From 195dff6d1d22cc8dd5ed840d846073ff22fed550 Mon Sep 17 00:00:00 2001
From: Hridoy Kabiraj <rudrokabiraj@gmail.com>
Date: Mon, 18 May 2026 20:20:59 +0600
Subject: [PATCH 1/2] Fix missing volume checks in material activity/decay heat
 (#3939)

---
 openmc/material.py                | 5 +++++
 tests/unit_tests/test_material.py | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/openmc/material.py b/openmc/material.py
index 2dbe691f52..86cc3d7939 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -1418,6 +1418,9 @@ class Material(IDManagerMixin):
         if volume is None:
             volume = self.volume
 
+        if units in {'Bq', 'Ci'} and volume is None:
+            raise ValueError(f"Volume must be set in order to compute activity in '{units}'.")
+
         if units == 'Bq':
             multiplier = volume
         elif units == 'Bq/cm3':
@@ -1474,6 +1477,8 @@ class Material(IDManagerMixin):
 
         if units == 'W':
             multiplier = volume if volume is not None else self.volume
+            if multiplier is None:
+                raise ValueError("Volume must be set in order to compute total decay heat.")
         elif units == 'W/cm3':
             multiplier = 1
         elif units == 'W/m3':
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 911b8867f9..89dfc03ddd 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -561,6 +561,10 @@ def test_get_activity():
     m1.add_element("Fe", 0.7)
     m1.add_element("Li", 0.3)
     m1.set_density('g/cm3', 1.5)
+    with pytest.raises(ValueError, match="Volume must be set"):
+        m1.get_activity(units='Bq')
+    with pytest.raises(ValueError, match="Volume must be set"):
+        m1.get_activity(units='Ci')
     # activity in Bq/cc and Bq/g should not require volume setting
     assert m1.get_activity(units='Bq/cm3') == 0
     assert m1.get_activity(units='Bq/g') == 0
@@ -619,6 +623,8 @@ def test_get_decay_heat():
     m1.add_nuclide("U235", 0.2)
     m1.add_nuclide("U238", 0.8)
     m1.set_density('g/cm3', 10.5)
+    with pytest.raises(ValueError, match="Volume must be set"):
+        m1.get_decay_heat(units='W')
     # decay heat in W/cc and W/g should not require volume setting
     assert m1.get_decay_heat(units='W/cm3') == 0
     assert m1.get_decay_heat(units='W/g') == 0

From beed56e6ee44037a1543e7ff3cc8815376634c18 Mon Sep 17 00:00:00 2001
From: charliesheh <59520443+charliesheh@users.noreply.github.com>
Date: Mon, 18 May 2026 11:35:56 -0700
Subject: [PATCH 2/2] Check for missing thread count argument for -s/--threads
 (#3940)

---
 src/initialize.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/initialize.cpp b/src/initialize.cpp
index 991877b242..c04a2fcbdd 100644
--- a/src/initialize.cpp
+++ b/src/initialize.cpp
@@ -300,6 +300,11 @@ int parse_command_line(int argc, char* argv[])
         settings::run_mode = RunMode::VOLUME;
       } else if (arg == "-s" || arg == "--threads") {
         // Read number of threads
+        if (i + 1 >= argc) {
+          std::string msg {"Number of threads not specified."};
+          strcpy(openmc_err_msg, msg.c_str());
+          return OPENMC_E_INVALID_ARGUMENT;
+        }
         i += 1;
 
 #ifdef _OPENMP