From b7df2d95e16c9eba756bfb1c65dae29d60a939c4 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Tue, 4 Aug 2020 13:05:56 -0500
Subject: [PATCH] Add documentation of collapse_rate functions

---
 include/openmc/nuclide.h  |  6 ++++++
 include/openmc/reaction.h |  9 ++++++++-
 openmc/lib/nuclide.py     | 17 +++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/openmc/nuclide.h b/include/openmc/nuclide.h
index ae4cdda1ef..6af04b14dc 100644
--- a/include/openmc/nuclide.h
+++ b/include/openmc/nuclide.h
@@ -58,6 +58,12 @@ public:
   //! from probability tables.
   void calculate_urr_xs(int i_temp, Particle& p) const;
 
+  //! \brief Calculate reaction rate based on group-wise flux distribution
+  //
+  //! \param[in] MT ENDF MT value for desired reaction
+  //! \param[in] energy Energy group boundaries in [eV]
+  //! \param[in] flux Flux in each energy group (not normalized per eV)
+  //! \return Reaction rate
   double collapse_rate(int MT, gsl::span<const double> energy, gsl::span<const double> flux) const;
 
   // Data members
diff --git a/include/openmc/reaction.h b/include/openmc/reaction.h
index ad1e7702cb..0975c1fd2a 100644
--- a/include/openmc/reaction.h
+++ b/include/openmc/reaction.h
@@ -27,7 +27,14 @@ public:
   //! \param[in] temperatures Desired temperatures for cross sections
   explicit Reaction(hid_t group, const std::vector<int>& temperatures);
 
-  double collapse_rate(gsl::span<const double> energy, gsl::span<const double> flux, const std::vector<double>& grid) const;
+  //! \brief Calculate reaction rate based on group-wise flux distribution
+  //
+  //! \param[in] energy Energy group boundaries in [eV]
+  //! \param[in] flux Flux in each energy group (not normalized per eV)
+  //! \param[in] grid Nuclide energy grid
+  //! \return Reaction rate
+  double collapse_rate(gsl::span<const double> energy, gsl::span<const double> flux,
+    const std::vector<double>& grid) const;
 
   //! Cross section at a single temperature
   struct TemperatureXS {
diff --git a/openmc/lib/nuclide.py b/openmc/lib/nuclide.py
index 0e3ca66eb6..b526cb1636 100644
--- a/openmc/lib/nuclide.py
+++ b/openmc/lib/nuclide.py
@@ -78,6 +78,23 @@ class Nuclide(_FortranObject):
         return name.value.decode()
 
     def collapse_rate(self, MT, energy, flux):
+        """Calculate reaction rate based on group-wise flux distribution
+
+        Parameters
+        ----------
+        MT : int
+            ENDF MT value of the desired reaction
+        energy : iterable of float
+            Energy group boundaries in [eV]
+        flux : iterable of float
+            Flux in each energt group (not normalized per eV)
+
+        Returns
+        -------
+        float
+            Reaction rate
+
+        """
         energy = np.asarray(energy, dtype=float)
         flux = np.asarray(flux, dtype=float)
         xs = c_double()