From 99dfa1f05304b4e41b6f58a5ec3ed489ad54c790 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <drewej@protonmail.com>
Date: Wed, 11 Sep 2019 10:42:16 -0500
Subject: [PATCH] Return defaultdict(dict) from
 Chain.get_default_fission_yields

---
 openmc/deplete/chain.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/openmc/deplete/chain.py b/openmc/deplete/chain.py
index 5814427852..510112c7c9 100644
--- a/openmc/deplete/chain.py
+++ b/openmc/deplete/chain.py
@@ -412,7 +412,7 @@ class Chain(object):
             names of nuclides with yield data and ``f_yield``
             is a float for the fission yield.
         """
-        out = {}
+        out = defaultdict(dict)
         for nuc in self.nuclides:
             if nuc.yield_data is None:
                 continue