Table of Content

20 July 2021 Volume 41 Issue 4

  

Research progress of epidemiology on plutonium workers

GU Xiaona, WANG Zhongwen, LIU Zhanqi, SU Lixia

RADIATION PROTECTION. 2021, 41(4):  289-294. 

Abstract ( 139 )   PDF (953KB) ( 139 )  

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With the development of nuclear technology, plutonium has gradually become the main nuclides in the nuclear fuel system, and the number of people engaged in plutonium operations has increased year on year. However, the health effects of plutonium need to be further determined. Some nuclear powers in the world have conducted some epidemiological studies on the health effects of workers exposed to plutonium. The research results are different for plutonium workers in different facilities. The Mayak workers had a relatively high dose of internal radiation exposure, and the cohort studies had sufficient statistical capacity. However, the cohort study of low-level plutonium radiation exposure in the United States and the United Kingdom had not determined the dose-effect relationship. The reliability of epidemiological studies for plutonium workers depends on the accuracy of internal organ dose assessment. There is still a certain gap between China and other major nuclear powers in the world about the research on the health effects of plutonium workers. It is expected to provide research ideas for the long-term health effects of the plutonium workers in China through this review.

Discussion on the concentrative volume reduction technology of low level radioactive waste of nuclear power plant

ZHENG Wei, WANG Zhaohui, LIN Peng, ZHOU Dongsheng, QIAO Baoquan, ZOU Liping, LIU Xiajie

RADIATION PROTECTION. 2021, 41(4):  295-301. 

Abstract ( 206 )   PDF (1033KB) ( 405 )  

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This article describes the current status of radioactive waste management and the urgent needs for efficient and concentrative volume reduction of radioactive waste in domestic nuclear power plant. The research progress of efficient volume reduction technologies are reviewed and the characteristic of technologies are analyzed to explore the efficient and centralized technology with economic and environmental benefits. This article finds that plasma processing technology has obvious advantages, and proposes a combination volume reduction technology route to provide the technology reference for domestic radioactive waste management.

Research of oxide film properties of AP1000 primary loop

CUI Yujie, WU Mingliang, ZHANG Yi, NIU Qiang, WANG Yongxian, GUO Lixiao, ZHAO Wei, CUI Anxi

RADIATION PROTECTION. 2021, 41(4):  302-308. 

Abstract ( 137 )   PDF (7614KB) ( 57 )  

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The difference between AP1000 and other general PWRs is that its primary loop adopts zinc in-jection and hydrogenation technology, which changes the characteristics of oxide film in the pri-mary loop. The experiment simulates water chemistry condition of AP1000 primary loop in auto-clave to study the characteristics of the oxide film formed on the surface of the three main reactor process equipment materials of F304L, F316, and 690. The results show that the oxide film is a bilayer structure, and the outer oxide film components are mainly Fe₂O₃ and Fe₃O₄. The inner oxide film of F304L and F316 stainless steel is mainly ZnCr₂O₄, and the injected Zn element replaces the iron element in FeCr₂O₄ to form a dense ZnCr₂O₄ oxide layer. A small amount of ZnO and ZnFe₂O₄ is present in the inner oxide film. The inner oxide film of 690 alloy is ZnCr₂O₄, with high content of ZnO and ZnFe₂O₄. Unlike F304L, F316, the oxide film of the 690 alloy contains a small amount of divalent nickel in the form of NiFe₂O₄ and NiCr₂O₄. The addition of zinc and hydrogen makes the oxide film denser and sig-nificantly thinner.

Estimating partial exposure dose by chromosomal aberrations in human peripheral blood lymphocytes in vitro

TIAN Xuelei, LU Xue, CAI Tianjing, TIAN Mei, LIU Qingjie

RADIATION PROTECTION. 2021, 41(4):  309-314. 

Abstract ( 114 )   PDF (910KB) ( 93 )  

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The majority of ionizing radiation accidents is partial exposure. Dolphin's model, recommended by IAEA, is applied to estimate partial exposure dose. Apply this model to calculate the chromosome aberration frequency in exposure area, and then put the chromosome aberration rate into dose-response curve established in vitro to estimate partial exposure dose. For elevating accuracy of partial exposure dose estimation, choosing appropriate dose-response curve is as important as accurately calculating chromosome aberration frequency. However, studies about affection of dose-response curve with different dose rate on partial exposure estimation are limited. Base on this, partial exposure doses were estimated by dic+r frequency and affection of dose-response curve with different dose rate on partial exposure estimation was analyzed in this study. Human peripheral blood lymphocytes (from sample A or sample B) were induced by ⁶⁰Co γ rays at 1 Gy and 5 Gy. Mix the exposed blood with the blood without exposure in 25% or 75% ratio to simulate partial exposure. Analyze dicentric chromosome (dic) plus centromeric ring (r) frequencies in mixed blood via Dolphin's model. Partial doses were estimated by using two curves with different dose rate. As results, dic+r distribution in most of mixed blood samples did not conform to poisson distribution. Based on the dose-response curve consistent with the actual dose rate, most partial doses were close to the actual doses, and the relative deviation was less than 10%. However, the estimated dose of 1 Gy 25% groups of two samples deviate greatly from the actual dose. Applying the dose-response curve inconsistent with the actual dose rate, all the relative deviation between estimated partial doses and actual doses were more than 10%. In conclusion, dic+r can be used to estimate the simulated partial exposure dose in vitro. It is more accuracy for partial exposure dose estimation to apply dose-response curve, which dose rate is same as actual dose rate.

Effects of low dose radiation on intestinal injury in mice

HU Changkun, ZHANG Xuemei, MA Zenchun, GAO Yue

RADIATION PROTECTION. 2021, 41(4):  315-320. 

Abstract ( 167 )   PDF (5036KB) ( 115 )  

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Objective: To compare the changes of intestinal injury indexes in mice exposed to different low-dose radiation, so as to provide scientific basis for the establishment of intestinal injury model in mice exposed to low-dose radiation.Methods: Balb/c mice in three groups were irradiated with three different low dose rates (0.04 Gy/d, 0.12 Gy/d, and 0.2 Gy/d) for five consecutive days (cumulative exposure of 0.2, 0.6, and 1.0 Gy, respectively), and a control group (NC) was established. After the irradiation, the body weight, peripheral blood picture, organ index, malondialdehyde (MDA) content in small intestinal tissue, superoxide dismutase (SOD) activity, immune cytokine (IL-1β, IL-2, IL-6, TNF-α), DNA damage were determined, to explore the optimal dose of low dose radiation for intestinal injury in mice.Results: After five days of continuous irradiation, compared with the control group, the body weight and organ index of mice in each irradiation group were decreased to different extents (p< 0.05 in the spleen index L group, p< 0.01 in the M and H groups). MDA content in small intestinal tissue was significantly increased (p< 0.05 in Group L, and p< 0.01 in Group M and H); SOD content was decreased to different degrees. TNF-α, IL-2, IL-1β and IL-6, the typical proinflammatory factors, showed dose-dependent increases (IL-1β: M, group H p< 0.05, IL-2: M group p< 0.05, group H p< 0.01, TNF-α: M, group H p< 0.05). Group M and H had significant DNA damage and apoptosis.Conclusion: The optimal dose and method for low dose rate radiation induced intestinal injury in mice is 0.12 Gy/d continuous irradiation and 0.6 Gy accumulation for 5 days.

Study on experimental methods of total α and total β radioactivity in water

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

RADIATION PROTECTION. 2021, 41(4):  321-326. 

Abstract ( 180 )   PDF (2735KB) ( 172 )  

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Experimental methods of total α and total β radioactivity in water using low-background α and β measuring system are discussed in this article. Based on a series of comparative experiments, the storage time and temperature of samples, sample preparation method and placement time, which may influence the experimental results, are put forward to reduce the experimental uncertainties. Radon dissolved in water such as well water, tap water and groundwater or infrared lamp may interfere with the counting. After the sample preparation, it is advisable to put the sample at room temperature and dry environment for at least 3 hours before measurement. It shows that storage temperature and storage time have no significant effects on total α and total β radioactivity of water under the condition of sealed storage. Furthermore, acidification of water samples with sulfuric acid recommended by the current national standard, can effectively avoid moisture absorption so as to reduce experimental uncertainty.

Optimization of filtered air intake flow rate to improve control room habitability

WANG Mengxi, LIU Xinjian, QIU Lin

RADIATION PROTECTION. 2021, 41(4):  327-334. 

Abstract ( 129 )   PDF (8042KB) ( 33 )  

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Control room habitability (CRH) shall be maintained to provide adequate protection for control room operators, such that they can remain in the control room envelope (CRE) safely for an extended period and thus control the nuclear facility during normal and accident conditions. Among the parameters determining radioactivity in a control room (in proportion to radiation doses of operators), intake flow rate of filtered air is an important one. The evolution of operator doses in a control room versus intake flow rate was analyzed in this paper. It turns out that the increase of intake flow rate results in larger operator doses when inert radioactive gases are the dominant radioactive substances. On the contrary, increasing intake flow rate does good to lower the irradiation level of control room operators when radioactive aerosols dominate the source terms. The rationality behind this fact was interpreted in detail in this paper, with special attention paid to the unfiltered in-leakage rate. It can be inferred that an optimal intake flow rate probably exists leading to the minimum operator dose under an actual accident condition. This paper then conducted a calculation analysis based on design parameters and source terms of design basis accident of LOCA (a large break loss of coolant accident). The evolution of operator dose was found to be a U-curve versus increasing intake flow rate, which proved the existence of the above mentioned optimal intake flow rate of filtered air for CRH systems. Furthermore, the sensitivity analysis of intake flow rate was carried out to study the effects of unfiltered in-leakage rate and filtered recirculation. This study indicates that intake flow rate of filtered air can significantly influence the CRH. To optimize the radiological habitability of control rooms, the effects of unfiltered in-leakage must be taken into consideration. Besides, filtered recirculation is an effective way to control radiation exposure caused by iodine and radioactive aerosols.

Distribution characteristics of ⁷Be, ⁴⁰K, ⁶⁰Co, ¹³¹I and ¹³⁷Cs in the ambient air of China Nuclear Power Institute and annual effective dose evaluation for the public

DU Yunwu, DENG Xiaoqin, WANG Qian, WANG Liang, ZENG Yi

RADIATION PROTECTION. 2021, 41(4):  335-342. 

Abstract ( 153 )   PDF (1341KB) ( 126 )  

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Based on monitoring data of ⁷Be, ⁴⁰K, ⁶⁰Co, ¹³¹I and ¹³⁷Cs in the ambient air around the China Nuclear Power Institute from 2015 to 2017, the effective doses of residents near the monitoring points of comprehensive building, Nanba Trade Union and Mucheng water plant were roughly estimated. The results showed that the average annual intake of ⁶⁰Co, ¹³¹I and ¹³⁷Cs as well as the induced annual effective doses decreased with the increase of the distance from the nuclear facilities; the average annual intakes of adults, teenagers, children, infants and newborns of residents near the comprehensive building by inhalation of ⁷Be, ⁴⁰K, ⁶⁰Co, ¹³¹I and ¹³⁷Cs are 29.25, 26.48, 20.16, 11.49 and 6.79 Bq/a, respectively; the annual effective doses of teenagers, children, adults, infants and newborns of residents near the comprehensive building caused by inhalation, immersion in the air and ground deposition of ⁶⁰Co, ¹³¹I and ¹³⁷Cs are 133.58, 130.98, 128.61, 120.20 and 118.61 nSv/a, respectively; the dose fraction caused by ⁶⁰Co reached 95.6%, followed by ¹³⁷Cs; the dose fraction caused by surface deposition reached 54%, followed by inhalation; the maximum effective dose caused by ⁶⁰Co, ¹³¹I and ¹³⁷Cs in the youth group of residents near the comprehensive building is 133.58 nSv/a, but this effective dose is only less than 1‰ of the target value of the evaluation dose (0.25 mSv).It can be concluded that ⁶⁰Co, ¹³¹I and ¹³⁷Cs have little influence on the ambient air of the nuclear base under normal operating conditions.

Investigation of natural radioactive environment in a bone coal mine area, in She County, Anhui Province

WEI Xinxiang, ZHANG Linxi, KUANG Fuxiang, XU Naizheng

RADIATION PROTECTION. 2021, 41(4):  343-350. 

Abstract ( 103 )   PDF (4548KB) ( 143 )  

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The γ-radiation air absorbed dose rate and radon concentration were measured in the She County coal mine area of Anhui Province, and the environmental media (soil, rock, stone coal, coal slag, coal gangue, sediment, surface water and groundwater) were systematically collected and analyzed. The results showed that the average gamma dose rate in the mine region is 121.5 nGy/h, which is much higher than the background value of Anhui Province and entire China. The gamma radiation level is controlled by the stratum/lithology, and the high value points are concentrated in bone coal mine. The mean concentrations of indoor and outdoor radon were 116.8 Bq/m³ and 47.1 Bq/m³ respectively, which were significantly higher than the background level. The concentration of ²³⁸U and ²²⁶Ra in bone coal, coal slag, coal gangue and carbonized brick is high, and the internal and external exposure index of carbonized bricks exceeds the radionuclide limit of building materials, so it is strictly prohibited to use them as main building materials. The development of bone coal has caused a significant increase in the concentration of radionuclides in the surrounding river sections, and the total α in the mine water exceeds the sewage discharge limit. Therefore supervision should be strengthened.

Study on properties and structure changes of impregnated activated carbon induced by aging

WANG Kunjun, CHANG Sen, WANG Longjiang, LI Yongguo, HOU Jianrong, QIU Dangui

RADIATION PROTECTION. 2021, 41(4):  351-358. 

Abstract ( 151 )   PDF (4732KB) ( 172 )  

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In order to study the properties and structure changes of impregnated activated carbon caused by aging, the adsorption efficiency, key physical properties, microstructure and thermal stability of impregnated activated carbon aging through in-place application and natural aging in the same batch were analyzed. It was found that that the performance indicators change of impregnated activated carbon was not significant after natural aging for 54 months. While for the impregnated activated carbon aging in-place, its efficiency for adsorbing radioactive methyl iodine dropped to less than 60%, the CCl₄ adsorption rate dropped significantly from the initial nearly 60% to 15%, pH value decreased from 9.7 to 7.2, the iodine adsorption value fell to three-quarters that of new impregnated activated carbon, which is consistent with the declining trend of iodine removal efficiency. SEM and N₂ adsorption tests showed that the microscopic pore structure of the activated carbon samples after aging in-place changed significantly, the pores were blocked and worn seriously, the specific surface area decreased, and the pore width increased. Thermogravimetry (TG) test showed that the weight loss of impregnated activated carbon aging in-place was about 10% at 200-500 ℃. These changes in physical and chemical properties and structure are the main reasons for the aging and declining of iodine-removing properties of impregnated activated carbon.

Design and numerical simulation of a virtual impactor

MA Tao, YANG Yi, SHANG Jie, LI Jianwei, MA Yinghao, CHANG Xiang

RADIATION PROTECTION. 2021, 41(4):  359-364. 

Abstract ( 118 )   PDF (4793KB) ( 145 )  

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The virtual impactor inhales aerosols from the air and collects particulates with specific size. In general, the commonly used virtual impacter has large cutting particle size and works at large flow rate, which may not be applicable to some conditions with limited flow. In this study, a new multi-slit virtual impactor is developed. Its main characteristics are that the impactor can work at high flow rate and low pressure drop. Clean air is injected near the nozzle, which can reduce the loss of aerosol in the impactor. The performance of the virtual impactor was analyzed through numerical simulation. The results show that the cutting particle size of the virtual impactor can reach to 0.2-0.4 μm, and the low pressure drop of 0.08 atm can be obtained even if the total flow is 36 L/min. The cutting particle size can be reduced even smaller by using the virtual impactor with clean air with slit nozzles, and can be collected at a flow rate of 1.8 L/min.

Guidance and enlightenment to radiological emergency provided by revised Radiological Emergency Plan of MEE (NNSA)

GUO Cai, QIAO Qingdang, YUE Feng, WANG Ruiying, YANG Duanjie

RADIATION PROTECTION. 2021, 41(4):  365-369. 

Abstract ( 127 )   PDF (947KB) ( 118 )  

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Enacting and revising emergency plan is the important foundation and a primary task in building emergency management system. In September 2020, Ministry of Ecology and Environment (MEE), also known as National Nuclear Safety Administration (NNSA), published the recently revised Radiological Emergency Plan of MEE (NNSA). By interpreting the emergency task, emergency plan system, emergency classification indicator, emergency organizations and their responsibilities, emergency response mechanism, emergency preparedness of the revised Radiological Emergency Plan, guidance and enlightenment are provided to radiological emergency preparedness and response in China.

Experience feedback on nuclear accident emergency drill in a certain nuclear power plant

WANG Bing

RADIATION PROTECTION. 2021, 41(4):  370-373. 

Abstract ( 145 )   PDF (3993KB) ( 80 )  

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After the Fukushima nuclear accident in Japan, higher requirements were put forward to nuclear emergency drills among global nuclear power plants. Experience feedback on these requirements and drills were summarized, combined with good practice of a certain nuclear power plant.