at a minimum, the size, thickness, characteristics of the material(s) used. Description of the RI should include, at a minimum, the number, size, and depth of the cement grout columns, material(s) used with specific characteristics, and characteristics of the grid pattern (e.g., spacings between the grout columns, square or rectangular pattern with regular or staggered column placement, etc.), and the estimated 2
AGhosh - Chapter 1 (Geotechnical) - RAIs strength of the resulting subsurface. Also, summarize the results of the design analysis showing that the proposed foundation system design will have sufficient bearing capacity against both static and dynamic loads and the expected settlements would be within the acceptable range of the design of the Process Building.
RAI-4 Liquefaction:
Regulatory Basis:
This information is necessary to satisfy the requirements of 10 CFR 70.22(a)(7), which state in part to provide, A description of equipment and facilities which will be used by the applicant to protect health and minimize danger to life or property. In addition, 70.64(a)(2) requires consideration of the (2) Natural phenomena hazards. The design must provide for adequate protection against natural phenomena with consideration of the most severe documented historical events for the site. According to 10 CFR 70.65(b)(1) and (2) the integrated safety analysis summary must contain (1) A general description of the site with emphasis on those factors that could affect safety (i.e.,
meteorology, seismology); and (2) A general description of the facility with emphasis on those areas that could affect safety, including an identification of the controlled area boundaries.
Describe Issue:
Discussion of the liquefaction potential of the subsurface soil layers including the fill material(s) is not provided.
Information Needed:
Summarize the results of an analysis showing that the soil layers including the backfill(s) below the foundation will not liquefy under the design-basis seismic load.
RAI-5 Differential settlement across the Process Building:
Regulatory Basis:
This RAI has the same regulatory basis as RAI 1.
Describe Issue:
Based on the five cross-sectional plots of the proposed site (Figures 1-4 through 1-8 of the LA), location of the rock-soil interface below the Process Building footprint varies significantly. In addition, the thickness of the soil above this interface significantly varies spatially. As stated in LA Section 1.1.1.4 Geology, the overburden soil thickness below the final grade is expected to vary generally from less than 5 feet to approximately 25 feet within the footprint of the process building. Use of backfill to bring the Process Building foundation to 811 ft elevation introduces another material in the subsurface with potentially different material characteristics. Consequently, the potential for settlement varies spatially resulting in differential settlement. Design of the Process Building should be able to tolerate the anticipated differential settlement.
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AGhosh - Chapter 1 (Geotechnical) - RAIs Information Needed:
Summarize the results of an assessment showing that the foundation design achieves the goal of acceptable differential settlement throughout the Process Building.
RAI-6 Geotechnical parameters Regulatory Basis:
This RAI has the same regulatory basis as RAI 1.
Description of Issue:
There is no discussion in the LA regarding the geotechnical tests conducted on both soil and rock samples collected at the proposed site. In addition, the LA does not discuss how the results of these geotechnical tests are used to develop the design of the foundation of the Process Building.
Information Needed:
Describe the tests conducted on both soil and rock samples collected at the site and summarize the results of the parameters that would be used in the geotechnical design of the proposed facility.
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