# Problem with openmc.MeshSurfaceFilter (OpenMC hangs) **URL:** \ **Category:** User Support\ **Created:** [January 10, 2024, 3:17pm UTC](https://openmc.discourse.group/t/problem-with-openmc-meshsurfacefilter-openmc-hangs/3813 "2024-01-10T15:17:41Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![riwa](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/riwa/32/3218_2.png) [@riwa](https://openmc.discourse.group/u/riwa)\ **Post date:** [January 10, 2024, 3:17pm UTC](https://openmc.discourse.group/t/problem-with-openmc-meshsurfacefilter-openmc-hangs/3813/1 "2024-01-10T15:17:41Z")
Hello OpenMC community, I ran recently in a problem when using the `openmc.MeshSurfaceFilter` At a certain point the simulations just hangs at a certain batch (and most likely a particle) and just won’t continue. I put below a version of our model that is reduced to the bare minimum to demonstrate the issue. A simple mono-energetic Source of quadratic-plane shape and a little farther away a rectangular `RegularMesh`. On this mesh the current is tallied with the `openmc.MeshSurfaceFilter`. All with `fill = None`, so no materials involved. With the particular setting of seed to `settings.seed = 21` the simulation hengs forever in the third simulated batch. Changing the seed value just shifts the time, when the problem occurs I am using the last versi on of OpenMC ( 0.14.1), but the error occurred at the previous release, too I tried to get some debug info by increasing verbosity and even by using a debugBuild of OpenMC, but got no leads from that. Any help would be appreciated. I can of course run more tests on demand and advice. Best Richard [Simple\_model\_meshsurface\_debug.ipynb](https://openmc.discourse.group/uploads/short-url/u836Ya4xPfmKRPYd4sr9Z1me6mC.ipynb) (111.6 KB) ---
**Author:** ![riwa](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/riwa/32/3218_2.png) [@riwa](https://openmc.discourse.group/u/riwa)\ **Post date:** [January 15, 2024, 4:35pm UTC](https://openmc.discourse.group/t/problem-with-openmc-meshsurfacefilter-openmc-hangs/3813/2 "2024-01-15T16:35:04Z")
Hi, Since there was no response - would it be better to open an issue so someone can hava a look at the problem? Or look for workarounds as to not use `MeshSurfaceFilter` for e.g.? I suspect a pure geometric reason since there is no material involved in the test case. Thanks, Richard ```auto %%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%% ############### %%%%%%%%%%%%%%%%%%%%%%%% ################## %%%%%%%%%%%%%%%%%%%%%%% ################### %%%%%%%%%%%%%%%%%%%%%%% #################### %%%%%%%%%%%%%%%%%%%%%% ##################### %%%%%%%%%%%%%%%%%%%%% ###################### %%%%%%%%%%%%%%%%%%%% ####################### %%%%%%%%%%%%%%%%%% ####################### %%%%%%%%%%%%%%%%% ###################### %%%%%%%%%%%%%%%%% #################### %%%%%%%%%%%%%%%%% ################# %%%%%%%%%%%%%%%%% ############### %%%%%%%%%%%%%%%% ############ %%%%%%%%%%%%%%% ######## %%%%%%%%%%%%%% %%%%%%%%%%% | The OpenMC Monte Carlo Code Copyright | 2011-2023 MIT, UChicago Argonne LLC, and contributors License | https://docs.openmc.org/en/latest/license.html Version | 0.14.1-dev Git SHA1 | ec8850deac2046668ab087f1f5f14a9df4614008 Date/Time | 2024-01-15 17:11:07 OpenMP Threads | 48 Reading model XML file './model.xml' ... WARNING: Other XML file input(s) are present. These files may be ignored in favor of the ./model.xml file. Reading cross sections XML file... Minimum neutron data temperature: 1.7976931348623157e+308 K Maximum neutron data temperature: 0 K Preparing distributed cell instances... Writing summary.h5 file... ===============> FIXED SOURCE TRANSPORT SIMULATION <=============== Simulating batch 1 Simulating batch 2 Simulating batch 3 -- ENDLESS LOOP -- ```