Refactor neutronics pka generators to include averaged number densiti…

…es as input. Add documentation (idaholab#302)

doc/content/bib/magpie.bib

@@ -0,0 +1,8 @@
+
+@inproceedings{SchunertTREATHeatSource,
+ author={S. Schunert and others},
+ title={{Heat Source Characterization In A TREAT Fuel Particle Using Coupled Neutronics Binary Collision Monte-Carlo Calculations}},
+ booktitle={{M\&C 2017 International Conference on Mathematics \& Computational Methods Applied to Nuclear Science \& Engineering}},
+ month={April,
+ year={2017}
+}

doc/content/documentation/systems/UserObjects/PKAFissionFragmentNeutronics.md

@@ -1,19 +1,31 @@
-<!-- MOOSE Documentation Stub: Remove this when content is added. -->
-
 # PKAFissionFragmentNeutronics
 
-!alert construction title=Undocumented Class
-The PKAFissionFragmentNeutronics has not been documented, if you would like to contribute to MOOSE by
-writing documentation, please see [/generate.md]. The content contained on this page explains
-the typical documentation associated with a MooseObject; however, what is contained is ultimately
-determined by what is necessary to make the documentation clear for users.
-
-!syntax description /UserObjects/PKAFissionFragmentNeutronics
+`PKAFissionFragmentNeutronics` generates primary knock-on atoms (PKA) originating
+from fission reactions. The difference to PKAFissionFragmentEmpirical is that
+it uses isotopic fission rates computed by neutronics calculations and ENDF data
+for sampling fission product species.
 
-!syntax parameters /UserObjects/PKAFissionFragmentNeutronics
+The partial fission rate for isotope $$i$$ is denoted by $$F_i(\vec{r}, \vec{rho})$$.
+It is computed by:
+$$$ F_i(\vec{r}, \vec{rho}) = \sum\limits_{g=1}^G N_i(\vec{r},\vec{rho})\sigma_{f,g,i} \phi_g(\vec{r}),$$$
+where $$\vec{r}$$ is the location in the macroscopic, neutronics domain and $$\vec{\rho}$$
+is the location in the microscopic domain. These two locations are separated because their
+scale is significantly separated by 3-4 orders of magnitude. Changes with $$\vec{r}$$ are
+understood to be smooth changes of the average composition of the microscopic domain (orders of centimeters), while changes with $$\vec{\rho}$$ captures compositional changes between grains on the microscopic domain, i.e. on the orders of micro-meters. The notation of separating the spatial dependence into two scales follows homogenization theory. $$N_i$$ is the number density of isotope $$i$$, $$\sigma_{f,g,i}$$ is the microscopic fission cross section of isotope $$i$$ in group $$g$$, and $$\phi_g$$ is the scalar flux in group $$g$$.
 
-!syntax inputs /UserObjects/PKAFissionFragmentNeutronics
+Denoting the microscopic domain as $$\Omega_m$$ located at $$\vec{r}_m$$, we can define a slowly varying average of the number densities:
+$$$ N_i(\vec{r}) = \frac{1}{\Omega_m} \int_{\Omega_m} N_i(\vec{r},\vec{rho}) d\vec{\rho}. $$$
+$$N_i(\vec{r})$$ is the number density provided to neutronics calculations. The nuclide fission rates computed by the neutronics calculation is consequently the slowly varying average
+given by:
+$$$ F_i (\vec{r}) = \sum\limits_{g=1}^G N_i(\vec{r})\sigma_{f,g,i}.$$$
+The `PKAFissionFragmentNeutronics` accepts the values of $F_i (\vec{r}_m)$ as the `partial_reaction_rates` parameter. In addition, it accepts the values of $$N_i(\vec{r}_m)$$
+as the `averaged_number_densities` parameter.
 
-!syntax children /UserObjects/PKAFissionFragmentNeutronics
+The fission rate density at a location in the microscopic domain is computed by:
+$$$ F_i (\vec{r}_m, \vec{\rho}) = \frac{N_i(\vec{r}_m, \vec{\rho})}{N_i(\vec{r}_m)} F_i(\vec{r}_m),  $$$
+where $$ N_i(\vec{r}_m, \vec{\rho}) $$ are the number densities provided by the rasterizer.
 
-!bibtex bibliography
+The expected number of fissions in a mesh element with index $j$ and volume $$V_j$$ is given by:
+$$$ C_i = \Delta t \int_{V_j} F_i (\vec{r}_m, \vec{\rho})  d\vec{\rho}. $$$
+Non-integer results are rounded up with a probability of the $$ C_i - \text{int}(C_i) $$; otherwise
+rounded down. Two PKAs are created from each fission event. The algorithm for sampling their type, energy, and direction of motion is described in [cite:SchunertTREATHeatSource].

doc/hidden.yml

@@ -21,7 +21,6 @@
 - /UserObjects/NeutronicsSpectrumSamplerFission
 - /UserObjects/PKAConstant
 - /UserObjects/PKAFissionFragmentEmpirical
-- /UserObjects/PKAFissionFragmentNeutronics
 - /UserObjects/PKAFixedPointGenerator
 - /UserObjects/PKAFunction
 - /UserObjects/PKAGeneratorAlphaDecay

include/userobjects/PKAFissionFragmentNeutronics.h

@@ -34,17 +34,6 @@ class PKAFissionFragmentNeutronics : public PKAGeneratorNeutronicsBase
    * will be sampled to determine the initial state of the ions passed to MyTRIM
    */
   DiscreteFissionPKAPDF _pdf;
-
-  /**
-   * _partial_fission_rates: the fission rate per nuclide is:
-   * f_i = N_i * (sum_g sigma_{f,g,i} phi_g),
-   * where i is the nuclide ID and g is the energy group.
-   * N_i is provided as variable in the Rasterizer, but the (sum_g sigma_{f,g,i} phi_g) must
-   * be provided as partial fission rate here
-   * Note: the fission rate densities are in units of [ fissions / ( mesh-length-unit^3 sec ) ]
-   */
-  std::vector<const Real *> _partial_fission_rates;
-  std::vector<Real> _stored_pps;
 };
 
 #endif //PKAFISSIONFRAGMENTNEUTRONICS_H

include/userobjects/PKAGeneratorNeutronicsBase.h

@@ -31,6 +31,20 @@ class PKAGeneratorNeutronicsBase : public PKAGeneratorBase
 
   /// helper function to set pdf based on neutronics information from Mammoth
   virtual void setPDF(const std::vector<unsigned int> & ZAID, const std::vector<Real> & energies, const MultiIndex<Real> & probabilities) = 0;
+
+protected:
+  /**
+   * The partial reaction rates are reaction rates of a certain type from the neutronics calculation
+   * for a single nculide, e.g. fission rate of U-235. NOTE: it multiplies the smoothly varying _average_
+   * of the U-235 number density already
+   *
+   * In Magpie, the rate of PKA creation is obtained by multiplying with the _local_ number density. To obtain a
+   * proper PKA creation rate, we need to divide by the smooth average. This is what _averaged_number_densities is for.
+   */
+  std::vector<const Real *> _partial_neutronics_reaction_rates;
+  std::vector<Real> _stored_reaction_rates;
+  std::vector<const Real *> _averaged_number_densities;
+  std::vector<Real> _stored_densities;
 };
 
 #endif // PKAGENERATORNEUTRONICSBASE_H

include/userobjects/PKAGeneratorRecoil.h

@@ -33,13 +33,6 @@ class PKAGeneratorRecoil : public PKAGeneratorNeutronicsBase
    * are sampled
    */
   DiscretePKAPDF _pdf;
-
-  /**
-   * The partial reaction rates [# reactions / time / volume] of the particular
-   * recoil reaction for each nuclide
-   */
-  std::vector<const Real *> _partial_recoil_rates;
-  std::vector<Real> _stored_pps;
 };
 
 #endif //PKAGeneratorRecoil_H

src/userobjects/PKAFissionFragmentNeutronics.C

@@ -17,41 +17,13 @@ template<>
 InputParameters validParams<PKAFissionFragmentNeutronics>()
 {
   InputParameters params = validParams<PKAGeneratorNeutronicsBase>();
-  params.addParam<std::vector<PostprocessorName>>("partial_fission_rates", "Partial fission rates per unit volume [sum_g sigma_{f,g,i} * phi_g]. "
-                                                  "Provide number density as variable in rasterizer!");
   params.addClassDescription("PKA generator (fission) user object.\n Takes pdf and samples PKAs due to fission.");
   return params;
 }
 
 PKAFissionFragmentNeutronics::PKAFissionFragmentNeutronics(const InputParameters & parameters):
     PKAGeneratorNeutronicsBase(parameters)
 {
-  if (isParamValid("partial_fission_rates"))
-  {
-    std::vector<PostprocessorName> names = getParam<std::vector<PostprocessorName>>("partial_fission_rates");
-    _partial_fission_rates.resize(names.size());
-    _stored_pps.resize(names.size());
-    for (unsigned int j = 0; j < names.size(); ++j)
-      if (_fe_problem.hasPostprocessor(names[j]))
-        _partial_fission_rates[j] = &getPostprocessorValueByName(names[j]);
-      else
-      {
-        Real real_value = -std::numeric_limits<Real>::max();
-        std::istringstream ss(names[j]);
-
-        if (ss >> real_value && ss.eof())
-          _stored_pps[j] = real_value;
-        else
-          mooseError("Illegal entry in partial_fission_rates: ", names[j]);
-
-        _partial_fission_rates[j] = &_stored_pps[j];
-      }
-  }
-  else
-  {
-    _stored_pps = {1.0e-8};
-    _partial_fission_rates = {&_stored_pps[0]};
-  }
 }
 
 void
@@ -66,12 +38,14 @@ PKAFissionFragmentNeutronics::appendPKAs(std::vector<MyTRIM_NS::IonBase> & ion_l
   mooseAssert(dt >= 0, "Passed a negative time window into PKAFissionFragmentNeutronics::appendPKAs");
   mooseAssert(vol >= 0, "Passed a negative volume into PKAFissionFragmentNeutronics::appendPKAs");
 
-  if (averaged_data._elements.size() != _partial_fission_rates.size())
-    mooseError("Size of averaged_data and partial_fission_rates must be equal");
+  if (averaged_data._elements.size() != _partial_neutronics_reaction_rates.size())
+    mooseError("Size of averaged_data and partial_reaction_rates must be equal");
 
-  for (unsigned int nuclide = 0; nuclide < _partial_fission_rates.size(); ++nuclide)
+  for (unsigned int nuclide = 0; nuclide < _partial_neutronics_reaction_rates.size(); ++nuclide)
   {
-    unsigned int num_fission = std::floor(recoil_rate_scaling * dt * vol * (*_partial_fission_rates[nuclide]) * averaged_data._elements[nuclide] + getRandomReal());
+    unsigned int num_fission = std::floor(recoil_rate_scaling * dt * vol *
+                              (*_partial_neutronics_reaction_rates[nuclide]) / (*_averaged_number_densities[nuclide])
+                              * averaged_data._elements[nuclide] + getRandomReal());
 
     for (unsigned i = 0; i < num_fission; ++i)
     {

src/userobjects/PKAGeneratorNeutronicsBase.C

@@ -15,11 +15,75 @@ template<>
 InputParameters validParams<PKAGeneratorNeutronicsBase>()
 {
   InputParameters params = validParams<PKAGeneratorBase>();
+  params.addParam<std::vector<PostprocessorName>>("partial_reaction_rates", "Partial neutronic reaction rates per unit volume [sum_g xs_{r,g,i} * phi_g], "
+                                                  "r: reaction type, g: energy group, i: nuclide id.Provide number density as variable in rasterizer!");
+  params.addParam<std::vector<PostprocessorName>>("averaged_number_densities", "The number density of the species averaged over the domain.");
   params.addClassDescription("PKA generator (neutronics) user object base class.\n Takes pdf and samples PKAs due to various interactions.");
   return params;
 }
 
 PKAGeneratorNeutronicsBase::PKAGeneratorNeutronicsBase(const InputParameters & parameters) :
     PKAGeneratorBase(parameters)
 {
+  if (isParamValid("partial_reaction_rates"))
+  {
+    std::vector<PostprocessorName> names = getParam<std::vector<PostprocessorName>>("partial_reaction_rates");
+    _partial_neutronics_reaction_rates.resize(names.size());
+    _stored_reaction_rates.resize(names.size());
+    for (unsigned int j = 0; j < names.size(); ++j)
+      if (_fe_problem.hasPostprocessor(names[j]))
+        _partial_neutronics_reaction_rates[j] = &getPostprocessorValueByName(names[j]);
+      else
+      {
+        Real real_value = -std::numeric_limits<Real>::max();
+        std::istringstream ss(names[j]);
+
+        if (ss >> real_value && ss.eof())
+          _stored_reaction_rates[j] = real_value;
+        else
+          mooseError("Illegal entry in _partial_neutronics_reaction_rates: ", names[j]);
+
+        _partial_neutronics_reaction_rates[j] = &_stored_reaction_rates[j];
+      }
+  }
+  else
+  {
+    _stored_reaction_rates = {1.0e-8};
+    _partial_neutronics_reaction_rates = {&_stored_reaction_rates[0]};
+  }
+
+  if (isParamValid("averaged_number_densities"))
+  {
+    std::vector<PostprocessorName> names = getParam<std::vector<PostprocessorName>>("averaged_number_densities");
+    _averaged_number_densities.resize(names.size());
+    _stored_densities.resize(names.size());
+    for (unsigned int j = 0; j < names.size(); ++j)
+      if (_fe_problem.hasPostprocessor(names[j]))
+        _averaged_number_densities[j] = &getPostprocessorValueByName(names[j]);
+      else
+      {
+        Real real_value = -std::numeric_limits<Real>::max();
+        std::istringstream ss(names[j]);
+
+        if (ss >> real_value && ss.eof())
+          _stored_densities[j] = real_value;
+        else
+          mooseError("Illegal entry in _partial_neutronics_reaction_rates: ", names[j]);
+
+        _averaged_number_densities[j] = &_stored_reaction_rates[j];
+      }
+  }
+  else
+  {
+    _averaged_number_densities.resize(_stored_reaction_rates.size());
+    _stored_densities.resize(_stored_reaction_rates.size());
+    for (unsigned int j = 0; j < _stored_densities.size(); ++j)
+    {
+      _stored_densities[j] = 1;
+      _averaged_number_densities[j] = &_stored_densities[j];
+    }
+  }
+
+  if (_averaged_number_densities.size() != _partial_neutronics_reaction_rates.size())
+    mooseError("partial_reaction_rates and averaged_number_densities must have the same number of entries.");
 }

src/userobjects/PKAGeneratorRecoil.C

@@ -16,41 +16,13 @@ template<>
 InputParameters validParams<PKAGeneratorRecoil>()
 {
   InputParameters params = validParams<PKAGeneratorNeutronicsBase>();
-  params.addParam<std::vector<PostprocessorName>>("partial_recoil_rates", "Partial recoil rates per unit volume [recoil reaction rate per nuclide]. "
-                                                  "Provide number density as variable in rasterizer!");
   params.addClassDescription("PKA recoil generator user object.\n Takes pdf and samples PKAs due to recoil reaction.");
   return params;
 }
 
 PKAGeneratorRecoil::PKAGeneratorRecoil(const InputParameters & parameters):
     PKAGeneratorNeutronicsBase(parameters)
 {
-  if (isParamValid("partial_recoil_rates"))
-  {
-    std::vector<PostprocessorName> names = getParam<std::vector<PostprocessorName>>("partial_recoil_rates");
-    _partial_recoil_rates.resize(names.size());
-    _stored_pps.resize(names.size());
-    for (unsigned int j = 0; j < names.size(); ++j)
-      if (_fe_problem.hasPostprocessor(names[j]))
-        _partial_recoil_rates[j] = &getPostprocessorValueByName(names[j]);
-      else
-      {
-        Real real_value = -std::numeric_limits<Real>::max();
-        std::istringstream ss(names[j]);
-
-        if (ss >> real_value && ss.eof())
-          _stored_pps[j] = real_value;
-        else
-          mooseError("Illegal entry in partial_recoil_rates: ", names[j]);
-
-        _partial_recoil_rates[j] = &_stored_pps[j];
-      }
-  }
-  else
-  {
-    _stored_pps = {1.0e-8};
-    _partial_recoil_rates = {&_stored_pps[0]};
-  }
 }
 
 void
@@ -68,12 +40,14 @@ PKAGeneratorRecoil::appendPKAs(std::vector<MyTRIM_NS::IonBase> & ion_list, Real
   mooseAssert(dt >= 0, "Passed a negative time window into PKAGeneratorRecoil::appendPKAs");
   mooseAssert(vol >= 0, "Passed a negative volume into PKAGeneratorRecoil::appendPKAs");
 
-  if (averaged_data._elements.size() != _partial_recoil_rates.size())
-    mooseError("Size of averaged_data and partial_recoil_rates must be equal");
+  if (averaged_data._elements.size() != _partial_neutronics_reaction_rates.size())
+    mooseError("Size of averaged_data and partial_reaction_rates must be equal");
 
-  for (unsigned int nuclide = 0; nuclide < _partial_recoil_rates.size(); ++nuclide)
+  for (unsigned int nuclide = 0; nuclide < _partial_neutronics_reaction_rates.size(); ++nuclide)
   {
-    unsigned int num_recoils = std::floor(recoil_rate_scaling * dt * vol * (*_partial_recoil_rates[nuclide]) * averaged_data._elements[nuclide] + getRandomReal());
+    unsigned int num_recoils = std::floor(recoil_rate_scaling * dt * vol *
+                               (*_partial_neutronics_reaction_rates[nuclide]) / (*_averaged_number_densities[nuclide])
+                               * averaged_data._elements[nuclide] + getRandomReal());
 
     for (unsigned i = 0; i < num_recoils; ++i)
     {

tests/radiation_damage/coupled_fission_mockup/damage_sub.i

@@ -137,7 +137,7 @@
   [./neutronics_fission_generator]
     type = PKAFissionFragmentNeutronics
     relative_density = 1
-    partial_fission_rates = '2.0e-11 0 0'
+    partial_reaction_rates = '2.0e-11 0 0'
   [../]
   [./rasterizer]
     type = MyTRIMRasterizer

tests/radiation_damage/coupled_fission_mockup/damage_sub_3D.i

@@ -138,7 +138,7 @@
   [./neutronics_fission_generator]
     type = PKAFissionFragmentNeutronics
     relative_density = 1
-    partial_fission_rates = '1.0e-14 0 0'
+    partial_reaction_rates = '1.0e-14 0 0'
   [../]
   [./rasterizer]
     type = MyTRIMRasterizer