Newly Unbound, Trump Weighs More Nuclear Arms and Underground Tests

It remains to be seen whether the three big nuclear powers are headed into a new arms race, or whether President Trump is trying to spur negotiations on a new accord now that a last Cold War treaty has expired.An underground atomic test at the Nevada Test Site near Yucca Flats in 1955. The last U.S. explosive test of a nuclear weapon was in 1992.