Summary of changes

This PR fixes material temperatures being hardcoded to 900K.

Specifcially, this PR:

• Adds a new attribute of DepcodeSerpent, fix_dict, that tracks the values of the fix card for each material
• Passes these values to the iteration material file instead of overwriting/dropping them

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Required for Merging

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• My change is a source code change
  • I have added/modified tests to cover my changes
  • I have explained why my change does not require new/modified tests
• My change is a user-facing change
  • I have recorded my changes in the changelog for the upcoming release
• My change is exclusively related to the repository (e.g. GitHub actions workflows, PR/issue templates, etc.)
  • I have verified or justified that my change will work as intended.
• All new and existing tests passed.
  • CI tests pass
  • Local tests pass (including Serpent2 integration tests)

Associated Issues and PRs

• Issue: closes [Bug]: Fuel Material Temperature Hardcoded (maybe?) in saltproc_mat #146

Associated Developers

• Dev: @

Checklist for Reviewers

Reviewers should use this link to get to the
Review Checklist before they begin their review.