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Table of Content

    20 March 2018 Volume 38 Issue 2
      
    Indicators of safety case for the disposal of radioactive waste
    LI Jingjing, LIU Senlin, ZHANG Yanqi, LI Jinfeng, LIAO Haitao
    RADIATION PROTECTION. 2018, 38(2):  89-94. 
    Abstract ( 110 )   PDF (1005KB) ( 141 )  
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    As the concept of safety case for the disposal of radioactive waste was put forward, in addition to the radiological safety indicators (i.e., dose and risk), complementary indicators are widely accepted as important components of the safety case. The developments in the application, the categories, and the criteria of indicators in safety cases for disposal were introduced. According to different evaluation objects, complementary indicators are usually divided into safety indicators and performance indicators, and some organizations have developed the concept of safety function indicator as well. The corresponding criteria for comparison with the indicators are reference values, indicator criteria and safety function indicator criteria, respectively. If the disposal system is regarded as several compartments, the indicators could also be divided into 3 main groups including ‘content and concentration’ related, ‘flux’ related and ‘status of barriers’ related. The suggestions for the disposal of radioactive waste in our country are to develop the safety cases as soon as possible, to establish a complete indicator system, to select appropriate indicators for assessment, and to determine relevant criteria based on the characteristics of radioactive waste disposal sites in China, in order to implement the optimization of safety and protection.
    Discussion on the safety case and related issues for the disposal of radioactive waste
    QIU Guohua, LI Jinfeng, LIU Senlin, FAN Zhong, CHEN Yunli
    RADIATION PROTECTION. 2018, 38(2):  95-100. 
    Abstract ( 95 )   PDF (1059KB) ( 180 )  
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    Based on the IAEA safety standards series No. SSG-23, the safety case for the disposal of radioactive waste and its application in the UK, France, the USA, Finland, Switzerland and Sweden were briefly introduced in this article. Combining with the management status quo of the disposal of radioactive waste in China, the main issues in current environmental impact assessment and safety analysis of disposal sites were discussed. In order to promote all-round development of safety case in China, it was suggested that relevant standards should be developed as soon as possible, safety case should be required as a condition to get the license for radioactive waste disposal, and research emphasis should be put on scenario development, long-term variations, robustness, uncertainty and management system.
    Progress on the safety case for geological disposal of high level radioactive waste
    LING Hui, WANG Ju, CHEN Weiming, CHEN Liang
    RADIATION PROTECTION. 2018, 38(2):  101-109. 
    Abstract ( 119 )   PDF (1524KB) ( 269 )  
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    Safety case for high level radioactive waste geological disposal is a systematic analysis of the long-term safety of the repository. The concept of safety case and its development in the past 20 years are discussed. The importance in the stages of planning, site selection, design, construction, operation, closure and post-closure of high level radioactive waste disposal facility are emphasized. Based on the technical documents of NEA and IAEA, the background, objectives, safety policy, foundation, safety assessment and system integration of the safety case are described. Twelve key points of management and technology in its application are given. The research work in Finland, Sweden, the United States and France are reviewed. Finally, suggestions on development and application of safety case in China are given.
    The experimental study on the preparation of quasi-uranium ore material and the measurement of radon diffusion coefficient
    JIANG Fuliang, LI Ming, LI Xiangyang, HONG Changshou, ZHANG Shuai, YANG Wenchao, WANG Xiaoli
    RADIATION PROTECTION. 2018, 38(2):  110-118. 
    Abstract ( 75 )   PDF (2092KB) ( 138 )  
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    Diffusion process is the main factor that leads to the migration and exhalation of radon in uranium ore. Taking into account the fact that the hazard exists in underground uranium mine and field sampling are rather difficult, it is not conducive to do the laboratory test. In order to solve the above problems, based on the similarity theory, a kind of typical granite was taken as the prototypical model, and the quartz sand, uranium tailings, cement, fine iron powder and silicon powder as the raw materials, three cylindrical uranium-like rock samples with different material ratios were prepared, and the physical and mechanical parameters were then measured. In addition, these samples were sealed in different ways and the corresponding cumulative radon concentrations were measured by closed chamber method. The formula for calculating the diffusion performance of radon is deduced, and the radon diffusion length and diffusion coefficient of the prototype and the samples were calculated. The results showed that the mean similarity ratios of the particle density, compressive strength, tensile strength, cohesion and internal friction angle of the granite rock and quasi-uranium ore were respectively 1.09 ∶1, 3.93 ∶1, 4.28 ∶1, 3.47 ∶1 and 1.00 ∶1, the diffusion coefficient of granite prototype was 0.146×10-6 m2·s-1, the diffusion coefficient of quasi-uranium ore was between 0.114×10-6 m2·s-1 and 0.594×10-6 m2·s-1, and the similarity ratio was between 0.25∶1 and 1.28∶1. Therefore, the third sample of similar materials to some extent can be used to simulate the granite-type uranium rock and can meet the needs of laboratory experiments.
    Analysis and measurement of 239+240Pu in environmental air
    LIANG Yong, YANG Xiuyu, WANG Zhijun
    RADIATION PROTECTION. 2018, 38(2):  119-122. 
    Abstract ( 74 )   PDF (1099KB) ( 135 )  
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    A measurement method for 239+240Pu in environmental air was established. In this method, about 5 000 to 10 000 m3 air is filtered with NF-2 filter cloth to obtain aerosol sample, the sample is ashed with a dry method, plutonium is leached with hot nitric acid and converted to tetravalent state with Fe(NH2SO3)2 and NaNO2, the tetravalent plutonium is separated and purified with tri-n-octylamine and polytrifluorochloroethylene, desorbed with 0.025 mol/L oxalic acid and 0.15 mol/L nitric acid. Finally, plutonium is electrodeposited on a stainless plate and measured by an alpha spectrometer. Key conditions and parameters of the measurement method were optimized by experiments as the following: 4 mm of the distance between two poles, 2.0 of pH, 6 cm of the height for the extraction/separation column, 2.0 mL/min of the flow rate of solution, 15 min of the oxidation-reduction time. The radiochemical recovery of plutonium was 52.5% to 82.5% with an average value of 68.3%. The minimum detectable amount was 1.31×10-7 Bq/m3 when aerosol sample volume was 10 000 m3. It is concluded that this method can be used to measure 239+240Pu of environmental aerosol samples. The concentrations of 239+240Pu in aersol samples taken from a northwestern district of China were measured with this method and an average value of 3.25×10-6 Bq/m3 was obtained.
    Study on release path of airborne radioactive substances in the China Experimental Fast Reactor
    YANG Jiayin, WANG Yong
    RADIATION PROTECTION. 2018, 38(2):  123-131. 
    Abstract ( 118 )   PDF (2232KB) ( 267 )  
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    The China Experimental Fast Reactor(CEFR) is the first sodium cold fast neutron reactor in China, which has achieved full-power operation. The source, migration in the reactor core and release pathways of the airborne radioactive materials in the experimental fast reactor of China were analyzed. The pathways discharged to the environment in normal and accident conditions were identified in order to assess the radioactive effects of the CEFR on the environment, and to establish and maintain the protection against radioactive hazards.
    Survey of radioactivity level of uranium in plants within uranium tailings waste backfilling area
    JIANG Xiaoyan, YAN Dong, HE Yingxue, ZHAO Xianzhe, DING Kuke
    RADIATION PROTECTION. 2018, 38(2):  132-136. 
    Abstract ( 82 )   PDF (1611KB) ( 102 )  
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    The study was to understand the enrichment of uranium in the plants within the uranium tailings backfill area in the north of China. This study also provided a theoretical basis for the further study of the feasibility of phytoremediation technology in uranium mining area. Uranium content in plant and soil were measured with inductively coupled plasma mass spectrometry after collecting plant and soil samples in leaching location of mining area and in mine tailings backfill area. This study aimed at evaluation of plants tolerance and uranium enrichment ability, screening of plants, and further exploration for the use of phytoremediation technology. The uranium content in the underground part of the plants was found to be higher than aboveground part. Uranium was mainly concentrated in the roots, and the uranium contents in different parts of the plant from high to low were roots, leaves, stems, flowers and fruits. The uranium radioactivity in the root of Artemisia sieversiana was 64.26 Bq/kg in the leaching location. In the mine tailings backfill area, the uranium content in the same part was relatively low as 0.86 Bq/kg. The uranium content in the plant from the tailings backfill area was extremely low, and far less than that from the leaching area, and generally the uranium content in roots was greater than that in shoots. Uranium was mainly enriched in plant roots, and the contents in plant different parts from high to low were root, leaf, stem. Deep buried backfill of uranium tailing is proven to be feasible.
    Comparison of several radioactive methyl iodide methods for iodine removal efficiency test of nuclear ventilation systems
    GAO Linfeng, YAO Yanyan, WANG Lei, ZHANG Yuan, YU Jie
    RADIATION PROTECTION. 2018, 38(2):  137-141. 
    Abstract ( 99 )   PDF (1551KB) ( 120 )  
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    Application of three methods for performance tests of iodine adsorbers and iodine removal efficiency test of nuclear ventilation systems was studied. Generation rates of methyl iodide, toxicity of reagents and residuals, reliability of test, and stability of equipment were evaluated. Results of this study indicated that the application of dimethyl sulfate method was limited due to its toxicity, trimethyl chlorosilane trimethyl phosphonoacetate method could satisfy the regulatory requirements of nuclear power plants but need to be improved on its corrosion to equipment; while isotope exchange method could be advantageous due to its low toxicity, high generation rate of radioactive methyl iodide, simple and stable operation, and low risk for the application in nuclear power plants.
    Experimental study on decontamination of surface radioactivity by dry-ice blasting
    LI Ye, TAN Zhaoyi, ZHANG Dong, LU Chuanxia, ZHANG Penghao, YANG Yang
    RADIATION PROTECTION. 2018, 38(2):  142-147. 
    Abstract ( 185 )   PDF (2321KB) ( 195 )  
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    A dry ice decontamination method and its equipment, with high decontamination efficiency, slight damage on matrices, and minimum of secondary waste, were developed to effectively decontaminate radioactive contaminations on surfaces of assemblies to be repeatedly utilized. An integrated system equipment of dry ice decontamination and gas cleaning was assembled, utilizing a dry ice cleaning technology for the decontamination of surface contamination and a closed loop design from blasting decontamination to collection of secondary wastes. Experiments of decontamination conditions were carried out using this equipment, and decontamination parameters of high efficiency and non-damage were obtained. The advantages of high decontamination efficiency, effect of aerosol cleaning, minimization of secondary waste were validated with the application of this new decontamination technology of dry ice blasting and offgas cleaning to decontaminate metal assemblies of in-place repeated utilization.
    Performance research and selection of activated carbons used in delay bed of nuclear power plants
    LI Yongguo, WANG Longjiang, SHI Yingxia, WANG Kunjun, LV Yang, ZHANG Jirong, QIU Dangui, HIU Jianrong, LIU Qun, XU Yangyang
    RADIATION PROTECTION. 2018, 38(2):  148-154. 
    Abstract ( 80 )   PDF (2620KB) ( 117 )  
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    A delay bed system for evaluating the performances of various kinds of activated carbons is established, and the retaining performances for radioactive krypton and xenon with different kinds of activated carbons were conducted. The effects of parameters, including system pressure, temperature of carrier gas, gas flow rate, and radiation intensity, etc., on retaining performances for krypton and xenon with activated carbons were carried out. It is known from experimental results that dynamic adsorption efficiency becomes bigger when pressure becomes higher and temperature becomes lower, and the affections of gas flow rate and radiation intensity are slight and neglected. The selected kinds of activated carbons all have satisfied physical properties and retaining capability for radioactive noble gas. The selected kinds of activated carbons satisfy the design requirements of radioactive gaseous treatment system and can be used in nuclear power plants.
    Status and discussion of standards for water filter elements used in nuclear power plants
    QIAO Taifei, KONG Haixia, SHI Yingxia, HOU Jianrong, WANG Jia, HAN Lihong
    RADIATION PROTECTION. 2018, 38(2):  155-160. 
    Abstract ( 80 )   PDF (1737KB) ( 239 )  
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    Current status of the technical standards and the performance testing standards for water filter elements used in nuclear power plants was introduced, and the trend for the developments of these standards was analyzed. Some imperative problems to be solved in establishing the performance testing standards for water filter elements were discussed to support the complement of the technical standards and performance testing standards for water filter elements used in nuclear power plants.
    Study on minimization strategy of radioactive waste of HTR-PM nuclear power plants
    JIANG Ziying, ZHANG Yanqi, WEN Baoyin, LIAO Haitao, LI Hong
    RADIATION PROTECTION. 2018, 38(2):  161-170. 
    Abstract ( 103 )   PDF (3020KB) ( 168 )  
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    Radioactive waste minimization is one of the basic principles of radioactive waste management. Study on radioactive waste minimization strategy of high temperature gas-cooled reactor of pebble-bed (HTR-PM) nuclear power plants has great significance for design optimization, operation activities, radioactive waste management, and development of high temperature gas-cooled reactor industry. The HTR-PM techniques and radioactive waste characteristics were analyzed on the basis of the data of operation history and radioactive wastes of HTR-PM in the world, radioactive waste management experiences and related research progresses were summarized, and finally some suggestions on radioactive waste minimization strategies of HTR-PM were proposed.
    Research progress of TGF-β1 on radiation-induced pulmonary fibrosis
    CHEN Zhiyuan, DONG Zhuo, WEI Wei, LU Yahui, WANG Rui, YUAN Mingcheng, JIN Shunzi
    RADIATION PROTECTION. 2018, 38(2):  171-176. 
    Abstract ( 160 )   PDF (1572KB) ( 198 )  
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    Transforming growth factor-β1 (TGF-β1) mediates complex fibrotic signaling pathways during the development of pulmonary fibrosis. Especially in the repair of lung tissue injury, TGF-β1, as an important cell growth factor plays an important role, can activate fibroblasts and promote matrix synthesis, resulting in a large number of collagen. Radiation induced lung injury is a common complication in radiotherapy of lung disease. Early manifestations are radioactive pneumonia and advanced manifestations are radioactive pulmonary fibrosis. Understanding of the molecular mechanism of TGF-β1 in the pathogenesis and progression of pulmonary fibrosis is of great significance to prevent, treat pulmonary fibrosis and reduce the incidence of complications. In this paper, the molecular mechanism of TGF-β1 in the role of radiation pulmonary fibrosis and treatment progress were reviewed.