95% of external source sites rejected

User Support
1

Hi there. I’m trying to model a fusion reactor in OpenMC.

I get the following error message:
ERROR: More than 95% of external source sites sampled were rejected. Please check your external source’s spatial definition.

My source code is as follows. I have 18 spheres whose centres lie on a ring of radius 700 in the xy plane. The spheres are located in void material (fill = None). My universe boundary edges are really far away (a z-cylinder with radius 1500, and 2 planes at z = ± 1500.

image
image864×607 59.8 KB

2

This is a very common issue (see other Discourse posts with the same error message) that likely has to do with the definition of the position of your source. You might have source locations in vacuum regions which can cause the issue

1 Like
3

Thank you. I replaced some void materials with low density hydrogen, and this seems to have solved the issue!

1 Like