[en] We present a possible hadronic explanation of the high-energy γ-ray emission from two very high-energy (VHE) sources, HESS J1745-303 (A) and HESS J1714-385, which coincide with supernova remnants (SNRs) interacting with dense molecular clouds (MCs). We calculate the proton spectra and the corresponding hadronic γ-ray spectra for different Mach numbers of the shock wave in a semi-analytical model for the non-linear shock acceleration process, then apply the model to the two newly discovered TeV sources. The results show that the γ-ray spectra for the two sources with energies above 100 MeV detected by HESS and EGRET can be reproduced with low Mach numbers about 2.5. Thus the high-energy γ-ray origin for each one of the two sources can be interpreted as proton-proton (p-p) collisions in MCs overtaken by an SNR shock wave. (authors)

[en] We present a possible hadronic explanation of the high-energy γ-ray emission from two very high-energy (VHE)sources, HESS J1745-303 (A) and HESS J1714-385, which coincide with supernova remnants (SNRs) interacting with dense molecular clouds (MCs). We calculate the proton spectra and the corresponding hadronic γ-ray spectra for different Mach numbers of the shock wave in a semi-analytical model for the non-linear shock acceleration process, then apply the model to the two newly discovered TeV sources. The results show that the γ-ray spectra for the two sources with energies above 100 MeV detected by HESS and EGRET can be reproduced with low Mach numbers about 2.5. Thus the high-energy γ-ray origin for each one of the two sources can be interpreted as proton-proton (p-p) collisions in MCs overtaken by an SNR shock wave. (authors)

[en] Operation safety surveillance and operation experience feedback are two effective measures to ensure and improve nuclear safety, the basis of which is nuclear power plant events analysis. A substantial number of events occur every year in nuclear power plant, thus screening for safety important and typical events which are valuable for experience feedback is important. Combining with risk insights, a new method for quick screening of nuclear power plant events is proposed on the basis of present event analysis method. A risk assessment tool to support the new method, i. e. significance determination process (SDP), is introduced in details. An example event is analyzed to obtain ΔCDF using SDP software and PSA model respectively, to verify the capability of SDP. The quantification results show agreement between ΔCDF of SDP and PSA models. It is concluded that the quantification results of SDP are capable for applications it supports. Limitations of present SDP software are pointed out and its future extension and potential applications are discussed. (authors)

[en] To analyze the reason of difference between the departure from nucleate boling ratio (DNBR) indicated by the upper-level software and lower-level software of the in-core instrumentation system (ICIS) at a certain water-cooled water-moderated power reactor (WWER) unit under its first thermal test during raising power, an investigation was made on the critical heat flux (CHF) correlations adopted in the reactor thermal and hydraulic design and accident analysis of WWER unit. On the above basis, the reason behind the difference was found to be the use of different CHF correlations by the upper-level software and the lower-level software of ICIS through the simulation of thermal tests under 50%, 75% and 90% power level using WWER accident analysis code DINAMIKA-97, calculation of DNBRs and comparison with the ones measured in thermal-hydraulic tests. DNBR under 100% power level was predicted, which coincided with the measured DNBR very well and proved the correctness of the guess further. It is suggested that the CHF correlations adopted by the upper-level software and the lower-level software shall be modified to the same conservative CHF correlation to get a conservative DNBR. (authors)

[en] Analogue dementia model of rats was produced by electrolytic lesion of brain. α-adrenergic receptors were assayed by radioligand binding assay (RRBA). It was found that B_max of α1 receptors was decreased obviously in cerebral cortex, hippocampus and cerebellum of analogue dementia rats and was raised obviously by Heart-and Kidney-Benefiting Chinese Herbs as well as by Hydergin. The electrolytic lesion did not change the activity of MAO-B in model rat brains. Neither Heart-and Kidney-Benefiting Chinese Herb Medicines nor Hydergin showed marked effect on brain MAO-B activity of the model rats

[en] Highlights: • Simulations were performed for turbulent bubbly flows in PWR subchannel geometry. • Liquid turbulence is fully resolved by direct numerical simulation approach. • Bubble behavior is captured using level-set interface tracking method. • Bubble tracking method collects the flow statistics at individual bubble level. - Abstract: Bubbly flow is a common natural phenomenon and a challenging engineering problem yet to be fully understood. More insights from either experiments or numerical simulations are desired to better model and predict the bubbly flow behavior. Direct numerical simulation (DNS) has been gaining renewed interests as an attractive approach towards the accurate modeling of two-phase turbulent flows. Though DNS is computationally expensive, it can provide highly reliable data for model development along with experiments. The ever-growing computing power is also allowing us to study flows of increasingly high Reynolds numbers. However, the conventional simulation and analysis methods are becoming inadequate when dealing with such ‘big data’ generated from large-scale DNS. This paper presents our recent effort in developing the advanced analysis framework for two-phase bubbly flow DNS. It will show how one can take advantage of the ‘big data’ and translate it into in-depth insights. Specifically, a novel bubble tracking method has been developed, which can collect detailed two-phase flow information at the individual bubble level. Due to the importance of subcooled boiling phenomenon in pressurized water reactors (PWR), the bubbly flow is simulated within a PWR subchannel geometry with the bubble tracking capability. It has been demonstrated that bubble tracking method significantly improves the data extraction efficiency for level-set based interface tracking simulations. Statistical analysis was introduced to post-process the recorded data to study the dependencies of bubble behavior with local flow dynamics.

[en] Steam generator tube rupture (SGTR) accident is a significant design basis accident which shall be analyzed in PWR nuclear power plant safety analysis reports. Thermo-hydraulic analysis of SGTR accident for licensing has been done using a specific code entitled LOFTTR2. To validate the applicability of RELAP5 for AP1000 SGTR accident, a RELAP5 model for AP1000 is established and used to assess this accident. Results show that both the accident progression and the doses result of RELAP5 calculation correspond well with that in Safety Analysis Report. Thus, RELAP5 and RELAP5 model of AP1000 can apply to other SGTR type analysis. (authors)

[en] ³H-QNB and ³H-GABA were used as radioactive ligand for M-and GABA receptors respectively. M-and GABA receptors were assayed by radioligand binding assay (RBA) in cerebral cortex, hippocampus and cerebellum of analogue dementia rats. It was found that R_t of M receptor was decreased in cerebral cortex and hippocampus and R_t of GABA receptor was decreased in cerebellum of analogue dementia rats. The dissociation constant (K_D) of M-receptor was decreased significantly in cerebral cortex and K_D value of (GABA) receptor was decreased in cerebellum of analogue dementia rats. The decreased R_t of M-and GABA receptor in brain tissue of analogue dementia rats was raised by Heart- and Kidney-Benefiting Chinese Herbs as well as hydergin

[en] The source HESS J1813-178 was detected in a survey of the inner Galaxy in TeV γ-rays, and a composite supernova remnant (SNR) G12.8-0.0 was identified in the radio band to be associated with it. The pulsar wind nebula (PWN) embedded in the SNR is powered by an energetic pulsar PSR J1813-1749, which was recently discovered. Whether the TeV γ-rays originate from the SNR shell or the PWN is currently uncertain. We theoretically investigate the multiwavelength nonthermal radiation from the composite SNR G12.8-0.0. The emission from the particles accelerated in the SNR shell is calculated by applying a semianalytical method to the nonlinear diffusive shock acceleration mechanism. In the model, the magnetic field is self-generated via resonant streaming instability, and the dynamical reaction of the field on the shock is taken into account. Based on a model which couples the dynamical and radiative evolution of a PWN in a non-radiative SNR, the dynamics and the multiband emission of the PWN are investigated. The particles are injected with the spectrum of a relativistic Maxwellian plus a power-law high-energy tail with an index of -2.5. Our results indicate that the radio emission from the shell can be reproduced well as synchrotron radiation of the electrons accelerated by the SNR shock; with an interstellar medium number density of 1.4 cm^-3 for the remnant, the γ-ray emission from the SNR shell is insignificant and the observed X-rays and very high energy (VHE) γ-rays from the source are consistent with the emission produced by electrons/positrons injected in the PWN via synchrotron radiation and inverse Compton scattering, respectively; the resulting γ-ray flux for the shell is comparable to the detected one, only with a relatively larger density of about 2.8 cm^-3. The VHE γ-rays of HESS J1813-178 can be naturally explained to mainly originate from the nebula, although the contribution of the SNR shell becomes significant with a denser ambient medium.

[en] In Light Water Reactor (LWR) cores, the nuclear fuel rods are arranged together as rod bundles in a triangular or square pattern. The fuel rod bundles are supported by the spacer grids with mixing vanes. An understanding of spacer grid and mixing vanes effect is important since it has a direct impact on the turbulence structure in the flow and the heat removal efficiency from the fuel rod surface. Although a considerable amount of literature has been published on the experimental investigation of spacer grid and mixing vanes effect, the measurements were mainly focused on single-phase flow. The influence of spacer grid and mixing vanes on two-phase flow is yet to be fully understood. Some preliminary research efforts have been invested in nuclear community. For example, Wheeler et al. experimentally studied the effects of spacer grid in air-water two-phase flow. Although mixing vanes are not considered, they presented interesting results of time-averaged two-phase flow quantities at upstream and downstream locations of the spacer grid. Over the past decades, the rapid development of High-Performance Computing (HPC) is allowing for the increasingly larger-scale high-fidelity simulations. Thanks to this favorable historical trend, Direct Numerical Simulation (DNS), integrated with Interface Tracking Methods (ITM), has been emerging as a valuable tool to complement and expand our ability to understand the two-phase flow phenomenon. Meanwhile, in order to make best use of the large-scale two-phase flow simulations, advanced data analysis techniques are being developed, as they enable the extraction of detailed parameters about individual bubble behavior. The level set ITM is utilized in our DNS flow solver, which makes use of a signed distance field. The gas-liquid interface is modeled by the zero level set. The level set method can be readily used to distinguish different phases based on the sign of corresponding level set value (e.g. the sign is positive in the liquid phase while negative in the gas phase.). However, the traditional level set approach is not able to collect calculated values and associate with specific bubbles when multiple (even thousands of) bubbles present in the simulations of two-phase flow. This drawback hinders the collection of useful bubble information, which can give us valuable insights about bubbly flows. For example, how the different local fluid conditions could affect bubble interfacial forces, bubble deformation level, and eventually the bubble distribution throughout the whole domain. A bubble tracking methodology has been developed to address the drawbacks and improve the data collection efficiency of level set based two-phase flow simulations. In the present work, a single Pressurized Water Reactor (PWR) subchannel with reduced size spacer grid and mixing vanes is chosen as the computational domain. The springs and dimples of the spacer grid are not represented for simplicity in the present investigation. The bubble tracking methodology is applied to the simulations of two-phase bubbly flow through spacer grid and mixing vanes region. In the intended simulation, the liquid turbulence will be fully resolved by DNS while the two-phase behaviors are captured by level set ITM. Bubble tracking data are to be processed to investigate the spacer grid and mixing vanes effect on two-phase bubbly flow. (authors)