SPOKANE, Wash. (AP) - The contractor that operates radioactive waste storage tanks at the Hanford Nuclear Reservation is proposing some reforms after dozens of workers reported becoming sick from chemical vapors associated with the tanks.

Washington River Protection Solutions this week asked unions to approve making nights and weekend work the standard shifts at the tank farms, an effort to reduce the number of workers who might be exposed to vapors.

The Hanford Atomic Metal Trades Council, a coalition of 15 unions on the former nuclear weapons production site, did not immediately respond to the reforms proposed Thursday in a letter from WRPS President Mark Lindholm.

Hanford is located near Richland and for decades made plutonium for nuclear weapons. The site is now engaged in cleaning up waste left over from that work.