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  4. TransAT CD&S


TransAT CD&S is an advanced system-code model developed at ASCOMP’s Nuclear Energy Division, providing a full evaluation of core parameters at a given loading pattern for light water reactors LWR’s. The model consists of a fully coupled 3D neutronics to 1D thermal hydraulics solution, and has the major advantage of considering a realistic model of the reactor (all core assemblies, lower and upper plenums, riser, steam separators, dome, downcomer) and its recirculation loop. The 3D neutronics equations (two energy groups with six precursor groups), rod conduction equation, and flow conservation equations (non-homogenous, non-equilibrium) constitute the main set of equations.

Physics and Workflow

A flow distribution among the assemblies is made automatically according to power and pressure drop level of each assembly. Stability of BWRs could be analyzed using frequency dependent equations and solve the system matrix for the for the state variables perturbations. Code is interfaced to reactor simulator for getting input data and verification of some of the results. Software usage is not limited only light water reactors. It has been implement in oil industry for stability of large heat exchangers.


TransAT-CD&S requires the following input data:

  • Reactor and assemblies geometries
  • Materials
  • Core configuration
  • Boundary condition (flows, pressure, total power)
  • Reactor distribution and Master files (for automatic reading information)

TransAT-CD&S provides the following output data:

  • Full 3D steady state results of reactor (both neutronics and thermalhydraulics)
  • Full 3D perturbation results
  • Reactor stability results (Decay ratio, resonance frequency, Nyquist diagram of system transfer function)

Contact TransAT Suite Team