The exact content of the vapors is unknown because the contents of the nuclear waste tanks are not completely known. Workers for years have complained that chemical vapors from the tanks have made them ill.More than 50 Hanford workers in recent months have sought medical examinations for possible exposure to chemical vapors. Officials for Washington River Protection Solutions, the private contractor that operates the tank farms for the U.S.Department of Energy, confirmed the work stoppage at the double-walled tank farms. The Hanford Atomic Metal Trades Council issued a "stop work" order at the double-walled tanks that contain dangerous wastes from the past production of plutonium for nuclear weapons. Tank farm work involving the movement of nuclear waste is suspected in the release of the non-radioactive chemical vapors, which are invisible.

Source: New Zealand Herald July 11, 2016 22:52 UTC