Fixing HT9 density - to match reference

[john-science]

Description

For some reason, the density of HT9 did not match the listed reference density: https://www.osti.gov/biblio/1506477-metallic-fuels-handbook (page 194/210)

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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.

[jakehader]

Thanks @john-science! I'm not sure the impact of downstream applications so maybe we can hold off on merging until we check this?

[john-science]

Thanks @john-science! I'm not sure the impact of downstream applications so maybe we can hold off on merging until we check this?

Agreed. Yeah, that's a bit of a concern.

On the one hand, the downstream projects would be slightly wrong, and this would be an improvement. On the other hand, I don't like surprising people.

[john-science]

Okay, we are ready to merge this into ARMI.

It appears we have solved our downstream concerns.