# Development **URL:** https://openmc.discourse.group/c/development/6.md [Latest](https://openmc.discourse.group/latest.md) · [Categories](https://openmc.discourse.group/categories.md) --- ## [About the Development category](https://openmc.discourse.group/t/about-the-development-category/672)
**Author:** [@paulromano](https://openmc.discourse.group/u/paulromano)\ **Replies:** 0
Discuss development topics, whether for core contributions or private R&D --- ## [Notice regarding limits on number of open pull requests](https://openmc.discourse.group/t/notice-regarding-limits-on-number-of-open-pull-requests/6503)
**Author:** [@paulromano](https://openmc.discourse.group/u/paulromano)\ **Replies:** 0\ **Last updated:** [October 14, 2026, 7:24pm UTC](https://openmc.discourse.group/t/notice-regarding-limits-on-number-of-open-pull-requests/6503 "2026-10-14T19:24:27Z")
I wanted to let people in the community know that as of today, we are enforcing a limit on the number of open pull requests (5) that any individual can have on the OpenMC repository. The project, like many, has seen an i… --- ## [ACTINV: an activation bridge for OpenMC R2S workflows](https://openmc.discourse.group/t/actinv-an-activation-bridge-for-openmc-r2s-workflows/6473)
**Author:** [@connoravila](https://openmc.discourse.group/u/connoravila)\ **Replies:** 0\ **Last updated:** [September 22, 2026, 2:12pm UTC](https://openmc.discourse.group/t/actinv-an-activation-bridge-for-openmc-r2s-workflows/6473 "2026-09-22T14:12:49Z")
Hi all, We develop ACTINV, an open-source activation and nuclide-inventory solver, dual-licensed under MIT or Apache-2.0. We’ve added a small example that takes an OpenMC neutron flux tally, calculates activation and de… --- ## [New vscode extension for openmc](https://openmc.discourse.group/t/new-vscode-extension-for-openmc/6220)
**Author:** [@villads](https://openmc.discourse.group/u/villads)\ **Replies:** 5\ **Last updated:** [September 14, 2026, 1:23pm UTC](https://openmc.discourse.group/t/new-vscode-extension-for-openmc/6220 "2026-09-14T13:23:07Z")
Hello, I have made an extension for VSCode that can inspect Statepoint files from OpenMC simulations to give an overview of general stats, tallies, meshes, and such. I have mainly been using the simulation tool Geant4 … --- ## [Inquiry regarding delayed neutron removal](https://openmc.discourse.group/t/inquiry-regarding-delayed-neutron-removal/6463)
**Author:** [@zamzaewoogi](https://openmc.discourse.group/u/zamzaewoogi)\ **Replies:** 0\ **Last updated:** [September 10, 2026, 2:18am UTC](https://openmc.discourse.group/t/inquiry-regarding-delayed-neutron-removal/6463 "2026-09-10T02:18:43Z")
To observe the effect of removing delayed neutrons when specific conditions are met, the code in the physics.cpp file was modified as shown below. // Increment the number of neutrons born delayed if (site.delayed\_group… --- ## [OpenMC for Windows OS - One Click installer - No docker, No WSL, No VM](https://openmc.discourse.group/t/openmc-for-windows-os-one-click-installer-no-docker-no-wsl-no-vm/6425)
**Author:** [@iamsachinshet](https://openmc.discourse.group/u/iamsachinshet)\ **Replies:** 2\ **Last updated:** [August 18, 2026, 10:26am UTC](https://openmc.discourse.group/t/openmc-for-windows-os-one-click-installer-no-docker-no-wsl-no-vm/6425 "2026-08-18T10:26:19Z")
OpenMC now runs natively on Windows..!!! :white\_check\_mark::white\_check\_mark: One Click Installer :grin: No docker :cross\_mark: No WSL :cross\_mark: No VM :cross\_mark: required at all Introducing the OpenMC community a… --- ## [Status/Plans to merge GPU OpenMP branch](https://openmc.discourse.group/t/status-plans-to-merge-gpu-openmp-branch/6056)
**Author:** [@mattb](https://openmc.discourse.group/u/mattb)\ **Replies:** 6\ **Last updated:** [August 14, 2026, 1:51pm UTC](https://openmc.discourse.group/t/status-plans-to-merge-gpu-openmp-branch/6056 "2026-08-14T13:51:33Z")
I have seen the development on OpenMP target offload at GitHub - exasmr/openmc: OpenMC Monte Carlo Code, are there plans to merge these two efforts? What are blockers in pursuing such a merge? --- ## [Can a voxelized F8 tally be interpreted as an efficiency contribution map?](https://openmc.discourse.group/t/can-a-voxelized-f8-tally-be-interpreted-as-an-efficiency-contribution-map/6386)
**Author:** [@Nadaloi](https://openmc.discourse.group/u/Nadaloi)\ **Replies:** 1\ **Last updated:** [June 30, 2026, 5:51pm UTC](https://openmc.discourse.group/t/can-a-voxelized-f8-tally-be-interpreted-as-an-efficiency-contribution-map/6386 "2026-06-30T17:51:14Z")
Hello everyone, I am working on the characterization of an HPGe detector with MCNP. I have voxelized the active germanium crystal into many small cells and assigned an F8 pulse-height tally to each voxel. By integratin… --- ## [Question on KERMA data (regading MT=301 and MT=901) generation and energy-deposition normalization](https://openmc.discourse.group/t/question-on-kerma-data-regading-mt-301-and-mt-901-generation-and-energy-deposition-normalization/6356)
**Author:** [@lee-siy](https://openmc.discourse.group/u/lee-siy)\ **Replies:** 0\ **Last updated:** [June 8, 2026, 2:01pm UTC](https://openmc.discourse.group/t/question-on-kerma-data-regading-mt-301-and-mt-901-generation-and-energy-deposition-normalization/6356 "2026-06-08T14:01:31Z")
Hello, I am using OpenMC depletion with CoupledOperator function. When I use the OpenMC HDF5 library based on ENDF/B-VII.1, I do not encounter any issue when using normalization\_mode="energy-deposition of energy calcula… --- ## [HexLattice cell rotation does not appear to preserve DistribcellFilter tally spatial ordering](https://openmc.discourse.group/t/hexlattice-cell-rotation-does-not-appear-to-preserve-distribcellfilter-tally-spatial-ordering/6352)
**Author:** [@Holtan](https://openmc.discourse.group/u/Holtan)\ **Replies:** 0\ **Last updated:** [June 6, 2026, 8:46pm UTC](https://openmc.discourse.group/t/hexlattice-cell-rotation-does-not-appear-to-preserve-distribcellfilter-tally-spatial-ordering/6352 "2026-06-06T20:46:32Z")
HexLattice cell rotation appears to break DistribcellFilter tally spatial ordering Summary: Rotating the cell containing a HexLattice via cell.rotation as described in pull request #1232 produces correct geometry for tra… --- ## [Using MGXS from NJOY](https://openmc.discourse.group/t/using-mgxs-from-njoy/6245)
**Author:** [@mfnash](https://openmc.discourse.group/u/mfnash)\ **Replies:** 3\ **Last updated:** [March 14, 2026, 2:43am UTC](https://openmc.discourse.group/t/using-mgxs-from-njoy/6245 "2026-03-14T02:43:44Z")
Hi all, I have a desire to use MGXS generated with NJOY in OpenMC. I am leaning towards a new method analogous to “from\_endf” under the openmc.data.IncidentNeutron class, namely “from\_gendf”. I am envisioning that, wit… --- ## [Notebook lm project for ORNL Molten salt reactor reports](https://openmc.discourse.group/t/notebook-lm-project-for-ornl-molten-salt-reactor-reports/6243)
**Author:** [@pranav](https://openmc.discourse.group/u/pranav)\ **Replies:** 1\ **Last updated:** [March 4, 2026, 5:59am UTC](https://openmc.discourse.group/t/notebook-lm-project-for-ornl-molten-salt-reactor-reports/6243 "2026-03-04T05:59:20Z")
The notebook supports chatting with the ORNL reports published during the MSRE experiment. Based on MSR report archive: GitHub - openmsr/msr-archive: curated documents pertaining to early molten salt reactor research.… --- ## [New OpenMC Post Processing Code for Unstructured Mesh Analysis](https://openmc.discourse.group/t/new-openmc-post-processing-code-for-unstructured-mesh-analysis/6231)
**Author:** [@thallam](https://openmc.discourse.group/u/thallam)\ **Replies:** 0\ **Last updated:** [February 19, 2026, 8:27pm UTC](https://openmc.discourse.group/t/new-openmc-post-processing-code-for-unstructured-mesh-analysis/6231 "2026-02-19T20:27:31Z")
Howdy, I’ve been working with unstructured meshes in OpenMC and got tired of the post-processing side of things, so I built a tool to make it easier: TONI-Exo (Translator for OpenMC Neutron Information To Exodus). Op… --- ## [Depletion Timings](https://openmc.discourse.group/t/depletion-timings/6199)
**Author:** [@Jarret](https://openmc.discourse.group/u/Jarret)\ **Replies:** 0\ **Last updated:** [January 28, 2026, 10:17pm UTC](https://openmc.discourse.group/t/depletion-timings/6199 "2026-01-28T22:17:59Z")
Is there any chance we can get the depletion modules updated to include the ability to track the timing of the transport and depletion sections of a depletion run separately? I use them to optimize step size and counting… --- ## [CPM dependencies](https://openmc.discourse.group/t/cpm-dependencies/6093)
**Author:** [@albertop](https://openmc.discourse.group/u/albertop)\ **Replies:** 0\ **Last updated:** [October 30, 2025, 2:42pm UTC](https://openmc.discourse.group/t/cpm-dependencies/6093 "2025-10-30T14:42:18Z")
Hello, Do you think it may be beneficial to include some standard dependencies via CPM instead of submodules? --- ## [Geometry with openmc](https://openmc.discourse.group/t/geometry-with-openmc/6054)
**Author:** [@fakhar](https://openmc.discourse.group/u/fakhar)\ **Replies:** 3\ **Last updated:** [October 14, 2025, 10:30pm UTC](https://openmc.discourse.group/t/geometry-with-openmc/6054 "2025-10-14T22:30:44Z")
I’m trying to recreate the geometry shown in my attached image using OpenMC and Python. It consists of several concentric layers (like squares with rounded corners), each one representing different materials — fuel, cla… --- ## [Mixing programming languages](https://openmc.discourse.group/t/mixing-programming-languages/6001)
**Author:** [@vitmog](https://openmc.discourse.group/u/vitmog)\ **Replies:** 4\ **Last updated:** [September 24, 2025, 7:52pm UTC](https://openmc.discourse.group/t/mixing-programming-languages/6001 "2025-09-24T19:52:47Z")
Hi everyone! My issue is addressed to the principal OpenMC developers. Is it allowed using existent third-party modules written in other compatible with GCC compilers languages, such as Fortran, in the C++ OpenMC core?… --- ## [Plotting importance maps](https://openmc.discourse.group/t/plotting-importance-maps/6008)
**Author:** [@lio\_fr](https://openmc.discourse.group/u/lio_fr)\ **Replies:** 0\ **Last updated:** [September 17, 2025, 5:04pm UTC](https://openmc.discourse.group/t/plotting-importance-maps/6008 "2025-09-17T17:04:16Z")
Hello ! I am currently experimenting with the different weight windows generation routines, and I would like to plot the importance maps. Is there a way to do that? For reference, I am using the latest OpenMC version (0… --- ## [Pending Split Plot Classes PR](https://openmc.discourse.group/t/pending-split-plot-classes-pr/5963)
**Author:** [@bpolania](https://openmc.discourse.group/u/bpolania)\ **Replies:** 1\ **Last updated:** [August 21, 2025, 6:28pm UTC](https://openmc.discourse.group/t/pending-split-plot-classes-pr/5963 "2025-08-21T18:28:51Z")
Hello All, I opened a PR a couple of weeks ago, but it seems to be stuck. The first one I got approved for went quickly, so I was wondering if I should just keep waiting or if I can ping someone about it. Here is the PR… --- ## [Remove\_redundant\_surfaces() for identical planes with different a, b, c, d (proportional)](https://openmc.discourse.group/t/remove-redundant-surfaces-for-identical-planes-with-different-a-b-c-d-proportional/5444)
**Author:** [@wxinyan](https://openmc.discourse.group/u/wxinyan)\ **Replies:** 2\ **Last updated:** [April 21, 2025, 10:03pm UTC](https://openmc.discourse.group/t/remove-redundant-surfaces-for-identical-planes-with-different-a-b-c-d-proportional/5444 "2025-04-21T22:03:39Z")
Hello group, If my observation is correct, I noticed that remove\_redundant\_surfaces(), or remove\_surfs in the legacy version, does not merge identical surfaces with different parameters. For example, x+y+z=1 and 2x+2y+2… --- ## [Spin off checkvalue](https://openmc.discourse.group/t/spin-off-checkvalue/5242)
**Author:** [@tjlaboss](https://openmc.discourse.group/u/tjlaboss)\ **Replies:** 1\ **Last updated:** [February 14, 2025, 10:47pm UTC](https://openmc.discourse.group/t/spin-off-checkvalue/5242 "2025-02-14T22:47:05Z")
openmc.checkvalue isn’t the only module for type enforcement in Python, but it is simple, clean, and intuitive. Other projects may benefit from having checkvalue as an import. Would it be reasonable to spin off checkval… --- ## [Error with custom cross section](https://openmc.discourse.group/t/error-with-custom-cross-section/5218)
**Author:** [@openmc\_user](https://openmc.discourse.group/u/openmc_user)\ **Replies:** 0\ **Last updated:** [February 5, 2025, 11:21pm UTC](https://openmc.discourse.group/t/error-with-custom-cross-section/5218 "2025-02-05T23:21:02Z")
Hello, I’ve been trying to use NJOY generated custom cross sections for high temperatures (~10000 K). I converted the NJOY generated cross sections in ace files to hdf5. It generates the hdf5 files with a warning messag… --- ## [Unstructured mesh data output update](https://openmc.discourse.group/t/unstructured-mesh-data-output-update/5210)
**Author:** [@pshriwise](https://openmc.discourse.group/u/pshriwise)\ **Replies:** 0\ **Last updated:** [January 30, 2025, 7:49pm UTC](https://openmc.discourse.group/t/unstructured-mesh-data-output-update/5210 "2025-01-30T19:49:00Z")
Issue related to removal of automated writing of unstructured mesh data during the openmc\_statepoint\_write call in C++ in favor of the more flexible option in the Python API. Please chime in if this is going to affect yo… --- ## [Polygon yz basis bug](https://openmc.discourse.group/t/polygon-yz-basis-bug/5124)
**Author:** [@wxinyan](https://openmc.discourse.group/u/wxinyan)\ **Replies:** 1\ **Last updated:** [January 10, 2025, 10:39pm UTC](https://openmc.discourse.group/t/polygon-yz-basis-bug/5124 "2025-01-10T22:39:00Z")
Hello group, There might be a bug in the model.polygon composite surface. I am trying to create a polygon like the following: It creates a rhombus tube along the designated axis depending on the basis parameter. Thi… --- ## [Perhaps the effects of the two value of parameter 'row\_colume' of 'get\_xs, 'outin' and 'inout', have been wrongly swapped?](https://openmc.discourse.group/t/perhaps-the-effects-of-the-two-value-of-parameter-row-colume-of-get-xs-outin-and-inout-have-been-wrongly-swapped/5078)
**Author:** [@flowersoul](https://openmc.discourse.group/u/flowersoul)\ **Replies:** 1\ **Last updated:** [December 23, 2024, 8:29am UTC](https://openmc.discourse.group/t/perhaps-the-effects-of-the-two-value-of-parameter-row-colume-of-get-xs-outin-and-inout-have-been-wrongly-swapped/5078 "2024-12-23T08:29:58Z")
hello,everyone! i have use pwr pin to learn the MGXS generation, but when i use energylist = \[0, 1.2e-7, 4.5e-7, 3.05902e-6, 1.30073e-4, 6.73795e-2, 20\] groups = openmc.mgxs.EnergyGroups(\[energy\*1e6 for energy in energ… --- ## [H5m xmdf med workflows](https://openmc.discourse.group/t/h5m-xmdf-med-workflows/4418)
**Author:** [@TruthSeeker](https://openmc.discourse.group/u/TruthSeeker)\ **Replies:** 6\ **Last updated:** [September 12, 2024, 3:35pm UTC](https://openmc.discourse.group/t/h5m-xmdf-med-workflows/4418 "2024-09-12T15:35:17Z")
Hi, My apologies if this is reproduced somewhere else but I couldn’t find it. Is there a reason why med or xmdf cant be used for dagmc and openmc when they also seem to be hdf5 based mesh transport formats? Would it be … --- ## [Depletion using analytical solution](https://openmc.discourse.group/t/depletion-using-analytical-solution/3629)
**Author:** [@pferney](https://openmc.discourse.group/u/pferney)\ **Replies:** 7\ **Last updated:** [September 4, 2024, 9:24pm UTC](https://openmc.discourse.group/t/depletion-using-analytical-solution/3629 "2024-09-04T21:24:30Z")
Hi everyone, While using openmc a lot for various purposes, I wondered if they were a solver using analytical solution for depletion in openmc. I think the answer is no, right ? I mean an algorithm that solves the prob… --- ## [Free GPUs for Benchmarks (on salad.com)](https://openmc.discourse.group/t/free-gpus-for-benchmarks-on-salad-com/4739)
**Author:** [@saladbob](https://openmc.discourse.group/u/saladbob)\ **Replies:** 0\ **Last updated:** [August 29, 2024, 7:58pm UTC](https://openmc.discourse.group/t/free-gpus-for-benchmarks-on-salad-com/4739 "2024-08-29T19:58:12Z")
Hello! I’m the founder of salad.com dropping a note here to see if anyone wants to take me up on an offer of free GPUs in return for publishing your work as a blog post or reference architecture? We’re a relatively ne… --- ## [Modifying the source code to reduce the amount of tracking](https://openmc.discourse.group/t/modifying-the-source-code-to-reduce-the-amount-of-tracking/4575)
**Author:** [@hopenmc](https://openmc.discourse.group/u/hopenmc)\ **Replies:** 5\ **Last updated:** [August 20, 2024, 5:11pm UTC](https://openmc.discourse.group/t/modifying-the-source-code-to-reduce-the-amount-of-tracking/4575 "2024-08-20T17:11:29Z")
Hi all, I am trying to track all the generated particles in the simulation but only in certain cell\_ids and material\_ids. It seems that for now, when you set tracks=True in the run, it saves all the tracks without any … --- ## [Different source in the system](https://openmc.discourse.group/t/different-source-in-the-system/4594)
**Author:** [@Criss](https://openmc.discourse.group/u/Criss)\ **Replies:** 6\ **Last updated:** [July 25, 2024, 4:30am UTC](https://openmc.discourse.group/t/different-source-in-the-system/4594 "2024-07-25T04:30:56Z")
Hello everyone, I’m starting my studies with Openmc and I have some questions. My system is simple, it contains a fuel and a cylindrical source in the center, in which I described the source as monoenergetic and also as… [Next page](https://openmc.discourse.group/c/development/6.md?page=1)