Seasonal variation of radon-222 concentrations in specific locations in Jordan

Previously calibrated passive detectors (CR-39) and an active radon device (Radon Monitor RM3) were used to study seasonal variation of radon-222 concentration levels inside and outside specific locations in Jordan. The study sites were located in an area that used to be an old phosphate mine. We found that the maximum value of radon concentration in air inside the dwellings, as measured by the passive dosimeters, was 1532.9 Bq/m³ during the winter season, and the minimum one was 46.3 Bq/m³ during fall season. While the highest and lowest readings of the active monitor were 892 and 4 Bq/m³ during fall and summer seasons, respectively. The radon concentration in soil ranges from 0.2 kBq/m³ in spring to 37.8 kBq/m³ in fall.     

Simultaneous measurement of radon, radon progeny and thoron concentrations using Makrofol-DE detectors

In this study we describe the set-up of a new passive integrating system to measure simultaneously ²²²Rn, ²²²Rn progeny (²¹⁸Po and ²¹⁴Po) and ²²⁰Rn concentration indoors. It consists of four Makrofol-DE (polycarbonate) circular foils. Two are enclosed within two diffusion chambers—each one with a different filter membrane—to measure ²²²Rn and ²²²Rn+²²⁰Rn. The other two foils are kept in direct contact with air and are electrochemically etched at different conditions to obtain the ²²²Rn daughters. Theoretical sensitivities of each Makrofol-DE foil are calculated using Monte-Carlo technique. The calculations are performed taking into account: (1) the Bethe–Bloch's expression for the stopping power of heavy charged particles in a medium, (2) the properties and behaviour of ²²²Rn, ²²⁰Rn and their progeny in the open air and within the diffusion chamber and (3) the etching conditions used to visualise -particles tracks.     

Rn concentrations and the radiation exposure levels in the Nerja Cave

²²²Rn concentrations in the air in one sampling point located in Nerja Cave (Spain) () have been measured over one year, since July 2003–June 2004. ²²²Rn levels were continuously monitored using Alpha-Guard (Genitron instruments) equipment, model PQ2000PRO. Firstly, the aim of this study was to perceive the daily, monthly and seasonal variations patterns of ²²²Rn concentrations. Diurnal cycles are presented by season showing that the ²²²Rn concentrations in spring–summer are higher than autumn–winter. The hourly variations are discussed in relation to various meteorological factors measured in the Cave and also on the outdoor. We have evaluated the radiation exposure levels for workers and tourists; those represent only a low percentage of the exposure guides for the general population ICRP, 1994. Protection against Radon-222 at home and at work. Pergamon Press, Oxford (publication 65).     

Environmental gamma and radon dosimetry in Venezuela

Environmental gamma exposure and radon concentration levels measured in Venezuelan regions are presented. A new generation image analyser was used for particle track counting in CR-39 detectors. Mineral water wells from where water is supplied for massive consumption have an alpha activity around 0.450 Bq L⁻¹ and few of them have concentrations above 50 Bq L⁻¹. Coastal potable water activity is on the average around 5.3 ± 12% Bq L⁻¹. Indoor radon national average is 36 ± 5% Bq m⁻³; in two of the 36 monitored sites, the measured average is above 400 ± 5% Bq m⁻³. In air gamma dose values are between 100 and 144 nGy h⁻¹. In soil, ¹³⁷Cs concentration is around 0.5 and 10 Bq kg⁻¹ at the depth of down to 20 cm. Building materials were included in this study. ⁷Be and ¹³⁷Cs were measured in low concentration in tropical plants on Tepuy-s (sacred mountains in the Amazonas State). Geological active faults were identified by radon concentration measurements using LR-115.     

Soil radon levels measured with SSNTD's and the soil radium content

The source of the radon gas ²²²Rn in the ground air is the soil and the bedrock underneath. The potential radon level in the ground is given by the content of ²²⁶Ra in the ground. The presence of ²²⁶Ra is in turn dependent on the amount of ²³⁸U in the ground, and these two isotopes are not always found to be in equilibrium in a sample of soil or bedrock. Especially if the soil is washed out, the radium content may be reduced. When the soil is the relevant source of the radon gas, it is interesting to look for a possible relation between the radon level and the radium content of the soil.

In this paper we report on measurements of soil radon level carried out with SSNTDs at several European sites. Soil samples were collected at these sites and analysed with gamma spectrometry to determine their radium content. A comparison of the different degree of disequilibrium of radon, defined as the ratio between the actual and the secular equilibrium-with-radium soil radon concentration, found at the different sites and depths is presented. The influence on the result of soil type and climate is briefly discussed.     

Ra in geothermal and bottled mineral waters of Hungary

Geothermal waters have been used on a large scale for bathing, drinking and medical purposes, while the consumption of bottled mineral waters is increasing. In this work, radon and radium activity concentrations of thermal and bottled mineral waters, originating from different regions of Hungary, were studied by different radioanalytical methods. It was found that the thermal springs, which supply the world famous baths of Budapest along the right riverside of the Danube, have high ²²²Rn and ²²⁶Ra activity concentration: up to about 100 and 1 kBqm⁻³, respectively. The radium content of some investigated geothermal waters found in the NE region of the Great Hungarian Plain is even higher: up to several kBqm⁻³. The ²²⁶Ra content of bottled mineral waters, commercially available in Hungary, was determined by gamma-spectrometric method, applying radiochemical separation. The highest value exceeded 2 kBqm⁻³ in the case of the Apenta mineral water, which is a popular brand in Hungary, as well as in Europe and North America.     

Radon decay products attached to clothes in a nuclear laboratory

A whole body counter determined the presence of radioactivities up to 21.8 kBq for ²¹⁴Bi and up to 18.7 kBq for ²¹⁴Pb attached to clothes of workers in a Nuclear Research Laboratory. A radon survey reveals that 80% of the monitoring areas have radon concentration values lower than 500 Bq m⁻³, while 10% of the sampling points with values bigger than 1 kBq m⁻³ correspond to the workers mentioned above. By exposing samples of 0.04 m² clothes in a radon chamber, it was observed that radon decay products ²¹⁴Bi and ²¹⁴Pb were attached to them with an activity of 315–618 Bq per each kBq m⁻³ of Rn concentration additionally, fibres characterised with a lower electrostatics build up showed the lower attachment.     

ITER气体注入系统含氚管道的等效漏率评估

氚的泄漏会对公众安全和环境造成危害,有必要对含氚管道的泄漏进行分析。对ITER气体注入系统的含氚管道进行分析,对触发系统氚报警阈值(3×10⁵Bq·m^-3/环境安全值,1×10⁸Bq·m^-3/系统安全值)时,氚送气管、离子源管以及中性化管泄漏的等效空气漏率进行了计算。结果表明,氚送气管泄漏的风险最高。虽然氚送气管的气体压力低于包容管的夹层压力,但由于管道的氚浓度高,漏率大于3.2×10^-8 Pa·m³·s^-1时会触发报警。而在离子源管中虽然氚浓度低,但管道的气体压力远高于包容管的夹层压力,漏率大于6.1×10^-6 Pa·m³·s^-1时会触发氚报警。气体注入系统含氚管道泄漏的氚危害不可忽视,必须进行实时监测和防护。     

HL-2M装置真空室预装阶段检漏试验

通过在加工现场和安装现场搭建的真空辅助系统、四极质谱计及氦检漏仪组成的检漏系统,运用残余气体分析和氦质谱检漏方法在冷态下对HL-2M真空室扇形段及真空室整体进行了真空检漏试验.对漏点进行修复后,测试了真空室的极限真空度和总漏气率等.真空室经过72h的抽气后,真空度达到3.7×10?5Pa,超过了1.0×10?4Pa的预...     

Verification of radioactive equilibrium to discriminate radon and progeny with LR 115 under a thin film geometry

A system of image analysis is applied to the track analysis of a plastic detector (LR 115). Based on track characteristics the system permits the separation of tracks produced by ²²²Rn and ²¹⁸Po from those produced by ²¹⁴Po. LR 115 was used inside a thin film geometry monitor and irradiated under very low ventilation conditions, where secular radioactive equilibrium between radon and progeny is expected. The monitor is used intending to exclude the entrance of external radon progeny in the sensitive volume of the plastic detector. The radioactive (secular) equilibrium is rapidly attained inside the monitor and equal numbers of particles from ²¹⁸Po, ²¹⁴Po and ²²²Rn are expected to reach the plastic. In order to guarantee good detection efficiency in the restricted volume, and to discriminate alpha energies, the LR 115 piece inside the monitor is covered with an aluminum foil of suitable thickness. The separation of tracks produced by alpha particles of different energies is made through the use of two track parameters related to area and opacity of the tracks. The ratio of tracks produced by (²¹⁸Po and ²²²Rn) and ²¹⁴Po—expected as two—is used to test the separation method in a series of controlled irradiations. Results point to the experimental attainment of radioactive equilibrium inside the monitor supporting the determination of ²¹⁴Po concentration alone, and points to an exclusive entrance of ²²²Rn inside the monitor, at low ventilation rates. This way, in situations where radioactive equilibrium inside the monitor may be considered, the exclusive measurement of radon concentration in the environment is possible.     

一种可用于极化~3He实验的新型磁场系统

原子核自旋极化的~3He气体已被深入研究并广泛用于各种科学实验.在过去的极化~3He实验中,为了减小磁场梯度对纵向弛豫时间的影响,通常会建造大尺寸的亥姆霍兹线圈来提供所需均匀度的主磁场环境.本文通过计算得到了新的六正方形线圈系统,可以为极化~3He实验提供小型高均匀性的磁场装置.其中线圈系√统内部超过30%的区域磁场梯度满足(|▽B_x|~2+|▽B_y|~2)/B_0 10~(-4)cm~(-1),这一均匀区域比例超过了现在所有用于极化~3He实验的线圈装置.对于其他需要大均匀区域磁场环境的研究实验,新的六线圈系统也具有很好的应用价值.     

Baseline studies of radon/thoron concentration levels in and around the Lambapur and Peddagattu areas in Nalgonda district, Andhra Pradesh, India

Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×10¹ and (6.7±0.3)×10¹ Bq/m³, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution.     

Natural activities of U, Th and K in some Indian building materials

The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K have been determined by gamma-ray spectrometry. The measured activity in the selected building materials ranges from (3.2 to 151.7 Bq/kg), 14 to 63.7 Bq/kg and 24.3 to 121.5 Bq/kg for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. The activity concentration of ²³⁸U has been determined using fission track technique and the value ranges from 0.11 to 3.85 ppm. The concentrations for these natural radionuclides are compared with the reported data from other countries. Radium-equivalent activities (Ra_eq) are calculated for the measured samples to assess the radiation hazards arising due to the use of these materials in the construction of dwellings. All building materials have shown Ra_eq activities lower than the limit set in the Organization for Economic Cooperation and Development (OECD) report (370 Bq/kg), equivalent to external gamma dose of 1.5 mSvyr⁻¹. A good correlation has been observed between ²³⁸U and ²²⁶Ra in these materials.     

The Radamon radon detector and an example of application

The etched track type Radamon radon detector is presented. As an example of application representative indoor radon survey was performed in Gyergyóremete (Romania) to pilot a study that can be done in other places of the country. Gyergyóremete was selected, because it was built on volcanic rock, where a number of aligning mineral water springs indicates the existence of geological faulting, and therefore, it was suspected that the village could be on a radon prone area. Measurements were done in sleeping rooms at pillow level. Representativity of the sample was ensured by random pull of 120 houses from the stock (hypergeometric statistical model). From the results it can be stated that the percentages of houses expected to have annual average ²²²Rn activity concentration higher than 400 Bqm⁻³ is less than 1%.     

System for calibration of track detectors used in gaseous and solid alpha radionuclides monitoring

A laboratory system for the calibration of track detectors and charcoal detectors used in monitoring of radon and its decay products/their aerosols in air, is proposed. The system consists of three main components: (i) the alpha exposure chambers, including alpha monitoring devices and the connection with the ²²⁶Ra radioactive source. The CR-39 track detectors are mounted in the monitoring devices pre-equipped or not with paper filter; (ii) the calibrated  ²²⁶Ra source. Among the three tested sources: ²²²Rn, ²²⁶Ra+²²²Rn and ²²⁶Ra, the ²²⁶Ra source is considered the most appropriate radon source for our calibration system. It is kept into an airtight flat bottom flask, the radionuclide ²²⁶Ra being always in the radioactive equilibrium with their descendants. In the alpha exposure chambers, the source assures the radon at a constant rate; (iii) the ALFAUURASE program for the computation of radioactive accumulation of the alpha ²²⁶Ra descendants. For any initial mass of the parent, the amount and the activity of each alpha decay product and of all the decay products can be calculated by this computation program. Each component of the calibration system is described in the paper. The use of the system for the calibration of CR-39 track detectors in radon measurements is tested.     

Natural radioactivity in marble stones- Jordan

Natural radioactivity has been measured in marble stone samples collected from Dabaa'h, Ajloun and Azrak areas using a gamma spectroscopy technique. The measured ²²⁶Ra activities in the stones collected from Dabaa'h quarries varied from 264.9 Bq kg⁻¹ to 369.5 Bq kg⁻¹. In samples from Ajloun and Azrak the maximum values of ²²⁶Ra were 28.3 Bq kg⁻¹ and 23.41 Bq kg⁻¹, respectively. The measured values of ²³²Th were less than 17.89 Bq kg⁻¹. The average values of the radium equivalent activities as well as external and internal hazard indices were also calculated. It was observed that for marble stones from Dabaa'h area, estimated average value of the external hazard index is 0.873 and that of internal hazard index is 1.71.     

Measurement of natural radioactivity in Jordanian sand

Sand samples were collected from Adasiah (near Amman), Jerash and Ghor As-Safi (near Karak). ²²⁶Ra, ²³²Th and ⁴⁰K activities, present in these samples, were measured using a gamma ray spectroscopy technique. The average values of the radium equivalent activities were calculated and were found to be 41.06 Bq kg⁻¹, 54.7 Bq kg⁻¹ and 85.53 Bq kg⁻¹ in samples collected from Adasiah, Jerash and Ghor As-Safi, respectively. These values are within the limit (i.e. less than 370 Bq kg⁻¹) recommended for the safe use of construction materials for dwellingsby OECD.     

Measurement of indoor Rn using CR-39 under a thin film geometry

In this work an assembly for indoor ²²²Rn measurement is presented. This assembly is made up of two acrylic plates (14 cm×14 cm) separated by a distance of 4 mm. To prevent radon daughters from outside entering the assembly (and produce alpha particle tracks striking the CR-39 detector placed in the central region of one of these plates), the borders of these plates were progressively closed, leaving open only a rectangular aperture of 5 mm×4 mm. The size of this opening was determined experimentally, by exposing in two indoor environments assemblies with different apertures as follows: (i) all borders open; (ii) two borders closed; (iii) three borders closed; (iv) four borders closed but one containing a 6 cm×4 mm opening; (v) four borders closed but one containing a 2.5 cm×4 mm opening and (vi) four borders closed but one containing a 0.5 cm×4 mm opening. Track density shows a noticeable decrease between assembly (i) and assembly (iii), remaining constant for smaller openings. Only ²²²Rn, a noble gas, should enter the assembly independently of the opening size.     

Site-selective spectroscopy in Eu: lanthanum magnesium aluminate

Pulsed resonance emission spectra for La_1-xEu_xMgAl₁₁O₁₉ are reported under excitation into the non-degenerate ⁵D₀ « ⁷F₀ transition of Eu³⁺ at 77 K. Emission spectra recorded under continuous-wave excitation into the same transition at liquid helium temperature were also examined. These results show clear evidence for the existence of only two distinct substitutional site distributions for Eu³⁺, with their ⁵D₀ « ⁷F₀ transitions between 577 and 579 nm. The suggestion of a third site distribution ca. 576 nm is also reported. Discrepancies concerning the number of Eu³⁺ substitutional sites and the positions of their corresponding ⁵D₀ å ⁷F₀ peaks reported in other studies are addressed in the light of our results.     

Spectroscopic investigation of a low current arc in pure fluorine

A pure fluorine 10-A DC arc has been operated in an Al₂O₃ tube of 18 mm diameter at atmospheric pressure. This arc was used to perform radially resolved spectroscopic end-on measurements in the visible and UV-spectral regions. An excitation temperature of 7800 K on the arc axis was determined from the intensity of atomic fluorine lines, and an ion density of 1.7×10 ²¹ m^-3 was determined from the half-width of the contamination line H_β. A Boltzmann plot of the affinity continuum in the UV-spectral region yields two groups of electrons. A group of hot electrons is characterized by a temperature that agrees with the excitation temperature, and a group of cold electrons has a temperature in accordance to the gas temperature of 4000 K. The absolute intensity of the affinity continuum gives and electron density of 1.3×10²⁰ m^-3 on the arc axis, which is lower than the density of both positive and negative ions in the discharge. From the difference between the electron and gas temperature, an elastic collision cross section between the electrons and F-atoms of 2×10^-20 m² is determined