Nozzles and Support Plate approximation

[liangjg]

I wonder if the water density is correct in the nozzle (source 63) because it doesn't take into account the volume of the instrument rod for the lower part and the steel rods above the rods in the upper part

also above the burnable absorber rods

I found https://www.nrc.gov/docs/ML0335/ML033530020.pdf for ref 15 used in source 64. Is it correct?
reading Table 2-3 of [15] it seems that region 1 an 6 have steel inside (respectively 0.1770 and 0.1720). Why is there only water in these parts in figs 32-35?

also, lower nozzle seems to be more or less region 5 of Table 2-3 of [15] (according to elevation), for which steel fraction is 0.1439 and not 0.1720. Is 0.1720 really expected in source 64?

sorry for those questions. if they are not appropriate, just let me know.

Thanks for your questions about the compositions/densities in the nozzle/support plate region. The approximations used may be improved by accounting for the volume of the extra rod, differentiating the nozzle and support plate... But I'm not sure how much they are affecting the simulation results. Have you done any testing before?
Anyway, I'll leave this as another issue. Please go ahead if you are interested to make the changes to the openmc model, do some tests, and submit a PR.

Originally posted by @liangjg in #4 (comment)

[rolandlenain]

I haven't tested anything yet.