دانلود رایگان مقاله تعامل سوخت خنک کننده رها شده توسط اثر حرارتی

Abstract

The phenomenon of thermal interaction plays a key role in fuel and coolant interaction (FCI) during NPP’s severe accidents, which determines the ratio of heat transferred to mechanical energy. However, the phenomenon is still not well understood due to its transient process and various involved likely mechanisms. In the present study, a new facility for intermediate-scaled FCI experiments has been set up, named ISFCI, mainly concentrating on the influencing factors and thermal interaction mechanism of high melting substances within the confined space. In the first series of tests, 304SS and Fe-Mo have been chosen for the melt materials with superheating temperature ranging from 150
C to 300
C. The initial mass of each material has been controlled by 1 kg or 2 kg. By grouping and characterizing the debris, the effect of initial mass, melt properties and melt superheating temperature on thermal interaction has been qualitatively analyzed. In addition, the pressure data recorded from these tests have been used to quantify the influencing analysis. Based on the morphology analyzing method and quantification, two relatively worse conditions that could cause larger and/or longer pressure increase have been identified.

4. Conclusions

In this paper, the test facility and conditions for thermal interaction of coolant and melt have been introduced at first. Then, four groups of experimental results have been analyzed based on the effects of initial mass, melt properties and melt superheating temperature. With the help of the morphology method and the pressure recorded by pressure transducers, the main conclusions can be drawn, as follows. (1) Compared with Case1 and Case2, the mass fraction of jet breakup products increases with the increase of the initial mass, while the fragmentation products are reduced. It can be inferred from the fact that under a certain configuration and test condition, whether the premixing zone is large or not has a significant effect on the thermal interaction strength. (2) Density and heat capacity of the melt are the influencing factors to affect the premixing, and a relatively worse condition determined from the present study is that a much stronger pressure increase would be induced and maintains a long time, when the melt gets a larger density and heat capacity. (3) The melt superheating effect can significantly strengthen the mass fraction of premixing products and thermal fragmentation ratio. Similarly, another relatively worse condition determined from the present study is that a much stronger pressure increase would be induced and maintains a long time, when the melt gets a higher superheating temperature. All in all, there were only mild interactions happening in the first series of tests, and it can be inferred that it’s the ‘stable system’, such as inert melt properties or lower water depth, that may suppress the vapor explosions induced by the interaction of coolant and melt. Therefore, some tests based on higher water depth or different melt mass in different superheating temperature should be performed for the purpose of better interpreting this kind of issue.