How to use HexagonalPrism correctly?

Hi, im trying to pack ZCylinder region into a HexagonalPrism, but when i checked the bounding_box of the hexagonal region, x value of its both lower left and upper right goes infinite. Here my HexagonalPrism

# Region hexagonal yang membungkus FC
ll, ur = fc_1_universe.bounding_box
edge1 = ur[0]

hexaregion = openmc.model.HexagonalPrism(edge_length = edge1 + 0.6, orientation = 'x')

outer_region = -hexaregion & +fc_lattice[3] & +fc_lattice_bot & -fc_lattice_top
outer_fc_cell = openmc.Cell(fill=graphite, region = outer_region)

fc_1_cell_universe = openmc.Universe(cells=[fc_helium1, fc_triso_1, fc_graph, fc_helium2, outer_fc_cell])

bounding box of fc_1_universe:

BoundingBox(lower_left=(-2.374, -2.374, 0.0), upper_right=(2.374, 2.374, 3.864000000000002))

and bounding_box of fc_1_cell_universe (the hexagonal one):

BoundingBox(lower_left=(-inf, -2.5755595508549205, 0.0), upper_right=(inf, 2.5755595508549205, 3.864000000000002))

Am i doing it wrong or its just how HexagonalPrism works? Any advice will be very grateful. Also sorry for my bad english