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A survey of indoor radon/thoron and their progeny concentrations was carried out in dwellings in the South West Khasi Hills district of Meghalaya, India. The survey was carried out using solid-state nuclear track detectors based on single-entry pinhole dosimeter and direct radon/thoron progeny sensors. The results are subjected to statistical analysis and discussed in the manuscript. The mean value of annual effective dose of the study region is estimated at 1.8 mSv.y −1. Seasonal variability and role of different indoor parameters are also discussed.

Uranium is renowned as a global contaminant, and attracts major concern with regards to the health risks involved because its nephrotoxicity. This paper discusses the development of a simple method to identify accumulated regions or localized sites of uranium within kidneys using the CR-39 plastic nuclear track detector. To demonstrate the proposed method, renal cryo-sections (5 μm-t) from Wistar male rats, subcutaneously administered with uranyl acetate (2 mg/kg), were prepared on day one after administration. Concerned sections were subsequently placed on CR-39, stored for 1.25 years, and then etched in a 7 M NaOH solution at 70°C for 3 h. α-tracks were then detected in the form of etch pits, corresponding to uranium, and also the tissue shape and structure were transferred as a roughness on the surface of CR-39. As observed, the proposed method served to facilitate simultaneous detection and identification of localized regions of uranium accumulation within kidneys.

The evaluation of different components of secondary radiation (charged fragments and neutrons) onboard ISS is described. Solid-state nuclear track detectors CR-39™ were applied for the measurements of short-range nuclear fragments, while the measurements of neutrons were carried out by means of thermo-luminescent dosimeters with various concentrations of 6Li and 7Li. The flux of charged secondaries and the gamma-equivalent neutron dose are presented in function of the low-LET dose in various modules of the Russian segment of ISS.

Indoor measurements of radon and thoron in Kuwait were conducted during the years 2015 and 2016. In this study, 65 dwellings were selected for the long-term radon-thoron survey using passive nuclear track monitors. The monitors (at least one) were used at various locations in the dwellings for 83-306 days. Some measurements were also repeated at the same locations in different seasons. This current study is a preliminary thoron survey with relatively small sample size. The results showed that the range of thoron concentration was from below the lower limit of detection to 35 Bq m-3, whereas the range of radon concentration was within 10-202 Bq m-3. Furthermore, 22% of the radon results exceeded the WHO radon reference level of 100 Bq m-3. The analysis of variance showed a correlation between indoor radon concentration and the season. However, the thoron measurements were rather limited and the values were low. In addition, the relationship was investigated between radon and thoron concentrations involving the floor levels and the type of ventilation systems used.

The radon survey of kindergartens has been conducted in Sverdlovskaya oblast during 2013-16. Indoor radon concentrations have been measured in 180 kindergartens in 21 villages and 10 towns. The LR-115 nuclear track detectors were placed in 560 rooms (three or four rooms per kindergarten) during 2-3 months. To obtain annual values, radon measurements were carried in the cold and warm seasons. The arithmetic and geometric means of annual indoor radon concentrations in rooms are 59 and 42 Bq/m3 respectively, GSD = 2.33. Analysis of the building factors affecting radon entry is presented. The detailed radon survey was performed in one kindergarten where exceeding of national action radon level was observed.

In the present study, the measurements of indoor radon, thoron and their progeny concentrations have been carried out in the Rajpur region of Uttarakhand, Himalaya, India by using LR-115 solid-state nuclear track detector-based time-integrated techniques. The gas concentrations have been measured by single-entry pin-hole dosemeter technique, while for the progeny concentrations, deposition-based Direct Thoron and Radon Progeny Sensor technique has been used. The radiation doses due to the inhalation of radon, thoron and progeny have also been determined by using obtained concentrations of radon, thoron and their progeny in the study area. The average radon concentration varies from 75 to 123 Bq m-3 with an overall average of 89 Bq m-3 The average thoron concentration varies from 29 to 55 Bq m-3 with an overall average of 38 Bq m-3 The total annual effective dose received due to radon, thoron and their progeny varies from 2.4 to 4.1 mSv y-1 with an average of 2.9 mSv y-1 While the average equilibrium factor for radon and its progeny was found to be 0.39, for thoron and its progeny, it was 0.06.

Concentrations of radon, thoron and their progeny inside the working place depend on the activity of radionuclides in the soil, building materials, atmospheric conditions, construction of the building, type of work and ventilation condition. Radon is a radioactive noble gas, and it is emanated from 226Ra present in earth crest and building material. Based on the type of work, construction of the building and ventilation condition, concentrations of radon, thoron and their progeny have been measured in 60 workplaces at 10 locations of Mysuru, Bengaluru and Kolar districts of Karnataka state using Solid-State Nuclear Track Detector technique. From the study, variations of radon, thoron and their progeny have been observed with the nature of work.

Indoor radon activity concentrations were measured in seven Museums of University of Naples, very old buildings of great historical value. The measurements were performed using a time-integrated technique based on LR-115 solid-state nuclear track detectors. The annual average concentrations were found to range from 40 up to 1935 Bq m(-3) and in 26 % of measurement sites, the values were higher than 500 Bq m(-3) which is the limit value of Italian legislation for workplace. Moreover, we analysed the seasonal variations of radon concentrations observing the highest average in cold weather than in warm.

The survey of natural radioactivity in Kosovo and Metohija involves 180 indoor Rn-220 measurements. They were performed either in living rooms or in bedrooms of 127 individual, rural type houses, using a passive method with application of CR-39 solid-state nuclear track detectors. Detectors were deployed at a distance of GT 10 cm from the walls. Values of all 180 measurements for 127 houses give an arithmetic mean (AM) of 132 Bq m(-3). The data for indoor thoron mapping arranged within 10 km x 10 km grid cells give an AM of 118 Bq m(-3) over AM grid cells. The distribution over individual data and the grid cells can be described as normal. About 19 % of the area of Kosovo and Metohija was covered by mapping. This study includes statistical analysis and discussion of factors, such as geogenic and seasonal, which possibly affect thoron concentration, as well as comparison with simultaneous radon measurements. 2nd International Conference on Radiation and Dosimetry in Various Fields of Research RAD and The 2nd East European Radon Symposium (SEERAS), May 27-30, 2014, Nis, Serbia

In recent years, elevated thoron concentrations were found in houses built of unfired clay. In this study experiments were carried out in 17 traditional and modern clay houses in Germany to obtain an overview of indoor thoron in such houses. Long-term measurements over an 8-week period were performed using a newly developed Unattended Battery-Operated Progeny Measurement Device (UBPM) for measuring thoron progeny. This instrument uses a high-voltage electric field to precipitate radon and thoron progeny on nuclear track detectors. Additional active and passive measurements of radon, thoron and their progeny were performed. The equilibrium equivalent thoron concentration was found to be between 2 and 10 Bq m(-3). Gas concentrations were found to be between 20 and 160 Bq m(-3) for radon and between 10 and 90 Bq m(-3) for thoron 20 cm from the wall. The thoron exposure contributes significantly to the inhalation dose of the dwellers (0.6-4 mSv a(-1)).

Radon is considered to be the main contributor to the worldwide population exposure to natural sources of radiation and so a lot of efforts have been made in most countries to assess indoor radon concentrations. Radon exhales from the earth's surface and is part of the radioactive decay series of uranium, which is also present in building materials. In this work, measurements of radon exhalation rates in building materials commonly used in the Iberian Peninsula have been carried out by using two different methods: active and passive techniques. In the first technique, the radon exhalation rate was measured following the radon activity growth as a function of time, by using a continuous radon monitor. The second technique is based on integrated measurements by using solid-state nuclear track detectors and a Spark Counter reading equipment. The results obtained by both measuring methods were found to be consistent.

In this paper, the evaluation of the dosimetric capability of a detector based on a CR-39 solid-state nuclear track detector coupled to a 1 cm thickness of PMMA radiator was made with the aim of understanding the applicability of this technique to personal and environmental neutron dosimetry. The dosemeter has been exposed to monoenergetic and quasi-monoenergetic neutron beams at PTB in Braunschweig, Germany and at Ithemba Laboratories, in Faure, South Africa, with peak energies ranging from 0.565 to 100 MeV. The results showed a response that is almost independent of the neutron energy in the whole energy range.

An extensive studies on the indoor activity concentrations of thoron, radon and their progeny in the granite region in the state of Karnataka, India, has been carried out since, 2007 in the scope of a lung cancer epidemiological study using solid-state nuclear track detector-based double-chamber dosemeters (LR-115, type II plastic track detector). Seventy-four dwellings of different types were selected for the measurement. The dosemeters containing SSNTD detectors were fixed 2 m above the floor. After an exposure time of 3 months (90 d), films were etched to reveal tracks. From the track density, the concentrations of radon and thoron were evaluated. The value of the indoor concentration of thoron and radon in the study area varies from 16 to 170 Bq m(-3) and 18 to 300 Bq m(-3) with medians of 66 and 82.3 Bq m(-3), respectively, and that of their progeny varies from 1.8 to 24 mWL with a median of 3.6 mWL and 1.6 to 19.6 mWL, respectively. The concentrations of indoor thoron, radon and their progeny and their equivalent effective doses are discussed.

Radon represents the most important contribution of population exposure to natural ionising radiation. This article presents the first indoor radon map in some regions of Romania based on 883 surveyed buildings in the Ştei-BăiŢa radon-prone region and 864 in other regions of Romania. Indoor radon measurements were performed in the last 10 y by using CR-39 nuclear track detectors exposed for 3-12 months on ground floor levels of dwellings. Excluding the Ştei-BăiŢa radon-prone region, an average indoor radon concentration of 126 Bq m(-3) was calculated for Romanian houses. In the Ştei-BăiŢa radon-prone area, the average indoor concentration was 292 Bq m(-3). About 21 % of the investigated dwellings in the Ştei-BăiŢa radon-prone region exceed the threshold of 400 Bq m(-3), while 5 % of the dwellings in other areas of Romania exceed the same threshold. As expected, indoor radon concentration is not uniformly distributed throughout Romania. The map shows a high variability among surveyed regions, mainly due to the differences in geology. The radon emanation rate is substantially influenced by the soil characteristics, such as the soil permeability and soil gas radon concentration. Since higher permeability enables the increased migration of soil gas and radon from the soil into the building, elevated levels of indoor radon can be expected in more permeable soil environments.

Radon measurements, as do any measurements, include errors in their readings. The relative values of such errors depend principally on the measurement methods used, the radon concentration to be measured and the duration of the measurements. Typical exposure times for radon surveys using passive detectors [nuclear track detectors, activated charcoal, electrostatic (E-perm), etc.)] may extend from a few days to months, whereas, in the case of screening methods utilising active radon monitors (AlphaGUARD, RAD7, EQF, etc.), the measurements may be completed quickly within a few hours to a few days. Thus, the latter may have relatively large error values, which affect the measurement accuracy significantly compared with the former measurements made over long time periods. The method presented in this paper examines the uncertainty of a short-term radon measurement as an estimate of the long-term mean and suggests a minimum measurement time to achieve a given margin of uncertainty of that estimate.

222Rn and. 220Rn levels have been measured using passive detector technique by employing time integrated solid-state nuclear track detector-based dosemeters in various types of houses at 10 different locations in and around Bangalore Metropolitan, India. The measured geometric mean concentration values of. 222Rn and. 220Rn levels in 200 dwellings of different types of construction were found to be 32.2±1.6 and 21.4±1.0 Bq m. -3, respectively. The dose rate received by the population of Bangalore ranged between 0.2 and 3.5 mSv y. -1 with an average and the geometric mean of 1.14±0.05 and 1.06 mSv y. -1, respectively. Overall, the result does not show much significant radiological risk for the inhabitants and the. 222Rn levels are well within the limits of global average concentration of 40 Bq m. -3. However, the. 220Rn levels observed were found to be higher than the global average of 10 Bq m. -3. © The Author 2012. Published by Oxford University Press. All rights reserved.

Extensive radon surveys have been carried out in many countries only in dwellings, whereas surveys in workplaces are rather sparse and generally restricted to specific workplaces/activities, e.g. schools, spas and caves. Moreover, radon-prone areas are generally defined on the basis of radon surveys in dwellings, while radon regulations use this concept to introduce specific requirements in workplaces in such areas. This approach does not take into account that work activities and workplace characteristics can significantly affect radon concentration. Therefore, an extensive survey on radon in different workplaces have been carried out in a large region of Italy (Tuscany), in order to evaluate radon distribution in workplaces over the whole territory and to identify activities and workplace characteristics affecting radon concentration. The results of this extensive survey are compared with the results of the survey carried out in dwellings in the same period. The workplaces monitored were randomly selected among the main work activities in the region, including both public and industrial buildings. The survey monitored over 3500 rooms in more than 1200 buildings for two consecutive periods of ∼6 months. Radon concentration was measured by means of passive nuclear track detectors.

An indoor radon survey of a total of 77 dwellings randomly selected in 10 districts in Oke-Ogun area of Oyo state, South-western Nigeria was carried out using CR-39 detectors. The CR-39 detectors were placed in the bedrooms and living rooms and exposed for 6 months and then etched in NaOH 6.25 N solution at 90 °C for 3 h. Mean concentrations amount to 255 ± 47 and 259 ± 67 Bq m(-3) in the living rooms and bedrooms, respectively. The lowest radon concentration (77 ± 29 Bq m(-3)) was found in Igbeti, whereas the highest was found in Okeho (627 ± 125 Bq m(-3)). The annual exposure of dwellers was estimated to fall

(238)U, (232)Th, (222)Rn and (220)Rn concentrations were measured inside various Moroccan black soap samples widely used by the Moroccan population in traditional baths (Hammans) by using both CR-39 and LR-115 type II solid state nuclear track detectors. The measured (238)U, (232)Th, (222)Rn and (220)Rn concentrations, respectively, ranged from (3.7 ± 0.2) to (11.7 ± 0.7) mBq kg(-1), (0.11 ± 0.01) to (0.32 ± 0.02) mBq kg(-1), (3.8 ± 0.2) to (11.6 ± 0.6) Bq kg(-1) and (0.10 ± 0.01) to (0.31 ± 0.02) Bq kg(-1) for the Moroccan black soap samples studied. The influence of pollution on the concentrations of these radionuclides inside the considered Moroccan black soap was investigated. A new dosimetric model for evaluating annual committed effective doses due to (238)U, (232)Th and (222)Rn to the skin of different age groups of the Moroccan populations from the application of the black soap samples studied was developed. The maximum total committed effective dose to the skin due to (238)U, (232)Th and (222)Rn from the application of unpolluted black soap samples 20 min per week by the Moroccan populations was found to be equal to (0.88 ± 0.05) μ Sv y(-1) cm(-2).

This paper deals with the results of the first-field use in the Balkans, i.e. Serbia and Republic of Srpska (Bosnia and Hercegovina), of a passive polycarbonate Mark II type and poliallyldiglycol carbonate (Cr-39) alpha track detectors sensitive to thoron as well as to radon. Both types of solid state nuclear track detectors were designed and supplied by National Institute of Radiological Sciences (NIRS), Chiba, Japan. The commercial names for these detectors which all have been field tested in Balkan rural communities are known as: UFO and RADUET passive discriminative radon/thoron detectors. No database of thoron and thoron progeny concentrations in dwellings in Serbia or Balkans region exist, and as a result, the level of exposure of the Serbian population to thoron and its progeny is unknown so far. 1st International Workshop on Environmental Thoron and Related Issues, May 19-22, 2010, Chiba, Japan

Three dosimetric properties of poly allyl diglycol carbonate (PADC) and their response to gamma irradiation are put forth. The variation of the optical absorption edge with the received dose can be used as a dosemeter for doses >500 kGy. The variationdielectric function is, to some extent, linear with dose logarithm but has a low precision. The fluorescence emitted from the irradiated PADC upon illumination by the 346-nm UV radiation intensifies the changes in the dielectric properties and shows an excellent dosimetric behaviour in response to gamma ray in both precision and simplicity of procedure. Results showed that this property could be used as a dosimetric properties for measuring doses between 100 Gy and 6 MGy.

Alpha and beta activities per unit volume of air due to radon ((222)Rn), thoron ((220)Rn) and their progenies were measured in the outdoor air at different locations in Morocco by using both CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs). In addition, the radon concentration was continuously measured in one location by using the methods with SSNTDs and AlphaGuard counter. The influence of the geological and meteorological conditions as well as phosphate and building material dust on the radon concentration in the outdoor air of the areas studied was investigated. The committed equivalent doses due to (218)Po and (214)Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of outdoor air. The annual effective dose due to radon short-lived progeny from the inhalation of outdoor air by the members of the rural population was estimated.

(222)Rn and (220)Rn, the immediate decay products of radium isotopes, are causative agents of lung cancer. (222)Rn and (220)Rn concentrations in houses with different floorings, roofs and walls and in different rooms of houses have been measured in Mysore city, Karnataka state, India, using solid-state nuclear track detectors. The radon and thoron concentrations in dwellings with granite floorings are found to be higher compared with other types. A correlation between the indoor radon concentration and dose in air from terrestrial gamma radiation is observed.

Alpha and beta activities per unit volume of air due to radon (222Rn), thoron (220Rn) and their progenies were measured in the air of natural caves by using CR-39 and LR-115 type II solid-state nuclear track detectors. Equilibrium factors between radon and its daughters and between thoron and its progeny were evaluated in the atmospheres studied.

Radon ( 222 Rn) and thoron ( 220 Rn) concentrations were measured in sixteen natural honey material samples collected from different regions in Morocco by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). The concentrations of these radionuclides were also measured in nectar solutions corresponding to the studied honey samples. The measured concentrations of 222 Rn and 220 Rn in honey samples ranged from (2.3 ± 0.2) to (8.1 ± 0.6) Bq.l −1 and (1.8 ± 0.1) to (3.9 ± 0.3) Bq.l −1 , respectively. Committed equivalent doses due to annual intakes of 222 Rn were evaluated in the human gastrointestinal tract compartments of adult members of the Moroccan populations from the ingestion of studied honey samples. The influence of the target tissue mass and activities due to 222 Rn on the annual committed equivalent doses in the compartments of the human gastrointestinal tract was investigated.

Makrofol Solid State Nuclear Track Detectors were used to study the (222)Radon concentration in dwellings of the Kars province in Turkey. Radon measurements were done for 3 months in 87 houses, selected as uniformly distributed in the area as possible. All values were seasonally corrected. In order to define the seasonal correction factors, the readings were taken in 12 homes for a 12-month period. A 1:100.000 scale geologic map of the region, prepared and published by the Institute of Mineral Research and Exploration (Ankara, Turkey), was used to present the radon results. Digitising, processing and integrating of the data were performed by using ArcView GIS. The results of the radon measurements in the study area range from 20 to 600 Bq/m(3), with 114 Bq/m(3) as average value. The results showed that the number of lung cancer deaths attributable to indoor radon exposure was estimated to be similar to 5.

The intercomparison measurements with Tn-Rn discriminative monitor were conducted at the Radon Laboratory of Nanhua University. The intercomparison results indicates that the Tn-Rn discrimination of most monitors (including the solid-state nuclear track detector of participant A and participant B, continuous monitors of RAD7 and RTM2100) keeps well in a wide range of the ratio of Tn to Rn. There are great differences of Tn measurement results among RAD7, RTM2100 and reference instrument. The discussion on the reason of these differences reveals the necessity of improvement on monitor calibration, Tn source make and the necessity of more international intercomparisons.

Inhalation of radon and its daughter products is the major contributor to the total exposure of the population to natural radiation. An indoor radon survey has been carried out in the state of Chhattisgarh (80.26 degrees N to 84.41 degrees N and 17.8 degrees E to 24.1 degrees E), India under the national coordinated radon project of the Department of Atomic Energy. In the frame of this project indoor radon concentration has been measured in 105 dwellings situated in different villages of Chhattisgarh state. Houses were selected for measurements to cover the most common type of houses generally existing in the rural areas. Measurements have been done on quarterly integrating cycle for one full year in each dwelling using radon cup dosemeter employing LR-115, type-II (pelliculable), solid-state nuclear track detectors. The gamma radiation level was also checked in each dwelling using a gamma survey meter. It was found that the annual average indoor radon concentration in these dwellings varies from 9.91 to 87.84 Bq m(-3) with overall mean value of 26.48 Bq m(-3). Gamma level in these rural dwellings varies from 14.84 to 26.56 microR h(-1) with mean value of 18.68 microR h(-1). We observed that the radon concentration is relatively higher in the houses where the floor is bare but relatively lower in those houses where the floor is tiled or cemented.

Mexico City, also called Federal District, covers an area of 1504 km 2 , and has more than 8 million inhabitants. It is located more than 2200 m above sea level in a zone of high seismic activity, and founded on an ancient lake. At present it is one of the most crowded and contaminated cities in the world, with thermal inversions. Chemical contaminants and aerosol particles in the environmental air are high most of the year. Due to these geological, environmental and socioeconomic conditions, Federal District presents very peculiar characteristics, which are important for understanding the distribution and measurements of indoor radon concentration. In this work the results of 3 year (1998-2000) measurements of indoor radon levels in the Federal District are presented. For the detector distribution and measurements, the actual political administrative divisions of the Federal District, consisting of 16 very well defined zones, was used. Nuclear track detection methodology was selected for the measurement, with a passive device close-end-cup system with CR-39 (Lantrack®) polycarbonate as the detection material, with one step chemical etching, following a very well established protocol developed at the Instituto de Fisica, UNAM. Calibration was carried out at the Oak Ridge National Laboratory, and verification at the Instituto de Fisica chamber. The results show that the arithmetical mean values of the indoor radon concentration for each region of the Federal District follow a non-homogenous distribution.

The dissolution characteristics of 232 Th from ThO 2 in the lung have been determined in an in vitro study. Two types of ThO 2 were examined to determine if the age of the material had any effect; an aged high-fired ThO 2 that had its progeny in secular equilibrium, and a recently recrystallised and high-fired ThO 2 in disequilibrium. The results show the amount of 232 Th that dissolved from the aged ThO 2 was approximately 10 times greater than the amount that dissolved from the recrystallised and fired ThO 2 , which was the result of recoil damage to the crystal structure of the aged material. A model based on nuclear track theory was developed to relate the size of the observed rapidly soluble fraction of 232 Th to the age of the material and its experimentally determined surface area.

Using the Raduet discriminative radon-thoron solid-state nuclear track detectors, a limited number of measurements were recently carried out about 1 m away from any wall and 1.5 m above the floor in different environments in Slovenia. The following thoron and radon ranges were obtained, respectively (Bq m(-3)): 33-700 and 25-4900 in 2 dwellings, 11-215 and 22-422 in 5 kindergartens, 21-368 and 40-4609 in 35 elementary schools, 47-1361 and 92-3280 in 4 hospitals, 4-37 and 10-153 in 9 spas and 800-880 and 4060-6870 in 1 karst cave (2 places). In case of thoron and radon concentrations lognormal distribution was confirmed, while the statistical relationship between them was weak.

The 222 Rn concentration level has been surveyed inside dwellings in the seven more important and populated cities of Mexico, and the results are presented in this work. The measurements were made for six months, covering winter and spring, the coolest seasons of the year in Mexico. More than a hundred dwellings in each town were chosen, selecting three groups of basic architectonic styles. Different factors affecting the potential 222 Rn concentration were considered in the study: construction materials, age of the dwellings, wall coverings, location of sites, and meteorological parameters such as indoor-outdoor temperature and relative environmental humidity. The passive integration of radon measurement method based on nuclear tracks was used. The closed end cup device, developed at the Institute of Physics of the University of Mexico, with CR-39 polycarbonate as material detector was chosen. The measurement methodology consists of the one step chemical etching process to develop the nuclear tracks and automatic track reading by a digital image analyser.

It is well established that neutrons cause significant biological damage because of higher LET. Therefore, a proper assessment of dose due to neutron exposure is essential. Various workers in the country and abroad have used Solid State Nuclear Track Detectors (SSNTDs) for recording doses due to neutrons. In the present study an attempt has been made to develop a novel approach to make these detectors angular independent by surrounding them with a water radiator. The response of CR-39 in this configuration under optimum electrochemical etching at elevated temperature has been found to be nearly angular independent and thus can be used for personnel neutron monitoring as it overcomes most of the practical problems previously experienced in the development of a multidirectional dosemeter.

In order to assess the natural radioactivity in a developing country with a hot climate, radon concentrations were measured inside 88 dwellings, 34 workplaces, and two underground non-uranium mines belonging to the Brazilian states of Rio Grande do Norte and Ceara. The determinations were performed in the selected settings using solid state nuclear track detectors which were exposed for a period of time of the order of 180 days between the months of June 1995 and April 1996. The indoor radon level was found to range from 3.2 to 140 Bq.m -3 with geometric means of 12.4 Bq.m -3 for houses, and 15.1 Bq.m -3 for workplaces (schools, hospitals, offices, and so on). These relatively low values are probably related to elevated ventilation rates which are typical of edifices located in Northeast Brazil. The average radon concentrations in the surveyed scheelite mines were 153 and 503 Bq.m -3 , respectively.

It is shown that a confocal laser scanning microscope can be used for 3-dimensional visualisation of chemically etched tracks in CR-39 if (a) the tracks are dyed with a fluorophor and (b) the tracks are viewed directly with an oil immersion objective. Two dyeing methods are described. This new method of track visualisation has potential applications in the development of track formation models and offers new possibilities for spectrometry and neutron capture radiography with nuclear track detectors. Currently available procedures for track analysis are briefly described and ideas regarding further developments are presented.

A digital image analysis system (DIAS) is described for evaluation of etched nuclear damaged tracks in plastics. Early efforts were directed at automated measurements of the ellipticity and area of etch tracks in CR-39 track areas related to particle energy. Discrimination was made between etch tracks from alpha particles emitted by 239 Pu, 241 Am and 244 Cm with good linearity of response for time of exposure. The DIAS could also discriminate between etched alpha particle tracks and etched surface scratches and other chemical artefacts. Eventually, it is hoped to expand the image enhancement and shape discrimination capabilities to measure the size and activity of 'hot' alpha-emitting particles.

CR-39 solid state nuclear track detectors were used to measure radon concentration in a city in the eastern part of Al-Qaseem province in Saudi Arabia. The dosemeters were distributed over 58 houses. Results obtained show that the mean radon concentration in this area is 67 ± 8 Bq.m -3 which is higher than the level reported in former studies in other parts of the country, but is still within normal limits. It is also found that, in general, the level in lower floors is higher than that in upper ones in all houses. It is believed that the high radon level in this part of the country may be attributed to its geographic location.

Indoor radon measurements were performed in public schools at different locations, as well as in dwellings of Algiers. Indoor radon was measured by means of solid state nuclear track detectors (LR-115) in twelve town locations and in twenty four schools, with two schools in each location. The average radon concentrations in schools, in dwellings and outdoors was 25.6, 29.8 and 11 Bq.m -3 , respectively. The estimated average effective dose equivalent for the school pupils was 1.28 mSv.y -1 (with occupancy factors of 0.6, 0.2 and 0.2 for home, school and outdoors, respectively). This paper describes the methodology adopted and discusses the results obtained.

In the National Board of Nuclear Safety and Radiation Protection of the GDR solid state nuclear track detectors (SSNTD) have been used routinely both for individual neutron dosimetry and for long-term measurements of radon and radon daughter products in flats and in the environment. For neutron monitoring a fission track dosemeter is used for the simultaneous response to fast and intermediate neutrons, using Makrofol KG as a detector. The long-term dosemeter for registering radon and radon daughter products is based on the diffusion chamber principle. Makrofol DE 1-4 of 300 µm thickness is used as the detector. Detector evaluation and calibration methods are described in detail and detection limits are stated. In addition, a screening measuring method based on CR-39 is presented, allowing the rational performance of long-term measurements by radon diffusion chambers.

For a single ion hit facility built to irradiate specific targets inside biological cells, it is necessary to prove that the ions hit the selected targets reliably because the ion hits usually cannot be seen. That ability is traditionally tested either indirectly by aiming at pre-etched tracks in a nuclear track detector or directly by making the ion tracks inside cells visible using a stain coupled to special proteins produced in response to ion hits. However, both methods are time consuming and hits can be verified only after the experiment. This means that targeting errors in the experiment cannot be corrected during the experiment. Therefore, we have developed a fast online hit verification method that measures the targeting accuracy electronically with a spatial resolution of +/-1 microm before cell irradiation takes place.

In 1992 a living area was discovered in Hungary where the radon exhalation rate was extremely high. One of the questions asked was whether this level of concentration has existed for a long time. Because radon daughters are continuously embedded on the surface of glass sheets by alpha recoil, it means that old glass sheets can 'remember' past radon concentration levels via long-lived decay products. Traditionally 210 Po (daughter of 210 Bi) surface activity concentration is measured with an ionisation chamber or solid state nuclear track detectors (SSNTD). A new and fast radiochemical method has been developed to investigate surface beta activity concentration of 210 Bi. The new method was checked by comparing it with SSNTD. It is concluded that the radon concentrations in the radon prone area where the glass samples were analysed have not changed by more than a factor of two over the last 8-55 years.

The concentrations of indoor 222 Rn have ben determined in several areas of the Campania region (south Italy), where there is the highest natural radioactivity in Italy. The technique of charcoal canisters was used for measurements of a few days and nuclear track detectors (CR-39 and LR-115) for several months measurements. Check measurements for the techniques adopted were done with a continuous monitor based on a silicon alpha detector and focusing electrostatic fields. The houses built with volcanic materials, such tuff and pozzolana, have shown an activity approx. 60% higher than houses built with typical industrial materials, like bricks. Of about 300 measurements 80% of the values are 400 Bq.m −3

Indoor radon is a potential health hazard for the general public, especially in buildings with poor ventilation. This realisation has sparked a flurry of scientific activity aimed at measuring radon concentration levels and assessing the nature and extent of risks involved. In this regard a variety of dosemeters have been developed and used in surveys of radon concentration measurements. In this article the passive dosemeters which are based on solid state nuclear track detectors are reviewed. The principle of passive dosimetry and the factors affecting their performance are discussed. The characteristics of SSNTD materials in relation to their behaviour under different environmental conditions are tabulated and discussed

Radon concentrations have ben measured in bedrooms, sitting-rooms, kitchens and TV lounges in some houses in the cities of Lahore, Islamabad and Rawalpindi using CN-85 solid state nuclear track detectors in box type dosemeters. In the city of Lahore, bedrooms were found to have higher (average) radon concentrations (=93 Bq.m −3 ) compared with those (=20 Bq.m −3 ) observed in TV lounges. A similar trend was observed in the cities of Islamabad and Rawalpindi, where the average radon concentration values of 83 Bq.m −3 and 12 Bq.m −3 were found in bedrooms and TV lounges, respectively.

This work describes the evaluation of CR-39 for use as a fast neutron microdosemeter, and provides some insight as to the feasibility of such use. The material was calibrated by irradiation with protons and alpha particles accelerated by a tandem electrostatic accelerator. Proton energies of 10, 6, and 3 MeV and alpha particle energies of 15, 10, and 7 MeV were used, at angles of incidence from 0 to 85 deg. The critical angle, normal incidence diameter, and track etching rates versus linear energy transfer (LET) were obtained from these measurements. A method for extracting a LET spectrum from CR-39 irradiated in-phantom with the fast neutron beam was developed and these results are compared with LET spectra measured by a 1.27 cm diameter Rossi chamber.

Three experiments were carried out at the Indoor Air Quality Research House (IAQRH) at Lawrence Berkeley Laboratory, University of California, to study the effect on the radon progeny of operating a mixing fan. At the beginning of every experiment, about 15 kBq.m-3 of radon was injected into a 36 m3 ordinary room. Measurements were conducted with three different aerosol particle concentrations of about 102, 104 and 105 per cm3. Real-time measurements of radon and progeny concentrations, particles and environmental parameters, were made throughout the experiments. Measurements of plated out activity on the surfaces of internal walls of the room and fan blades were measured directly by filter papers and CR-39 nuclear track detectors placed on the surfaces. The ratio of plated out activity to the total progeny activity in the room varied from 17% to 84%, in inverse relation to the particle concentrations. More than 99% of the plateout activity was found on walls and less than 1% on the fan blades.