Americans who grew up with nightmares of nuclear explosions should get ready for some terrifying flashbacks, for the Trump administration and its Republican enablers in Congress seem to be preparing to revive U.S. nuclear weapons tests, which were halted in 1992.  This action, designed to intimidate U.S. rivals, would ignore treaty commitments and world opinion, encourage other nations to resume or begin nuclear testing, and pollute the environment with deadly radioactivity.