Hi Matthew.
You can have the same AAA for both portals.
AAA rules can be also location based.
with the above the logic can be:
If location A then portal A and AAArules.
If location B then portal B and AAArules.
Your AAArules:
if location A then Radius A
If location B then Radius B
Regards, hope it helps
Regards
Zdeněk Pala