State lawmakers take another step this week toward repealing Minnesota's ban on construction of nuclear power plants.  The Senate and House are expected to set up a conference committee to work out differences between their bills.  House DFL Minority Leader Paul Thissen hopes that Governor Dayton's wishes will be accomodated.  The governor wants protections for utility ratepayers.  Some warn that those customers will be forced to pick up too much of high up-front costs if nuclear plants are built.  Backers of the bill say that to encourage business growth, Minnesota needs reliable and affordable electricity.