The United States is wiring Ukraine with sensors that can detect bursts of radiation from a nuclear weapon or a dirty bomb and can confirm the identity of the attacker.
In part, the goal is to make sure that if Russia detonates a radioactive weapon on Ukrainian soil, its atomic signature and Moscow’s culpability could be verified.
Ever since Russia invaded Ukraine 14 months ago, experts have worried about whether President Vladimir Putin of Russia would use nuclear arms in combat for the first time since the American bombings of Hiroshima and Nagasaki in 1945. The preparations, mentioned last month in a U.S. House of Representatives hearing and detailed Wednesday by the National Nuclear Security Administration, a federal agency that is part of the Energy Department, seem to constitute the hardest evidence to date that Washington is taking concrete steps to prepare for the worst possible outcomes of the invasion of Ukraine, Europe’s second-largest nation.