Aiken, SC

Savannah River Site, Pit Disassembly and Conversion Facility


The U.S. Department of Energy (DOE), in conjunction with the National Nuclear Security Administration’s Office of Fissile Materials Disposition, planned to eliminate stockpiles of weapons-grade, highly enriched uranium by down-blending the material to low-enriched uranium.  In support of Washington Group International’s structural design, SGH performed seismic soil-structure interaction (SSI) studies of the new pit disassembly and conversion facility.

The facility consists of large and closely spaced reinforced concrete buildings connected by buried tunnels.  Certain buildings are buried or covered by berms, while others are above grade with uneven soil support.  The facility is founded on deep soil layers with rock deeper than 800 ft.  With these conditions, the seismic SSI analysis became an important requirement for the structural design process.  Highlights of SGH’s work on the project include the following:

  • Performed seismic SSI analyses of five new Performance Category 3 (PC-3) buildings and tunnels, consisting of four reinforced concrete structures and one  concrete and steel structure
  • Performed seismic structure-soil-structure interaction analysis of closely spaced structures
  • Performed analyses using SASSI, verified in accordance with SGH’s Quality Assurance program for nuclear facilities
  • Developed post-processor for SASSI to calculate deformed shape-time histories during the seismic event
  • Presented the SSI methodology and analysis results to the DOE and the Defense Nuclear Facilities Safety Board

Project Summary



Completion Date


New Construction
Structures | Advanced Analysis
Science & Defense
Washington Group International
Specialized Capabilities
Seismic Engineering | Nuclear | Computational Mechanics

Key team members

Mehdi Zarghamee
Mehdi Zarghamee
Senior Principal
Said Bolourchi
Said Bolourchi
Senior Principal