Add a settings flag to turn off/on delayed photon fission yield scaling

docs/source/io_formats/settings.rst

@@ -96,6 +96,17 @@ When the DAGMC mode is enabled, the OpenMC geometry will be read from the file
 ``dagmc.h5m``. If a :ref:`geometry.xml <io_geometry>` file is present with
 ``dagmc`` set to ``true``, it will be ignored.
 
+----------------------------
+``<delayed_photon_scaling>``
+----------------------------
+
+Determines whether to scale the fission photon yield to account for delayed
+photon energy. The photon yields are scaled as (EGP + EGD)/EGP where EGP and EGD
+are the prompt and delayed photon components of energy release, respectively,
+from MF=1, MT=458 on an ENDF evaluation.
+
+  *Default*: true
+
 --------------------------------
 ``<electron_treatment>`` Element
 --------------------------------

include/openmc/settings.h

@@ -29,6 +29,7 @@ extern bool confidence_intervals;     //!< use confidence intervals for results?
 extern bool create_fission_neutrons;  //!< create fission neutrons (fixed source)?
 extern "C" bool cmfd_run;             //!< is a CMFD run?
 extern "C" bool dagmc;                //!< indicator of DAGMC geometry
+extern bool delayed_photon_scaling;   //!< Scale fission photon yield to include delayed
 extern "C" bool entropy_on;           //!< calculate Shannon entropy?
 extern bool legendre_to_tabular;      //!< convert Legendre distributions to tabular?
 extern bool material_cell_offsets;    //!< create material cells offsets?

openmc/settings.py

@@ -40,6 +40,10 @@ class Settings(object):
         below which particle type will be killed.
     dagmc : bool
         Indicate that a CAD-based DAGMC geometry will be used.
+    delayed_photon_scaling : bool
+        Indicate whether to scale the fission photon yield by (EGP + EGD)/EGP
+        where EGP is the energy release of prompt photons and EGD is the energy
+        release of delayed photons.
     electron_treatment : {'led', 'ttb'}
         Whether to deposit all energy from electrons locally ('led') or create
         secondary bremsstrahlung photons ('ttb').
@@ -219,6 +223,7 @@ class Settings(object):
             VolumeCalculation, 'volume calculations')
 
         self._create_fission_neutrons = None
+        self._delayed_photon_scaling = None
         self._material_cell_offsets = None
         self._log_grid_bins = None
 
@@ -356,6 +361,10 @@ class Settings(object):
     def create_fission_neutrons(self):
         return self._create_fission_neutrons
 
+    @property
+    def delayed_photon_scaling(self):
+        return self._delayed_photon_scaling
+
     @property
     def material_cell_offsets(self):
         return self._material_cell_offsets
@@ -691,6 +700,11 @@ class Settings(object):
                       create_fission_neutrons, bool)
         self._create_fission_neutrons = create_fission_neutrons
 
+    @delayed_photon_scaling.setter
+    def delayed_photon_scaling(self, value):
+        cv.check_type('delayed photon scaling', value, bool)
+        self._delayed_photon_scaling = value
+
     @material_cell_offsets.setter
     def material_cell_offsets(self, value):
         cv.check_type('material cell offsets', value, bool)
@@ -930,6 +944,11 @@ class Settings(object):
             elem = ET.SubElement(root, "create_fission_neutrons")
             elem.text = str(self._create_fission_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")
+            elem.text = str(self._delayed_photon_scaling).lower()
+
     def _create_material_cell_offsets_subelement(self, root):
         if self._material_cell_offsets is not None:
             elem = ET.SubElement(root, "material_cell_offsets")
@@ -1166,6 +1185,11 @@ class Settings(object):
         if text is not None:
             self.create_fission_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:
+            self.delayed_photon_scaling = text in ('true', '1')
+
     def _material_cell_offsets_from_xml_element(self, root):
         text = get_text(root, 'material_cell_offsets')
         if text is not None:
@@ -1225,6 +1249,7 @@ class Settings(object):
         self._create_resonance_scattering_subelement(root_element)
         self._create_volume_calcs_subelement(root_element)
         self._create_create_fission_neutrons_subelement(root_element)
+        self._create_delayed_photon_scaling_subelement(root_element)
         self._create_material_cell_offsets_subelement(root_element)
         self._create_log_grid_bins_subelement(root_element)
         self._create_dagmc_subelement(root_element)
@@ -1291,6 +1316,7 @@ class Settings(object):
         settings._ufs_mesh_from_xml_element(root)
         settings._resonance_scattering_from_xml_element(root)
         settings._create_fission_neutrons_from_xml_element(root)
+        settings._delayed_photon_scaling_from_xml_element(root)
         settings._material_cell_offsets_from_xml_element(root)
         settings._log_grid_bins_from_xml_element(root)
         settings._dagmc_from_xml_element(root)

src/finalize.cpp

@@ -69,6 +69,7 @@ int openmc_finalize()
   settings::check_overlaps = false;
   settings::confidence_intervals = false;
   settings::create_fission_neutrons = true;
+  settings::delayed_photon_scaling = true;
   settings::electron_treatment = ELECTRON_LED;
   settings::energy_cutoff = {0.0, 1000.0, 0.0, 0.0};
   settings::entropy_on = false;

src/nuclide.cpp

@@ -305,11 +305,13 @@ void Nuclide::create_derived(const Function1D* prompt_photons, const Function1D*
             // For fission, artificially increase the photon yield to account
             // for delayed photons
             double f = 1.0;
-            if (is_fission(rx->mt_)) {
-              if (prompt_photons && delayed_photons) {
-                double energy_prompt = (*prompt_photons)(E);
-                double energy_delayed = (*delayed_photons)(E);
-                f = (energy_prompt + energy_delayed)/(energy_prompt);
+            if (settings::delayed_photon_scaling) {
+              if (is_fission(rx->mt_)) {
+                if (prompt_photons && delayed_photons) {
+                  double energy_prompt = (*prompt_photons)(E);
+                  double energy_delayed = (*delayed_photons)(E);
+                  f = (energy_prompt + energy_delayed)/(energy_prompt);
+                }
               }
             }
 

src/relaxng/settings.rnc

@@ -14,6 +14,8 @@ element settings {
     (element energy_positron { xsd:double } | attribute energy_positron { xsd:double })?
   }? &
 
+  element delayed_photon_scaling { xsd:boolean }? &
+
   element electron_treatment { ( "led" | "ttb" ) }? &
 
   element energy_grid { ( "nuclide" | "log" | "logarithm" | "logarithmic" | "material-union" | "union" ) }? &

src/relaxng/settings.rng

@@ -82,6 +82,11 @@
         </interleave>
       </element>
     </optional>
+    <optional>
+      <element name="delayed_photon_scaling">
+        <data type="boolean"/>
+      </element>
+    </optional>
     <optional>
       <element name="electron_treatment">
         <choice>

src/settings.cpp

@@ -44,6 +44,7 @@ bool cmfd_run                {false};
 bool confidence_intervals    {false};
 bool create_fission_neutrons {true};
 bool dagmc                   {false};
+bool delayed_photon_scaling  {true};
 bool entropy_on              {false};
 bool legendre_to_tabular     {true};
 bool material_cell_offsets   {true};
@@ -778,6 +779,11 @@ void read_settings_xml()
     }
   }
 
+  // Check whether to scale fission photon yields
+  if (check_for_node(root, "delayed_photon_scaling")) {
+    delayed_photon_scaling = get_node_value_bool(root, "delayed_photon_scaling");
+  }
+
   // Check whether material cell offsets should be generated
   if (check_for_node(root, "material_cell_offsets")) {
     material_cell_offsets = get_node_value_bool(root, "material_cell_offsets");