`emult` is overwritten with hard-coded value in ccfe_hcpb regardless of input value

[jonmaddock]

In GitLab by @pc6783 on Mar 3, 2022, 15:12

emult is a user-configurable input, the energy multiplication due to neutron reactions in the blanket and shield. However, regardless of the value that the user sets, emult is set to 1.269 in the subroutine ccfe_hcpb. This overwrites the user's value.

emult may have a value differing from this in reactor designs that the user is interested in. For example, the Menard et al. 2016 pilot plant, in which the lack of blanket on the inboard side means those neutrons don't exhibit energy multiplication. In this case, emult is 1.1.

I plan to just get rid of that offending line.

@mkovari @stuartmuldrew do you have any insight? Thanks

[jonmaddock]

In GitLab by @mkovari on Mar 3, 2022, 15:21

The CCFE HCPB blanket model (without TBR calculation) was based on a particular family of blanket geometries, so it is hazardous to use it for a very different geometry.

[jonmaddock]

In GitLab by @pc6783 on Mar 3, 2022, 15:31

Do you recommend another blanket model for spherical tokamaks? I inferred (perhaps incorrectly) CCFE HCPB is the most relevant to itart==1 cases because it has centrepost subroutines such as st_cp_angle_fraction, st_tf_centrepost_fast_neut_flux, and st_centrepost_nuclear_heating, and logic which considers only the outer legs when using the conventional model.

[jonmaddock]

In GitLab by @mkovari on Mar 4, 2022, 14:05

I have a nasty feeling that it may have been hijacked for use in STEP by adding these ST-relevant routines.

But no, I am not sure I can recommend anything better.

[jonmaddock]

In GitLab by @pc6783 on Mar 4, 2022, 15:17

Based on your comment, it sounds like this is the "least wrong" model for HCPB blankets in a spherical tokamak. In light of this, my current plan is to continue as planned with changing the offending emult line, to make it that small amount "less wrong."