Indoor radon measurement in Izmir Province,Turkey

In 2013, an extensive study was performed in a total of 117 locations in Izmir province and indoor radon levels were measured using the alpha track etch integrated method with LR-115 detectors. As the maps are more practical to interpret the results of radiological survey, the distributions of indoor ²²²Rn activities in four most densely populated districts of Izmir were mapped in detail. It is seen that the estimated average radon concentration level (210 Bq m^?3) determined in Izmir province was almost three times higher than the mean value for Turkey (81 Bq m^?3). Exposed annual effective dose equivalents for Izmir province were estimated in the range of 0.7 to 12.3 mSv year^?1 with a mean of 5.3 mSv year^?1. In this study, it is pointed out that indoor radon concentration was affected by the age of the building and height above the ground.     

Natural radioactivity and radon exhalation rates in building materials used in Egypt

Natural and fabricated building materials commonly used in Egypt were surveyed for both natural radionuclides content and radon exhalation rate. These include raw as well as construction products. Concentration of natural radionuclides in all samples were determined by γ-ray spectroscopy with HPGe detector. For Radon exhalation rate measurements of fabricated samples, the seal can-technique has been applied using CR-39 plastic track detectors. The radiation hazard indices of the total natural radioactivity in the studied samples were estimated. The results were compared with the corresponding results of different countries and were found to be lying within the average world values. Radon exhalation rate in the studied samples varied between 197 (cement brick) and 907 mBq m⁻² h⁻¹ (blast furnace slag cement). The results of this survey suggest that, using blast furnace slag cement for pre-coating the internal walls of buildings in the Urban region of Egypt is discouraged and the replacement of clay brick by cement brick will be more healthy for the public.     

Soil radon time series: Surveys in seismic and volcanic areas

Soil radon surveys have been performed in a long term monitoring basis with SSNTD (LR 115 type II), in order to observe possible fluctuations due to high magnitude seismic events and volcanic eruptions. Five-year radon time series are available in stations located in an intense seismic zone located along the Pacific coast of Mexico. The series analyses have been performed as a function of the local seismicity and geological characteristics. A discussion is intended to explain the lack of biunivocal relation between single radon peaks and earthquakes for the long term monitoring data using SSNTDs. Examples of short term radon anomalies obtained with continuous probes are also discussed as a function of local earthquakes and meteorological perturbations. Additionally, complementary results from recent changes in the activity pattern of an active volcano indicate that degassing process induced anomalous soil radon emanation correlated with the volcanic activity changes.     

A passive radon dosimeter based on the combination of a track etch detector and activated charcoal

The aim of this work is to test a combination of a Makrofol track detector with a new type of charcoal (Carboxen-564) to design a personal radon dosimeter. The intention is to use this dosimeter as a personal radon dosimeter to measure the monthly radon exposure in workplaces, especially when the occupancy is not ecactly known. The proposed combination was exposed to low and high concentrations of radon in a large range of relative humidity (RH). For the optimal layer thickness, a charcoal bed of 2.2 mm, a specific track density of 5.1 tracks cm⁻²/kBq h m⁻³ was obtained. For a monthly working exposure (170 h) at an average radon concentration of 100 Bq/m³, this means 87 tracks/cm² or 10 times the background of the Makrofol detector, with a statistical uncertainty of 15%.     

Studies on radon adsorption characteristics of different charcoals used as amplifiers for the track detectors

Ten sorts of charcoals were studied regarding their use as amplifier in the design of a personal dosimeter. It consists of a combination of a Makrofol detector and activated charcoal. The calibration factor for the Makrofol using the charcoals as an amplifier is about ten times higher comparing with an exposure without charcoal. The best results were obtained with Carboxen 563. The background radioactivity of charcoals must also be considered in the dosimeter's design.     

Development of a reader for track etch detectors based on a commercially available slide scanner

NRPB has operated a routine neutron personal dosimetry service based on the electrochemical etch of PADC elements since 1986. Since its inception it has used an automated reader based on a video camera and real time analysis. A new and more powerful replacement system has been developed using a commercially available photographic slide scanner. This permits a complete image of the dosemeter to be grabbed in a single scan, generating a 2592x3888 pixel file which is saved for subsequent analysis. This gives an effective pixel size of 10x10 μm with an image of the entire dosemeter in one field of view. Custom written software subsequently analyses the image to assess the number of etched pits on the dosemeter and read the detector identification number (code). Batch scanning of up to 40 detectors is also possible using an autofeed attachment. The system can be used for electrochemically etched tracks for neutron detectors and chemically etched tracks for radon detectors.     

Properties and structure of cesium phosphate glasses

A series of Cs-phosphate glasses, xCs₂O(1−x)P₂O₅, where 0?x?0.60, were prepared. The glass transition temperature (T_g) decreases with the initial addition of Cs₂O to P₂O₅, from 637 K at x=0 to 472 K at x=0.16. There is little change in T_g with further additions of Cs₂O up to x=0.60. The ³¹P magic angle spinning nuclear magnetic resonance (MAS NMR) spectra show that Cs₂O additions systematically convert the cross-linked ultraphosphate network of ν-P₂O₅ to a chain-like metaphosphate structure as x approaches 0.50. The ¹³³Cs MAS NMR spectra show a 90 ppm increase in isotropic chemical shift (δ_iso) with increasing Cs₂O content, which indicates a decrease in the average electron density around the Cs⁺ ions, more covalent Cs-O bonding, and a shorter average Cs-O bond length. The physical properties and spectroscopic results are interpreted using a structural model that considers the effects of composition on the average coordination environment of Cs⁺ ions.     

SPECT均匀衰减投影数据的反演公式

依据近年来公开发表的有关单光子发射断层成像(SPECT)成像技术的文献,探索SPECT均匀衰减投影数据的反投影问题.主要采用指数型拉动变换的性质和构造特殊函数—–δ函数的方法,进而应用δ函数的特殊性得到了一个精确的反演公式.结果表明,由这种方法得到的反演公式能够更加有效和精确地实现图像的重建.     

Measurements of the size distribution of unattached radon progeny by using the imaging plate

The size distribution of unattached radon progeny is an important parameter for an accurate estimation of the internal dose of radon exposure. In this study, a new measuring system was developed to evaluate the size distribution of unattached radon progeny in air. In the system, airborne radon progeny were collected with a newly designed graded screen array (GSA), the activity concentrations were measured by using the imaging plate technique, and the size distribution of unattached fraction was retrieved by using an iterative nonlinear algorithm. The simulation results indicated that the collection characteristics of the new GSA system were well agreed with other systems. Test experiments showed that the activity-weighted median diameters (AMD) for unattached ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi were 0.89 ± 0.11 nm, 0.96 ± 0.13 nm and 1.01 ± 0.25 nm in a particle-free radon chamber, and the distribution changed with different concentrations of particles. As multiple measurements can be simultaneously carried out with a single IP, the new technique is considered as an optional and useful way to measure the size distribution measurement of unattached radon progeny.     

Indoor radon survey in Eastern Sicily

Inhalation of radon (Rn-222) and its progeny is one of the most significant sources of natural radiation exposure of the population. Nowadays, high radon exposures have been shown to cause lung cancer and many governments all over the world have therefore recommended that radon exposures in dwellings and indoor workplaces should be limited. Radon levels in buildings vary widely from area to area depending on local geology. This paper presents the results of a long-term survey of radon concentrations carried out from 2005 till 2010 in schools and dwellings of Eastern Sicily, using the solid-state nuclear track detector (SSNTD) technique. The investigated area shows medium-high indoor radon concentrations, higher than the Italian average of about 70 Bq/m³, with peaks of 500 Bq/m³ or more in buildings near active faults. Fortunately, only a small fraction of the measurements, about 1.5% of total, was found greater than EU and Italian action limits for indoor and workplaces.