Table of Content

20 May 2023 Volume 43 Issue 3

  

Progress of research on electromagnetic radiation safety of implantable medical devices

HE Diwei, CHEN Zhiying, TANG Danfeng, ZHANG Ying

RADIATION PROTECTION. 2023, 43(3):  193-208. 

Abstract ( 72 )   PDF (15515KB) ( 49 )  

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Long-term or excessive exposure of the human body to electromagnetic radiation may cause some health effect. When medical devices are implanted into human body, the level of electromagnetic radiation exposed to human body will be increased. With the widespread application of implantable medical devices, the safety of electromagnetic radiation containing such devices cannot be ignored. Implantable medical devices often communicate with the outside world or have power supply wirelessly. On the one hand, its existence will change the electromagnetic field distribution of external radiation sources in hu-man tissues, which may increase the level of electromagnetic radiation; on the other hand, it is a radiation source itself and will generate electromagnetic radiation in human tissues. Many countries and international organizations use the specific absorption rate to measure the impact of electromagnetic radiation on the human body, and use it to formulate safety limits for electromag-netic radiation. This paper reviews domestic and foreign research on electromagnetic radiation safety in the communication and charging scenarios of implantable medical devices, and focuses on the electromagnetic field metrology methods, related models and influencing factors of electromagnetic radiation specific absorption rate research. Finally, the numerical calculation and ex-perimental measurement methods are discussed and compared, and the important factors affecting the specific absorption rate are analyzed, which will provide reference to the engineering design of parameters such as optimal operating frequency and power limit.

Research on the module structure design of simulation workplace neutron spectrum device based on DT neutron source

LI Hui, LI Deyuan, YAN Xuewen, ZHANG Pengpeng, CHEN Faguo, LI Hua

RADIATION PROTECTION. 2023, 43(3):  209-217. 

Abstract ( 74 )   PDF (7577KB) ( 43 )  

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Neutron dose is highly dependent on its energy. However, the energy spectrum of the calibration field is different from workplace, which could lead to a large deviation in the measurement of neutron dose at workplace. Using simulation workplace neutron spectrum for equipment calibration will improve the accuracy of neutron dose measurements. In this paper, the modular construction method of the simulated workplace neutron spectrum and the structural design method of the device were studied based on the DT neutron source, the simulated spectrum with the characteristics of workplace neutron spectrum at pressurized water reactors (PWR), and its fuel cycle. By analyzing the T(d, n)⁴He reaction emission neutron’s energy spectrum and angular distribution law, a point source with an average energy of 14.1 MeV Gaussian distribution and isotropic emission was used to approximate the DT neutron source. 14 alternative materials were selected according to the interaction cross-section of neutron and matter, the relative neutron fluence ratio and average neutron energy were analyzed. And the materials for constructing the simulation workplace neutron spectrum device were selected from the perspectives of neutron multiplication, energy attenuation, energy spectrum adjustment, and practicality. Two workplace neutron spectrum of the pump room and reactor hall were selected as target spectrum. Main moderation assembly, modulating layers and reflector assembly were designed. The simulated neutron spectrum and device structure for the two workplace target spectrum were constructed. The results show that the construction method of the simulated workplace neutron spectrum described in this paper is effective, and the modular design is highly expandable, which can be adapted to a variety of workplace target spectrum to construct the simulated spectrum.

Design and testing of source range detector for nuclear measurement system outside reactor core

XIAO Wei, HU Chan, QIU Shunli, ZHAI Chunrong, DONG Jincheng, GE Mengtuan, ZHOU Yulin, ZENG Le

RADIATION PROTECTION. 2023, 43(3):  218-224. 

Abstract ( 80 )   PDF (3718KB) ( 42 )  

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A boron lined proportional counter is used to design the source range measurement channel of the ex-core nuclear measurement system. A high sensitivity detector is developed and a set of source rang detection device is designed. The thermal neutron sensitivity on pile test methods are given. The sensitivity, discrimination threshold characteristics, high-voltage plateau characteristics, count rate linearity and measurement range of the detection device are tested and verified. The test results show that the detector has excellent radiation performance. The thermal neutron sensitivity can reach 22 s^-1/(cm^-2·s^-1), and the high-voltage plateau characteristic plateau length is 150 V, with plateau slope 28.3%/100 V. The pulse counting rate of the detector has a significant linear coincidence with the neutron fluence rate, and the upper limit of the neutron fluence measurement can reach 1×10⁵ cm^-2·s^-1, which meets the use requirements of the source range channel of the external nuclear measurement system. The source range detector can be widely used in nuclear power plant and marine external nuclear measurement and monitoring systems.

Research on temperature drift correction method of seawater radioactivity sensor

SHI Yan, ZHANG Yingying, WU Bingwei, FENG Xiandong, WANG Yifei, BI Haijie

RADIATION PROTECTION. 2023, 43(3):  225-234. 

Abstract ( 95 )   PDF (9407KB) ( 33 )  

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The seawater radioactivity sensor developed based on NaI(Tl) scintillation crystal detection method is the main technological means to carry out in situ automatic monitoring of marine radionuclides at home and abroad. Nevertheless, when the seawater radioactivity sensor is continuously operating at sea for a long time, the measured seawater gamma spectrum data will drift due to the influence of ambient temperature. In this paper, the seawater radioactivity sensor measurement experiment is carried out under the condition of environmental temperature gradient change, and the drift law of the gamma spectrum data calculated by the seawater radioactivity sensor which occurs with the environmental temperature change is analyzed. When the ambient temperature is lower than 15 ℃, channel address corresponding to the characteristic energy peak increases with the increase of temperature; on the contrary, when the ambient temperature is higher than 15 ℃, the channel address corresponding to the characteristic energy peak decreases with the increase of temperature. The gamma spectrum peak channel address shift can be expressed as a quadratic function of temperature, and further a correction method of gamma spectrum shift based on ambient temperature change is proposed. It is verified by laboratory experiments on air and water environment that the peak channel address drift of characteristic peak after air environment correction is not more than ±2 channels, and the peak channel address drift after water environment correction is not more than ±3 channels, which meets the requirements of temperature drift correction for continuous measurement of gamma spectrum by the sensor.

Study on monitoring method of automatic continuous sampling and analysis system for ultra-large flow aerosol

CAO Longsheng, LIAO Yuhang, LV Anbiao, ZHOU Ying, ZHOU Feng

RADIATION PROTECTION. 2023, 43(3):  235-242. 

Abstract ( 67 )   PDF (8502KB) ( 39 )  

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Due to different Placement decay time of aerosol samples, the detection limit of automatic continuous sampling and analysis system for ultra-large flow aerosol will be greatly affected. High detection limit may cause the fact that very low content of artificial radioactive substances in the air can not be detected. In order to develop an optimized and perfect monitoring method, this experiment studies natural radionuclides that mainly affect the background and their changes with the placement time, and further analyzes the changes of the detection limit of artificial radionuclides around nuclear facilities with sample placement time, by measuring the samples in different weather conditions for different placement time. The results show that for routine environmental monitoring, the samples on sunny day need to be placed for 2 days after collection; On rainy days, the collected samples shall be placed for 1 day before measurement; For emergency monitoring , direct measurement after sampling is required, the detection limit of sunny day samples are about 4-5 times of the minimum value and rainy day samples are about 2 times. It can be considered to measure the samples directly first and then conduct verification measurement after sufficient decay time.

Rapid determination of strontium-89 and strontium-90 in liquid effluent of nuclear power plant by liquid scintillation counting method

FANG Chunming, YANG Fan, GUO Xiaocui

RADIATION PROTECTION. 2023, 43(3):  243-248. 

Abstract ( 77 )   PDF (3317KB) ( 44 )  

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This paper described analysis and measurement method for strontium-89 and strontium-90 in liquid effluent of nuclear power plant. Strontium-89 and strontium-90 in liquid effluent are enriched by cation exchange resin, separated by strontium resin, and measured by low background scintillation spectrometer. The relevant measurement conditions are analyzed and studied. This method simplifies the treatment process of liquid effluent of nuclear power plant. The established method can detect multiple nuclides at the same time, and can fully meet the analysis requirements of strontium-89 and strontium-90 in liquid effluent of nuclear power plant.

An evaluation method of indoor radon exposure dose matrix caused by building materials

XU Pengcheng, ZENG Zhi, MA Hao, SUN Bowen, LI Junli

RADIATION PROTECTION. 2023, 43(3):  249-256. 

Abstract ( 72 )   PDF (926KB) ( 61 )  

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In order to make the evaluation of indoor radon exposure dose more systematic and universally applicable, an evaluation method of indoor radon exposure dose caused by building materials was established by using matrix. Based on indoor radon concentration model, personnel exposure dose estimation model and standards, four factors including radon exhalation rate of building materials, building structure size, indoor air exchange rate and personnel exposure time were combined in this method. The complex calculation under different conditions is converted into the matrices. Using this method, the radon exposure dose levels of indoor personnel under different air exchange rates and different exposure duration can be obtained. Taking a room with known size and known radon exhalation rate of building materials as an example, this method was used to analyze and evaluate the indoor radon exposure dose. The indoor radon exposure dose levels under different ventilation rates and exposure duration were quickly and simply obtained from reference table.

Calculation and regulation of radon and radon progeny concentration in uranium mine ventilation network

YE Yongjun, ZHANG Yingpeng, CHEN Daijia, ZHANG Xiaoyu

RADIATION PROTECTION. 2023, 43(3):  257-264. 

Abstract ( 54 )   PDF (3069KB) ( 30 )  

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The radiation dose received by workers in uranium mines mainly comes from radon and radon progeny. In order to reduce the radiation dose caused by radon in uranium mine, it is necessary to provide sufficient and reliable radon reduction air volume to the underground on the basis of ensuring the air quality. Therefore, according to the ventilation network calculation theory, radionuclide decay theory and turbulent mass transfer theory, the calculation model of radon and radon progeny concentration in ventilation network is established. Using MATLAB software, according to the proposed model, the radon and radon progeny concentration distribution in the specific branch of a hard rock uranium mine is calculated and analyzed. The results show that: 1) the solution model can analyze the radon and radon progeny concentration of single branch, multi branch and ventilation network with local radon source; 2) According to the protection requirements against radon and radon progeny, the branch with the concentration of radon and radon progeny exceeding the limit can be judged, and the optimal air volume of radon and radon progeny reduction as well as the wind pressure of fan operation can be calculated by air volume adjustment method when the corrected air volume is small.

Experimental analysis on energy characteristics of DC arc plasma torch

ZHANG Ziwei, ZHOU Dongsheng, LIU Chunyu, LU Jie, LIU Xiajie

RADIATION PROTECTION. 2023, 43(3):  265-270. 

Abstract ( 44 )   PDF (3533KB) ( 16 )  

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The energy characteristic data of self-stabilized DC arc plasma torch with air and nitrogen as working gas are obtained by experiment. The influence pattern and function relation between arc current, gas volume and arc voltage are concluded, and the variation characteristics of plasma jet power and specific enthalpy are analyzed. The results show that when the arc current is constant, the arc voltage and power increase with the increase of gas volume, while the specific enthalpy decreases with the increase of gas volume. When the gas volume is constant, the power and specific enthalpy increase with the increase of arc current, and the arc voltage decreases with the increase of arc current. By fitting the volt-ampere characteristic function, U_air=480(I²/G)^-0.08G^0.30 for air and U_N2=693(I²/G)^-0.09G^0.25 for nitrogen, the volt-ampere characteristic curves of the two will have the same general trend. Under the same arc current and gas volume, the arc voltage, power and specific enthalpy of nitrogen as the working gas are larger than that of air.

Effects of ionizing radiation on the development of cerebellum and prefrontal cortex in mice during neonatal period

WANG Yangyang, LIU Yuanduo, LIU Lian

RADIATION PROTECTION. 2023, 43(3):  271-279. 

Abstract ( 55 )   PDF (14831KB) ( 16 )  

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To investigate the effects of X-ray on the development of cerebellum and prefrontal cortex in mice during neonatal period, the mice in irradiation group were irradiated with whole-body X-ray dose of 2 Gy (2 Gy/min) at the postanal day 3(PD 3). Irradiated mice were euthanized at 7, 21 and 90 days after irradiation (PD 3+7, PD 3+21, PD 3+90) and brain samples were collected for different experimental studies. Hematoxylin-eosin (HE) was utilized to detect the pathomorphological changes of brain tissue; Immunohisto-chemistry were used to detect the protein expression of IBa1 and GFAP; Western blotting were used to detect the protein expression of IL-1β and TNF-α. In the irradiation group, the inflammatory cell infiltration was observed in the cerebellum and prefrontal cortex, and the thickness of external granular layer (EGL) narrowed. Purkinje cells migrated to internal granular layer (IGL) and some cells were lost in the cerebellum. Compared with the control group, the number of IBa1 positive cells increased at 21 days after irradiation (p<0.05), while the number of GFAP positive cells decreased at 7 days after irradiation in cerebellum (p<0.05). The number of IBa1 positive cells continued to increase until adulthood (p<0.05, p<0.01), and the number of GFAP positive cells continued to decrease until adulthood in prefrontal cortex (p<0.01). The protein expression of IL-1β increased at 90 days after radiation in cerebellum and prefrontal cortex (p<0.05), while the expression of TNF-α did not change. Neonatal exposure to 2 Gy X-ray caused continuous pathological changes in the granulosa cell layer, molecular layer and Purkinje cell layer of cerebellum, and inflammatory cell aggregation in the prefrontal cortex. Neonatal exposure to 2 Gy X-ray increased the number of microglia in the prefrontal cortex and cerebellum, decreased the number of astrocytes. IL-1β is mainly the inflammatory factor.