359 



A total of 12 profiles, 500 to 1,700 m long, were passed, and radioactive 

 contamination was monitored for 3.0 km (Figure 16). The results of surface observations 

 were practically comparable with the data from the airborne gamma-spectrometric 

 survey. 



The nature of gamma radiation from field observations was determined by the 

 presence of cesium-137 (Figure 17,a-fl). 



We used the value of the background, 10 /xr/hr, as the boundary of the 

 contamination spot, when the presence of cesium-137 against a background of 8 /if/hr is 

 recorded reliably by the instrument RSP-IOIM Toisk-Pripyat" (Figure 17j»), 



The density of the flux of beta particles within the contamination spot reaches 98 

 particles/min.cm^ at the shaft mouth and 60-90 particles/min.cm^ along the line in the 

 area of profiles 5 and 6 against the backgroui.d of 2-4 particles/min.cm^ beyond tne 

 boundaries of the spot (measurements were made at a distance of 10 cm from the 

 surface). 



The results of the measurements suggested the presence of sfrontium-90. 



On the isogam of 5 Mf/hr (Figure 8), the airborne gamma-spectrometric survey 

 around the main trace revealed and delimited contamination spots that spanned the first 

 few hundred meters to the first few kilometers. The nature of their distribution makes it 

 possible to talk about a possible spread of spots over tens of kilometers. During the test, 

 two spots were visited: the spot on the right bank of the Markha River downstream from 

 the mouth of the Chukoka River: 12 /ir/hr (water sampling sites SIO and Sll), and the 

 spot that is the closest to the main trace to the east: 15-17 /ir/hr (water sampling sites 

 y-8n and y-6P). 



According to calculations performed by LtCol. A,I. Chomchoyev, chief of staff of 

 the Civil Defense of the city of Yakutsk, the levels of radioactivity in the nearest trace at 

 the time of discharge could exceed 200 /xr/hr, and the total contamination of this area at 

 the present time is up to 3,000,000 Bq/kg (calculations were made before the results of 

 the analysis were received). 



Results of Sampling 



Diiring field operation on the "Aykhal" site, soil, vegetation and water were tested. 

 Testing as well as analytical operations were performed in accordance with the 

 appropriate departmental procedures. A totad of 44 sofl samples, 14 vegetation samples, 

 and 20 water samples were taken. The distribution of soQ and vegetation sampling sites 

 is given in Figure 18, and water samples are presented in Figure 19. 



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