Since June till September 2017, the personnel of Chornobyl NPP Radiation Safety Shop carried out measurement of gamma-radiation dose rate (EDR) in the near field of New Safe Confinement (NSC). The measurement goal is to study how much gamma-radiation level has been reduced within work execution area after NSC Arch sliding in the designed position. The measurements were made in three vertical planes, each of which had nine control points at the heights 30, 60, and 90 meters above ground. The measurement planes are located 120, 256, and 355 m from the Shelter Object covering the whole area of work execution. The EDR measurements at heights were performed using an unmanned aerial vehicle (UAV) and a dosimeter DMC 2000S. After completion of preparatory activities for NSC construction (removal of process materials and solid radioactive waste, concreting of Arch assembling area, and filling the work execution area with non-radioactive gravel) and following the Arch’s set into the designed position the gammaradiation in the near field of NSC reduced in average more than 10 times. In 2018, the EDR measurement was continued at different heights around the NSC. The way of delivering the monitoring devices into the target height point remained the same as in previous year, i.e. using the UAV. But this time, the RSS personnel used radio dosimeters Mini- TRACE-γ S100R as radiation monitoring equipment. The peculiarity of these dosimeters is that they are operated online and monitoring results are transferred by radio channel to an operator’s workplace who, in his turn, takes the reading. This dosimeter was suspended to the UAV body and delivered to the target control point. The dose rate was measured at the same heights as previously – 30, 60, and 90 m above the industrial site level. Comparing the previous method of control, the application of these dosimeters reduces significantly the error in dose rate measurement. The main objective of the measurements is to determine gamma-radiation dose rate at the specified heights. In future, it will give an opportunity to compare the results received at this time with the results to be received after completion of activities on dismantling of unstable structures of the Shelter Object enabling to develop additional radiation protection measures, if required.
Keywords: New Safe Confinement, “Shelter” object, gamma-radiation, equivalent dose rate.
1. SIP K 01 21 310 MR1 003 02. Task 1: Measurement of the aerial fields of gamma radiation. Phase 1. Measurement report. (Rus)
2. SIP K 01 21 310 MR2 003 02. Task 1: Measurement of the aerial fields of gamma radiation. Phase 2. Measurement report. (Rus)
3. Operation manual for use of electronic personal dosimeters of the DMC 2000S series and LDM 2000 reader of MGP, 29Э-ЦРБ. (Rus)
4. Operation manual for radiation monitoring devices of the radiation safety department, 43Э-ЦРБ. (Rus)
5. Operation manual of the electronic radio dosimeter MiniTRACE-γ S100R. (Rus)