| Summary: | 碩士 === 國立清華大學 === 核子工程與科學研究所 === 105 === The quenching of molten corium in the coolant in crucial for the management of severe nuclear accident. The objective of the present study is to investigate the quenching phenomenon of high temperature molten materials in de-ionized water or sea water. At first, cooper particles was employed as the simulated molten material. The experimental results reveal that, in sea water, the interface between water and vapor is very wavy. However, it is quite smooth in de-ionized water. Moreover, the surface of the solidified copper after quench is smoother than the coolant at high sub-cooling that at low sub-cooling. It is also found that there is no or very little fragmentation effect.
So we use to more closely simulate molten corium, through literature review, Bismuth trioxide and Tungsten trioxide powder (BTOP) was subsequently used as the molten material. To study the superheat effect of molten BTOP on the quenching, the BTOP is heated to 1000℃ or 890℃, respectively. Fragmentation effect become apparent for the caucusing BTOP as the simulation. For the case of 1000℃, there is fragment cloud surrounding the melt stream, but it is absent for the case of 890℃ . On the other hand, it is also of significant importance to investigate the quenching phenomena in different coolant, i.e. de-ionized water and sea water. Significant different two-phase flow phenomena in present between the two fluids. Moreover, the mass accumulation distribution of fragment also demonstrates significant difference. The fraction of big fragments in the sea water is significantly more than that in the de-ionized water. The examination of the images of High Resolution Thermal Field Emission Scanning Electron Microscope (SEM) on the fragment surface also shows significant difference. In the sea water, the particle surface is rough and presents a lot of particles with different size, while it is smoother in the de-ionized water. The many ions in the sea water may create the zeta potential effect, like that between solid surface and sea water, resulting in significant contacts between liquid coolant and molten BTOP.
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