Delayed neutron fraction by isotope with IFP method

[OlivaresDarian]

Description

This modification allows the Iterated Fission Probability (IFP) method implemented by @JoffreyDorville to break down the effective delayed neutron fraction $\beta_{eff}$ tally by isotope. This extension of the IFP method enables deeper analyses in reactor physics.

In practice, the IFP tally stores certain ancestor information to compute adjoint-weighted tallies. This adaptation follows the same principle but also records the isotope that generated each delayed neutron. It slightly increases both memory use and computation time.

To use it, you simply need to define a list of nuclides in $\texttt{beta-num-tally.nuclides = [...]}$.

Fixes #3605

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[GuySten]

You should run clang format (version 15) on cpp source files for CI to successfully run.

[OlivaresDarian]

You should run clang format (version 15) on cpp source files for CI to successfully run.

Thanks @GuySten for your help

[GuySten]

I think you accidentally removed src/output.cpp and its header.
You should watch closely the "files changed" tab of this PR.
A change in 47 files seems too much for a feature of this scope.

[OlivaresDarian]

I think you accidentally removed src/output.cpp and its header. You should watch closely the "files changed" tab of this PR. A change in 47 files seems too much for a feature of this scope.

You're right. I already restored the output.* files. From the 47 changes, more than 27 are related to tests modifications because we added a new variable to the Particle object. The current version passes all tests in local.

[GuySten]

But you also added new files (I think by mistake).
Edit:
You can find them by the green plus in the files tab of this PR.

[GuySten]

Nice work, @OlivaresDarian!

[paulromano]

Putting a placeholder review on this as I'd like to take a look before we merge

[GuySten]

While trying to fix the current failing tests, I found a bug.
I will update this PR after #3676 is merged.

[JoffreyDorville]

Thanks @OlivaresDarian and @GuySten for this new feature! I would also like to take a look at it before we merge.

[GuySten]

I think a nice follow up feature will be to sample more frequently delayed neutrons with lower weight.
This should help the convergence of the kinetic parameters.

@JoffreyDorville, @OlivaresDarian, what do you think?

[OlivaresDarian]

Hi @GuySten, in commit fcd88d9 to ensure correct results we need to keep the lines that were removed here. Inside the if block, the upper bracket uses delayed_groups[0], while after the else block it uses delayed_groups[1]. This is because ancestor_event_nuclide[0] stores the isotope from which the neutron in delayed_groups[1] was born (the next generation).

Regarding your proposal, I need to investigate a bit more, but it should be possible.

[GuySten]

My bad, I thought that was a typo.
I fixed it in the last commit.

[GuySten]

I added a suggestion to prevent code repetition.