Potential Radon Hazard of the Territory of Lermontov Town (Caucasian mineral Waters Region)

Abstract

Purpose: To study the factors determining the potential radon hazard of territories and to identify patterns of its formation in the territory near the former uranium deposit, characterized by an increased concentration of radon in buildings using the example of Lermontov Town, Stavropol Territory. Material and methods: Radon flux density (RFD) measurements were carried out mainly during the dry season using the method of an open chamber with activated carbon. The measurements were performed using equipment included in the Camera-01 measuring complex. IED of gamma radiation was measured using gamma radiation dosimeters DKG-07D “Drozd” at a height of 1 meter above the ground. Specific activity of natural radionuclides in soil samples was measured on a gamma-ray spectrometric complex equipped with a NaI(Tl) scintillation detector of 63 × 63 millimeters with Progress-2000 software, in Marinelli geometry of 1 liter. Results: The values of specific activity for 226Ra, 232Th and 40K in Lermontov Town vary within the ranges of (26‒180) Bq/kg, (19‒99) Bq/kg and (220‒1041) Bq/kg respectively. The RFD from the soil surface varied from 25 mBq/m²s to 2730 mBq/m²s. The average RFD in the city is 232 mBq/m²s, which is approximately 3 times the permissible level for residential building sites. Abnormal high radiation rates, reaching 2730 mBq/m²s, were recorded at three locations. These anomalous points are locally concentrated and may be associated with a possible geodynamically active zone that can be traced between the Cheludivaya and Ostroya Mountains. In the Lermontov Town, where a high and fairly uniform radium content in its soils, the main factor determining variations in radon flux density from the surface is soil permeability. This permeability varies greatly in the loamy-sedimentary deposits that make up most of the city’s area, depending on factors such as the degree of compaction, moisture content, and possibly other variables. The increased values of the specific activity of radionuclides in the soil, radon flux density from the soil surface, including the detected anomalies, as well as indoor radon concentration are due to natural causes and are not related to past activities in the extraction and processing of uranium ores.