added fns depletion chain

Author: shimwell

src/openmc_data/download/download_endf_chain.py

@@ -38,18 +38,19 @@ class CustomFormatter(
     "-r",
     "--release",
     choices=["b7.1", "b8.0"],
-    default="b7.1",
+    default="b8.0",
     help="The nuclear data library release version. The currently supported "
-         "options are b7.1 and b8.0",
+         "options are b7.1 and b8.0.",
 )
 parser.add_argument(
     "-b",
     "--branching_ratios",
-    choices=["None", "SFR", "PWR"],
-    default="SFR",
+    choices=["None", "SFR", "PWR", "FNS"],
+    default="FNS",
     help="The nuclear data library release version. The currently supported "
          "options are b7.1 and b8.0 with branching ratio options of None, SFR "
-         "or PWR",
+         "(sodium fast reactor), PWR (pressurized water reactor) or FNS "
+         "(fusion neutron source)",
 )
 
 parser.set_defaults()

src/openmc_data/urls_xml.py

@@ -32,6 +32,11 @@
                 "chain": {
                     "url": "https://github.com/openmc-data-storage/openmc_data/raw/main/src/openmc_data/depletion/chain_endf_b8.0_pwr.xml"
                 }
+            },
+            "FNS": {
+                "chain": {
+                    "url": "https://github.com/jbae11/openmc_activator/raw/refs/heads/main/fns_spectrum.chain.xml"
+                }
             }
         }
     }