ML22091A041
| ML22091A041 | |
| Person / Time | |
|---|---|
| Issue date: | 04/07/2022 |
| From: | NRC/NRR/DNRL/NRLB |
| To: | |
| Schiller A | |
| Shared Package | |
| ML22091A040 | List: |
| References | |
| NEDO-33914, Rev. 1 | |
| Download: ML22091A041 (14) | |
Text
Staff Presentation to the ACRS Full-Committee GEH Licensing Topical Report BWRX-300 Advanced Civil Construction and Design Approach (NEDO-33914, Revision 1)
April 7, 2022
2 NRC Staff Reviewers:
Amitava Ghosh, Ph.D., Geotechnical Engineer, Presenter, NRR/DEX/ESEB David Heeszel, Ph.D., Geophysicist, NRR/DEX/EXHB Edward Stutzcage, Health Physicist, NRR/DRA/ARCB Angelo Stubbs, Sr. Safety and Plant Systems Engineer, NRR/DSS/SCPB Sujit Samaddar, Sr. Structural Engineer, NMSS/DFM/MSB Project Managers:
Alina Schiller, TR Project Manager, NRR/DNRL/NRLB James Shea, Sr. Project Manager, NRR/DNRL/NRLB GEH BWRX-300: ACRS Full Committee April 7, 2022
3 Agenda
- Introduction
- Difference Between Traditional Light Water Reactor and GEH BWRX-300
- Regulatory Bases
- Staff Limitations and Conditions (L&Cs)
GEH BWRX-300 Reactor
- Reactor Building (RB) is placed in a vertical right-cylinder shaft and located mostly below-grade to mitigate effects of possible external events, including aircraft crashes, adverse weather, flooding, fires, and earthquakes GEH BWRX-300: ACRS Full Committee 4
LTR Figure 1-3 April 7, 2022
Regulatory Bases
- Defining Subsurface Conditions o 10 CFR 100.20(c)(1): physical characteristics of the site o 10 CFR 100.23: geologic and seismic considerations
- Development of Site Design Parameters o 10 CFR Part 50, Appendix A, General Design Criteria 2: Design bases for protection against natural phenomena GEH BWRX-300: ACRS Full Committee 5
April 7, 2022
Rock Fracture Network
- Fractures control the response of a rock mass
- Fracture network:
- Dip angle
- Dip direction
- Fracture spacing
- Number of fracture sets
- Staff will review rock fracture network characterization in a site-specific license application GEH BWRX-300: ACRS Full Committee 6
From: Cao, et al. 2016. An Experimental and Numerical Study on Mechanical Behavior of Ubiquitous-Joint Brittle Rock-Like Specimens Under Uniaxial Compression. Rock mechanics and Rock Engineering.
April 7, 2022
NRC Staff Review
- LTR proposes approaches at conceptual level to deal with the technical issues
- Staff conducted a comprehensive review of each proposed approach(es)
- Foundation Interface Analysis (FIA) (LTR Section 4)
- Stability of reactor shaft (LTR Section 5.1.2 and others)
- Soil-Structure Interaction (SSI) modeling (including parameter estimation of equivalent linear elastic materials)
(LTR Section 5.1.2)
- Strain-compatible dynamic properties (LTR Section 5.2.4)
- Nonlinear SSI analysis (sensitivity) (LTR Section 5.3.11)
April 7, 2022 GEH BWRX-300: ACRS Full Committee 7
L&C #1: Interface Testing Large size samples collected at a site tested in the laboratory to have an acceptable estimate of the measured discontinuity, strength and deformation parameters Staff will review the sizes of the samples and their testing at the laboratory to estimate the properties of the discontinuities and interfaces in a site-specific license application with a BWRX-300 SMR GEH BWRX-300: ACRS Full Committee 8
From: Fan, et al. 2019. Geotechnical and Geological Engineering. Experimental and Numerical Study on the Damage Evolution of Random Rock Joint Surface During Direct Shear Under CNL Condition.
April 7, 2022
Stability of Reactor Shaft
- Stability of Embedded Reactor: Unstable rock mass without any permanent support systems is not acceptable
- Unstable blocks in surrounding region o Key block theory (Goodman and Shi, 1985) o Numerical simulation e.g.,
FIA model (LTR Section 4.0) o Results verified by instrumentation installed (LTR Section 3.3)
GEH BWRX-300: ACRS Full Committee 9
From: Cao, et al. 2016. An Experimental and Numerical Study on Mechanical Behavior of Ubiquitous-Joint Brittle Rock-Like Specimens Under Uniaxial Compression. Rock Mechanics and Rock Engineering.
April 7, 2022
L&C #2: Stable Excavation A stable shaft excavation would have no unstable blocks in its surrounding that may slide into the excavation A self-supported (even with some temporary reinforcement) excavation would be needed to place the RB and to estimate the earth pressure loads to be considered in the generic design of the RB structure Staff will review method(s) used to identify the unstable rock blocks and to assess the earth pressure imparted on the RB shaft for determining whether the subgrade is acceptable for siting the reactor in a site-specific application Any mitigation measures used to stabilize the surrounding materials would be reviewed by the staff GEH BWRX-300: ACRS Full Committee 10 April 7, 2022
L&C #3: Isotropic and Homogeneous Rock Mass Rock mass classification systems inherently assume isotropic and homogeneous rock mass to determine rock mass modulus for use in Soil-Structure Interaction (SSI) analyses A jointed (or a fractured) rock mass is assumed to contain a sufficient number of fracture sets so that its deformational behavior may be assumed to be isotropic and homogeneous Staff will review whether the fracture sets at the selected site would make the rock mass behavior isotropic and homogeneous in any future site-specific licensing application GEH BWRX-300: ACRS Full Committee 11 April 7, 2022
L&C # 4: Site Specific Application of the HCSCP
- GEH has proposed to develop Hazard Consistent Strain-Compatible Properties (HCSCP) so that properties used as input for SSI analysis to be consistent with soil/rock properties used in generation of input motion
- During review of future licensing applications, staff will audit the HCSCP approach GEH BWRX-300: ACRS Full Committee 12 April 7, 2022
L&C # 5: Sensitivity Nonlinear SSI Analysis May be important for sites with high seismicity and/or with highly nonlinear subgrade materials Separation and/or sliding at soil/rock-structure interface Nonlinearity at rock fractures NRC staff plans to review the characterization and modeling of the nonlinear behavior of the materials surrounding the reactor in any future licensing application utilizing a nonlinear SSI analysis approach GEH BWRX-300: ACRS Full Committee 13 April 7, 2022
Staff Conclusions
- The approaches to characterize the surrounding media (soil and/or rock) are reasonable
- The design approaches for a deeply imbedded RB structure are reasonable
- The construction methods for the BWRX-300, as described in this LTR, are acceptable with the associated L&Cs.