4692 bug avoid eta cd dimensionless hcd primary nan when p hcd primary injected mw 0

[grmtrkngtn]

Description

Issue

PROCESS calculates three current-drive efficiency quantities for the primary H&CD system:

• eta_cd_hcd_primary: absolute current-drive efficiency in A/W.
• eta_cd_norm_hcd_primary: normalised current-drive efficiency, which scales eta_cd_hcd_primary by plasma density and major radius.
• eta_cd_dimensionless_hcd_primary: dimensionless current-drive efficiency, which additionally normalises the efficiency using the plasma electron temperature.

Currently, eta_cd_dimensionless_hcd_primary is calculated using:

c_hcd_primary_driven / p_hcd_primary_injected_mw

However, when no auxiliary current drive is required, PROCESS can produce:

p_hcd_primary_injected_mw = 0
c_hcd_primary_driven = 0

This causes 0 / 0, giving:

eta_cd_dimensionless_hcd_primary = NaN

eta_cd_hcd_primary is already calculated from the selected i_hcd_primary model, so eta_cd_dimensionless_hcd_primary should use eta_cd_hcd_primary directly rather than recalculating the same efficiency from realised current and power.

Proposed fix

Refactor calculate_dimensionless_current_drive_efficiency() to take eta_cd_hcd instead of c_hcd_driven and p_hcd_injected

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.28%. Comparing base (db9f377) to head (e011e37).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4694   +/-   ##
=======================================
  Coverage   50.28%   50.28%           
=======================================
  Files         181      181           
  Lines       30532    30532           
=======================================
  Hits        15353    15353           
  Misses      15179    15179           

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