Critical Structures & Facilities

SI is an expert in evaluating critical structures and facilities for normal operating loads and extreme events. Some of the largest utilities and engineering companies in the world have looked to SI for seismic and advanced structural analysis solutions including root cause analysis, equipment qualifications, non-linear steel and concrete modeling, material aging and degradation, dynamic and non-linear seismic analysis, soil-structure interaction, and equipment/structure fragility analysis. Our capabilities include the use of explicit software programs that model load drops, tornado missile impacts, fluid-structure interaction, barrier design, shock propagation and isolation system design, and blast protective design. Our services are unique in that we provide seismic qualification of equipment through both analysis and shake table testing.

Qualification of Diesel Engine Aftercoolers for Nuclear Services

We evaluated components of an emergency diesel generator system under operating conditions and for the operating plus seismic loading condition.

The model generated for analysis of the aftercoolers is shown below. A Computer Aided Design (CAD) model of the intercoolers was imported into ANSYS Workbench for analysis. We applies custom mesh sizing and mesh transition controls to produce accurate results.

Acoustic Analysis of Recirculation Line Outlet Break

Acoustic loads are transient pressure loads which propagate within the coolant, inside the reactor pressure vessel (RPV). These loads are caused by the rapid depressurization of the coolant at the postulated break plane.

At the instant after the postulated break, a decompression front propagates upstream into the RPV. This decompression front contributes fluctuating pressure loads to RPV internal components. We use fluid models like the one shown below to determine the pressure response of the boiling water reactor (BWR) annulus. The resulting loads are superimposed with other dynamic and static loads to assess shroud loads and allowable flaw sizes. SI has a full line of offerings related to BWR Internals.

Case Study

Repair Hardware for Hydroeletric Dam Gate Hoist

SI assisted a hydroelectric utility to design a repair option for a lift hoist hub that had cracked. The hoist lifts an emergency overflow gate and operability of the hoist had to be determined. A repair clamp was designed by SI and an ANSYS analysis was performed to show that the clamp provided sufficient structural margin and the hoist could perform its function. Contact elements were used to accurately model the lifting axel and hub interface. Bolt preload was applied to the repair clamp and the repair clamp was analyzed for structural strength as well as the hub. This analysis enabled the utility to continue to operate the hoist without have to replace a large and costly component.

Cracked Hub
Repair Clamp
Model of Repair

Case Study

Diesel Engine Turbo Charger with Cracked Blade

SI performed an analysis of a turbo charger nozzle for a nuclear power plant emergency diesel generator. The turbo charger was found cracked and was replaced, but a past operability analysis was needed. SI developed a CAD model of the “as found” turbo charger nozzle and performed analysis in ANSYS with different mechanical and thermal loading. Crack initiation locations were identified and a comparison of design and as found conditions was made to show that the cracked condition did not pose a threat to plant safety. This entire project was completed in just a few days and shows the rapid response and modeling expertise SI brings to the table.

Case Study

Evaluation of a Standby Service Water Cooling Tower

SI evaluated the benefit of replacing ceramic fill with a stainless steel alternative and performed ACI design checks to verify the adequacy of a structural retrofit. SI determined that replacing the fill increases margins from at the critical connections and members, and that the retrofit plans met design criteria.

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