Modelling the long-term consequences of a hypothetical dispersal of radioactivity in an urban area including remediation alternatives

The Urban Remediation Working Group of the International Atomic Energy Agency's EMRAS (Environmental Modelling for Radiation Safety) program was organized to address issues of remediation assessment modelling for urban areas contaminated with dispersed radionuclides. The present paper describes the second of two modelling exercises. This exercise was based on a hypothetical dispersal of radioactivity in an urban area from a radiological dispersal device, with reference surface contamination at selected sites used as the primary input information. Modelling endpoints for the exercise included radionuclide concentrations and external dose rates at specified locations, contributions to the dose rates from individual surfaces, and annual and cumulative external doses to specified reference individuals. Model predictions were performed for a “no action” situation (with no remedial measures) and for selected countermeasures. The exercise provided an opportunity for comparison of three modelling approaches, as well as a comparison of the predicted effectiveness of various countermeasures in terms of their short-term and long-term effects on predicted doses to humans.     

Determination of radionuclide levels in rainwater using ion exchange resin and γ-spectrometry

The evaluation of radioactivity accidentally released into the atmosphere involves determining the radioactivity levels of rainwater samples. Rainwater scavenges atmospheric airborne radioactivity in such a way that surface contamination can be deduced from rainfall rate and rainwater radioactivity content. For this purpose, rainwater is usually collected in large surface collectors and then measured by γ-spectrometry after such treatments as evaporation or iron hydroxide precipitation. We found that collectors can be adapted to accept large surface (diameter 47 mm) cartridges containing a strongly acidic resin (Dowex AG 88) which is able to quantitatively extract radioactivity from rainwater, even during heavy rainfall. The resin can then be measured by γ-spectrometry. The detection limit is 0.1 Bq per sample of resin (80 g) for ¹³⁷Cs. Natural ⁷Be and ²¹⁰Pb can also be measured and the activity ratio of both radionuclides is comparable with those obtained through iron hydroxide precipitation and air filter measurements. Occasionally ²²Na has also been measured above the detection limit. A comparison between the evaporation method and the resin method demonstrated that 2/3 of ⁷Be can be lost during the evaporation process. The resin method is simple and highly efficient at extracting radioactivity. Because of these great advantages, we anticipate it could replace former rainwater determination methods. Moreover, it does not necessitate the transportation of large rainwater volumes to the laboratory.     

Inventory and vertical migration of ¹³⁷Cs in Spanish mainland soils

In this study the total activity of ¹³⁷Cs deposited per unit area over the Spanish peninsular territory was analysed using a 150 × 150 km² mesh grid, with samples taken from 29 points. The deposited activities ranged between 251 and 6074 Bq/m². A linear relationship was obtained between these values and the mean annual rainfall at each sampling point which allowed a map to be drawn, using GIS software, which shows the distribution of total deposited ¹³⁷Cs activity across the Spanish mainland. At twelve of these sampling points the vertical migration profile of ¹³⁷Cs was obtained. These profiles are separated into two groups with different behaviour, one of which includes clay and loam soils and the other containing sandy soils. For both groups of profiles the parameters of the convective-diffusive model, which describes the vertical migration of ¹³⁷Cs in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) were calculated.     

Radionuclide content of building materials and associated gamma dose rates in Egyptian dwellings

Studies have been carried out to determine the natural radioactivity in some building materials (bricks, tiles, marble and ceramics) and their associated radiation hazard. The radioactivity concentrations of ²²⁶Ra ²³²Th and ⁴⁰K were measured using a gamma spectrometer with a Hp–Ge detector. The activities of ²³⁸U and ²³⁴U were measured using an alpha-spectrometer with a surface barrier detector after applying a radiochemical procedure. The ²³⁴U/²³⁸U isotopic ratios were calculated. The radium equivalent activities and the radiation hazard index associated with the natural radionuclides were calculated. A computer program was developed and applied to calculate the dose rate a person will receive from the walls of a room constructed from the studied building materials.     

2007—2015年长江流域四川段主要江河放射性水平分析

对2007—2015年长江流域四川段主要12条江河水体放射性核素活度浓度的监测结果进行了分析。结果表明,四川段主要江河放射性核素水平远低于我国规定的露天水源的限制浓度。与1995年中国环境天然放射性（四川省部分）、1988年长江水系天然放射性活度浓度参考范围相比,U、Th、²²⁶Ra、⁴⁰K、¹³⁷C_s均有上升趋势,其他核素活度浓度涨落不明显均在本底范围内。总 α、总 β放射性活度浓度测值均符合《生活饮用水卫生标准》（GB 5749—2006）的限值要求。     

The contents and forms of solid-phase species of radioactive strontium and cesium in Taiwan soils

This study was to investigate the activities and contents of ¹³⁷Cs in the profiles of selected arable and forest soils in Taiwan and various solid-phase species of ⁸⁵Sr and ¹³⁷Cs in selected arable soils in Taiwan. The gamma (γ) ray spectra of the collected soil samples and some of the soils amended with ⁸⁵Sr and ¹³⁷Cs were measured. The data indicate that the arable soils from Sanhsing series, Sanhsing Township and Chuangwei series, Chuangwei Township, Ilan County, and from Tunglochuan series, Pinglin Township, Taipei County shows significantly higher radioactivity of ¹³⁷Cs (ND − 11.0 ± 0.2 Bq kg⁻¹). Furthermore, the radioactivity of ¹³⁷Cs in the mountain soils (1.24 ± 0.07 − 42 ± 1 Bq kg⁻¹) from Yuanyang Lake Nature Preserve among Ilan, Taoyuan, and Hsinchu Counties is the highest among the investigated mountain forest soils. This may be mainly attributed to the fact that Ilan County is located in the northeastern part of Taiwan and faces the northeastern and northern seasonal winds with lots of precipitation annually from mid-autumn through mid-spring next year and is receiving greater amount of fallouts yearly. Due to longer reaction period (≥3 y) of ¹³⁷Cs with soil components, ¹³⁷Cs was mainly in the forms bound to oxides and to organic matter in the soil amended with ¹³⁷Cs and in the soil contaminated with ¹³⁷Cs. On the contrary, due to shorter reaction period (<60 d) of ⁸⁵Sr with soil components, ⁸⁵Sr was mainly in exchangeable form and partially in the forms bound to carbonates and oxides in the soils amended with ⁸⁵Sr.     

磷石膏作水泥缓凝剂的试验研究

介绍了磷石膏的主要化学成份，矿物组成和水泥 磷石膏的物理力学性能。它可以代替天然石膏作水泥缓剂加紧开发利用。     

放射性污染防治对策与建议

根据2001年浙江省放射性申报登记试点城市－－嘉兴市的申报登记结果，在分析该市的放射性污染控制现状和管理现状的基础上，结合该市的实际情况，对放射性污染管理防治工作中存在的问题和薄弱环节，有针对性地提出嘉兴市放射性污染防治对策与建议，供有关部门参考。     

Management of Lignite Fly Ash for Improving Soil Fertility and Crop Productivity

Lignite fly ash (LFA), being alkaline and endowed with excellent pozzolanic properties, a silt loam texture, and plant nutrients, has the potential to improve soil quality and productivity. Long-term field trials with groundnut, maize, and sun hemp were carried out to study the effect of LFA on growth and yield. Before crop I was sown, LFA was applied at various doses with and without press mud (an organic waste from the sugar industry, used as an amendment and source of nutrients). LFA with and without press mud was also applied before crops III and V were cultivated. Chemical fertilizer, along with gypsum, humic acid, and biofertilizer, was applied in all treatments, including the control. With one-time and repeat applications of LFA (with and without press mud), yield increased significantly (7.0–89.0%) in relation to the control crop. The press mud enhanced the yield (3.0–15.0%) with different LFA applications. The highest yield LFA dose was 200 t/ha for one-time and repeat applications, the maximum yield being with crop III (combination treatment). One-time and repeat application of LFA (alone and in combination with press mud) improved soil quality and the nutrient content of the produce. The highest dose of LFA (200 t/ha) with and without press mud showed the best residual effects (eco-friendly increases in the yield of succeeding crops). Some increase in trace- and heavy-metal contents and in the level of γ-emitters in soil and crop produce, but well within permissible limits, was observed. Thus, LFA can be used on a large scale to boost soil fertility and productivity with no adverse effects on the soil or crops, which may solve the problem of bulk disposal of fly ash in an eco-friendly manner.     

A study on the elimination of 137Cs in mussels under contaminated fields and laboratory conditions

The natural depuration or bioelimination of ^l37Cs was investigated in Mytilus galloprovincialis under contaminated field and laboratory conditions. The depuration result represented by a single component and biological half‐life was found to be 63 days under Chernobyl condition during 1986–1987. On the other hand, the biological half‐life of ¹³⁷Cs were found in the range 19.7–27.1 days in the laboratory experiment. The bioelimination process was also found biphasic and dependent of temperature at 5°C and 13°C under laboratory conditions. The results obtained in the contaminated field and the laboratory are not comparable in the mussels.