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added input description for CMFD XML input file
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Bryan Herman
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1 changed files with 186 additions and 2 deletions
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@ -37,16 +37,19 @@ Overview of Files
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-----------------
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To assemble a complete model for OpenMC, one needs to create separate XML files
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for the geometry, materials, and settings. Additionally, there are two optional
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for the geometry, materials, and settings. Additionally, there are three optional
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input files. The first is a tallies XML file that specifies physical quantities
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to be tallied. The second is a plots XML file that specifies regions of geometry
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which should be plotted. OpenMC expects that these files are called:
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which should be plotted. The third is a CMFD XML file that specifies coarse mesh
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acceleration geometry and execution parameters. OpenMC expects that these
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files are called:
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* ``geometry.xml``
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* ``materials.xml``
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* ``settings.xml``
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* ``tallies.xml``
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* ``plots.xml``
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* ``cmfd.xml``
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--------------------------------------
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Settings Specification -- settings.xml
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@ -979,3 +982,184 @@ sub-elements:
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materials to plot. This overrides any ``col_spec`` color specifications.
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*Default*: None
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--------------------------------------------
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CMFD Specification -- cmfd.xml
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--------------------------------------------
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Coarse mesh finite difference acceleration method has been implemented in OpenMC.
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Currently, it allows users to accelerate fission source convergence during
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inactive neutron batches. To run CMFD, the ``<run_cmfd>`` element in
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``settings.xml`` should be set to ``.true.``.
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``<active_flush>`` Element
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--------------------------
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The ``<active_flush>`` element controls the batch where CMFD tallies should be
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reset. CMFD tallies should be reset before active batches so they are accumulated
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without bias.
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*Default*: 0
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``<begin>`` Element
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-------------------
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The ``<begin>`` element controls what batch CMFD calculations should begin.
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*Default*: 1
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``<feedback>`` Element
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----------------------
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The ``<feedback>`` element controls whether or not the CMFD diffusion result is
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used to adjust the weight of fission source neutrons on the next OpenMC batch.
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It can be turned on with ".true." and off with ".false.".
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*Default*: .false.
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``<inactive>`` Element
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----------------------
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The ``<inactive>`` element controls if cmfd tallies should be accumulated
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during inactive batches. For some applications, CMFD tallies may not be
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needed until the start of active batches. This option can be turned on
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with ".true." and off with ".false."
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*Default*: .true.
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``<keff_tol>`` Element
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----------------------
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The ``<keff_tol>`` element specifies acceptance criteria of a CMFD eigenvalue.
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If the CMFD eigenvalue and OpenMC batch eigenvalue are within this tolerance,
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CMFD is allowed to modify source neutron weights.
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*Default*: 0.005
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``<ksp_monitor>`` Element
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-------------------------
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The ``<ksp_monitor>`` element is used to view the convergence of linear GMRES
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iterations in PETSc. This option can be turned on with ".true." and turned off
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with ".false.".
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*Default*: .false.
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``<mesh>`` Element
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------------------
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If a structured mesh is desired as a filter for a tally, it must be specified in
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a separate element with the tag name ``<mesh>``. This element has the following
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attributes/sub-elements:
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:type:
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The type of structured mesh. Only "rectangular" is currently supported.
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:lower_left:
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The lower-left corner of the structured mesh. If only two coordinate are
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given, it is assumed that the mesh is an x-y mesh.
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:upper_right:
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The upper-right corner of the structrued mesh. If only two coordinate are
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given, it is assumed that the mesh is an x-y mesh.
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:dimension:
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The number of mesh cells in each direction.
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:width:
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The width of mesh cells in each direction.
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:energy:
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Energy bins [in MeV], listed in ascending order (e.g. 0.0 0.625e-7 20.0)
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for CMFD tallies and acceleration. If no energy bins are listed, OpenMC
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automatically assumes a one energy group calculation over the entire
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energy range.
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:albedo:
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Surface ratio of incoming to outgoing partial currents on global boundary
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conditions. They are listed in the following order: -x +x -y +y -z +z.
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*Default*: 1.0 1.0 1.0 1.0 1.0 1.0
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:map:
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An optional acceleration map can be specified to overlay on the coarse
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mesh spatial grid. If this option is used a ``1`` is used for a
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non-accelerated region and a ``2`` is used for an accelerated region.
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For a simple 4x4 coarse mesh with a 2x2 fuel lattice surrounded by
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reflector, the map is:
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``1 1 1 1``
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``1 2 2 1``
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``1 2 2 1``
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``1 1 1 1``
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Therefore a 2x2 system of equations is solved rather than a 4x4. This
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is extremely important to use in reflectors as neutrons will not
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contribute to any tallies far away from fission source neutron regions.
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A ``2`` must be used to identify any fission source region.
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.. note:: Only two of the following three sub-elements are needed:
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``lower_left``, ``upper_right`` and ``width``. Any combination
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of two of these will yield the third.
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``<norm>`` Element
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------------------
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The ``<norm>`` element is used to normalize the CMFD fission source distribution
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to a particular value. For example, if a fission source is calculated for a
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17 x 17 lattice of pins, the fission source may be normalized to the number of
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fission source regions, in this case 289. This is useful when visualizing this
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distribution as the average peaking factor will be unity. This parameter will
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not impact the calculation.
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*Default*: 1.0
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``<n_procs_cmfd>`` Element
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--------------------------
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The ``<n_procs_cmfd>`` element is used to set the number of processors used
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for CMFD calculation. It should be less than or equal to the number of
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processors used during OpenMC.
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*Default*: 1
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``<power_monitor>`` Element
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---------------------------
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The ``<power_monitor>`` element is used to view the convergence of power iteration.
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This option can be turned on with ".true." and turned off with ".false.".
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*Default*: .false.
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``<write_balance>`` Element
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---------------------------
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The ``<write_balance>`` element is used to view the balance of OpenMC tally
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residuals for every coarse mesh region and energy group. This option can be
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turned on with ".true." and off with ".false.".
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*Default*: .false.
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``<write_hdf5>`` Element
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------------------------
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The ``<write_hdf5>`` element can be turned on with ".true." to get an
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HDF5 output file of CMFD results.
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*Default*: .false.
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``<write_matrices>`` Element
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----------------------------
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The ``<write_matrices>`` element is used to view the PETSc sparse matrices
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created when solving CMFD equations. These binary output files can be imported
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into MATLAB using PETSc-MATLAB utilities. This option can be
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turned on with ".true." and off with ".false.".
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*Default*: .false.
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