9.6. Input and Output Description
The user interface for the MFUEL model consists of text input that is part of the SAS4A/SASSYS‑1 model file and text and binary output that is generated during a simulation. Existing input locations are used in conjunction with new input options to model the irradiation history, fuel specifications, and transient scenario.
Table 9.6.1 summarizes the input data that is utilized by the MFUEL
model and provides valid input ranges as appropriate. Note that some
of the existing input definitions have been updated such that they
can be used by the MFUEL model. MFUEL can be activated by setting
IFUELO = 2 for a given channel. In addition, IFUELM = 3 activates an
alternative thermal conductivity correlation recommended for use with
MFUEL. Since MFUEL simulates the fuel from the beginning of life, all
fuel pin geometry parameters in SAS input should be set to
as-fabricated conditions. Fuel porosity needs to be set to zero and
initial plenum pressure needs to set to as-fabricated gas pressure at
TR. Initial fuel composition should be provided as input. To model
the irradiation history, the existing MSTEP, PLIN, and TPLIN inputs
can be utilized, assuming that the SAS steady-state coolant flow rate
is the flow rate during irradiation. Users can also use the existing
TABLE block input format to define power and flow variations during
pre-transient irradiation as a function of time. This option is
utilized if MSTEP is set greater than 8, in which case MSTEP must
correspond to a valid TABLE block. A valid MFUEL table contains the
columns TIME, POWER, and FLOW, APRINT, where the entries for TIME are
defined in seconds, the entries for POWER are defined relative to
POWTOT, and the entries for FLOW are defined in kg/s per pin, APRINT
is used whether to skip (=1) or include (=0) printing of the axial
distribution data to binary output files for the relevant MFUEL
parameters.
Example irradiation history input using a TABLE Blocks:
TABLE 101 "T473 Pre-Transient History"
TIME POWER FLOW APRINT
0.00000E+00 2.78571E+00 4.95552E-02 0
2.96165E+06 2.78571E+00 4.95552E-02 1
2.96165E+06 2.73810E+00 5.06606E-02 0
5.31213E+06 2.73810E+00 5.06606E-02 0
5.31213E+06 2.83333E+00 5.06813E-02 0
8.10774E+06 2.83333E+00 5.06813E-02 0
8.10774E+06 2.85714E-01 4.81279E-02 0
8.15276E+06 2.85714E-01 4.81279E-02 0
8.15276E+06 2.85714E-01 4.81279E-02 1
8.24237E+06 2.85714E-01 4.81279E-02 0
8.24237E+06 1.96599E+00 5.03524E-02 0
8.59148E+06 1.96599E+00 5.03524E-02 0
8.59148E+06 3.33333E+00 6.50261E-02 0
8.67860E+06 3.33333E+00 6.50261E-02 0
8.67860E+06 2.76190E+00 4.99568E-02 1
9.64807E+07 1.00000E+00 4.85789E-02 1
9.65389E+07 1.00000E+00 4.85789E-02 1
END
Variable Name |
|---|
MFUEL prints detailed steady state and transient results for the fuel
characterization to standard SAS output.
IF IDSSC input is set to 1, steady-state
results will be printed for each user-controlled coarse time step.
Otherwise, only end of steady state simulation results will be printed.
Users has the ability to print results with a desired frequency for
steady-state and transient simulations. Steady-state print frequency can
be controlled by the size of the power/flow Table. Transient print
frequency can be controlled by IPO and
IPOBOI inputs. In addition to standard
output, each SAS run with MFUEL activation creates binary files for each
channel storing the peak values of essential parameters at every time
step. Steady-state and transient binary files including the peak values
of relevant parameters as a function of time are named as
MFUELss_Ci.dat and MFUELts_Ci.dat, respectively where i is the
channel number. Steady-state binary file including the axial
distribution of the relevant parameters as time snapshots is named as
MFUELss_Ci-axial.dat.