Table of Content

20 January 2020 Volume 40 Issue 1

  

Weakly penetrating radiation and personal dose monitoring in Tianwan Nuclear Power Station

HOU Bingjun, ZHAO Honghe, WEI Yingjing, LI Zhonghua

RADIATION PROTECTION. 2020, 40(1):  1-9. 

Abstract ( 198 )   PDF (4059KB) ( 137 )  

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During the two refueling outages of the Tianwan Nuclear Power Station, the investigation of weakly penetrating radiation of Units 1 and 2 was carried out, mainly including radiation dose rate monitoring at sites that may have a higher probability of weakly penetrating radiation, the weakly penetrating radiation dose monitoring received by some representative workers and the protective effect test of protective equipment. From the measurement results of weak penetrating radiation, the radionuclides deposited on the surface of the maintenance equipment of Tianwan nuclear power plant are basically the same, including ⁵⁸Co, ⁶⁰Co, ⁹⁵Nb, ⁹⁵Zr, ⁵¹Cr, ¹²⁴Sb, ⁵⁴Mn, ^110mAg, ⁵⁹Fe, etc. The β-ray energy is mainly concentrated below 600 keV.It is measured that the maximum value of H·′(3)/H·^*(10) is 2.08 and H·′(0.07)/H·^*(10) has a maximum value of 34.9 for reactor coolant pump item; H·′(3)/H·^*(10) has a maximum value of 2.58 and H·′(0.07)/H·^*(10) has a maximum value of 10.7 for the steam generator item; H·′(3)/H·^*(10) has a maximum value of 1.25, H·′(0.07)/H·^*(10) has a maximum value of 26.4 for the reactor item; The maximum value of H·′(3)/H·^*(10) is 3.80 and H·′(0.07)/H·^*(10) has a maximum value of 55.6 for the other pumps item; H·′(3)/H·^*(10) has a maximum value of 1.15 and the monitoring value of H·′(0.07)/H·^*(10) is 4.18 for the valves item. The maximum value of H·′(3)/H·^*(10) is 1.53 and H·′(0.07)/H·^*(10) has the maximum value of 2.16 for the other items. The results of weakly penetration dose monitoring showed that the maximum values of H_p(0.07)/H_p(10) and H_p(3)/H_p(10) are 7.66 and 3.73 respectively, and the personal dose equivalent H_p(10) during the overhaul monitoring period are all below 0.35 mSv. In addition, the personal dose equivalent H_p(10) of the entire staff in these overhauls is less than 2 mSv. It indicates that H_p(0.07)and H_p(3) are less likely to exceed the national standard personal dose limit of 500 mSv/a and the new IAEA limit of 20 mSv/a, respectively. It is suggested to carry out eye crystal dose and skin dose monitoring for special maintenance personnel such as reactor coolant pump maintenance, reactor pool cleaning, KBA system pumps and valves maintenance, radioactive waste sorting, etc.

Influence of ²¹⁰Bi on calculation of ²¹⁰Po activity concentration in air aerosol

ZHANG Jing, LI Zhou, LI Pengxiang, BAO Li, WANG Ruijun, SONG Qinnan, MA Xuyuan, YI Wujing

RADIATION PROTECTION. 2020, 40(1):  10-15. 

Abstract ( 138 )   PDF (3390KB) ( 141 )  

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²¹⁰Pb and ²¹⁰Po in aerosol are in disequilibrium and separated by the short-lived radionuclide ²¹⁰Bi. The initial activity concentration of ²¹⁰Bi is often unknown, and the ²¹⁰Po activity concentration in aerosol is difficult to be estimated to the initial sampling time. This article analyzes the effect of the short-lived radionuclide ²¹⁰Bi upon the calculation of activity concentration of ²¹⁰Po. In most of the actual conditions, the activity concentration ratios of ²¹⁰Po/²¹⁰Pb in air are less 1, and the ratio of ²¹⁰Bi/²¹⁰Pb in air should be considered and ²¹⁰Bi needs to be measured quickly within one month. Otherwise, ²¹⁰Bi/²¹⁰Pb cannot be measured. It is recommended to take short-time sampling, rapid measurement and other measures to avoid such errors when the activity concentration of ²¹⁰Bi in the initial air is unknown.

Research and design of radiation zoning outside the floating nuclear power plant’s reactor compartment shell and bottom

TAN Mei, GUO Jian, ZHANG Jincai, CHEN Gang

RADIATION PROTECTION. 2020, 40(1):  16-22. 

Abstract ( 171 )   PDF (3061KB) ( 299 )  

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The floating nuclear power plant (FNPP) is a nuclear power plant located in sea area; and the main radiation source is concentrated in the cabin area. Inside the bulkhead is a ship cabin containing radiation sources such as reactors and primary circuit systems. The outer space of the reactor compartment includes side and the bottom of the ship. The radiation zone inside the bulkhead is similar to that of onshore nuclear power plant, while the outer space requires additional consideration. For the FNPP’s radiation zoning standard selection, the design method of the onshore nuclear power plant can be referred to the reactor compartment, but the reference area is lacking in the area outside. In this paper, the general characteristics of the FNPP’s radiation are given. The constraints affecting the radiation zone outside are studied. The solution for the design of the side and bottom’s radiation zoning is given, taking into account the radiation safety, high radiation area management costs and economic cost. The results can be as engineering design reference.

Natural radionuclides and radiological assessment for building materials used in reef engineering in the South China Sea

LIN Wuhui, CHEN Xiaoxia, YU Kefu, LIU Xinming, MO Zhenni, FENG Liangliang, HE Xianwen

RADIATION PROTECTION. 2020, 40(1):  23-30. 

Abstract ( 156 )   PDF (2129KB) ( 145 )  

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Two dominant building materials of coral sand and coral skeleton were measured using high purity germanium γ spectrometry with high energy resolution for the first time. The activities of ²³⁸U, ²²⁶Ra, ²²⁸Ra, ⁴⁰K in coral sand and coral skeleton were 24.8 Bq/kg, 2.38 Bq/kg, 2.10 Bq/kg, 11.6 Bq/kg and 28.7 Bq/kg, 3.47 Bq/kg, 12.6 Bq/kg, 10.9 Bq/kg, respectively. The radioactive level of coral sand and coral skeleton was 1%-10% of the recommended value and limiting value provided by the international organizations. After comparison of radioactivity in a variety of building materials, we found that coral sand and coral skeleton had the lowest radioactive level. These building materials of low radioactivity can be potentially used in the construction of the low radioactive laboratory and used as dilution to reduce radioactivity during the production of building materials (coal ash) with high radioactivity.

Assessment of public dose caused by effluent discharge at Tianwan nuclear plant (2007—2016)

JIANG Konghua, LIU Hanhan, TIAN Qing, SUN Kaibin

RADIATION PROTECTION. 2020, 40(1):  31-37. 

Abstract ( 169 )   PDF (1275KB) ( 124 )  

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Calculation model and parameters of public dose caused by the gaseous and liquid effluent discharge is introduced. The biggest individual effective dose, critical groups, critical exposure pathways, critical nuclides, public collective effective dose and normalized emissions of gaseous and liquid effluents are given from 2007 to 2016. The largest individual collective dose each year is compared with the designed value, the national standard GB 6249—2011 prescribed dose constraint value, and natural background radiation level. The results show that the impact to the public caused by the annual effluent discharge of Tianwan nuclear power plant can be neglected under safe and stable operation condition.

Optimization research on neutron shielding material component based on genetic algorithm

CHEN Faguo, LI Guodong, YANG Mingming, HAN Yi, LIANG Runcheng

RADIATION PROTECTION. 2020, 40(1):  38-44. 

Abstract ( 183 )   PDF (5420KB) ( 279 )  

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Based on the fast non-dominated sorting genetic algorithm NSGA-II, multi-objective optimization of shielding design was studied, and automatic optimization design code for composite neutron shielding material component was developed. Aiming at the minimum shielding dose and material density, the effectiveness of the code is demonstrated by an example of 30 cm thick slab shield, which is composed of polyethylene, lead, steel, aluminum, boron and lithium homogeneously. Combining the shielding optimization method based on genetic algorithm and the experience of designer, multi-objective optimization of shielding design can be achieved more efficiently.

Safety analysis on efficiency test of iodine absorbers in ventilation systems of nuclear power plants

YAO Yanyan, GAO Linfeng, WU Zhenlong, ZHAO Gaoxin

RADIATION PROTECTION. 2020, 40(1):  45-51. 

Abstract ( 141 )   PDF (1463KB) ( 308 )  

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This paper outlines two methods for the efficiency test of iodine adsorbers in ventilation systems of nuclear power plants: Freon method and radioactive methyl iodide method, and analyzes the implementation way of each method and the advantages and disadvantages under each application process. The safety of the on-site efficiency test for iodine adsorbers is analyzed in detail, and the corresponding preventive and treatment measures are proposed for the unsafe factors, which including the safety related to testing process and safety related to operating conditions, as well as the failure of the iodine removal circuit.

Impact test and numerical simulation on a model container for transport of medical radioactive sources

LI Guoqiang, LI Zhiqiang, LUO Xiaowei

RADIATION PROTECTION. 2020, 40(1):  52-57. 

Abstract ( 107 )   PDF (10815KB) ( 40 )  

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A model container is designed to transport and store radio-therapeutic sealed sources with 1,141 mm×1,206 mm dimension and about 3,600 kg in mass. The container belongs to type B package when being loaded maximum activity up to 444 TBq (12,000 Ci)for ⁶⁰Co. The package should be tested subject to the free drop test I (i.e. impact test) according to GB 11806 and SSR-6, which is one of test items for demonstrating its ability to withstand accident conditions of transport. The ANSYS/LS-DYNA code based on finite element method is used to analyze stress and deformation during impact. Under top corner impact condition, the results show that there is larger stress at the impacted position about 200 mm×200 mm square with 45.9 mm maximum deformation and two bolts may be ruptured. Stress on the outer shell of the outer container was measured during the test and the deformation of the container was measured after the test. The results show consistency between calculation and test, which verifies that finite elements method can be used to well predict the stress and deformation fields before intensive impact destructive test.

Preliminary study on vitrification process conditions of incineration ash

ZHANG Yu, CHU Haoran, ZHENG Bowen, XU Wei, YANG Lili, RUAN Jiasheng

RADIATION PROTECTION. 2020, 40(1):  58-66. 

Abstract ( 148 )   PDF (14746KB) ( 39 )  

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A kind of solidified glass is prepared with simulated incineration ash and additives in certain proportion based on research and analysis of domestic and foreign vitrification formulas which combines our specific processing objects and processing requirements. The solidified glass is apparently hard, smooth, dense with a density of higher than 2.6 g/cm³ and shows a uniform glassy substance in XRD tests, and thus proves a feasible melting process of incineration ash treatment. Experimental results show that the melting temperature of incineration ash decreases with the increase of borax content of additive and the fluidity and molding effect are also significantly improved. Experimental conditions for the initial incineration ash melting treatment are as follows: the treatment temperature should be higher than 1 100 ℃ when the addition amount of B₂O₃ and Na₂O was 30%-35%; the treatment temperature can be lowered to 1 000 ℃ when the addition amount of B₂O₃ and Na₂O reaches 40%. Experiments of real incineration ash under the above mentioned same processing conditions obtained same results.

Vitrification technologies of high level radioactive liquid waste in Japan

LU Jiawei, GUO Zifang, WU Zhihao, CHEN Geng, WENG Hanqin, LIN Mingzhang, CHEN Xiaoli, ZHOU Qiang

RADIATION PROTECTION. 2020, 40(1):  67-77. 

Abstract ( 194 )   PDF (10513KB) ( 139 )  

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This paper mainly introduces the vitrification facilities and operation of reprocessing plants in Tokai and Rokkasho, as well as the improvement measures taken in Japan in terms of vitrification facilities, operation methods and raw material components in solving the problems like blockage of outlet at bottom of furnace, and leakage of spent fuel storage pool during the current vitrification process. In future research projects, Japan will focus on developing standards for low level radioactive waste vitrification and developing advanced technologies such as cold crucible and plasma vitrification. In the same time, Japan will strengthen the research on formulas and advanced processes to achieve the capacity reduction and economy of vitrification. Japan’s experience and lessons learned are of great significance to the development of vitrification in China.

Application of infrared imaging in radiation protection and other medical fields

YAO Zhen, ZHAO Minyan, LIU Yulong

RADIATION PROTECTION. 2020, 40(1):  78-83. 

Abstract ( 200 )   PDF (4083KB) ( 281 )  

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Infrared imaging technology is another new branch after traditional medical imaging technology such as X-ray, Ultrasonic, CT, MRI, etc. It has the advantages of non-invasive, non-destructive, simple and fast, and its application can be used in multiple clinical departments. This paper mainly describes the principle of medical infrared imaging, its influencing factors and its application in radiation protection and other medical fields.