At present, more than 30 countries and regions have established nuclear power station, and nuclear safety has become a problem that should be paid more attention in the development of nuclear energy in future. From the first nuclear power station of the world to the present, in the past 60 years of nuclear power development, there were once more than 10 nuclear accidents of different scales, especially were Chernobyl nuclear accident in 1986 and the Fukushima nuclear accident in 2011 which were two most serious seven grade nuclear accidents in mankind history. Therefore, nuclear accident, especially serious accident, has enormously affected society. And nuclear leak event could affect strategic direction of nuclear development of many countries, and involve how to ensure nuclear safety under the influence of special event and involve nuclear safety culture. Besides, it also provided valuable experience and lessons for international society about how to deal with nuclear accident. The safety of nuclear electric power generation is basic principle that must be persisted by competent department. And only when the nuclear safety is ensured, it can promote nuclear power to achieve enormous development.

This study represents a total of 245 samples collected. The activities of (238)U, (228)Ra, (226)Ra, (40)K and (137)Cs were determined in samples of vegetables, tea, cereal (rice, wheat and corn), meat, poultry, freshwater product, seafood and seaweed that collected from the 30km safety zone of the Nuclear Power Plants (NPPs) area. All the samples radionuclide activities were quantified by using High Purity Germanium (HPGe) gamma spectrometry. The geometric mean concentrations (Bqkg(-1) wet weight) for (238)U, (228)Ra, (226)Ra, (40)K, and (137)Cs in all investigated foodstuffs samples, are 0.13, 0.16, 0.11, 68 and 0.02, respectively. The arithmetic mean concentrations (Bqkg(-1) wet weight) for (238)U, (228)Ra, (226)Ra, (40)K, and (137)Cs in all investigated foodstuffs samples, are 0.34, 0.65, 0.32, 111 and 0.09, respectively. Results of this study were compared with others, the measured values are the same with those of a previous investigation. Radiation doses due to the consumption of these foodstuffs to humans are estimated to comprise around 37-46% of the annual dose limit for public.

目的 对海南部分地区土壤样品中的放射性水平进行评估.方法 在2012年期间,为了评估土壤中放射性,在中国海南省收集表层土壤样品.用低本底高纯锗γ谱仪测量了15个土壤样品中的放射性.结果 样品中226Ra、232Th和40K的平均放射性浓度分别为(26.3±1.0),(23.7±0.90)和(366.1±13.4)Bq·kg-1.而137Cs的活度浓度变化范围值＜ 0.35 Bq·kg-1(最小可探测活度浓度)到2.25 Bq·kg-1.通过使用土壤样品中226Ra、232Th和40K的数据结果推算户外空气中γ剂量率值为(41.7±1.5)nGy·h-1.土壤中放射性核素所致居民人均外照射年有效剂量为0.05 mSv.结论 土壤样品分析结果表明,所有调查点的测量结果属正常环境水平,未见异常.

Objective: To test the accuracy of method of efficiency calibration by source less calibration. Methods:The energy spectrum in the same HPGe gamma, were calibrated by using the source less calibration and actual calibration technique for the same specification of the water samples, the efficiency value of relative deviation was compared. Results:Two efficiency calibration curve used by source less calibration and actual calibration were generated, the maximum relative deviation of the two methods is less than 10%, for most of the points the values are less than 3%. Conclusion:For the water samples, the efficiency obtained by source less calibration are in good agreement with the actual calibration data, so the efficiency calibration technique of source less calibration can be applied in various kinds of water samples for gamma spectrometry analysis.

Objective:To quickly monitor radioactive contamination of open crops. It is necessary to study the feasibility of monitoring radioactive contamination of open crops by gamma-ray real-time imaging system. Methods:To introduce the composition and working principle of portable gamma-ray real-time imaging system, and to expand its performance and functionality, and to test its imaging capabilities and dose rate measurement accuracy by using theγ-calibration gauge of national secondary standard laboratory. Results:The results of testing portable gamma-ray real-time imaging system by 137Cs and 60Co point source of γ-calibration gauge show clear image and distinguish the bound of radioactive pollution Accurately, and the dose rate measured at the minimum relative deviation of less than 3%, maximum relative deviation of 30.6%. Conclusion:Portable gamma-ray real-time imaging system can distinguish the bound of radioactive pollution accurately and measure dose rate accurately. So it can be well applied to the monitoring of open crops in nuclear accident.

An intercomparison of γ-spectrometry measurement and analysis was organized by the Japan Chemical Analysis Center (JCAC), the National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention (NIRP, China CDC), and the Radiation Monitoring Technical Center of Ministry of Environmental Protection, Chinese (RMTC). The main objective of this study was to assess the γ-spectrometry measurement and analysis technology. The JCAC completed the collection and preparation of soil and powdered rice samples. Three laboratories compared the measurement of seven radionuclides that included two samples of (214)Pb, (214)Bi, (208)Tl, (228)Ac, (40)K, (137)Cs, and (134)Cs with γ-spectrometry. During the studies conducted at the laboratory, the calculated value En was found to be the total uncertainty data of the reported activity. Except (134)Cs in powdered rice sample, the calculated En between each of the two laboratories was <1. The measurement results are acceptable except (134)Cs; therefore, measurement results in the three laboratories were consistent within a certain range except in the case of (134)Cs. Although there is a need to improve the accuracy of measurements and analysis of (134)Cs, an intercomparison was conducted of the tested levels on radionuclide analyzed in the three laboratories.

Objective To improve the technical levels and analytical ability of γ-spectrometry analysts for agencies engaged in radiation measurement and assessment and to promote further advances of monitoring methods for γ-spectrometry analysis laboratories in our nation.Methods A nationwide intercomparison on γ-spectrometry measurement for activity concentration of 40K, 137Cs, 208Tl, and 208Ac in soil was organized in 2014.Results Thirty-one laboratories have participated in this intercomparison.Among these laboratories, 26 laboratories showed "acceptable" results, which include 2 laboratories with "excellent" status, while 5 laboratories showed "unacceptable" results.The production percentages of "acceptable" results and "excellent" status are 84％ (24/31) and 6％ (2/31), respectively.Conclusions The measurement values reported by most of the laboratories involved in this intercomparison showed a good agreement with the reference values.Therefore, these values may provide a reliable measurement result during measurement in γ-spectrometry analyses.However, proper operation of γ-spectrometers and its regular calibration must be further emphasized to obtain accurate measurements to improve the calculation of nuclear data in some laboratories.

Objective To survey the 238U radioactivity level in the surface soil in the Beijing-Tianjin-Hebei Border (BTHB) region,and to prepare a high resolution distribution map of 238U activity concentrations.Methods The soil samples were collected in a grid (10 km × 10 km).The activity concentrations of 238U in soil samples were measured by using HPGe γ spectrometry.The distribution of the activity concentrations of 238U in soil samples was mapped by the aid of MAPGIS software.Results In total,416 samples were collected and measured.The activity concentrations of 238U were in the range of 0.1-106.0 Bq/kg,with an average of 34.7 Bq/kg.The 238U activity concentration distribution map showed that 238U activity concentration was in the range of 15-55 Bq/kg mostly on the surface soil in the BTHB region.Conclusions The map of 238U activity concentration shows the distribution of 238U activity concentration in the BTHB region.It is of importance to map the distribution of 238U activity concentration in the BTHB region,by converting a huge amount of data into the simple and intuitive graphics,and for evaluating the regional environmental radioactivity and studying the radioactive substance migration within the locality.

Objective:To improve methods of sample preparation and radioactivity monitoring of food, and to establish fast method of sample pretreatment and radioactivity analyses.Methods: By changing the method of cylindrical backer filled with ash samples to Marinelli backer filled with powder samples, radionuclides in ten kinds of food samples, such as in spinach, carrots, beef, rice, tea, dried small shrimps, prawns, milk powder, seaweed and mushrooms, were analyzed by using gamma spectrometry. The minimum detectable concentration (MDC) obtained by the method were compared with that of cylindrical backer filled with ash samples.Results: Compared with that method of cylindrical backer filled with ash samples, pretreatment time for sample in this work can be shortened from seven days to one or three days under condition of automatically low-temperature drying, which also do not emit smoke or have flame, the MDC of the present methods are in the range of 0.02-0.180 Bq/kg for the137Cs if measure it for 72 hours.Conclusion: The time for sample pretreatment can be greatly shortened after use method of Marinelli backer filled with powder samples, and the corresponding MDC can be kept in the same order of magnitude with that method of using cylindrical backer filled with ash samples, so it can meet the requirements of monitoring.

Objective To determine the activity concentration of radionuclides for 137Cs and 40K in edible wild mushrooms,and to evaluate the extent of radioactive contamination and ingestion doses to adults from consumption of these wild mushrooms.Methods A total of 33 samples for 18 edible wild mushroom species were collected from natural forest Mangshi,Yunnan province.The activity concentrations of 137Cs and 40K were analyzed by using high-purity germanium (HPGe) gamma spectrometry.Results Except.for one sample that was below the MDA,137Cs artificial radionuclides were detected in other 32 samples,with activity concentration of 137Cs in the range of 0.45-339.58 Bq/kg (dry weight) and an average of 25.47 Bq/kg (dry weight).In regards to 40K in edible mushrooms,all species presented the activity concentrations for this radionuclide and the levels varied from 453.4 to 1 882.6 Bq/kg (dry weight),with an average of 815.1 Bq/kg (dry weight).After species of mushroom with only one sample were eliminated,there was significant difference for 137Cs(F =21.13,P ＜ 0.05) among 6 species of mushroom named Gomphus floccosus (Schw.) Sing.,Boletus edulis bull,Boletus edulis bull,Tylopllus bolloul (Peck) Sing.,Lentinus edodes (Berk.) Sing.and Boletus brunneissimus W.F.Chin,but without significant difference for 40K.Conclusions These 6 different mushroom species have different capacity to retain radionuclides of 137Cs in soil.These wild mushrooms,such as Gomphus floccosus (Schw.) Sing.and Lentinus edodes (Berk.) Sing.have large affinity ability for radionuclides137Cs.The effective dose to adults attributable to consuming these kinds of mushrooms is small and below the level that could cause harm.

Objective:To calculate the diffusion of airborne radioactive material fastly and accuratly when nuclear radiation emergencies occurs.Methods: Gaussian model were used for basis of the calculation, the conditions such as gravitational settling, ground reflection as well as radioactive decay and other factors were considered during the atmospheric dispersion calculation.Results: A software that can be used to calculate airborne radioactive material atmospheric dispersion under nuclear radiation emergencies were designed and developed. With tables, graphics and other forms downwind coordinates given in the results.Conclusion: This software can effectively reduce some difficulty of the calculation for the airborne spread of radioactive material, and can meet the need during nuclear radiation emergency response.

目的 在大气放射性核素监测中引入空气实时监测系统,建立空气实时监测方法.方法 以FHT59N2空气实时监测系统为代表,研究其能量刻度和效率刻度方法,建立能量刻度曲线和效率刻度曲线,分析该系统的运行模式特点,根据连续监测本底数据计算天然放射性核素的活度浓度和特定信号核素的检出限.结果 汇总了1d中40K、208 Tl、212pb、214Bi、214pb等天然放射性核素每5min的分析结果和1个月中这些核素每天监测结果均值并作图.确定131I、134Cs、137Cs等特定信号核素的检出限分别为5 mBq/m3、6 mBq/m3和6 mBq/m3.结论 空气实时监测系统可以较好的应用于大气放射性核素监测.

Six comparison exercises on radioactivity measurement by γ-spectrometry have been organized by NIRP in China since 2007. The type of measured nuclides changed from natural to man-made over this period. A total of 188 samples were prepared and distributed to 39 different participating laboratories and 528 radionuclide assays have been performed. A perceptible laboratory performance improvement was observed with the average percentage of acceptable scores being 87% in 2008, increasing to 92% in 2012.

Objective:To improve the monitoring sensitivity of air samples by using the fieldportable air sampler during of nuclear-related events.Methods:Portable air sampler parallel sampling combined with gamma spectroscopy methods and laboratory sourceless calibration software were used for the measuring analysis in the study.Results:After the parallelled in unit time,sample volume was doubled,the minimum detectable activity concentration of radionuclides decreased greatly.Conclusion:The monitoring sensitivity of suspected nuclear events could be significantly improved by using portable air sampler parallel sampling,measurement and analysis.

目的 调查我国核试验场下风向地区辐射剂量水平和居民健康状况.方法 以土壤中137Cs为主要研究核素,通过对土壤中137Cs沉积密度和分布的分析测定,估算我国核试验产生的裂变产物和活化产物所致下风向地区居民受内、外照射累积剂量.采用辐射流行病学方法,调查该地区4个县的10个乡1987-2000年恶性肿瘤死亡率和居民细胞遗传学分析.比较该地区不同时期观察指标以及该地区与国内其他地区、甘肃省的调查结果.结果 居民恶性肿瘤死亡率和淋巴细胞染色体畸变率在正常范围,它们的变化与照射剂量大小无相关性.结论 在我国大气层核试验停止20年后,核试验放射性落下灰造成的附加辐射剂量对下风向地区居民健康未见任何不良影响.

A total of 118 samples were analyzed using HPGe γ-spectrometry. (131)I, (134)Cs, (137)Cs and (136)Cs were detected in aerosol air samples that were collected 22 days after the accident with values of 1720 µBq m(-)³, 247 µBq m(-)³, 289 µBq m(-)³ and 23 µBq m(-)³, respectively. (131)I was detected in rainwater and soil samples and was also measurable in vegetables collected between April 2 and 13, 2011, with values ranging from 0.55 Bq kg(-1) to 2.68 Bq kg(-1). No (131)I was detected in milk, drinking water, seawater or marine biota samples.

In order to compare cosmic radiation dose for air crew including pilot and flight attendant between polar route flight and non-polar route flight, a typical polar flight route that is from Beijing to New York was selected and compared with non-polar route. Optically stimulated luminescence dosimeter and track etch detector CR-39 were worn as personal dosimeters to measure the cosmic radiation dose to air crew. The mean annual effective dose for air crew from polar route and non-polar route was (5.79 ± 0.92) mSv/year and (2.14 ± 0.64) mSv/year, respectively. The effective dose per 1,000 flight hours for air crew was (3.10 ± 0.27) mSv/1,000 h and (2.21 ± 0.46) mSv/1,000 h, respectively. The result is analyzed by using SPSS 15.0 statistical software. There was significant difference between the two groups for both mean annual effective dose (t = 30.25, P < 0.05) and the effective dose per 1,000 flight hours (t = 7.60, P < 0.05). The dose to pilot was higher than that of flight attendant for both polar route and non-polar route, and there was significant difference between them, for polar route (t = 7.96, P < 0.05), for non-polar route (t = 4.70, P < 0.05). The effective dose from cosmic radiation to air crew of polar route was higher than that of non-polar route, however, it did not exceed 20 mSv/year, which is the limit on cosmic radiation exposure set by many countries in the world.

Objective To detect artificial radionuclide content in the spinach and soil in open air vegetable garden in Beijing during Fukushima nuclear accident and to study the radioactive contamination characteristics of the samples.Methods 6 spinach samples and 3 soil samples in open air vegetable garden were obtained through continuously sampling.High-purity germanium (HPGe) γ spectrometry was used to analyze activity concentrations of artificial radionuclide131 Ⅰ etc in these samples.Results Artificial radionuclide 131Ⅰ was detected in the 6 open air spinach samples.Artificial radionuclide 137Cs was detected in 3 vegetable garden soil samples,trace amount of 131 Ⅰ was detected in 1 open-air surface soil sample alone.Conclusions Following the Fukushima nuclear accident,spinach in Beijing's open-air vegetable garden was slightly polluted by artificial radionuclide 131 Ⅰ,with the highest values of pollution appeared around April 4,2011,but it could not cause harm to human health.

Objective To determine the artificial radionuclides levels in environmental samples collected in some areas of China following the Japanese Fukushima nuclear accident,and to evaluate the extent of radioactive contamination.Methods A total of 118 samples including aerosol,water,soil and biological samples were collected and the activity concentrations of 131I, 137Cs and other artificial radionuclides were analyzed by using high-purity germanium (HPGe) γ spectrometry.Results Artificial radionuclides 131I,134Cs,137Cs and 136Cs were detected in the aerosol samples on 2 April,2011 and the activity concentrations were 1720,247,289,and 23 μBq/m3,respectively.Trace amount of 131I was detected in one sample of rain water and two samples of surface soil with concentrations of 2.08 Bq/L,1.82 and 0.59 Bq/kg,respectively.131I was also detected in 18 vegetable samples which were collected from 2 April to 13 April with the range of 0.55 -2.68 Bq/kg.Neither abnormal concentrations of 131I nor 137Cs was detected in milk,drinking water,sea water and marine products samples.Conclusions During the Fukushima nuclear accident,although minute quantities of radionuclides were detected in some samples collected in China,the effective dose for adults attributed to the nuclear accident is extremely small and significantly below the level that could cause harm to the public.

By using high-purity germanium gamma spectroscopy, specific activities of naturally occurring and man-made radionuclides were determined in topsoil samples collected from Nyingch, Lhasa and Xigazê of Tibet Autonomous Region, China. The average activity concentrations of (226)Ra, (232)Th and (40)K were 25.1 ± 0.7, 67.1 ± 2.8 and 608.6 ± 12.9 Bq kg(-1), respectively. The activity concentration of (137)Cs was found to vary from <0.3 (minimum detection concentration) to 46.2 Bq kg(-1) with an average of 4.3 ± 0.5 Bq kg(-1). By using the results of (226)Ra, (232)Th and (40)K in the sampled soils, the average outdoor gamma dose rate in air was calculated as 77.5 ± 23.2 nGy h(-1). Furthermore, the average outdoor annual effective dose from terrestrial radiation was 0.10 mSv. The external hazard index in this work varied from 0.20 to 0.70 with an average of 0.40 ± 0.14. The external exposure from terrestrial radiation will not pose any significant radiological threat to the population resident in the studied areas.