EDA, Incorporated

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RELAP5/MOD3 is a "best estimate" system code suitable for the analysis of all transients and postulated accidents in Light Water Reactor (LWR) systems, including both large- and  small-break loss-of-coolant accidents (LOCAs) as well as the full range of operational transients.  The one dimensional RELAP5/MOD3 code is based on a non-homogeneous and non-equilibrium model for the two-phase system that is solved by a fast,  partially implicit numerical scheme to permit economical calculation of system transients.   As a part of the severe accident core meltdown code SCDAP/RELAP5, RELAP5/MOD3  describes the thermal hydraulic aspects of both LWR systems and of the degrading core. RELAP5 and the coupled version SCDAP/RELAP5 are being developed at INEEL.  

In addition, RELAP5 can be used to solve many plant thermal-hydraulic problems.  Modeling of single and two-phase systems can be accomplished using many types of valves, heat exchangers and pumps.  Using the best estimate (BE) code, RELAP5, for probabilistic safety analysis (PSA) has be performed with much success.

The code includes many generic models allowing to simulate general thermo hydraulic systems. The models include pumps, valves, pipes, heat releasing or absorbing structures, reactor point kinetics, electric heaters, jet pumps, turbines, separators, accumulators, and control system logic elements.  RELAP5 represents the aggregate accumulation of experience in modeling reactor core behavior during accidents, two-phase flow processes, and LWR systems. The code development has benefited from extensive application and validation against a lot of experimental programs.


Our Mission

EDA, Incorporated aspires to be the engineering leader in providing safe, reliable and economical solutions to challenging problems. 

Company Profile

EDA, Incorporated provides quality-engineering services on time, on schedule and within budget.  EDA, Inc. is able to do this by performing the work correctly the first time. We accept the most challenging problems and look forward to working with the client as a team member.  EDA believes that the client should be an active participant in the work process to ensure that the product is commensurate with client expectations and is delivered within schedule and budget constraints.

EDA, Inc. belongs to the National Society of Professional Engineers (NSPE), the American Society of Mechanical Engineers (ASME), the Society of Instrument Control Engineers, Society of Professional Engineers (ISA) and the American Nuclear Society (ANS).


Thank You for visiting EDA.  This site provides for your use free calculators/calculators in every engineering discipline.  We also provide extensive information on all engineering areas and on many different engineering groups.  In addition, a significant collection of computer information is provided.  Please visit our Specialties page to learn what services we provide.  Use our Search Page to find a specific topic.

For free calculations go to the Calculator page.  The calculators should be used with caution.  Some of these calculators are not verified and are only intended to provide a starting point in performing design calculations.  All final design calculations should  be performed using verified and validated programs.  For more information on this, please contact EDA, Inc.

For more information on EDA, Incorporated services, please contact Client Service Manager at:

Client Service Manager

EDA, Inc.

6397 True Lane

Springfield, VA 22150


or email  the Client Service Manager at .


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Contact Information

Virginia Office (703) 356-4149
Postal address
6397 True Lane
          Springfield, Va 22150
Electronic mail
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