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gapTRISO

Description

Model for gap gas composition, volume, temperature and pressure for TRISO.

Formulation

Similar to the FRAPCON model in terms of main assumptions and algorithm used to calculate the gap volume. Check FRAPCON documentation for more information.

Warning

The volumes calculated and printed are in m3, and refer to the modeled geometry.

In addition the gapTRISO model calculates the production of CO using either the GA or Proksch models.

For the GA model, one has that:

\[ \begin{aligned} CO_{prod}=min(0.625, 1.64e^{\frac{-3311}{T}}) \end{aligned} \]

where:

  • \(CO_{prod}\) is produced CO per fission(atoms/fission),
  • \(T\) is temperature(K),
  • 0.625 is the limit set by PARFUME.

For the Proksch model, one has that:

\[ \begin{aligned} log\frac{O/F}{t^2}=-0.21-\frac{8500}{T} \end{aligned} \]

where:

  • \(O/F\) is oxygen release at the end of irradiation(atoms/fission),
  • \(t\) is irradiation time(days),
  • \(T\) is time-averaged particle surface temperature(K).

The maximum value of \(O/F\) is limited by the following expression:

\[ \begin{aligned} (O/F)_{max}=0.40f_U+0.85f_{Pu} \end{aligned} \]

where \(f_U\) and \(f_{Pu}\) are the fission fractions of \(^{235}U\) and \(^{239}Pu + ^{241}Pu\), respectively.

We assume that all the oxygen forms carbon monoxide, then \(CO_{prod}=O/F\).

Options

The TRISO class in OFFBEAT requires the user to set various parameters in gapGasOptions (a subdictionary of the solverDict) and gapGas (a dictionary in the 0/uniform/ folder), as described below.

Parameters in gapGasOptions:

heatSourceName Name of heat source field. It is Q by default.
COProductionModel CO production model, either Proksch (default) or GA.
model3D Is the model in 3D? Set to false by default.
bufferPorosity The porosity of buffer.
bufferZones Name of the zones corresponding to buffer material.
gapPatches Specifies the patches for the fuel-clad gap (e.g., fuelOuter cladInner).
gapVolumeOffset Offset for the initial gap volume (by default: 0.0).
gasReserveVolume Initial volume of reserve gas for gap pressure calculation (by default: 0.0).
gasReserveTemperature Initial temperature of reserve gas, in Kelvin (by default: 290). Alternatively the user can provide a time-dependent list using the following keyword
gasReserveTemperatureList If present it is read in place of gasReserveTemperature. It is a sub-dictionary used to provide a time-dependent table of reserve temperatures.
type Parameter of gasReserveTemperatureList subdictionary; it specifies the table type (table).
values Parameter of gasReserveTemperatureList subdictionary; it is a list of time-value pairs for temperature (e.g., [(0.0, 290), (100.0, 590)]).
outOfBounds Parameter of gasReserveTemperatureList subdictionary; it handles the method for out-of-bounds values (default: clamp).
interpolationScheme Parameter of gasReserveTemperatureList subdictionary; it selects the interpolation method between time points (e.g., linear).
includeCentralHole Toggles inclusion of central hole in the fuel (default: on).
includeDishes Toggles inclusion of dish geometry (default: on).

Parameters in gapGas:

massFractions Specifies the initial mass fractions of gases (Ar, He, Kr, Ne, Rn, Xe, CO).
gasPressureType Defines the method for gas pressure calculation (options: fromModel, fixed, or fromList).
gasPressure Fixed gas pressure value when gasPressureType is set to fixed.
gapPressureList Activated only if gasPressureType is set as fromList, this is a sub-dictionary used to provide a time-dependent table for gas pressure.
type Parameter of gapPressureList subdictionary; it specifies the table type (table).
values Parameter of gapPressureList subdictionary; it is a list of time-pressure pairs (e.g., [(0.0, 1e5), (100.0, 1e6)]).
outOfBounds Parameter of gapPressureList subdictionary; it handles the method for out-of-bounds values (default: clamp).
interpolationScheme Parameter of gapPressureList subdictionary; it specifies the interpolation method between time points (e.g., linear).

Usage

Here is a code snippet of the solverDict to be used for activating the FRAPCON gapGas model:

gapGas                  TRISO;

//... rest of solverDict

// Option subdict for gapGas model
gapGasOptions
{
    gapPatches ( bufferOuter ipycInner );
    bufferOuterPatches bufferOuter;
    bufferPorosity  0.4054;
    bufferZones     Buffer;
    COProductionModel  Proksch;
    model3D    false;
    gapVolumeOffset 0.0;
    gasReserveVolume 0.0;
    gasReserveTemperature 290;

    // // Alternatively one can provide a time dependent list
    // gasReserveTemperatureList
    // {
    //      type    table;
    //
    //        values
    //        (
    //            (0.0    290)
    //            (100.0  590)
    //        );
    //
    //        outOfBounds         clamp;     // optional out-of-bounds handling
    //        interpolationScheme linear;    // optional interpolation method
    // }
}

In gapGas file inside the time step folder (e.g. 0/uniform or 0/):

massFractions
{
    Ar 0;
    He 0;
    Kr 0;
    Ne 0;
    Rn 0;
    Xe 0;
    CO 0;
};

gasPressureType                 fromModel;// fixed;// fromList;
gasPressure                     0;

//  gapPressureList
//  {
//  type    table;
//
//      values
//      (
//          (0.0    1e5)
//          (100.0  1e6)
//      );

//      outOfBounds         clamp;     // optional out-of-bounds handling
//      interpolationScheme linear;    // optional interpolation method
//  }