Volume not specified for depletable material with ID=2

Hi, thanks for the reply. I’m new to this so was simply trying to do the hexagonal tutorial.

"%matplotlib inline
import openmc
import math

uel = openmc.Material(name=‘fuel’)
fuel.add_nuclide(‘U235’,1.0)
fuel.set_density(‘g/cm3’,100.0)

fuel2 = openmc.Material(name = ‘fuel2’)
fuel2.add_nuclide(‘U238’,1.0)
fuel2.set_density(‘g/cm3’,100.0)

water = openmc.Material(name=‘water’)
water.add_nuclide(‘H1’,2.0)
water.add_nuclide(‘O16’,10.0)
water.set_density(‘g/cm3’,10.0)

fuel.volume = 1 # ← units are cm³
fuel2.volume = 1 # ← units are cm³

mats = openmc.Materials((fuel,fuel2,water))
mats.export_to_xml()

r_pin = openmc.ZCylinder(r=0.25)
fuel_cell = openmc.Cell(fill=fuel, region = -r_pin)
water_cell = openmc.Cell(fill=water, region = +r_pin)
pin_universe = openmc.Universe(cells=(fuel_cell,water_cell))

r_big_pin = openmc.ZCylinder(r=0.5)
fuel2_cell = openmc.Cell(fill=fuel2, region = -r_big_pin)
water2_cell = openmc.Cell(fill=water,region=+r_big_pin)
big_pin_universe = openmc.Universe(cells=(fuel2_cell,water2_cell))

all_water_cell = openmc.Cell(fill=water)
outer_universe = openmc.Universe(cells=(all_water_cell,))

lat = openmc.HexLattice()

lat.center = (0.,0.)
lat.pitch = (1.25,)
lat.outer = outer_universe

uter_ring = [big_pin_universe] + [pin_universe]*11
middle_ring = [big_pin_universe] + [pin_universe]*5
inner_ring = [big_pin_universe]
lat.universes = [outer_ring,middle_ring,inner_ring]

outer_surface = openmc.ZCylinder(r=4.0,boundary_type=‘vacuum’)
main_cell = openmc.Cell(fill=lat,region=-outer_surface)
geom = openmc.Geometry([main_cell])
geom.export_to_xml()

settings = openmc.Settings()
settings.particles = 100
settings.inactive = 10
settings.batches = 20
settings.export_to_xml()
import openmc.deplete
chain = openmc.deplete.Chain.from_xml("./chain_endfb71_sfr.xml")
operator = openmc.deplete.Operator(geom,settings,"./chain_endfb71_sfr.xml")
power = 174
time_steps = [30 * 24 * 60 * 60] * 6
integrator = openmc.deplete.PredictorIntegrator(operator, time_steps, power)
integrator.integrate() "