UTFPR, Federal University of Technology - Paraná, Av. Sete de Setembro, 3165, Curitiba, , Brazil;

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1 Sergei A. Paschuk 1 ; Janine Nicolosi Corrêa 1 ; Jaqueline Kappke 1 ; Flávia Del Claro 1 ; Allan F.N. Perna 1 ; Marilson Reque 1 ; Valeriy Denyak 2 ; Hugo R. Schelin 2 1 UTFPR, Federal University of Technology - Paraná, Av. Sete de Setembro, 3165, Curitiba, , Brazil; 2 IPPPP, Pelé Pequeno Príncipe Research Institute, Av. Silva Jardim, 1632, Curitiba, , Brazil

2 INTRODUCTION

3 INTRODUCTION The present work describes the principal results concerning the radon and radium measurements at Curitiba (PR) urban area during the last decade. The monitoring was performed in cooperation with the Center of Nuclear Technology Development (CDTN/CNEN). For radon in air activity measurements, it was used polycarbonate etched track detectors such as LEXAN and CR-39, mounted in diffusion chambers. For soil gas measurements, the experimental setup was based on the Professional AlphaGUARD Radon Monitor connected to the Soil Gas Probe, filter vessels and air pump (AlphaPUMP), following the recommended protocols elaborated in the Soil-Gas Radon Intercomparison Measurements performed at different Countries of the world.

4 INTRODUCTION In the case of radon tests in drinking water, the experimental setup was based on the AlphaGUARD Radon monitor and Electronic Radon Detector RAD7 connected to a special kit of glass vessels through the air pump. The obtained results permitted to identify few dwellings where radon concentration in air was found bigger than 600 Bq/m3, that is considered as the action level by most of the European Community and the World Health Organization (WHO). In the case of well water, collected samples presented the average Rn-222 activity of about 60 Bq/L, that is 6 times bigger than the maximum level recommended by USEPA. Some artesian wells presented radon activity of almost 200 Bq/L. More over, almost all water samples presented the radioactivity of radium (Ra-226) salts bigger than the upper limit for global alpha radioactivity of potable water established by the Norms and Regulation of the Brazilian Ministry of Health.

5 INTRODUCTION The 222 Rn is entering and mixing with the atmosphere of a dwelling being released from several sources, including its release and emanation from basement soil through breaks in the foundation, which is considered as principle. The ground waters as well as the construction materials have to be mentioned among other causes of radon entry in air of the dwellings. Building materials as source of radon in air are the subject of many studies [1-5] performed around the world, which resume in the conclusion that soil contribution is about 10 times bigger than originates from common construction materials with high degree of compaction, such as stones, concrete and masonry bricks. Nevertheless, the diffusion of 222 Rn from the building materials may contribute significantly to the radon concentration in air in the case where, for example, the used concrete or masonry bricks are manufactured from materials that contain substantial quantity of natural radioactive elements.

6 INTRODUCTION Due to its solubility in water, high levels of 222 Rn are found in groundwater and are correlated with the occurrence of high levels of 226 Ra in igneous bedrock. Crystalline rocks, especially granite, could be a source of high levels of radon comparing with sedimentary rocks, sandstone or sand and gravel that usually are associated with lower levels of exhaled radon. The resume of studies performed by European countries [6] show that the average radon concentration level of radon in surface water is below 1 Bq/L, but the waters extracted from sedimentary rock aquifers present values of radon activity within 1 and 50 Bq/L. Another results of that study show that water from dug wells usually has radon activity that varies from 10 Bq/L to 300 Bq/L comparing with water from crystalline rocks where radon activity levels usually are of 100 Bq/L - 50,000 Bq/L. Present knowledge concerning the factors that affect the entry of 222 Rn in the internal structures of dwellings has been significantly improved during the development of the analysis and calculations involving the simplified model for houses and masonry buildings cited in the UNSCEAR Annual Reports on the Effects of Atomic Radiation (1988 and 1993) apud UNSCEAR [7].

7 INTRODUCTION In general, the entry of radon into the air of dwellings is affected by barometric pressure, ambient and outdoor temperature, differential pressure, wind speed, etc. The amount of radon released from water is subject of its prime soluble concentration, the quantity of water consumed during some domestic activities such as bathing, cooking and washing, the temperature of the water and the size of water to air surface area, etc. Rather complete review of studies of physical, geological and meteorological factors that influence the indoor 222 Rn concentrations and its progeny can be found in [8]. Rather big variety of norms and regulations can be found in the literature. For example, the documents of the International Commission on Radiological Protection (ICRP) [9] state that the limit for indoor radon activity within the dwelling environment has to be below 200 Bq/m 3. The houses with radon concentration in air between Bq/m 3, has to be observed and monitored and when radon concentration is found between Bq/m 3 some remediation measures have to be taken. This document is considering the radon activity in air bigger than 600 Bq/m 3 as intervention level.

8 INTRODUCTION The documents of the US Environmental Protection Agency (EPA) [10] suggest practical intervention in residence where the concentration of radon reaches 148 Bq/m 3, which coincide with conclusions of the World Health Organization report [11] that worldwide indoor average of radon remains below 148 Bq/m 3 that is below 200 Bq/m 3 recommended by UNSCEAR [7]. In Brazil for evaluation of radiation expose risks as well the necessity of interventions, the National Nuclear Energy Commission (CNEN) in the Regulatory Position 3.01/007 [12] recommends that generic level of annual dose for general public cannot exceed 10 msv/year, which corresponds to the maximum of radon activity in air of 300 Bq/m 3 in agreement with recent evaluation performed by the ICRP [13].

9 INTRODUCTION Considering the impact associated with radon activity in air on human health, many countries around the world spend significant efforts and resources with radon monitoring, mapping, mitigation measures together with a wide range of activities and intensive research aimed at limiting human exposure to radon. Frequent results of the studies concluded in Europe and United States have found the radon concentration levels between 2,000 and 50,000 Bq/m 3, which is bigger than recommended acceptable level [13-17] of 148 or 200 Bq/m 3. The surveys concluded in Sweden, Canada, and the United States [1] revealed very high incidence of elevated radon and its progeny levels in ordinary houses. Unfortunately, the quantity of national result concerning this subject is insufficient. Table 1 presents some results of several studies performed in different regions of Brazil concerning indoor radon concentration. It can be observed that the average concentration of radon in the monitored regions of Brazil does not significantly exceed the value of 200 Bq/m 3 following the conclusion of the World Health Organization report [11]. At the same time, it can be seen that some data are significantly exceeded the recommended limits of radon-inair in dwellings [7]. Table 2 shows the results of some measurements of radon concentration in water samples from different regions of Brazil. It can be observed that the radon activity in studied water ranges within a fairly extensive limit that is bigger in some cases than the upper limit of 11.1 Bq/L for 222 Rn concentration in drinking water proposed by EPA [3].

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12 MATERIALS AND METHODS For the measurements of radon ( 222 Rn) activity in air of dwellings in the Paraná St., it was used the experimental setup based on passive track etch detectors CR-39 and polycarbonate films prepared from LEXAN that were installed in diffusion chambers protected with glass microfiber filters. The diffusion chambers of the model described in [33] have a sensitive volume of 7.1 cm³ in the form of a semisphere with 3 cm in diameter covered by a hollow cap for the entrance of external air. The cavities in the cap are covered by glass microfiber filter to restrain the entrance of dust and aerosols. Figure 1 shows the general view of the diffusion chamber used in the measurements. To decrease the plate-out of the 222 Rn decay products at the surface of CR-39, the diffusion chamber is made from carbon fiber composite plastic with high electrical conductivity. Thus, the plate-out of decay products of 222 Rn mainly occurs at the wall surface of the chamber. More over, the semi-spherical format of the chamber provides a better transport of the radon decay product toward the wall and their better absorption there.

13 MATERIALS AND METHODS Figure 1. General view of the diffusion chamber used in radon monitoring

14 For the latest measurements of radon in air it was chosen CR-39 track etch detector, which is very sensitive to alpha particles. It was chosen due to its stability, high optical transparency and accumulated previous experience in chemical development of alpha particle tracks. CR-39 detectors are widely used in numerous radon long-term measurements and monitoring [35-38]. In the case of this type of detector, chemical attack and alpha particle track development was performed using 6.25M sodium hydroxide (NaOH) solution and ethanol (2%) during 14 hours at 70 C. Considering rather small size of obtained tracks, in this particular case their counting was conducted manually using the optical microscope with magnification of 100x and glass overlay mask, which permitted to identify the CR-39 surface area of 1cm 2. Very special attention was focused in detector calibration and background measurements. In the case of LEXAN thin film the calibration performed at the Institute of Radiation Protection and Dosimetry (IRD/ CNEN), where the efficiency of 70% was obtained for the density of alpha particle tracks about 13.8 cm 2 per exposure day and per kbq/m 3 of radon concentration [5]. In other words, such track density in the developed (etched) detector guarantees that 70% of the detected events will not be superposed and could be easily identified and counted. Following this recommendation and considering the expected radon concentration levels in air within 200 Bq/m 3 and 2000 Bq/m 3 the exposition time was estimated. The calibration of CR-39 films was conducted in collaboration with the Center for Development of Nuclear Technology (CDTN/CNEN) at the facility of the National Institute of Radiological Sciences (NIRS) in Japan where 30 diffusion chambers with mounted CR-39 detectors were exposed within controlled Environmental Storage Room in the atmosphere with varied concentrations of 222 Rn. After that, the exposed detectors were returned to the laboratories of CDTN and UTFPR where they were etched and read. The comparison between radon activities used for calibration and obtained number of alpha particle tracks together with statistical errors resulted in value of (405±30) Bq cm 2 h m -3 that has to be multiplied by the density of the counted alpha particle track per 1 cm 2 and per hour of exposition of CR-39 detector to receive the radon activity concentration in studied dwelling.

15 MATERIALS AND METHODS Studied construction materials have been submitted to the instant measurements of radon concentration using AlphaGUARD Professional detector (SAPHYMO). These measurements were carried in the Laboratory of the Ionizing Radiations of Federal University of Technology Paraná (UTFPR) as well as in the Radon Laboratory from the Institute of Radioprotection and Dosimetry (IRD, CNEN) where the samples of construction materials were stored inside an acrylic container (sealed up chamber) connected to the instant AlphaGUARD detector. Some general views of these measurements can be seen in Figure 2. For 222 Rn concentration measurements related to different construction materials as well as for the studies of Rn emanation and its reduction, the cell chambers with internal dimensions of approximately 60 x 60 x 60 cm 3 have been built using the ceramic clay bricks and concrete blocks. This construction was performed within a protected and isolated laboratory environment to maintain the air humidity and temperature stable. The details of cell-house construction can be seen in Figure 3. During the radon long term measurements the cell chambers were sealed by the wooden caps.

16 MATERIALS AND METHODS Figure 2: (a) Some samples of construction materials, (b) AlphaGUAR D detector and (c) the construction materials stored in acrylic chambe r. Figure 3: Cell chambers built from concrete and ceramic blocks.

17 MATERIALS AND METHODS In these measurements the water samples of 100mL were collected from wells at Curitiba urban area and submitted to analysis using the kit of glass vessels (Aqua KIT) connected to instant radon detector AlphaGUARD (SAPHYMO), that is also suitable for continuous monitoring of radon concentrations in the range of 2 2*106 Bq/m³. Some general views of the experimental setup used in those measurements are presented in Figure 4. Water samples were removed from the depth of about 1.5 m below the level of well water surface using 1000 ml PET bottles in the well. Completely filed PET bottles were tightly closed to prevent the entry of air into the bottle as well as to prevent the release of radon from it. The sealed samples were transported to the Laboratory of Applied Nuclear Physics of the Federal University of Technology Paraná (UTFPR, Curitiba, Brazil) to be submitted with minimum delay to the radon concentration measurements. When the time delay between the sample collection and its measurements was significant, the correction was introduced taking into account the time interval between the water sampling and the activity measurements and the decay constant for 222Rn.

18 MATERIALS AND METHODS Figure 4: General view of Alpha GUARD detector together with Aqua Kit prepared for the measurements of 222 Rn in well water.

19 20 Model Equation DecaimentoRNRa ( User) A2=A1o*(1-exp(-t/( 3.84*24)))+A2o*ex p(-t/(3.84*24)) Concentração (Bq/L) Reduced Chi-Sqr Adj. R-Square Value Standard Error Concentração A1o Concentração A2o Tempo (horas)

20 MATERIALS AND METHODS In the case of 226 Ra activity measurements in bottled mineral water available in the market of Curitiba Brazil, the experimental setup was based on the Professional Radon Monitor RAD7. The measurements were performed when 222 Rn in water samples reached the secular equilibrium. For this purpose, collected water samples were stored in hermetic bottles of 250 ml during days before the measurements. The RAD7 Manual suggests two specific protocols for the measurements of radon activity in water: the Wat-40 and Wat250 for the sample volume of 40 and 250 ml, respectively. Initially these protocols consist of a water sample s aeration stage, which takes place for five minutes. After that, the equipment uses 4 cycles of 5 minutes each one to measure the 218 Po activity within sampling cavity and to recalculate in 222 Rn activity concentration [41].

21 Therefore, for measurements of low activity samples, one of the most important questions is the radon concentration in the system air before aeration (background). One of the suggestions given in the RAD7 RAD H 2 O [41] manual is to use the external laboratory air to fill the system before measurements. As the number of measurements of the laboratory air was performed and the results show that the value of the background reaches hundreds of Bq/m 3 and the error of its determination with the Wat250 protocol, proposed in the manual as the basic protocol for low activity measurements, also reaches hundreds of Bq/m 3. With such a level of background and associated errors it is not possible to perform the measurements of low activity of water samples. To decrease the background value activated charcoal filter was used to clean the laboratory air before the measurement. All measurements were performed with an enclosed volume of air. To avoid the contact of the internal detection system with the laboratory air, 5 tap connectors were installed at each point of interest as it is shown in Figure 5. Using modified experimental setup of connections it was possible to reach the error of Bq/m 3 measuring the 226 Ra activity in the distilled water with the protocol WAT250. This result is not satisfactory for concentration measurement of about 100 Bq/m 3. Considering that the main source of this error is the uncertainty in the background determination and repeating the protocol WAT250 four times we succeeded to achieve the background error of the order of 50 Bq/m 3. To reduce more the error value it is necessary to change the protocol and to increase the measurement time significantly.

22 MATERIALS AND METHODS Activated Charcoal 5 4 DRIERITE 3 RAD7 Detector 1 2 Water Sample Figure 5: General view of RAD7 detector and modified setup of connections.

23 MATERIALS AND METHODS Measurements were performed at Curitiba urban area following the results concerning the high concentration levels of radon in samples of drinking water from artesian wells or, in some cases, obtained high concentration levels of radon inside the dwellings. In all cases the tests were performed at the native (rough) soil excluding the terrains submitted to strong grading and earth-moving. The survey was performed using the Professional Radon Monitor (AlphaGUARD) connected to the Soil Gas Probe through the air pump and filter system. The general view of the AlphaGUARD detector during the measurements can be seen in Figure 6. For air sampling and radon concentration measurements in the soil gas it has been developed steel probe and auxiliary drill. Geometrical parameters of the probe and drill are: total length 1400mm, drill and probe external diameter 35mm, internal probe diameter 22mm, estimated internal volume of the probe 0.348L, the depth of probe penetration in the soil 1000mm.

24 MATERIALS AND METHODS Figure 6: AlphaGUARD Detector (SAPHYMO) in measurements with Soil Gas Probe.

25 CONCLUSIONS It can be concluded that the obtained values of radon activity in dwellings and in workplaces of Curitiba urban area are within the normal range established by International norms and regulations that were discussed previously. No one of the investigated places requires any sort of mitigation measures. Comparing the obtained experimental results with similar studies performed in other Brazilian states (mainly at São Paulo, Minas Gerais and Rio de Janeiro) [5, 18-27] it can be concluded that the obtained values of measured radon concentrations are very similar.

26 CONCLUSIONS The present studies show rather high concentration levels of 222 Rn in well water from the region of Curitiba. Moreover, about 70% of the investigated water samples presented radioactivity of radon bigger than 11.1 Bq/L, recommended by the United States Environmental Protection Agency (EPA) [15], which requires the implementation of mitigation measures for radon reduction in drinking water. It should be noted that the main source of 222 Rn in water is soil and not soluble 226 Ra compounds. The only sample of water where obtained 226 Ra activity was found of 6.76 Bq/L is an isolated case and requires further investigation. At the same time, it should be concluded that almost all investigated samples of water presented the level of radium activity concentration bigger than the maximum level of global alpha radioactivity for drinking water established by the Norm of the Brazilian Health Ministry [43], which requires some special attention during the licensing for artesian water drilling.

27 CONCLUSIONS Evidently further development of radon monitoring in air, water and soil is required due to the progress of building materials, rather quick grow of urban areas, changes of ventilation technologies and population habits. As an example it has to be mentioned the air conditioning ductless (split) units, which offer rather significant energy saving benefits but their installation and usage makes the dwelling more airtight interrupting all natural ventilation that can stimulate the radon accumulation in houses and buildings. The continuation of radon monitoring requires the attention of local and federal authorities and their financial support of this work since the biggest part of the used detectors and materials are imported and have rather high costs. Evidently, national norms and regulation concerning radon activity in air and water have to be created and approved establishing, at least, the maximum activity levels of radon in air of dwellings and water consumed by the Brazilian population.

28 ACKNOWLEDGMENTS The authors are very thankful to CNPq, CAPES, CNEN, and Fundação Araucária (Paraná St.) for their financial support of this work, as well as to colleagues from the Institute of Radiation Protection and Dosimetry (IRD/CNEN) and from the Center of Nuclear Technology Development (CDTN/CNEN) for their collaboration, positive discussions and assistance in the measurements.

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