def METHOD_NAME():
    openmc.reset_auto_ids()
    mat = openmc.Material()
    mat.add_nuclide('Zr90', 1.0)
    mat.set_density('g/cm3', 1.0)
    model = openmc.Model()
    sph = openmc.Sphere(r=25.0, boundary_type='vacuum')
    cell = openmc.Cell(fill=mat, region=-sph)
    model.geometry = openmc.Geometry([cell])
    model.settings.run_mode = 'fixed source'
    model.settings.batches = 2
    model.settings.particles = 50
    return model