State nuclear power subsidy mechanism that requires emitting producers to purchase credits from nuclear producers at a price set by the market with a safety valve provision directly tied to the federal utility power auction mechanism is not preempted by the federal stature setting up the auction, since the state scheme doesn't price participants and non-participants in the federal auctions differently, and states have a right to regulate the utilities within their borders.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2018/D09-13/C:17-2433:J:Easterbrook:aut:T:fnOp:N:2218059:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.