TF5池火平均质量损失速率简化模型及其高原环境下的适用性研究

通过池火在常压环境下燃烧时的质量损失机理分析,对火灾探测中欧洲标准试验火TF5(正庚烷池火)归纳推导出以辐射热反馈为主导的质量损失速率简化模型,并推广到拉萨高原低压环境.该模型建立了TF5池火平均质量损失速率与火焰温度四次方的正比关系,通过对火焰温度的测量,确定燃料液面所受的辐射热反馈功率,从而推算出燃料的平均质量损失速率.同时结合合肥及拉萨两地的TF5标准火实验,对模型进行了验证,实验结果表简化模型能够反映出不同气压下TF5池火燃烧的主要过程.     

Radiological risk assessment and biosphere modelling for radioactive waste disposal in Switzerland

Long-term safety assessments for geological disposal of radioactive waste in Switzerland involve the demonstration that the annual radiation dose to humans due to the potential release of radionuclides from the waste repository into the biosphere will not exceed the regulatory limit of 0.1 mSv. Here, we describe the simple but robust approach used by Nagra (Swiss National Cooperative for the Disposal of Radioactive Waste) to quantify the dose to humans as a result to time-dependent release of radionuclides from the geosphere into the biosphere. The model calculates the concentrations of radionuclides in different terrestrial and aquatic compartments of the surface environment. The fluxes of water and solids within the environment are the drivers for the exchange of radionuclides between these compartments. The calculated radionuclide concentrations in the biosphere are then used to estimate the radiation doses to humans due to various exposure paths (e.g. ingestion of radionuclides via drinking water and food, inhalation of radionuclides, external irradiation from radionuclides in soils). In this paper we also discuss recent new achievements and planned future work.     

Escaping radioactivity from coal-fired power plants (CPPs) due to coal burning and the associated hazards: a review

Coal, like most materials found in nature, contains trace quantities of the naturally occurring primordial radionuclides, i.e. of ⁴⁰K and of ²³⁸U, ²³²Th and their decay products. Therefore, the combustion of coal results in the released into the environment of some natural radioactivity (1.48 TBq y⁻¹), the major part of which (99 %) escapes as very fine particles, while the rest in fly ash. The activity concentrations of natural radionuclides measured in coals originated from coal mines in Greece varied from 117 to 435 Bq kg⁻¹ for ²³⁸U, from 44 to 255 Bq kg⁻¹ for ²²⁶Ra, from 59 to 205 Bq kg⁻¹ for ²¹⁰Pb, from 9 to 41 Bq kg⁻¹ for ²²⁸Ra (²³²Th) and from 59 to 227 Bq kg⁻¹ for ⁴⁰K. Fly ash escapes from the stacks of coal-fired power plants in a percentage of 3-1% of the total fly ash, in the better case. The natural radionuclide concentrations measured in fly ash produced and retained or escaped from coal-fired power plants in Greece varied from 263 to 950 Bq kg⁻¹ for ²³⁸U, from 142 to 605 Bq kg⁻¹ for ²²⁶Ra, from 133 to 428 Bq kg⁻¹ for ²¹⁰Pb, from 27 to 68 Bq kg⁻¹ for ²²⁸Ra (²³²Th) and from 204 to 382 Bq kg⁻¹ for ⁴⁰K. About 5% of the total ash produced in the coal-fired power plants is used as substitute of cement in concrete for the construction of dwellings, and may affect indoor radiation doses from external irradiation and the inhalation of radon decay products (internal irradiation) is the most significant. The resulting normalized collective effective doses were 6 and 0.5 man-Sv (GW a)⁻¹ for typical old and modern coal-fired power plants, respectively.     

Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the first arrival of the airborne fission products ¹³¹I, ¹³²I, ¹³²Te, ¹³⁴Cs, and ¹³⁷Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. We measured the evolution of the activities over a period of 23 days at the end of which the activities had mostly fallen below our detection limit. The highest detected activity from radionuclides attached to particulate matter amounted to 4.4 ± 1.3 mBq m⁻³ of ¹³¹I on 19-20 March.     

Simulation of aerosol direct radiative forcing with RAMS-CMAQ in East Asia

The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols, including sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements of EANET (Acid Deposition Monitoring Network), AERONET (Aerosol Robotic Network), and CSHNET (Chinese Sun Hazemeter Network). The correlation coefficients of the comparisons of daily average mass concentrations of sulfate, PM2.5, and PM10 between simulations and EANET measurements are 0.70, 0.61, and 0.64, respectively. It is also determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the high AOD values ranging from 0.8 to 1.2 are mainly distributed over the Sichuan Basin as well as over central and southeastern China, in East Asia. The aerosol direct radiative forcing patterns generally followed the AOD patterns. The strongest forcing effect ranging from −12 to −8 W m⁻² was mainly distributed over the Sichuan Basin and the eastern China’s coastal regions in the all-sky case at TOA, and the forcing effect ranging from −8 to −4 W m⁻² could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan     

高风险移动放射源风险管控模糊综合评价

根据高风险移动放射源辐射安全风险特点与辐射事故经验反馈,结合辐射安全监管部门和企业实际,在充分调研的基础上,构建高风险移动放射源辐射安全风险管控评价指标体系,体系分为目标层、准则层和方案层,准则层8项指标,方案层40项指标。采用层次分析法确定各指标权重,运用模糊综合评价方法对甘肃省7家高风险移动放射源企业进行评价,结果表明决策层指标权重较大,与实际情况相符。     

Measurement of natural radioactive nuclide concentrations in various metal ores used as industrial raw materials in Japan and estimation of dose received by workers handling them

Natural resources such as ores and rocks contain natural radioactive nuclides at various concentrations. If these resources contain high concentrations of natural radioactive nuclides, workers handling them might be exposed to significant levels of radiation. Therefore, it is important to investigate the radioactive activity in these resources. In this study, concentrations of radioactive nuclides in Th, Zr, Ti, Mo, Mn, Al, W, Zn, V, and Cr ores used as industrial raw materials in Japan were investigated. The concentrations of ²³⁸U and ²³²Th were determined by inductively coupled plasma mass spectrometry (ICP-MS), while those of ²²⁶Ra, ²²⁸Ra, and ⁴⁰K were determined by gamma-ray spectrum. We found the concentrations of ²³⁸U series, ²³²Th series, and ⁴⁰K in Ti, Mo, Mn, Al, W, Zn, V, and Cr ores to be lower than the critical values defined by regulatory requirements as described in the International Atomic Energy Agency (IAEA) Safety Guide. The doses received by workers handling these materials were estimated by using methods for dose assessment given in a report by the European Commission. In transport, indoor storage, and outdoor storage scenarios, an effective dose due to the use of Th ore was above 4.3 × 10⁻² Sv y⁻¹, which was higher than that of the other ores. The maximum value of effective doses for other ores was estimated to be about 4.5 × 10⁻⁴ Sv y⁻¹, which was lower than intervention exemption levels (1.0 × 10⁻³ Sv y⁻¹) given in International Commission of Radiological Protection (ICRP) Publication 82.     

大气棕色碳的研究进展与方向

有机气溶胶是大气气溶胶的重要组成部分.近年来,部分有机气溶胶被证实在紫外-近可见光波段能进行有效光吸收.吸光有机气溶胶(即棕色碳)已成为当前国际大气环境领域的研究热点之一,其吸光贡献对辐射强迫、区域空气质量、全球气候变化的影响备受关注.中国城市群区域大气复合污染严重,2013年1月以来,大尺度区域能见度降低、灰霾现象频繁发生.研究表明,中国大气棕色碳的负荷高,其重要贡献源类如生物质与化石燃料燃烧等排放量大,棕色碳在中国大气细颗粒物总消光中的贡献及其辐射强迫亟需评估.然而,棕色碳的基础研究还较为薄弱,特别是对它的组成及来源的认识仍十分有限.本文旨在指出在中国开展大气棕色碳研究的紧迫性和必要性,并从棕色碳的来源、组成、测量方法、浓度分布、光学特性、辐射强迫贡献等角度介绍目前国际研究进展,提出现有问题与不足,以及对未来研究方向的建议,以促进对棕色碳的认识与了解,为中国在该领域的研究提供参考和依据.     

气候试验需要注意的几个问题

本文对气候试验要注意的几个问题进行探讨,有助于提高试验质量.