9.5. Interactions with Other SAS Models
The pre-transient characterization driver of MFUEL_SSInit is called from main steady-state driver routine of SAS (SSTHRM). For each fuel channel with MFUEL activated, MFUEL_SSInit is called only once. The time loop to simulate pre-transient history is handled by MFUEL. Steady state thermal-hydraulics routines are called from MFUEL at every coarse time step. At the end of pre-transient characterization, fuel pin, flow area and axial height are updated to be used for the thermalhydraulics and reactivity feedback models during the transient. During the transient, at each heat transfer time step, MFUEL_TsStep is called explicitly from transient driver of SAS (TSTHRM). At each time step, the fuel and clad reactivity feedback is computed due to axial height change of fuel and cladding computed by MFUEL, respectively. MFUEL calculation directly affects the fuel thermal conductivity, coolant flow area, and fuel and clad reactivity feedback.
Currently, coupling of MFUEL with coolant boiling (BOIL), pre-failure molten fuel in-pin fuel relocation (PINACLE), and post-failure fuel dispersal (LEVITATE) models has not been accomplished. Therefore, these models cannot be used if MFUEL is activated.
A new class structure is created to support MFUEL data storage and fuel performance simulations. Table 9.5.1 describes the high-level procedures within the MFUEL class. In order to reduce the complexity of the MFUEL class, additional classes are defined for the fuel clad chemical interaction and Zr redistribution models, described in Table 9.5.2 and Table 9.5.3, respectively.
The new MFUEL model interfaces with the existing SAS models by accessing the CHAN data structure and the common blocks. At a high level, the MFUEL model accesses the fuel pin temperature and geometry. Following pre-transient characterization, the MFUEL model updates the fuel pin geometry stored within the CHAN data structure. During transient analysis, SAS utilizes the updated fuel pin geometry and composition to solve for the fuel pin temperature. The fuel composition is stored within the MFUEL data structure and made accessible to the SAS material property routines.
MFUEL_BaseCH Method |
Description |
|---|---|
Init(ICH) |
Initializes the memory and MFUEL model variables for channel ICH. |
Release() |
Releases the MFUEL data objects that were initialized during Init. |
WriteDAT(unit) |
Writes model specific restart data into unit. |
ReadDAT(unit) |
Reads model specific restart data from unit. |
SSInit() |
Simulates the pre-transient metal fuel behavior up to transient initialization. See Figure 9.4.1. |
SSPrint() |
Prints the MFUEL results and standard channel output at steady state. |
TSStep() |
Given a transient heat transfer time step, MFUEL computes the metal fuel behavior. See Figure 9.4.2. |
TSPrint() |
Prints MFUEL transient results. |
FuelThermCond(i,j,T) |
Computes the irradiated fuel thermal conductivity for node (i,j) at temperature T. Used if |
GetExpansionReactivity(rhoFuel,rhoClad) |
Compute fuel, rhoFuel, and clad, rhoClad, reactivity change due to axial expansion or contraction. |
FCCI Method |
Description |
|---|---|
Init() |
Initializes FCCI model with a refined mesh relative to the SAS frame. |
WriteDAT(unit) |
Writes model specific restart data to unit. |
ReadDAT(unit) |
Reads model specific restart data from unit. |
ActivateFCCI() |
Activates fuel clad chemical interaction (actinide migration) within the LaMigration procedure and sets the boundary radial node between fuel and cladding. |
UpdateGeometry() |
Update FCCI mesh based on SAS frame. FCCI Mesh is always extended to the inner cladding wall. |
UpdateTemperature() |
Update FCCI temperatures based on temperatures in SAS frame. |
LaMigration() |
Computes the migration of lanthanides due to diffusion and clad inner wastage due to lanthanide precipitation. |
FeMigration() |
Computes the migration of iron, iron phase formation in the fuel and eutectic penetration into the cladding. |
NaCorrosion() |
Computes the clad outer wastage due to sodium corrosion. |
GetFuelData(fData) |
Transform data from the FCCI mesh to the SAS mesh. |
FCRD Method |
Description |
|---|---|
Init() |
Initializes FCRD model with a refined mesh relative to the SAS frame. |
WriteDAT() |
Writes model specific values calculated during steady-state initialization into RESTART.dat. |
ReadDAT() |
Reads model specific values from RESTART.bin. |
UpdateGeometry() |
Update FCRD mesh based on SAS frame. |
UpdateTemperature() |
Update FCRD temperatures based on temperatures in SAS frame. |
ZrMigration() |
Computes the migration of Zirconium due to concentration and temperature gradient driving force. |
GetFuelData() |
Get U and Zr atom fraction on the SAS frame. |
SwellDriver Method |
Description |
|---|---|
MFUEl_swell() |
Computes fission gas and gas bubble behavior, swelling and release and solid fission product swelling. |
MFUEL_creep() |
Computes the creep induced hot pressing (pressure sintering) behavior of the fuel slug and irradiation/thermal creep, void swelling behavior of the cladding. |
PoreYieldStress() |
Computes the pore sintering yield stress. |
StresDriver Method |
Description |
|---|---|
StresDriver() |
Driver to call fuel pin mechanical analysis and update the fuel pin and coolant area geometry. |
MFUEL_stress() |
Given the strain components, it computes the fuel pin stress distribution and radial/axial displacements. |
Contak() |
Computes the contact stress between fuel and cladding. |
Method |
Description |
|---|---|
BurnupDriver() |
Computes fuel burnup (at. fraction). |
ExpanDriver() |
Compute fuel and cladding incremental thermal expansion strain. |
MCFDriver() |
Computes mechanistic creep failure margin for the HT9 cladding only. |
CLAD_props |
Includes functions and subroutines for cladding irradiation, thermal creep, void swelling, thermal expansion, elastic constants, and CDF clad failure margin. |
MFUEL_props |
Fuel phase transition temperatures, empirical eutectic penetration model, and fuel elastic constants. |
MFUEL_Parameters |
Includes constant parameters for all models. |
MFUEL_Data |
Includes the derived data types for all models. |