Merge pull request #2348 from cfichtlscherer/prompt_neutrons

Prompt neutrons 2.0

docs/source/io_formats/settings.rst

@@ -32,6 +32,17 @@ standard deviation.
 
   *Default*: false
 
+-------------------------------------
+``<create_delayed_neutrons>`` Element
+-------------------------------------
+
+The ``<create_delayed_neutrons>`` element indicates whether delayed neutrons
+are created in fission. If this element is set to "true", delayed neutrons
+will be created in fission events; otherwise only prompt neutrons will be
+created.
+
+  *Default*: true
+
 -------------------------------------
 ``<create_fission_neutrons>`` Element
 -------------------------------------

include/openmc/settings.h

@@ -28,6 +28,7 @@ extern bool check_overlaps;       //!< check overlaps in geometry?
 extern bool confidence_intervals; //!< use confidence intervals for results?
 extern bool
   create_fission_neutrons; //!< create fission neutrons (fixed source)?
+extern bool create_delayed_neutrons; //!< create delayed fission neutrons?
 extern "C" bool cmfd_run;  //!< is a CMFD run?
 extern bool
   delayed_photon_scaling;   //!< Scale fission photon yield to include delayed

openmc/settings.py

@@ -225,6 +225,10 @@ class Settings:
         Weight windows to use for variance reduction
 
         .. versionadded:: 0.13
+    create_delayed_neutrons : bool
+        Whether delayed neutrons are created in fission.
+
+        .. versionadded:: 0.13.3
     weight_windows_on : bool
         Whether weight windows are enabled
 
@@ -296,6 +300,7 @@ class Settings:
             VolumeCalculation, 'volume calculations')
 
         self._create_fission_neutrons = None
+        self._create_delayed_neutrons = None
         self._delayed_photon_scaling = None
         self._material_cell_offsets = None
         self._log_grid_bins = None
@@ -459,6 +464,10 @@ class Settings:
     def create_fission_neutrons(self) -> bool:
         return self._create_fission_neutrons
 
+    @property
+    def create_delayed_neutrons(self) -> bool:
+        return self._create_delayed_neutrons
+
     @property
     def delayed_photon_scaling(self) -> bool:
         return self._delayed_photon_scaling
@@ -866,6 +875,12 @@ class Settings:
                       create_fission_neutrons, bool)
         self._create_fission_neutrons = create_fission_neutrons
 
+    @create_delayed_neutrons.setter
+    def create_delayed_neutrons(self, create_delayed_neutrons: bool):
+        cv.check_type('Whether create only prompt neutrons',
+                      create_delayed_neutrons, bool)
+        self._create_delayed_neutrons = create_delayed_neutrons
+
     @delayed_photon_scaling.setter
     def delayed_photon_scaling(self, value: bool):
         cv.check_type('delayed photon scaling', value, bool)
@@ -1207,6 +1222,11 @@ class Settings:
             elem = ET.SubElement(root, "create_fission_neutrons")
             elem.text = str(self._create_fission_neutrons).lower()
 
+    def _create_create_delayed_neutrons_subelement(self, root):
+       if self._create_delayed_neutrons is not None:
+           elem = ET.SubElement(root, "create_delayed_neutrons")
+           elem.text = str(self._create_delayed_neutrons).lower()
+
     def _create_delayed_photon_scaling_subelement(self, root):
         if self._delayed_photon_scaling is not None:
             elem = ET.SubElement(root, "delayed_photon_scaling")
@@ -1532,6 +1552,11 @@ class Settings:
         if text is not None:
             self.create_fission_neutrons = text in ('true', '1')
 
+    def _create_delayed_neutrons_from_xml_element(self, root):
+        text = get_text(root, 'create_delayed_neutrons')
+        if text is not None:
+            self.create_delayed_neutrons = text in ('true', '1')
+
     def _delayed_photon_scaling_from_xml_element(self, root):
         text = get_text(root, 'delayed_photon_scaling')
         if text is not None:
@@ -1630,6 +1655,7 @@ class Settings:
         self._create_resonance_scattering_subelement(element)
         self._create_volume_calcs_subelement(element)
         self._create_create_fission_neutrons_subelement(element)
+        self._create_create_delayed_neutrons_subelement(element)
         self._create_delayed_photon_scaling_subelement(element)
         self._create_event_based_subelement(element)
         self._create_max_particles_in_flight_subelement(element)
@@ -1722,6 +1748,7 @@ class Settings:
         settings._ufs_mesh_from_xml_element(elem, meshes)
         settings._resonance_scattering_from_xml_element(elem)
         settings._create_fission_neutrons_from_xml_element(elem)
+        settings._create_delayed_neutrons_from_xml_element(elem)
         settings._delayed_photon_scaling_from_xml_element(elem)
         settings._event_based_from_xml_element(elem)
         settings._max_particles_in_flight_from_xml_element(elem)

src/finalize.cpp

@@ -74,6 +74,7 @@ int openmc_finalize()
   settings::check_overlaps = false;
   settings::confidence_intervals = false;
   settings::create_fission_neutrons = true;
+  settings::create_delayed_neutrons = true;
   settings::electron_treatment = ElectronTreatment::LED;
   settings::delayed_photon_scaling = true;
   settings::energy_cutoff = {0.0, 1000.0, 0.0, 0.0};

src/nuclide.cpp

@@ -519,7 +519,7 @@ double Nuclide::nu(double E, EmissionMode mode, int group) const
   case EmissionMode::prompt:
     return (*fission_rx_[0]->products_[0].yield_)(E);
   case EmissionMode::delayed:
-    if (n_precursor_ > 0) {
+    if (n_precursor_ > 0 && settings::create_delayed_neutrons) {
       auto rx = fission_rx_[0];
       if (group >= 1 && group < rx->products_.size()) {
         // If delayed group specified, determine yield immediately
@@ -544,7 +544,7 @@ double Nuclide::nu(double E, EmissionMode mode, int group) const
       return 0.0;
     }
   case EmissionMode::total:
-    if (total_nu_) {
+    if (total_nu_ && settings::create_delayed_neutrons) {
       return (*total_nu_)(E);
     } else {
       return (*fission_rx_[0]->products_[0].yield_)(E);

src/settings.cpp

@@ -44,6 +44,7 @@ bool assume_separate {false};
 bool check_overlaps {false};
 bool cmfd_run {false};
 bool confidence_intervals {false};
+bool create_delayed_neutrons {true};
 bool create_fission_neutrons {true};
 bool delayed_photon_scaling {true};
 bool entropy_on {false};
@@ -873,6 +874,12 @@ void read_settings_xml(pugi::xml_node root)
     }
   }
 
+  // Check whether create delayed neutrons in fission
+  if (check_for_node(root, "create_delayed_neutrons")) {
+    create_delayed_neutrons =
+      get_node_value_bool(root, "create_delayed_neutrons");
+  }
+
   // Check whether create fission sites
   if (run_mode == RunMode::FIXED_SOURCE) {
     if (check_for_node(root, "create_fission_neutrons")) {

tests/unit_tests/test_settings.py

@@ -49,6 +49,7 @@ def test_export_to_xml(run_in_tmpdir):
         domains=[openmc.Cell()], samples=1000, lower_left=(-10., -10., -10.),
         upper_right = (10., 10., 10.))
     s.create_fission_neutrons = True
+    s.create_delayed_neutrons = False
     s.log_grid_bins = 2000
     s.photon_transport = False
     s.electron_treatment = 'led'
@@ -107,6 +108,7 @@ def test_export_to_xml(run_in_tmpdir):
                                       'energy_min': 1.0, 'energy_max': 1000.0,
                                       'nuclides': ['U235', 'U238', 'Pu239']}
     assert s.create_fission_neutrons
+    assert not s.create_delayed_neutrons 
     assert s.log_grid_bins == 2000
     assert not s.photon_transport
     assert s.electron_treatment == 'led'