Explicit Fission Product Modeling #1022

jakehader · 2022-12-13T02:14:44Z

Description

Updates to the fission product model and nuclides to allow for users to model fission products explicitly based on which cross section libraries/software will be used to generate multi-group cross sections.

This implements a method that looks at the existing nuclides defined in the blueprints nuclideFlags and amends this to include all nuclides within regions that are determined to be Depletable based on which nuclides the user sets as being burn=True. This will not check that the user defines the correct depletable nuclides for this determination, but will only add all the nuclides that are missing to the depletable regions. This is reasonable since the behavior is similar to how it is when the user selects another fission product model option.

This change also introduces a mechanism to remove gaseous fission products from the core that can be called upon by a fuel performance or other plugin code. The previous implementation of this modified the fission yields as a surrogate for this removal, but upon further review it is better to update the number densities within the blocks directly compared to modifying the fission yields. This is currently left not implemented.

Finally, the fuel performance parameters were updated to add setters on the gasReleaseFraction and the bondRemoved. The description suggested that these values should only range from [0, 1] and any value outside of this range is not valid. The setters now check for this and raise a ValueError if these conditions are not met.

Checklist

This PR has only one purpose or idea.
Tests have been added/updated to verify that the new/changed code works.

The code style follows good practices.
The commit message(s) follow good practices.

The release notes (location doc/release/0.X.rst) are up-to-date with any bug fixes or new features.
The documentation is still up-to-date in the doc folder.
The dependencies are still up-to-date in setup.py.

to model fission products explicitly based on which cross section libraries/software will be used to generate multi-group cross sections. This implements a method that looks at the existing nuclides defined in the blueprints `nuclideFlags` and amends this to include all nuclides within regions that are determined to be `Depletable` based on which nuclides the user sets as being `burn=True`. This will not check that the user defines the correct depletable nuclides for this determination, but will only add all the nuclides that are missing to the depletable regions. This is reasonable since the behavior is similar to how it is when the user selects another fission product model option. This change also introduces a mechanism to remove gaseous fission products from the core that can be called upon by a fuel performance or other plugin code. The previous implementation of this modified the fission yields as a surrogate for this removal, but upon further review it is better to update the number densities within the blocks directly compared to modifying the fission yields. By modifying the number densities directly we are explicitly handling both the microscope and macroscopic cross section effects in lattice physics calculations and in system eigenvalue/flux solutions. Finally, the fuel performance parameters were updated to add setters on the `gasReleaseFraction` and the `bondRemoved`. The description suggested that these values should only range from [0, 1] and any value outside of this range is not valid. The setters now check for this and raise a ValueError if these conditions are not met.

jakehader · 2022-12-14T01:54:26Z

This PR depends on #998 and is basically just pulling out commits from there to isolate changes with added unit tests. This is functional for our internal needs

keckler · 2022-12-19T16:57:49Z

@jakehader

Can I make the request that we split this into two separate PRs: (1) for the explicit FP modeling and (2) for the FPs to be removed from the fuel.

It appears to me that these two capabilities are separable, and it would make it much easier during our internal integration testing in the process of pulling this into our app.

If you think this is possible, let me know if I can be any help.

jakehader · 2022-12-20T01:12:27Z

@jakehader

Can I make the request that we split this into two separate PRs: (1) for the explicit FP modeling and (2) for the FPs to be removed from the fuel.

It appears to me that these two capabilities are separable, and it would make it much easier during our internal integration testing in the process of pulling this into our app.

If you think this is possible, let me know if I can be any help.

I will consider it since these are two separate features.

Edit: I decided that it doesn't make sense to decouple these additions since the code changes for just adding the explicitFissionProducts setting without further updates throughout would be a trivial change and the next PR would be just as large.

# Conflicts: # armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py # armi/physics/neutronics/fissionProductModel/tests/test_lumpedFissionProduct.py # armi/resources/referenceFissionProducts.dat # doc/release/0.2.rst

…el treatment with fission gas removal implemented

armi/cases/case.py

armi/operators/settingsValidation.py

armi/physics/neutronics/crossSectionGroupManager.py

armi/physics/neutronics/fissionProductModel/fissionProductModel.py

armi/physics/neutronics/fissionProductModel/tests/test_lumpedFissionProduct.py

armi/reactor/blueprints/__init__.py

armi/reactor/tests/test_assemblies.py

armi/settings/fwSettings/globalSettings.py

armi/physics/neutronics/fissionProductModel/tests/test_lumpedFissionProduct.py

armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py

armi/resources/referenceFissionProducts.dat

armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py

# Conflicts: # doc/release/0.2.rst

armi/physics/neutronics/fissionProductModel/fissionProductModel.py

# Conflicts: # doc/release/0.2.rst

…the nucDirectory to get the displacement energies from the element symbol rather than the element object

after some more testing was done.

opotowsky

I didn't finish the code review yet but I figured I'd leave feedback tonight that you can work on first thing in the AM while I/we finish up our reviews.

There is a significant coverage drop despite all of the testing work you did. There's two methods/functions that are newly uncovered, and a new one that needs to get tested. Since I can't comment on code that's not changed....well, you'll see what I did...

armi/reactor/blueprints/__init__.py

armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py

armi/physics/neutronics/crossSectionGroupManager.py

keckler

Okay, here's some comments for you at this point.

I still have to review 2 files worth of tests and referenceFissionProducts.dat. So probably any further comments will be minor.

I have a few concerns, particularly related to the removal of fission gases. Those are captured in comments throughout.

I also am worried that the changed handling of the gaseous fission products might surprise non-TP users of ARMI if all of the sudden their block number densities are different when they update their framework.

I do not disagree that this change should be made, but I think it is likely to
cause some confusion down the line. That is really a product of having a bad
fission gas model in the first place, but still. Probably nothing can be done about that if we are intent on fixing the model.

armi/operators/settingsValidation.py

armi/physics/fuelPerformance/parameters.py

armi/physics/neutronics/fissionProductModel/fissionProductModelSettings.py

armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py

armi/physics/neutronics/fissionProductModel/fissionProductModel.py

armi/physics/neutronics/fissionProductModel/lumpedFissionProduct.py

gas removal code because it wasn't working correctly.

john-science · 2022-12-27T18:08:58Z

It's a big PR.

I see changes to blueprints and settings. Are these backwards compatible? I just want to make sure we aren't breaking all of the current, really important, settings/blueprints YAML files we have lying around.

armi/settings/caseSettings.py

jakehader · 2022-12-27T20:01:31Z

It's a big PR.

I see changes to blueprints and settings. Are these backwards compatible? I just want to make sure we aren't breaking all of the current, really important, settings/blueprints YAML files we have lying around.

@john-science - existing blueprints and settings are not impacted by this change. This change only impacts modeling with fpModel is set to explicitFissionProducts, but the default is still to use lumped fission products.

… coverage.

…ission product number densities rather than assuming that the first LFP in the collection contains the entire set of nuclides required.

keckler

@jakehader Thank you for all of your work on this. I think this puts us in a good place to be able to model the explicit fission products!

keckler · 2022-12-27T22:51:25Z

armi/reactor/blueprints/__init__.py

+from armi.physics.neutronics.fissionProductModel import lumpedFissionProduct
+from armi.nucDirectory import elements


I'm pretty certain these added imports are not used.

keckler · 2022-12-27T23:38:02Z

I wanted to update this thread with the current state of what all was changed and/or added with this PR, since the target changed a couple times.

This PR enables the modeling of explicit fission products, as compared to previously being limited to using lumped fission products at best.

This PR does NOT implement the correct removal of fission gases from blocks. However, it does remove the previous implementation, which was modifying the yields of fission products to artificially exclude some fraction of gaseous fission products. Now, fission products are left in place, and a warning is issued if a user tries to remove them via the removeFissionGasesFromBlocks() method. If one wants to remove fission gases, they should overwrite that method from within their own plugin.

That is my understanding, but please feel free to chime in with more details if I am wrong.

opotowsky · 2022-12-28T00:19:22Z

Thanks so much for this enormous lift @jakehader !

jakehader added bug Something is wrong: Highest Priority enhancement New feature or request labels Dec 13, 2022

jakehader requested a review from onufer December 13, 2022 02:14

WIP - adding testing

05f46aa

Working on testing.

aa2c0ec

jakehader added 2 commits December 20, 2022 06:19

Finish fission product model updates for explicit fission product mod…

545f002

…el treatment with fission gas removal implemented

jakehader requested review from keckler, albeanth, opotowsky and john-science and removed request for onufer December 21, 2022 02:18