Radiological states around the Kraton-4 underground nuclear explosion sitein Sakha

Underground nuclear explosion/Sakha/Gamma-survey/In-situ spectroscopy/Cs-13 7 A radiological survey around the site of Kraton-4, an underground nuclear explosion (Yield of 20 kt, depth of 560 m, 1978) in Sakha was carried out in March 1998. Gamma survey and in-situ spectroscopy on the ground exhibite d quite normal levels: a dose rate of 0.022 Sv/ and Cs-137 surface contamin ation of less than 1.1 kBq/mZ around the hypocenter. The results suggested no remarkable leakage of radioactivity from the epicenter to the ground sur face at least not for non-rare gas elements as of 1998.