@@ -107,6 +107,9 @@ class SharedArray {
   //! \param size The new size of the container
   void resize(int64_t size) { size_ = size; }
 
+  //! Return whether the array is full
+  bool full() const { return size_ == capacity_; }
+
   //! Return the number of elements that the container has currently allocated
   //! space for.
   int64_t capacity() { return capacity_; }
 
@@ -468,7 +468,8 @@ void Particle::cross_surface()
     write_message(1, "    Crossing surface {}", surf->id_);
   }
 
-  if (surf->surf_source_ && simulation::current_batch == settings::n_batches) {
+  if (surf->surf_source_ && simulation::current_batch > settings::n_inactive &&
+      !simulation::surf_source_bank.full()) {
     SourceSite site;
     site.r = r();
     site.u = u();
 
@@ -7,6 +7,7 @@
 import openmc
 
 from tests.testing_harness import PyAPITestHarness
+from tests.regression_tests import config
 
 
 @pytest.fixture
@@ -118,10 +119,14 @@ def _cleanup(self):
 
 @pytest.mark.surf_source_op('write')
 def test_surface_source_write(model):
+    # Test result is based on 1 MPI process
+    np = config['mpi_np']
+    config['mpi_np'] = '1'
     harness = SurfaceSourceTestHarness('statepoint.10.h5',
                                        model,
                                        'inputs_true_write.dat')
     harness.main()
+    config['mpi_np'] = np
 
 
 @pytest.mark.surf_source_op('read')
Original file line number	Diff line number	Diff line change
`@@ -468,7 +468,8 @@ void Particle::cross_surface()`
`468`	`468`	`write_message(1, " Crossing surface {}", surf->id_);`
`469`	`469`	`}`
`470`	`470`
`471`		`- if (surf->surf_source_ && simulation::current_batch == settings::n_batches) {`
	`471`	`+ if (surf->surf_source_ && simulation::current_batch > settings::n_inactive &&`
	`472`	`+ !simulation::surf_source_bank.full()) {`
`472`	`473`	`SourceSite site;`
`473`	`474`	`site.r = r();`
`474`	`475`	`site.u = u();`