Subjects: Nuclear Science and Technology >> Radiation Protection Technology Subjects: Nuclear Science and Technology >> Nuclear Safety Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-04-02
Abstract： he amount of gaseous tritium stored and released in fusion reactor is higher than which in current fission reactors, so that tritium is an important source of potential radioactivity in fusion reactor. Therefore, in order to achieve the safety and environmental friendliness of fusion reactor in the future, it is necessary to study the environmental impact of gas tritium emission from fusion reactor. Based on the Gauss model to predict the atmospheric dispersion of gaseous tritium release and the dry deposition of tritium gas (HT), soil oxidation and reevaporation of HTO, the radiation dose of 1g HT released from fusion reactor to the public in the surrounding environment was calculated. The calculation results show that: The effective dose of inhalation internal irradiation of HT released at 10m height for adults at 500-3000m W of the release point ranges from 0.38mSv to 0.1mSv The dose caused by the reevaporation effect of HTO at different distances is the main source of the dose of gaseous tritium. The proportion of the HT deposited to soil being oxidized to HTO and the atmosphere condition are the key parameter determining the effective dose of the tritium gas. The study shows that the effective dose of HT released from fusion reactor to public is higher than which released from fission reactor,so that further attention to the environmental impact of the tritium is needed in the research on the fusion reactor subsequently.
Peer Review Status:
Awaiting Review
Subjects: Nuclear Science and Technology >> Radiation Protection Technology submitted time 2023-11-20
Abstract： 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^DBT results were 14.6% - 51.0% lower than those of the traditional dosimetry standard in China. The difference in D_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.
Subjects: Nuclear Science and Technology >> Radiation Protection Technology submitted time 2023-07-07
Abstract： 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-γ 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.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Radiation Protection Technology submitted time 2023-06-06
Abstract： 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.
Peer Review Status:Awaiting Review
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