Some parametric neutronics tests randomly failing in GA

PRs #766 and #767 both experience what seems to be randomly failing tests.
See : https://github.com/ukaea/paramak/pull/766/checks?check_run_id=2048177525
This is the error message.
=================================== FAILURES ===================================
______ TestNeutronicsBallReactor.test_reactor_from_shapes_2d_mesh_tallies ______

self = <tests.test_parametric_neutronics.test_NeutronicModel.TestNeutronicsBallReactor testMethod=test_reactor_from_shapes_2d_mesh_tallies>

    def test_reactor_from_shapes_2d_mesh_tallies(self):
        """Makes a reactor from two shapes, then mades a neutronics model
        and tests the TBR simulation value"""

        os.system('rm *_on_2D_mesh_*.png')

        test_shape = paramak.RotateStraightShape(
            points=[(0, 0), (0, 20), (20, 20)],
            material_tag='mat1',
        )
        test_shape2 = paramak.RotateSplineShape(
            points=[(100, 100), (100, -100), (200, -100), (200, 100)],
            material_tag='blanket_mat',
            rotation_angle=180
        )

        test_reactor = paramak.Reactor([test_shape, test_shape2])

        neutronics_model = paramak.NeutronicsModel(
            geometry=test_reactor,
            source=self.source,
            materials={
                'mat1': 'copper',
                'blanket_mat': 'FLiNaK',  # used as O18 is not in nndc nuc data
            },
            mesh_tally_2d=['(n,Xt)', 'heating', 'flux'],
            simulation_batches=2,
            simulation_particles_per_batch=10,
        )

        # starts the neutronics simulation using trelis
>       neutronics_model.simulate(verbose=False, method='pymoab')

tests/test_parametric_neutronics/test_NeutronicModel.py:699: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
paramak/parametric_neutronics/neutronics_model.py:629: in simulate
    self.statepoint_filename = self.model.run(
opt/openmc/openmc/model/model.py:228: in run
    openmc.run(**kwargs)
opt/openmc/openmc/executor.py:218: in run
    _run(args, output, cwd)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

args = ['openmc'], output = False, cwd = '.'

    def _run(args, output, cwd):
        # Launch a subprocess
        p = subprocess.Popen(args, cwd=cwd, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT, universal_newlines=True)

        # Capture and re-print OpenMC output in real-time
        lines = []
        while True:
            # If OpenMC is finished, break loop
            line = p.stdout.readline()
            if not line and p.poll() is not None:
                break

            lines.append(line)
            if output:
                # If user requested output, print to screen
                print(line, end='')

        # Raise an exception if return status is non-zero
        if p.returncode != 0:
>           raise subprocess.CalledProcessError(p.returncode, ' '.join(args),
                                                ''.join(lines))
E           subprocess.CalledProcessError: Command 'openmc' died with <Signals.SIGSEGV: 11>.

opt/openmc/openmc/executor.py:28: CalledProcessError
----------------------------- Captured stdout call -----------------------------
Saved file as  RotateStraightShape.stl
Saved file as  RotateSplineShape.stl
Saved file as  Graveyard.stl
----------------------------- Captured stderr call -----------------------------
rm: cannot remove 'dagmc_not_watertight.h5m': No such file or directory
rm: cannot remove 'geometry.xml': No such file or directory
_______ TestNeutronicsBallReactor.test_reactor_from_shapes_cell_tallies ________

self = <tests.test_parametric_neutronics.test_NeutronicModel.TestNeutronicsBallReactor testMethod=test_reactor_from_shapes_cell_tallies>

    def test_reactor_from_shapes_cell_tallies(self):
        """Makes a reactor from two shapes, then mades a neutronics model
        and tests the TBR simulation value"""

        test_shape = paramak.RotateStraightShape(
            points=[(0, 0), (0, 20), (20, 20)],
            material_tag='mat1',
        )
        test_shape2 = paramak.RotateSplineShape(
            points=[(100, 100), (100, -100), (200, -100), (200, 100)],
            material_tag='blanket_mat',
            rotation_angle=180
        )

        test_reactor = paramak.Reactor([test_shape, test_shape2])

        neutronics_model = paramak.NeutronicsModel(
            geometry=test_reactor,
            source=self.source,
            materials={
                'mat1': 'copper',
                'blanket_mat': 'FLiNaK',  # used as O18 is not in nndc nuc data
            },
            cell_tallies=['TBR', 'heating', 'flux'],
            simulation_batches=2,
            simulation_particles_per_batch=10,
        )

        # starts the neutronics simulation using trelis
>       neutronics_model.simulate(verbose=False, method='pymoab')

tests/test_parametric_neutronics/test_NeutronicModel.py:666: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
paramak/parametric_neutronics/neutronics_model.py:629: in simulate
    self.statepoint_filename = self.model.run(
opt/openmc/openmc/model/model.py:228: in run
    openmc.run(**kwargs)
opt/openmc/openmc/executor.py:218: in run
    _run(args, output, cwd)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

args = ['openmc'], output = False, cwd = '.'

    def _run(args, output, cwd):
        # Launch a subprocess
        p = subprocess.Popen(args, cwd=cwd, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT, universal_newlines=True)

        # Capture and re-print OpenMC output in real-time
        lines = []
        while True:
            # If OpenMC is finished, break loop
            line = p.stdout.readline()
            if not line and p.poll() is not None:
                break

            lines.append(line)
            if output:
                # If user requested output, print to screen
                print(line, end='')

        # Raise an exception if return status is non-zero
        if p.returncode != 0:
>           raise subprocess.CalledProcessError(p.returncode, ' '.join(args),
                                                ''.join(lines))
E           subprocess.CalledProcessError: Command 'openmc' died with <Signals.SIGSEGV: 11>.

opt/openmc/openmc/executor.py:28: CalledProcessError
----------------------------- Captured stdout call -----------------------------
Saved file as  RotateStraightShape.stl
Saved file as  RotateSplineShape.stl
Saved file as  Graveyard.stl
----------------------------- Captured stderr call -----------------------------
rm: cannot remove 'dagmc_not_watertight.h5m': No such file or directory
rm: cannot remove 'statepoint.2.h5': No such file or directory
rm: cannot remove 'geometry.xml': No such file or directory
=============================== warnings summary ===============================
ukaea / paramak

Some parametric neutronics tests randomly failing in GA #768
