Lattice within manually defined cells

lattice_ex.py

import openmc

# constants

l = 1.0
h = 1.0

model = openmc.model.Model()

# materials
m_fuel = openmc.Material()
m_fuel.set_density('kg/m3', 10820)

m_fuel.add_nuclide('U234', 0.0020301709666386285, 'ao')
m_fuel.add_nuclide('U235', 0.8413029718075326, 'ao')
m_fuel.add_nuclide('U238', 0.15666685722582877, 'ao')
m_fuel.add_nuclide('O16', 0.4998105, 'ao')

m_graphite_matrix = openmc.Material()
m_graphite_matrix.set_density('kg/m3', 1700)
m_graphite_matrix.add_element('C', 1.0)
m_graphite_matrix.add_s_alpha_beta('c_Graphite')

# infinite fuel and moterator cells
fuel_cell = openmc.Cell(name="Fuel", fill=m_fuel)
fuel_univ = openmc.Universe(cells=[fuel_cell])
mod_cell = openmc.Cell(name="Moderator", fill=m_graphite_matrix)
mod_univ = openmc.Universe(cells=[mod_cell])

# Define planes that will be defined for cells to fill with the universe
min_z = openmc.ZPlane(z0=0.0, boundary_type='reflective')
max_z = openmc.ZPlane(z0=h, boundary_type='reflective')

min_x = openmc.XPlane(x0=-l, boundary_type='reflective')
max_x = openmc.XPlane(x0=l, boundary_type='reflective')

min_y = openmc.YPlane(y0=-l, boundary_type='reflective')
max_y = openmc.YPlane(y0=0, boundary_type='reflective')

# separate into three sections along y
y0 = openmc.YPlane(y0=0)
y1 = openmc.YPlane(y0=-l/3)
y2 = openmc.YPlane(y0=-2*l/3)
y3 = openmc.YPlane(y0=-l)
quadrants = [+y3 & -y2, +y2 & -y1, +y1 & -y0]

# define a regular lattice
reg_lattice = openmc.RectLattice()
reg_lattice.universes = [[[fuel_univ, mod_univ], [mod_univ, fuel_univ]], # k = 0
                         [[mod_univ, fuel_univ], [fuel_univ, mod_univ]]] # k = 1
lattice_region = +min_y & -max_y & +min_x & -max_x & +min_z & -max_z
llc, urc = lattice_region.bounding_box
reg_lattice.lower_left = llc
reg_lattice.pitch = (urc - llc) / reg_lattice.shape
print("Regular lattice shape: {}".format(reg_lattice.shape))

# uncomment and fill cells with lattice_univ to fix
# lattice_cell = openmc.Cell(fill=reg_lattice)
# lattice_univ = openmc.Universe(cells=[lattice_cell])

y_section_0 = openmc.Cell(region=quadrants[0], fill=reg_lattice)
y_section_1 = openmc.Cell(region=quadrants[1], fill=reg_lattice)
y_section_2 = openmc.Cell(region=quadrants[2], fill=reg_lattice)

y_sections = [y_section_0, y_section_1, y_section_2]

inner_univ = openmc.Universe(cells=y_sections)
main_cell = openmc.Cell(region=lattice_region, fill=inner_univ)

model.geometry = openmc.Geometry([main_cell])

# some settings
settings = openmc.Settings()

settings.particles = 1000
settings.inactive = 2
settings.batches = 10
settings.temperature['method'] = 'interpolation'
settings.temperature['multipole'] = True
settings.temperature['range'] = (294.0, 1500.0)
settings.temperature['default'] = 500.0

lower_left = (-l, -l, 0.0)
upper_right = (l, 0, h)
source_dist = openmc.stats.Box(lower_left, upper_right)
source = openmc.Source(space=source_dist)
settings.source = source

model.settings = settings
model.export_to_xml()