353 



On the map of the gamma field of sector No. 3, the isolines were also drawn 

 every S nr/hi. The sector is characterized by a background gamma activity of no higher 

 than 15 /ir/hr. In this sector two underground nuclear explosions were conducted. The 

 natxire of the gamma field above the wells is normal (Figures 6, 7). 



The "Avkhal" site. The survey of this sector entailed a series of smface operations 

 (Figure 8). 



An airborne geophysical survey confirmed the presence of radioactive 

 contamination 3^0 m south-southwest from the mouth of the River Chulnika, the left 

 tributary of the River Markha. The sector with radioactivity of higher than 10 nr/hi is 1 

 X 3.75 Ian in size and extends in a northeasterly direction (Figure 9). The highest 

 radioactivity of up to 70 nr/bi was registered in the southwestern part of the 

 contaminated sector. Since the nature of radioactivity of this sector was established 

 unambiguously by the surface operations, including that in, the mouth of the River 

 Qiukuka where gamma field radioactivity is slightly higher than 5 Mr/hr, surface 

 operations should be conducted in this area for determining the nature of other "spots" 

 with radioactivity over 5 /ir/hr, and also aerial operations should be expanded for 

 detecting similar "spots" in adjacent areas. 



The "Udachgy " site. In August of 1990 an airborne gamma-spectrometric survey 

 on the scale of 1:10,000 was conducted on the left bank of the Daldyn (Figure 10). On 

 the gamma field map, the site of the explosion and traces of the discharge are fixed by 

 the 10 Mr/hr isogamma; the maximum values in the epicenter reach 25 la/bi (Figure 11). 

 In addition to the map of the gamma field, we present a copy from the map of uranium 

 concentratioiis (Figure 12) which indicates that the site of the nuclear explosion was also 

 recorded in the uranium channel 



22 Sorihoe Dosimetric and Radiometric Operations 



Surface operations were plaimed, taking into account the data obtained from an 

 advance airborne gamma-spectrometric survey, in sectors with increased levels of 

 radioactivity that were not clearly related to the sites of underground nuclear explosions 

 by the method of landing an "assault team", conducting measurements and sampling sofl 

 and water, in sectors where radioactive contamination was detected, detafled operations 

 were carried out on a scale determined by the dimensions of the object detected. 



For performing these tasks the team was equip{>ed with a sufficient number of 

 radiometers and dosimeters: 6 SRP-68-01, 1 DRG-OIT, 1 DKS-04, 1 DP-5, 1 IMI>-12, 2 

 RSP-IOIM Poisk-Pripyat with gamma and beta detectors, 1 RKB4-IeM. AD of these 

 instruments were tested metrologically in 1989-1990. 



In the course of carrying out the planned program of operations, the inadequacy 

 of the "assault team" technique immediately became obvious: the time limitation when 



