有关氡子体平衡因子对暴露量和有效剂量估算值影响的初步讨论

１前言平衡因子Ｆ定义为平衡等效氡浓度与空气中母体核素氡放射性浓度的比值。它表征了用α潜能表示的空气中短寿命子体混合物与其母体核素之间的不平衡状态。近年来，在氡水平调查中，有不再测量氡子体的趋势，在剂量评价中采用ＩＣＲＰ及ＵＮＳＣＥＡＲ推荐的平衡因子...     

矿物开采和加工中天然放射性物质的辐射防护

目的 加强矿物开采和加工中天然放射性物质的辐射防护管理的科学性,与国际通行准则的限值和管理措施相一致。方法 简述了IAEA和我国标准中适用于含天然放射性物质矿物开采和加工中辐射防护限值和管理措施。结果 国际相关天然放射性物质防护导则中对γ外照射剂量+粉尘内照射剂量(氡及其子体除外)低于1 mSv/a或大宗物料中铀、钍系放射性核素活度浓度≤ 1 Bq/g给予豁免管理,高于以上两限值的情况进行优化分级管理。结论 国内相关NORM辐射防护管理的实践,应以国际通行准则为基础,不断总结经验,进一步补充完善,可逐步推广应用于其他含天然放射性核素较高矿物开采和加工行业的辐射防护。     

我国部分地区煤矿原煤中天然放射性水平调查分析

目的 了解我国部分地区煤矿原煤中天然放射性核素⁴⁰K、²²⁶Ra、²³²Th和²³⁸U的活度浓度,探讨不同活度浓度的矿石与工作场所氡及其子体浓度的关联性。方法 采集5省12家煤矿的原煤样品,使用高纯锗γ能谱测量系统测量其中的⁴⁰K、²²⁶Ra、²³²Th和²³⁸U活度浓度。结果 12家煤矿原煤样品中4种天然放射性核素活度浓度均低于1000 Bq/kg,其中有1家煤矿²³⁸U活度浓度接近100 Bq/kg;不同煤矿⁴⁰K、²²⁶Ra、²³²Th和²³⁸U的含量差别很大,但对同一煤矿²²⁶Ra、²³²Th和²³⁸U含量基本在相同水平上。结论 12家煤矿均不属于伴生放射性矿,有1家煤矿接近限制使用管理类矿山标准限值,建议开展原矿、中间产品、尾矿（渣）或者其他残留物中²²⁶Ra的含量与氡及其子体浓度的关联性研究,并对²²⁶Ra、²³²Th和²³⁸U 3种天然放射性核素活度浓度较高的煤矿加强其衰变链中氡及其子体监测与防护。     

某厂放射卫生调查

对某非放射性工厂进行了包括γ辐射水平、氡及氡子体浓度、天然放射性核素活度为主的调查测试。并对该地居民的受照剂量进行了估算。结果表明,该地区地球γ辐射水平较高,高值可达131.6×10~(-8)Gyh~(-)1。厂区和住宅区室内外的氡及子体浓度均高于全省水平,厂属莹石矿中的平衡当量氡浓度高达210.90Bqm~(-3)。剂量估算结果表明,该厂职工每年受到1mSv以上的附加照射,其中部分职工受到12.84mSva~(-1)的附加照射。所以,非放射性单位由于地理环境、气象条件及放射性矿分布等因素影响,工作场所及环境中放射性水平增高,甚至对居民健康产生一定影响,是不容忽视的。     

2018年参加全国放射性核素γ能谱分析比对结果

目的 验证本实验室所用的γ能谱测量系统,确认γ放射性核素测量分析方法和技术的可靠性。方法 通过参加2018年中国疾病预防控制中心辐射防护与核安全医学所组织的全国放射性核素γ能谱质量控制分析比对,分别用相对比较法和效率曲线法分析土壤样品中核素²³²Th、⁴⁰K、¹³⁷Cs的活度浓度。结果 相对比较法测得的3种核素的活度浓度与参考值的偏差为0%~14.1%,U检验值为0.15~2.35;效率曲线法测得的3种核素的活度浓度相对参考值的偏差为2.8%~18.5%,U检验值为0.42~2.58,均在合格范围内。结论 本实验室所用的γ能谱测量系统性能稳定,分析方法可靠,但测量结果与参考值的相对偏差较大,实验室质量控制技术有待进一步完善。     

2014-2015年宁夏食品中放射性核素监测结果分析

目的 了解2014-2015年宁夏食品中放射指标污染状况,掌握食品中放射性平均活度水平基础资料。方法 主要依据《食品中放射性物质检验(总则)》(GB14883.1-94)、《高纯锗γ能谱分析通用方法》GB/T11713-2015。采用Canberra公司 BE3830高纯锗γ谱仪对采集的食品中的放射指标进行检测。检测结果依据GB 14882-94《食品中放射性物质限制浓度标准》的限量规定进行评价。结果 32份样品中均未检出131I、134Cs、137Cs、60Co、58Co等人工放射性核素。其中有5份菠菜样品,全部检出了微量的人工放射性核素90Sr,检出率达100％;天然放射性核素238U、232Th、226Ra的比活度值2015年的检测结果比2014年的明显降低;天然放射性核素40K在所有被检食品中均有检出,2015较2014略有变化。结论 虽然不同食品中放射性含量有一定差异,但均低于国家标准GB 14882-1994《食品中放射性物质限制浓度标准》规定的限值范围。     

淄博市生活饮用水放射性水平的分析

目的 通过调查淄博市生活饮用水中总α、总β、铯-137、锶-90等活度浓度,研究当地居民生活饮用水的放射性水平、人工核素活度浓度水平以及用于剂量估算的主要放射性核素。方法 依据《生活饮用水标准检验方法:放射性指标》(GB/T 5750.13-2006)、《水中放射性核素的γ能谱分析方法》(GB/T 16140-1995)和《水中锶-90放射化学分析方法二-(2-乙基己基)磷酸酯萃取色层法》(GB 6766-86),使用低本底总α、总β测量设备及HPGe γ能谱仪进行样品总α、总β与锶-90、碘-131等等核素的分析测量。结果 淄博市张店区生活饮用水中总α活度浓度范围为59~168 mBq/L,总β活度浓度范围为67~255 mBq/L,⁹⁰ Sr活度浓度范围为3.5~4.5 mBq/L,²²⁶Ra活度浓度范围为6.0~10.2 mBq/L,²³² Th活度浓度范围为4.3~7.2 mBq/L,⁴⁰ K活度浓度范围为65~154 mBq/L,²³⁸ U活度浓度范围为51~92 mBq/L。结论 淄博市生活饮用水放射性物质含量处在正常本底水平,可以正常饮用。     

福清核电站周边地区食品放射性核素本底调查

目的掌握福清核电站周边地区运行前期食品放射性核素本底值,为长期监测比对提供参考。方法采集核电站周围30km范围内居民日常食用的13种食品样品,预处理后用高纯锗γ谱仪检测食品中的放射性核素。结果福清核电站周边地区食品样品中检出的放射性核素,是天然核素238 U、232 Th、226 Ra、40 K以及人工核素137 Cs,放射性活度浓度水平均低于国家标准限值。结论福清核电站30km范围内居民日常食用的食品中,人工和天然放射性核素活度浓度均处在本底水平,膳食摄入后对人体造成的剂量负担较小,但仍需继续监测。     

居室环境放射性现状评价

目的 为了掌握居室环境放射性水平,并对当前室内环境的放射性水平做出评价。方法 使用自制的"室内环境放射性评价测量盒"(专利号:ZL200620082698.7)对室内环境中²²²Rn活度浓度、²²⁰Rn活度浓度、²²⁰Rn子体的平衡当量浓度(EEC_Tn)以及γ外照射剂量率进行测量。结果 测量济南市室内²²²Rn共411间次,活度浓度范围为18~203Bq·m^-3,呈对数正态分布,几何均值为45Bq·m^-3;测量室内²²⁰Rn共203间次,其活度浓度范围为1~167Bq·m^-3,几何均值为16Bq·m^-3;测量室内²²⁰Rn子体的平衡当量浓度共204间次,其活度浓度范围为0.015~10.230Bq·m^-3,几何均值为1.082Bq·m^-3;测量室内γ外照射剂量率共412间次,其γ外照射剂量率范围为0.041~0.167μSv·h^-1,呈正态分布,算术均值为0.106μSv·h^-1。结论 居民由²²²Rn及其子体造成的内照射剂量为1.189mSv/a;由²²⁰Rn及其子体造成的内照射剂量为0.255mSv/a;由γ外照射外照射剂量为0.743mSv/a;年均总剂量为2.187mSv,最大年均剂量已超过5mSv。     

2011—2015年我国环境天然辐射水平分析

目的 以国家辐射监测网监测数据为基础，从空气吸收剂量率、空气、水、土壤等方面对2011—2015年全国环境天然辐射水平进行分析和总结。方法 通过查阅相关资料、整理、归类和总结了2011—2015年我国空气、水和土壤中的天然辐射水平监测数据。结果 2011—2015年，自动站空气吸收剂量率年均值范围为88～92 nGy/h，累积剂量测得的空气吸收剂量率年均值范围为97～99 nGy/h，空气、水和土壤中天然放射性核素活度浓度均在日常涨落范围内。结论 自动站连续空气吸收剂量率、地级及以上城市累积剂量测得的空气吸收剂量率处于当地天然本底涨落范围内，气溶胶和沉降物中天然放射性核素活度浓度处于本底水平，江河水、湖（库）水、海水及土壤中天然放射性核素活度浓度在日常涨落范围内，且与1983—1990年全国环境天然放射性水平调查结果处于同一水平。     

Measuring method of undamaged samples for the radiation levels of decorative building materials

When natural radionuclides are well distributed in materials, there is a fixed interrelationship between activities in any part of the material and the surface flux of alpha and beta rays. Placing an alpha detector on the surface can estimate radionuclide activities in the materials without damaging samples. This paper studied the relationship between gamma ray specific activities of natural radionuclides and alpha ray surface flux of decorative building materials. The results show that when the surface alpha ray activities of granite are less than 0.0052 Bq cm, or the surface alpha ray activities of polished tiles are less than 0.0082 Bq cm, their internal and external exposure indexes are in the range of "A" limits of national criteria of China, Limit of radionuclides in building materials. Because there is a great difference between the radioactive levels of the surface glaze and the matrix of color-glazed tiles, the natural radionuclides are not well distributed in color-glazed tiles, and the ratio between the alpha surface activity and the gamma ray activity in unit mass is not fixed. The surface alpha ray flux of materials cannot be used to estimate the internal and external exposure indexes of color-glazed tiles.     

Natural soil gamma radioactivity levels and resultant population dose in the cities of Zacatecas and Guadalupe,Zacatecas, Mexico

The study of natural gamma radioactivity was made to determine the concentrations of natural radionuclides in soil. Twenty soil samples collected in the cities of Zacatecas and Guadalupe and their suburban areas in the Mexican state of Zacatecas were analyzed by gamma-ray spectrometry to determine the activity concentrations of 226Ra, 232Th, and 40K. Gamma-spectrometry measurements were made using a hyperpure germanium detector surrounded with shielding material to reduce the background counting rate. The GammaVision-32 MCA emulation software was used for gamma-ray spectrum analysis and the TRUMP card of 2k as a MCA emulator. Conversion factors were used to calculate the dose to the population from outdoor exposure to terrestrial gamma rays. The measured activity concentration of 226Ra varies from 11 to 38 Bq kg(-1), the activity concentration of 232Th varies from 8 to 38 Bq kg(-1). The activity concentration of 40K is in the range 309-1,049 Bq kg(-1). The overall population mean outdoor terrestrial gamma dose rate is 44.94 nGy h(-1).     

The studies on radiological limits of color-glazed tiles used in home decoration

This study was carried out to lay down the radiological limits of color-glazed tiles used in home decoration. The activity concentrations of various end products and raw materials as well as processed materials were measured using gamma spectroscopy. 222Rn exhalation rates from the surface of color-glazed tiles were measured using charcoal canister method. Levels of exposure to alpha ray and beta ray from the surface of glazed tiles were measured by surface alpha and beta contaminant instrument. The results show a great difference between the radioactive levels of the surface glaze and the matrix of color-glazed tiles. The 222Rn exhalation rates from the surface of color-glazed tiles are in the range of 10(-3) - 10(-4) Bq m(-2) s(-1). The concentrations of some natural radionuclides in glaze exceed the exempt limits of International Basic Safety Standards for Protection against Ionizing Radiation Sources (IAEA 1997). The limits for color-glazed tiles were deduced according to these data and the theory of UNSCEAR (1993). The activity concentration of 226Ra (Bq kg(-1)) in the glaze of color-glazed tiles should be in the range of A(226Ra) < or = 1,000 (Bq kg(-1)), and, at the same time, the specific activity of the natural radionuclides (Bq kg(-1)) should be in the range of A(232Th)/230 + A(226Ra)/310 + A(40K)/3,500 < or = 1.     

A study on natural radioactivity in khewra salt mines, pakistan

The Khewra Salt Mines, the second largest salt mines in the world, are located 160 km south of Islamabad, the capital of Pakistan. Around 1000 workers are involved in the removal of salt from these mines. More than 40,000 visitors come annually to see the mines. The visitors and workers are directly exposed to the internal and external radiological hazards of radon and gamma rays in these mines. The general public is affected by the intake of the salt containing the naturally occurring radionuclides. Therefore the concentration of radon (²²²Rn) in the Khewra Salt Mines and activity concentrations of the naturally occurring radionuclides in the salt samples from these mines were measured. Both active and passive techniques were employed for the measurement of radon with Radon Alpha Detector (RAD-7) and SSNTD respectively. The concentration of ²²²Rn was 26 ± 4 Bq m^-3 measured by the active method while 43 ± 8 Bq m^-3 was measured by the passive method. The activity concentration of the radionuclides was measured using gamma ray spectrometry with HPGe detector. The mean activity of ⁴⁰K in salt samples was found to be 36 ± 20 Bq kg^-1 and the concentration of ²²⁶Ra and ²³²Th in the salt samples was below the detection limits. Gamma radiation hazard was assessed in terms of the external gamma dose from salt slabs and the rooms made of salt and the annual effective dose due to gamma radiation. The exposure to radon daughters, annual effective dose and excessive lifetime cancer risk due to radon in the mines were estimated. The mean annual effective dose due to an intake of ⁴⁰K from the salt was calculated as 20.0 ± 11.1 μSv, which is lower than the average annual effective dose rate of 0.29 mSv, received by the ingestion of natural radionuclides. Due to the low concentration values of primordial radionuclides in the salt and radon (²²²Rn) in the mines, a 'low level activity measurement laboratory' is suggested to be established in these mines.     

Continuous monitoring for airborne alpha emitters in a dusty environment

Disposal of radioactive wastes in underground facilities requires continuous monitoring for airborne radioactive materials, both on the surface and underground. In addition to a natural background of nonradioactive and radioactive aerosols, there may be a sizeable dust contribution from ongoing work such as mining and vehicular traffic. In the monitoring of alpha-emitting radionuclides, these aerosols may lead to self-absorption in the source and a deterioration of the energy spectrum of the detected alpha particles. In this paper, the influence of a realistic background aerosol on the performance of an alpha monitoring system is evaluated theoretically. It is shown that depositing alpha emitters and background aerosol on a surface for counting leads rapidly to a considerable loss of counts, a deterioration of the alpha spectra, an eventual saturation of the count rates, and interference from the natural background of Rn daughters.     

Radiological implications of granite of northern Pakistan

Granite is an igneous rock that contains natural radioactivity of primordial radionuclides. In Pakistan, granite is distributed in a vast area called the Ambela Granitic Complex (AGC) in North West Frontier Province (NWFP). Granite is a hard rock that exists in different colours and is used to decorate floors, kitchen counter tops, etc. The use of granite in a building as a decor material is a potential source of radiation dose; therefore, natural radioactivity has been measured in 20 granite samples of the AGC with an HPGe (high purity germanium) based gamma ray spectrometer. The average specific activities and their range (given in parentheses) for primordial radionuclides (40)K, (226)Ra and (232)Th were 1218 (899-1927), 659 (46-6120) and 598 (92-3214) Bq kg(-1), respectively. The measured activity concentrations were used for the assessment of hazard indices and radiation dose which were evaluated based on the permissible limits defined for these parameters. The measured specific activities and the derived quantities, hazard indices and radiation dose, have been compared with those given in the literature for these parameters.     

In-situ determination of deposited radionuclide activities: improved method using derived depth distributions from the measured photon spectra.

When applying the standard method of in-situ gamma spectrometry to determine deposited radionuclide activities, an assumption is needed regarding the depth distribution of radionuclides in the ground. The method can be improved by assessing, from information contained in the spectrum, the attenuation of the radiation by the soil and vegetation. By comparing the count rates of the x ray and the gamma-ray lines of its daughter nuclide 137mBa, the 137Cs activity per area can be determined. The range of applicability of the method is discussed by means of an uncertainty analysis, and the method is applied to post-Chernobyl measurements. A comparison with the results of the standard method of in-situ spectrometry demonstrates the progress achieved by the proposed method. Nevertheless, the method still has some shortcomings for the peak analysis that could be improved by better detector resolution or better computer software.     

Radioactive waste due to electric power and mineral fertiliser production

Radiation Protection Unit of the Institute for Medical Research and Occupational Health in Zagreb has been conducting systematic investigations of radioactive contamination of the Croatian environment by anthropogenic fission products as well as by naturally occurring radioactive material (NORM) since 1963. Several critical sites in Croatia were identified for NORM, that is, for slag and ash repositories from coal-fired power plants and phosphogypsum repository from a mineral fertilizer production plant. As the coals and phosphate ores contain naturally occurring radionuclides, especially the members of the uranium and thorium radioactive chains, utilising these materials in various industries only enhances their natural radioactivity in residual waste. Consequently, the resulting activity concentrations of natural radionuclides in waste material could be several times higher than in the adjacent soil. These deposited materials pose permanent risk of radiation exposure due to the long physical half-life of natural radionuclides (e.g., T 1/2 = 1600 years for 226Ra). Results of scientific investigations related to natural radioactivity are used in the recovery of slag and ash repositories and landfills, as well as in establishing regulatory criteria targeting import of coal and phosphate ores. In consequence, recently measured activity concentrations of natural radioactivity in imported materials used nowadays in coal-fired power plants are significantly lower than in previously used raw materials. Therefore, slag and ash can be used as additive materials in cement production.     

石煤灰渣建材辐射环境影响评价

目的 对我国某石煤综合利用项目灰渣建材的辐射环境影响进行了预测评价研究。方法 通过石煤灰渣中放射性核素浓度估算灰渣建材中放射性核素浓度,评估对公众造成的辐射剂量及建材的辐射射风险指数。结果 石煤灰渣用作建筑主体材料后将明显增高公众辐射照射剂量,包括γ辐射外照射和氡吸入内照射剂量。结论 建议根据灰渣建材的工艺,加强监测和管理,有选择地用于建材生产,满足国家标准对建材中放射性核素限量的要求,减少公众使用石煤灰渣建材而受到的辐射照射。     

Parenting Practices, Parents' Underestimation of Daughters' Risks, and Alcohol and Sexual Behaviors of Urban Girls

PURPOSE: In urban economically distressed communities, high rates of early sexual initiation combined with alcohol use place adolescent girls at risk for myriad negative health consequences. This article reports on the extent to which parents of young teens underestimate both the risks their daughters are exposed to and the considerable influence that they have over their children's decisions and behaviors. METHODS: Surveys were conducted with more than 700 sixth-grade girls and their parents, recruited from seven New York City schools serving low-income families. Bivariate and multivariate analyses examined relationships among parents' practices and perceptions of daughters' risks, girls' reports of parenting, and outcomes of girls' alcohol use, media and peer conduct, and heterosexual romantic and social behaviors that typically precede sexual intercourse. RESULTS: Although only four parents thought that their daughters had used alcohol, 22% of the daughters reported drinking in the past year. Approximately 5% of parents thought that daughters had hugged and kissed a boy for a long time or had "hung out" with older boys, whereas 38% of girls reported these behaviors. Parents' underestimation of risk was correlated with lower reports of positive parenting practices by daughters. In multivariate analyses, girls' reports of parental oversight, rules, and disapproval of risk are associated with all three behavioral outcomes. Adult reports of parenting practices are associated with girls' conduct and heterosexual behaviors, but not with their alcohol use. CONCLUSION: Creating greater awareness of the early onset of risk behaviors among urban adolescent girls is important for fostering positive parenting practices, which in turn may help parents to support their daughters' healthier choices.