一级设备的应力与应变分析研究

一级设备在核设备中非常重要,在该设备的设计和调试的过程中需要对其进行应力与应变分析,从而确保其安全性。对一级设备的应力与应变分析有两种方法,理论方法和实验方法。通过理论方法,可以得到一级设备在各种工况下的应力与应变状况,从而为设备的设计提供依据;通过实验方法,可以验证理论方法的准确性,并为设备的安全评定提供依据。中国实验快堆(CEFR)主容器属于一级设备,本文结合CEFR主容器的应力与应变分析研究,根据AMSE规范,描述了核安全一级设备的应力与应变分析的理论方法,同时也介绍了测量核安全一级设备的应力与应变的实验方法。     

XRD investigation of the strain/stress state of ion-irradiated crystals

In this work, it is demonstrated that XRD is a powerful technique for the study of ion-irradiated materials. For this purpose, XRD experiments have been performed under different configurations on a 〈1 0 0〉-oriented yttria-stabilized zirconia single crystal implanted with 300 keV caesium-ions at 3 × 10¹⁴ cm⁻². Initially, it is demonstrated that the depth strain profile can be determined from the refinement of a symmetric θ-2θ scan. Moreover, in order to explore the whole XRD data, a model that describes the strain/stress state of the damaged layer is proposed. This model takes into account the elastic response of the bulk material (substrate) underneath the irradiated layer. The measured elastic strain is then the sum of a free strain due to the formation of radiation-induced defects and of an additional strain arising from the substrate elastic reaction. Application of this model allowed the calculation of the different strain contributions and the stress experienced by the irradiated layer. It is shown that these parameters may reach large values (respectively 0.7% and −1.9 GPa) despite the low radiation damage level.     

Phase identification by a novel needle-contact capacitance probe in gas-liquid two-phase flows

In this paper,we propose a novel probe to identify phases in any two-phase flows where one phase is conductive and the other nonconductive.We can further obtain many parameters such as void fraction,bubble velocity,and interfacial area concentration.Compared with the traditional probe,the novel probe has unique advantages that it is less dependent on water conductance or distance between the electrodes,and that the amplitude is bigger between high and low levels.Theoretical analyses showed that the measurement error became higher when water conductance decreases or distance increases,which is consistent with the theoretical analyses.Experimental results showed that the output signal kept constant with salt content of 0-5% and electrode distance of 0-30 mm in tap water.The level difference was up to 6.4 V,resulting in identifying two phases easily.Time traces of phase identification were completely consistent with the flow structures.     

80 MeV/u C-12离子诱变选育PHB高产菌株

用80MeV/u12C6+离子对一株积累聚β-羟基丁酸酯(PHB)的芽孢杆菌(BacillusP-9)进行诱变选育,最终获得PHB高产株菌G15,其PHB产量达2.93g/L,与出发菌株相比较,PHB积累量提高了1.5倍。研究结果表明,本试验辐照最佳剂量为15Gy。重离子辐照诱变育种效果显著,具有广阔的发展应用前景。     

Isolation and identification of bacteria able to form biofilms from deep subsurface environments

Migration radionuclides in an underground environment are one of the major concerns in the safety assessment of a geological repository. Biofilms can have an impact on the transport of radionuclides in several ways: (1) by acting as a barrier to radionuclide sorption onto geological surfaces, or (2) by providing a sorption site for radionuclides, or (3) by trapping many things, including radionuclides. Little is known about bacterial effects on the biofilm formation deep underground. In this study, we isolated bacterial strains from deep groundwater and evaluated the biofilm formation abilities of these strains by crystal violet assay. Bacterial strains were isolated from ground-water collected at –140 m in the 07-V140-M01 borehole at the Horonobe Underground Research Center, Japan. The crystal violet assay showed that 98% of the isolated strains had biofilm formation abilities under tested conditions. This result suggested that biofilm formation must not be neglected in the study of migration radionuclides in nuclear waste repositories. The isolated strains produced differential amounts of biofilm, although they were identified as the same Pseudomonas species, suggesting that biofilm formation abilities varied at different strain levels. These results support the conclusion that the assessment of biofilm impact on the transport of radionuclides in a geological repository must consider the variation in biofilm formation as a function of strain level.     

Depth dependent lattice disorder and strain in Mn-implanted and post-annealed InAs thin films

The lattice order degree and the strain in as-grown, Mn-implanted and post-implanted annealed InAs thin films were investigated with depth resolution by means of Rutherford backscattering spectrometry in channeling conditions (RBS/C). Three main crystallographic axes were analyzed for both In and As sublattices. The behaviour of the induced defects was evaluated in two regions with different native defects: the interface and the surface. The results show that Mn implantation and post-implantation annealing are anisotropic processes, affecting in a different way the In and As sublattices. The mechanisms influencing the enhancement and deterioration of the crystal quality during the implantation are discussed in relation to the as-grown defects and the segregation of the elements.     

A review of creep-fatigue life prediction methods: identification and extrapolation to long term and low strain cyclic loading

Eight creep-fatigue interaction models are identified on a set of LCF experimental data.The material is 316 L type stainless steel, the temperature is 600°C. The general agreement between tests and predictions is good in the experimental range.Tentative extrapolations are made toward low strain and long dwell.Opposite trends are then pointed out on stress dependent and strain range dependent models.The final results are still encouraging and general rules are given concerning the long term life prediction.     

A novel approach for feature extraction from a gamma-ray energy spectrum based on image descriptor transferring for radionuclide identification

Nuclear Science and Techniques - This study proposes a ladder gradient method for neutron and gamma-ray discrimination. The proposed method exhibited state-of-the-art performance with low time...