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The region from cladding to pellet of the leak rod with the burnup of 41 GW·d/tU and the intact rod with the burnup of 45 GW·d/tU was characterized by nanoindentation, metallurgical microscope, and Raman spectroscopy. The results show that a porous high burnup structure (HBS) appears on the pellet periphery of the intact rod, and this phenomenon results in the decrease of the hardness of periphery of the pellet. The hardness of the pellet of the leak rod decreases along the radial direction towards the centre of the pellet, which is mainly related to the migration of the pores and the reconstruction of the fuel pellet. After the leak of the cladding, coolant enters the gap between the cladding pellets and reacts with the pellets. The porosity of the HBS of the leak rod is less than that of the intact rod, and the hardness of the HBS of the leak rod is slightly higher. Meanwhile, the temperature change leads to grain reconstruction and the formation of large-sized columnar crystals, resulting in the decrease of hardness in the middle and centre of the leak rod fuel pellet. The leak of the cladding does not change the phase composition of the pellets. As a result, the Young's modulus of intact rod and leak rod pellets does not show much difference. The hardness of the FCCI layer of the intact rod increases gradually along the cladding towards the pellet, while the Young's modulus firstly decreases and then increases. The hardness of the FCCI layer of the leak rod increases at first and then decreases, while the change of the Young's modulus is in general similar to the hardness of the leak rod along the cladding to the pellet. The phenomenon arises from the combined effects of phase structure transformation and fission product doping. The hydrogenation and oxidation of the cladding after the leak of the fuel rod results in a significantly higher hardness and Young's modulus of the leak rod cladding than that of the intact rod.

Ephemeral gully (EG) erosion is an important type of water erosion. Understanding the spatial distribution of EGs and other influencing factors at a regional scale is crucial for developing effective soil and water management strategies. Unfortunately, this area has not been sufficiently studied. The present study visually interpreted the EGs based on Google Earth images in 137 small watersheds uniformly distributed in the Loess Plateau, compared them with measured results, and analyzed the factors influencing EG formation and density using GeoDetector. The results showed that visually interpreting EGs from Google Earth images was suitable for EG regional studies. Out of the 137 small watersheds, 33.6% had EG occurrence with an average density of 3.41 km/km2. Rainfall (R) and slope gradient (S) were the primary factors influencing the formation of EGs, while the area proportion of sloping farmland (APSF) and soil erodibility (K) were the main factors affecting EG density. The interaction of dual factors had a greater influence compared to single factors, with the interaction between S and Normalized Difference Vegetation Index (NDVI) having the greatest impact on EG formation and the interaction between K and NDVI on EG density. Although natural forces significantly influence whether EGs can form in a specific area, human activities greatly affect the density of the gullies that develop. This underscores the importance of proper land management in controlling gully erosion. These findings could provide theoretical support for EG prediction models and a scientific basis for soil and water loss control strategies at the regional scale. [ABSTRACT FROM AUTHOR]

At present, the return of farmland to forests is the key ecological conservation policy in use to control soil erosion and restore the ecoenvironment of the Loess Plateau, China. In order to explore policy-driven ecological defarming scenarios, Ansai County is taken as a case study. The land use map in 2000 and the topographic and slope map (taking the defarmed slopes with 15°, 20°, and 25° as the defarming thresholds) were used, supported by spatial analysis techniques in geographic information systems (GIS). This paper simulates and analyzes the scale and spatial difference of ecological defarming of Ansai County, the subsidy demand for defarming, and the influences of defarming on agricultural development. The results show: (1) The area of defarmed land with slopes greater than 25° in Ansai amounts to 3451.05 ha, which accounts for 2.84% of total area with slopes over 25°, and the defarming index will be 3.14%. The total subsidy demand for defarming land will be 6884.84 × 104 yuan (RMB) or US$1008.03 × 104. The loss of agricultural food products that results from defarming will be 955.17 t in the average year, or 1.66% of total average annual production. (2) The area of defarmed land with slopes from 20°-25° in Ansai will increase to 36,281.61 ha, which accounts for 19.74% of total area with slopes of this class, and the defarming index will be 32.96%. The total subsidy demand for defarming land will be 72,381.81 × 104 yuan or US$10,597.63 × 104. The loss of agricultural food products due to defarming will be 10,041.9 t in the average year, or 17.50% of total average annual production. (3) The area of defarmed land with slopes from 15°-20° in Ansai increases to 101,807.99 ha, which accounts for 37.23% of total area with slopes in this class, and the defarming index will be 92.49%. The total subsidy demand for defarming land will be 203,106.94 × 104 yuan or US$29,737.47 × 104. The loss of agricultural food products owing to defarming will be 28,178.06 t in the average year, or 49.10% of total average annual production. [ABSTRACT FROM AUTHOR]