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Enclosure 2: Absorption Coefficient for Pool Water and Reactor Building Floor Interaction, PM-1218-63882, Revision 0
	ML18362A142
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Site:	NuScale
Issue date:	12/19/2018
From:	; NuScale
To:	; Office of New Reactors
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	L0-1218-63884 PM-1218-63882-NP, Rev 0
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Enclosure 2:

"Absorption Coefficient for Pool Water and Reactor Building Floor Interaction," PM-1218-63882, Revision 0, nonproprietary version NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com L0-1218-63884

PM-1218-63882-NP Revision: 0 NuScale Nonproprietary Absorption Coefficient for Pool Water and Reactor Building Floor Interaction Tamas Liszkai, Heqin Xu Dylan Addison, J.J. Arthur Structures and Design Analysis 12119/2018 Copyright 2018 by NuScale Power, LLC.

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Outline

_* Review overall DCA seismic methodology

- Types of models

- Workflow

- Model interfaces

- High level physics

- Unique fluid-structure-interaction (FSI) considerations

Discuss limitation and conservatisms of DCA methodology regarding FSI

Discuss the basis of a reasonable approach to account for FSI in sub-structure analysis

Present results of absorption coefficient develop,ment 2

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DCA Seismic Analysis

Current methodology in NuScale DCA

- provides a reasonable and conservative evaluation of seismic loads/demand

- Conforms to NRC regulatory guidelines

Many complex interfaces between building and NPM models

Unique design of u,timate heat sink provides challenges for codes like SASSI

- Fluid structure interaction (FSI) plays significant role

- Large model size

- Deeply embedded structure

Inherent conservatism of multi-step process results in high design loads 3

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DCA Seismic Analysis Process

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Soil-Library Methodology

NuScale submitted for review a fully-coupled FSSI methodology for frequency domain analysis (TR-0118-58005)
Soil impedance from SASSI + ANSYS structural model +

ANSYS equation solver and post-processing

Functionally identical to SASSI except that it overcomes the limitations associated with lack of FSI capabilities
Uses one-step dynamic analysis for SSI of buildings, NPMs, and pool water 7

Option to Include Acoustic Fluid Damping"

Complex impedance boundary condition (BC) at the pool cut-boundary can be applied in which is the ratio between the pressure and normal particle velocity

- Development of exact BC of this kind is cumbersome and poses many challenges due to its frequency dependent nature and location dependency

Alternatively an absorption coefficient can be used which can reasonably represent the wave dissipation at the boundary
Absorption coefficient represents how much of the waves at the boundary are being reflected vs. absorbed
NuScale developed a conservative approach to determine a reasonable absorption coefficient for seismic analysis of the N PM 9

Key Takeaways

The use of absorption coefficient is to remedy limitations associated with sub-modeling using multiple software
Seismic analysis other than.the NPM has no use for absorption coefficient, soil structure integratron and fluid pressure impact on building design is considered separately
The NPM seismic 30 FSI model uses acoustic elements to correctly account for hydrodynamic mass of pool
Acoustic pressure in absence of fluid damping has high harmonic peak which is unrealistic at resonance conditions
Employing absorption coefficient to model dissipative phenomena is a reasonable approximation when computing structural response of NPM 10 PM-1218-63882-NP Revision: 0 Copyright 2018 by NuScale Power, LLC.

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Background===

Acoustic Elements used for FSI in the transient seismic model
RXB present in the SASSI model but not in the transient seismic model
Acoustic surface without FSI considered "rigid wall"

- Neumann BC

Absorption coefficient needed to account for energy absorption at acoustic element surface
No existing data available for FSI

- Limited literature in-air data shows AC depends on material, surface, thickness, frequency, etc - Range from 0.01 to 0.99 12 PM-1218-63882-NP Revision: 0 Copyright 2018 by NuScale Power, LLC. w ~~.?.~A~.~ - Template#: 0000-21727-F01 R4

Methodology (( 14 PM-1218-63882-NP Revision: O Copyright.2018 by NuScale Power, LLC. }}2(a),(c) M ~!J.~.~~-~s-Template #: 0000-21727-F01 R4

Conclusion

Iterative process to determine absorption coefficient that matches the response of the NPM at key locations with and without the surrounding building
Absorption coefficient of 0.7 generates similar peak responses independent of NPM location
For added conservatism a value of 0.4 is used for NPM analysis 25 PM-1218-63882-NP Revision: O Copyright 2018 by NuScale Power, LLC.

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ML18362A142

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