Determination of the radon diffusion coefficient and radon exhalation rate in Moroccan quaternary samples using the SSNTD technique

Measurements have been made of radon (²²²Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq^.m^-2.h^-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09)^.10^-6 m^2.s^-1 to (4.3±0.36)^.10^-6 m^2.s^-1. Furthermore, the correlation between ²²²Rn diffusion coefficient and porosity are also discussed.     

Thermal behaviour of perovskite ceramics as a matrix for encapsulation of hazardous elements

Summary Emanation thermal analysis (ETA) was used to characterize thermal behaviour of the perovskite ceramics designed as a matrix for the encapsulation of high level radioactive waste. The perovskite ceramics (composition CaTiO₃ where small admixtures of Nd and Ce simulated the radioactive elements Cm and Pu, respectively) was prepared from sol-gel precursors by hot pressing at 1250°C/29 MPa for 2 h. The chemical durability of the ceramics was tested by leaching in the solution with pH 2 at 90°C/2 months. ETA results of as-leached and as-prepared perovskite ceramics samples were compared and evaluated by means of a mathematical model. Three temperature ranges of the annealing of structure defects in the as-prepared sample were determined from the decrease of radon release rate in the ranges 280-560, 800-960 and 960-1200°C, respectively. One annealing step was determined for the as-leached sample from the decrease of radon release rate in the range of 800-950°C.     

The influence of the lithology and depth on water recharge of wells in two Moroccan Atlantic coastal regions by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon and thoron -activity concentrations were evaluated inside different underground water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted -particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranium nitrate standard solutions. A relationship between water radon concentration and recharge of wells dug in two Moroccan Atlantic coastal regions, for a given lithology, was found. The influence of the lithology and depth on radon concentration and salinity of well waters studied was investigated.     

Measurements of222Rn migration in soil

The concentration of radon (²²²Rn) was measured in the soil near the ground surface, using CR/39 solid state nuclear track detectors. The measurements were carried out in PVC tubes at 0.25 m intervals up to 1.25 m. The detectors were etched in 7N NaOH solutions at 80°C. The -tracks from radon's decay were counted using a microscope. A microscope-camera-computer system developed for automatic counting was also used. The results provide evidence for the non-diffusive transport of radon in soils. A transport length of (46.9±3.2) cm was estimated for radon transport near ground surface. Also the variation of soil's radon concentration was correlate to humidity and atmospheric pressure.     

Solid-state photoreaction on an inclusion compound of coumarin with β-cyclodextrin

-Cyclodextrin was found to form a crystalline inclusion complex with coumarin. The solid-state photoreaction of the inclusion compound was studied at 25–27°C, and compared with those of coumarin and of a mixture of coumarin with the cyclodextrin. Under irradiation at a wavelength longer than 300 nm, coumarin with or without -cyclodextrin and in the inclusion complex converted to a photodimer, cis-head-to-head dimer in the solid state. The conversion rate of coumarin was higher than that in the mixture, and the latter was higher than that in the complex. These indicate that -cyclodextrin retards the photodimerization of coumarin, but does not affect the course of the reaction in the solid state.     

Monitoring of Radon Anomalies in the Rio Casanay and a Thermal Spring Near the El Pilar Fault Shortly After the July 9, 1997 Earthquake (Mw=6.9) in the State of Sucre (Venezuela)

Immediately, after the July 9, 1997 earthquake (Ms = 6.8) in the state of Sucre, Venezuela, we began measuring radon in water to investigate the possible correlations with the seismic activity and to study the meteorological affects. Sampling periods were for 3–5 days with 4–8 weeks in between each. During the first two sampling periods, the seismic activity was high with several minor events (Mb4.0) and anomalous radon concentrations were measured and considered as possible precursors for the events. We have also shown that the radon activity was stable except for daily meteorological effects during periods of low seismic activity. The radon activity during the first year after the major event on July 9, 1997, at the beginning of the rainy season increased from about 50 pCi/l to about 350 pCi/l for all sampling points. Then abruptly dropped to 100 pci/l at the beginning of the next rainy season for points #1 and #2 in the Casanay river and stayed relativelystable during the second year. At the start of the third year, the values began to increase again, similarly to the first year. We concluded that this was caused by the heavy rainfall at the beginning of the rainy season. While at the sampling points at Hotel Cristal, thermal spring pool, it decreased slowly during the second year but increased again at the onset of the third year. Finally, we have concluded as other investigators, that monitoring radon activity alone is insufficient to predict minor earthquakes (Mb4.0), but in some cases it can be considered as a precursor.     

Influence of pollution and building materials on domestic radioactivity in Marrakechi dwellings

Domestic radioactivity has been studied by using LR-115 and CR-39 solid state nuclear track detectors (SNTD) and a suitable beta- and gamma-gaseous counter. A new calibration method, based on measuring thoron (²²⁰Rn) to radon (²²²Rn) ratios, has been developed for determining the -activity originating from radon in different Marrakechi dwellings. The influence of building materials as well as pollution and airing factors, on domestic radioactivity has been investigated.     

A simple passive collector for direct measurement of radon flux from soil

A simple technique for measurement of the soil-atmosphere radon flux has been developed by fastening a charcoal canister inside a PVC cylindrical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister and measurement of the radon daughter activity on a NaI detector, the radon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of charcoal canisters to²²⁶Ra-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the²²²Rn generated during radium decay, it forms a useful flux standard. The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or accumulator method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were based on single overnight deployments. The experiment was repeated 5 times at two different sites and the two techniques generally agreed within a 95% confidence interval.     

Determination of Radon Equivalent Alpha-Doses in Different Human Organs from Water Ingestion Using SSNTD and Dosimetric Compartmental Models

Radon -activities per unit volume have been measured in different drinking water samples belonging to different aquifers and sources by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). Radon initial equivalent -dose rates due to water ingestion have been evaluated in the stomach assuming that all the radon ingested appears in this organ. The influence of the origin and quality of the water samples studied has been investigated. Committed equivalent doses have been determined in different human organs by using dosimetric compartment models. The influence of the radon mean residence time on the committed equivalent doses in the different compartments of the gastrointestinal system has been studied. The committed equivalent dose per unit activity of radon ingested has been evaluated in the stomach tissue and compared with literature data.     

Multimedia Analysis of Radon in 10 mL of Air for in-Laboratory Quality Assurance

A new, simple, reliable and self-consistent procedure has been developed to produce, handle and measure radon in 10mL of air in the three media air, water and charcoal simultaneously. Equal and low activities of radon (200Bq, 4ag) are transferred with a 10mL gas syringe from a 3.8L natural, harmless and constant radon source to three receivers: a 48L Peli case with outdoor air, an 0.5L bottle with tap water, and a 22mL tube with activated charcoal. Concentrations, i.e. activities in the three media are measured with different methods providing independent results. Hence, in-laboratory cross-method calibration and traceability to a certified standard is available for radon in air and in water for the first time and with minimum effort.     

Radon and CN: Complementary tracers of polluted air masses at coastal and island sites

CN and radon concentrations have been measured at coastal and island sites in programs measuring baseline concentrations of atmospheric trace constituents. It is shown that addition of CN and radon concentrations to meteorological criteria for characterisation of an air mass, substantially improves the objectivity of baseline selection. Wind direction and CN concentration are both useful for indicating likelihood of pollution from sources within a few km. Beyond that the fetch over land is enough for radon to be useful. For sources more than a thousand km away, wind direction and CN become poor indicators, whereas radon concentrations still yield reliable indications of land contact.     

Effect of random copolymerization on growth transition and morphology change in polypropylene

The growth rate of an ethylene-propylene random copolymer with a 2.8% w/w ethylene content was studied in a similar manner to polypropylene. A growth regime transition associated with a birefringence change was observed at 130C, while the same phenomena appeared at 138C in isotactic polypropylene. In both polymers positive birefringence corresponds to Regime III, whereas negative birefringence of spherulites is associated with Regime II. The birefringence change is attributed to a change in the organization of crystalline lamellae: quadritic arrays of intercrossing lamellae at low temperature (Regime III) and preferentially radiating lamellae at higher temperature (Regime II). We confirm that such a morphological change can be interpreted using the concept of non-adjacent re-entry introduced in Hoffman's kinetic theory. Thus, quadritic morphology seems to have a partly kinetic origin. The shift of the transition temperature in the copolymer is due to the rejection of ethylene segments at the surface of crystalline lamellae of polypropylene.     

Background airborne radioactivity in an equatorial Brazilian town

The aim of this work was to determine the background airbome radioactivity in the town of Natal, Brazil. Indoor radon concentrations were measured inside 24 buildings using solid state nuclear track detectors which were exposed for a period of about 180 days. The average indoor radon level resulted to be 15.4±10.6 Bq·m^–3. Measurements of gross - and -activities were performed at six different sites for airbome particulate samples collected over cellulose nitrate filters. Mean values of 0.15±0.06 mBq·m^–3 and 0.42±0.10 mBq·m^–3 were obtained for the gross -and gross -activity, respectively.     

Effect of the aggregate state on the conjugation in the 2-(2′-quinolyl)benzoxazole system

It was demonstrated by x-ray diffraction analysis, electronic spectroscopy, and mass spectrometry that the phase state and a decrease in the temperature of the solution have a substantial effect on the dihedral angle between the planes of the rings and the conjugation in the 2-(2-quinolyl)benzoxazole molecule. The molecule is planar in the crystalline state, in the gas phase, and in solution at low temperature. The conjugation is maximal in these cases. The conjugation decreases when the compound is dissolved, and this is reflected in the character of the electronic absorption and emission spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 775–779, June, 1982.     

Radon concentration in basements of old town buildings in the Lublin region, Poland

Radon concentration in basements of old buildings in the oldest towns of Lublin region (Zamo, Chelm and Sandomierz) was determined. Two techniques were applied: passive (Pico-rad) and alpha-spectrometry for radon progeny concentration measurement (SILENA). It was found that only 7% of results exceeded a dose limit of 400 Bq·m^-3, established for old buildings. Radon concentration levels ranged from 0.2 to 5150 Bq·m^-3. Distribution of the results satisfied a log-normal relationship. Applying these two methods at the same time, the radioactive equilibrium factor of radon and its progeny was determined. In the underground ways, open for visitors, no higher radon concentration was observed.     

Thermal analysis of Vectran® fibers and films

Vectra^® liquid crystalline polymers (LCP's) were introduced as commercial products in the mid-1980's. The first of these (Vectra A130) was a wholly aromatic thermotropic copolyester ofp-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Vectra A130 is a thermotropic LCP that can be melt spun into filaments that on heat treatment are characterized by high strength and high modulus. Vectra resin can also be extruded into films. In the fiber or film form this material is commercially known as Vectran^®. Heat treatment enhances the tensile strength of Vectran fiber variants. Because of this, the elucidation of the physical transformations taking place in the internal structure of the material during heating has always been an important subject. Several thermal techniques are used to indicate clearly that what is observed as a glass transition is unlike the conventional glass transition in typical semicrystalline polymers. There is also an indication of the presence of multiple states of mesophase aggregation that collapse into a single state when taken to high enough temperatures.     

Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose

Stable colloidal suspensions of cellulose microcrystallites may be prepared from filter paper by sulfuric acid hydrolysis. Above a critical concentration, the suspensions form a chiral nematic ordered phase, or colloid crystal. The preparation conditions govern the properties of the individual cellulose microcrystallites, and hence the liquid crystalline phase separation of the cellulose suspensions. The particle properties and the phase separation of the suspensions were strongly dependent on the hydrolysis temperature and time, and on the intensity of the ultrasonic irradiation used to disperse the particles. The particle size of the microcrystallites was characterized with transmission electron microscopy and photon correlation spectroscopy. The surface charge was determined by conductometric titration. It was possible to fractionate the microcrystallites by size using the partitioning between isotropic and liquid crystalline phases; the longer microcrystallites migrate to the liquid crystalline phase     

Phase Behavior of Polymer Blends

The present report deals with some results on phase behavior, miscibility and phase separation for several polymer blends casting from solutions. These blends are grouped as the amorphous polymer blends, blends containing a crystalline polymer or two crystalline polymers. The blends of PMMA/PVAc were miscible and underwent phase separation at elevated temperature, exhibited LCST behavior. The benzoylated PPO has both UCST and LCST nature. For the systems composed of crystalline polymer poly(ethylene oxide) and amorphous polyurethane, of two crystalline polymers poly(-caprolactone) and poly[3,3,-bis-(chloromethyl) oxetane], appear a single T_g, indicating these blends are miscible. The interaction parameter B's were determined to be –14 J cm^–3, –15 J cm^–3 respectively. Phase separation of phenolphthalein poly(ether ether sulfone)/PEO blends were discussed in terms of thermal properties, such as their melting and crystallization behavior.This revised version was published online in November 2005 with corrections to the Cover Date.     

Radon concentrations in kindergartens of Osijek and Ljubljana

Indoor radon concentrations in the kidergartens of Osijek, Croatia, have been measured with -scintillation cells, LR-115 nuclear track detectors, as well as a Radhome semiconductor detector. Average values of 50.2, 43.7 and 47 Bq m^–3 were obtained, respectively. Under the worst conditions, the annual radon effective dose equivalent was 10 mSv y^–1. Using bare and filtered LR-115 detectors, the average equilibrium factor was assessed as 0.36 indoors. Measurements of the -dose rate in the kindergartens did not show any significant correlation with the radon concentration. Indoor radon concentrations in the kindergartens of Ljubljana, Slovenia, measured by scintillation cells had an arithmetic mean and standard deviation of 228 and 143 Bq m^–3, respectively.     

Synthesis and characterization of side-chain liquid crystalline polymer containing dichroic dye monomer

A series of side-chain liquid crystalline polysiloxanes containing 1-(p-toluidino)-4-anthraquinone undecylenate (TAU) (dye-monomer) and 4-allyloxybenzoyl-4^′-(p-propyl-benzoyl)-p-benzenediol bisate (ABB) (liquid crystalline monomer) side groups were synthesized by copolymeraztion. The molecular structures of the monomers and polymers were confirmed by FT-IR spectroscopy. The optical characterization of the monomer ABB and polymers was made by using polarizing optical microscopy (POM) technique, and their thermal behaviour was investigated by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC). The conjugate action of the dye (1-(p-toluidino)-4-hydroxyl anthraquinone) and the monomer was analyzed by fluorophotometry. Polymers and monomer ABB revealed nematic phase. And DSC results demonstrated that the glass transition temperatures (T_g) of the polymers increased with the increase in dye-monomer. TGA result showed that the temperatures at which 5% mass loss occurred () for all the polymers were above 270 °C.