The Semipalansk polygonlocated in a remote area of the eastern steppes of Kazakhstan, represented one of the main ones Nuclear experimentation centers of the Soviet Union during the period of intense rivalry in the armament race with the United States. Between the 1949 and 1989on the site they were performed overall 456 atomic testsunderstanding both atmospheric detonations and underground and it is estimated that approximately 220 thousand local residents have been exposed to extremely high levels of ionizing radiation. The area was subject to rigorous security measures and access to information relating to experimentation activities was limited exclusively to a small number of high -ranking officials of the USSR. Only with the conclusion of the Cold War and the consequent disposal and closing of most nuclear sites, details on the operations conducted were made public, arousing strong indignation between the local population.
Development of the Soviet nuclear program
The Soviet nuclear program was officially started in 1941 under the scientific direction of the nuclear physicist Igor Vasilyevich Kurchatov and the supervision of Stalin’s closest political collaborators. Until 1945, the project benefited from limited funding; However, following the launch of the US atomic bombs On Hiroshima and Nagasaki, Soviet leadership ordered a substantial acceleration in the development of the nuclear order. This decision determined a significant enhancement of research infrastructure, military reactors and the scientific contingent engaged, with the aim of optimizing realization times. In this context, the oriental kazake steppes were designated as suitable site For the experimentation of Soviet atomic weapons and the “was establishedNuclear Polygon of Semipalansk“(also known as”Semipalansk-21“), which over the years became one of the places with The highest levels of radioactive contamination of the time.
The area of the semipalansk polygon, located in the north-east of Kazakhstan, south of the Irtysh river valley, extended for about 18 thousand km2 and was selected on the basis oferroneous assumption that the surrounding steppes were uninhabited. The site was conceived as a complex dedicated to the detection and measurement of the parameters of nuclear explosions in experimental conditions real environmental. At the center of the area intended for the execution of the tests there is still a crater known as “The epicenter“, the place where numerous experiments were conducted, including the First historian of 29 August 1949 (“First Lighting“). From that day until 1989, a total of 456 nuclear explosions were performed in the polygon, with a total detonation power Fourteenth century higher That of the Hiroshima bomb in the period 1949-1963 alone. 116 tests were carried out outdoors until 1962year in which the United Nations General Assembly (UN) introduced the prohibition atmospheric experimentation. Subsequently, following the ratification of the partial ban on nuclear tests (PTBT) deL 1963the Soviet authorities performed the remaining 340 tests exclusively in underground structures and in tunnel specifically excavated.
The first underground nuclear test the January 15, 1965 In the vicinity of the ancient riverbed of river Chaganstrategically selected location so that the edge of the generated crater could act as a natural dam to contain the waters during the spring peak of the river course. The detonation determined the movement of beyond 200 million tons of earthy material, generating a cavity with a diameter of 408 meters and a depth of 100 meters. An artificial basin was formed within this depression, which took the name of Chagan lake or Balapan lake.
The closure of the polygon
On August 29, 1991 The atomic experimentation site was officially abandonedat the same time as the fall of the Soviet Union and the dissemination of the harmful effects of exposure to radiation on the local population and on the surrounding environment. On that occasion, the president of the newly formed Republic of Kazakhstan Nursultan nazarbayevannounced theabandonment of the development and exploitation policy of nuclear energy for war purposes. Between 1995 and 2012 operations were conducted reclamationwith a total investment of about 150 million dollarsduring which they were sealed beyond 180 tunnels And 13 wells used during the various tests and adopted safety measures for a significant amount of residual plutonium in the area.
The scientific studies carried out after the disposal of the site highlighted a significant Radionuclidi dispersion in the surrounding environmental matrices, with consequent contamination of an estimated area in 300 thousand km2an area comparable with that of Germany. The epidemiological analysis revealed a direct health impact on about 220 thousand residents in the areas surrounding the site, with a statistically significant increase inincidence of neoplasms, In particular, malignant tumors and thyroid pathologies, attributable to prolonged exposure to ionizing radiation. Further investigations conducted on subjects of pediatric and adolescence have underlined genetic alterations in specifics DNA sequences involved in gametogenesis, that is, in the processes of germ cells.
The current state of conservation of the site
Currently the polygon area hosts theKazakh institute for radiological security and ecologyas well as three of the four nuclear research reactors present on the national territory, two workshops with cyclotron and two particles accelerators. The main activities of the research complex include the monitoring and stabilization of the radioecological conditions of the area, the control of ionizing radiation sources (IRS), the collection, treatment and safe disposal of radioactive waste. In addition, the area is affected by a phenomenon of specialized tourismwith local operators who organize paid guided tours within abandoned structures. At the same time, they are recorded illegal activities aimed at the unauthorized extraction of precious metals present in the subsoil, with consequent environmental and safety risks.
