Analysis and treatment of large-scale nuclear heating commissioning problems

Through the modification of a nuclear power plant, the extraction steam on the exhaust pipe of the high-pressure cylinder of the steam turbine is used to heat the circulating water of the heat network, and the pressurized anf heated circulating water of the heat network is supplied to the secondary thermal power station, and then supplied to various users after heat exchange, realizing the first large-scale nuclear heating in China. This paper introduces the function and process of nuclear heating system, and focuses on the analysis of the problems in the commissioning process, which provides a reference for the commissioning of other domestic nuclear power plants after nuclear heating modification

Cause Analysis and Solution of Boron Concentration Reduction in Three Generation Nuclear Power Passive Core Makeup Tank (CMT)

During the normal operation of the third-generation nuclear power plant, according to the requirements of the technical specification (TS), the CMT should be sampled every seven days, which should be controlled between 3400ppm and 4500ppm. However, due to various reasons, the boron concentration of CMT will drop abnormally. In order to meet the requirements of the technical specification, it is necessary to supplement boron to CMT frequently, which will cause a series of serious problems. Therefore, it is necessary and urgent to solve the problem of abnormal reduction of boron concentration in CMT

Effect of the Distribution Characteristics of TiC Phases Particles on the Strengthening in Nickel Matrix

Molecular dynamics (MD) was used to simulate the effect of TiC particles distribution on the tribological behavior of the reinforced composites. The mechanical properties, friction coefficient, number of wear atoms, stress and temperature, and microscopic deformation behavior of TiC/Ni composites during nano-friction were systematically investigated by MD to reveal the effect of TiC distribution on the friction removal mechanism of the material. It was found that the larger the radius of the TiC particles, or the shallower the depth of the TiC particles, the easier it was to generate stress concentrations around the TiC particles, forming a high dislocation density region and promoting the nucleation of dislocations. This leads to severe friction hardening, reducing the atomic number of abrasive chips and reducing the friction coefficient by approximately 6% for every 1 nm reduction in depth, thus improving the anti-wear capacity. However, when the radius of the TiC particles increases and the thickness from the surface deepens, the elastic recovery in material deformation is weakened. We also found that the presence of the TiC particles during the friction process changes the stress state inside the workpiece, putting the TiC particles and the surrounding nickel atoms into a high-temperature state and increasing the concentrated temperature by 30 K for every 1 nm increase in depth. Nevertheless, the workpiece atoms below the TiC particles invariably exist in a low-temperature state, which has a great insulation effect and improves the high-temperature performance of the material. The insight into the wear characteristics of TiC particles distribution provides the basis for a wide range of TiC/Ni applications

Molecular Dynamics Simulation of Chip Morphology in Nanogrinding of Monocrystalline Nickel

In this study, the nanogrinding process for single-crystal nickel was investigated using a molecular dynamics simulation. A series of simulations were conducted with different tool radii and grinding methods to explore the effects of chip morphology, friction forces, subsurface damage, and defect evolution on the nanogrinding process. The results demonstrate that the workpiece atoms at the back of the tool were affected by the forward stretching and upward elastic recovery when no chips were produced. Although the machining depth was the smallest, the normal force was the largest, and dislocation entanglement was formed. The small number of defect atoms indicates that the extent of subsurface damage was minimal. Moreover, when spherical chips were produced, a typical columnar defect was generated. The displacement vector of the chip atoms aligned with the machining direction and as the chips were removed by extrusion, the crystal structure of the chip atoms disintegrated, resulting in severe subsurface damage. By contrast, when strip chips were produced, the displacement vector of the chip atoms deviated from the substrate, dislocation blocks were formed at the initial stage of machining, and the rebound-to-depth ratio of the machined surface was the smallest