A comparative study of indoor radon concentrations between dwellings and schools

The aim of this study is to determine the relationship of radon concentrations between dwellings and the schools located in the same regions and to obtain related indoor average radon concentration dwelling-school correction factor for similar locations. The research has been carried out by determining indoor radon concentrations at schools and dwellings located at the same districts in the selected two separate research fields called The Former Adapazari region and The New Adapazari region in the city of Adapazari using a total of 81 Cr-39 passive radon detectors for 75 days. The average radon concentrations have been determined for the dwellings and the schools in 15 districts of the Former Adapazari region as 59.9 Bq m⁻³ and 57.1 Bq m⁻³, respectively. The results in 4 districts of the New Adapazari region were 63.5 Bq m⁻³ for the dwellings and 61.0 Bq m⁻³ for the schools. Moreover, the annual effective doses were calculated as 1.33 mSv/y and 1.41 mSv/y for the dwellings of Former Adapazari and New Adapazari, respectively. It was seen that the doses received in the dwellings are about four times the doses received in the schools. The indoor radon concentration dwelling-school correction factor was found to be 1.04±0.01 for the research area.     

Experimental study on the Karst area fracture zones of the synthesizing geophysical methods

岩溶地区地形、地质情况相对复杂,各种物探方法的应用都受到一定条件限制,进行岩溶断裂破碎带勘察时,应进行综合物探勘察,为设计和施工提供可靠的原始资料;本文采用综合物探方法对广州地铁九号线工程田美断裂进行探测,详细查明田美断裂的走向、破碎带宽度、构造破碎特征、断裂的性质、规模和产状等;同时辅以少量勘察验证孔施工对断裂做验证,以便有效地揭示断裂特征,通过实验取得较理想的成果,并意外地发现了田美断裂的次一级断裂。     

Radioactivity in samples of cleaning materials

ABSTRACT

The cleaning products have widespread use in daily life; they are made from various complex chemical materials and their containment of radioactive material is possible; so to keep background radiation, found in our environment at as low a level as possible, the radioactivity of these products has been investigated in this research. The cleaning material products (soap, powder detergent, cloth washer and chlorine detergent) traded in the Iraqi market from both local and imported production undergo an examination to record gamma activity which can be emitted due to the existence of ²³⁸U, ²³²Th, ⁴⁰K and ²²²Rn. Gamma spectrometry techniques and radon concentration measurement equipments have been used to evaluate the level of radiation activity of these products. All results of the samples that have been studied have shown the levels of natural radioactivity is lower than the global average levels recommended by UNSCEAR, which are 30, 32 and 400 Bq/kg for ²³⁸ U, ²³²Th and ⁴⁰K, respectively; also the values of Raeq and Hex were lower than the global average recommended by OECD and ICRP, respectively. Finally, it could be concluded that no significant hazard can be raised.     

Bridging, non-bridging and free (O) oxygen in Na2O-SiO2 glasses: An X-ray Photoelectron Spectroscopic (XPS) and Nuclear Magnetic Resonance (NMR) study

High resolution Na 1s, O 1s and Si 2p core level XPS spectra of six Na₂O-SiO₂ glasses ranging in composition from 100 to 45 mol % SiO₂ have been collected using the Kratos Ultra Axis instrument with its unique charge compensation system. The O 1s spectra for the glasses are well resolved so that bridging oxygen (BO, Si-O-Si) and non-bridging oxygen (NBO, Na-O-Si) signals can be accurately fitted and quantified without resorting to constraints or assumptions. The same samples were analysed by ²⁹Si MAS NMR to obtain Q-species abundances from which BO and NBO proportions were calculated. Similar BO:NBO ratios were obtained by both methods over the entire compositional range studied. They are also consistent with most previous XPS and NMR results for glasses containing more than ~ 65 mol % SiO₂. Our XPS and NMR experimental results, however, differ somewhat from previously published XPS and NMR results for glasses containing less than about 65 mol % SiO₂.Na is mobile in the X-ray beam and mobility causes BO:NBO ratios to increase with time of exposure. Na mobility here has been circumvented to yield reliable BO:NBO ratios of the glasses. The ratios are lower than previously reported in XPS studies and are similar to ratios obtained from our ²⁹Si MAS NMR results on the same glasses. The XPS and ²⁹Si MAS NMR results also indicate the presence of a third oxygen species in sodic glasses. As has been proposed for CaSiO₃ glass and for sodic and potassic glasses containing La, we suggest that O²⁻ is present in sodic glasses at small concentrations. The O²⁻ content correlates with increased soda content and may be associated with, and instrumental in development of, three dimensional percolation channels in the glasses. The XPS O 1s line width of the BO peak is broader than the NBO peak, indicating more than one contribution to the BO peak. As observed in crystalline Na metasilicate and Na disilicate, BO of Na-silicate glasses may be of two types, one arising from BO bridging two Si atoms, and the second BO signal arising from BO bonded not only to two Si atoms but also to Na.     

Factors affecting the registration and counting of alpha tracks in solid state nuclear track detectors

In view of the fact that the radon progeny contribute the highest to the natural radiation dose to general populations, large scale and long-term measurements of radon and its progeny in the houses have been receiving considerable attention. Solid State Nuclear Track Detector (SSNTD) based systems, being the best suited for large scale passive monitoring, have been widely used for the radon gas (using a cup closed with a semi-permeable membrane) and to a limited extent, for the measurement of radon progeny (using bare mode in conjunction with the cup). These have been employed for radon mapping and indoor radon epidemiological studies with good results. In this technique, alpha tracks recorded on SSNTD films are converted to radon/thoron concentrations using corresponding conversion factors obtained from calibration experiments carried out in controlled environments. The detector response to alpha particles depends mainly on the registration efficiency of the alpha tracks on the detector films and the subsequent counting efficiency. While the former depends on the exposure design, the latter depends on the protocols followed for developing and counting of the tracks. The paper discusses on parameters like etchant temperature, stirring of the etchant and duration of etching and their influence on the etching rates on LR-115 films. Concept of break down thickness of the SSNTD film in spark counting technique is discussed with experimental results. Error estimates on measurement results as a function of background tracks of the films are also discussed in the paper.      

Dosimetric model of human lung and associated computer program

The dosimetric human respiratory tract model given in ICRP Publication 66 and ICRP Vol. 32 is briefly described in this paper. The associated home-written computer programs for calculations of radiation dose from radon and its short-lived progeny are presented, together with some representative results.      

Daily variation of radon gas and its short-lived progeny concentration near ground level and estimation of aerosol residence time

Atmospheric concentrations of radon(~(222)Rn) gas and its short-lived progenies~(218)Po,~(214)Pb, and~(214)Po were continuously monitored every four hours at the ground level in Jeddah city, Kingdom of Saudi Arabia. The measurements were performed three times every week, starting from November 2014 to October 2015. A method of electrostatic precipitation of positively charged~(218)Po and ~(214)Po by a positive voltage was applied for determining~(222)Rn gas concentration. The short-lived~(222)Rn progeny concentration was determined by using a filter holder connected with the alpha-spectrometric technique. The meteorological parameters(relative air humidity, air temperature, and wind speed) were determined during the measurements of~(222)Rn and its progeny concentrations.~(222)Rn gas as well as its short-lived progeny concentration display a daily and seasonal variation with high values in the night and early morning hours as compared to low values at noon and in the afternoon. The observed monthly atmospheric concentrations showed a seasonal trend with the highest values in the autumn/winter season and the lowest values in the spring/summer season. Moreover, and in parallel with alphaspectrometric measurements, a single filter-holder was used to collect air samples. The deposited activities of~(214)Pb and the long-lived~(222)Rn daughter ~(210)Pb on the filter were measured with the gamma spectrometric technique. The measured activity concentrations of~(214)Pb by both techniques were found to be relatively equal largely. The highest mean seasonally activity concentrations of ~(210)Pb were observed in the autumn/winter season while the lowest mean were observed in the spring/summer season. The mean residence time(MRT) of aerosol particles in the atmospheric air could be estimated from the activity ratios of ~(210)Pb/~(214)Pb.     

大气颗粒物滞留时间的确定方法及初步实验验证

通过研究大气颗粒物中222Rn子体活度比与颗粒物平均寿命之间的关系,建立了基于活度比估算大气颗粒物滞留时间(residence time of atmospheric aerosol,RTAA)的方法,并在相对理想条件下进行了实验验证.当氡室浓度稳定为1.816kBq/m3时,由214Bi/214Pb活度比计算出的RTAA为112.17min,与氡室的平均换气时间(104.17min)相当,表明大气颗粒物中同一衰变链上的放射性核素活度比(如214Bi/214Pb,210Bi/210Pb或210Po/210Pb)可以用于估算RTAA.     

Spontaneous fission of neutron-deficient fermium isotopes and the new nucleus 241Fm

Spontaneous fission of neutron-deficient fermium isotopes (N ≤ 144) was investigated. The nuclei were produced in fusion-evaporation reactions of ⁴⁰Ar beams with ^{204,206–208}Pb targets. Excitation functions of the two-and three-neutron evaporation channels were measured. The new isotope ²⁴¹Fm was identified, and its decay properties were determined. A previously made assignment of a 0.8 ms spontaneous-fission activity to the isotope ²⁴²Fm could not be confirmed. Isomeric states were not observed in any of the investigated isotopes. The experiments were performed at the velocity filter SHIP of GSI in Darmstadt.     

K-forbidden allowed $ \beta$ transitions in heavy nuclei

The role of the band quantum number K in influencing the character of allowed transitions in heavy deformed nuclei is examined. The conditions for the occurrence of K -forbidden decays in this region are explored. Specific cases of “allowed” decays proceeding via K = 2 to K = 6 channels are presented to illustrate the phenomenon. The listed K = 2 transitions, which by themselves contribute over 10% of all the presently known allowed transitions for A 228 nuclei, are seen to have an average , which is clearly outside the normal range for allowed transitions. It is concluded that, wherever the -connected states can be confidently labelled using the quantum numbers, the K -forbiddenness is in general as significant as that involving the other two (spin and parity) quantum numbers.