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Real-time detection of X/gamma radiation dose rates holds particular significance in nuclear science research. In this study, we developed a portable X/gamma-ray survey meter for large-scale distributed real-time monitoring of ambient dose equivalent rates in the surrounding environment. This innovative device uses a silicon photomultiplier coupled with a CsI(Tl) scintillator and can connect to an Internet of Things network. Additionally, it facilitates a wide spectrum of dose rate measurements by modifying the frequency of a pulse-frequency modulation-type DC-DC power supply mode. The energy response of the survey meter, which is improved through Geant4 simulations and a multi-comparator design, ranges from 48 keV to 1.3 MeV, encompassing various common protection level applications. It effectively measures gamma radiation dose rates ranging between 0.1 mSvh-1 and 100 mSvh-1 for 60Co. Temperature compensation of the detector was achieved through a series of experiments. The meter exhibits a deviation of -25 % to +25 % at temperatures between -40°C and +40°C.

In order to provide technical support and evaluation basis for the development of remediation technology of radioactive contaminated sites and the site selection, design and construction of radioactive waste disposal facilities, the reliable longterm risk assessment for potential nuclear waste repositories and decommissioning of nuclear facilities requires detailed knowledge on the migration behavior of radionuclides in natural, it is necessary to understand the reaction mechanism of radionuclides in the complex geological environment of aquifers. The batch experiments and dynamic undisturbed soil column migration experiments of 90Sr, 137Cs, 238Pu and 241Am were carried out under saturated steadystate flow conditions in fine sand column, a theoretical model of nuclide migration in soil and groundwater environment was constructed, and the irreversible adsorption reaction mechanism of the microinterface was studied through static adsorptiondesorption and dynamic undisturbed soil column migration experiments, and the environmental migration flux of nuclides was calculated. The static adsorption and desorption experiments adopt batch method, and the test medium is fine sand with saturated porous media from an arid mining area in Gansu Province. The fine sand and soil samples according to the solidliquid ratio of 1 g∶9 mL were added into the centrifuge tube, and the nuclide activity concentration was measured after adsorption and desorption equilibriums to obtain the adsorption and desorption isotherms. Dynamic column method used undisturbed soil to ensure the continuity of soil sample medium, original connectivity of void channels and authenticity of stratum. The design and advantages of dynamic column method is to take into account various physical, chemical and biogeochemical reaction processes and complex migration paths of tracers during migration in soil. And the dynamic migration and transformation process of 90Sr, 137Cs, 238Pu and 241Am were studied in saturated porous media with anisotropic timevarying hydrologic characteristics by artificial spraying under controlled laboratory initial conditions and boundary conditions. The results show that the absorption isotherm of 90Sr doesn’t coincide with its desorption isotherm, with an angle at 3238° between them. According to the metastable equilibrium adsorption theory, 90Sr has an irreversible adsorptiondesorption process, and ions exchange is the dominated action for its adsorption. As for 137Cs, 238Pu and 241Am, reversible adsorptiondesorption process are shown, and their adsorptions are mainly attributed to surface complexation. Equilibrium adsorption theory and nonequilibrium adsorption model can be used to describe the migration peak phenomenon of different nuclides in the dynamic soil column experiment, which can be effectively integrated into chemical nonequilibrium and physical nonequilibrium processes. Considering the superposition of convectiondispersion and chemical reaction on solute migration, solute migration equations were established based on the reaction rate equation, and the calculated and measured concentration distribution curves were fitted reasonably to obtain a reaction model that can accurately describe and predict nuclide migration. As for 90Sr, the nonequilibrium adsorption model by transport column was taken into account the firstorder rate coefficient (β) between the dissolved phase and the adsorbed phase. The calculated concentration distribution curve is good agreement with the measured concentration. The fitting results show that the distribution coefficient (Kd) and β of 90Sr in the fine sand aquifer are 085 mL/g and 016 h-1, respectively, in terms of 137Cs, 238Pu and 241Am, the radionuclides concentration distribution curves in equilibrium adsorption and nonequilibrium models are in good agreement with the measured values. Meanwhile the calculated results by two different adsorption models are almost similar, and the Kd are 49×102, 21×104, and 6.0×103 mL/g for 137Cs, 238Pu and 241Am. It shows that the stronger adsorption capacities of the nuclides have the faster rate of the adsorption-desorption in the soil, meanwhile the shorter time for the system reaction equilibrium. At this time, the fitting results of the equilibrium adsorption mode and the nonequilibrium adsorption mode are closer to each other.

Objective To explore the application of team-based learning(TBL) combined with case-based learning (CBL) in training program of thyroid surgery on medical intern. Methods A prospective study was conducted in 94 interns with training program from November 2020 to June 2021 in thyroid surgery, Ruijin Hospital. The interns were grouped chronologically. Forty-six interns from November 2020 to February 2021 were included into control group and 48 interns from March 2021 to June 2021 into study group. Interns in control group were given traditional training and interns in study group with TBL with CBL training. Basic theory and knowledge, basic operative skill and ability of managing crisis were evaluated and compared between two groups. Results The basic theory and knowledge in study group were significantly better than that in control group (t=12.610, P0.05) and ability of managing crisis (t=1.313, P>0.05) between two groups. As for crisis management abi-lity, the team work ability (t=3.610, P

BackgroundCompton imaging technology is a new radiation hotspot location technology that does not require collimation and has a wide field of view, high efficiency, and broad application prospects. With the development of nuclear technology, Compton cameras with the above-mentioned advantages have a wide range of applications not only in the nuclear industry but also in the field of nuclear medicine, hence recently become a popular research field worldwide.PurposeThis study aims to develop a double-layer separated Compton camera for far-field imaging of specific radiation scenes in nuclear facilities.MethodsFirst of all, two pixel-type cadmium zinc telluride (CZT) detectors and an application-specific integrated circuit (ASIC)-based readout electronics system were adopted for the development of a double-layer separated Compton camera. A list-mode maximum likelihood expectation maximization (LM-MLEM) image reconstruction algorithm was implemented in the host computer software. Then, 137Cs point source was used for experimental test of imaging performance of the system, and the parameters affecting the imaging performance, such as the detector layer spacing and area of the absorption layer, were optimized. Finally, far-field three-dimensional imaging of the radiation source was performed by moving the measuring position of the detector.ResultsThe test results show that the energy resolution of the CZT detectors is approximately 3% (FWHM@662 keV), which can determine the location of the point source at a distance of 5 m, and the angular resolution for θ and φ directions of the optimized system is approximately 10°.ConclusionsDouble-layer separated Compton camera of this study has advantages of adjustable structure, low detector cost, relatively simple readout electronics, and wide imaging field of view. The angular resolution of this double-layer separated Compton camera can be improved by proper adjustment of the imaging influence parameters (such as layer spacing and the area of the absorption layer).

Nanocarbon materials (carbon nanotubes, graphene, graphene oxide, reduced graphene oxide, etc.) are considered the ideal toughening phase of ceramic matrix composites because of their unique structures and excellent properties. The strengthening and toughening effect of nanocarbon is attributed to several factors, such as their dispersibility in the matrix, interfacial bonding state with the matrix, and structural alteration. In this paper, the development state of nanocarbon-toughened ceramic matrix composites is reviewed based on the preparation methods and basic properties of nanocarbon-reinforced ceramic matrix composites. The assessment is implemented in terms of the influence of the interface bonding condition on the basic properties of ceramic matrix composites and the methods used to improve the interface bonding. Furthermore, the strengthening and toughening mechanisms of nanocarbon-toughened ceramic matrix composites are considered. Moreover, the key problems and perspectives of research work relating to nanocarbon-toughened ceramic matrix composites are highlighted.