remove json for decay energy

paulromano · Nov 18, 2022 · Oct 13, 2022 · Oct 14, 2022 · Oct 31, 2022 · Oct 31, 2022
commit 542553b50098360e2e6fe117454c5211bf294f4d
diff --git a/openmc/data/data.py b/openmc/data/data.py
@@ -203,7 +203,6 @@
 # Used in half_life function as a cache
 _HALF_LIFE = {}
 _LOG_TWO = log(2.0)
-_DECAY_ENERGY = {}
 
 def atomic_mass(isotope):
     """Return atomic mass of isotope in atomic mass units.
@@ -333,34 +332,6 @@ def decay_constant(isotope):
     return _LOG_TWO / t if t else 0.0
 
 
-def decay_energy(isotope):
-    """Return decay energy of isotope in eV or 0.0 if isotope is stable
-
-    Decay energy values are from the `ENDF/B-VIII.0 decay sublibrary
-    <https://www.nndc.bnl.gov/endf-b8.0/download.html>`_.
-
-    .. versionadded:: 0.14.1
-
-    Parameters
-    ----------
-    isotope : str
-        Name of isotope, e.g., 'U235'
-
-    Returns
-    -------
-    float
-        Decay energy of isotope in [eV]
-
-    """
-    global _DECAY_ENERGY
-    if not _DECAY_ENERGY:
-        # Load ENDF/B-VIII.0 data from JSON file
-        decay_energy_path = Path(__file__).with_name('decay_energy.json')
-        _DECAY_ENERGY = json.loads(decay_energy_path.read_text())
-    t = half_life(isotope)
-    return _DECAY_ENERGY.get(isotope.lower()) if t else 0.0
-
-
 def water_density(temperature, pressure=0.1013):
     """Return the density of liquid water at a given temperature and pressure.
 

@@ -619,3 +619,48 @@ def decay_photon_energy(nuclide: str) -> Optional[Univariate]:
                  "sources listed.")
 
     return _DECAY_PHOTON_ENERGY.get(nuclide)
+
+
+_DECAY_ENERGY = {}
+
+
+def decay_energy(nuclide: str):
+    """Get decay energy value resulting from the decay of a nuclide
+
+    This function relies on data stored in a depletion chain. Before calling it
+    for the first time, you need to ensure that a depletion chain has been
+    specified in openmc.config['chain_file'].
+
+    .. versionadded:: 0.14.0
+
+    Parameters
+    ----------
+    nuclide : str
+        Name of nuclide, e.g., 'H3'
+
+    Returns
+    -------
+    float
+        Decay energy of isotope in [eV].
+    """
+    if not _DECAY_ENERGY:
+        chain_file = openmc.config.get('chain_file')
+        if chain_file is None:
+            raise DataError(
+                "A depletion chain file must be specified with "
+                "openmc.config['chain_file'] in order to load decay data."
+            )
+
+        from openmc.deplete import Chain
+        chain = Chain.from_xml(chain_file)
+        for nuc in chain.nuclides:
+            if nuc.decay_energy:
+                _DECAY_ENERGY[nuc.name] = nuc.decay_energy
+
+        # If the chain file contained no decay energy, warn the user
+        if not _DECAY_ENERGY:
+            warn(f"Chain file '{chain_file}' does not have any decay energy.")
+
+    return _DECAY_ENERGY.get(nuclide)
+
+