Merge pull request #102 from paulromano/mcnp-expand-weight

Support expanding elements in MCNP by weight percent

CHANGELOG.md

@@ -12,7 +12,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * The `Plugin.__call__` method now supports a `cleanup` argument
   ([#92](https://github.com/watts-dev/watts/pull/92))
 * Support for natural element expansion in `PluginMCNP`
-  ([#93](https://github.com/watts-dev/watts/pull/93))
+  ([#93](https://github.com/watts-dev/watts/pull/93),
+  [#102](https://github.com/watts-dev/watts/pull/102))
 * Reorganize the structure of `csv_data` generated by `PluginSAS` ([#98](https://github.com/watts-dev/watts/pull/98))
 
 ### Fixed

doc/source/user/plugins.rst

@@ -242,10 +242,10 @@ MCNP input file, this feature can be utilized by adding a `filter section
 .. code-block:: jinja
 
     {% filter expand_element %}
-    m1    24000.70c  0.17
-          26000.70c  0.79
-          28000.70c  0.10
-          42000.70c  0.02
+    m1    24000.70c  -0.17
+          26000.70c  -0.79
+          28000.70c  -0.10
+          42000.70c  -0.02
     {% endfilter %}
 
 Natural elements can be represented using the standard ZAID identifiers as above
@@ -254,10 +254,10 @@ Natural elements can be represented using the standard ZAID identifiers as above
 .. code-block:: jinja
 
     {% filter expand_element %}
-    m1    Cr.70c  0.17
-          Fe.70c  0.79
-          Ni.70c  0.10
-          Mo.70c  0.02
+    m1    Cr.70c  -0.17
+          Fe.70c  -0.79
+          Ni.70c  -0.10
+          Mo.70c  -0.02
     {% endfilter %}
 
 The ``expand_element`` custom filter also accepts a single argument specifying
@@ -266,10 +266,10 @@ what cross section suffix to apply by default when one is missing:
 .. code-block:: jinja
 
     {% filter expand_element('70c') %}
-    m1    Cr 0.17
-          Fe 0.79
-          Ni 0.10
-          Mo 0.02
+    m1    Cr  -0.17
+          Fe  -0.79
+          Ni  -0.10
+          Mo  -0.02
     {% endfilter %}
 
 By default, :class:`~watts.PluginMCNP` will look for the ``xsdir`` file found

doc/source/user/usage.rst

@@ -37,10 +37,7 @@ object::
         values=[10.0, 20.0, 0.05]
     )
 
-Most native Python datatypes (:class:`int`, :class:`float`, :class:`bool`,
-:class:`str`, :class:`list`, :class:`set`, :class:`tuple`, :class:`dict`) are
-supported along with :class:`NumPy arrays <numpy.ndarray>` as well. Parameters
-can be saved to a pickle file::
+Parameters can be saved to a pickle file::
 
     params.save('parameters.pkl')
 

src/watts/fundamental_data.py

@@ -26,8 +26,10 @@
 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 """
 
+import itertools
 import re
-from typing import List, Tuple
+from pathlib import Path
+from typing import List, Tuple, Dict
 
 
 ATOMIC_SYMBOL = {
@@ -188,3 +190,42 @@ def isotopes(element: str) -> List[Tuple[str, float]]:
         if re.match(r'{}\d+'.format(element), kv[0]):
             result.append(kv)
     return result
+
+
+# Used in atomic_mass function as a cache
+_ATOMIC_MASS: Dict[str, float] = {}
+
+
+def atomic_mass(nuclide):
+    """Return atomic mass of isotope in atomic mass units.
+
+    Atomic mass data comes from the `Atomic Mass Evaluation 2020
+    <https://doi.org/10.1088/1674-1137/abddaf>`_.
+
+    Parameters
+    ----------
+    nuclide : str
+        Name of nuclide, e.g., 'Pu239'
+
+    Returns
+    -------
+    float
+        Atomic mass of nuclide in [amu]
+
+    """
+    if not _ATOMIC_MASS:
+        # Load data from AME2020 file
+        mass_file = Path(__file__).with_name('mass_1.mas20.txt')
+        with mass_file.open('r') as ame:
+            # Read lines in file starting at line 37
+            for line in itertools.islice(ame, 36, None):
+                name = f'{line[20:22].strip()}{int(line[16:19])}'
+                mass = float(line[106:109]) + 1e-6*float(
+                    line[110:116] + '.' + line[117:123])
+                _ATOMIC_MASS[name.lower()] = mass
+
+    # Get rid of metastable information
+    if '_' in nuclide:
+        nuclide = nuclide[:nuclide.find('_')]
+
+    return _ATOMIC_MASS[nuclide.lower()]