Kremena Ivanova - Academia.edu (original) (raw)

Papers by Kremena Ivanova

Dokladi na Bʺlgarskata akademiâ na naukite, Apr 26, 2024

Environmental spread of radon gas (222Rn) has been intensively investigated in the last few years... more Environmental spread of radon gas (222Rn) has been intensively investigated in the last few years due to its harmful effects on human health. A concept of radon index is used to characterize the geogenic radon potential of the terrain, as the latter gives the probability of the presence of radon gas concentration in a building, the genesis of which is directly related to the influence of the earth's surface. One of the approaches for quantifying the radon index is based on a multivariate cross-tabulation, which includes two parameters-radon concentration in soil gas and gas permeability of the earth layer (at 80 cm). The geology of the specific site (approx. 350 m 2) is characterized by the Pliocene clayey-sandy Formation, covered with Quaternary sediments. From tectonic point of view, the site as a part of Sofia Graben, has being subject of events related mainly with the Late Alpine deformations heading to very complex structures and fault systems. In situ measurements performed in the summer of 2023 at ten distinct points at the surface and 11 distinct points at two meters in depth from the surface vary as follows: from 44.2 to 189.0 kBq/m 3 (radon soil gas), from 2.0E−11 to 1.8E−13 m 2 (soil gas permeability), and from 0.10 to 0.17 µSv/h (gamma dose rate). Based on that, the radon index of the site is determined from "medium" to "high", with a predominance of the latter.

Списание на Българското геологическо дружество, Nov 1, 2022

Резюме. Естественият радон (222Rn) е радиоактивен благороден газ, който се среща във всяка скала ... more Резюме. Естественият радон (222Rn) е радиоактивен благороден газ, който се среща във всяка скала или почва поради съдържанието на радий (226Ra), част от семейството 238U, в литосферата. Един от показателите за оценка на влиянието на радона върху определена площ/терен, включително и върху биотата, е т.нар. геогенен радонов потенциал. Различните видове скали и почви имат различно съдържание на 226Ra, както и различна пропускливост. Радонът като газ има висока подвижност и се придвижва от процесите на дифузия и конвекция с почвения газ през свързани и ненаситени с вода пори и/или пукнатини в скали и почви. Следователно, геогенният радоновия потенциал на повърхността се влияе от геоложките особености (като съдържание на уран в скалите), но и също така-от хидрогеоложките характеристики (като степен на водонасищане близо до повърхността). Настоящото изследване разглежда основно различните по генезис плиткозалягащи подземни води в България въз основа на публикувани източници от 1960 г. насам. След анализ на събраните данни са отделени няколко района, по отношение на литоложките и геоморфоложки условия, и на база дълбочина 0-3 m на нивото на подземните води. В допълнение, е разработена ГИСбазирана карта, свързваща скалите с очакван висок радонов потенциал и зоните с плитко залягащи подземни води.

Review of the Bulgarian Geological Society

Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the con... more Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the content of radium (226Ra), part of the 238U family, in the lithosphere. One of the indicators for evaluating the impact of radon on a certain area/terrain, including on the biota, is the so-called geogenic radon potential. Different types of rocks and soils possess different 226Ra content and different permeability. Radon gas has high mobility and is driven by diffusion and convection with the soil gas throughout connected and water-unsaturated pores and/or cracks in permeable rocks and soils. Therefore the geogenic radon potential at the surface could be affected by the geological settings as a content of uranium and also by the hydrogeological settings as a degree of saturation near the surface. The present study mainly deals with the different by genesis shallow groundwater in Bulgaria based on the published since 1960’s sources. After analysis of the collected data several distinct regi...

Radiation Protection Dosimetry, May 24, 2023

The study presents the analysis of the results for indoor radon concentration in the kindergarten... more The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children’s rooms situated in 157 kindergartens. The measured radon concentrations in the children’s rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity of measuring the indoor radon concentration before the renovation and repair of the building, especially the implementation of energy efficiency measures.

Journal of Radiation Research and Applied Sciences, Jun 1, 2023

Building and Environment, Oct 1, 2021

This paper presents an evaluation of the indoor radon spatial variation between and within school... more This paper presents an evaluation of the indoor radon spatial variation between and within school buildings. Radon measurements were carried out in 331 rooms of 16 school buildings in 5 municipalities of Plovdiv province, Bulgaria. They were performed with CR-39 nuclear track detectors exposed over an 8-month period from September 2018 to April 2019. The arithmetic and geometric means together with corresponding standard deviation and geometric standard deviations of the indoor radon concentration were 160 ± 175 Bq/m 3 and 108 */2.35 Bq/m 3 , respectively. The best data fit was achieved with a Weibull 3-parameter function (Kolmogorov-Smirnov test, p = 0.2916). The effect of the school location and various building characteristics on the indoor radon concentration distribution within a province was investigated. The analyses showed that the factor "year of building construction", which is in general related with the technical condition of the building, imposed the highest impact on the indoor radon concentration difference between schools. The vertical and horizontal components of the indoor radon spatial variability within a school were analysed as well. The results concerning the radon variation within schools could be used to optimize future radon school surveys. In this paper, quality control for indoor radon measurement procedures and radon health impact assessments was included.

The European Physical Journal Special Topics

All IAEA scientific and technical publications are protected by the terms of the Universal Copyri... more All IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952 (Berne) and as revised in 1972 (Paris). The copyright has since been extended by the World Intellectual Property Organization (Geneva) to include electronic and virtual intellectual property. Permission to use whole or parts of texts contained in IAEA publications in printed or electronic form must be obtained and is usually subject to royalty agreements. Proposals for non-commercial reproductions and translations are welcomed and considered on a case-by-case basis. Enquiries should be addressed to the IAEA Publishing Section at:

Nukleonika

The major part of the radiation dose that humans receive from natural radioactive sources is due ... more The major part of the radiation dose that humans receive from natural radioactive sources is due to inhalation of radon and its decay products. The study focuses on radon concentration (CRn) investigation in kindergartens and nurseries in the district of Montana. The influence of building characteristics on CRn was evaluated. The measurement of the CRn was performed using passive detectors. The survey was carried out between December 2019 and May 2020 with a total number of 602 detectors. The average value of CRn in the premises of the studied kindergartens and nurseries in this district is 125 Bq·m−3, and the geometric mean (GM) value is 88 Bq·m−3. The buildings that have built ventilation and sewerage systems have lower CRn. The effective doses of the children and workers were evaluated in order to assess the radon exposure.

Proceedings of the Bulgarian Academy of Sciences

The development of a methodology for the geogenic radon potential (GRP) mapping based on soil gas... more The development of a methodology for the geogenic radon potential (GRP) mapping based on soil gas radon and soil gas permeability field measurements is among the main objectives in the determination of “radon priority areas” in Bulgaria. One of the key elements of the methodology is to define as accurately as possible, areas of risk for the presence of radon gas (222Rn) on the map. This study presents an approach to spatial sampling for the geogenic radon potential survey in Sliven Province, Bulgaria. The district is characterised by its very complex geological settings, represented by rocks of different age and mineral and chemical compositions. The proposed methodology defined a sampling frame of province radon map, prepared on the base of indoor radon measurement and the complex sampling scheme of random points. The parcel-level GIS was used for establishing the sample frame of 5×5 km polygons on the territory of the province. The IBM SPSS Complex Samples Module was applied for p...

In the last decade, many studies have been made for measuring natural radioactivity in regions of... more In the last decade, many studies have been made for measuring natural radioactivity in regions of the Republic of Macedonia. However, the information on terrestrial radiation exposure, and, consequently, risk assessment were not available. In this study, a risk assessment was done considering a specific activity concentration of 226 Ra, 232 Th, 40 K and 137 Cs in the topsoil. The results indicate that the external gamma doses due to natural radionuclides in soils are higher than those of 137 Cs. The absorbed dose rate in air varies in intervals: from 4.3 to 57 nGy/h (due to 226 Ra); from 3.9 to 88 nGy/h (due to 232 Th); from 3.3 to 58 nGy/h (due to 40 K); and from 0.01 to 5.3 nGy/h (due to 137 Cs). In addition, the mean annual effective doses due to natural radionuclides and 137 Cs in the soils of the Republic of Macedonia are estimated to be 78 μSv and 1.01 μSv, respectively. As well as, the values of external hazard index Hex indicate in general low gamma radiation risk for populations living in the Republic of Macedonia.

Radiation Protection Dosimetry

The study presents the analysis of the results for indoor radon concentration in the kindergarten... more The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children’s rooms situated in 157 kindergartens. The measured radon concentrations in the children’s rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity o...

Radiation Protection Dosimetry

Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for t... more Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for the period November/December 2019 to May/June 2020. The measurements were carried out in 2427 rooms on the basement, ground floor and first floor using the passive track detectors of the Radosys system. The estimated arithmetic and geometric means with standard deviations were 153 ± 154 and 114 Bq/m3 (geometric standard deviation (GSD) = 2.08), respectively. The results are higher than those referred from the National Radon Survey in dwellings. In 9.4% of the rooms, the radon concentrations were above the reference value of 300 Bq/m3. The difference between indoor radon concentrations in the districts was significant, which proves its spatial variation. The hypothesis that the applied energy efficiency measures increase indoor radon values in buildings was confirmed. The surveys demonstrated the importance of indoor radon measurements in school buildings, in order to control and reduce ch...

Review of the Bulgarian Geological Society

The study deals with the evaluation of the dynamic of the radon index in one pilot site based on ... more The study deals with the evaluation of the dynamic of the radon index in one pilot site based on second-time pilot investigations of the radon index in Bulgaria. In situ measurements of the radon concentration in soil gas, and soil permeability at three polygons: one over and two – close to fault zone have been performed in October 2020 and October 2022. The results show that higher radon content is detected in the fault zone in both cases.

Journal of the European Radon Association

The exposure to radon in buildings open to the public and at workplaces depends on many factors, ... more The exposure to radon in buildings open to the public and at workplaces depends on many factors, for example, forms of utilization, construction conditions, time of exposure, heating, and ventilation conditions, etc. To evaluate the radon exposure in different working environments, continuous simultaneous measurements of radon (CRn), equilibrium equivalent (EEC), and potential alpha energy (PAEC) concentrations for 24 hours were performed using AlphaE for CRn and DOSEman PRO from SARAD GmbH for EEC and PAEC measurements. The study considered measurements at three locations in the radon-rich spa of Narechen, Asenovgrad, and at an old mine turned museum in the town of Pernik. A comparison was made between the average values of the concentrations relating to all-day and only working hours when the measurements were completed. The CRn increases during the working hours in the museum as well as in the bath of the spa, while it decreases in the spa’s treatment room. On the other hand, the...

Aerosol and Air Quality Research

Indoor radon exposure is the largest contributor to population dose from natural sources. Radon a... more Indoor radon exposure is the largest contributor to population dose from natural sources. Radon as a natural radioactive gas could accumulate to harmful levels in buildings, such as homes and buildings with public access. In order to assess the exposure due to radon in school the results of indoor radon measurements in 55 state school buildings in 7 municipalities located in one district in southern Bulgaria are considered in this paper. The survey was carried out with passive CR-39 etched track detectors. Radon concentrations ranged from 17 to 868 Bq.m-3 , with a geometric mean of 117 Bq.m-3 and a geometric standard deviation of 1.78. The findings revealed that in 30 % of the measured buildings the radon concentration was higher than the national reference level of 300 Bq.m-3. The statistically significant difference in indoor radon concentrations between municipalities (KW, р < 0.001) was obtained. The research was also focused on parameters affecting radon concentration levels such as type of room and floor location. The estimated annual effective dose of 0.39 to 1.07 mSv.y-1 , applying the ICRP and UNSCEAR methodology, was calculated for students. The results of the measurements were provided to the administrative authorities and measures were proposed to improve the air in school buildings with high radon levels.

As a very mountainous country, Bulgaria has a lot of caves, but only some of them are developed, ... more As a very mountainous country, Bulgaria has a lot of caves, but only some of them are developed, managed and available for tourist visits. The main sources of radon are rocks and a high concentration can be measured in caves. Caves have been of interest because radon concentration in these environments may sometimes reach high values. A rather large number of investigations have been carried out all over the world, from the point of view of both researches on radon behavior in a cave environment and radiation protection. There are no systematic investigations of radon in the caves in Bulgaria in order to assess the health risk. The paper presents the sample design of the radon concentration survey in Bulgarian caves for the evaluation of the health risk of people. The sample design covers the method of selection, the sample structure and the plan for analyzing and interpreting the results. The method selected to define the representative sample corresponds to the following criteria:...

This study discusses the sampling frames of the buildings with public access to radonconcentratio... more This study discusses the sampling frames of the buildings with public access to radonconcentration surveys on the territory of Bulgaria in order to assess the health risk for the population.The sampling frame is the list from which the sample is selected, so the quality of the sampling frameaffects the quality of the sample. The general list of different types of buildings with public access hasbeen prepared in accordance with the list of the Ministry of the Regional Development and PublicWorks in Bulgaria and international experience in the field of radon investigation. The types ofbuildings with public access have been classified in nine general groups. These groups of buildingswith public access are defined as follows: educational institutions; buildings for commerce and/orservices; health and social care buildings; buildings in the field of culture; sports facilities; buildingsin the field of transport; prisons; cult and religious buildings and post offices. Multicriteria analys...

Dokladi na Bʺlgarskata akademiâ na naukite, Apr 26, 2024

Environmental spread of radon gas (222Rn) has been intensively investigated in the last few years... more Environmental spread of radon gas (222Rn) has been intensively investigated in the last few years due to its harmful effects on human health. A concept of radon index is used to characterize the geogenic radon potential of the terrain, as the latter gives the probability of the presence of radon gas concentration in a building, the genesis of which is directly related to the influence of the earth's surface. One of the approaches for quantifying the radon index is based on a multivariate cross-tabulation, which includes two parameters-radon concentration in soil gas and gas permeability of the earth layer (at 80 cm). The geology of the specific site (approx. 350 m 2) is characterized by the Pliocene clayey-sandy Formation, covered with Quaternary sediments. From tectonic point of view, the site as a part of Sofia Graben, has being subject of events related mainly with the Late Alpine deformations heading to very complex structures and fault systems. In situ measurements performed in the summer of 2023 at ten distinct points at the surface and 11 distinct points at two meters in depth from the surface vary as follows: from 44.2 to 189.0 kBq/m 3 (radon soil gas), from 2.0E−11 to 1.8E−13 m 2 (soil gas permeability), and from 0.10 to 0.17 µSv/h (gamma dose rate). Based on that, the radon index of the site is determined from "medium" to "high", with a predominance of the latter.

Списание на Българското геологическо дружество, Nov 1, 2022

Резюме. Естественият радон (222Rn) е радиоактивен благороден газ, който се среща във всяка скала ... more Резюме. Естественият радон (222Rn) е радиоактивен благороден газ, който се среща във всяка скала или почва поради съдържанието на радий (226Ra), част от семейството 238U, в литосферата. Един от показателите за оценка на влиянието на радона върху определена площ/терен, включително и върху биотата, е т.нар. геогенен радонов потенциал. Различните видове скали и почви имат различно съдържание на 226Ra, както и различна пропускливост. Радонът като газ има висока подвижност и се придвижва от процесите на дифузия и конвекция с почвения газ през свързани и ненаситени с вода пори и/или пукнатини в скали и почви. Следователно, геогенният радоновия потенциал на повърхността се влияе от геоложките особености (като съдържание на уран в скалите), но и също така-от хидрогеоложките характеристики (като степен на водонасищане близо до повърхността). Настоящото изследване разглежда основно различните по генезис плиткозалягащи подземни води в България въз основа на публикувани източници от 1960 г. насам. След анализ на събраните данни са отделени няколко района, по отношение на литоложките и геоморфоложки условия, и на база дълбочина 0-3 m на нивото на подземните води. В допълнение, е разработена ГИСбазирана карта, свързваща скалите с очакван висок радонов потенциал и зоните с плитко залягащи подземни води.

Review of the Bulgarian Geological Society

Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the con... more Natural radon (222Rn) is a radioactive noble gas that occurs in every rock or soil due to the content of radium (226Ra), part of the 238U family, in the lithosphere. One of the indicators for evaluating the impact of radon on a certain area/terrain, including on the biota, is the so-called geogenic radon potential. Different types of rocks and soils possess different 226Ra content and different permeability. Radon gas has high mobility and is driven by diffusion and convection with the soil gas throughout connected and water-unsaturated pores and/or cracks in permeable rocks and soils. Therefore the geogenic radon potential at the surface could be affected by the geological settings as a content of uranium and also by the hydrogeological settings as a degree of saturation near the surface. The present study mainly deals with the different by genesis shallow groundwater in Bulgaria based on the published since 1960’s sources. After analysis of the collected data several distinct regi...

Radiation Protection Dosimetry, May 24, 2023

The study presents the analysis of the results for indoor radon concentration in the kindergarten... more The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children’s rooms situated in 157 kindergartens. The measured radon concentrations in the children’s rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity of measuring the indoor radon concentration before the renovation and repair of the building, especially the implementation of energy efficiency measures.

Journal of Radiation Research and Applied Sciences, Jun 1, 2023

Building and Environment, Oct 1, 2021

This paper presents an evaluation of the indoor radon spatial variation between and within school... more This paper presents an evaluation of the indoor radon spatial variation between and within school buildings. Radon measurements were carried out in 331 rooms of 16 school buildings in 5 municipalities of Plovdiv province, Bulgaria. They were performed with CR-39 nuclear track detectors exposed over an 8-month period from September 2018 to April 2019. The arithmetic and geometric means together with corresponding standard deviation and geometric standard deviations of the indoor radon concentration were 160 ± 175 Bq/m 3 and 108 */2.35 Bq/m 3 , respectively. The best data fit was achieved with a Weibull 3-parameter function (Kolmogorov-Smirnov test, p = 0.2916). The effect of the school location and various building characteristics on the indoor radon concentration distribution within a province was investigated. The analyses showed that the factor "year of building construction", which is in general related with the technical condition of the building, imposed the highest impact on the indoor radon concentration difference between schools. The vertical and horizontal components of the indoor radon spatial variability within a school were analysed as well. The results concerning the radon variation within schools could be used to optimize future radon school surveys. In this paper, quality control for indoor radon measurement procedures and radon health impact assessments was included.

The European Physical Journal Special Topics

All IAEA scientific and technical publications are protected by the terms of the Universal Copyri... more All IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952 (Berne) and as revised in 1972 (Paris). The copyright has since been extended by the World Intellectual Property Organization (Geneva) to include electronic and virtual intellectual property. Permission to use whole or parts of texts contained in IAEA publications in printed or electronic form must be obtained and is usually subject to royalty agreements. Proposals for non-commercial reproductions and translations are welcomed and considered on a case-by-case basis. Enquiries should be addressed to the IAEA Publishing Section at:

Nukleonika

The major part of the radiation dose that humans receive from natural radioactive sources is due ... more The major part of the radiation dose that humans receive from natural radioactive sources is due to inhalation of radon and its decay products. The study focuses on radon concentration (CRn) investigation in kindergartens and nurseries in the district of Montana. The influence of building characteristics on CRn was evaluated. The measurement of the CRn was performed using passive detectors. The survey was carried out between December 2019 and May 2020 with a total number of 602 detectors. The average value of CRn in the premises of the studied kindergartens and nurseries in this district is 125 Bq·m−3, and the geometric mean (GM) value is 88 Bq·m−3. The buildings that have built ventilation and sewerage systems have lower CRn. The effective doses of the children and workers were evaluated in order to assess the radon exposure.

Proceedings of the Bulgarian Academy of Sciences

The development of a methodology for the geogenic radon potential (GRP) mapping based on soil gas... more The development of a methodology for the geogenic radon potential (GRP) mapping based on soil gas radon and soil gas permeability field measurements is among the main objectives in the determination of “radon priority areas” in Bulgaria. One of the key elements of the methodology is to define as accurately as possible, areas of risk for the presence of radon gas (222Rn) on the map. This study presents an approach to spatial sampling for the geogenic radon potential survey in Sliven Province, Bulgaria. The district is characterised by its very complex geological settings, represented by rocks of different age and mineral and chemical compositions. The proposed methodology defined a sampling frame of province radon map, prepared on the base of indoor radon measurement and the complex sampling scheme of random points. The parcel-level GIS was used for establishing the sample frame of 5×5 km polygons on the territory of the province. The IBM SPSS Complex Samples Module was applied for p...

In the last decade, many studies have been made for measuring natural radioactivity in regions of... more In the last decade, many studies have been made for measuring natural radioactivity in regions of the Republic of Macedonia. However, the information on terrestrial radiation exposure, and, consequently, risk assessment were not available. In this study, a risk assessment was done considering a specific activity concentration of 226 Ra, 232 Th, 40 K and 137 Cs in the topsoil. The results indicate that the external gamma doses due to natural radionuclides in soils are higher than those of 137 Cs. The absorbed dose rate in air varies in intervals: from 4.3 to 57 nGy/h (due to 226 Ra); from 3.9 to 88 nGy/h (due to 232 Th); from 3.3 to 58 nGy/h (due to 40 K); and from 0.01 to 5.3 nGy/h (due to 137 Cs). In addition, the mean annual effective doses due to natural radionuclides and 137 Cs in the soils of the Republic of Macedonia are estimated to be 78 μSv and 1.01 μSv, respectively. As well as, the values of external hazard index Hex indicate in general low gamma radiation risk for populations living in the Republic of Macedonia.

Radiation Protection Dosimetry

The study presents the analysis of the results for indoor radon concentration in the kindergarten... more The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children’s rooms situated in 157 kindergartens. The measured radon concentrations in the children’s rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity o...

Radiation Protection Dosimetry

Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for t... more Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for the period November/December 2019 to May/June 2020. The measurements were carried out in 2427 rooms on the basement, ground floor and first floor using the passive track detectors of the Radosys system. The estimated arithmetic and geometric means with standard deviations were 153 ± 154 and 114 Bq/m3 (geometric standard deviation (GSD) = 2.08), respectively. The results are higher than those referred from the National Radon Survey in dwellings. In 9.4% of the rooms, the radon concentrations were above the reference value of 300 Bq/m3. The difference between indoor radon concentrations in the districts was significant, which proves its spatial variation. The hypothesis that the applied energy efficiency measures increase indoor radon values in buildings was confirmed. The surveys demonstrated the importance of indoor radon measurements in school buildings, in order to control and reduce ch...

Review of the Bulgarian Geological Society

The study deals with the evaluation of the dynamic of the radon index in one pilot site based on ... more The study deals with the evaluation of the dynamic of the radon index in one pilot site based on second-time pilot investigations of the radon index in Bulgaria. In situ measurements of the radon concentration in soil gas, and soil permeability at three polygons: one over and two – close to fault zone have been performed in October 2020 and October 2022. The results show that higher radon content is detected in the fault zone in both cases.

Journal of the European Radon Association

The exposure to radon in buildings open to the public and at workplaces depends on many factors, ... more The exposure to radon in buildings open to the public and at workplaces depends on many factors, for example, forms of utilization, construction conditions, time of exposure, heating, and ventilation conditions, etc. To evaluate the radon exposure in different working environments, continuous simultaneous measurements of radon (CRn), equilibrium equivalent (EEC), and potential alpha energy (PAEC) concentrations for 24 hours were performed using AlphaE for CRn and DOSEman PRO from SARAD GmbH for EEC and PAEC measurements. The study considered measurements at three locations in the radon-rich spa of Narechen, Asenovgrad, and at an old mine turned museum in the town of Pernik. A comparison was made between the average values of the concentrations relating to all-day and only working hours when the measurements were completed. The CRn increases during the working hours in the museum as well as in the bath of the spa, while it decreases in the spa’s treatment room. On the other hand, the...

Aerosol and Air Quality Research

Indoor radon exposure is the largest contributor to population dose from natural sources. Radon a... more Indoor radon exposure is the largest contributor to population dose from natural sources. Radon as a natural radioactive gas could accumulate to harmful levels in buildings, such as homes and buildings with public access. In order to assess the exposure due to radon in school the results of indoor radon measurements in 55 state school buildings in 7 municipalities located in one district in southern Bulgaria are considered in this paper. The survey was carried out with passive CR-39 etched track detectors. Radon concentrations ranged from 17 to 868 Bq.m-3 , with a geometric mean of 117 Bq.m-3 and a geometric standard deviation of 1.78. The findings revealed that in 30 % of the measured buildings the radon concentration was higher than the national reference level of 300 Bq.m-3. The statistically significant difference in indoor radon concentrations between municipalities (KW, р < 0.001) was obtained. The research was also focused on parameters affecting radon concentration levels such as type of room and floor location. The estimated annual effective dose of 0.39 to 1.07 mSv.y-1 , applying the ICRP and UNSCEAR methodology, was calculated for students. The results of the measurements were provided to the administrative authorities and measures were proposed to improve the air in school buildings with high radon levels.

As a very mountainous country, Bulgaria has a lot of caves, but only some of them are developed, ... more As a very mountainous country, Bulgaria has a lot of caves, but only some of them are developed, managed and available for tourist visits. The main sources of radon are rocks and a high concentration can be measured in caves. Caves have been of interest because radon concentration in these environments may sometimes reach high values. A rather large number of investigations have been carried out all over the world, from the point of view of both researches on radon behavior in a cave environment and radiation protection. There are no systematic investigations of radon in the caves in Bulgaria in order to assess the health risk. The paper presents the sample design of the radon concentration survey in Bulgarian caves for the evaluation of the health risk of people. The sample design covers the method of selection, the sample structure and the plan for analyzing and interpreting the results. The method selected to define the representative sample corresponds to the following criteria:...

This study discusses the sampling frames of the buildings with public access to radonconcentratio... more This study discusses the sampling frames of the buildings with public access to radonconcentration surveys on the territory of Bulgaria in order to assess the health risk for the population.The sampling frame is the list from which the sample is selected, so the quality of the sampling frameaffects the quality of the sample. The general list of different types of buildings with public access hasbeen prepared in accordance with the list of the Ministry of the Regional Development and PublicWorks in Bulgaria and international experience in the field of radon investigation. The types ofbuildings with public access have been classified in nine general groups. These groups of buildingswith public access are defined as follows: educational institutions; buildings for commerce and/orservices; health and social care buildings; buildings in the field of culture; sports facilities; buildingsin the field of transport; prisons; cult and religious buildings and post offices. Multicriteria analys...