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Update correlation used for U weight fractions based on enrichment

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This commit is contained in:
Paul Romano 2017-10-04 14:15:13 -05:00
parent 62d4f725b0
commit a41a4d1feb
2 changed files with 18 additions and 4 deletions
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14
openmc/element.py
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@ -124,6 +124,15 @@ class Element(object):
is a tuple consisting of an openmc.Nuclide instance and the natural
abundance of the isotope.
Notes
-----
When the `enrichment` argument is specified, a correlation from
`ORNL/CSD/TM-244 <https://doi.org/10.2172/5561567>`_ is used to
calculate the weight fractions of U234, U235, U236, and U238. Namely,
the weight fraction of U234 and U236 are taken to be 0.89% and 0.46%,
respectively, of the U235 weight fraction. The remainder of the isotopic
weight is assigned to U238.
"""
# Get the nuclides present in nature
@ -217,9 +226,10 @@ class Element(object):
if enrichment is not None:
# Calculate the mass fractions of isotopes
abundances['U234'] = 0.008 * enrichment
abundances['U234'] = 0.0089 * enrichment
abundances['U235'] = enrichment
abundances['U238'] = 100.0 - 1.008 * enrichment
abundances['U236'] = 0.0046 * enrichment
abundances['U238'] = 100.0 - 1.0135 * enrichment
# Convert the mass fractions to mole fractions
for nuclide in abundances.keys():

8
tests/test_enrichment/test_enrichment.py
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@ -21,7 +21,7 @@ if __name__ == '__main__':
sum_densities = 0.
for nuc in densities.keys():
assert nuc in ('U234', 'U235', 'U238')
assert nuc in ('U234', 'U235', 'U236', 'U238')
sum_densities += densities[nuc][1]
# Compute the weight percent U235
@ -30,4 +30,8 @@ if __name__ == '__main__':
# Compute the ratio of U234/U235
u234_to_u235 = densities['U234'][1] / densities['U235'][1]
assert np.isclose(u234_to_u235, 0.008, rtol=1.e-8)
assert np.isclose(u234_to_u235, 0.0089, rtol=1.e-8)
# Compute the ratio of U234/U235
u234_to_u235 = densities['U236'][1] / densities['U235'][1]
assert np.isclose(u234_to_u235, 0.0046, rtol=1.e-8)