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BackgroundThe reactor period will dramatically decrease at the beginning of reactivity insertion in the nuclear reactor, which may trigger the protection system of the reactor period and lead to unnecessary shutdown. The instantaneous short reactor period is influenced greatly by the inserting rate of reactivity, but also related with the present delayed neutron precursors, which is difficult to quantify.PurposeThis study aims to explore the relationship between the instantaneous short reactor period and the inserting rate of reactivity from a theoretical perspective.MethodsA point reactor model was used to deduce the inserting rate of the reactivity function using the variable factors of reactivity, reactor period, and reactor dynamic parameters, with some conservative assumptions to omit the effect of delayed neutron precursors. The relationship between reactivity insertion rate and transient period of reactor was derived after analysis on the short period phenomenon. Then, the formula of relationship was verified for several transient cases.ResultsThe results show that the reactor periods are all larger than the aim reactor periods for all transient cases when using the rate constraint of reactivity insertion in the aforementioned formula. According to the proposed theoretical framework, unnecessary shutdown during an instantaneous short reactor period can be avoided.ConclusionsA theoretical framework proposed in this study can be applied to the control of rod withdrawal rate during the operation of nuclear reactors.

BackgroundThe medical isotope production aqueous reactor (MIPR) has advantages of small size, low power, and high inherent safety, hence is one of better candidate reactor types for the production of 99Mo and other medical isotopes.PurposeThis study aims at the effects of extraction methods and reprocessing capacity on the production efficiency of 99Mo based on low-enriched uranium MIPR designed with neutronic optimization.MethodsFirst, the calculation method was verified according to existing experimental data, and the neutronic optimization of the MIPR was performed for core design by using SCALE6.1 code and ENDF/B-VII database with 238 groups. Then, the 99Mo production efficiency under different extraction methods as well as processing capacities was investigated based on the optimized core structure. The range of achievable critical uranium concentration and enrichment was determined.ResultsThere is a minimum critical mass under different enrichment, and with the increase of 235U enrichment, the uranium concentration at the minimum critical uranium mass decreases. The effective multiplication factor decreases linearly with an increase in nitric acid concentration, and the corresponding nitric acid reactivity coefficient is approximately -1.400×10-2 L·mol-1. With an increase in uranium concentration, the void and temperature reactivity coefficients decrease, and the corresponding reactivity coefficients are approximately (-100~-250)×10-3 ℃-1 and (-18~-30)×10-5 ℃-1.ConclusionThe production efficiency of the MIPR production of the 99Mo online extraction method is slightly greater than that of the offline batch processing method with an increment of about 16% under a five-day production cycle. The reprocessing capability has a greater impact on the production efficiency of the online extraction method. If the reprocessing rate is increased five times, the increment of production efficiency is about 113% under a five-day production cycle.

Cu/Cu2O cermet composites were prepared with hot pressing graphite reduction methods. The DC electrical conductivity of Cu/Cu2O cermets, with various volume contents and random distribution status of the conducting phase was tested. To quantitatively characterize the shape, size, and distribution status of the conducting phase, the fractal dimensions of the conducting phase(Cu) were calculated through the binarized image analysis. The percolation behavior was analyzed, and the relationship between microstructure and electrical properties was studied. The results show that the quantities of the percolation infinite cluster and backbone increase with the increasing volume fraction of the conducting phase, but the backbone density fluctuates near the percolation threshold. Furthermore, the difference of fractal dimension between Cu/Cu2O cermet composites perpendicular to hot pressing direction and the parallel to hot pressing direction is about 0.1.An approach is provided to quantitatively characterize the microstructure of the conducting phase in dual-phase conductor/insulator composites, which is beneficial to predict the properties of composites with a randomly distributed second phase.

During the early Cenozoic, the collision and convergence between India and Eurasia resulted in the uplift of the Tibetan Plateau and continuous northward compression, forming the Circum‐Tibetan Plateau Basin and Orogen System (CTPBOS). The Tarim Basin, located between the Tibetan Plateau and the Tianshan Mountains, plays a crucial role for studying the convergence‐driving strain propagation mechanism intra‐Asian continent during the growth processes of the Tibetan Plateau. Owing to the lack of accurate geophysical information on the deep structure of the Tarim crust，the mechanism of Cenozoic deformation in the Tarim Basin has been under debate. In this paper, the teleseismic data acquired by the broadband seismic profile across the Tarim Basin from south to north and the S‐wave receiver function method were used to obtain the depth of the Moho and the discontinuities in the lithosphere beneath the Tarim Basin. The SRF result shows that the Moho geometry has an abrupt relief under the Bachu Uplift, and Moho offset under the fault zone between the Kalashayi Fault and the Tumuxiuke Fault. The regional dip of the Moho under the Bachu area can be explained by the root of the Bachu basement‐involved uplift cutting across the whole crust and locally penetrating into the mantle lithosphere. The Bachu Uplift, located in the central Tarim terrane, has a relatively weak lithosphere. In the process of forming the Tarim large igneous province during the early Permian, the crust beneath the Bachu area was weakened and thinned by the thermo‐mechanical erosion from upwelling mantle plume. As the collision and convergence of India and Eurasia since the early Cenozoic, the convergence‐driving strain was propagated into the Tarim Basin. The pre‐existing weak Bachu Uplift was reactivated. The Tarim Basin absorbs Cenozoic compressional deformation through the crustal shortening and Moho offset of the Bachu Uplift. [ABSTRACT FROM AUTHOR]

The Guxiang–Tongmai segment of the Jiali fault is situated northeast of the Namche Barwa Syntaxis in northeastern Tibet. It is one of the most active strike‐slip faults near the syntaxis and plays a pivotal role in the examination of seismic activity within the eastern Himalayan Syntaxis. New study in the research region has yielded a 1:200000 gravity dataset covering an area 1500 km2. Using wavelet transform multiscale decomposition, scratch analysis techniques, and 3D gravity inversion methods, gravity anomalies, fault distributions, and density structures were determined across various scales. Through the integration of our new gravity data with other geophysical and geological information, our findings demonstrate substantial variations in the overall crustal density within the region, with the fault distribution closely linked to these density fluctuations. Disparities in stratigraphic density are important causes of variations in the capacity of geological formations to endure regional tectonic stress. Earthquakes are predominantly concentrated within the density transition zone and are primarily situated in regions of elevated density. The hanging wall stress within the Guxiang–Tongmai segment of the Jiali fault exhibits a notable concentration, marked by pronounced anisotropy, and is positioned within the density differential zone, which is prone to earthquakes. [ABSTRACT FROM AUTHOR]

The letter to the editor discusses the use of shear-wave elastography (SWE) as a diagnostic method for encapsulating peritoneal sclerosis (EPS) in patients undergoing peritoneal dialysis (PD). The authors argue that while SWE has been successful in other areas of imaging, it may not be suitable for diagnosing EPS due to the limited evidence from a single patient in the study. They suggest that computed tomography (CT) remains the recommended method for diagnosing EPS, especially in long-term PD patients. The authors call for further research to compare the effectiveness of CT and SWE in detecting EPS, particularly in the early stages. [Extracted from the article]