Hi all. I’m trying to find the activation of a blanket configuration. But first I’m just trying to run a depletion/transmutation simulation to find the number of H3 atoms bred in the blanket over 2 hours.
I’m running the code in the fusion workshop docker container since I had trouble using Jupyter notebook on my laptop.
I’ve adapted John Shimwell’s code from task 14, which irradiates a sphere of silver, replacing the point source with a cylindrical source and the silver with my blanket configuration. Trouble is, the code tells me I’m only getting 1e-18 atoms after 2 hrs. The blanket should have a TBR of ~2 so I’d expect in the order of 1e15 atoms.
I can’t seem to work out why I’m getting such a low value. Any pointers would be very much appreciated. I’ve attached my script. Thanks
I’m not really familiar enough with the example or model to have an intuition here, but one thing to check would be the units on the values you’re using. In particular, are your timesteps really supposed to be 24 seconds? (the default unit for time is seconds). If you want to change the timestep units, you can do so with the timestep_units argument to PredictorIntegrator or any other integrator class.
I chose 24 seconds for the time step in that depletion example because that is the half life of Ag110 which is one of the main products in that example. But I see you have changed this to 600 seconds in your first example.
I’ve rerun you Untitled.py and also get low number of tritium atoms. I’ve also tried the script with newer chain file os.system('download_nndc_chain -r b8.0')
Not sure what is going on here but it reminds me of this PR that Paul put in a while ago which improved the traacking of light particles
However if you want to know the number of tritium atoms produced you can do this without the deplete methods. You might be better of building on the TBR example. This finds the tritium atoms produced per source neutron so you would just scale the TBR answer by the number of neutrons emitted per second (e.g. 1e24n/s) to find the total number of atoms produced.
Ah yes, now I remembered an issue that is relevant here. The default depletion chains do not include (n,t) reactions, which will obviously miss tritium production. If you wanted to include production of tritium from Li6, you could make the following change in your chain file:
Thanks guys, that helps. The reason I’m trying to find the number of atoms via depletion rather than just a TBR tally is that eventually I’m going to build up to finding all the radionuclides produced in the blanket after irradiation. This will be in order to find the activation so as to inform safety protocols of my design.
Also, @paulromano could I ask why the chain files are missing this data, and if they’ll be missing others which might affect my results? I’ve also noticed nuclides missing in cross section files. Is this an openmc specific problem, or something typical of neutronics codes? I’m still fairly new to MC simulations.
Our depletion system really came about from fission applications, and in those applications typically people don’t care about (n,t) reactions, so they were not included by default. It’s hard to say what else might be missing as it depends on the application, what materials you have present, etc…
This is really a fundamental limitation in the nuclear data libraries themselves, so all neutronics codes would be subject to the same limitations (e.g., if you are using ENDF/B-VII.1, there is no evaluation for C13).
