Recommendation to rename the puFrac parameter to puHMFrac and add block parameter puWeightFrac

[sammiller11235]

It can be seen below that the block parameter definition that puFrac represents the fraction of "heavy metal" which is Plutonium. For certain fuel systems, the plutonium in the fuel is typically defined as the total weight fraction of Plutonium in the fuel mass (e.g., 100 grams of U-19Pu-10Zr has 19g of Pu, 10g of Zr, and 71g of U). This parameter has been misinterpreted to mean the Pu total weight fraction, and renaming would resolve this ambiguity.

armi/armi/reactor/blockParameters.py

Lines 798 to 803 in f6ee150

	pb.defParam(
	"puFrac",
	units=units.UNITLESS,
	description="Current Pu number density relative to HM at BOL",
	location=ParamLocation.AVERAGE,
	)

[onufer]

if we make the second param, we should probably call it puFuelWeightFrac

[john-science]

Renaming parameters is easy enough, my only caution is that we are in the middle of a particularly busy release right now.

Having said that, my request is that if we change the name of this parameter, we don't use the name puFrac for another other parameters. We've had some real tricky problems in the past when people think they are using one parameter, but it's become something totally different. If you follow me.

I'll leave it up to you two, if you think this is high enough priority to push through now, or if we wait 2-3 weeks.