CRS report via FAS – Comprehensive Nuclear-Test-Ban Treaty: Background and Current Developments, Mary Beth D. Nikitin, Specialist in Nonproliferation. September 1, 2016.

“Nuclear testing has a long history, beginning in 1945. The Natural Resources Defense Council states that the United States conducted 1,030 nuclear tests, the Soviet Union 715, the United Kingdom 45, France 210, and China 45. (Of the U.K. tests, 24 were held jointly with the United States and are not included in the foregoing U.S. total.) Congress passed and President George H.W. Bush signed legislation in 1992 that established a unilateral moratorium on U.S. nuclear testing. Russia claims it has not tested since 1990. In 1998, India and Pakistan announced several nuclear tests. Each declared a test moratorium; neither has signed the CTBT. North Korea announced that it conducted nuclear tests in 2006 , 2009, 2013 , and 2016. Since 1997, the United States has held 28 “subcritical experiments” at the Nevada National Security Site , most recently in August 2014, to study how plutonium behaves under pressures generated by explosives. It asserts these experiments do not violate the CTBT because they cannot produce a self – sustaining chain reaction. Russia reportedly held some such experiments since 1998…”