From 01cd2cc8ddcc791077dbdad7875b148bdfebece9 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Mon, 24 Apr 2023 10:53:00 -0500
Subject: [PATCH] Check that distances are all positive

Co-authored-by: Ethan Peterson <ethan.peterson@mit.edu>
---
 openmc/model/surface_composite.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/openmc/model/surface_composite.py b/openmc/model/surface_composite.py
index 0f4d7cc7f..22724c675 100644
--- a/openmc/model/surface_composite.py
+++ b/openmc/model/surface_composite.py
@@ -1144,6 +1144,9 @@ class CruciformPrism(CompositeSurface):
     @distances.setter
     def distances(self, values):
         values = np.array(values, dtype=float)
+        # check for positive values
+        if not (values > 0).all():
+            raise ValueError("distances must be positive")
         # Check for monotonicity
         if (values[1:] > values[:-1]).all() or (values[1:] < values[:-1]).all():
             self._distances = values