Natural gamma radiation map (MARNA) and indoor radon levels in Spain

During the last decade, the Department of Applied and Medical Physics has been involved in the development of a radiation protection programme. In the framework of this programme, measurements of indoor radon, principally, have been carried out nationwide. Geometric mean radon concentrations of 45 Bq m(-3) in the whole country and 130 Bq m(-3) in the high natural radiation area have been estimated. On the other hand, the so-called MARNA Project is developed into the framework of an agreement subscribed between the Spanish Nuclear Safety Council (CSN) and the National Uranium (ENUSA), the first phase of which has been the elaboration of the Natural Gamma Radiation Map of Spain on the scale of 1:1,000,000 using radiometric data generated in the 30 years of the lifetime of the ancient National Uranium Exploration and Investigation Plan mainly through airborne, carborne, and by foot surveys, within the MARNA Project itself. The lowest averaged dose rate from external gamma radiation (19.3 nGyh(-1)) was found in carbonate bedrock and the highest (87.7 nGyh(-1)) was found in granite and clay bedrock. This paper summarizes the main results obtained from the measurements performed in both projects, with special interest in those concerning the correlation between the data reported in order to conclude about the potential benefit of the MARNA maps in the definition of affected areas in the country.     

哈尔滨市部分新装修住宅室内空气质量的检测与评价

大量含有有害物质的装修材料的应用是引起室内空气污染的主要原因之一,经过对哈尔滨市内部分新装修住宅室内空气污染状况调查后发现,游离甲醛和总挥发性有机物均存在不同比例的超标现象。本文采用客观指数评价方法对新装修住宅的室内空气质量进行了评价,评价结果显示,48％的住宅室内空气质量符合卫生标准。     

Seasonal variation of indoor radon in dwellings of Malwa region, Punjab

Indoor radon measurements in 105 dwellings belonging to 21 villages of Muktsar and Ferozepur districts of Malwa region, Punjab, have been carried out, using LR-115 type II cellulose nitrate films in the bare mode. The annual average indoor radon value in the study area varies from 76.25 to 145.50 Bq m⁻³, which is well within the recommended action level [ICRP, 1993. Protection against radon at home and work. Annals of ICRP, ICRP Publication, p. 65]. Seasonal variation of indoor radon shows high values in winter and low values in summer. The winter/summer ratio of radon concentration has been computed for all 105 dwellings. The winter/summer ratio of indoor radon ranges from 0.84 to 1.89 with an average of 1.46. The indoor radon values obtained in the present investigation are more than the world average of 40 Bq m⁻³     

Dose estimation and radon action level problems due to nanosize radon progeny aerosols in underground manganese ore mine

One of the essential parameters influencing of the dose conversion factor is the ratio of unattached short-lived radon progeny. This may differ from the value identified for indoor conditions when considering special workplaces such as mines. Inevitably, application of the dose conversion factors used in surface workplaces considerably reduces the reliability of dose estimation in the case of mines.This paper surveyed the concentration of radon and its short-lived radon progeny and identified the unattached fraction of short-lived radon progeny. As well equilibrium factor during the month of August was calculated simultaneously at two extraction faces in a manganese ore mine.During working hours the average radon concentrations were 220 Bq m⁻³ and 530 Bq m⁻³ at Faces 1 and 2; the average short-lived progeny concentration was 90 Bq m⁻³ and 190 Bq m⁻³, the average equilibrium factors were 0.46 and 0.36, and the average unattached fractions were 0.21 and 0.17, respectively. The calculated dose conversion factor was between 9 and 27 mSv WLM⁻¹, but higher values could also be possible.     

Radon measurements by nuclear track detectors in secondary schools in Oke-Ogun region, Nigeria

Radon measurements were performed in secondary schools in the Oke-Ogun area, South-west, Nigeria, by solid state nuclear track detectors (SSNTDs). About seventy CR-39 detectors were distributed in 35 high schools of the Oke-Ogun area. The CR-39 detectors were exposed in the schools for 3 months and then etched in NaOH 6 N solution at 90 °C for 3 h. The tracks were counted manually at the microscope and the radon concentration was determined at the Radioactivity Laboratory, Department of Physics, University of Trieste, Trieste, Italy. The overall average radon concentration in the surveyed area was 45 ± 27 Bq m⁻³. The results indicate no radiological health hazard. The research also focused on parameters affecting radon concentrations such as the age of the building in relation to building materials and floor number of the classrooms. The results show that radon concentrations in ground floors are higher than in upper floors.     

Po-210 and Pb-210 as atmospheric tracers and global atmospheric Pb-210 fallout: a review

Over the past ∼5 decades, the distribution of ²²²Rn and its progenies (mainly ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po) have provided a wealth of information as tracers to quantify several atmospheric processes that include: i) source tracking and transport time scales of air masses; ii) the stability and vertical movement of air masses iii) removal rate constants and residence times of aerosols; iv) chemical behavior of analog species; and v) washout ratios and deposition velocities of aerosols. Most of these applications require that the sources and sink terms of these nuclides are well characterized.Utility of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po as atmospheric tracers requires that data on the ²²²Rn emanation rates is well documented. Due to low concentrations of ²²⁶Ra in surface waters, the ²²²Rn emanation rates from the continent is about two orders of magnitude higher than that of the ocean. This has led to distinctly higher ²¹⁰Pb concentrations in continental air masses compared to oceanic air masses. The highly varying concentrations of ²¹⁰Pb in air as well the depositional fluxes have yielded insight on the sources and transit times of aerosols. In an ideal enclosed air mass (closed system with respect to these nuclides), the residence times of aerosols obtained from the activity ratios of ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb are expected to agree with each other, but a large number of studies have indicated discordance between the residence times obtained from these three pairs. Recent results from the distribution of these nuclides in size-fractionated aerosols appear to yield consistent residence time in smaller-size aerosols, possibly suggesting that larger size aerosols are derived from resuspended dust. The residence times calculated from the ²¹⁰Pb/²²²Rn, ²¹⁰Bi/²¹⁰Pb, and ²¹⁰Po/²¹⁰Pb activity ratios published from 1970’s are compared to those data obtained in size-fractionated aerosols in this decade and possible reasons for the discordance is discussed with some key recommendations for future studies.The existing global atmospheric inventory data of ²¹⁰Pb is re-evaluated and a ‘global curve’ for the depositional fluxes of ²¹⁰Pb is established. A current global budget for atmospheric ²¹⁰Po and ²¹⁰Pb is also established. The relative importance of dry fallout of ²¹⁰Po and ²¹⁰Pb at different latitudes is evaluated. The global values for the deposition velocities of aerosols using ²¹⁰Po and ²¹⁰Pb are synthesized.     

Soil gas (²²²Rn, CO₂, ⁴He) behaviour over a natural CO₂ accumulation, Montmiral area (Drôme, France): geographical, geological and temporal relationships

The south east basin of France shelters deep CO₂ reservoirs often studied with the aim of better constraining geological CO₂ storage operations. Here we present new soil gas data, completing an existing dataset (CO₂, ²²²Rn, ⁴He), together with mineralogical and physical characterisations of soil columns, in an attempt to better understand the spatial distribution of gas concentrations in the soils and to rule on the sealed character of the CO₂ reservoir at present time.Anomalous gas concentrations were found but did not appear to be clearly related to geological structures that may drain deep gases up to the surface, implying a dominant influence of near surface processes as indicated by carbon isotope ratios. Coarse grained, quartz-rich soils favoured the existence of high CO₂ concentrations. Fine grained clayey soils preferentially favoured the existence of ²²²Rn but not CO₂. Soil formations did not act as barriers preventing gas migrations in soils, either due to water content or due to mineralogical composition. No abundant leakage from the Montmiral reservoir can be highlighted by the measurements, even near the exploitation well. As good correlation between CO₂ and ²²²Rn concentrations still exist, it is suggested that ²²²Rn migration is also CO₂ dependent in non-leaking areas - diffusion dominated systems.     

Exerpts from the history of alpha recoils

Any confined air volume holding radon (²²²Rn) gas bears a memory of past radon concentrations due to ²¹⁰Pb (T_1/2 = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author’s unsuccessful trials of removing ²¹⁴Po from radon exposed glass objects. In this contribution the history and different techniques of assessing radon exposure to man in retrospect will be overviewed. The main focus will be on the implantation of alpha recoils into glass surfaces, but also potential traps in radon dwellings will be discussed. It is concluded that for a successful retrospective application, three crucial imperatives must be met, i.e. firstly, the object must persistently store a certain fraction of the created ²¹⁰Pb atoms, secondly, be resistant over decades towards disturbances from the outside and thirdly, all ²¹⁰Pb atoms analysed must originate from airborne radon only.For large-scale radon epidemiological studies, non-destructive and inexpensive measurement techniques are essential. Large-scale studies cannot be based on objects rarely found in dwellings or not available for measurements     

Temperature calibration formula for activated charcoal radon collectors

Radon adsorption by activated charcoal collectors such as PicoRad radon detectors is known to be largely affected by temperature and relative humidity. Quantitative models are, however, still needed for accurate radon estimation in a variable environment. Here we introduce a temperature calibration formula based on the gas adsorption theory to evaluate the radon concentration in air from the average temperature, collection time, and liquid scintillation count rate. On the basis of calibration experiments done by using the 25 m³ radon chamber available at the National Institute of Radiological Sciences in Japan, we found that the radon adsorption efficiency may vary up to a factor of two for temperatures typical of indoor conditions. We expect our results to be useful for establishing standardized protocols for optimized radon assessment in dwellings and workplaces.     

Relationship between deposition and attachment rates in Jacobi room model

It is shown in this work that parameters of the Jacobi model, which describes behavior of short-lived radon progeny, are not independent. The relationship between deposition rate of attached radon progeny and attachment rate of their unattached fraction was determined in this paper. It was found that deposition rate increases when the attachment rate is smaller; this effect is more pronounced for larger friction velocity. The deposition rate of attached radon progeny is presented here as a function of friction velocity, ventilation and attachment rate. Deposition rate of attached fraction was estimated in the range 0.012-0.46 h⁻¹, when attachment rate varies from 10 h⁻¹ to 100 h⁻¹.