Strontium-90 Contamination Within the Semipalatinsk Nuclear Test Site: Results of Semirad1 and Semirad2 Projects – Contamination Levels And Projected Doses to Local Populations

Analysis of strontium-90 in soils showed that most of the SEMIRAD1 and SEMIRAD2 project areas were little contaminated with this radionuclide indicating that the extensive testing of nuclear devices at the STS (including more than 100 groundlevel, aerial and crater-producing explosions) resulted in little dispersed local contamination by fission products, including strontium-90. However, local strontium-90 contamination produced by the Telkem, crater-producing explosions within the SEMIRAD1 study area was evident at distances less that about 3 km from the explosion sites. Within the craters soil strontium-90 concentrations reached 1 kBq kg^–1. Around the craters strontium-90 was more widely dispersed than fuel-associated radionuclides and evidence exists to suggest that it is much more mobile within the environment. Within the SEMIRAD1 study area strontium-90 levels were also elevated below the path of the fallout plume produced by the testing of the Soviet Union’s first H-bomb in 1953. Radiation doses to residents of the SEMIRAD1 study area were calculated using a modified ECOSYS model. These indicated that strontium-90 was a major contributor to dose in the more contaminated regions around Telkem and close to the village of Sarzhal. Annual doses to adult males living close to Telkem were assessed to currently be about 7 mSv, but these were predicted to fall in line with the physical half-life (28.64 years) of strontium- 90. Localised hotspots that are significantly contaminated with strontium-90 are to be found within Technical Area 4a, which straddles the southern boundary of the SEMIRAD2 study area. About 35 areas of contamination produced by the testing of radiation dispersion devices have been identified. They are considered hazardous since they are unmarked and have been grazed by animals from local farms. They may also present a terrorism hazard. Calculations made using the ICRP biokinetic model for strontium suggest that, under conditions of chronic ingestion, radiation doses to farmers and their families could reach about 4 mSvy^–1.