RADIATION PROTECTION

Development status on post-accident management strategy for nuclear and radiological accident

YANG Duanjie, LI Bing, CUI Hao, HOU Jie

RADIATION PROTECTION. 2020, 40(3): 177-180.

Abstract ( 316 )

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International development status and related requirements regarding post-accident management strategies for nuclear and radiological accident were briefly introduced. Based on current practical situations in China, some suggestions were set forth in establishing and improving the system of post-accident management strategies, so as to enhance the capacity of overall emergency managemen.

Thoughts on the prevention and regulation on radioactive occupational hazards in Chinese non-uranium mines

GU Xiaona, LIU Zhanqi, ZHAN Jingming, LIU Hong

RADIATION PROTECTION. 2020, 40(3): 181-185.

Abstract ( 198 )

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Non-uranium mines refer to mines whose main purpose is not to produce uranium. In China,the level of radon pollution in some non-uranium mines is high. And the annual effective dose caused by radon is close to or exceeds the annual effective dose limit for occupational radiation worker. However, there is still no specific regulations on the prevention of radioactive occupational hazards in non-uranium mines. In this paper, some key problems such as the prevention and control emphasis of radioactive occupational hazards in non-uranium mines, the determination of dose constraint values of radon in the workplace of non-uranium mines is discussed, and the corresponding countermeasures and suggestions are proposed.

Study on on-site calibration method of stationary neutron dosimeter

LV Ning, GUO Huiping, SHANG Aiguo, ZHOU Cheng, LV Jinxu, ZHAO Kuo, WEI Zhihao, LV Wenhui, LIU Yang, LI Daji, WANG Kai

RADIATION PROTECTION. 2020, 40(3): 186-192.

Abstract ( 188 )

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In this paper, a nuclear facility on-site calibration system consisting of a small-scale controllable neutron source and a neutron dose reference instrument is used to obtain the calibration coefficient through the ratio of the response of the instrument to be calibrated and the reference instrument to the neutron emission of the neutron tube in a symmetrical position. In order to complete the transfer of the instrument’s ambient dose equivalent calibration coefficient from the reference radiation field of the National Standards Metrology and Calibration Center to the nuclear facility site, the calibration coefficient must be energy corrected. Am-Be neutron source was used to simulate the radiation field inside the nuclear facility, the on-site calibration experiments of neutron dose instruments were performed, and compared with the measurement results of the calibrated multi-sphere neutron spectrometer. The results have shown that: if the measurement results of the instrument to be calibrated were calibrated using an uncorrected calibration coefficient, the relative deviation of the ambient dose equivalent rate was 17.0%; while if the measurement results of the instrument to be calibrated were calibrated using the corrected calibration coefficient, the relative deviation of the ambient dose equivalent rate would be -2.4%.

A compact LaBr₃:Ce gamma spectrometer based on SiPM with high energy resolution

SHI Boxuan, LIU Liye, CAO Qinjian, XIA Sanqiang, WANG Xiaolong

RADIATION PROTECTION. 2020, 40(3): 193-197.

Abstract ( 202 )

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The PMT-based LaBr₃:Ce gamma spectrometer has higher energy resolution than NaI gamma spectrometer, but it has the disadvantages such as large volume, sensitive to magnetic field and high voltage demand. Silicon photomultiplier tube (SiPM) has similar gain and efficiency as PMT, while offering excellent characteristics such as high timing resolution, high magnetic field resistance, low bias and compact size. In this paper, the LaBr₃:Ce crystal is coupled with the SiPM array, and the compact LaBr₃:Ce γ spectrometer based on SiPM is designed and developed to improve the impact of the shortcomings of SiPM on the performance of gamma spectrometer by reducing noise, optimizing the operating voltage.The noise of working voltage will lead to the deterioration of energy resolution. By designing the CLC-type π filter with passive filter circuit, the high frequency ripple can be filtered by using its different characteristics of DC/AC impedance and the signal-to-noise ratio of working voltage can be increased from 62.6 dB to 74.64 dB before the noise reduction. The minimum energy resolution corresponds to the optimum operating voltage representing a compromise between dark noise, crosstalk, photodetection efficiency, and SiPM gain. The energy resolution at different working voltages is given by experiment, and the optimal working voltage is determined to be 54.8 V. The energy resolution at this voltage is 3.06% (@662 keV), the result of which is very close to 2.89% measured by photomultiplier tube (PMT).

Calculation of radioactive effluents source terms from third generation NPP and the environmental impact optimization under the condition of inland plant site

CHEN Cheng, ZHANG Libo, ZHANG Junnan, WANG Xiaoliang

RADIATION PROTECTION. 2020, 40(3): 198-203.

Abstract ( 201 )

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Inland nuclear power is an important choice for the future development of nuclear power in China. Compared with the coastal plant site, the environmental conditions of inland plant site have their own characteristics. In this paper the radioactive effluents source terms calculation and results from third generation NPP such as HPR1000 and AP1000 are introduced, and analysis process of environmental impact of radioactive effluents is described. The differences of atmospheric diffusion conditions and receiving water conditions between inland and coastal nuclear power plants, as well as the requirements of regulations and national standards, are compared and analyzed. Based on the ALARA principle, the methods of reducing the total amount of radioactive effluents and its environmental impact, and the method to adapt to the site lack of receiving water are proposed.

Study on indoor radon concentration level and pollution of an office space in Chengdu

XU Lipeng, GE Liangquan, WANG Meng, WANG Liang, LI Bin, YU Qiang, WANG Qian, GUO Xuying, GU Yi

RADIATION PROTECTION. 2020, 40(3): 204-211.

Abstract ( 228 )

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The solid state nuclear track method and the instantaneous method were used to investigate indoor radon concentrations of an office space in Cheng Du. The results show that the range of indoor cumulative radon concentrations is 10.82-102.50 Bq/m³, the arithmetic mean is (36.56±17.38) Bq/m³, which is lower than the national and world averages. The investigation proved that new decoration materials such as glass walls and rubber ground can effectively reduce indoor radon, and ventilation can also effectively reduce indoor radon concentration. The studies found that high concentrations of PM_2.5 and PM10 can affect office indoor and outdoor radon concentration levels. By finding contamination and dealing with the abnormal radon concentration in the low background laboratory, the following suggestions are given: Avoid samples with high concentration of radio-nuclides temporarily stored near the test equipment; In order to reduce the interference of radon and its daughters on measurement and improve the accuracy of analysis results, it is suggested to upgrade and transform the fresh air system of low-background laboratory.

A brief analysis about management and evaluation of personnel body surface contamination at nuclear power plant

ZHANG Zhengzheng, YANG Junwu, GU Hairong, SU Liangliang

RADIATION PROTECTION. 2020, 40(3): 212-216.

Abstract ( 158 )

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This paper briefly describes the method of estimating skin dose by skin contamination level. Taking surface pollution measuring instrument 6150AD5+6150AD17 as an example, the conversion relation between the monitoring value and contamination level is derived. According to the management requirements of body surface contamination in China and internationally, the definition, classification method and response strategy of the human body surface contamination event based on the monitoring value of 6150AD17 are given. Finally, some suggestions on evaluation index of surface pollution management are given.

Feasibility analysis on external sampling technologies of iodine adsorbers

LIANG Fei, LV Yang, ZHANG Yuan, WANG Zhen, WU Bo, ZHANG Xueping, ZHANG Zhaochen, GAO Linfeng, QIU Dangui, HOU Jianrong

RADIATION PROTECTION. 2020, 40(3): 217-222.

Abstract ( 152 )

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Sampling technologies of iodine adsorbers in different types of nuclear power plants are investigated and their different influence factors on sample representativeness of the entire adsorbers are analyzed. Results of performance tests under different conditions and adsorbent bed-depths showed that the bed depth and pressure drop through a sampler section are the same as through the main adsorber bank for the sample to be representative, which may be helpful to the feasibility analysis of the external sampling device of iodine adsorbers.

Decontamination practice of radioactive contaminated hydraulic torsion wrenches in NPP

LI Yuxin, JIA Jianzhao

RADIATION PROTECTION. 2020, 40(3): 223-230.

Abstract ( 166 )

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large number of radioactive contaminated hydraulic torque wrenches are resulted from maintenance of radioactive contaminated equipment and sites during normal operation and outage of nuclear power plants. And the contaminated hydraulic torque wrenches are difficult to be decontaminated because of their complex structure with many components and hot spots deposited in dead corners. Therefore they have to be treated as radioactive waste in many nuclear power plants. In order to solve the problems regarding cost control, minimization of radioactive waste, and radiation protection optimization caused by these contaminated hydraulic torque wrenches, some deep decontamination tests through chemical decontamination, mechanical decontamination, foam decontamination, ultrasonic decontamination and other combined processes were carried out. Result shows several hydraulic torque wrenches are finally cleaned and qualified with decontamination criteria after four stages of deep decontamination with a decontamination factor of higher than 1,000, which proves the deep decontamination method for radioactive contaminated hydraulic torque wrenches is feasible, practical and effective.

Three-dimensional numerical analysis of the interaction between fracture water flow, heat transfer and distance between disposal pits in the near field of high-level radioactive waste repository

GAO Junyi

RADIATION PROTECTION. 2020, 40(3): 231-238.

Abstract ( 114 )

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In order to study the interaction mechanism between fracture water flow, heat transfer and distance between disposal pits in the near field of high-level radioactive waste repository, 3DEC software is used to calculate the influence of the interaction of fracture water flow, heat transfer and distance between disposal pits on the near-field temperature distribution of the disposal repository. Results show that: (1) Under the same disposal pit spacing, the flowing fracture water changes the temperature field near the disposal pit, decreases the rock mass temperature, and obviously shortens the time required for the model to reach steady state; (2) The larger the distance between the disposal pits, the weaker the temperature superposition effect. The lower the near-field temperature of the disposal repository, the lower the temperature of bentonite of waste tank surface. The lower the water temperature at the outlet of the fracture, the shorter the time required for the model to reach a steady state; (3) The temperature in downstream area of near-field fracture water flow is significantly higher than that in upstream area of fracture water flow in the disposal reservoir due to joint heat transfer between horizontal and vertical fracture water flows; (4) The water temperature of horizontal fracture water outlet is higher than that of the vertical fracture water outlet when the spacing of the disposal pit is 6 m and 8 m, but the water temperature of the horizontal fracture water outlet is lower than that of the vertical fracture water outlet when the spacing of the disposal pit is 10 m.

Discussion on the setting of licensed position for the main process operator in spent fuel reprocessing facility

LYU Dan, YANG Xiaowei, LIU Yuntao, ZHANG Yu, ZHAO Shangui, XU Chunyan

RADIATION PROTECTION. 2020, 40(3): 239-244.

Abstract ( 186 )

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The main process operators at spent fuel reprocessing facilities are important professional technical talent concerning nuclear and radiation safety of the facility. It is necessary to implement license management for the operators in the safety-critical operation positions. In the four parts of the main process in the spent fuel reprocessing facility, which are divided as front-end, Uranium and Plutonium separation, Uranium-end (including Uranium refining) and Plutonium-end (including Plutonium refining). Analysis and comparison were carried out on the safety functions they performed, the credible potential accidents they might face, and the realistic accidents caused by human error in history as well. The study found that, the safety process of prevention of criticality, radioactive material containment and external radiation protection was carried out in the four processes of front-end, Uranium and Plutonium separation, Uranium-end (including Uranium refining) and Plutonium-end (including Plutonium refining); the number of credible potential accidents in the four processes are all about 20; the realistic accidents caused by human error in history are more concentrated in the three processes such as Uranium and Plutonium separation, Uranium-end (including Uranium refining) and Plutonium-end (including Plutonium refining). The study showes that, it is necessary to set up licensed positions and carry out operator personnel qualification management in the four parts of the main process in the spent fuel reprocessing facility.

Preliminary study on identification method for safety key positions at nuclear fuel cycle facilities

HAN Guosheng, LIU Caixia, XU Jian, ZHANG Liang, HUANG Qingyong, LEI Qifeng, WANG Yifeng

RADIATION PROTECTION. 2020, 40(3): 245-249.

Abstract ( 176 )

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The identification method for safety key positions at nuclear fuel cycle facilities was established in this work, based on the characteristics of post responsibility, safety risk and professional skills. The definition, identification indicator system, identification principle, identification and evaluation process as well as case study of certain spent fuel reprocessing plant were given.

Research progress of mesenchymal stem cell for treatment of radiation injuries

WANG Li, MA Dexun, Zhang Rui, ZHANG Chao, GAO Rui, LIU Shufeng

RADIATION PROTECTION. 2020, 40(3): 250-255.

Abstract ( 190 )

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The probability of radiation incidences is increasing with the widespread use of nuclear energy in the field of military and civilian. Radiation exposures result in a variety of tissue injuries, including hematopoietic and immune system, gastrointestinal tract, lung and skin etc. Current treatment strategies had a dissatisfactory efficacy on victims who received lethal radiation dosis. Mesenchymal stem cells (MSCs) are low immunogenicity and suit for allogeneic application. MSCs have the capacity to differentiate a variety of cells and unique immunomodulatory effect and hematopoietic supporting capacity. MSCs can enhance hematopoietic reconstitution and tissue repair after irradiation through their differentiation capacity and paracrine effects. Herein, the recent research progress about the effect of MSCs on radiation injuries is systematically reviewed.

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