TRISO model generation issue

User Support
1

I’m very new to OpenMC but I am trying to use it to model a pebble bed reactor with TRISO fuel.

My problem is when I try to generate a model of a single pebble, or a reactor core filled with graphite only pebbles, the geometry generation takes longer than a few hours and I’ve had to code automatically killed on my computer before. This is just to generate and plot the geometry, I haven’t tried any criticality simulation yet.

I found and used the TRISO particle example code on the openmc website and have been using that as the basis for my random triso generation. I’ve tried messing with the lattice settings but it doesn’t seem to help, and I don’t know how to optimize it for my case.

I also checked my openmc version, v0.14.0, because I saw there was an API added v0.12 for TRISO generation. Specifically for the single pebble model it’s set to a pf of 0.05, because I’ve heard larger pf can cause issues. However, when I eventually go to fill the core I will most likely need a pf of about 0.6, so any recommendations for this as well is appreciated.

Openmc is currently on my laptop so I can work on it outside of home. My next idea is to try installing openmc on my desktop to see if it might be a hardware issue.

Any advice is appreciated

2

Update: I got openmc on my desktop and tried running the same program. On my laptop, it would take an hour at least and not show the openmc startup dialogue. On my desktop, it took about two minutes then the openmc startup showed up but said it was killed. There was also a little output about a file or directory not being opened, but it didn’t affect the test program I tried before the TRISO pebble model. Here is the output:

mca_base_component_repository_open: unable to open mca_btl_openib: librdmacm.so.1: cannot open shared object file: No such file or directory (ignored)
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             | The OpenMC Monte Carlo Code
   Copyright | 2011-2023 MIT, UChicago Argonne LLC, and contributors
     License | https://docs.openmc.org/en/latest/license.html
     Version | 0.14.0
    Git SHA1 | e1a8ee7794b441c992426f17fafe216391cbba83
   Date/Time | 2024-03-28 18:31:41

MPI Processes | 1
OpenMP Threads | 4

Reading settings XML file…
Reading materials XML file…
Reading geometry XML file…
Preparing distributed cell instances…
Killed

3

I managed to get the model for a TRISO pebble to work! I think there was an issue with the size or shape of my lattice.
Now that I am able to run this geometry for an k eigenvalue simulation, I am getting the following in the output:

WARNING: Cannot reflect particle 1 off surface in a lower universe. WARNING: Cannot reflect particle 26 off surface in a lower universe.

WARNING: WARNING: Cannot reflect particle 51 off surface in a lower universe.
Cannot reflect particle 78 off surface in a lower universe.
WARNING: Cannot reflect particle 27 off surface in a lower universe.
WARNING: Cannot reflect particle 2 off surface in a lower universe.
WARNING: Cannot reflect particle 52 off surface in a lower universe.
WARNING: Cannot reflect particle 79 off surface in a lower universe.
WARNING: Cannot reflect particle 28 off surface in a lower universe.
WARNING: Cannot reflect particle 3 off surface in a lower universe.
WARNING: Cannot reflect particle 54 off surface in a lower universe.
WARNING: Cannot reflect particle 80 off surface in a lower universe.
WARNING: Cannot reflect particle 29 off surface in a lower universe.
ERROR: Maximum number of lost particles has been reached.

Online there were a few instances of people with similar warnings, and they claimed it had to do with root cell regions or dimensions, but what I have done to edit my root cells and universe haven’t helped.
In case it might help, I have my .py code included. I can’t upload a file so I’ll just link to a doc file.

TRISO model