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Because the elastic scattering cross sections of medium-mass nuclides have very strong elastic scattering resonance phenomenon in the fast neutron region, which will lead to the self-shielding effect of energy scale and make distortions of the neutron flux distribution to zigzagging. In order to accurately describe the distribution of neutron flux in the energy scale, the deterministic one-step method needs to divide a large number of energy intervals for description, and the number of energy groups is generally thousands. Deterministic one-step transport calculation has large memory and low computational efficiency with thousands of groups. In the traditional calculation of the whole-core non-uniform transport calculation for the thousands of groups, the section generation software was mainly used to prepare the self-shielding cross section by using the ultra-fine groups, and then the broad-group cross section was prepared offline by the transport calculation of the equivalent model of cells or components. Finally, the deterministic one-step program was used to calculate the whole-core non-uniform transport. The broad-group cross sections prepared off-line cannot reflect the characteristics of materials of different reactor locations and bring the approximations. In order to solve the problem that the thousand-group energy structure of fast reactors leads to the high computational cost of the deterministic one-step method, an online energy group condensation method with fine group energy spectrum based on SHARK was developed. For the fuel cells of fast reactors, it can keep the composition of fuel and other materials unchanged and search the radius of the fuel to make the escape cross section conserved. It has the capability of online equivalent model establishment, online calculation of fine group energy spectrum and broad group cross sections condensation. For non-fuel cells, the broad group cross section was condensed using the fine group energy spectrum calculated by the one-dimensionalal constant volume model of practical problems. Based on the MOX1000 material of the benchmark for neutronic analysis of sodium-cooled fast reactor cores, a two-dimensional 5×5 rectangular single-assembly problem and a two-dimensional 3×3 multi-assembly problem were constructed and calculated. The numerical results show that compared with the calculation results of the group in 1 968, the acceleration ratio of the online energy group condensation method in the two-dimensional 5×5 rectangular single-assembly problem is 8 to 18 and that in the two-dimensional 3×3 multi-assembly problem is 12 to 17, which can significantly improve the calculation efficiency. In terms of calculation accuracy, the relative deviation of pin power distribution is less than 1%, and the maximum deviation of eigenvalue is about 360 pcm. It is of great significance to deterministic one-step method for fast reactor transport calculation.

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In this study, two kinds of shark repellents, chemical shark repellent and electric pulse shark-repelling device were selected to test their effects on seawater quality as well as the physiology and survival of fish using simulated ecology experiments. Three marine fish species, Japanese flounder (Paralichthys olivaceus), black rockfish (Sebastes schlegelii), and spotted grouper (Oplegnathus punctatus) were selected as test subjects. The results of water quality indicators showed that the chemical shark repellent could significantly reduce the water transparency and pH (P < 0.05), while the electric pulse shark-repelling device had no significant effect. The mortality rate of the fishes under the chemical shark repellent was 100% within 15 min, while it was 0% under both the electric pulse shark-repelling device and the blank control. While investigating the effect of the two repellent methods on the survival and physical activities, the gills and fins of juvenile fish in the chemical shark repellent group were rapidly dyed blue reaching a mortality rate of 100% within 15 min, while the juvenile fish in the electric pulse shark-repelling device group resumed their natural activities rapidly except for exhibiting avoidance behavior when the device was started. The blood indices of the species did not show any significant differences in the chemical shark repellent group because of the acute mortality caused by poisoning. However, in the electric pulse shark-repelling device group, the number of erythrocytes and leukocytes significantly increased in all three fishes. In terms of blood biochemical indices, the chemical shark-repellents caused a significant increase in chloride content, blood glucose, and alkaline phosphatase (AKP) enzyme activity in the juvenile fishes, while the blood albumin content reduced significantly in all three fishes. The use of electric pulse shark-repelling device caused a significant increase in blood glucose and glutamate transaminase activity only in the Japanese flounder. Histopathological results showed that chemical shark repellents caused tissue damage to the gill, liver, spleen, and heart in juvenile fishes. It can be seen that compared to chemical shark repellents, the electric pulse shark-repelling device is a more environmentally friendly way to repel sharks as it has less impact on seawater quality as well as less toxic effects on major marine fishes. These results would provide a scientific basis for the selection of shark repellent methods in ocean exploration activities.

With the rapidly increasing use of stable isotope analysis (SIA) in ecology, it becomes a powerful tool and complement to traditional methods for investigating the trophic ecology of animals. Sharks play a keystone role in marine food webs as the apex predators and are recently becoming the frontier topic of food web studies and marine conservation because of their unique characteristics of evolution. Recently, SIA has recently been applied to trophic ecology studies of shark species. Here, we reviewed the current applications of SIA in shark species, focusing on available tissues for analyzing, standardized analytical approaches, diet-tissue discrimination factors, diet shift investigation, migration patterns predictions and niche-width analyses, with the aim of getting better understanding of stable-isotope dynamics in shark biology and ecology research. [ABSTRACT FROM AUTHOR]