Who played Karen Silkwood in the movie "Silkwood"?

This is a 1980 movie. Karen Silkwood, an employee of the Kerr-McGee plutonium processing plant, was killed in a car crash on her way to deliver important documents to a newspaper reporter in 1974. Silkwood was a union activist concerned about health and safety issues at the plant, and her death at age twenty-eight was considered by many to be highly suspicious.