About OpenMC aborted unexpectedly

Hello everyone
I’d like to ask you a few questions.
Firstly, When calculating the burnup, the volume refers to the volume of the entire fuel area or the volume of the entire fuel, then if the calculation object is TRISO particles, is it the entire fuel area ×pf
Secondly, When I used all the threads to compute, I always reported the OpenMC aborted unexpectedly.
WARNING: Could not find material 16 specified in plot 5
WARNING: Could not find material 18 specified in plot 5
These problems, but I think my modeling is OK, the code is below, please help me check, thank you.

from math import pi

import numpy as np

#import openmoc

import openmc

import openmc.model

import openmc.mgxs as mgxs

import openmc.data

import math

fuel = openmc.Material(name=‘Fuel’)

fuel.add_nuclide(‘U235’, 7.11163507e-03)

fuel.add_nuclide(‘U238’, 1.63842133e-02)

fuel.add_nuclide(‘O16’, 4.69916967e-02)

buff = openmc.Material(name=‘Buffer’)

buff.set_density(‘g/cm3’, 1.0)

buff.add_element(‘C’, 1.0)

buff.add_s_alpha_beta(‘c_Graphite’)

PyC1 = openmc.Material(name=‘PyC1’)

PyC1.set_density(‘g/cm3’, 1.9)

PyC1.add_element(‘C’, 1.0)

PyC1.add_s_alpha_beta(‘c_Graphite’)

PyC2 = openmc.Material(name=‘PyC2’)

PyC2.set_density(‘g/cm3’, 1.87)

PyC2.add_element(‘C’, 1.0)

PyC2.add_s_alpha_beta(‘c_Graphite’)

SiC = openmc.Material(name=‘SiC’)

SiC.set_density(‘g/cm3’, 3.2)

SiC.add_element(‘C’, 0.5)

SiC.add_element(‘Si’, 0.5)

graphite = openmc.Material()

graphite.set_density(‘g/cm3’, 1.1995)

graphite.add_element(‘C’, 1.0)

graphite.add_s_alpha_beta(‘c_Graphite’)

Zr = openmc.Material(name=‘Zr’)

Zr.temperature = 300.0

Zr.set_density(‘atom/b-cm’, 1.776679E-02)

Zr.add_nuclide(‘Fe54’, 7.99520E-04)

Zr.add_nuclide(‘Fe56’, 1.22590E-02)

Zr.add_nuclide(‘Fe57’, 2.66510E-04)

Zr.add_nuclide(‘Cr52’, 3.55340E-03)

Zr.add_nuclide(‘Al27’, 8.88360E-04)

Matrix = openmc.Material(name=‘Matrix’)

Matrix.temperature = 300.0

Matrix.set_density(‘atom/b-cm’, 9.55241E-02)

Matrix.add_nuclide(‘C0’, 4.77620E-02)

Matrix.add_nuclide(‘Si28’, 4.40510E-02)

Matrix.add_nuclide(‘Si29’, 2.23050E-03)

Matrix.add_nuclide(‘Si30’, 1.48060E-03)

Water = openmc.Material(name=‘Water’)

Water.temperature = 300.0

Water.set_density(‘atom/b-cm’, 1.00500E-01)

Water.add_nuclide(‘H1’, 2.0)

Water.add_nuclide(‘O16’,1.0)

Water.add_s_alpha_beta(‘c_H_in_H2O’)

Gd2O3=openmc.Material(name=‘Gd2O3’)

Gd2O3.set_density(‘g/cm3’, 8.33)

Gd2O3.add_nuclide(‘Gd152’,0.167639,‘wo’)

Gd2O3.add_nuclide(‘Gd154’,1.851335,‘wo’)

Gd2O3.add_nuclide(‘Gd155’,12.650508,‘wo’)

Gd2O3.add_nuclide(‘Gd156’,17.609904,‘wo’)

Gd2O3.add_nuclide(‘Gd157’,13.550727,‘wo’)

Gd2O3.add_nuclide(‘Gd158’,21.643699,‘wo’)

Gd2O3.add_nuclide(‘Gd160’,19.288733,‘wo’)

Gd2O3.add_nuclide(‘O16’,13.237456,‘wo’)

Create TRISO universe

spheres = [openmc.Sphere(r=1e-4*r)

for r in [215., 315., 350., 385.]]

cells = [openmc.Cell(fill=Gd2O3, region=-spheres[0]),

openmc.Cell(fill=Gd2O3, region=+spheres[0] & -spheres[1]),

openmc.Cell(fill=Gd2O3, region=+spheres[1] & -spheres[2]),

openmc.Cell(fill=Gd2O3, region=+spheres[2] & -spheres[3]),

openmc.Cell(fill=Gd2O3, region=+spheres[3])]

triso_univ = openmc.Universe(cells=cells)

wide_fuel=2

height_fuel=0.36

wide_water=wide_fuel+0.2

height_water=height_fuel+0.2

min_x = openmc.XPlane(x0=-wide_water/2, boundary_type=‘reflective’)

max_x = openmc.XPlane(x0=wide_water/2, boundary_type=‘reflective’)

min_y = openmc.YPlane(y0=-height_water/2, boundary_type=‘reflective’)

max_y = openmc.YPlane(y0=height_water/2, boundary_type=‘reflective’)

min_z = openmc.ZPlane(z0=-0.4, boundary_type=‘reflective’)

max_z = openmc.ZPlane(z0=0.4, boundary_type=‘reflective’)

fuel_or=openmc.model.rectangular_prism(width=wide_fuel,height=height_fuel)

zr_or=openmc.model.rectangular_prism(width=wide_fuel+0.1,height=height_fuel+0.1)

triso_region = fuel_or&(-max_z&+min_z)

zr_cell=openmc.Cell(region=zr_or&~fuel_or&-max_z&+min_z)

water_cell=openmc.Cell(region=~zr_or&(-max_z& +min_z&-max_x&+min_x&+min_y&-max_y))

outer_radius = 425*1e-4

pf=0.1

centers = openmc.model.pack_spheres(radius=outer_radius, region=triso_region, pf=pf)

trisos = [openmc.model.TRISO(outer_radius, triso_univ, center) for center in centers]

triso_fuel_cell = openmc.Cell(region=triso_region)

lower_left, upper_right = triso_fuel_cell.region.bounding_box

shape = (7, 7, 7)

pitch = (upper_right - lower_left)/shape

lattice = openmc.model.create_triso_lattice(

trisos, lower_left, pitch, shape, fuel)

triso_fuel_cell.fill = lattice

zr_cell.fill=Zr

water_cell.fill=Water

univ = openmc.Universe(cells=[zr_cell,water_cell,triso_fuel_cell])

geom = openmc.Geometry(univ)

geom.export_to_xml()

mats = list(geom.get_all_materials().values())

openmc.Materials(mats).export_to_xml()

settings = openmc.Settings()

settings.batches = 500

settings.inactive = 10

settings.particles = 10000

settings.export_to_xml()

openmc.run()