Random Ray Transport (#2823)

Co-authored-by: Gavin Ridley <[email protected]>
Co-authored-by: Paul Romano <[email protected]>

CMakeLists.txt

@@ -380,6 +380,9 @@ list(APPEND libopenmc_SOURCES
   src/progress_bar.cpp
   src/random_dist.cpp
   src/random_lcg.cpp
+  src/random_ray/random_ray_simulation.cpp
+  src/random_ray/random_ray.cpp
+  src/random_ray/flat_source_domain.cpp
   src/reaction.cpp
   src/reaction_product.cpp
   src/scattdata.cpp

docs/source/io_formats/settings.rst

@@ -413,6 +413,32 @@ or sub-elements and can be set to either "false" or "true".
 
   .. note:: This element is not used in the multi-group :ref:`energy_mode`.
 
+------------------------
+``<random_ray>`` Element
+------------------------
+
+The ``<random_ray>`` element enables random ray mode and contains a number of
+settings relevant to the solver. Tips for selecting these parameters can be
+found in the :ref:`random ray user guide <random_ray>`.
+
+  :distance_inactive:
+    The inactive ray length (dead zone length) in [cm].
+
+    *Default*: None
+
+  :distance_active:
+    The active ray length in [cm].
+
+    *Default*: None
+
+  :source:
+    Specifies the starting ray distribution, and follows the format for
+    :ref:`source_element`. It must be uniform in space and angle and cover the
+    full domain. It does not represent a physical neutron or photon source -- it
+    is only used to sample integrating ray starting locations and directions.
+
+    *Default*: None
+
 ----------------------------------
 ``<resonance_scattering>`` Element
 ----------------------------------

docs/source/methods/index.rst

@@ -20,3 +20,4 @@ Theory and Methodology
     energy_deposition
     parallelization
     cmfd
+    random_ray

docs/source/usersguide/data.rst

@@ -279,6 +279,8 @@ The `official ENDF/B-VII.1 HDF5 library
 multipole library, so if you are using this library, the windowed multipole data
 will already be available to you.
 
+.. _create_mgxs:
+
 -------------------------
 Multigroup Cross Sections
 -------------------------

docs/source/usersguide/index.rst

@@ -25,4 +25,6 @@ essential aspects of using OpenMC to perform simulations.
     processing
     parallel
     volume
+    random_ray
     troubleshoot
+

examples/pincell_random_ray/build_xml.py

@@ -0,0 +1,203 @@
+import numpy as np
+import openmc
+import openmc.mgxs
+
+###############################################################################
+# Create multigroup data
+
+# Instantiate the energy group data
+group_edges = [1e-5, 0.0635, 10.0, 1.0e2, 1.0e3, 0.5e6, 1.0e6, 20.0e6]
+groups = openmc.mgxs.EnergyGroups(group_edges)
+
+# Instantiate the 7-group (C5G7) cross section data
+uo2_xsdata = openmc.XSdata('UO2', groups)
+uo2_xsdata.order = 0
+uo2_xsdata.set_total(
+    [0.1779492, 0.3298048, 0.4803882, 0.5543674, 0.3118013, 0.3951678,
+     0.5644058])
+uo2_xsdata.set_absorption([8.0248e-03, 3.7174e-03, 2.6769e-02, 9.6236e-02,
+                           3.0020e-02, 1.1126e-01, 2.8278e-01])
+scatter_matrix = np.array(
+    [[[0.1275370, 0.0423780, 0.0000094, 0.0000000, 0.0000000, 0.0000000, 0.0000000],
+      [0.0000000, 0.3244560, 0.0016314, 0.0000000, 0.0000000, 0.0000000, 0.0000000],
+      [0.0000000, 0.0000000, 0.4509400, 0.0026792, 0.0000000, 0.0000000, 0.0000000],
+      [0.0000000, 0.0000000, 0.0000000, 0.4525650, 0.0055664, 0.0000000, 0.0000000],
+      [0.0000000, 0.0000000, 0.0000000, 0.0001253, 0.2714010, 0.0102550, 0.0000000],
+      [0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.0012968, 0.2658020, 0.0168090],
+      [0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.0085458, 0.2730800]]])
+scatter_matrix = np.rollaxis(scatter_matrix, 0, 3)
+uo2_xsdata.set_scatter_matrix(scatter_matrix)
+uo2_xsdata.set_fission([7.21206e-03, 8.19301e-04, 6.45320e-03,
+                        1.85648e-02, 1.78084e-02, 8.30348e-02,
+                        2.16004e-01])
+uo2_xsdata.set_nu_fission([2.005998e-02, 2.027303e-03, 1.570599e-02,
+                           4.518301e-02, 4.334208e-02, 2.020901e-01,
+                           5.257105e-01])
+uo2_xsdata.set_chi([5.8791e-01, 4.1176e-01, 3.3906e-04, 1.1761e-07, 0.0000e+00,
+                    0.0000e+00, 0.0000e+00])
+
+h2o_xsdata = openmc.XSdata('LWTR', groups)
+h2o_xsdata.order = 0
+h2o_xsdata.set_total([0.15920605, 0.412969593, 0.59030986, 0.58435,
+                      0.718, 1.2544497, 2.650379])
+h2o_xsdata.set_absorption([6.0105e-04, 1.5793e-05, 3.3716e-04,
+                           1.9406e-03, 5.7416e-03, 1.5001e-02,
+                           3.7239e-02])
+scatter_matrix = np.array(
+    [[[0.0444777, 0.1134000, 0.0007235, 0.0000037, 0.0000001, 0.0000000, 0.0000000],
+      [0.0000000, 0.2823340, 0.1299400, 0.0006234, 0.0000480, 0.0000074, 0.0000010],
+      [0.0000000, 0.0000000, 0.3452560, 0.2245700, 0.0169990, 0.0026443, 0.0005034],
+      [0.0000000, 0.0000000, 0.0000000, 0.0910284, 0.4155100, 0.0637320, 0.0121390],
+      [0.0000000, 0.0000000, 0.0000000, 0.0000714, 0.1391380, 0.5118200, 0.0612290],
+      [0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.0022157, 0.6999130, 0.5373200],
+      [0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.0000000, 0.1324400, 2.4807000]]])
+scatter_matrix = np.rollaxis(scatter_matrix, 0, 3)
+h2o_xsdata.set_scatter_matrix(scatter_matrix)
+
+mg_cross_sections_file = openmc.MGXSLibrary(groups)
+mg_cross_sections_file.add_xsdatas([uo2_xsdata, h2o_xsdata])
+mg_cross_sections_file.export_to_hdf5()
+
+###############################################################################
+# Create materials for the problem
+
+# Instantiate some Materials and register the appropriate macroscopic data
+uo2 = openmc.Material(name='UO2 fuel')
+uo2.set_density('macro', 1.0)
+uo2.add_macroscopic('UO2')
+
+water = openmc.Material(name='Water')
+water.set_density('macro', 1.0)
+water.add_macroscopic('LWTR')
+
+# Instantiate a Materials collection and export to XML
+materials_file = openmc.Materials([uo2, water])
+materials_file.cross_sections = "mgxs.h5"
+materials_file.export_to_xml()
+
+###############################################################################
+# Define problem geometry
+
+# The geometry we will define a simplified pincell with fuel radius 0.54 cm
+# surrounded by moderator (same as in the multigroup example).
+# In random ray, we typically want several radial regions and azimuthal
+# sectors in both the fuel and moderator areas of the pincell. This is
+# due to the flat source approximation requiring that source regions are
+# small compared to the typical mean free path of a neutron. Below we
+# sudivide the basic pincell into 8 aziumthal sectors (pizza slices) and
+# 5 concentric rings in both the fuel and moderator.
+
+# TODO: When available in OpenMC, use cylindrical lattice instead to
+# simplify definition and improve runtime performance.
+
+pincell_base = openmc.Universe()
+
+# These are the subdivided radii (creating 5 concentric regions in the
+# fuel and moderator)
+ring_radii = [0.241, 0.341, 0.418, 0.482, 0.54, 0.572, 0.612, 0.694, 0.786]
+fills = [uo2, uo2, uo2, uo2, uo2, water, water, water, water, water]
+
+# We then create cells representing the bounded rings, with special
+# treatment for both the innermost and outermost cells
+cells = []
+for r in range(10):
+    cell = []
+    if r == 0:
+        outer_bound = openmc.ZCylinder(r=ring_radii[r])
+        cell = openmc.Cell(fill=fills[r], region=-outer_bound)
+    elif r == 9:
+        inner_bound = openmc.ZCylinder(r=ring_radii[r-1])
+        cell = openmc.Cell(fill=fills[r], region=+inner_bound)
+    else:
+        inner_bound = openmc.ZCylinder(r=ring_radii[r-1])
+        outer_bound = openmc.ZCylinder(r=ring_radii[r])
+        cell = openmc.Cell(fill=fills[r], region=+inner_bound & -outer_bound)
+    pincell_base.add_cell(cell)
+
+# We then generate 8 planes to bound 8 azimuthal sectors
+azimuthal_planes = []
+for i in range(8):
+    angle = 2 * i * openmc.pi / 8
+    normal_vector = (-openmc.sin(angle), openmc.cos(angle), 0)
+    azimuthal_planes.append(openmc.Plane(a=normal_vector[0], b=normal_vector[1], c=normal_vector[2], d=0))
+
+# Create a cell for each azimuthal sector using the pincell base class
+azimuthal_cells = []
+for i in range(8):
+    azimuthal_cell = openmc.Cell(name=f'azimuthal_cell_{i}')
+    azimuthal_cell.fill = pincell_base
+    azimuthal_cell.region = +azimuthal_planes[i] & -azimuthal_planes[(i+1) % 8]
+    azimuthal_cells.append(azimuthal_cell)
+
+# Create the (subdivided) geometry with the azimuthal universes
+pincell = openmc.Universe(cells=azimuthal_cells)
+
+# Create a region represented as the inside of a rectangular prism
+pitch = 1.26
+box = openmc.model.RectangularPrism(pitch, pitch, boundary_type='reflective')
+pincell_bounded = openmc.Cell(fill=pincell, region=-box, name='pincell')
+
+# Create a geometry (specifying merge surfaces option to remove
+# all the redundant cylinder/plane surfaces) and export to XML
+geometry = openmc.Geometry([pincell_bounded], merge_surfaces=True)
+geometry.export_to_xml()
+
+###############################################################################
+# Define problem settings
+
+# Instantiate a Settings object, set all runtime parameters, and export to XML
+settings = openmc.Settings()
+settings.energy_mode = "multi-group"
+settings.batches = 600
+settings.inactive = 300
+settings.particles = 50
+
+# Create an initial uniform spatial source distribution for sampling rays.
+# Note that this must be uniform in space and angle.
+lower_left = (-pitch/2, -pitch/2, -1)
+upper_right = (pitch/2, pitch/2, 1)
+uniform_dist = openmc.stats.Box(lower_left, upper_right)
+settings.random_ray['ray_source'] = openmc.IndependentSource(space=uniform_dist)
+settings.random_ray['distance_inactive'] = 40.0
+settings.random_ray['distance_active'] = 400.0
+
+settings.export_to_xml()
+
+###############################################################################
+# Define tallies
+
+# Create a mesh that will be used for tallying
+mesh = openmc.RegularMesh()
+mesh.dimension = (2, 2)
+mesh.lower_left = (-pitch/2, -pitch/2)
+mesh.upper_right = (pitch/2, pitch/2)
+
+# Create a mesh filter that can be used in a tally
+mesh_filter = openmc.MeshFilter(mesh)
+
+# Let's also create a filter to measure each group
+# indepdendently
+energy_filter = openmc.EnergyFilter(group_edges)
+
+# Now use the mesh filter in a tally and indicate what scores are desired
+tally = openmc.Tally(name="Mesh and Energy tally")
+tally.filters = [mesh_filter, energy_filter]
+tally.scores = ['flux', 'fission', 'nu-fission']
+
+# Instantiate a Tallies collection and export to XML
+tallies = openmc.Tallies([tally])
+tallies.export_to_xml()
+
+###############################################################################
+#                   Exporting to OpenMC plots.xml file
+###############################################################################
+
+plot = openmc.Plot()
+plot.origin = [0, 0, 0]
+plot.width = [pitch, pitch, pitch]
+plot.pixels = [1000, 1000, 1]
+plot.type = 'voxel'
+
+# Instantiate a Plots collection and export to XML
+plots = openmc.Plots([plot])
+plots.export_to_xml()

include/openmc/boundary_condition.h

@@ -10,6 +10,7 @@ namespace openmc {
 
 // Forward declare some types used in function arguments.
 class Particle;
+class RandomRay;
 class Surface;
 
 //==============================================================================

include/openmc/cell.h

@@ -249,6 +249,42 @@ class Cell {
   std::unordered_map<int32_t, vector<int32_t>> get_contained_cells(
     int32_t instance = 0, Position* hint = nullptr) const;
 
+  //! Determine the material index corresponding to a specific cell instance,
+  //! taking into account presence of distribcell material
+  //! \param[in] instance of the cell
+  //! \return material index
+  int32_t material(int32_t instance) const
+  {
+    // If distributed materials are used, then each instance has its own
+    // material definition. If distributed materials are not used, then
+    // all instances used the same material stored at material_[0]. The
+    // presence of distributed materials is inferred from the size of
+    // the material_ vector being greater than one.
+    if (material_.size() > 1) {
+      return material_[instance];
+    } else {
+      return material_[0];
+    }
+  }
+
+  //! Determine the temperature index corresponding to a specific cell instance,
+  //! taking into account presence of distribcell temperature
+  //! \param[in] instance of the cell
+  //! \return temperature index
+  double sqrtkT(int32_t instance) const
+  {
+    // If distributed materials are used, then each instance has its own
+    // temperature definition. If distributed materials are not used, then
+    // all instances used the same temperature stored at sqrtkT_[0]. The
+    // presence of distributed materials is inferred from the size of
+    // the sqrtkT_ vector being greater than one.
+    if (sqrtkT_.size() > 1) {
+      return sqrtkT_[instance];
+    } else {
+      return sqrtkT_[0];
+    }
+  }
+
 protected:
   //! Determine the path to this cell instance in the geometry hierarchy
   //! \param[in] instance of the cell to find parent cells for

include/openmc/constants.h

@@ -340,6 +340,8 @@ enum class RunMode {
   VOLUME
 };
 
+enum class SolverType { MONTE_CARLO, RANDOM_RAY };
+
 //==============================================================================
 // Geometry Constants
 

include/openmc/mgxs.h

@@ -29,7 +29,6 @@ class Mgxs {
   int num_delayed_groups; // number of delayed neutron groups
   vector<XsData> xs;      // Cross section data
   // MGXS Incoming Flux Angular grid information
-  bool is_isotropic; // used to skip search for angle indices if isotropic
   int n_pol;
   int n_azi;
   vector<double> polar;
@@ -85,6 +84,8 @@ class Mgxs {
   std::string name; // name of dataset, e.g., UO2
   double awr;       // atomic weight ratio
   bool fissionable; // Is this fissionable
+  bool is_isotropic {
+    true}; // used to skip search for angle indices if isotropic
 
   Mgxs() = default;
 

include/openmc/output.h

@@ -57,6 +57,8 @@ void print_results();
 
 void write_tallies();
 
+void show_time(const char* label, double secs, int indent_level = 0);
+
 } // namespace openmc
 #endif // OPENMC_OUTPUT_H
 
@@ -80,4 +82,4 @@ struct formatter<std::array<T, 2>> {
   }
 };
 
-} // namespace fmt
+} // namespace fmt

include/openmc/plot.h

@@ -100,6 +100,7 @@ class PlottableInterface {
   virtual void print_info() const = 0;
 
   const std::string& path_plot() const { return path_plot_; }
+  std::string& path_plot() { return path_plot_; }
   int id() const { return id_; }
   int level() const { return level_; }