Depletion calculations do not deplete

User Support
1

I installed OpenMC 0.14.0 and downloaded the depletion example jupyter notebook from https://nbviewer.org/github/openmc-dev/openmc-notebooks/blob/main/depletion.ipynb. When I run the calculations, however, I do not get anywhere near the same results as in the notebook. For me, the reactivity just jumps around the initial value within the uncertainties:

output

While in the example linked above, the reactivity clearly goes down with time. This means that there actually is no depletion going on in my case, while in the example some form of depletion is absolutely happening.

The only difference between my jupyter notebook and the one above is the part where the rectangular prism is defined, as this was changed in 0.14.0:

bound_box = openmc.model.RectangularPrism(1.24, 1.24, boundary_type="reflective")
root_cell = openmc.Cell(fill=pin_univ, region=-bound_box)

I have built OpenMC from source on a M1 MacBook Pro, using OpenMPI. The CMake command I used was

HDF5_ROOT=/opt/homebrew CXX=/opt/homebrew CC=/opt/homebrew/opt/llvm/bin/clang CXX=/opt/homebrew/opt/llvm/bin/clang++ LDFLAGS=-L/usr/local/lib cmake -DCMAKE_INSTALL_PREFIX=$HOME/openmc-mpi -DOPENMC_USE_MPI=ON -DOPENMC_USE_OPENMP=OFF ..

One weird thing is that even though i explicitly built OpenMC without OpenMP (I use MPI with OpenMPI instead, see command above), I get the following output when OpenMC is ran which seems to indicate that I am using OpenMP:

                 | 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 | fa2330103de61a864c958d1a7250f11e5dd91468
       Date/Time | 2024-01-29 11:44:49
   MPI Processes | 1
  OpenMP Threads | 10

 Reading settings XML file...
 Reading cross sections XML file...
 Reading materials XML file...
 Reading geometry XML file...

Does anyone have a clue why my depletion is not running? I did run the OpenMC test suite, and It seems like most of the tests involving depletion has failed. I use the endfb-vii.1-hdf5 cross section library from Official Data Libraries | OpenMC with the simplified depletion chain from Depletion Chains | OpenMC.

1 Like
2

I am getting the same issue when I run the depletion example jupyter notebook. The output plot is exactly the same, there is not any depletion occurring.

4

Interesting, so it seems like this is not an isolated incident. Which version of OpenMC are you running, and which cross section library/depletion chain are you using?

5

I am using version 14.0 of OpenMC, chain_casl_pwr.xml as depletion chain, endfb80 as cross section library. The plot I got is very similar:

image

6

One thing I’ll mention – there was recently a new version of SciPy released (1.12) and it caused a lot of our depletion tests to fail, and I have a sneaking suspicion that this may be the cause of the problems you all are seeing here. I haven’t had time to dig into the root cause yet and find a fix, but in the meantime I would suggest downgrading scipy to see if that helps (pip install 'scipy==1.11.4' or conda install 'scipy=1.11.4').

5 Likes
7

Okay now it seems to work. Results are much more similar to the ones obtained in the example, the difference could be due to the different cross section library, but at least there is depletion.

image

Thank you for your help!!!

8

This worked for me as well. Thanks a lot Paul! :slight_smile:

9

Can I ask what type of cross section library you used? Because now there is depletion but I feel like it is even too much compared to the results I should obtain and I do not think that difference could only be due to the cross section library.

1 Like
11

I get the same result as you - i.e. way too much depletion compared to the example linked in the original post. My graph looks very much like yours, and the reactivity goes down a lot more than the example.

I use ENDF/B-VII.1 as the nuclear data library and the Simplified Chain (Thermal Spectrum) from Depletion Chains | OpenMC. I also tested the ENDF/B-VII.1 Chain (Thermal Spectrum), but it still gives me way too much depletion.

output1

12

It really works, thank you!

13

This solution worked for me too. Thanks!
In my specific case the mpiexec runs of a adapted pincell depletion example just did not deplete (kinf looked constant, no pu239 fission rate increase)… it looked like it would redo the n0 step over and over again. After downgrading concentrations are changing as expected…
Cheers.