PostOMC

A Python package for reading and analyzing OpenMC depletion_results.h5 files.

Installation

PostOMC is available on PyPI:

pip install postomc

This installs the postomc python package as well as the pomc command line script.

API Usage

PostOMC revolves around the DepletionResults class which can be instantiated from a depletion_results.h5 file:

from postomc import DepletionResults
res = DepletionResults("path/to/depletion_results.h5")

To get the isotopic composition over time simply call the DepletionResults like a function, and provide the desired unit as argument:

res("g/cm**3")

If your result file contains only a single medium, this returns a Pandas dataframe with nuclide names as row index and timestamps as columns:

          0.0           1.0           2.0           3.0
H1        0.0  8.546804e-11  1.710615e-10  2.561159e-10
H2        0.0  9.163202e-17  3.674525e-16  8.276545e-16
H3        0.0  7.819664e-26  6.288458e-25  2.128727e-24
H4        0.0  0.000000e+00  0.000000e+00  0.000000e+00
H5        0.0  0.000000e+00  0.000000e+00  0.000000e+00
...       ...           ...           ...           ...
Ds271_m1  0.0  0.000000e+00  0.000000e+00  0.000000e+00
Ds272     0.0  0.000000e+00  0.000000e+00  0.000000e+00
Ds273     0.0  0.000000e+00  0.000000e+00  0.000000e+00
Ds279_m1  0.0  0.000000e+00  0.000000e+00  0.000000e+00
Rg272     0.0  0.000000e+00  0.000000e+00  0.000000e+00

[3820 rows x 4 columns]

If your result file contains multiple media, it will return a dictionary mapping medium id to results dataframes. If you want to look at derived quantities like decay heat or activity, you'll need to provide an OpenMC decay chain to get decay constant and energy release values:

from postomc import DepletionResults
res = DepletionResults("path/to/depletion_results.h5", chain="path/to/chain.xml")
res("W")
res("W/cm**3")
res("Bq")
res("Bq/cm**3")

You can also set the time unit to whatever you prefer:

res("W", time_unit="s")

PostOMC uses pint for unit management so any unit from the default pint definition file is valid as long as it is homogeneous to mass, number of atoms, power, activity, or their volumic counterparts.

We also define the atom unit as an alias for the count unit so you can do:

res("atom/beer_barrel", time_unit="fortnight")

Sometimes you may want to get information like total mass of a certain element, regardless of isotope. You can facilitate this treatment by providing the multiindex=True argument to the call, this will result in dataframes using multiindex.

          0.0           1.0           2.0           3.0
Z  A   I
H  1   0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   2   0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   3   0  0.0  4.284350e-12  3.445411e-11  1.166318e-10
   4   0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   5   0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
...       ...           ...           ...           ...
Ds 271 1  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   272 0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   273 0  0.0  0.000000e+00  0.000000e+00  0.000000e+00
   279 1  0.0  0.000000e+00  0.000000e+00  0.000000e+00
Rg 272 0  0.0  0.000000e+00  0.000000e+00  0.000000e+00

[3820 rows x 4 columns]

In addition to isotopic composition you can retrieve:

• Reaction rates in $\mathrm{reaction}/s$ with DepletionResults.rr(time_unit="s")
• $k_\mathrm{eff}$ using DepletionResults.keffs(time_unit="s")
• Reactivity using DepletionResults.rhos(time_unit="s")

Time units are always "day" by default.

CLI Usage

PostOMC provides some CLI commands to perform common analysis tasks without having to create a python script.

Printing Information

You can print a short summary of a depletion_results.h5 file using the pomc info command:

$ pomc info data/depletion_results.h5
Depletion File       data/depletion_results.h5
Summary File         data/summary.h5

                  Depletion Steps                   
┏━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Step # ┃ t(i) [days] ┃ t(i+1) [days] ┃ Power [W] ┃
┡━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ 1      │ 0.00        │ 30.00         │ 174.00    │
│ 2      │ 30.00       │ 60.00         │ 174.00    │
│ 3      │ 60.00       │ 90.00         │ 174.00    │
│ 4      │ 90.00       │ 120.00        │ 174.00    │
│ 5      │ 120.00      │ 120.00        │ 174.00    │
└────────┴─────────────┴───────────────┴───────────┘
                        Materials                        
┏━━━━┳━━━━━━━━━━━━┳━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Id ┃ Name       ┃ Nuclides ┃ Atom Density [atom/b/cm] ┃
┡━━━━╇━━━━━━━━━━━━╇━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ 1  │ UO2 (2.4%) │ 4        │ 6.88e-02                 │
└────┴────────────┴──────────┴──────────────────────────┘

Exporting data

PostOMC provides the pomc export command to export the depletion result data to Excel, CSV, or to print its content to the terminal:

Usage: pomc export [OPTIONS] FILE

  Converts depletion_result.h5 files to various output formats.

Options:
  -s, --split-nuclides    Whether to create a nuclide indexed table or an
                          (Element, A, I) indexed table.
  -u, --unit TEXT         The desired unit.  [default: g/cm**3]
  -t, --time-unit TEXT    The desired time unit.  [default: d]
  -o, --output TEXT       Path to the output file.
  -c, --chain TEXT        Path to a depletion chain file.
  -m, --material INTEGER  Id of the desired material
  --help                  Show this message and exit.

Examples

To create an Excel file with a tab for each material:

$ pomc export path/to/depletion_results.h5 -o mass.xlsx -u "g/cm**3"

To create a CSV file of decay heat for a single material:

$ pomc export data/depletion_results.h5 -o dh.csv -u "W" -m 1

By default PostOMC finds the required depletion chain using the OPENMC_CHAIN_FILE environment variable, to specify a depletion chain manually you can provide the export command with the -c /path/to/chain/file option.

Plotting data

PostOMC provides the pomc plot command to quickly plot data from the depletion_results.h5 file:

Usage: pomc plot [OPTIONS] FILE

Options:
  -n, --nuclides TEXT
  -u, --unit TEXT         The desired unit.  [default: g/cm**3]
  -t, --time-unit TEXT    The desired time unit.  [default: d]
  -m, --material INTEGER  Id of the desired material
  -o, --output TEXT       Path to the output file.  [default: depletion.png]
  -c, --chain TEXT        Path to a depletion chain file.
  --help                  Show this message and exit.

Examples

To plot the mass density of U235 and Pu239 from the depletion_results.h5 file in SVG format:

$ uv run pomc plot data/depletion_results.h5 -n "U235 Pu239" -o depletion.svg -u "g/cm**3"