RADIATION PROTECTION

Effects of material structural gaps on neutron shielding using SuperMC

MENG Xianfang, ZHANG Long, SUN Chao, WANG Shijun, CAO Ke, MA Huiling, QIN Peizhong

RADIATION PROTECTION. 2018, 38(4): 265-269.

Abstract ( 100 )

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Neutron attenuation ratios of four different structural gaps on two kinds of spectrum neutrons were calculated using SuperMC (Super Monte Carlo Program for Nuclear and Radiation Simulation). The structural gaps were made of boron polyethylene (B-PE) materials. In order to study the effect of different gaps on neutron shielding performance, they were compared with seamless materials and the relative reductions of neutron attenuation ratios were obtained. Some simulation results were verified by the experiments under the same conditions. The results showed that, for the B-PE materials with a thickness of 6 cm, the relative reduction of neutron attenuation ratio is 1/8 on fast neurons by comparing of oblique gap with straight gap. That is 1/3 on slowing down neutrons. Oblique gap is proved to have the least negative effect on neutron shielding.

Measurement of uranium isotopes in environmental samples by ICP-MS

LI Sixuan, HUANG Wenna, WANG Zhongtang, GUO Qiuju

RADIATION PROTECTION. 2018, 38(4): 270-274.

Abstract ( 142 )

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A new method for simultaneous and fast determination of uranium isotopes (²³⁴U, ²³⁵U, and ²³⁸U) in environmental samples by ICP-MS has been developed. In this research, we employed an extraction chromatography for separation and purification of uranium from water, soil, and sediment samples. Low detection limits of this method are ultimately achieved. They are 0.7 mBq/g for ²³⁴U, 0.002 mBq/g for ²³⁵U, and 0.04 mBq/g for ²³⁸U in soil and sediment samples. In water samples they are 0.000 1 Bq/L, 6×10^-7 Bq/L, and 1×10^-5 Bq/L respectively. This method is validated by analyzing seawater reference material IAEA-443, soil reference material IAEA-447, and sediment reference material NIST-4357 with average recovery ratios of 84.2%, 93.4%, and 90.6% respectively. All results obtained correspond well to those certified values and corroborate the validity and veracity of this method.

Measurement of radon concentration in shallow soil in Beijing area

YANG Zhijie, ZHAO Rong, WANG Nanping

RADIATION PROTECTION. 2018, 38(4): 275-280.

Abstract ( 114 )

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In order to study the relationship between the radon concentration and the depth of shallow soil in Beijing area, field survey of soil using RAD7 electronic radon monitor has been performed along with collection of soil samples. The survey of 9 sample sites was carried out in Tongzhou Distirct, Fengtai District, Mentougou district and Yanqing County, respectively. The soil radon concentrations at 20 cm, 40 cm, 60 cm, 80 cm and 100 cm depth were measured and the radium specific activities of the collected samples were analyzed with indoor HPGe γ spectrometer. The results showed that the concentration of soil radon increased with the increase of soil depth in shallow soil, and there was a positive correlation between soil radon concentration and specific activity of radium in soil samples. Compared with the radon concentration in the sandy soil , the concentration of radon in the clayey soil is higher.

Research on the method of concentration field measurement andatmospheric diffusion simulation

WU Haokun, LI Yunpeng, ZHANG Junfang, YAO Rentai

RADIATION PROTECTION. 2018, 38(4): 281-286.

Abstract ( 83 )

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There must be many assumptions and constraints to physical simulation. Water can partly replace air medium for physical simulation of atmospheric diffusion as a fluid medium and can be complementary to environmental wind tunnel experiments and other simulation tools. The physical simulation method of towing tank is discussed in this paper. A Planar Laser Induced Fluorescence (PLIF) technology was used to establish a set of methods for concentration field measurement suitable for atmospheric diffusion towed flume, which was preliminarily applied in pollution diffusion research near simple standards bodies. Results showed that some cases of atmospheric diffusion could be simulated, and different atmospheric conditions affecting pollutant concentration distribution could be derived using this method.

Unusual low radiation area on the surface of the earth: coral reefs

LIN Wuhui, YU Kefu, WANG Yinghui, LIU Xinming, WANG Jianjun, NING Qiuyun, LI Yinghua

RADIATION PROTECTION. 2018, 38(4): 287-291.

Abstract ( 96 )

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Radioactivity levels are rarely investigated in coral reefs compared to the land. In this study, the average radioactivity levels of ²³⁸U, ⁴⁰K, ²²⁸Ra and ²²⁶Ra were measured by High Purified Germanium (HPGe) γ spectrometry and found to be 28.96 Bq/kg, 24.36 Bq/kg, 5.08 Bq/kg, 3.34 Bq/kg respectively in marine sediments collected from coral reefs of the South China Sea (SCS).The environmental radiation quality was assessed by several indexes which was found to be significantly lower than the international recommended values. A comparison with marine sediments from other sea areas of China, the average of China, and the world average indicated that radium equivalent activity of coral reefs was only ~10% and ~1‰ of the world average and the high background radiation area (HBRA), respectively. Coral reefs have a unique feature of extremely low radioactivity in the surface of the earth.

Radionuclide transport and radiation protection in production process ofZrOCl₂ from zircon sand in a factory

GUO Qingli, WANG Yan, LI Xianjie

RADIATION PROTECTION. 2018, 38(4): 293-299.

Abstract ( 83 )

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Radionuclide transport and radiation protection are discussed based on analysis of some natural radionuclides in feedstocks, products, intermediates, and wastes in the production process of zirconium oxychloride (ZrOCl₂) from zircon sand in a factory. The results showed that U, Th, and ²²⁶Ra were enriched in the third waste acid with concentrations of 1.52 g/L, 1.31 g/L, and 801 Bq/L, respectively. 86% of U and 99% of Th went into final residues of waste water treatment, 14% of U was discharged into treated waste water. Natural radionuclides in ZrOCl₂ are too little and no attention is needed. The residues from the ZrOCl₂ production process need to be treated as radioactive wastes. The additional external irradiation doses of workers are calculated as a maximum of 1.61 mSv/a. The relavant measures for radiation protection are suggested.

Assessment of radiation dose to inhabitants from coal ashin main wall material in China

SONG Weijie, CHEN Ling, PAN Ziqiang, GUO Jinsen, LIU Zhe

RADIATION PROTECTION. 2018, 38(4): 300-307.

Abstract ( 108 )

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Additional radiation dose to inhabitants living in buildings constructed with wall material containing coal ash were evaluated through the investigations on electricity generation of coal-fired power plants (CFPs), activity concentration of natural γ nuclides in coal ash, comprehensive utilization of coal ash in wall materials in China and the indoor radiation exposure scenarios during 1992—2010. The results showed that: the radiation dose for inhabitants living in these buildings increased with the addition of coal ash in main wall material, which was consistent with the reported data. In China, the total additional annual effective individual dose from wall material containing coal ash was 0.01-0.30 mSv/a higher than that from red bricks, with an average of 0.22 mSv/a; and the internal dose approached to 82%. The additional normalized collective dose during 1992—2010 was approximately (1.92×10³)-(5.85×10³) man·Sv/GWa. It was also found that the average contribution to the increase of indoor radon concentration from use of main wall material containing coal ash approached to 28%, with a range of 7%-38%. The results obtained in this study provided essential basic data for the utilization policy of coal ash and environmental radiological risk analysis for CFPs.

Study on influence factors and characteristics of continuousmonitoring data of environmental γ dose rate

LUO Dunye, SHA Xiangdong, SHANGGUAN Zhihong, LIN Minggui, HUANG Yanjun, PENG Kai

RADIATION PROTECTION. 2018, 38(4): 308-318.

Abstract ( 138 )

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Continuous monitoring of γ dose rate is the main item of regular monitoring and supervision monitoring of nuclear power plants. Analysis of influence factors for continuous monitoring data of γ dose rate is important to identify abnormal discharge of nuclear power plants and establish emergency monitoring background. In this paper, various influence factors, including cosmic ray response, meteorological parameters, and discharge from nuclear power plants were studied on the basis of the continuous monitoring hourly data of γ dose rate from a supervision monitoring system of Ningde Nuclear Power Plant in 2016 and the related characteristics were summarized. The study results show that γ radiation mainly comes from natural radioactive isotopes and cosmic rays. The variation of meteorological parameters is the main influence factor on variation of γ dose rate. From the rapid Fourier analysis ( FFT) and the analysis of meteorological parameter relativity, it shows that there is an obvious date-period variation in the data of continuous monitoring of γ dose rate. The radioactivity released from nuclear accidents may also affect the monitoring result of γ dose rate.

Multi-attribute analysis theory and its application in optimization of liquideffluent release from Fang Jiashan nuclear power project

ZHANG Jing, ZHAI Liang, ZHU Yuelong

RADIATION PROTECTION. 2018, 38(4): 319-325.

Abstract ( 82 )

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According to the requirements of national regulations and National Nuclear Safety Agency, radioactive effluent release amount should be approved regularly. Multi-attribute analysis theory and its application in the optimization of the effluent release amount of Fang Jiashan nuclear power project is described. Through comprehensive analysis on individual dose, collective effective dose, worker dose from TEU system and radioactive waste disposal cost and descendant effect, the optimized amount of liquid effluent release of Fang Jiashan nuclear power project is given.

Experimental study on hot-melt pressure sensitive coil materialfor decontaminating radioactive dust

WANG Jing, WANG Jianhui, LI Jian, ZHENG Li, CAO Xingwei

RADIATION PROTECTION. 2018, 38(4): 326-330.

Abstract ( 84 )

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This study aims to develop a new method for quickly removing surface radioactive contamination with hot-melt pressure sensitive coil material. The hot-melt pressure sensitive coil was designed and prepared by screening hot-melt pressure sensitive adhesives and substrates. Simulated decontamination tests with the coil material were conducted to decontaminate dusts prepared with 100-mesh and 20-mesh standard sieves for simulating nuclear explosion fallout and radioactive contaminated particles, respectively. The single-time decontamination efficiencies for simulated fallout and contaminated particles are both above 80% at conditions of 25 kPa pressure and 140 ℃ temperature, a maximum single-time decontamination efficiency is 92.5%. These results validated its decontamination effect of the prepared hot-melt pressure sensitive coil material for removing surface nuclear explosion fallout and may provide useful information for its practical application.

Preliminary study on interaction of bentonite and water

LIU Wei, LIANG Dong, LI Honghui, JIA Meilan, ZHAO Shuaiwei, MAO Liang, YANG Zhontian

RADIATION PROTECTION. 2018, 38(4): 331-335.

Abstract ( 144 )

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In order to study the interaction influence of bentonite and water on safety of geological disposal for high-level radioactive waste, two bentonites of different montmorillonite contents were immersed in water for 3 000 hours. Test results showed that their swell indexes increased with the increase of montmorillonite content, and a linear relationship was observed between the biggest swell index and logarithm of montmorillonite content. After swelling reached equilibrium, the concentration of univalent cation was larger than the concentration of divalent cation in supernatant and it increased with the increase of montmorillonite content; and there was also a linear relationship between sodium concentration and logarithm of montmorillonite content in two bentonites. The amount of dried residue of the supernatant also increased with the increase of montmorillonite content, and the XRD test results indicated that montmorillonite was present in dried residue of liquid supernatant. These experimental results can be a basis for further studies on interaction of buffer material and groundwater in geological disposal.

Characterization practices and suggestions for low andintermediate level radioactive waste forms in China

XIANG Zhengzhi, GUO Xiliang, YAN Xiaojun, XU Chunyan, LI Xiaolong

RADIATION PROTECTION. 2018, 38(4): 337-343.

Abstract ( 107 )

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Practices and experiences of characterization for low and intermediate level radioactive waste forms are introduced. Insufficiencies in characterization techniques and requirements in China are analyzed, and some suggestions are provided in view of good practices and regulatory requirements of other countries.

Lessons learned from robots used in Fukushima nuclear accident

CHEN Faguo, YANG Mingming, HAN Yi, LI Guodong

RADIATION PROTECTION. 2018, 38(4): 344-351.

Abstract ( 262 )

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Up to now, more than 30 kinds of robots were used in Unit 1/2/3 of Fukushima Daiichi NPP for aerial survey of the reactor building exterior, decontamination of work area and walkway, investigation of water leakage from primary containment vessel, the reactor building interior and the primary containment vessel interior. Eight of these robots broke down during operation mainly because of radiation damage and blocking of obstacles. The good practice and lessons learned from the deployment of robots in Fukushima NPP are worth for reference in the R&D and practical application of nuclear robot. Nuclear robot should be paid more attention and be developed in serialarity. Except for the high radiation field above dozens of Gy/h, the space accessibility and control performance,not the radiation tolerance,are usually the decisive factors to the practical application of nuclear robot. When used in the radiation field below 10 Gy/h, cumulative dose management and exchange of core components are effective countermeasures to make up for the shortage of radiation tolerance design for general robots.

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