Roger Breton wrote:
Operationalize = put into some operation or how do you mesure it.
OK, the proper way to do this would be to compare the spectra of the two papers, with different illuminants. You want the spectra to match in any case, and comparing using two illuminants with different levels of UV will check how they track with regard to UV.
In practical terms, I don't know of any instruments that have a switchable UV source, but you can get close with the Spectrolino, checking the spectra using the default D50, and with the simulated D65 using the filter.
Even without the ability to check under two illuminants, it's pretty easy to examine the paper spectra by eye, and get a rough idea how similar the FWA level is. FWA sucks the deep blue out of the reflectance (below 400nm), and returns it as a peak at a longer wavelength (peak about 430nm). Plot a bunch of different sorts of papers, from the best proofing stock to office copy paper, and you'll get a feel for it.