The federal government is asking a court to block a new Washington state law making it easier for workers at the Hanford Nuclear Reservation to secure compensation for workplace injuries or illnesses.

The state law (SHB 1723) was approved in 2017 amid concerns about worker exposures since 2014 to vapors from tanks containing radioactive and hazardous chemical wastes. Workers at the facility are pushing to dispose of the materials as part of a multibillion-dollar project overseen by the Department of...