ON THE QUESTION OF DETERMINING THE ACTIVITY OF FAULT ZONES OF THE PRECAMBRIAN CRYSTALLINE FOUNDATION AT THE ZAPORIZHZHIA NPP SITE BASED ON RADON MEASUREMENTS

Problem statement. The completed studies were due to the post-Fukushima reassessment of the site's seismic hazard and seismic resistance at the Zaporizhzhia NPP (Nuclear Power Plant), considering changes in geotechnical conditions during the plant operation. And also, to increase its operational reliability and safety. The basis was the international requirements for nuclear safety and the IAEA Safety Standards Series no. SSG-9, the requirements of domestic and foreign standards for the design of earthquake-resistant atomic power plants. The highly specialized research was conducted firstly in the country and tested at the site of the Zaporizhzhia NPP, with further improvement of the methodology it is quite possible for the stated purposes at the sites of other nuclear power plants, especially those located in seismically active zones. Purpose of the article. The purpose of the article is to test the methodology for determining the degree of tectonic activity of previously assumed, and subsequently confirmed by drilling and geophysics, fault zones at the Zaporizhzhia NPP site based on monitoring of radon in groundwater. Also, in the future, justify the use of radonometry for accurate mapping of fault zones in igneous rocks of the Ukrainian Crystalline Massif. Conclusions and results. The authors analysed archival data on the geology and hydrogeology of the NPP site and data on the radon content in the groundwater of crystalline basement rocks. We described existing methods for collecting water samples for radon and testing them in laboratory conditions. The data obtained as a result of the monitoring of radon in groundwater indicate the absence of neo-tectonic activity of a natural character on the site of the geodynamic polygon. This site is immediately adjacent to the Zaporizhzhia NPP site, and primarily in the zone of the sublatitudinal fault uncovered by one of the wells and crossing the NPP site in the area of the fourth block. The result of comparative studies of radon volumetric activity (VAR) indicators in the aquifer's fissure-vein waters of the crystalline Precambrian basement during 2012−2015 was confirmation of the fundamental possibility of assessing the tectonic activity of fault zones of the geodynamic polygon at the Zaporizhzhia NPP when carrying out radon monitoring.