# Latest **URL:** https://openmc.discourse.group/latest.md [Latest](https://openmc.discourse.group/latest.md) · [Categories](https://openmc.discourse.group/categories.md) --- ## [Welcome to Discourse](https://openmc.discourse.group/t/welcome-to-discourse/7)
**Author:** [@system](https://openmc.discourse.group/u/system)\ **Replies:** 0\ **Last updated:** [August 5, 2020, 2:59pm UTC](https://openmc.discourse.group/t/welcome-to-discourse/7 "2020-08-05T14:59:27Z")
Discussion for users and developers of the OpenMC Monte Carlo particle transport code --- ## [Papers using OpenMC](https://openmc.discourse.group/t/papers-using-openmc/787)
**Author:** [@paulromano](https://openmc.discourse.group/u/paulromano)\ **Replies:** 246\ **Last updated:** [September 22, 2026, 6:34pm UTC](https://openmc.discourse.group/t/papers-using-openmc/787 "2026-09-22T18:34:10Z")
I thought I’d start a topic for anyone wanting to share a paper they wrote in which OpenMC was used, or if you came across a paper that used OpenMC. Here’s one that I just came across using OpenMC for some studies on a … --- ## [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… --- ## [JENDL-5 Depletion cross section](https://openmc.discourse.group/t/jendl-5-depletion-cross-section/6472)
**Author:** [@sadia33](https://openmc.discourse.group/u/sadia33)\ **Replies:** 0\ **Last updated:** [September 22, 2026, 7:10am UTC](https://openmc.discourse.group/t/jendl-5-depletion-cross-section/6472 "2026-09-22T07:10:22Z")
I’m running a core depletion simulation in OpenMC and encountering some discrepancies when using the JENDL-5 depletion cross-section library. Has anyone else faced specific issues or unexpected results with JENDL-5 durin… --- ## [Generating a derived library using OpenMC and tools](https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468)
**Author:** [@alwonj7](https://openmc.discourse.group/u/alwonj7)\ **Replies:** 1\ **Last updated:** [September 18, 2026, 6:36pm UTC](https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468 "2026-09-18T18:36:46Z")
Hello everyone, This is kind of related to OpenMC. I’ve been looking at cross sections and have used the openmc\_data repository to generate/merge cross section files. I have a question about trying to create a library f… --- ## [Shared Secondary Bank](https://openmc.discourse.group/t/shared-secondary-bank/6467)
**Author:** [@yrrepy](https://openmc.discourse.group/u/yrrepy)\ **Replies:** 2\ **Last updated:** [September 17, 2026, 7:21am UTC](https://openmc.discourse.group/t/shared-secondary-bank/6467 "2026-09-17T07:21:24Z")
Anybody have some feedback on its use? I have a large real world problem Neutron transport only Advantg generated wwinp, was already decently optimized Performance hit from secondary shared bank being ON 48xMPI \* 8… --- ## [Update: STARFIRE gap-streaming benchmark finished — MAGIC WW results, looking for a technical read](https://openmc.discourse.group/t/update-starfire-gap-streaming-benchmark-finished-magic-ww-results-looking-for-a-technical-read/6466)
**Author:** [@alanhalley](https://openmc.discourse.group/u/alanhalley)\ **Replies:** 0\ **Last updated:** [September 16, 2026, 6:53pm UTC](https://openmc.discourse.group/t/update-starfire-gap-streaming-benchmark-finished-magic-ww-results-looking-for-a-technical-read/6466 "2026-09-16T18:53:53Z")
Posting an update to my July thread (was asking for a technical read + arXiv endorser while this was still in progress) — the work is finished now, so this is a different ask: I’d like someone who actually knows Weight… --- ## [Dose on a deep shielding problem - Source biasing](https://openmc.discourse.group/t/dose-on-a-deep-shielding-problem-source-biasing/6459)
**Author:** [@thibault](https://openmc.discourse.group/u/thibault)\ **Replies:** 3\ **Last updated:** [September 16, 2026, 5:21pm UTC](https://openmc.discourse.group/t/dose-on-a-deep-shielding-problem-source-biasing/6459 "2026-09-16T17:21:35Z")
Dear OpenMC Community, I am working on a simulation of a DT fusion deep shielding problem. The final goal is to estimate the thickness of concrete required for the dose on the outer layer of the bioshield to remain belo… --- ## [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 … --- ## [Hi, i am new to Openmc,Trying to run the gamma detector ipynb.example it rises lookup error('Unable to get Tally')](https://openmc.discourse.group/t/hi-i-am-new-to-openmc-trying-to-run-the-gamma-detector-ipynb-example-it-rises-lookup-error-unable-to-get-tally/6461)
**Author:** [@Sajalk1234](https://openmc.discourse.group/u/Sajalk1234)\ **Replies:** 1\ **Last updated:** [September 14, 2026, 3:56am UTC](https://openmc.discourse.group/t/hi-i-am-new-to-openmc-trying-to-run-the-gamma-detector-ipynb-example-it-rises-lookup-error-unable-to-get-tally/6461 "2026-09-14T03:56:59Z")
Hi sajal here, i am new to Openmc,Trying to run the gamma detector ipynb.example it rises lookup error(‘Unable to get Tally’).My version is 0.15.3 does it support tally?can any body help? --- ## [ERROR: Failed to check if object '250K' exists — during depletion calculation with fission products](https://openmc.discourse.group/t/error-failed-to-check-if-object-250k-exists-during-depletion-calculation-with-fission-products/6464)
**Author:** [@gang](https://openmc.discourse.group/u/gang)\ **Replies:** 1\ **Last updated:** [September 13, 2026, 8:23am UTC](https://openmc.discourse.group/t/error-failed-to-check-if-object-250k-exists-during-depletion-calculation-with-fission-products/6464 "2026-09-13T08:23:55Z")
I am calculating the burnup, but when I run the code, it shows that the Br81.h5 file does not exist, and I have attached my Python code so that anyone can review it. Everything else works normally if burnup is not calcu… --- ## [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… --- ## [Tallying activation in big geometry](https://openmc.discourse.group/t/tallying-activation-in-big-geometry/6435)
**Author:** [@thibault](https://openmc.discourse.group/u/thibault)\ **Replies:** 3\ **Last updated:** [September 9, 2026, 11:21am UTC](https://openmc.discourse.group/t/tallying-activation-in-big-geometry/6435 "2026-09-09T11:21:08Z")
I am trying to run a full dose simulation including prompt neutrons, prompt photons and delayed photons (through R2S) to estimate the real dose received by workers during operations of an ICF plant. The issue I have is … --- ## [How to restart the depletion calculation when 'diff\_burnable\_mats=True'?](https://openmc.discourse.group/t/how-to-restart-the-depletion-calculation-when-diff-burnable-mats-true/6462)
**Author:** [@CoolSky](https://openmc.discourse.group/u/CoolSky)\ **Replies:** 1\ **Last updated:** [September 7, 2026, 5:07am UTC](https://openmc.discourse.group/t/how-to-restart-the-depletion-calculation-when-diff-burnable-mats-true/6462 "2026-09-07T05:07:17Z")
\# define materials / geometry / settings results = openmc.deplete.Results("./depletion\_results.h5") materials = results.export\_to\_materials(burnup\_index=55,path='./materials.xml') # print(materials) model = openmc.Mode… --- ## [Possible restart bug with 'generations\_per\_batch \> 1': fission bank fills after loading statepoint](https://openmc.discourse.group/t/possible-restart-bug-with-generations-per-batch-1-fission-bank-fills-after-loading-statepoint/6456)
**Author:** [@A\_Bohemian](https://openmc.discourse.group/u/A_Bohemian)\ **Replies:** 2\ **Last updated:** [September 2, 2026, 4:17am UTC](https://openmc.discourse.group/t/possible-restart-bug-with-generations-per-batch-1-fission-bank-fills-after-loading-statepoint/6456 "2026-09-02T04:17:01Z")
The following description is AI-assisted I am using OpenMC 0.16.0 for a k-eigenvalue MGXS calculation. A completed run used: batches = 300 inactive = 100 generations\_per\_batch = 5 The final statepoint has: current… --- ## [Struggle processing TENDL nuclear data for DT fusion activation](https://openmc.discourse.group/t/struggle-processing-tendl-nuclear-data-for-dt-fusion-activation/6437)
**Author:** [@thibault](https://openmc.discourse.group/u/thibault)\ **Replies:** 11\ **Last updated:** [August 31, 2026, 10:21pm UTC](https://openmc.discourse.group/t/struggle-processing-tendl-nuclear-data-for-dt-fusion-activation/6437 "2026-08-31T22:21:28Z")
I am doing activation of steels under DT neutrons irradiations. I have been using the basic ENDF VIII.1 and chain\_endfb81\_sfr.xml from Cross sections - OpenMC. After reading this FNS chains (n,gamma) is only the fourt… --- ## [Flux distribution axial and radial](https://openmc.discourse.group/t/flux-distribution-axial-and-radial/6445)
**Author:** [@DinaEl](https://openmc.discourse.group/u/DinaEl)\ **Replies:** 9\ **Last updated:** [August 30, 2026, 6:06am UTC](https://openmc.discourse.group/t/flux-distribution-axial-and-radial/6445 "2026-08-30T06:06:48Z")
Hello everyone! I have a question about calculating the axial and radial neutron flux distribution in OpenMC. I understand how to define the mesh and the tally, but I’m not sure how to proceed with the post-processing. … --- ## [How to generate the data of Photoatomic in h5 format by myself through the file of mcplib84?](https://openmc.discourse.group/t/how-to-generate-the-data-of-photoatomic-in-h5-format-by-myself-through-the-file-of-mcplib84/4468)
**Author:** [@cro](https://openmc.discourse.group/u/cro)\ **Replies:** 6\ **Last updated:** [August 27, 2026, 9:07am UTC](https://openmc.discourse.group/t/how-to-generate-the-data-of-photoatomic-in-h5-format-by-myself-through-the-file-of-mcplib84/4468 "2026-08-27T09:07:23Z")
I know I can download the ENDF/B-VIII.0 zip at Official Data Libraries | OpenMC, but I’d like to know how the photon in it was converted to get it, to help myself to Learn how to convert data from mcplib84 to h5 format. --- ## [The burnup material was not updated during the criticality search in the depletion calculation.](https://openmc.discourse.group/t/the-burnup-material-was-not-updated-during-the-criticality-search-in-the-depletion-calculation/6446)
**Author:** [@Tan](https://openmc.discourse.group/u/Tan)\ **Replies:** 2\ **Last updated:** [August 27, 2026, 4:06am UTC](https://openmc.discourse.group/t/the-burnup-material-was-not-updated-during-the-criticality-search-in-the-depletion-calculation/6446 "2026-08-27T04:06:34Z")
Hello, I encountered an issue while using OpenMC to perform a criticality search for the calculation of keff​. When I enabled the add\_keff\_search\_control() function in the depletion calculation, I found that the critica… --- ## [Delta tracking in OpenMc](https://openmc.discourse.group/t/delta-tracking-in-openmc/1461)
**Author:** [@Stepniac](https://openmc.discourse.group/u/Stepniac)\ **Replies:** 5\ **Last updated:** [August 26, 2026, 2:14pm UTC](https://openmc.discourse.group/t/delta-tracking-in-openmc/1461 "2026-08-26T14:14:50Z")
Hello, Are there plans to add delta tracking in OpenMC? Delta tracking is implemented in the code UK code MONK by the user using what are called hole materials. Hole materials can be used to represent geometries that … --- ## [OpenMC Monthy Meeting Dates 2026](https://openmc.discourse.group/t/openmc-monthy-meeting-dates-2026/6025)
**Author:** [@pshriwise](https://openmc.discourse.group/u/pshriwise)\ **Replies:** 4\ **Last updated:** [August 26, 2026, 1:41pm UTC](https://openmc.discourse.group/t/openmc-monthy-meeting-dates-2026/6025 "2026-08-26T13:41:15Z")
2026-01-28T16:00:00Z (UTC)→2026-01-28T17:00:00Z (UTC) 2026-02-25T16:00:00Z (UTC)→2026-02-25T17:00:00Z (UTC) 2026-03-25T15:00:00Z (UTC)→2026-03-25T16:00:00Z (UTC) 2026-04-29T15:00:00Z (UTC)→2026-04-29T16:00:00Z (UTC) 2… --- ## [Materials are not updated during the criticality search in the depletion calculation](https://openmc.discourse.group/t/materials-are-not-updated-during-the-criticality-search-in-the-depletion-calculation/6441)
**Author:** [@Tanbo](https://openmc.discourse.group/u/Tanbo)\ **Replies:** 2\ **Last updated:** [August 25, 2026, 5:10am UTC](https://openmc.discourse.group/t/materials-are-not-updated-during-the-criticality-search-in-the-depletion-calculation/6441 "2026-08-25T05:10:24Z")
Hello, I encountered an issue while using OpenMC to perform the keff criticality search. When I enabled the add\_keff\_search\_control() function in the depletion calculation, I found that the criticality search parameter … --- ## [Installing OpenMC on MacOS using spack](https://openmc.discourse.group/t/installing-openmc-on-macos-using-spack/6442)
**Author:** [@jschwartz](https://openmc.discourse.group/u/jschwartz)\ **Replies:** 0\ **Last updated:** [August 24, 2026, 7:35pm UTC](https://openmc.discourse.group/t/installing-openmc-on-macos-using-spack/6442 "2026-08-24T19:35:27Z")
I’ve tried to install OpenMC using spack install py-openmc +mpi ^openmpi ^openmc build\_type=Release. I then do spack load py-openmc, then start a python REPL with python. I start to import openmc and get an error that t… --- ## [Install OpenMC from source on MacOS with Conda](https://openmc.discourse.group/t/install-openmc-from-source-on-macos-with-conda/6208)
**Author:** [@pferney](https://openmc.discourse.group/u/pferney)\ **Replies:** 1\ **Last updated:** [August 24, 2026, 3:35pm UTC](https://openmc.discourse.group/t/install-openmc-from-source-on-macos-with-conda/6208 "2026-08-24T15:35:26Z")
Hi everyone, That’s quite a long time time I struggle with the creation of a conda environment to compile OpenMC on MacOs without utilizing brew. I don’t like brew because I must work with a lot of different environment… --- ## [MuSurfaceFilter usage](https://openmc.discourse.group/t/musurfacefilter-usage/6439)
**Author:** [@LitBen](https://openmc.discourse.group/u/LitBen)\ **Replies:** 0\ **Last updated:** [August 21, 2026, 2:47pm UTC](https://openmc.discourse.group/t/musurfacefilter-usage/6439 "2026-08-21T14:47:51Z")
Hi all, I’m testing MuSurfaceFilter in OpenMC 0.15.3: tally.filters = \[ openmc.SurfaceFilter(\[cz\_2\]), openmc.MuSurfaceFilter(\[-1.0, 0.0, 1.0\]), \] tally.scores = \["current"\] with cz\_2 = openmc.ZCylinder(r=130.… --- ## [File Error When Installing MOAB for DAGMC Using WSL2](https://openmc.discourse.group/t/file-error-when-installing-moab-for-dagmc-using-wsl2/5225)
**Author:** [@aidan](https://openmc.discourse.group/u/aidan)\ **Replies:** 4\ **Last updated:** [August 18, 2026, 3:56pm UTC](https://openmc.discourse.group/t/file-error-when-installing-moab-for-dagmc-using-wsl2/5225 "2026-08-18T15:56:26Z")
Hello everyone. I’ve been trying to set up the necessary tools for importing CAD and mesh-based geometries into OpenMC, and I’ve been running into an issue when installing MOAB (a required dependency of DAGMC). I can fol… --- ## [Installation via pip (C-Python bindings)](https://openmc.discourse.group/t/installation-via-pip-c-python-bindings/6424)
**Author:** [@rzehumat](https://openmc.discourse.group/u/rzehumat)\ **Replies:** 2\ **Last updated:** [August 18, 2026, 2:47pm UTC](https://openmc.discourse.group/t/installation-via-pip-c-python-bindings/6424 "2026-08-18T14:47:59Z")
I was wondering if the whole code could be installable via pip. As the user guide mentiones, Python API is installable via pip, but the rest has to be installed from Conda/Docker/Spack or compiled via CMake. Idea Could… --- ## [Discrepancy between OpenMC and SCALE depletion results](https://openmc.discourse.group/t/discrepancy-between-openmc-and-scale-depletion-results/6358)
**Author:** [@imelnyk](https://openmc.discourse.group/u/imelnyk)\ **Replies:** 10\ **Last updated:** [August 18, 2026, 10:52am UTC](https://openmc.discourse.group/t/discrepancy-between-openmc-and-scale-depletion-results/6358 "2026-08-18T10:52:32Z")
Hi there, I am modeling depletion of VVER-440 fuel assembly using CoupledOperator and CECMIntegrator and want to compare the results of the OpenMC simulation with a similar SCALE6.2.4 t-6 depl sequence results. However… --- ## [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… --- ## [Fetter vs NRC limits for activated fusion materials and a question about R2S at long cooling times](https://openmc.discourse.group/t/fetter-vs-nrc-limits-for-activated-fusion-materials-and-a-question-about-r2s-at-long-cooling-times/6436)
**Author:** [@Vithushan](https://openmc.discourse.group/u/Vithushan)\ **Replies:** 2\ **Last updated:** [August 18, 2026, 10:08am UTC](https://openmc.discourse.group/t/fetter-vs-nrc-limits-for-activated-fusion-materials-and-a-question-about-r2s-at-long-cooling-times/6436 "2026-08-18T10:08:02Z")
Hi all, Still fairly new to OpenMC, so apologies if some of this is obvious. I’m on 0.15.3 from conda-forge (0.16.0 doesn’t seem to be up there yet) and I’ve been poking at the waste classification methods. The docstri… [Next page](https://openmc.discourse.group/latest.md?page=1)