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Enable fission heating tallies in the random ray solver #3714

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2e8b700
Add kappa-fission to the list of required random ray MGXS.
nuclearkevin Jan 8, 2026
3e070e5
Support kappa-fission tallying in the random ray solver.
nuclearkevin Jan 8, 2026
3deab36
Add a test for scoring kappa-fission for the random ray solver.
nuclearkevin Jan 8, 2026
e176f1c
Make the generation of fission heating cross sections optional.
nuclearkevin Jan 8, 2026
ec6064e
Minor documentation changes.
nuclearkevin Jan 8, 2026
c68122a
Error message.
nuclearkevin Jan 8, 2026
4f51b33
Trigger tests
nuclearkevin Jan 9, 2026
57e1019
Make kappa-fission mandatory again.
nuclearkevin Jan 13, 2026
82e7cf1
Add the multiplication by density to kappa-fission.
nuclearkevin Jan 14, 2026
9965437
Merge branch 'develop' into rr_kappa_fission
GuySten Jan 17, 2026
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1 change: 1 addition & 0 deletions docs/source/usersguide/random_ray.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -513,6 +513,7 @@ Supported scores:
- total
- fission
- nu-fission
- kappa-fission
- events

Supported Estimators:
Expand Down
1 change: 1 addition & 0 deletions include/openmc/random_ray/flat_source_domain.h
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Expand Up @@ -107,6 +107,7 @@ class FlatSourceDomain {
vector<double> nu_sigma_f_;
vector<double> sigma_f_;
vector<double> chi_;
vector<double> kappa_fission_;

// 3D arrays stored in 1D representing values for all materials x energy
// groups x energy groups
Expand Down
24 changes: 15 additions & 9 deletions openmc/model/model.py
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Expand Up @@ -1179,8 +1179,8 @@ def plot(

# Convert ID map to RGB image
img = id_map_to_rgb(
id_map=id_map,
color_by=color_by,
id_map=id_map,
color_by=color_by,
colors=colors,
overlap_color=overlap_color
)
Expand Down Expand Up @@ -1217,7 +1217,7 @@ def plot(
extent=(x_min, x_max, y_min, y_max),
**contour_kwargs
)

# If only showing outline, set the axis limits and aspect explicitly
if outline == 'only':
axes.set_xlim(x_min, x_max)
Expand Down Expand Up @@ -1862,12 +1862,14 @@ def _generate_infinite_medium_mgxs(
if correction == 'P0':
mgxs_lib.mgxs_types = [
'nu-transport', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi'
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission'
]
elif correction is None:
mgxs_lib.mgxs_types = [
'total', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi'
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission'
]

# Specify a "cell" domain type for the cross section tally filters
Expand Down Expand Up @@ -2068,10 +2070,12 @@ def _generate_stochastic_slab_mgxs(
# Specify needed cross sections for random ray
if correction == 'P0':
mgxs_lib.mgxs_types = ['nu-transport', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi']
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission']
elif correction is None:
mgxs_lib.mgxs_types = ['total', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi']
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission']

# Specify a "cell" domain type for the cross section tally filters
mgxs_lib.domain_type = "material"
Expand Down Expand Up @@ -2160,12 +2164,14 @@ def _generate_material_wise_mgxs(
if correction == 'P0':
mgxs_lib.mgxs_types = [
'nu-transport', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi'
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission'
]
elif correction is None:
mgxs_lib.mgxs_types = [
'total', 'absorption', 'nu-fission', 'fission',
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi'
'consistent nu-scatter matrix', 'multiplicity matrix', 'chi',
'kappa-fission'
]

# Specify a "cell" domain type for the cross section tally filters
Expand Down
14 changes: 12 additions & 2 deletions src/random_ray/flat_source_domain.cpp
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Expand Up @@ -665,10 +665,15 @@ void FlatSourceDomain::random_ray_tally()
score = 1.0;
break;

case SCORE_KAPPA_FISSION:
score = flux * volume * kappa_fission_[material * negroups_ + g] *
density_mult;
break;

default:
fatal_error("Invalid score specified in tallies.xml. Only flux, "
"total, fission, nu-fission, and events are supported in "
"random ray mode.");
"total, fission, nu-fission, kappa-fission, and events "
"are supported in random ray mode.");
break;
}
// Apply score to the appropriate tally bin
Expand Down Expand Up @@ -1165,6 +1170,10 @@ void FlatSourceDomain::flatten_xs()
}
chi_.push_back(chi);

double kappa_fission =
m.get_xs(MgxsType::KAPPA_FISSION, g_out, NULL, NULL, NULL, t, a);
kappa_fission_.push_back(kappa_fission);

for (int g_in = 0; g_in < negroups_; g_in++) {
double sigma_s =
m.get_xs(MgxsType::NU_SCATTER, g_in, &g_out, NULL, NULL, t, a);
Expand All @@ -1180,6 +1189,7 @@ void FlatSourceDomain::flatten_xs()
nu_sigma_f_.push_back(0);
sigma_f_.push_back(0);
chi_.push_back(0);
kappa_fission_.push_back(0);
for (int g_in = 0; g_in < negroups_; g_in++) {
sigma_s_.push_back(0);
}
Expand Down
5 changes: 3 additions & 2 deletions src/random_ray/random_ray_simulation.cpp
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Expand Up @@ -143,11 +143,12 @@ void validate_random_ray_inputs()
case SCORE_FISSION:
case SCORE_NU_FISSION:
case SCORE_EVENTS:
case SCORE_KAPPA_FISSION:
break;
default:
fatal_error(
"Invalid score specified. Only flux, total, fission, nu-fission, and "
"event scores are supported in random ray mode.");
"Invalid score specified. Only flux, total, fission, nu-fission, "
"kappa-fission, and event scores are supported in random ray mode.");
}
}

Expand Down
Empty file added tests/regression_tests/random_ray_auto_convert_kappa_fission/__init__.py
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Empty file.
73 changes: 73 additions & 0 deletions tests/regression_tests/random_ray_auto_convert_kappa_fission/infinite_medium/inputs_true.dat
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@@ -0,0 +1,73 @@
<?xml version='1.0' encoding='utf-8'?>
<model>
<materials>
<cross_sections>mgxs.h5</cross_sections>
<material id="1" name="UO2__2_4__" depletable="true">
<density value="1.0" units="macro"/>
<macroscopic name="UO2__2_4__"/>
</material>
<material id="2" name="Zircaloy">
<density value="1.0" units="macro"/>
<macroscopic name="Zircaloy"/>
</material>
<material id="3" name="Hot_borated_water">
<density value="1.0" units="macro"/>
<macroscopic name="Hot_borated_water"/>
</material>
</materials>
<geometry>
<cell id="1" name="Fuel" material="1" region="-1" universe="0"/>
<cell id="2" name="Cladding" material="2" region="1 -2" universe="0"/>
<cell id="3" name="Water" material="3" region="2 3 -4 5 -6" universe="0"/>
<surface id="1" name="Fuel OR" type="z-cylinder" coeffs="0 0 0.39218"/>
<surface id="2" name="Clad OR" type="z-cylinder" coeffs="0 0 0.4572"/>
<surface id="3" name="left" type="x-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="4" name="right" type="x-plane" boundary="reflective" coeffs="0.63"/>
<surface id="5" name="bottom" type="y-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="6" name="top" type="y-plane" boundary="reflective" coeffs="0.63"/>
</geometry>
<settings>
<run_mode>eigenvalue</run_mode>
<particles>100</particles>
<batches>10</batches>
<inactive>5</inactive>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1 0.63 0.63 1</parameters>
</space>
<constraints>
<fissionable>true</fissionable>
</constraints>
</source>
<energy_mode>multi-group</energy_mode>
<random_ray>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1.0 0.63 0.63 1.0</parameters>
</space>
</source>
<distance_inactive>30.0</distance_inactive>
<distance_active>150.0</distance_active>
<source_region_meshes>
<mesh id="1">
<domain id="0" type="universe"/>
</mesh>
</source_region_meshes>
<source_shape>linear</source_shape>
</random_ray>
<mesh id="1">
<dimension>2 2</dimension>
<lower_left>-0.63 -0.63</lower_left>
<upper_right>0.63 0.63</upper_right>
</mesh>
</settings>
<tallies>
<filter id="61" type="material">
<bins>1</bins>
</filter>
<tally id="193" name="KF Tally">
<filters>61</filters>
<scores>kappa-fission</scores>
</tally>
</tallies>
</model>
5 changes: 5 additions & 0 deletions ...s/regression_tests/random_ray_auto_convert_kappa_fission/infinite_medium/results_true.dat
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@@ -0,0 +1,5 @@
k-combined:
7.479770E-01 1.624548E-02
tally 1:
2.965503E+08
1.762157E+16
73 changes: 73 additions & 0 deletions tests/regression_tests/random_ray_auto_convert_kappa_fission/material_wise/inputs_true.dat
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@@ -0,0 +1,73 @@
<?xml version='1.0' encoding='utf-8'?>
<model>
<materials>
<cross_sections>mgxs.h5</cross_sections>
<material id="1" name="UO2__2_4__" depletable="true">
<density value="1.0" units="macro"/>
<macroscopic name="UO2__2_4__"/>
</material>
<material id="2" name="Zircaloy">
<density value="1.0" units="macro"/>
<macroscopic name="Zircaloy"/>
</material>
<material id="3" name="Hot_borated_water">
<density value="1.0" units="macro"/>
<macroscopic name="Hot_borated_water"/>
</material>
</materials>
<geometry>
<cell id="1" name="Fuel" material="1" region="-1" universe="0"/>
<cell id="2" name="Cladding" material="2" region="1 -2" universe="0"/>
<cell id="3" name="Water" material="3" region="2 3 -4 5 -6" universe="0"/>
<surface id="1" name="Fuel OR" type="z-cylinder" coeffs="0 0 0.39218"/>
<surface id="2" name="Clad OR" type="z-cylinder" coeffs="0 0 0.4572"/>
<surface id="3" name="left" type="x-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="4" name="right" type="x-plane" boundary="reflective" coeffs="0.63"/>
<surface id="5" name="bottom" type="y-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="6" name="top" type="y-plane" boundary="reflective" coeffs="0.63"/>
</geometry>
<settings>
<run_mode>eigenvalue</run_mode>
<particles>100</particles>
<batches>10</batches>
<inactive>5</inactive>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1 0.63 0.63 1</parameters>
</space>
<constraints>
<fissionable>true</fissionable>
</constraints>
</source>
<energy_mode>multi-group</energy_mode>
<random_ray>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1.0 0.63 0.63 1.0</parameters>
</space>
</source>
<distance_inactive>30.0</distance_inactive>
<distance_active>150.0</distance_active>
<source_region_meshes>
<mesh id="1">
<domain id="0" type="universe"/>
</mesh>
</source_region_meshes>
<source_shape>linear</source_shape>
</random_ray>
<mesh id="1">
<dimension>2 2</dimension>
<lower_left>-0.63 -0.63</lower_left>
<upper_right>0.63 0.63</upper_right>
</mesh>
</settings>
<tallies>
<filter id="97" type="material">
<bins>1</bins>
</filter>
<tally id="203" name="KF Tally">
<filters>97</filters>
<scores>kappa-fission</scores>
</tally>
</tallies>
</model>
5 changes: 5 additions & 0 deletions tests/regression_tests/random_ray_auto_convert_kappa_fission/material_wise/results_true.dat
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k-combined:
7.372542E-01 6.967831E-03
tally 1:
2.909255E+08
1.693395E+16
73 changes: 73 additions & 0 deletions tests/regression_tests/random_ray_auto_convert_kappa_fission/stochastic_slab/inputs_true.dat
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<?xml version='1.0' encoding='utf-8'?>
<model>
<materials>
<cross_sections>mgxs.h5</cross_sections>
<material id="1" name="UO2__2_4__" depletable="true">
<density value="1.0" units="macro"/>
<macroscopic name="UO2__2_4__"/>
</material>
<material id="2" name="Zircaloy">
<density value="1.0" units="macro"/>
<macroscopic name="Zircaloy"/>
</material>
<material id="3" name="Hot_borated_water">
<density value="1.0" units="macro"/>
<macroscopic name="Hot_borated_water"/>
</material>
</materials>
<geometry>
<cell id="1" name="Fuel" material="1" region="-1" universe="0"/>
<cell id="2" name="Cladding" material="2" region="1 -2" universe="0"/>
<cell id="3" name="Water" material="3" region="2 3 -4 5 -6" universe="0"/>
<surface id="1" name="Fuel OR" type="z-cylinder" coeffs="0 0 0.39218"/>
<surface id="2" name="Clad OR" type="z-cylinder" coeffs="0 0 0.4572"/>
<surface id="3" name="left" type="x-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="4" name="right" type="x-plane" boundary="reflective" coeffs="0.63"/>
<surface id="5" name="bottom" type="y-plane" boundary="reflective" coeffs="-0.63"/>
<surface id="6" name="top" type="y-plane" boundary="reflective" coeffs="0.63"/>
</geometry>
<settings>
<run_mode>eigenvalue</run_mode>
<particles>100</particles>
<batches>10</batches>
<inactive>5</inactive>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1 0.63 0.63 1</parameters>
</space>
<constraints>
<fissionable>true</fissionable>
</constraints>
</source>
<energy_mode>multi-group</energy_mode>
<random_ray>
<source type="independent" strength="1.0" particle="neutron">
<space type="box">
<parameters>-0.63 -0.63 -1.0 0.63 0.63 1.0</parameters>
</space>
</source>
<distance_inactive>30.0</distance_inactive>
<distance_active>150.0</distance_active>
<source_region_meshes>
<mesh id="1">
<domain id="0" type="universe"/>
</mesh>
</source_region_meshes>
<source_shape>linear</source_shape>
</random_ray>
<mesh id="1">
<dimension>2 2</dimension>
<lower_left>-0.63 -0.63</lower_left>
<upper_right>0.63 0.63</upper_right>
</mesh>
</settings>
<tallies>
<filter id="97" type="material">
<bins>1</bins>
</filter>
<tally id="203" name="KF Tally">
<filters>97</filters>
<scores>kappa-fission</scores>
</tally>
</tallies>
</model>
5 changes: 5 additions & 0 deletions ...s/regression_tests/random_ray_auto_convert_kappa_fission/stochastic_slab/results_true.dat
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k-combined:
6.413334E-01 2.083132E-02
tally 1:
2.541463E+08
1.297259E+16
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