分类： 核科学技术 >> 辐射防护技术 分类： 核科学技术 >> 核安全 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-04-02
摘要： 聚变堆贮存及释放的气态氚的量远高于现行的裂变堆，氚是聚变堆潜在放射性的重要来源。因此，为未来实现聚变堆的安全性及环境友好性，需要研究聚变堆气态氚排放对环境的影响。基于使用高斯模型预测气态氚释放后的大气弥散规律以及氚气（HT）的干沉积、土壤氧化以及氚化水（HTO）的再蒸发效应，计算了聚变堆1g的HT在短期释放情况下对周围环境的公众所造成辐射剂量。计算结果显示：在10m高度处释放的HT对排放点W方位500-3000m处的成人造成的吸入内照射剂量在0.38~0.10mSv之间，不同距离HTO的再蒸发效应所造成的剂量都是气态氚剂量的主要来源，沉降至土壤中的HT被氧化成HTO的比例及气象条件是决定气态氚剂量的关键参数。研究表明聚变堆HT释放所造成公众剂量要高于现行的裂变堆，在后续开展聚变堆的相关研究过程中，需要进一步关注其释放的气态氚对环境的辐射效应。
分类： 核科学技术 >> 辐射防护技术 提交时间： 2023-11-20
摘要： Objective: The increasing incidence of breast cancer among Chinese women has necessitated the utilization of breast X-ray screening, which carries radiation risk. This work aims to provide a dosimetry protocol for the Chinese female population, to replace the traditional standard that utilize simplified breast models, for the accurate estimation of patients mean glandular dose undergoing digital breast tomosynthesis (DBT).Approach: We have constructed the first set of Chinese female detailed breast models with their representative breast parameters. Considering the backscatter radiation and computational efficiency, we improved the combination of these models and the Chinese reference adult female whole-body voxel phantom. The image acquisition for four commercial DBT systems, which are widely employed in China, were simulated using the Monte Carlo method to obtain the normalized glandular dose coefficients of DBT (D_gN^DBT) and glandular depth dose (Dgdepz ) for different breast characteristics and X-ray spectra.Main results: We calculated a series of D_gN^DBT for breasts with different percentage mass glandularity (5%, 25%, 50%, 75%, and 100%) and compressed breast thicknesses (2cm, 3cm, 4cm, 5cm, 6cm, 7cm), at various tube potentials (25kV, 28kV, 30kV, 32kV, 35kV, and 49kV) and target/filter combinations (W/Rh, W/Al, Mo/Mo, Rh/Rh, Rh/Ag). The parameter dependence of breast characteristics and beam conditions on D_gN^DBT of detailed breast models were investigated. The D_gN^DBTresults were 14.6% - 51.0% lower than those of the traditional dosimetry standard in China. The difference inD_gN^DBT was mainly due to the decrease in the depth of the main energy deposition area caused by glandular distribution along the depth direction.Significance: The results obtained in this work could be employed for the improvement of breast dosimetry in China, and provide more detailed information about risk assessment undergoing DBT.
分类： 核科学技术 >> 辐射防护技术 提交时间： 2023-07-07
摘要： Environmental radon emanates from the exhalation and release of soil, rocks, and building materials. Environmental radon contamination tracing and radon pollution prevention and control require the measurement of the radon exhalation rate on media surfaces. Reliable measurements of the radon exhalation rate cannot be achieved without regular calibration of the measuring instrument with a high-performance reference device. In this study, a reference device for the calibration of radon exhalation rate measuring instruments was developed using a diffusion solid radon source with a high and stable radon emanation coefficient, an integrated diffusion component composed of a plasterboard and a high-density wooden board, an air pressure balance device, a radon accumulation chamber, and a support structure. The uniformity and stability of the reference device were evaluated using the activated carbon- spectrum and open-loop method, respectively, to measure the radon exhalation rate. The reference device achieved different radon exhalation rates by using different activities of diffusion solid radon sources. Nineteen measurement points were regularly selected on the radon exhalation surface of the reference device, and the uniformity of the radon exhalation rate exceeded 5%. The short-term stability of the reference device was better than 5% under different environmental conditions and was almost unaffected by the ambient air pressure, environmental temperature, and relative humidity.
分类： 核科学技术 >> 辐射防护技术 提交时间： 2023-06-06
摘要： The uncertainty of nuclide libraries in the analysis of the gamma spectra of low- and intermediate-level radioactive waste (LILW) using existing methods produces unstable results. To address this problem, a novel spectral analysis method is proposed in this study. In this method, overlapping peaks are located using a continuous wavelet transform. An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks. Combined with the adaptive sensitive nonlinear iterative peak, this method can effectively subtracts the background. Finally, a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library. Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152, a segmented gamma scanning experiment for a 200 L standard drum, and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides (Sb-125, Sb-124, and Cs-134) are conducted. The results of the experiments indicate that (1) the novel method and gamma vision (GV) with an accurate nuclide library have the same spectral analysis capability, and the peak area calculation error is less than 4%; (2) compared with the GV, the analysis results of the novel method are more stable; (3) the novel method can be applied to the activity measurement of LILW, and the error of the activity reconstruction at the equivalent radius is 2.4%; and (4) The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library. This novel method can improve the accuracy and precision of LILW measurements, provide key technical support for the reasonable disposal of LILW, and ensure the safety of humans and the environment.
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