ALTHOUGH NORTHEASTERN Kazakhstan’s Semipalatinsk, the world’s largest and most frequently used nuclear test site, has been closed since 1991 and will soon be sealed, its legacy will linger for years to come. Set up in 1948, the test site encompasses 18,000 square meters of territory and has experienced about 500 nuclear explosions over the past 30 years, including a total of 160 atmospheric and above-ground tests.1It was here that the Soviet Union exploded its first atom bomb in 1949 and detonated its first hydrogen bomb in 1953. Above-ground tests were discontinued in 1963 after the Soviet Union ratified the Partial Test Ban Treaty. However, the lack of adequate safeguards resulted in roughly one out of every three underground explosions venting at surface level.
