Speaker
Description
System of emergency monitoring of artificial radioactivity in the environment in the Czech Republic is based on the scheme created for routine monitoring. That means, that picked samples are analysed by the lab procedures, only frequency of sampling and sensitivity of the procedures is adjusted according to Decree 360/2016. Radiation events from previous years brought evidence, that monitoring techniques with enhanced time resolution employed as supplementary monitoring tools can bring indispensable information (Masson et al., 2019).
A natural consequence of the increased likelihood of radiation risk observed in recent years is the development of various types of monitoring units for determining artificial radioactivity in the environment, as well as the subsequent installation of sensor networks.
A pilot network of aerosol samplers capable of real-time determination of artificial gamma activity in atmospheric aerosol was supplemented by networks of the following three types of real-time measuring devices in the subsequent years: submersible surface water gamma probe (Fejgl and Hýža, 2019); rain water collector determining artificial gamma activity; ambient dose equivalent (H*10) monitoring station (ZV) with the ability to identify source radionuclides and their spatial distribution.
The last two devices are prone to contamination from atmospheric fallout, what makes them difficult to work well in the event of radiation accident. Series of experiments with the aim of reinforcement their capabilities under severe conditions were performed.
Rainwater collector is based on 5L through-flow Marinelli beaker equipped with 2inch NaI(Tl) detector. Both energy and efficiency calibration were conducted for different radionuclides (Cs-134,Cs-137, I-131, Co-60) in multiple volumes within full volume range of the Marinelli beaker. The contribution of surface contamination was determined in experiments exploiting Tc-99m.
The Groud-Air monitoring station consists of two NaI(Tl) probes, which distinguish between photons originating from the air and the ground, and two Geiger-Mueller detectors utilized for the detection of atmospheric contamination. Both energy and efficiency calibration were conducted for different radionuclides (Cs-137, I-131, Co-60). An alternative approach for surface contamination determination using response of ground facing NaI(Tl) probe was developed. Several radioactivity dispersion experiments, including the determination of deposition distribution, were performed using Tc-99m and ultrasonic aerosol generators. Experiments were carried out in a controlled environment.
The conference contribution focuses on the determination of the most important gamma-emitting radionuclides under nuclear accident scenarios, with emphasis on detection sensitivity and time resolution.
This work was supported by institutional funding from the Ministry of the Interior of the Czech Republic.