[en] Background: Control rod drive mechanism (CRDM) is one of the important safety-related equipment for nuclear power plants. Purpose: The operating parameters of stepping movement, including lifting loads, step distance and step velocity, are all critical design targets. Methods: FEA and numerical simulation are used to analyze stepping movement separately. Results: The motion equations of the movable magnet in stepping movement are established by load analysis. Gravitation, magnetic force, fluid resistance and spring force are all in consideration in the load analysis. The operating parameters of stepping movement are given. Conclusions: The results, including time history curves of force, speed and etc, can positively used in the design of CRDM. (authors)

[en] Background: A core drop accident causes the core barrel and supporting structure to drop and impact on the bottom of the reactor vessel. Purpose: To ensure the scram functionality is maintained. Methods: The stress-strain curves applicable to the material are approximated by Ludwik's expression. Considering the core deadweight, buoyancy force and heat expansion, material train ratios for both cold and hot conditions are calculated. Results: Vessel impact load (8294482N in cold condition and 6064537N in hot condition) is determined, which remains within the vessel design specification limits. The calculated drop length (47.44 mm in cold condition and 27.63 mm in hot condition) is less than the fuel pin full-diameter engagement length, so the fuel assembly top nozzle will remain engaged during a core drop. Finally the compressive assemblies are evaluated, which would not buckle due to the core drop accident loads. Conclusions: A core drop will not affect the scram function. (authors)

[en] Background: For the intensity of high-enriched uranium's neutrons from fission is weak, the active detection method is commonly adopted. Purpose: The quality attribute of uranium components is analysed. Methods: According to the theory of neutron source-driven noise analysis method and mass measurement problem of uranium material or uranium component, Monte Carlo simulation is used to study the mass measurement of metal uranium sphere components with the same geometry and enrichment and the different masses. The time-correlation coincidence count distributions to different uranium components are obtained. Results: The source-driven time correlation coincidence measurements can provide quantities, time-dependent coincidence distributions between two detectors, which can be related to the mass of uranium components. Conclusions: By studying on the sample (radius: 4.67 cm, mass: 8 kg), it realized mass measurement to metal uranium sphere components with different masses. (authors)

[en] Background: Accurate nuclear data are needed for the development of molten salt reactors which use thorium as nuclear fuel. Purpose: We attempt to get an optimum set of optical potential parameters for "2"3"2Th with the incident neutron energy from 0.1 MeV to 20 MeV Methods: APMN code which based on optical theory and Hauser-Feshbach theory with width fluctuation correction was used. Steepest descent method was adopted when the code seeks the optimum optical parameters automatically. Results: The comparison between the experimental data and the calculation results before and after adjusting the optical parameters shows that the calculation results after adjusting are in better agreement with the experimental data. This set of parameters could be used for nuclear data calculation. Conclusions: Based on the results it could provide a believable set of optical parameters for the neutron data evaluation. (authors)

[en] Background: The twist of bent crystal is a common problem of sagittal focusing monochromators. In Shanghai Synchrotron Radiation Facility (SSRF), one of monochromators has an unfocused beam profile because of crystal twist. Purpose: In order to amend the twist problem and get theoretical understanding for further design optimization, a study on the mechanism of crystal twist has been developed. Methods: Finite Element Analysis (FEA) models considering anisotropic effect of crystal were constructed to study some common factors, i.e. crystal orientation, clamping method, stiffening ribs and asymmetric clamping on the bent crystal profile. Results: The simulation result shows that among those factors, asymmetric clamping is the main reason causing the crystal twist while crystal orientation is also important. Clamping method is a factor that restricts the asymmetric clamping to a certain scale. Conclusions: For optimizing the system, asymmetric clamping should be controlled and crystal should be cut in a particular orientation. (authors)

[en] Background: Ramie fiber is a kind of natural polymer material with abundant resources and low price, which has been widely applied in textile. Ramie textiles possess many good qualities, such as air permeability, sweat conductivity and antibacterial ability, but the high crystallinity of ramie fiber gives rise to bad spinning property, small extensibility and low chromaticity which restrict its further application. Purpose: In order to reduce the crystallinity of ramie fiber, the electron beam was directly utilized to irradiate ramie fiber. Methods: Ramie fiber was irradiated by electrons with the irradiation doses from O to 2 000 kGy, and the irradiated ramie fiber was characterized by XRD and FT-IR. The crystallinity and the crystallinity index of ramie fiber were analyzed, and the irradiation effect was discussed. Results: The crystallinity and the crystallinity index of ramie fiber decrease with the increasing of irradiation doses and the number of -C=O increases with the increasing of irradiation doses. Conclusions: The variation behavior of the crystallinity and the crystallinity index of ramie fiber with electron irradiation dose ranging from 0 to 2000 kGy is got. It is shown that the crystallinity and the crystallinity index of ramie fiber may be effectively reduced by using electron beams irradiation, but also the required crystallinity of ramie fiber in its application can be achieved by controlling the electron beams irradiation doses. (authors)

[en] Background: Studies of the radiation effects on the floating-gate flash memory have been mainly focused on functionality measurement. Purpose: According to the present situation, flash memory was irradiated and annealed by "6"0Co γ rays, and the TID failure mechanism of the device was analyzed. Methods: The function parameters including DC and AC were measured using a large scale integrated circuit testing system. The range of radiation-sensitive parameters was extended using the Verigy 93000 instrument and the Shmoo test. Results: The results showed that the maximum operating frequency was radiation-sensitive parameter which has a significant change in radiation and annealing. Conclusions: Under strong electric field, due to the accumulation of oxide trapped charge and interface trap charge, the performance of charge pump circuit was deteriorated and the function of device was failed. Annealing characteristics indicated that the oxide trapped charge accounts for a major role. (authors)

[en] Background: Due to the effect of near-field artifacts, the clearity of reconstructed image obtained by coded aperture imaging was decreased. Purpose: In order to explore a way to eliminate the effect and to enhance the image quality, a Geant4 simulation was performed in this work. Methods: On the basis of the principles of near-field artifact generation and elimination, coded aperture imaging of a 300 keV gamma source was simulated by Geant4 at near-field conditions with a mosaicked MURA (19×19) mask by single- and double-mode measurements, respectively. Results: The near-field artifacts were apparent in the images obtained by single-mode measurement, while they were almost eliminated by double-mode measurement. Similar results showed up in the imaging experiments with a commercial gamma camera. Conclusions: The near-field artifacts would be inhibited or even eliminated by the double-mode measurement otherwise from the conventional single-mode measurement, resulting with an enhanced signal-to-noise ratio (SNR) of reconstructed images. (authors)

[en] Background: Location nuclear imaging systems have been used in many fields, such as astronomical observation, radioactive source monitoring, nuclear development, biomedicine, etc. Purpose: It puts forward much higher requirements of monitoring and control of safety of nuclear facilities and radioactive sources. In this paper, a new portable nuclear imaging system is designed, which can be used in far field imaging. Methods: It uses high resolution detector which consists of LaBr_3 crystal and H8500 position sensitive photomultiplier to meet the design requirements of high resolution. In order to acquire the higher radiation collection efficiency, we choose modified uniformly redundant arrays (MURA) as system collimator. It uses the maximum likelihood-expectation maximization (MLEM) algorithms in reconstruction procedure. Results: The test results show that the imaging system can image the far field radioactive source clearly. The field-of-view of our system can achieve the design goal: ±10°-±20°, and its resolution can be variable among 0.923°-2.038°. Conclusions: It can meet the design requirements of resolution and FOV very well. This radiation imaging system can achieve miniaturization and portability radiation imaging robot which is suited for the long-range control. (authors)

[en] Background: Elastic scattering is induced by weakly unstable nuclei. Generally, a good angular resolution for angular distribution of elastic scattering is needed. The silicon strip detector is often used for this kind of experiment. Purpose: In order to use silicon strip detector to study the elastic scattering of weakly unbound nuclei, it is important to get the information of its position calibration. It is well known that the elastic scattering of stable nuclei has a good angular distribution and many experimental data have been obtained. Methods: So the scattering of stable nuclei can be used to calibrate the position information of silicon strip detector. In this experiment, the positions of silicon strip detectors are calibrated using 101 MeV and 59 MeV "1"6O scattering on the "1"9"7Au target. Results: The quasi-elastic peaks can be observed in the silicon strip detectors and the counts of quasi-elastic "1"6O can be obtained. The solid angles of the silicon strip detectors are calibrated by using alpha source which has three alpha energy values. The angular distribution of quasi-elastic scattering of "1"6O+"1"9"7Au is obtained at these two energy values. Conclusions: The experimental data of angular distribution are reasonable and fit for the principle of angular distribution of elastic scattering. It is concluded that in the experiment these silicon strip detectors can accurately give the position information and can be used for the elastic scattering experiment. (authors)