Depletion/Burnup not implementing into example problem

User Support
1

Hello Everyone!

I have been playing around with the example for burnup and evolving TBR calculations.

What I am finding is that I am seeing suitable (n,t) reactions for Li6 however my Li6 inventory remains the same throughout all timesteps and my TBR values fluctuate to the same value instead of decreasing.

Do I need to manually update the inventory through reaction rates or am I thinking about this wrong?

2

Hi Luis Garcia, welcome to the openmc community.
Just to make sure, have you set up your lithium material to be a depletable material? Something like this your_Li_mat.depletable = True

Also, I haven’t done this kind of TBR calculation before, but maybe it also came out from the depletion chain data for Li6 that only takes into account the (n,gamma) and (n,p), without (n,t) reaction in thermal chain endf80. You might want to modify the depletion chain if you think it came from this. Maybe @Shimwell wants to give some comments for this (n,t) reaction?

  <nuclide name="Li6" reactions="2">
    <reaction type="(n,gamma)" Q="7250600.0" target="Li7"/>
    <reaction type="(n,p)" Q="-2727300.0" target="He6"/>
  </nuclide>
3

Hi @wahidluthfi

Yes, I have my material set to depletable. I am currently trying to run the example from the neutronics workshop here

I think I am using the same/correct chain file as the example, it seems to have the necessary reactions:

image

I am finding that my TBR is staying about the same and my Li6 atom concentration is also constant at each timestep where I am expecting it to drop off.

4

I also noticed that in that notebook, there is a note that you have to change your `settings.particles’ to 50,000 to show the decreasing TBR. Have you checked that? I think it might affect your reaction rate uncertainty.
“Access the TBR tally at each depletion time step, to observe the TBR decreasing as a function of time the simulation needs to be run with around 50000 particles”

5

Hi @wahidluthfi

I have tested the example with 50,000 and 500,000 and still not seeing any changes in TBR and Li6 amount

6

Hello,

I think my problem was I was using an outdated environment. I was running OpenMC 0.14 and switching to OpenMC 0.15 allowed my simulation to track Lithium inventory and TBR values decreased as expected.

Thank you for helping me debug my problem @wahidluthfi !

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