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Engineering Mechanics

Seismic Analysis

Finite Element Analysis/Computational Fluid Dynamics

Heat Transfer

Piping/Support Design and Analysis

Computer Modeling

Seismic Analysis

The Great Tohoku (M9.0) and Mineral, VA (M5.8) earthquakes demonstrated that while beyond design basis events were unlikely, they could still occur. These events, along with the development of updated design ground motion response spectra for the central and eastern US as part of the CEUS effort, have spurred plants to reexamine their seismic vulnerability.

This entails characterizing the new seismic event, comparing it with the existing design basis event, and assessing impact using probabilistic risk assessment. As a result of characterization, some systems, structures and components may require qualification for increased seismic loads.

Altran engineers are experienced in seismic load development (time histories or response spectra), as well as structural analysis and code qualification of buildings/structures, piping systems and components, and mechanical and electrical equipment.  As veteran engineers, we can bring to bear a deep understanding of plant SSCs, design codes and analysis methods. We focus on qualification with minimal field modifications; we do this by evaluating and removing existing conservatism, ensuring accurate design basis inputs, using sophisticated analyses if required and examining the impact of other loads, such as fluid transients.

Finite Element Analysis/Computational Fluid Dynamics

Altran engineers use Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) to model complex structural, electrical, thermodynamic and fluid problems with greater detail and accuracy. We use our expertise and broad experience in structural analysis, fluids/heat transfer and materials to validate and understand FEA and CFD results. We can create visual simulations that illustrate system, structure or component behavior. Our materials laboratory allows us to verify material behavior with full-scale or scaled models.

FEA/CFD applications include:

  • Structural dynamic response: vibration, shock, seismic, impact
  • Non-linear materials: plasticity and large deflection
  • Mechanical and thermal stress analysis
  • Material fracture and fatigue
  • Thermodynamic analysis and heat transfer
  • Simulations
  • Fluid flow visualization and characterization; waterhammer and transients, vortex shedding
  • Acoustic analysis

Altran engineers use ANSYS, ANSYS CFX, STAADPro, STRUDL, SAP, FLOTRAN, RELAP, NUPIPE and ADLPIPE commercial codes, as well as internally developed applications based on MathCAD and Visual Basic.

Heat Transfer

Altran can provide fully integrated thermal performance evaluations by combining the expertise of its consultant engineers with the use of advanced scientific laboratory analysis in order to determine power and efficiency losses in your system. Maximizing the thermal energy conversion process will result in significant cost savings within a short turnaround time. Our engineers are highly experienced in all aspects of "megawatt hunting" and have direct access to Altran's in-house, advanced microbiological testing laboratory. These resources ensure a complete and comprehensive analysis of your power and efficiency losses.

Altran's Thermal Performance Evaluation is comprised of many phases and analyses including:

  • Core Thermal Power Analysis
  • Instrument Uncertainty Analysis
  • Integrated System Modeling (PEPSE Computer Modeling)
  • Overall Turbine Performance Evaluation, including pressure-ratio evaluation
  • First-Stage Turbine Pressure Analysis
  • Condenser Performance Analysis, which includes studies for Condenser Cleanliness, Evidence of Fouling and Scaling and Microbiological Water Sampling
  • Feedwater Heater System Efficiency Seasonal  Performance Evaluation
  • Cycle Isolation Component Analysis, including AOV, MOV and other valve leakage evaluations
  • Feedwater / condensate chemistry analysis (including radioactive sampling capabilities) for impact on component heat transfer characteristics and feedwater element fouling

This integrated evaluation and consultation can be completed in a short time period and can result in significant cost savings and increase in power output.

Piping/Support Design and Analysis

Since our inception, Altran engineers have designed, evaluated and qualified nuclear and fossil plant piping systems using a combination of technical expertise, knowledge of industry codes and plant systems, as well as experience in the range of analytical methods. We can use span tables to hang new lines and hand calculations to qualify proposed modifications quickly and inexpensively; we can also model entire systems to analyze a number of loads and load combinations.

Analysis usually includes dead weight, thermal, seismic, anchor movements and dynamic events. Altran has particular expertise in transient load formulation (e.g., waterhammer events) as well as seismic load development. Detailed evaluations are performed to qualify all types of integral welded attachments to piping components using the AltraLug™ program for simple lugs and ANSYS™ for complex attachments. We perform fatigue analyses for thermal and structural loads, and evaluations of equipment nozzles, penetrations, valves and flanges.

For nuclear safety-related systems, design and analysis services are performed under Altran’s Nuclear Quality Assurance Program. Our QA program is compliant with 10CFR50, App. B and ASME/ANSI NQA-1, and has been audited by NUPIC. For non-safety related and non-nuclear systems, our work is prepared under the same standard of care.

Our engineers use special finite element analysis software such as ADLPIPE, AutoPIPE™, NUPIPE™, and ME101™ to model piping systems and perform code qualifications. These are enhanced with the use of AltraLug™ for local welded attachments, ANSYS™ for specialized components, and PD STRUDL™ and SAP for support evaluation and qualification. For characterization of fluid transients, we use a number codes including RELAPV, GOTHIC, ALGOR and CFX.

We can draw upon extensive code expertise, with experience in the use of ASME Boiler & Pressure Vessel Code Section III, Subsections NB, NC, and ND for Class 1, 2, and 3 piping, ANSI B31.1 Code for Power Piping, ANSI B31.3 Code for Process Piping, ANSI B31.1 Non-Mandatory Appendix VII for Buried Piping Design, as well as specialized ASME code cases for specialized applications such as cured-in-place pipe (CIPP) and HDPE piping.

Altran engineers have participated in many industry groups that developed guidelines for qualification of piping systems including Welding Research Council Bulletin 316, "Technical Position on Piping Installation Tolerances," and Nuclear Construction Issues Group NCIG-05 "Guidelines for Piping System Reconciliation.” An Altran staff member authored the chapter on steam systems piping in the Piping Handbook, 7th Edition. Altran engineers have also prepared criteria and methodology documents for piping stress analysis and pipe support qualification for use at several nuclear power plants.

Computer Modeling

Computer simulations are typically used to obtain a higher level of accuracy to solutions of complex problems as compared to simplified manual calculations. Altran engineers capitalize on their knowledge of the fundamentals of physics and engineering principles to develop accurate models and make the right interpretation of the results. We appreciate the role of knowledge and experience in technical theory and computer modeling science and thus avoid pitfalls typically encountered by black-box users.

Computer simulations are used for a wide range of applications such as solid state mechanics, thermal hydraulic, open and close channel flow, state interaction, natural and forced convection problems. We take advantage of in-house test capabilities to benchmark simulations to achieve reliable numerical solutions.

Scot Blodgett, Vice President of Nuclear

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