"KURCHATOV, Kazakhstan — Twenty years after the Soviet Union collapsed and tens of thousands of soldiers abandoned their posts at this remote site in northeastern Kazakhstan, the footprints of another great power — the United States — are increasingly visible.
The United States Defense Department has paid for aerial drones to spot intruders, and for motion detectors that signal when a person, or a horse or a car, crosses into restricted territory. The classified project aims to keep terrorists away from what the Soviets left behind in patches of earth and a warren of tunnels that they used for atomic testing: among other things, plutonium and highly enriched uranium that Western scientists fear could be used to build an improvised nuclear device.
Protecting this material has meant teasing out nuclear secrets that have been kept for decades. Russia is warily sharing archival material about Soviet-era tests, and the United States is paying to remove or secure weapons-grade material. Kazakhstan is providing the labor, but because it is not a nuclear power, its officials are forbidden from learning exactly what it is that they are guarding."