RADIATION PROTECTION

Progress in research of spectrum unfolding method on neutron spectrum measurement

HUANG Qianming, LIU Bin, LU Ting, WANG Bo, TANG Songqian, LV Huanwen, YING Dongchuan, ZAI Zian

RADIATION PROTECTION. 2022, 42(4): 265-279.

Abstract ( 186 )

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Neutron spectrum unfolding technology is a necessary part of the neutron spectrum measurement system. In recent decades, a large number of studies have been carried out at home and abroad. This paper first introduces the conventional resolution process of neutron spectrum, including unfolding model, response function, unfolding spectrum error, etc.; And then introduces in detail the current research status of neutron spectrum measurement technology at home and abroad and the current research status of neutron spectrum unfolding algorithm, including the relatively mature least squares algorithm, maximum entropy algorithm, etc., as well as emerging neural networks algorithm, Genetic algorithms, etc., summarized the characteristics of different spectrum unfolding algorithms; And furtherly, introduced the spectrum unfolding programs developed according to different spectrum unfolding algorithms, and compared the advantages and disadvantages of different spectrum unfolding algorithms and programs. The SAND series programs which were developed based on the least squares algorithm and the MAXED program developed based on the maximum entropy algorithm are the most powerful and widely used programs for spectrum unfolding. Finally, the development context of the neutron spectrum unfolding method is sorted out, and the differences between domestic and foreign research are summarized. The development direction of the spectrum unfolding algorithm is proposed.

Determination of ⁵⁵Fe and ⁶³Ni in spent resin of nuclear power plant using radiochemical separation and liquid scintillation counting

MA Lina, WANG Lusheng, SONG Lijuan, ZHANG Hui, DAI Xiongxin

RADIATION PROTECTION. 2022, 42(4): 280-286.

Abstract ( 136 )

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In this work, a method for sequential determination of ⁵⁵Fe and ⁶³Ni in spent resins of nuclear power plants was developed. After decomposing the spent resin sample, ⁵⁵Fe and ⁶³Ni ions were first precipitated in the form of hydroxide and subsequently purified by anion exchange chromatography and dimethylglyoxime precipitation. After purification, ⁵⁵Fe and ⁶³Ni were determined by liquid scintillation counting (LSC). The average chemical recovery rate of ⁵⁵Fe and ⁶³Ni was 86% and 90% respectively. The decontamination factors of interfering radionuclides such as ⁶⁰Co, ⁶⁵Zn and ⁵⁴Mn by the sequential determination method were higher than 1 000. The deviation of expected and measured values was less than ±10% through the validation of the analytical method with spiked samples. The measured average activities of ⁵⁵Fe and ⁶³Ni in a set of spent resin samples from its primary loop of a nuclear power plant were (76.2±1.4) kBq/g and (120.0±5.1) kBq/g, respectively.

The optimal design of an aerosol monitor in dynamic gamma radiation field

SHANG Jie, CHEN Jihong, MA Tao, YANG Yi, LI Jianwei, ZHANG Yanting, CHANG Xiang

RADIATION PROTECTION. 2022, 42(4): 287-294.

Abstract ( 125 )

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To meet the needs of online monitoring of α/β radioactive aerosols for dynamic variation of high γ radiation in nuclear power stations and emergency monitoring environments, ion implanted semiconductor detector with passivated surface is redesigned and improved, based on the characteristics of the source term of the monitoring scene. Monte Carlo method was used to simulate the angular response of the optimized dual PIPS detector, and then the structure of the probe was improved. In order to decrease relative standard deviation for angle response, the structure of detection system is improved. Optimized equipment is placed in the ⁶⁰Co and ¹³⁷Cs reference radiation field. Linearity, energy and angular response experiments were performed. It is shown that: 1) The newly designed integrated dual detector has better performance in angular response. 2) Due to anisotropy of the structure and density of assembly material, the construction of probe is optimized, the angular response is no more than 5%, thereby the weight of equipment is effectively reduced. In addition, the linearity and energy response data of the equipment are fitted and the formula is input into the data processing program. Finally, the operating equipment was placed in a ¹³⁷Cs reference radiation field with 10 μGy/h. The test data have shown that the minimum detection limit (MDL) is less than 0.03 Bq/cm³ (for α aerosol) and 0.4 Bq/cm³ (for β aerosol), respectively. As a result, false alarm is significantly avoided.

Application of electret method in investigation of radon precipitation rate in uranium tailing dam

WANG Pan, ZENG Zhiwei, SUN Xueyun, TANG Linjun, HU Penghua, ZHANG Hui

RADIATION PROTECTION. 2022, 42(4): 295-300.

Abstract ( 74 )

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The measurement of radon precipitation rate is of great significance to the decommissioning of China’s uranium mining and metallurgical facilities, and is a key link in evaluating the treatment effect of uranium tailing dams against radon precipitation. In view of the large workload of investigation on radon precipitation rate in uranium tailing dams in China and the long measurement period of instruments, this study proposes a technical method based on electret radon precipitation rate, which shortens the measurement time for radon precipitation rate and increases the daily measurement points. The increased frequency of measurement can be used to quickly investigate the radon precipitation rate in wide-area uranium mining and metallurgical sites. The results of laboratory calibration and field application show that the device is reliable, the method is feasible, and the result is credible. Under the same conditions of the number of measurement points for the radon precipitation rate, the electret method is 2/9 of the RAD7 measurement time.

Discussion on influential factors and measuring methods of total α and total β radioactivity in water

TANG Huaming, ZHANG Weiliang, LUO Haien, HAN Shuaishuai, YANG Guandong, ZHONG Yu

RADIATION PROTECTION. 2022, 42(4): 301-306.

Abstract ( 132 )

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Through a series of comparative experiments and relvant data, experimental factors of total α and total β radioactivity in water using low-background α and β measuring system are discussed in this article. According to the standard curve method in the national standard, the experiments were carried out and the fitting results of curves were analyzed. The intertrack crosstalk experiments were performed using ²⁴¹Am and ⁴⁰K standard powder sources. In the end, factors which might influence sample counts were analyzed by thermoluminescence measuring system. The results show that the linear-fitting results of “mass thickness-net counting rate” curves are well to be used in experiments calculation. The intertrack crosstalk from channel α to channel β needs to be corrected in the measurement of water samples with high radioactivity. Finally, the samples should not be measured immediately after preparation, but should be stored in a dry environment with low background. After storage, the samples should be dried by infrared lamp for a long enough time and should be completely cooled before measurement.

Design and experiment of an adsorbent sampling device for a nuclear air cleaning system

WANG Mingwen, LIANG Fei, MA Tutu, QIU Jilin, WANG Qi, LI Hongfei, XU Yangyang

RADIATION PROTECTION. 2022, 42(4): 307-311.

Abstract ( 71 )

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A sampling device for ventilation cleaning systems of nuclear power plants is designed. The device can provide samples of impregnated activated carbon iodine adsorbent with the same operation history as the iodine adsorbent in the ventilation cleaning system, so as to facilitate regular supervision and test. The relevant validation test results show that the pressure difference between the six sample cups is very close, and the flow rate is within ± 10% of the flow rate of the adsorbent. Therefore, it can be ensured that the activated carbon samples in the six sample cups have the same contact characteristics with the running gas, so they have the same representativeness; The wind speed passing through the six sampling cups is consistent with the wind speed passing through the main body of the system, thus ensuring that the adsorbent in the sampling cup has the same air contact characteristics as the adsorbent in the main body of the system; The installation of sampling device does not influence the operation of ventilation system.

Computational analysis on correlation between soil detection efficiency and soil density in γ energy spectrum analysis

LIU Qingyun, HU Xiang, MA Guoxue, FengYue, LI Lifan, HAN Qiaoye

RADIATION PROTECTION. 2022, 42(4): 312-316.

Abstract ( 122 )

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The accurate calibration of different energy detection efficiency in γ spectrum analysis is an important factor affecting the accuracy of measurement results. In this paper, based on domestic efficiency calibration software Gammacalib, soil samples with different densities were modeled to calculate the corresponding detection efficiency, and compared with the value measured by standard sources to verify the accuracy of Gammacalib. According to the calibration results of Gammacalib, the relative detection efficiency with soil density was analyzed, and the ε~ρ regression equation was obtained. Results for standard soil sources, the relative deviation between active efficiency and Gammacalib ranged from -7.6% to 8.1%, and efficiency was positively correlated with density, with the correlation coefficient between 0.938 and 0.992. The relative deviation of detection efficiency between the calculation results of Gammacalib and standard source can be acceptable. Gammacalib, the domestic efficiency calibration software, can meet the requirements of daily radiation environment monitoring and nuclear accident emergency monitoring, and the applicability of ε~ρ regression equation is good, which can provide reference for different density and efficiency correction.

Study on numerical simulation of building influence on the flow field under stable stratification

SHI Xuefeng, GUO Dongpeng, LI Yunpeng, YAO Rentai

RADIATION PROTECTION. 2022, 42(4): 317-325.

Abstract ( 107 )

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RNG k-ε turbulence model was used to simulate the influence of cube type building on the flow field structure under different Richardson numbers (Ri_b). And the results were compared with the corresponding wind tunnel results. The CFD numerical simulation results are in good agreement with the wind tunnel results. With the increase of Ri_b, the flow is gradually driven by buoyancy, and the cavity zone of the leeward side of the building is gradually reduced. Especially when Rib exceeds 0.82, buoyancy plays a leading role in the recovery of the flow field.When Ri_b is about 0.21, the structure of the flow field is transformed from turbulent flow to similar flow. The normalized turbulent energy(k/u_H²)high value area on the top of the building disappears with the disappearance of the re-circulation zone. With the increase of downwind distance, the influence of different Ri_b on the flow field structure and k/u_H² gradually appears.

Research on the optimization of the receiving exhaust hood of a smelting furnace for radioactive scrap metal

WU Qingdong, ZHANG Yiliang, ZENG Guan, XUE Xiangming, GU Xiaona, DUAN Yujian, LIU Peiyao, ZHAN Jingming

RADIATION PROTECTION. 2022, 42(4): 326-332.

Abstract ( 81 )

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Purpose: In order to effectively collect radioactive aerosols generated during the re-smelting process of scrap metal in nuclear facilities, and to protect the health of workers, we conducted a research on the optimization of the receiving exhaust hood. Method: A certain radioactive scrap metal smelting furnace was selected as the research object. We established a model, divided the grid, and finally used the Fluent numerical simulation method to simulate the influence of factors such as different heights, different hood sizes, and interference winds on the exhaust hood. Results: The smelting furnace mouth diameter is 0.5 m, there is a cross-wind of 0.3 m/s, and the height of the exhaust hood is 1.5 m. The optimized exhaust hood is a circular hood with a diameter of D=1.4 m, which can effectively eliminate the radioactive aerosol produced by smelting furnace. Conclusion: Compared with the theoretical calculation design, the exhaust hood optimized by the CFD numerical simulation method has reduced the diameter of the exhaust hood by 0.84 m and the air volume by 0.616 m³/s, which saves space and energy. It can provide reference for the design of smelting furnace exhaust hood.

Analysis and evaluation of radiation level of the loaded and unloaded package of 3 m³ natural uranium hexafluoride for transport

ZHUANG Dajie, GONG Daokun, LIAN Yiren, CHEN Lei, WANG Zhipeng, WANG Pengyi, SUN Shutang, SUN Hongchao, LI Guoqiang, ZHANG Jiangang

RADIATION PROTECTION. 2022, 42(4): 333-338.

Abstract ( 71 )

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The radiation source term of the 3 m³ transport container for natural uranium hexafluoride, after full load and unload, is analyzed. The external radiation level of the container is simulated and calculated, so as to provide suggestions for the optimization of radiation protection during the operation and transportation of the container package. The results show that the external γ radiation of the container comes from ²³⁵U, ^234mPa and ²³⁴Pa; When the package is fully loaded, the external radiation level increases with time until the third month; After the container is unloaded, due to the lack of self-shielding of UF₆ and the large residue of decay daughters ²³⁴Th, ^234mPa and ²³⁴Pa, the external radiation level of the container is even higher than the full load package. The maximum radiation levels on the container surface decreased from 167.5 μSv·h^-1 down to 30.3 μSv·h^-1 at the first two months.The surface radiation level of unloaded container was measured after two months and the maximum value was 31.3 μSv·h^-1 and 28.1 μSv·h^-1 respectively. The measured results are consistent with the calculated results, which proved the presumption of the distribution of residual UF₆ is correct. In view of the frequent natural UF₆ transportation activities and large transportation volume, the radiation protection for the residual containers should not be ignored. The exposure of workers can be reduced by increasing the vacant time of residual containers, remote operation and reducing the operation time.

Cross-section library study on the activated source term calculation at the upper and lower ends of spent fuel assembly

ZHANG Liying, CAO Liangzhi, WANG Xiaoxia, GAO Guiling

RADIATION PROTECTION. 2022, 42(4): 339-344.

Abstract ( 61 )

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Based on the needs of refined analysis of activated source term at the upper and lower ends of the spent fuel assembly, through comparative analysis, different cross section libraries are applied to the calculation of activated source term at the upper and lower ends of the spent fuel assembly. The main conclusions include: The active region cross section library and thermal neutron cross section library have large calculation errors when applied to the calculation of the activated source term. The combined cross section library is conservative in the processing of the resonance group and the fast group cross-section, which leads to the conservative analysis results. The problem related cross section library is closer to the real situation.

A preliminary study on the simultaneous effect of irradiation and heat on physicochemical properties and microstructure of bentonite

HU Bo, LIU Wei, YANG Zhongtian

RADIATION PROTECTION. 2022, 42(4): 345-353.

Abstract ( 81 )

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In order to study the impact on bentonite under irradiation and heat simultaneous effect, the modified Na-bentonite taken from Gaomiaozi in Inner Mongolia was studied. The samples were heated to 90 ℃ and irradiated with different dose rates and cumulative doses. The results show that: when the cumulative dose was 0.37 MGy or 0.74 MGy, the water absorption, pH value, cation exchange capacity, layer charge and cell size of montmorillonite of aging samples were smaller than those of reference samples, and reduced by maximum of 18.4%, 7.8%, 3.4%, 2.9% and 15.6%, respectively. These effects decreased with the decrease of dose rate, but the aging effect had small on thermal stability and mineral compositions. It is proposed that these influencing factors on bentonite properties should be considered in the design of engineering barriers of geological disposal repository.

A simulation study on the influence on tissue dose caused by lung density change

XIAO Yang, HUANG Shunping, LI Heng, WU Yan, LI Jin, LIU Hong, CHEN Xiaolin

RADIATION PROTECTION. 2022, 42(4): 354-360.

Abstract ( 79 )

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To explore the effects of changes in the physical properties of lung caused by breathing exercise on the absorbed dose of lung and tumor, Monte Carlo method for simulation calculation using EGSnrc was used to convert the collected lung data of different densities into corresponding phantom materials, to establish tissue models under different breathing states, and to analyze the differences between PDD (percentage depth dose) and Profile under different radiation fields. Results showed that, the smaller the radiation field size, the more obvious the difference in tissue absorbed dose under different breathing states. There is no significant difference in lung absorbed dose under the 10 cm×10 cm radiation field, and the tumor absorbed dose is reduced by 3.86%. When the radiation field is smaller than 5 cm×5 cm, the absorbed dose of upstream lung increases first and then decreases with the increase of depth. When radiation field is 1 cm×1 cm, the maximum difference of lung absorbed dose is 46.87%, the tumor absorbed dose is reduced by 6.97%. At the same time, there is an obvious electron imbalance in low-density tissue under small radiation field. The difference in tissue dose caused by breathing exercise under 3D-CRT technology is smaller than IMRT and SBRT. Under breathing gating technology, clinicians can combine the TPS algorithm to delineate the target area at the end of inspiration, which can reduce the normal lung tissue dose and increase the target area dose.

The nuclear submarine accident of former Soviet Union in 1985 and the evaluation of potential radiation impact on China

YUE Feng, QIAO Qingdang, GUO Cai, ZHU He, GUO Ruiping, GAO Jianwei, WANG Ruiying, LI Wenting

RADIATION PROTECTION. 2022, 42(4): 361-367.

Abstract ( 258 )

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On August 10, 1985, K-431, the former Soviet E-2 class nuclear submarine, suffered a reactor criticality, explosion and combustion accident during refueling. The accident resulted in the death of 10 crew members. Based on the meteorological data at the time of the accident, the unfavorable meteorological conditions for China, and the HYSPLIT program, this paper evaluated the potential radiation impact of the accident source terms on China. The results show that the maximum effective dose for individuals in China is of the order of 10^-5 mSv under the two meteorological conditions. Although the radiation impact of the accident is small, similar threats need to be paid attention, and relevant monitoring and evaluation system needs to be strengthened.

Study on the revision of categorization threshod for nuclear safety supervision of nuclear facilities

PENG Haicheng

RADIATION PROTECTION. 2022, 42(4): 368-373.

Abstract ( 63 )

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Based on the analysis of the background of the categorization threshold quantities and relevant technical documents of nuclear safety supervision, this paper focuses on the main considerations in the revision of relevant standard of the US Department of Energy and its applicability to the safety categorization and its revision of China’s nuclear facility, and puts forward relevant revision recommendations.

Health Phys. Abstracts,Volume 122,Number 5

RADIATION PROTECTION. 2022, 42(4): 374-378.

Abstract ( 62 )

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