The RETRAN-03 code development effort is designed to overcome the major theoretical and practical limitations associated with the RETRAN-02 computer code. The major objectives of the development program are (a) to extend the range of analyses that can be performed with RETRAN, (b) to make the code more dependable and faster running, and (c) to have a more transportable code. The first two objectives are accomplished by developing new models and adding other models to the RETRAN-02 base code. The major model additions for RETRAN-03 are as follows:

  1. implicit solution methods for the steady-state and transient forms of the field equations
  2. additional options for the velocity difference equation
  3. a new steady-state initialization option for computing low-power steam generator initial conditions
  4. models for nonequilibrium thermodynamic conditions
  5. several special-purpose models.
The source code and the environmental library for RETRAN-03 are written in standard FORTRAN 77, which allows the last objective to be fulfilled. Some models in RETRAN-02 have been deleted in RETRAN-03. The changes between RETRAN-02 and RETRAN-03 are reviewed.