Chlorine-36 in soil collected at Semipalatinsk Nuclear Test Site

Concentration of 36Cl was determined in soil sample collected at the former Soviet Union (FSU) Semipalatinsk Nuclear Test Site (SNTS). The radiochemical separation procedure has been developed for chlorine isolation from soil matrix and interfering radionuclides, and 36Cl determination was performed by liquid scintillation counting (LSC) and projectile X-ray accelerator mass spectrometry (PX-AMS) techniques. The concentration of 36Cl was determined as (1.5±0.7) mBq/g by LSC. 36Cl/Cl atom ratio measured by PX-AMS at Kyushu University Tandem Laboratory (KUTL) was found to be (5.0±1.6) x 10-10 and the activity of 36Cl was calculated as (2.0±0.6) mBq/g. The separation of competing atomic isobars of 36S and 36Cl was satisfactory achieved by projectile X-ray detection technique. Currently developed at the KUTL 36Cl-PX-AMX system can be applied for 36Cl analysis at 36Cl/Cl atom ratio level of 10-11. (author)