First Steps towards a National Approach for Radon Survey in Romanian Schools

Schools are a category of public buildings with a high radon exposure risk, due to their high occupancy factor. In Romania, the elaboration of a methodology for radon measurements in schools is a necessity imposed both by the European legislation and by the relatively high percentage (about 10%) of the mapped territory with a potential increased risk of exposure to the action of ionizing radiation emitted by radon. In order to optimize the design of a national survey aimed to evaluate radon exposure of children in Romanian schools, we conducted a pilot study in two schools in Cluj-Napoca, following the screening measurements carried out in 109 schools and kindergartens from five counties. The specific steps that must be followed were described, taking into account the international protocols and particularities of Romanian territory. The proposed approach could act as a guide for other large buildings and is implicit for the implementation of National Radon Action Plan, approved by HG no. 526/12 July 2018 in accordance with Council Directive 2013/59/EURATOM. The obtained results indicate that a high probability of annual radon concentration above the national reference level is to be expected in schools.

Radon survey in kindergartens and schools of Dushanbe, Republic of Tajikistan

The paper presents results of the radon survey carried out in preschool and school institutions in Dushanbe, Republic of Tajikistan. Radon concentration was measured using solid state nuclear track detectors Radtrak2. Track detectors were exposed for 3 months during the heating and warm seasons of the year in the same premises. In total, the measurements were performed in 200 premises of 14 kindergartens and 36 schools. The radon equilibrium equivalent concentration during the heating and warm seasons and the annual average radon equilibrium equivalent concentration were calculated. Annual average radon equilibrium equivalent concentration in surveyed buildings ranged from 42 to 331 Bq/m3 with the mean value of 98 Bq/m3 on the first floor and 56 Bq/m3 on the second floor. It was shown that both seasonal values and annual average value of radon equilibrium equivalent concentration in the premises on the second floor are lower than in the premises on the first floor. The annual average effective dose to children from exposure to radon and its progeny in the premises of schools and kindergartens in Dushanbe ranged from 0,64 to 1,64 mSv. The limit value of annual average radon equilibrium equivalent concentration in dwellings and public buildings is set to 100 Bq/m3 for newly built buildings and 200 Bq/m3 for existing buildings in the Radiation safety norms (NRB-06) of the Republic of Tajikistan. This limit was exceeded only on the first floors in one kindergarten during the heating season, in three schools during the warm season and in eight schools during the heating season. When comparing the results of measurements of radon equilibrium equivalent concentration with data on the geological structure of underlying rocks at the locations of the surveyed buildings, no regularity was found. Additional detailed measurements in the buildings, including basements, will help to identify the source of radon entry into the indoor air and to develop recommendations for implementing radon remediation actions separately for each building. The survey results were also used to develop a radon map of Dushanbe.

Radon survey in Chelyabinsk Oblast, Russia, in 2008–2011. Analysis of spatial variability of indoor radon concentration

An extensive radon survey was conducted in 2008-2011 in the framework of the Federal target program on the territory of 29 districts of Chelyabinsk Oblast. SSNTDs were used to measure indoor radon concentrations in public buildings, dwellings and industrial buildings. The results are stored in the database “Radon” owned by Research and Technical Center of Radiation-Chemical Safety and Hygiene of Federal Medical-Biological Agency. The paper presents the results of the analysis of spatial variability of indoor radon concentration and the relationship of this value with a set of geological predictors of radon potential of the territory integrated into a map of ecological and radiogeochemical zones. The results show that in all districts and the whole Chelyabinsk Oblast radon concentrations conform to a lognormal distribution, but in ten districts log-logistic distribution fits the data slightly better. Nevertheless, relative difference between the median values of indoor radon concentration calculated from the two fitted distributions yields zero. The results show that dose assessment based on the arithmetic means could lead to an overestimation of the doses from radon in 1.4 times on average compared to that based on the medians. The median value does not exceed 400 Bq/m3 in any of the surveyed territories and the 95th percentile lies between 96 and 1274 Bq/m3. The fraction of indoor radon concentrations above 400 Bq/m3 expected from the fitted distribution lies between less than 0.1 and 26.8%. The highest values of this fraction were obtained for the Sosnovsky, Kaslinsky, Bredinsky districts and the Miassky urban district (except for the city of Miass). A map of ecological and radiogeochemical zones in Chelyabinsk Oblast was released in 1993-1995 and it was based on a set of geological predictors of radon potential of the territory. We analyzed the relationship of these zones with the results of the radon survey. One-way ANOVA on ranks with the Bonferroni correction showed that there is no statistically significant difference at the 95% confidence level amongst the medians of indoor radon concentration on basement, ground and first floors in settlements, which are located on the territory of three of four of these zones and outside of the territory of all zones. In the fourth zone the median was even two times lower than outside of the zones. These results lead to the conclusion that the possibility of using this map as a map of radon-prone areas is very doubtful. Each datapoint stored in the “Radon” database has a number of additional properties, which allows analyzing other types of indoor radon concentration variability such as seasonal or floor-to-floor. It is expected that later this dataset could be used for estimating regional seasonal correction factors.

RADON MEASUREMENTS IN BIG BUILDINGS: PILOT STUDY IN RUSSIA

Detailed analysis of indoor radon concentration distribution by floors was conducted in four children institutions, one office building and two residential houses in Russian cities to develop approaches to draw up a program of radon survey for big buildings. Higher variability of radon concentration was found in high geogenic radon potential (GRP) area when the soil is the main source of radon. No essential dependence of radon concentration on the floor in high-rise buildings was found in low GRP area. The number of required radon measurements is estimated using obtained characteristics of radon variability.

RADON SURVEY IN THE BUILDINGS OF PRE-UNIVERSITY EDUCATION IN MONTENEGRO

During the academic year 2016/17 (September − June), radon was surveyed in all 519 buildings of the pre-university education in Montenegro – primary, high and vocational schools, kindergartens, institutes for children with special needs and student dormitories. Radon detectors (Radosys,RSFV type) were placed in all classrooms, rooms occupied by children and offices on ground floor, and in some rooms on the upper floors. The total number of detectors was 4078, of which 285 were duplicate (control) detectors. During the radon survey, 11.4% of the detectors were lost or damaged. Average 9-month radon activity concentrations were obtained for 3345 rooms in 507 buildings. Mean values of radon concentrations in the rooms were AM = 243 Bq/m3 and GM = 142 Bq/m3, while the corresponding values for Montenegrin dwellings, found in the national radon survey, were more than twice lower. Radon concentrations above 300 Bq/m3 were found in 23.3% of all surveyed rooms and in 3.4% of the rooms they were above 1000 Bq/m3. Radon activity concentrations above 300 Bq/m3 were measured in some rooms in 44% of the buildings, and those above 1000 Bq/m3 in 9.5% of the buildings. Radon levels in educational buildings are significantly higher than in Montenegrin homes, which means that children and educators are more exposed to the harmful effects of radon in schools and kindergartens than at homes (for equal durations of stay in them). This could be resulting from the type of construction of educational buildings, which are usually large low-rise structures, and from a relatively high average age of these buildings.