OpenMC/tests/unit_tests/test_deplete_microxs.py
Marco De Pietri e5348d3f62
Avoid divide-by-zero in from_multigroup_flux when flux is zero (#3624)
Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
2025-11-12 10:35:07 +00:00

126 lines
3.9 KiB
Python

"""Basic unit tests for openmc.deplete.IndependentOperator instantiation
Modifies and resets environment variable OPENMC_CROSS_SECTIONS
to a custom file with new depletion_chain node
"""
from os import remove
from pathlib import Path
import pytest
from openmc.deplete import MicroXS
import numpy as np
ONE_GROUP_XS = Path(__file__).parents[1] / "micro_xs_simple.csv"
def test_from_array():
nuclides = [
'U234',
'U235',
'U238',
'U236',
'O16',
'O17',
'I135',
'Xe135',
'Xe136',
'Cs135',
'Gd157',
'Gd156']
reactions = ['fission', '(n,gamma)']
# These values are placeholders and are not at all
# physically meaningful.
data = np.array([[0.1, 0.],
[0.1, 0.],
[0.9, 0.],
[0.4, 0.],
[0., 0.],
[0., 0.],
[0., 0.1],
[0., 0.9],
[0., 0.],
[0., 0.],
[0., 0.1],
[0., 0.1]])
data.shape = (12, 2, 1)
MicroXS(data, nuclides, reactions)
with pytest.raises(ValueError, match='Data array must be 3D'):
MicroXS(data[:, 0], nuclides, reactions)
def test_csv():
ref_xs = MicroXS.from_csv(ONE_GROUP_XS)
ref_xs.to_csv('temp_xs.csv')
temp_xs = MicroXS.from_csv('temp_xs.csv')
assert np.all(ref_xs.data == temp_xs.data)
remove('temp_xs.csv')
def test_from_multigroup_flux():
energies = [0., 6.25e-1, 5.53e3, 8.21e5, 2.e7]
flux = [1.1e-7, 1.2e-6, 1.3e-5, 1.4e-4]
chain_file = Path(__file__).parents[1] / 'chain_simple.xml'
kwargs = {'multigroup_flux': flux, 'chain_file': chain_file}
# test with energy group structure from string
microxs = MicroXS.from_multigroup_flux(energies='CASMO-4', **kwargs)
assert isinstance(microxs, MicroXS)
# test with energy group structure as floats
microxs = MicroXS.from_multigroup_flux(energies=energies, **kwargs)
assert isinstance(microxs, MicroXS)
# test with nuclides provided
microxs = MicroXS.from_multigroup_flux(
energies=energies, nuclides=['Gd157', 'H1'], **kwargs
)
assert isinstance(microxs, MicroXS)
assert microxs.nuclides == ['Gd157', 'H1']
# test with reactions provided
microxs = MicroXS.from_multigroup_flux(
energies=energies, reactions=['fission', '(n,2n)'], **kwargs
)
assert isinstance(microxs, MicroXS)
assert microxs.reactions == ['fission', '(n,2n)']
def test_multigroup_flux_same():
chain_file = Path(__file__).parents[1] / 'chain_simple.xml'
# Generate micro XS based on 4-group flux
energies = [0., 6.25e-1, 5.53e3, 8.21e5, 2.e7]
flux_per_ev = [0.3, 0.3, 1.0, 1.0]
flux = flux_per_ev * np.diff(energies)
flux_sum = flux.sum()
microxs_4g = MicroXS.from_multigroup_flux(
energies=energies, multigroup_flux=flux, chain_file=chain_file)
# from_multigroup_flux should not modify the flux
assert flux.sum() == flux_sum
# Generate micro XS based on 2-group flux, where the boundaries line up with
# the 4 group flux and have the same flux per eV across the full energy
# range
energies = [0., 5.53e3, 2.0e7]
flux_per_ev = [0.3, 1.0]
flux = flux_per_ev * np.diff(energies)
microxs_2g = MicroXS.from_multigroup_flux(
energies=energies, multigroup_flux=flux, chain_file=chain_file)
assert microxs_4g.data == pytest.approx(microxs_2g.data)
def test_microxs_zero_flux():
chain_file = Path(__file__).parents[1] / 'chain_simple.xml'
# Generate micro XS based on zero flux
energies = [0., 6.25e-1, 5.53e3, 8.21e5, 2.e7]
flux = [0.0, 0.0, 0.0, 0.0]
microxs = MicroXS.from_multigroup_flux(
energies=energies, multigroup_flux=flux, chain_file=chain_file)
# All microscopic cross sections should be zero
assert np.all(microxs.data == 0.0)