Table of Content

20 September 2026 Volume 46 Issue 5

  

Progress of metrological techniques for naturally occurring radon isotopes

XIAO Detao, LIANG Juncheng, HE Zhengzhong, TANG Quan

RADIATION PROTECTION. 2026, 46(5):  377-386.  doi:10.27045/j.1000-8187.202605001

Abstract ( 32 )   PDF (2062KB) ( 2 )  

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Radon isotope metrological techniques are the important guarantee for the reliability of the measurement results of environmental radon isotopes and their daughters. This article introduces the current development status of radon isotope sources, and the metrological techniques of radon, thoron and radon exhalation rate, summarizes the performance characteristics of radon isotope sources, radon chambers, thoron chambers and radon exhalation rate standard devices in various countries, and points out some challenges in radon isotope metrological techniques.

Emerging problems of radon protection in uranium mining and metallurgy

LI Xianjie, HU Penghua, LIU Xiaochen, WANG Ziye

RADIATION PROTECTION. 2026, 46(5):  387-391.  doi:10.27045/j.1000-8187.202605002

Abstract ( 22 )   PDF (935KB) ( 1 )  

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In its Publication No.137(2017), the International Commission on Radiological Protection (ICRP) updated the dose conversion factors for radon and radon progeny exposure, replacing the value of 1.4 mSv/(mJ·h·m^-3) adopted in the 1990s with 3.3 mSv/(mJ·h·m^-3) for mines and 5.7 mSv/(mJ·h·m^-3) for indoor workplaces. This has resulted in a corresponding reduction in the control limits for radon and radon progeny concentrations in uranium mines and mills (from 2 700 to 2 000 Bq/m³ for underground mines and from 2 400 to 600 Bq/m³ for processing plants), which will significantly increase the cost of radon mitigation and protection. With advances and changes in uranium mining and milling methods, new radon contamination issues, such as high leakage and high release under high negative pressure, have emerged. Furthermore, due to the development and utilization of naturally occurring radioactive material (NORM) resources, the measurement and control of thoron and its progeny have become new challenges facing the field of radon protection.

Research and integration proposal of domestic and international standard systems for radon and its progeny measurement

GAN Yuhang, LIU Xiaochen, ZHANG Qian

RADIATION PROTECTION. 2026, 46(5):  392-403.  doi:10.27045/j.1000-8187.202605003

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Radon and its short-lived progeny constitute the major source of natural radiation exposure to the public, and their accurate measurement forms an important technical basis for environmental radiation monitoring and radiation protection. This paper conducts a comparative study between the ISO 11665 series of international standards and relevant Chinese standards for the measurement of radon and its progeny. It systematically compares their differences in terms of system architecture, measurement methods, key technical parameters and practical application orientation. The analysis reveals notable deficiencies in Chinese standards, including fragmented standard system, outdated versions of some standards, lack of direct measurement methods for radon progeny, and absence of standardized specifications for alpha-spectrometry. To address these issues, this paper proposes an idea for integrating and revising domestic standards by drawing on the ISO 11665 series. A 16-part standard system framework “Measurement Methods for Radon and Its Progeny in Air” is constructed, which consists of three tiers: general principles, measurement principles, and application fields. It provides a systematic reference for establishing a well-coordinated and comprehensive domestic standard system for radon measurement.

Theoretical simulation and experimental study on the effect of rainfall on soil radon concentration

XIAO Lei, WANG Nanping

RADIATION PROTECTION. 2026, 46(5):  405-416.  doi:10.27045/j.1000-8187.202605004

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To reveal the influence law and mechanism of rainfall on soil radon concentration, this study combined with experimental observation and numerical simulation to research the dynamic response characteristics of soil radon concentration under rainfall conditions. Real-time observation under different rainfall were carried out, and the dynamic changes of parameters such as precipitation, soil radon concentration, and soil gas permeability were continuously monitored. A theoretical assumption of soil radon concentration was proposed, which was composed of four mechanisms including pore reduce, gas attenuation, cover layer, and rainfall infiltration. A two-layer soil water-air radon transport model was constructed to achieve theoretical simulation of the radon concentration field during rainfall infiltration. The research results show that the four-coupled mechanism model constructed by the two-layer soil model can reproduce the response trend of soil radon concentration in the rainfall experiment, which first rises and then drops. About 94% of the model prediction values fall within the ±2σ range of the measured values, close to the theoretical coverage rate of 2σ confidence level (95.4%). Normalization analysis indicates that the cover layer effect is the parameter among the four mechanisms that is most sensitive to water content changes. The infiltration convective velocity decreases after reaching the peak, revealing the convective upper limit effect caused by the disappearance of the gas phase channel under high water content. As the total rainfall increased from 64 mm to 227 mm, the simulation deviation changed from the lag of radon concentration rise to systematic underestimation. The average absolute error (MAE) increased from 1.96 to 3.81 kBq/m³, reflecting that the model's expression of the surface closure and radon accumulation mechanism caused by the cover layer effect during the heavy rainfall period is not yet sufficient, and there is still needed to improve in the amplitude of the transient response of the four-coupled mechanisms. The research results can provide a theoretical basis for eliminating the interference of rainfall and improving the application of soil radon concentration in radon geological potential mapping and radon data processing in uranium geological exploration.

Effect of pore structure on radon adsorption in porous materials

TANG Zengming, XIAO Detao, DENG Xiangyuan, WANG Fuxing, CHENG Weiqing

RADIATION PROTECTION. 2026, 46(5):  418-425.  doi:10.27045/j.1000-8187.202605005

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To investigate the impact of porous material pore structure (characterized by pore diameter, pore shape, pore volume, and specific surface area) on radon dynamic adsorption, experiments were conducted using molecular sieves with an uniform pore diameter (3A, 4A, 5A, ZSM-5, and 13X types) and activated carbon materials with different pore shapes (coconut shell activated carbon and activated carbon fibers) in a standard radon chamber. The results indicated that pore size matching is crucial to enhancing adsorption thermodynamics, with ZSM-5 molecular sieve exhibiting optimal performance among the several molecular sieve materials due to its effective pore diameter of 5.3~5.8 Å; pore shape significantly affects adsorption kinetics. Coconut shell activated carbon, featuring large effective micropore volume and hierarchically connected pore structure serving as mass transfer channels, achieved a radon adsorption coefficient of 4.45 L/g, which is much higher than that of activated carbon fibers (1.52 L/g), which have shorter pores and smaller effective micropore volumes. While increasing the pore-specific surface area and total pore volume of the adsorbent, increasing the effective micropore volume in the 0.5~0.7 nm range and constructing an appropriate amount of mesopores can enhance radon adsorption capacity. These findings can provide a basis for the targeted design of efficient radon adsorbents.

Variation characteristics and influencing factors of radon and radon progeny levels in tourist karst caves in Guangxi,China:A preliminary analysis

WU Jiacheng, WU Guohui, YANG Hang, LUO Jizun, ZHONG Jie, YU Yang

RADIATION PROTECTION. 2026, 46(5):  427-436.  doi:10.27045/j.1000-8187.202605006

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Three tourist karst caves in Guangxi,namely Laojun Cave,Jiulong Cave and Jinlun Cave,all of which are solution caves,were selected for year-round monthly fixed-site monitoring of airborne radon,radon progeny,radon in water and microclimatic parameters,and effective doses under specific exposure scenarios were estimated.The results showed that the levels of airborne radon,radon progeny and radon in cave water were highest in Jiulong Cave,followed by Jinlun Cave and Laojun Cave.The annual mean airborne radon concentrations were 211.42±194.73,104.97±52.33 and 13.74±8.33 Bq/m³,respectively; the annual mean radon progeny concentrations were 135.07±124.94,66.31±37.88 and 8.93±8.22 Bq/m³,respectively;and the annual mean radon concentrations in cave water were 3.060±3.141, 0.745±0.329 and 0.338±0.076 Bq/L,respectively.Airborne radon and radon progeny concentrations in Jiulong Cave and Jinlun Cave were relatively high from June to September,while Laojun Cave remained at a low level overall.Jiulong Cave had the highest radon level in cave water and showed a relatively clear correspondence with the monthly variation of airborne radon.The analysis of microclimatic parameters indicated that airborne radon was relatively clearly related to air pressure,and airborne radon was negatively correlated with air pressure in both Jiulong Cave and Jinlun Cave.Dose estimation indicated that the effective dose was 0.000 17-0.002 5 mSv for a typical 2 h tourist visit scenario and 0.008-0.125 mSv for a 100 h cumulative occupancy scenario.The results may provide a reference for radon environmental monitoring and radiation protection management in tourist karst caves.

A study on the variation patterns of outdoor radon concentration in the Nanning region

LIN Chen, ZHAN Liqun, SU Chuancheng, XU Mingfa, XU Pin, PENG Wenbin, CHANG Qing

RADIATION PROTECTION. 2026, 46(5):  437-445.  doi:10.27045/j.1000-8187.202605007

Abstract ( 27 )   PDF (3493KB) ( 1 )  

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To investigate the levels and variation patterns of outdoor atmospheric radon concentration in Nanning, Guangxi, continuous monitoring was conducted over two one-year periods at an urban central site of Nanning, covering April 2023-March 2024 and October 2024-September 2025. Three mainstream domestic and international radon monitors were deployed for synchronous measurements. Combined with meteorological data, the dynamic variations of radon concentration and its key influencing factors were thoroughly analyzed. The acquisition rate of valid monitoring data was 95.0%. The results indicated that the average outdoor atmospheric radon concentration in urban Nanning from 2023 to 2025 was (14.5±9.7) Bq/m³, exhibiting distinct diurnal and seasonal variations. For diurnal cycles, the radon concentration peaked at 6:00-7:00 (18.0 Bq/m³) and reached its minimum at 14:00-15:00 (11.7 Bq/m³). Seasonally, the lowest concentrations occurred from June to August, while the highest values appeared from November to February. Hourly correlation analysis revealed that air temperature and wind speed were negatively correlated with radon concentration, while the Air Quality Index (AQI) showed a positive correlation. This study provides scientific data support for radon exposure dose assessment, atmospheric boundary layer research, and environmental radiation monitoring in the Nanning area.

Survey and analysis on soil and environmental radon concentration levels in Shenzhen

LIANG Xuehui, LI Yaqin, GE Yan, LIU Haigui, WU Zhengxin, YAN Qiang, LIU Guoqing

RADIATION PROTECTION. 2026, 46(5):  447-454.  doi:10.27045/j.1000-8187.202605008

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This study comprehensively investigates the radon concentration levels in soil and ambient air in Shenzhen, providing scientific basis for radiation environmental impact assessment. From March to October 2025, soil radon concentration, soil radon exhalation rate, and ambient air radon concentration were measured at 151 sites in Shenzhen. Soil radon concentrations in Shenzhen range from 3.72×10³ to 3.44×10⁴ Bq·m^-3. In-situ ambient air radon concentrations range from 5.60 to 19.46 Bq·m^-3.The soil radon concentration in Shenzhen exhibited a clear seasonal variation, with higher concentrations in the dry season and lower concentrations in the rainy season. Soil moisture content is the key factor determining the radon exhalation rate, which subsequently affects the soil radon concentration levels. The seasonal variation of outdoor air radon concentration in Shenzhen was not significant. Ambient air radon concentration showed a weak correlation with soil radon concentration, while no correlation was observed with soil radon exhalation rate. The levels of soil and outdoor air radon in Shenzhen are within the normal background range and show no significant difference from other regions in China or abroad.

Research on the attribution of lung cancer in miners based on different risk factors

REN Yue, LI Youchen, LIU Senlin

RADIATION PROTECTION. 2026, 46(5):  456-461.  doi:10.27045/j.1000-8187.202605009

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Radon and its progeny are classified as Group 1 carcinogens. The attribution determination of lung cancer caused by high radon exposure among miners is key to the diagnosis of occupational radioactive tumors. To optimize the attribution method for radon-induced lung cancer in China and reduce the attribution bias caused by the transfer of risks across populations, this study constructed a new attribution method based on the excess relative risk (ERR) coefficient of radon-induced lung cancer obtained from the uranium miner cohort study in China. 177 cases of miner lung cancer with a history of smoking were selected, and the attribution analysis was conducted simultaneously using both the new method and the method of GBZ 97—2017. The attribution results of different methods were compared and the causes of the differences were analyzed. The results showed that the total attribution rates of the two methods were similar (new method 45%, standard method 43%), but there was a significant difference in the <20WLM low-dose area. The attributable rate of the new method was only 3%, which was 1/4 of the standard method. A total of 16 cases had conflicting attribution results. Among them, 6 cases with low radon exposure and low attained age could be attributed by the standard method but not by the new method, and 10 cases with high radon exposure and high attained age could be attributed by the new method but not by the standard method. In summary, the new method based on the ERR coefficient of the local cohort has a higher dose correlation and lower age correlation, which can effectively avoid the uncertainty caused by using data from foreign populations and is in line with the characteristics of the Chinese population and the continuity of occupational health policies. It provides core methodological support and a data reference for the optimization and upgrading of the attribution method for radon-induced lung cancer in China.

Analysis of radon concentration distribution and effective dose attribution of underground metal mines based on coupling of depth gradient, ventilation conditions and occupational exposure

CAO Faming, WANG Zhe, DENG Lei, ZHOU Ning

RADIATION PROTECTION. 2026, 46(5):  463-468.  doi:10.27045/j.1000-8187.202605010

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Objective To systematically reveal the distribution law of underground radon concentration in metal mines under the coupled effects of depth gradient,ventilation conditions and occupational exposure,accurately identify high-risk areas and exposed populations,and carry out dosimetric attribution and risk assessment.Methods A retrospective analysis was performed on 62 groups of underground monitoring data collected from underground metal mines in the Gannan area of Jiangxi Province.A RAD7 radon detector was adopted for field measurement.The UNSCEAR recommended model was used to estimate miners’annual effective dose.Normality test and homogeneity of variance test were conducted to verify the applicability of the data,and analysis of variance as well as multiple linear regression models were applied to analyze the multi-factor coupling effects. Results The arithmetic mean of underground radon concentration was(499±632)Bq/m³ with a median of 285 Bq/m³,and 16.1%of the measuring points exceeded 1 000 Bq/m³.Radon concentration increased significantly with the rise of mining depth(P＜0.001).The average radon concentration at mining depth≥400 m was(1 422±919)Bq/m³,which was 6.9 times that of shallow areas(depth＜100 m).There was a significant negative correlation between effective ventilation rate and radon concentration(P＜0.001).When the ventilation rate was less than 60%,the average radon concentration reached(2003±900)Bq/m³,while it decreased to(128±59)Bq/m³ when the ventilation rate was≥90%.There were significant differences in exposure levels among different occupational groups(P＜0.001).The median annual effective dose of extraction workers was 3.917 mSv.The data passed normality and homogeneity of variance tests and met the prerequisites for analysis of variance.The adjusted R² of the multiple linear regression model was 0.68.The annual effective dose increased by 0.65 mSv per 100 m increase in mining depth,and decreased by 2.70 mSv per 10%improvement in effective ventilation rate. Conclusion Radon pollution in underground metal mines is characterized by“generally controllable with partial over-limit areas”.The coupling of deep mining,low ventilation efficiency and long-term exposure of extraction workers is the core cause of high radiation dose.Differentiated and targeted ventilation optimization and occupational health management strategies should be implemented for deep mining areas(≥400 m)andextraction workers.

Study on numerical calculation and regulation of radon concentration in coal mine ventilation networks

FAN Zhihao, MA Wei, YANG Junlei

RADIATION PROTECTION. 2026, 46(5):  469-476.  doi:10.27045/j.1000-8187.202605011

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The most prominent radioactive occupational hazard factor in non-uranium mines such as coal mines is excessive exposure to radon underground. To obtain the overall radon concentration data of the coal mine ventilation network and ensure that the underground radon concentration is within a safe level, a method for calculating the underground radon concentration based on the principle of node air volume balance and the mathematical model of radon concentration distribution, as well as the regulation method when the radon concentration in a branch exceeds the limit, was studied. Taking a certain mine in Shaanxi as the research object, through the combination of numerical calculation and on-site testing, radon measurement points were first set up at the return air outlet, intake air outlet and main passage of the fully mechanized mining face according to the ventilation network structure of the mine, and the radon exhalation rate was calculated based on the measurement results. Then, combined with the air volume, cross-sectional size and length of each branch, the radon concentration data for each branch in the ventilation network were calculated. When the radon concentration in a certain branch exceeded the limit, the ventilation demand to meet the safety threshold was calculated by reverse calculation in the concentration-exceeding area, and the regulation was carried out according to the calculation to bring the radon concentration in the branch back to a safe range. Verified by on-site measurements at 5 nodes, the absolute deviation between the radon concentration calculation results and the measured data is within 11%, and the regulation measures taken based on the calculation results successfully reached the expected level, verifying the reliability of the calculation results. The research results can provide theoretical reference for the prevention and control of radon gas in mines.

Measurement of radon exhalation parameters in fired common brick and its contribution to indoor radon

DING Bowei, WU Yunyun, SONG Yanchao, SUN Haoran, LI Jialu, HOU Changsong

RADIATION PROTECTION. 2026, 46(5):  478-484.  doi:10.27045/j.1000-8187.202605012

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Radon is a major contributor to human exposure to natural radiation, and radon exhalation from building materials is an important contributor to indoor radon concentrations. Fired common brick is extensively used in residential buildings in rural areas in China and remains a predominant wall material. In this study, a total of 14 fired common brick samples were collected from 10 provinces in China. The ²²⁶Ra content of the samples was determined using a GC3018 low-background HPGe γ-spectrometer, while porosity was measured using a BSD-TD-K fully automated true density and open porosity analyzer. The radon exhalation rate and radon emanation fraction were measured using the activated carbon sealed chamber method. The radon diffusion length and diffusion coefficient were determined by controlling the thickness of the building material samples using an integrated system including a source chamber, diffusion window, accumulation chamber, and RAD7 radon detector. The mean ²²⁶Ra content of fired common brick was 48 ± 9 Bq/kg, and the mean porosity was 38%±3%. The mean surface radon exhalation rate was 0.03 ± 0.02 mBq·m^-2·s^-1, and the radon emanation fraction was 2.2%±1.1%. The mean radon diffusion length was 0.44±0.10 m, and the radon diffusion coefficient was (0.403±0.165)×10^-6 m²·s^-1. Based on the measured radon exhalation parameters, an indoor radon concentration prediction model was applied to estimate the indoor radon concentration attributable to radon exhalation from building materials. Indoor radon concentrations were also measured in the investigated rooms to quantitatively evaluate the contribution of building materials to indoor radon. The results showed that the average contribution of radon exhalation from building materials to the measured indoor radon concentration was 41%±9% across the six rooms. The contribution of radon exhalation from building materials was lower on the first floor than on the second floor, indicating that first-floor rooms were more strongly affected by radon originating from the underlying soil.

Design and operating condition simulation of a closed-loop radon progeny test system

YANG Yi, CHANG Xiang, ZHANG Fuguo, ZHANG Yanting, MA Tao, SHANG Jie

RADIATION PROTECTION. 2026, 46(5):  486-493.  doi:10.27045/j.1000-8187.202605013

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This study presents a closed-loop radon progeny test system for evaluating radon compensation performance and establishing a systematic method for controlling the test conditions. Steady-state and transient simulations were conducted to determine how key parameters affect the target operating conditions. A sequential three-variable control procedure was proposed. The aerosol particle concentration (C_p), filtration flow rate (Q), and radon concentration (C_Rn) were adjusted in this order. The procedure was used to determine control schemes and parameter settings for multiple target conditions. These conditions covered equilibrium factors (F) from 0.10~0.35, equilibrium equivalent concentrations (EEC) from 140 to 700 Bq·m^-3, and unattached fractions (f_p) from 15% to 50%. These ranges generally cover typical testing requirements and provide practical guidance for controlling radon compensation tests.

A preliminary investigation into integrated personal monitoring techniques for respirable dust and elevated radon exposure in mining operations

CAO Lei, DENG Jun, JI Fang

RADIATION PROTECTION. 2026, 46(5):  494-498.  doi:10.27045/j.1000-8187.202605014

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Objective An integrated monitoring technology and supporting equipment for personal exposure to respirable dust and high levels of radon were investigated, given the severe occupational hazards present in mine operations in China. Methods By analyzing and summarizing the technical requirements for personal exposure monitoring of respirable dust and high radon, suitable research approaches and key development points were identified. Results The BMRC curve-based separation sampling for respirable dust was achieved through a dual-layer filter technique. Radiation dose from radon and thoron progeny was quantified using CR39 solid-state nuclear track detectors, while a suction device combined with glass fiber filters was used for dust sampling. Conclusions The development of this equipment may enable simultaneous sampling and analysis of two major occupational hazards that contribute to an elevated risk of lung cancer and other associated cancers, and has laid important technical groundwork for examining the synergistic effects of occupational hazards to lung cancer.