From 064426a05fdac019917d613eb2805fb80f5fb5ad Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Tue, 2 Aug 2022 13:17:33 +0100
Subject: [PATCH 01/17] added specific_activity

---
 openmc/material.py                | 25 +++++++++++++++++++++++++
 tests/unit_tests/test_material.py | 18 ++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/openmc/material.py b/openmc/material.py
index 6c26416801..61015f5b05 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -94,6 +94,9 @@ class Material(IDManagerMixin):
     activity : float
         Activity of the material in [Bq]. Requires that the :attr:`volume`
         attribute is set.
+    specific_activity : float
+        Activity of the material per unit mass in [Bq/kg]. Requires that the
+        :attr:`volume` and :attr:`density` attributes are set.
 
     """
 
@@ -155,6 +158,11 @@ class Material(IDManagerMixin):
         """Returns the total activity of the material in Becquerels."""
         return sum(self.get_nuclide_activity().values())
 
+    @property
+    def specific_activity(self):
+        """Returns the total specific activity of the material in Becquerels per gram."""
+        return sum(self.get_nuclide_specific_activity().values())
+
     @property
     def name(self):
         return self._name
@@ -925,6 +933,23 @@ class Material(IDManagerMixin):
             activity[nuclide] = inv_seconds * atoms
         return activity
 
+    def get_nuclide_specific_activity(self):
+        """Return specific activity in [Bq/g] for each nuclide in the material
+
+        .. versionadded:: 0.13.1
+
+        Returns
+        -------
+        dict
+            Dictionary whose keys are nuclide names and values are specific
+            activity in [Bq/g].
+        """
+        activity = {}
+        for nuclide, atoms in self.get_nuclide_atoms().items():
+            inv_seconds = openmc.data.decay_constant(nuclide)
+            activity[nuclide] = (inv_seconds * atoms) / self.get_mass()
+        return activity
+
     def get_nuclide_atoms(self):
         """Return number of atoms of each nuclide in the material
 
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 2c5cc2874c..d70161f485 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -496,3 +496,21 @@ def test_activity_of_metastable():
     m1.set_density('g/cm3', 1)
     m1.volume = 98.9
     assert pytest.approx(m1.activity, rel=0.001) == 1.93e19
+
+
+def test_specific_activity_of_tritium():
+    """Checks that specific activity stays the same for all volumes and
+    densities while activity changes proportionally to mass"""
+    m1 = openmc.Material()
+    m1.add_nuclide("H3", 1)
+    m1.set_density('g/cm3', 1)
+    m1.volume = 1
+    # activity and specific_activity are initially the same as we have 1g
+    assert pytest.approx(m1.specific_activity) == 3.559778e14
+    assert pytest.approx(m1.activity) == 3.559778e14
+    m1.set_density('g/cm3', 2)
+    assert pytest.approx(m1.specific_activity) == 3.559778e14
+    assert pytest.approx(m1.activity) == 3.559778e14*2
+    m1.volume = 3
+    assert pytest.approx(m1.specific_activity) == 3.559778e14
+    assert pytest.approx(m1.activity) == 3.559778e14*2*3

From 98c287b83a692beac38eb1617f3f7315a6fa8a20 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Tue, 2 Aug 2022 17:24:48 +0100
Subject: [PATCH 02/17] volume not needed when finding specific activity

---
 openmc/material.py                |  4 ++--
 tests/unit_tests/test_material.py | 21 ++++++++-------------
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 61015f5b05..57f9a6f862 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -945,9 +945,9 @@ class Material(IDManagerMixin):
             activity in [Bq/g].
         """
         activity = {}
-        for nuclide, atoms in self.get_nuclide_atoms().items():
+        for nuclide, atoms in self.get_nuclide_atom_densities().items():
             inv_seconds = openmc.data.decay_constant(nuclide)
-            activity[nuclide] = (inv_seconds * atoms) / self.get_mass()
+            activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.density
         return activity
 
     def get_nuclide_atoms(self):
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index d70161f485..c959ba2762 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -481,12 +481,16 @@ def test_activity_of_stable():
 
 
 def test_activity_of_tritium():
-    """Checks that 1g of tritium has the correct activity"""
+    """Checks that 1g of tritium has the correct activity activity scaling"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)
     m1.volume = 1
     assert pytest.approx(m1.activity) == 3.559778e14
+    m1.set_density('g/cm3', 2)
+    assert pytest.approx(m1.activity) == 3.559778e14*2
+    m1.volume = 3
+    assert pytest.approx(m1.activity) == 3.559778e14*2*3
 
 
 def test_activity_of_metastable():
@@ -499,18 +503,9 @@ def test_activity_of_metastable():
 
 
 def test_specific_activity_of_tritium():
-    """Checks that specific activity stays the same for all volumes and
-    densities while activity changes proportionally to mass"""
+    """Checks that specific activity of tritium is correct"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)
-    m1.volume = 1
-    # activity and specific_activity are initially the same as we have 1g
-    assert pytest.approx(m1.specific_activity) == 3.559778e14
-    assert pytest.approx(m1.activity) == 3.559778e14
-    m1.set_density('g/cm3', 2)
-    assert pytest.approx(m1.specific_activity) == 3.559778e14
-    assert pytest.approx(m1.activity) == 3.559778e14*2
-    m1.volume = 3
-    assert pytest.approx(m1.specific_activity) == 3.559778e14
-    assert pytest.approx(m1.activity) == 3.559778e14*2*3
+    assert m1.specific_activity == 355978108155965.9
+    assert m1.get_nuclide_specific_activity() == {"H3": 355978108155965.9}
\ No newline at end of file

From 742311fd1bb37b884a633d3464f56504448a6ef5 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Tue, 2 Aug 2022 17:37:17 +0100
Subject: [PATCH 03/17] [skip ci] fixed typo

---
 tests/unit_tests/test_material.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index c959ba2762..fd9f325f2e 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -481,7 +481,7 @@ def test_activity_of_stable():
 
 
 def test_activity_of_tritium():
-    """Checks that 1g of tritium has the correct activity activity scaling"""
+    """Checks that 1g of tritium has the correct activity scaling"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)

From 98c707ea07736578a7f4080f2bbbbcab3df3b7a6 Mon Sep 17 00:00:00 2001
From: shimwell <mail@jshimwell.com>
Date: Wed, 3 Aug 2022 22:46:50 +0100
Subject: [PATCH 04/17] refactor activities to single method

---
 openmc/material.py                | 87 ++++++++++++++++---------------
 tests/unit_tests/test_material.py | 25 ++++++---
 2 files changed, 61 insertions(+), 51 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 57f9a6f862..05b69287d2 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -91,13 +91,6 @@ class Material(IDManagerMixin):
     fissionable_mass : float
         Mass of fissionable nuclides in the material in [g]. Requires that the
         :attr:`volume` attribute is set.
-    activity : float
-        Activity of the material in [Bq]. Requires that the :attr:`volume`
-        attribute is set.
-    specific_activity : float
-        Activity of the material per unit mass in [Bq/kg]. Requires that the
-        :attr:`volume` and :attr:`density` attributes are set.
-
     """
 
     next_id = 1
@@ -153,16 +146,6 @@ class Material(IDManagerMixin):
 
         return string
 
-    @property
-    def activity(self):
-        """Returns the total activity of the material in Becquerels."""
-        return sum(self.get_nuclide_activity().values())
-
-    @property
-    def specific_activity(self):
-        """Returns the total specific activity of the material in Becquerels per gram."""
-        return sum(self.get_nuclide_specific_activity().values())
-
     @property
     def name(self):
         return self._name
@@ -916,39 +899,57 @@ class Material(IDManagerMixin):
 
         return nuclides
 
-    def get_nuclide_activity(self):
-        """Return activity in [Bq] for each nuclide in the material
+    def get_activity(self, normalization: str = 'total', by_nuclide: bool = False):
+        """Returns the activity of the material or for each nuclide in the
+        material in units of [Bq], [Bq/g] or [Bq/cc].
 
         .. versionadded:: 0.13.1
 
-        Returns
-        -------
-        dict
-            Dictionary whose keys are nuclide names and values are activity in
-            [Bq].
-        """
-        activity = {}
-        for nuclide, atoms in self.get_nuclide_atoms().items():
-            inv_seconds = openmc.data.decay_constant(nuclide)
-            activity[nuclide] = inv_seconds * atoms
-        return activity
-
-    def get_nuclide_specific_activity(self):
-        """Return specific activity in [Bq/g] for each nuclide in the material
-
-        .. versionadded:: 0.13.1
+        Parameters
+        ----------
+        normalization : {'total', 'mass', 'volume'}
+            Specifies the type of activity to return, 'total' will return the
+            material activity in [Bq], 'mass' returns the materials specific
+            activity in [Bq/g] and 'volume' returns the activity in [Bq/cc].
+        by_nuclide : bool
+            Specifies if the activity should be returned for the material as a
+            whole or per nuclide.
 
         Returns
         -------
-        dict
-            Dictionary whose keys are nuclide names and values are specific
-            activity in [Bq/g].
+
+        Union[dict, float]
+            If by_nuclide is True then a dictionary whose keys are nuclide 
+            names and values are activity is returned. Otherwise the activity
+            of the material is returned as a float.
         """
-        activity = {}
-        for nuclide, atoms in self.get_nuclide_atom_densities().items():
-            inv_seconds = openmc.data.decay_constant(nuclide)
-            activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.density
-        return activity
+
+        cv.check_value('normalization', normalization, {'total', 'mass', 'volume'})
+        cv.check_type('by_nuclide', by_nuclide, bool)
+        
+        if normalization=='total':
+            activity = {}
+            for nuclide, atoms in self.get_nuclide_atoms().items():
+                inv_seconds = openmc.data.decay_constant(nuclide)
+                activity[nuclide] = inv_seconds * atoms
+
+        elif normalization=='mass':
+            activity = {}
+            for nuclide, atoms in self.get_nuclide_atom_densities().items():
+                inv_seconds = openmc.data.decay_constant(nuclide)
+                activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.density
+        # normalization must be volume by this stage so else can be used
+        else:
+            activity = {}
+            for nuclide, atoms in self.get_nuclide_atom_densities().items():
+                inv_seconds = openmc.data.decay_constant(nuclide)
+                activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.volume
+
+        if by_nuclide:
+            return activity
+        else:
+            return sum(activity.values())
+
 
     def get_nuclide_atoms(self):
         """Return number of atoms of each nuclide in the material
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index fd9f325f2e..763325ac90 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -477,7 +477,7 @@ def test_activity_of_stable():
     m1.add_element("Fe", 1)
     m1.set_density('g/cm3', 1)
     m1.volume = 1
-    assert m1.activity == 0
+    assert m1.get_activity() == 0
 
 
 def test_activity_of_tritium():
@@ -486,11 +486,11 @@ def test_activity_of_tritium():
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)
     m1.volume = 1
-    assert pytest.approx(m1.activity) == 3.559778e14
+    assert pytest.approx(m1.get_activity()) == 3.559778e14
     m1.set_density('g/cm3', 2)
-    assert pytest.approx(m1.activity) == 3.559778e14*2
+    assert pytest.approx(m1.get_activity()) == 3.559778e14*2
     m1.volume = 3
-    assert pytest.approx(m1.activity) == 3.559778e14*2*3
+    assert pytest.approx(m1.get_activity()) == 3.559778e14*2*3
 
 
 def test_activity_of_metastable():
@@ -499,13 +499,22 @@ def test_activity_of_metastable():
     m1.add_nuclide("Tc99_m1", 1)
     m1.set_density('g/cm3', 1)
     m1.volume = 98.9
-    assert pytest.approx(m1.activity, rel=0.001) == 1.93e19
+    assert pytest.approx(m1.get_activity(), rel=0.001) == 1.93e19
 
 
 def test_specific_activity_of_tritium():
-    """Checks that specific activity of tritium is correct"""
+    """Checks that specific and volumetric activity of tritium are correct"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)
-    assert m1.specific_activity == 355978108155965.9
-    assert m1.get_nuclide_specific_activity() == {"H3": 355978108155965.9}
\ No newline at end of file
+    assert m1.get_activity(normalization='mass') == 355978108155965.9  # [Bq/g]
+    assert m1.get_activity(normalization='mass', by_nuclide=True) == {
+        "H3": 355978108155965.9  # [Bq/g]
+    }
+    # volume is required to calculate total and volumetric activity
+    m1.volume = 10.
+    assert m1.get_activity(normalization='total') == 355978108155965.9*10. # [Bq]
+    assert m1.get_activity(normalization='volume') == 355978108155965.9/10. # [Bq/cc]
+    assert m1.get_activity(normalization='volume', by_nuclide=True) == {
+        "H3": 355978108155965.9/10. # [Bq/cc]
+    }

From c900e4784e68b3ea833e3b60fe80d3cc345f33eb Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Thu, 4 Aug 2022 07:55:35 +0100
Subject: [PATCH 05/17] Corrections to activity calcs

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 openmc/material.py | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 05b69287d2..48684ed67f 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -927,23 +927,15 @@ class Material(IDManagerMixin):
         cv.check_value('normalization', normalization, {'total', 'mass', 'volume'})
         cv.check_type('by_nuclide', by_nuclide, bool)
         
-        if normalization=='total':
-            activity = {}
-            for nuclide, atoms in self.get_nuclide_atoms().items():
-                inv_seconds = openmc.data.decay_constant(nuclide)
-                activity[nuclide] = inv_seconds * atoms
-
-        elif normalization=='mass':
-            activity = {}
-            for nuclide, atoms in self.get_nuclide_atom_densities().items():
-                inv_seconds = openmc.data.decay_constant(nuclide)
-                activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.density
-        # normalization must be volume by this stage so else can be used
+        if normalization == 'total':
+            multiplier = self.volume
         else:
-            activity = {}
-            for nuclide, atoms in self.get_nuclide_atom_densities().items():
-                inv_seconds = openmc.data.decay_constant(nuclide)
-                activity[nuclide] = (inv_seconds * atoms * 1.0e24) / self.volume
+            multiplier = 1 if normalization == 'volume' else 1.0 / self.get_mass_density()
+            
+        activity = {}
+        for nuclide, atoms_per_bcm in self.get_nuclide_atom_densities().items():
+            inv_seconds = openmc.data.decay_constant(nuclide)
+            activity[nuclide] = inv_seconds * 1e24 * atoms_per_bcm * multiplier
 
         if by_nuclide:
             return activity

From e4d54d49a8f92aa5b90bfd2b814b6bcc751c3541 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Thu, 4 Aug 2022 09:39:14 +0100
Subject: [PATCH 06/17] moved volume lower

---
 tests/unit_tests/test_material.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 763325ac90..24887d8a6b 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -507,14 +507,14 @@ def test_specific_activity_of_tritium():
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
     m1.set_density('g/cm3', 1)
-    assert m1.get_activity(normalization='mass') == 355978108155965.9  # [Bq/g]
+    assert m1.get_activity(normalization='mass') == 355978108155966.0  # [Bq/g]
     assert m1.get_activity(normalization='mass', by_nuclide=True) == {
-        "H3": 355978108155965.9  # [Bq/g]
+        "H3": 355978108155966.0  # [Bq/g]
     }
-    # volume is required to calculate total and volumetric activity
-    m1.volume = 10.
-    assert m1.get_activity(normalization='total') == 355978108155965.9*10. # [Bq]
-    assert m1.get_activity(normalization='volume') == 355978108155965.9/10. # [Bq/cc]
+    assert m1.get_activity(normalization='volume') == 355978108155965.94 # [Bq/cc]
     assert m1.get_activity(normalization='volume', by_nuclide=True) == {
-        "H3": 355978108155965.9/10. # [Bq/cc]
+        "H3": 355978108155965.94 # [Bq/cc]
     }
+    # volume is required to calculate total activity
+    m1.volume = 10.
+    assert m1.get_activity(normalization='total') == 3559781081559659.5 # [Bq]

From c036403c984067946542e97cbdbe488687b6b706 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Thu, 4 Aug 2022 14:55:45 +0100
Subject: [PATCH 07/17] simpler if else statement for normalization

Co-authored-by: Patrick Shriwise <pshriwise@gmail.com>
---
 openmc/material.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 48684ed67f..965c9d5c85 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -929,8 +929,10 @@ class Material(IDManagerMixin):
         
         if normalization == 'total':
             multiplier = self.volume
-        else:
-            multiplier = 1 if normalization == 'volume' else 1.0 / self.get_mass_density()
+        elif normalization == 'volume':
+            multiplier = 1
+        elif normalization == 'mass':
+            multiplier = 1.0 / self.get_mass_density()
             
         activity = {}
         for nuclide, atoms_per_bcm in self.get_nuclide_atom_densities().items():

From 8164f309e9d61479fd65759da46c6e8b22715eef Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Thu, 4 Aug 2022 15:37:01 +0100
Subject: [PATCH 08/17] added pre volume attribute tests for stable nuclide

---
 tests/unit_tests/test_material.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 24887d8a6b..ddb1bfcf20 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -471,16 +471,19 @@ def test_mix_materials():
     assert m5.density == pytest.approx(dens5)
 
 
-def test_activity_of_stable():
+def test_get_activity_of_stable_nuclides():
     """Creates a material with stable isotopes to checks the activity is 0"""
     m1 = openmc.Material()
     m1.add_element("Fe", 1)
-    m1.set_density('g/cm3', 1)
+    m1.set_density('g/cm3', 1.5)
+    # activity in Bq/cc and Bq/g should not require volume setting
+    assert m1.get_activity(normalization='volume') == 0
+    assert m1.get_activity(normalization='mass') == 0
     m1.volume = 1
     assert m1.get_activity() == 0
 
 
-def test_activity_of_tritium():
+def test_get_activity_of_tritium():
     """Checks that 1g of tritium has the correct activity scaling"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)
@@ -493,7 +496,7 @@ def test_activity_of_tritium():
     assert pytest.approx(m1.get_activity()) == 3.559778e14*2*3
 
 
-def test_activity_of_metastable():
+def test_get_activity_of_metastable():
     """Checks that 1 mol of a Tc99_m1 nuclides has the correct activity"""
     m1 = openmc.Material()
     m1.add_nuclide("Tc99_m1", 1)
@@ -502,7 +505,7 @@ def test_activity_of_metastable():
     assert pytest.approx(m1.get_activity(), rel=0.001) == 1.93e19
 
 
-def test_specific_activity_of_tritium():
+def test_get_activity_of_tritium_nuclides():
     """Checks that specific and volumetric activity of tritium are correct"""
     m1 = openmc.Material()
     m1.add_nuclide("H3", 1)

From a30f9b88fd79400c8bbc65de3902d3ddce8e838d Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Thu, 4 Aug 2022 15:49:11 +0100
Subject: [PATCH 09/17] combined activity unit tests as suggested @eepeterson

---
 tests/unit_tests/test_material.py | 67 +++++++++++++++----------------
 1 file changed, 32 insertions(+), 35 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index ddb1bfcf20..432cf3a032 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -471,10 +471,13 @@ def test_mix_materials():
     assert m5.density == pytest.approx(dens5)
 
 
-def test_get_activity_of_stable_nuclides():
-    """Creates a material with stable isotopes to checks the activity is 0"""
+def test_get_activity():
+    """Tests the activity of stable, metastable and active materials"""
+
+    # Creates a material with stable isotopes to checks the activity is 0
     m1 = openmc.Material()
-    m1.add_element("Fe", 1)
+    m1.add_element("Fe", 0.7)
+    m1.add_element("Li", 0.3)
     m1.set_density('g/cm3', 1.5)
     # activity in Bq/cc and Bq/g should not require volume setting
     assert m1.get_activity(normalization='volume') == 0
@@ -482,42 +485,36 @@ def test_get_activity_of_stable_nuclides():
     m1.volume = 1
     assert m1.get_activity() == 0
 
+    # Checks that 1g of tritium has the correct activity scaling
+    m2 = openmc.Material()
+    m2.add_nuclide("H3", 1)
+    m2.set_density('g/cm3', 1)
+    m2.volume = 1
+    assert pytest.approx(m2.get_activity()) == 3.559778e14
+    m2.set_density('g/cm3', 2)
+    assert pytest.approx(m2.get_activity()) == 3.559778e14*2
+    m2.volume = 3
+    assert pytest.approx(m2.get_activity()) == 3.559778e14*2*3
 
-def test_get_activity_of_tritium():
-    """Checks that 1g of tritium has the correct activity scaling"""
-    m1 = openmc.Material()
-    m1.add_nuclide("H3", 1)
-    m1.set_density('g/cm3', 1)
-    m1.volume = 1
-    assert pytest.approx(m1.get_activity()) == 3.559778e14
-    m1.set_density('g/cm3', 2)
-    assert pytest.approx(m1.get_activity()) == 3.559778e14*2
-    m1.volume = 3
-    assert pytest.approx(m1.get_activity()) == 3.559778e14*2*3
+    # Checks that 1 mol of a metastable nuclides has the correct activity
+    m3 = openmc.Material()
+    m3.add_nuclide("Tc99_m1", 1)
+    m3.set_density('g/cm3', 1)
+    m3.volume = 98.9
+    assert pytest.approx(m3.get_activity(), rel=0.001) == 1.93e19
 
-
-def test_get_activity_of_metastable():
-    """Checks that 1 mol of a Tc99_m1 nuclides has the correct activity"""
-    m1 = openmc.Material()
-    m1.add_nuclide("Tc99_m1", 1)
-    m1.set_density('g/cm3', 1)
-    m1.volume = 98.9
-    assert pytest.approx(m1.get_activity(), rel=0.001) == 1.93e19
-
-
-def test_get_activity_of_tritium_nuclides():
-    """Checks that specific and volumetric activity of tritium are correct"""
-    m1 = openmc.Material()
-    m1.add_nuclide("H3", 1)
-    m1.set_density('g/cm3', 1)
-    assert m1.get_activity(normalization='mass') == 355978108155966.0  # [Bq/g]
-    assert m1.get_activity(normalization='mass', by_nuclide=True) == {
+    # Checks that specific and volumetric activity of tritium are correct
+    m4 = openmc.Material()
+    m4.add_nuclide("H3", 1)
+    m4.set_density('g/cm3', 1)
+    assert m4.get_activity(normalization='mass') == 355978108155966.0  # [Bq/g]
+    assert m4.get_activity(normalization='mass', by_nuclide=True) == {
         "H3": 355978108155966.0  # [Bq/g]
     }
-    assert m1.get_activity(normalization='volume') == 355978108155965.94 # [Bq/cc]
-    assert m1.get_activity(normalization='volume', by_nuclide=True) == {
+    assert m4.get_activity(normalization='volume') == 355978108155965.94 # [Bq/cc]
+    assert m4.get_activity(normalization='volume', by_nuclide=True) == {
         "H3": 355978108155965.94 # [Bq/cc]
     }
     # volume is required to calculate total activity
-    m1.volume = 10.
-    assert m1.get_activity(normalization='total') == 3559781081559659.5 # [Bq]
+    m4.volume = 10.
+    assert m4.get_activity(normalization='total') == 3559781081559659.5 # [Bq]

From 152a149488ddc9fae4612b828ca49f9cd27cb181 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Thu, 4 Aug 2022 16:15:12 +0100
Subject: [PATCH 10/17] density set to 1.5 to test different activities scaling

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 tests/unit_tests/test_material.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 432cf3a032..5f567304bd 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -474,7 +474,7 @@ def test_mix_materials():
 def test_get_activity():
     """Tests the activity of stable, metastable and active materials"""
 
-    # Creates a material with stable isotopes to checks the activity is 0
+    # Creates a material with stable isotopes to check the activity is 0
     m1 = openmc.Material()
     m1.add_element("Fe", 0.7)
     m1.add_element("Li", 0.3)
@@ -506,15 +506,15 @@ def test_get_activity():
     # Checks that specific and volumetric activity of tritium are correct
     m4 = openmc.Material()
     m4.add_nuclide("H3", 1)
-    m4.set_density('g/cm3', 1)
-    assert m4.get_activity(normalization='mass') == 355978108155966.0  # [Bq/g]
+    m4.set_density('g/cm3', 1.5)
+    assert m4.get_activity(normalization='mass') == 355978108155966.0*2/3  # [Bq/g]
     assert m4.get_activity(normalization='mass', by_nuclide=True) == {
-        "H3": 355978108155966.0  # [Bq/g]
+        "H3": 355978108155966.0*2/3  # [Bq/g]
     }
-    assert m4.get_activity(normalization='volume') == 355978108155965.94 # [Bq/cc]
+    assert m4.get_activity(normalization='volume') == 355978108155965.94*3/2 # [Bq/cc]
     assert m4.get_activity(normalization='volume', by_nuclide=True) == {
-        "H3": 355978108155965.94 # [Bq/cc]
+        "H3": 355978108155965.94*3/2 # [Bq/cc]
     }
     # volume is required to calculate total activity
     m4.volume = 10.
-    assert m4.get_activity(normalization='total') == 3559781081559659.5 # [Bq]
+    assert m4.get_activity(normalization='total') == 355978108155965.94*3/2*10 # [Bq]

From 39eaf9d88752f97ad21170c6b393358f24d4961c Mon Sep 17 00:00:00 2001
From: Ethan Peterson <ethan.peterson@mit.edu>
Date: Thu, 4 Aug 2022 16:50:18 -0400
Subject: [PATCH 11/17] Apply suggestions from code review

Co-authored-by: Jonathan Shimwell <drshimwell@gmail.com>
---
 openmc/material.py                |  2 +-
 tests/unit_tests/test_material.py | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 965c9d5c85..ed1b839771 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -899,7 +899,7 @@ class Material(IDManagerMixin):
 
         return nuclides
 
-    def get_activity(self, normalization: str = 'total', by_nuclide: bool = False):
+    def get_activity(self, normalization: str = 'volume', by_nuclide: bool = False):
         """Returns the activity of the material or for each nuclide in the
         material in units of [Bq], [Bq/g] or [Bq/cc].
 
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 5f567304bd..eadad5006b 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -483,33 +483,33 @@ def test_get_activity():
     assert m1.get_activity(normalization='volume') == 0
     assert m1.get_activity(normalization='mass') == 0
     m1.volume = 1
-    assert m1.get_activity() == 0
+    assert m1.get_activity(normalization='total') == 0
 
     # Checks that 1g of tritium has the correct activity scaling
     m2 = openmc.Material()
     m2.add_nuclide("H3", 1)
     m2.set_density('g/cm3', 1)
     m2.volume = 1
-    assert pytest.approx(m2.get_activity()) == 3.559778e14
+    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14
     m2.set_density('g/cm3', 2)
-    assert pytest.approx(m2.get_activity()) == 3.559778e14*2
+    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14*2
     m2.volume = 3
-    assert pytest.approx(m2.get_activity()) == 3.559778e14*2*3
+    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14*2*3
 
     # Checks that 1 mol of a metastable nuclides has the correct activity
     m3 = openmc.Material()
     m3.add_nuclide("Tc99_m1", 1)
     m3.set_density('g/cm3', 1)
     m3.volume = 98.9
-    assert pytest.approx(m3.get_activity(), rel=0.001) == 1.93e19
+    assert pytest.approx(m3.get_activity(normalization='total'), rel=0.001) == 1.93e19
 
     # Checks that specific and volumetric activity of tritium are correct
     m4 = openmc.Material()
     m4.add_nuclide("H3", 1)
     m4.set_density('g/cm3', 1.5)
-    assert m4.get_activity(normalization='mass') == 355978108155966.0*2/3  # [Bq/g]
+    assert m4.get_activity(normalization='mass') == 355978108155965.94  # [Bq/g]
     assert m4.get_activity(normalization='mass', by_nuclide=True) == {
-        "H3": 355978108155966.0*2/3  # [Bq/g]
+        "H3": 355978108155965.94  # [Bq/g]
     }
     assert m4.get_activity(normalization='volume') == 355978108155965.94*3/2 # [Bq/cc]
     assert m4.get_activity(normalization='volume', by_nuclide=True) == {

From 75d82a7df72dc1a1e40d7983d4537f412fca703f Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Thu, 4 Aug 2022 23:43:42 +0100
Subject: [PATCH 12/17] reverting to pytest.approx

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 tests/unit_tests/test_material.py | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index eadad5006b..dbc67fcc27 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -507,14 +507,11 @@ def test_get_activity():
     m4 = openmc.Material()
     m4.add_nuclide("H3", 1)
     m4.set_density('g/cm3', 1.5)
-    assert m4.get_activity(normalization='mass') == 355978108155965.94  # [Bq/g]
-    assert m4.get_activity(normalization='mass', by_nuclide=True) == {
-        "H3": 355978108155965.94  # [Bq/g]
-    }
-    assert m4.get_activity(normalization='volume') == 355978108155965.94*3/2 # [Bq/cc]
-    assert m4.get_activity(normalization='volume', by_nuclide=True) == {
-        "H3": 355978108155965.94*3/2 # [Bq/cc]
+    assert pytest.approx(m4.get_activity(normalization='mass')) == 355978108155965.94  # [Bq/g]
+    assert pytest.approx(m4.get_activity(normalization='mass', by_nuclide=True)["H3"]) == 355978108155965.94  # [Bq/g]
+    assert pytest.approx(m4.get_activity(normalization='volume')) == 355978108155965.94*3/2 # [Bq/cc]
+    assert pytest.approx(m4.get_activity(normalization='volume', by_nuclide=True)["H3"]) == 355978108155965.94*3/2 # [Bq/cc]
     }
     # volume is required to calculate total activity
     m4.volume = 10.
-    assert m4.get_activity(normalization='total') == 355978108155965.94*3/2*10 # [Bq]
+    assert pytest.approx(m4.get_activity(normalization='total')) == 355978108155965.94*3/2*10 # [Bq]

From 496dda717ce055024993053d9a42af47a961c955 Mon Sep 17 00:00:00 2001
From: shimwell <mail@jshimwell.com>
Date: Thu, 4 Aug 2022 23:59:51 +0100
Subject: [PATCH 13/17] removed missing bracket

---
 tests/unit_tests/test_material.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index dbc67fcc27..7e91216081 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -511,7 +511,6 @@ def test_get_activity():
     assert pytest.approx(m4.get_activity(normalization='mass', by_nuclide=True)["H3"]) == 355978108155965.94  # [Bq/g]
     assert pytest.approx(m4.get_activity(normalization='volume')) == 355978108155965.94*3/2 # [Bq/cc]
     assert pytest.approx(m4.get_activity(normalization='volume', by_nuclide=True)["H3"]) == 355978108155965.94*3/2 # [Bq/cc]
-    }
     # volume is required to calculate total activity
     m4.volume = 10.
     assert pytest.approx(m4.get_activity(normalization='total')) == 355978108155965.94*3/2*10 # [Bq]

From a94fb43418e15fccf522c2ee1f1271e268c5cba9 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Mon, 8 Aug 2022 14:00:25 +0100
Subject: [PATCH 14/17] review comments from @paulromano

---
 openmc/material.py | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index ed1b839771..c194a8229c 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -899,18 +899,17 @@ class Material(IDManagerMixin):
 
         return nuclides
 
-    def get_activity(self, normalization: str = 'volume', by_nuclide: bool = False):
+    def get_activity(self, units: str = 'Bq/cm3', by_nuclide: bool = False):
         """Returns the activity of the material or for each nuclide in the
-        material in units of [Bq], [Bq/g] or [Bq/cc].
+        material in units of [Bq], [Bq/g] or [Bq/cm3].
 
         .. versionadded:: 0.13.1
 
         Parameters
         ----------
-        normalization : {'total', 'mass', 'volume'}
-            Specifies the type of activity to return, 'total' will return the
-            material activity in [Bq], 'mass' returns the materials specific
-            activity in [Bq/g] and 'volume' returns the activity in [Bq/cc].
+        units : {'Bq', 'Bq/g', 'Bq/cm3'}
+            Specifies the type of activity to return, options include total
+            activity [Bq], specific [Bq/g] or volumetric activity [Bq/cm3].
         by_nuclide : bool
             Specifies if the activity should be returned for the material as a
             whole or per nuclide.
@@ -924,16 +923,16 @@ class Material(IDManagerMixin):
             of the material is returned as a float.
         """
 
-        cv.check_value('normalization', normalization, {'total', 'mass', 'volume'})
+        cv.check_value('units', units, {'Bq', 'Bq/g', 'Bq/cm3'})
         cv.check_type('by_nuclide', by_nuclide, bool)
-        
-        if normalization == 'total':
+
+        if units == 'Bq':
             multiplier = self.volume
-        elif normalization == 'volume':
+        elif units == 'Bq/g':
             multiplier = 1
-        elif normalization == 'mass':
+        elif units == 'Bq/cm3':
             multiplier = 1.0 / self.get_mass_density()
-            
+
         activity = {}
         for nuclide, atoms_per_bcm in self.get_nuclide_atom_densities().items():
             inv_seconds = openmc.data.decay_constant(nuclide)
@@ -944,7 +943,6 @@ class Material(IDManagerMixin):
         else:
             return sum(activity.values())
 
-
     def get_nuclide_atoms(self):
         """Return number of atoms of each nuclide in the material
 

From 63b517aebc775fc4c060c18868895960c95100ae Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Mon, 8 Aug 2022 14:52:35 +0100
Subject: [PATCH 15/17] updated tests to use units args by @eepeterson

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 openmc/material.py                |  3 ++-
 tests/unit_tests/test_material.py | 24 ++++++++++++------------
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index c194a8229c..724b88ab47 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -910,9 +910,10 @@ class Material(IDManagerMixin):
         units : {'Bq', 'Bq/g', 'Bq/cm3'}
             Specifies the type of activity to return, options include total
             activity [Bq], specific [Bq/g] or volumetric activity [Bq/cm3].
+            Default is volumetric activity [Bq/cm3].
         by_nuclide : bool
             Specifies if the activity should be returned for the material as a
-            whole or per nuclide.
+            whole or per nuclide. Default is False.
 
         Returns
         -------
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 7e91216081..451c5308a4 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -480,37 +480,37 @@ def test_get_activity():
     m1.add_element("Li", 0.3)
     m1.set_density('g/cm3', 1.5)
     # activity in Bq/cc and Bq/g should not require volume setting
-    assert m1.get_activity(normalization='volume') == 0
-    assert m1.get_activity(normalization='mass') == 0
+    assert m1.get_activity(units='Bq/cm3') == 0
+    assert m1.get_activity(units='Bq/g') == 0
     m1.volume = 1
-    assert m1.get_activity(normalization='total') == 0
+    assert m1.get_activity(units='Bq') == 0
 
     # Checks that 1g of tritium has the correct activity scaling
     m2 = openmc.Material()
     m2.add_nuclide("H3", 1)
     m2.set_density('g/cm3', 1)
     m2.volume = 1
-    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14
+    assert pytest.approx(m2.get_activity(units='Bq')) == 3.559778e14
     m2.set_density('g/cm3', 2)
-    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14*2
+    assert pytest.approx(m2.get_activity(units='Bq')) == 3.559778e14*2
     m2.volume = 3
-    assert pytest.approx(m2.get_activity(normalization='total')) == 3.559778e14*2*3
+    assert pytest.approx(m2.get_activity(units='Bq')) == 3.559778e14*2*3
 
     # Checks that 1 mol of a metastable nuclides has the correct activity
     m3 = openmc.Material()
     m3.add_nuclide("Tc99_m1", 1)
     m3.set_density('g/cm3', 1)
     m3.volume = 98.9
-    assert pytest.approx(m3.get_activity(normalization='total'), rel=0.001) == 1.93e19
+    assert pytest.approx(m3.get_activity(units='Bq'), rel=0.001) == 1.93e19
 
     # Checks that specific and volumetric activity of tritium are correct
     m4 = openmc.Material()
     m4.add_nuclide("H3", 1)
     m4.set_density('g/cm3', 1.5)
-    assert pytest.approx(m4.get_activity(normalization='mass')) == 355978108155965.94  # [Bq/g]
-    assert pytest.approx(m4.get_activity(normalization='mass', by_nuclide=True)["H3"]) == 355978108155965.94  # [Bq/g]
-    assert pytest.approx(m4.get_activity(normalization='volume')) == 355978108155965.94*3/2 # [Bq/cc]
-    assert pytest.approx(m4.get_activity(normalization='volume', by_nuclide=True)["H3"]) == 355978108155965.94*3/2 # [Bq/cc]
+    assert pytest.approx(m4.get_activity(units='Bq/g')) == 355978108155965.94  # [Bq/g]
+    assert pytest.approx(m4.get_activity(units='Bq/g', by_nuclide=True)["H3"]) == 355978108155965.94  # [Bq/g]
+    assert pytest.approx(m4.get_activity(units='Bq/cm3')) == 355978108155965.94*3/2 # [Bq/cc]
+    assert pytest.approx(m4.get_activity(units='Bq/cm3', by_nuclide=True)["H3"]) == 355978108155965.94*3/2 # [Bq/cc]
     # volume is required to calculate total activity
     m4.volume = 10.
-    assert pytest.approx(m4.get_activity(normalization='total')) == 355978108155965.94*3/2*10 # [Bq]
+    assert pytest.approx(m4.get_activity(units='Bq')) == 355978108155965.94*3/2*10 # [Bq]

From 3271c08d22d60b21546bbb948cd967a46b2023cd Mon Sep 17 00:00:00 2001
From: Ethan Peterson <ethan.peterson@mit.edu>
Date: Mon, 8 Aug 2022 11:34:10 -0400
Subject: [PATCH 16/17] Apply suggestions from @paulromano code review

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
---
 openmc/material.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index 724b88ab47..c89109bfa6 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -917,7 +917,6 @@ class Material(IDManagerMixin):
 
         Returns
         -------
-
         Union[dict, float]
             If by_nuclide is True then a dictionary whose keys are nuclide 
             names and values are activity is returned. Otherwise the activity
@@ -939,10 +938,7 @@ class Material(IDManagerMixin):
             inv_seconds = openmc.data.decay_constant(nuclide)
             activity[nuclide] = inv_seconds * 1e24 * atoms_per_bcm * multiplier
 
-        if by_nuclide:
-            return activity
-        else:
-            return sum(activity.values())
+        return activity if by_nuclide else sum(activity.values())
 
     def get_nuclide_atoms(self):
         """Return number of atoms of each nuclide in the material

From 5d5bc53a15ea3e77744285564d4aac26f0c0c731 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Mon, 8 Aug 2022 20:46:57 +0100
Subject: [PATCH 17/17] Fixing the activity tests @eepeterson

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 openmc/material.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index c89109bfa6..54ff0b5129 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -928,9 +928,9 @@ class Material(IDManagerMixin):
 
         if units == 'Bq':
             multiplier = self.volume
-        elif units == 'Bq/g':
-            multiplier = 1
         elif units == 'Bq/cm3':
+            multiplier = 1
+        elif units == 'Bq/g':
             multiplier = 1.0 / self.get_mass_density()
 
         activity = {}