SPATIAL VARIABILITY OF INDOOR RADON CONCENTRATION IN SCHOOLS: IMPLICATIONS ON RADON MEASUREMENT PROTOCOLS.

The requirements about radon measurements in schools and public buildings included in most of the national and international legislations are generally restricted to all the rooms located at the ground floor and basement, assuming the soil beneath the building as the main source of indoor radon. In order to verify such an assumption for small buildings having at maximum two floors, a preliminary study was performed in 50 schools located in 15 municipalities of the Republic of Srpska. Results of this study suggest that a protocol requiring measurements at the ground floor only may be considered adequate. Due to the high radon spatial variability for rooms at the ground floor, it is preferable to require measurements in a high number of rooms (preferably in all of them) in order to assess the compliance with the reference level established by the legislation.

INDOOR RADON, THORON AND THEIR PROGENY CONCENTRATIONS IN HIGH THORON RURAL SERBIA ENVIRONMENTS.

This article deals with the variation of radon (Rn), thoron (Tn) and their progeny concentrations expressed in terms of equilibrium equivalent concentrations (EERC and EETC), in 40 houses, in four villages of Sokobanja municipality, Southern Serbia. Two types of passive detectors were used: (1) discriminative radon-thoron detector for simultaneous Rn and Tn gases measurements and (2) direct Tn and Rn progeny sensors (DRPS/DTPS) for measuring Rn and Tn progeny concentrations. Detectors were exposed simultaneously for a single period of 12 months. Variations of Tn and EETC appear higher than those of Rn and EERC. Analysis of the spatial variation of the measured concentrations is also reported. This work is part of a wider survey of Rn, Tn and their progeny concentrations in indoor environments throughout the Balkan region started in 2011 year.

The relation between radon in schools and in dwellings: A case study in a rural region of Southern Serbia.

Recognized as a significant health hazard, radon (Rn) has been given increasing attention for years. Surveys of different kinds have been performed in many countries to assess the intensity and the geographical extent of possible Rn problems. Common surveys cover mainly dwellings, the indoor place with highest occupancy, and schools, where people spend a large fraction of their lifetime and which can also be considered exemplary for Rn exposure at workplaces; it has however been observed that relating them is difficult. It was unclear whether residential Rn at a location, or in a region, can be predicted by Rn at a school of that location, or vice versa. To current knowledge, no general rule seems applicable, as few models to describe the relationship between Rn in dwellings and in schools have been developed. In Southern Serbia, a Rn survey in a predominantly rural region was based on measurements in primary schools. The question arose whether or to which degree the results can be considered as indicative or even representative for residential Rn concentrations. To answer the question an additional survey of indoor Rn concentrations in dwellings was initiated, designed and performed in Sokobanja district in 2010-2012 in a manner to be able to detect a relationship if it exists. In the study region, 108 dwellings in 12 villages and towns were selected, with one primary school each. In this paper, we investigate how a relation between Rn in schools and dwellings could be identified and quantified, by developing a model and using experimental data from both the above main and additional surveys. The key criterion is the hypothesis that the relation dwellings - schools, if it exists, is stronger for dwellings closer to a school than for those dwellings further away. We propose methods to test the hypothesis. As result, the hypothesis is corroborated at 95% significance level. More specifically, on town level (typical size about 1 km), the Rn concentration ratio dwelling/school is about 0.8 (geometrical mean), with geometrical standard deviation (GSD) about 1.9. For dwelling and school hypothetically in the same location, the ratio is estimated about 0.7 with GSD about 1.5. We think that the methodology can be applied to structurally similar problems. The results could be used to create "conditional maps" of Rn concentration in dwellings, i.e., for example a map of probabilities that indoor Rn concentrations in dwellings exceed 100 Bq/m3, as function of Rn concentration in the local school.

Long-term measurements of radon, thoron and their airborne progeny in 25 schools in Republic of Srpska.

This article reports results of the first investigations on indoor radon, thoron and their decay products concentration in 25 primary schools of Banja Luka, capital city of Republic Srpska. The measurements have been carried out in the period from May 2011 to April 2012 using 3 types of commercially available nuclear track detectors, named: long-term radon monitor (GAMMA 1)- for radon concentration measurements (C(Rn)); radon-thoron discriminative monitor (RADUET) for thoron concentration measurements (C(Tn)); while equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) measured by Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS) were exposed in the period November 2011 to April 2012. In each school the detectors were deployed at 10 cm distance from the wall. The obtained geometric mean concentrations were C(Rn) = 99 Bq m(-3) and C(Tn) = 51 Bq m(-3) for radon and thoron gases respectively. Those for equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) were 11.2 Bq m(-3) and 0.4 Bq m(-3), respectively. The correlation analyses showed weak relation only between C(Rn) and C(Tn) as well as between C(Tn) and EETC. The influence of the school geographical locations and factors linked to buildings characteristic in relation to measured concentrations were tested. The geographical location and floor level significantly influence C(Rn) while C(Tn) depend only from building materials (ANOVA, p ≤ 0.05). The obtained geometric mean values of the equilibrium factors were 0.123 for radon and 0.008 for thoron.

Air ions as indicators of short-term indoor radon variations.

Diurnal variations in the air ion concentration are subject to changes in the radon concentration. In this experiment, the air ion and radon concentrations were simultaneously measured using two air ion detectors and two continuous radon detectors. The results of the indoor measurements revealed a strong correlation between the concentrations of positive air ions and radon (with a correlation coefficient greater than 0.9). The radon-to-ion concentration ratio changes with an increase in the radon concentration from a linear to a square-root relation. This correlation provides a means of using air ion measurements as a high-confidence indicator of changes in the radon concentration, especially for short-term measurements on the order of seconds or minutes, which is too short a measurement interval for conventional radon monitors. The use of air ions as an indicator of changes in radon concentration allows for investigation of the behavior of indoor radon and also allows radon to be used as a tracer gas for air mass exchange.