Radon in sub-reactor room 012/7 of ''Ukryttya'' object

Survey sessions were made with using seismic radon station SRS-05 in ''Ukryttya'' object room 012/7, which lasted from 2 to 50 hours. It was stated that under average radon concentration being 80 Bq/m³, maximum values reached 400 - 500 Bq/m³. Parallel samplings in ''Bypass'' system have demonstrated that radon concentration in airflow being released into free atmosphere from ''Ukryttya'' object is in 4 - 5 fold lower than that in the room 012/7. It was established that during 2 - 3 days the dynamics of radon and thoron concentrations can essentially differ. Therefore, there are several sources in sub-reactor rooms for emanating radioactive gases, in particular, concrete structures containing diverse amount and ratio of ²²⁶Ra and ²³²Th. Temperature difference inside the room 012/7 and in outer environment does not influence radon concentration in this room. Radon content depends on wind within the ''Ukryttya'' object environs. The highest concentrations were registered when average wind velocity reached 4 m/s, and maximum gusts exceeded 9 - 10 m/s. As result of inhalation of radon, thoron and their daughter products, personnel exposure in room 012/7 can make up to 10 % of effective dose limit.