On October 11, 1961, the world's first underground nuclear explosion was conducted at the Semipalatinsk Test Site (STS). It began a new phase of experiments carried out in the area during the Soviet era.
The Semipalatinsk test site was brought into operation under a secret decree released by the Council of the People's Commissars in 1948. It was founded as a primary testing venue for the Soviet Union's first nuclear weapons. The area encompassed 18,500 square kilometers and was situated on the bank of the Irtysh River, in the northeast of Kazakhstan, 130 km from the city of Semipalatinsk.
Ground and atmospheric tests of nuclear weapons were conducted at the site until 1963 by the Soviet military organizations for technical and scientific studies. After the Soviet Union, US and Britain signed a nuclear ban treaty in 1963 (Limited Test Ban Treaty or LTBT), banning nuclear tests in the oceans, in the atmosphere, and in outer space, the USSR began carrying out underground explosions in compliance with the terms of the LTBT.
In the forty years of operation (first nuclear explosion was conducted in 1949) 456 ground, underground as well as atmospheric nuclear tests took place at the site. In addition, almost 600 thermonuclear devices were tested, and several tens of hydrodynamic and hydro-nuclear devices.
The most unique thing about STS is that it is the only test site in the world on the territory of which people continued to live - despite the large radioactive contamination - as well as growing crops and collecting scrap metal.
The total power of all nuclear bombs exploded at the site is 2,500 times bigger than the power of the one bomb dropped on Hiroshima. Examination of the zone conducted by the Academy of Science concluded that this area has a high radioactive contamination and diagnosed people and animals living in the vicinity of the test site with pathology caused by radiation effects. In addition, the radioactive clouds from ground and atmospheric explosions, as well as gases from underground tests, spread beyond the bounds of the site by hundreds of kilometers.
The population was exposed to radioactive irradiation, which in the course of time entails illnesses, untimely deaths, and genetic damage. Statistics regarding all effects on the people residing in the area, gathered by the Soviet scientists in the course of nuclear tests, remain classified.
The decree to close the Semipalatinsk test site was released by the President of Kazakhstan, Nursultan Nazarbayev in 1991. Today, the test site no longer exists; only a monument in memory of its victims stands today in Semipalatinsk.