[en] This paper introduces some designs of Gamma-camera image data acquisition system, which has been developed by Department of Engineering Physics of Qinghua University in recent years

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No abstract available

No abstract available

[en] The author introduced some front-end electronic circuit designs that can improve the counting-rate performance of scintillation ECT system, including: delay-line pulse-clipping method, dynamic integration method and pile-up prevention method. Finally, the comparison of their performance was presented

[en] A multiscale methodology was developed to predict the evolution of thermal conductivity of polycrystalline fuel under irradiation. In the mesoscale level, phase field model was used to predict the evolution of gas bubble microstructure. Generation of gas atoms and vacancies were taken into consideration. In the macroscopic scale, a statistical continuum mechanics model was applied to predict the anisotropic thermal conductivity evolution during irradiation. Microstructure predicted by phase field model was fed into statistical continuum mechanics model to predict properties and behavior. Influence of irradiation intensity, exposition time and morphology were investigated. This approach provides a deep understanding on microstructure evolution and property prediction from a basic scientific viewpoint.

[en] Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at grain boundaries for given grain boundary properties. More validation of the model capability in polycrystalline is underway.

[en] Introduced a new-style computer interface for a γ-camera. The interface took the advantages of IBM PC/AT, such as, large memory size, high speed, 7 DMA channels and available of 16-bit data transfer. It does not need any extra buffer memory and operates the inter memory of PC directly, So it is low cost. Also, it is high capability and can collect all mode data from γ-Camera

[en] The author presents some new detector technology for nuclear medicine that will be very important and popular in the 21st century, including: Scintillator LSO, Avalanche Photodiode (APD), multi-channel PMT (MC-PMT), position sensitive PMT(PSPMT), semiconductor, etc

[en] The author presents some methods to reduce the unusable areas at the edges of modular small-plate NaI(Tl) crystals that tare used in a cylindrical SPECT system. Generally the unusable area is about half the PMT's width. In authors' approach, the PMT at the edge is shared by two adjacent modules; and two grooves parallel to the edge, one on the entrance surface, the other on the exit surface were cut on crystal. Using the centroid algorithm to calculate the position, the authors found the intrinsic resolution could be reduced to 5 mm