دانلود رایگان مقاله لاتین تعامل سوخت خنک کننده از سایت الزویر
عنوان فارسی مقاله:
مطالعه مقدماتی بر تعامل سوخت خنک کننده رها شده توسط اثر حرارتی
عنوان انگلیسی مقاله:
Preliminary study on the fuel-coolant interaction triggered by thermal effect
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
In severe accident scenarios, the core-melt accident may occur because of lack of sufficient cooling. Without enough coolant supply, the nuclear core starts to degrade from a relatively high position. As the core is partially damaged, core melt may go through downwards into the lower plenum, and even relocate in the lower head of the vessel. If there is a little water remaining in the lower head, maybe a sort of in-vessel vapor explosion can be induced. While if the lower head has already been dried out, the residual melt may continue to melt through the structure, and finally be scattered around the reactor cavity. Once the high temperature melt contacts with the volatile coolant, the fuel-coolant interaction (FCI) can occur, which may result in vapor explosion and seriously damage the reactor cavity or the containment structure. Due to its likely radioactive threats and many uncertain negative effects involved, researchers have drawn much attention to this issue of FCI. In regards to interpreting the phenomenon of fuel and coolant interaction, a large set of experiments were launched, one of which was large scale tests of corium or stimulant materials. In this group, ALPHA (Yamano et al., 1995; Yamano et al., 1999) researched on the vapor explosion characters, including dynamic pressure history and debris distribution, and pointed out that such involved FCI mechanisms should be figured out. KROTOS (Huhtiniemi and Magallon, 2001; Hohmann et al., 1995; Huhtiniemi et al., 1999) focused on vapor explosion and energy conversion process based on spontaneous trigger or external trigger condition, and firstly presented that the interaction between hot alumina and cold water is much more violent, thus generating a very strong and sharp pressure increase. However, due to lack of FCI mechanism analysis, such new findings could not completely be adopted in mechanistic code for FCI. KAERI carried out the TROI (Song et al., 2002, 2003; Kim et al., 2008) tests, analyzing the speci- fic effect of melt material on vapor explosion, and concluded that ZrO2 can trigger an even higher vapor explosion. While, if iron was added to the melt, it seemed that the spontaneous vapor explosion was suppressed, but this result still needs to be examined. The other group of experiments was to research on interaction mechanism by small scale tests. For example, SIGMA (Luo et al., 1999) observed the micro-interaction process by high speed camera, and described the mixing region. MISTEE (Park et al., 2009) was highly instrumented by two high speed cameras and an X-ray detector, depicting the premixing and fragmentation process exactly. Besides, SJTU (Lin et al., 2009) systematically analyzed various impact factors on thermal fragmentation mechanisms by SSFT facility and a typical thermal fragmentation partition map was drawn. Recently, based on the contribution of OECD (OECD/NEA, 2007), it was recognized that the level of loads would not challenge the integrity of the reactor vessel. However, the problem is that the ex-vessel FCI would probably cause the damage of reactor cavity, affecting the integrity of the containment building. In addition, plenty of FCI codes have been adopted in order to obtain better estimations. People still can’t select the best result from those predictions obtained from the codes so far, which makes the potential damage unpredictable. Therefore, further research on the thermal interaction of coolant and melt must be carried out aiming at getting better interpretations of this issue. SJTU has set up an intermediate-scaled experimental facility named ‘ISFCI’ to carry out the thermal interaction analysis using stimulant materials. The objective of the ISFCI is to study the mechanisms behind the thermal interaction and develops a new mechanistic model for this process, based on the new experimental findings. In this paper, the first series of test results are presented, in which the debris characteristics under different initial conditions will be firstly described, followed by FCI mechanisms behind. Finally, the corresponding pressures generated from each trial will be qualified and quantified so as to support the analysis of the impact factors.
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