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SAS4A/SASSYS-1 runs as a command-line tool in Unix or Linux shells (including Mac OS X) or as a DOS executable at the Windows command prompt.

Input File

A text-based input file that describes the problem to be solved is required for all SAS4A/SASSYS-1 calculations. This text file is read from standard input. An optional binary restart file must also be provided if a simulation is being restarted from a previously saved state.


A simulation may be continued from where it ended if an input file with a RESTART declaration is provided along with an existing restart file generated by a prior execution. SAS4A/SASSYS-1 makes a distinction between an output and an input restart file:

RESTART File (RESTART.dat) — output 
This RESTART file is created by SAS4A/SASSYS-1 and it contains all of the data needed to continue a calculation from where it left off. RESTART files are saved at the end of steady-state initialization and after every NSTEP main time steps. If NSTEP is zero, no restart files are saved.
RESTART File (RESTART.bin) — input 
A binary input RESTART file must be provided by the user if a simulation is being restarted from a previously saved state. For example, a saved RESTART file may be copied from RESTART.dat to RESTART.bin. An appropriate restart input file must be provided on standard input.

Output Files

SAS4A/SASSYS-1 generates one or more output files depending on user-defined options. Most output is written to the terminal (standard output). Other common output files include the following:

Log messages containing status updates are written to this file. Processing of the user-supplied input is also recorded in this file to reduce the overhead in the standard output.
A compiled version of the user-supplied input is optionally written to this file. Because user-defined input found later in a model file can overwrite input defined earlier in the input file, model data can change during input processing. This file contains the final state of all user-defined input. To generate this file, set IPDECK > 0 on the Storage Allocation Record.
Binary, channel-dependent data is written to a channel data file. Data written to this file include core fission power, decay heat, and reactivity feedback contributions and channel-dependent fuel, cladding, coolant, and structure temperatures. Input options that control the frequency of data written to this file include ICLCMP, MSTPLA, MSTPLB, MSTPL1, MSTPL2, and MSTPL3. Channel-dependent options that control the location of temperature reports include JCLN, JNEN, JNCN, and JNSN for fuel, cladding, coolant, and structure node locations, respectively. If ICLCMP = 0, this file is not written.
Binary data for selected PRIMAR-4 results. The selection of primary and intermediate coolant system results is controlled by user-supplied input defined for NBINOT, IBINOT, and IBINST. If NBINOT = 0, this file is not generated. IBINST controls the time-step interval (frequency) for writing results to this file.