375 



3. Individual Dosimetry 



In order to ensure the safety of personnel during surface operations in the course 

 of radiometric investigations and while sampling plants, soil and water at many sites of 

 radioactive contamination, "Regulations on Radiation Safety During Investigations" of 

 June 22, 1990 (Appendix 6) were developed and approved. The Radiation Safety Service 

 of TsPSO ordered 25 individual photodosimeters (IFKU-1) from the Experimental 

 Procedural Unit of Nuclear Geophysics, which has the right to test dosimeters granted by 

 the Far East Center of Standardization and Metrology (678500, town of Batagay, 

 Verkhoyansk Rayon, Yakut SSR, uL Oktyabrskaya, 6 .., illegible...). These dosimeters 

 were distributed in the following manner: 11 instnmients for operations in the area of 

 the town of Taas-Yuryakh, 12 for operations in the area of the town of Udachny, and 

 two reserve dosimeters (No. 4005 and No. 4016) for determining background values were 

 not used (Appendix 7). 



CONCLUSION 



According to information we have gathered, nine underground nuclear explosions 

 were conducted in the Mirny Rayon of the Yakut-Sakha SSR for research and economic 

 purposes in the vicinity of the following population centers: town of Udachny, one 

 explosion, (a site called "Kristall", 1974), town of Aykhal (one, "Kraton-3", 1978), town of 

 Taas-Yuiyakh (seven, "Oka", shaft No. 42, 1976, "Vyatka", shaft No. 43, 1978, "Sheksna", 

 shaft No. 47, 1979), "Neva-1", shaft No. 66, 1983, "Neva-2,3", shafts Nos. 61, 68, and 101, 

 1987). 



All nine explosion shafts and adjacent areas were studied, although over limited 

 areas, in 1990 by airborne gamma-spectrometric survey. In two cases, at the sites 

 "Kristall" and "Kraton-3", area radioactive contamination was foimd. Surface operations 

 were carried out at 4 sites: detafled operations at the site "Kraton-3" and prospecting at 

 the sites "Kristall," "Sheksna," and "Neva-3". Radioactive contamination was recorded at 

 three sites, "Neva-3" being the exception. The operations employed data fixjm an 

 advance airborne gamma-spectrometric survey, and only at the site "Kristall" were 

 airborne geophysical operations performed later. 



Parameters of sectors of radioactive contamination that were foimd and 

 investigated: 



"Sheksna" - 50x50 m, the exposure dose up to 60 ^r/hr, the minimum dose on the 

 surface 239 ^r/hr, the total beta activity in soil 640 (460) Bq/kg (here and below the 

 results of radiochemical analysis in parentheses indicate the minimum values for the 

 site); strontium-90, 160 (88) Bq/kg; cesium-137, 350 (70) Bq/kg. In vegetation (reindeer 

 moss), the total beta activity was 979 Bq/kg; strontium-90, 220 Bq/kg; cesium-137, 166 



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