Experimental study of non-heating pool boiling simulation and CHF on reactor vessel wall

Abstract

In this study, mainly two experimental works have been done. The first one is the non-heating simulation of pool boiling and CHF using the air-blowing drilled flat plate and the related analytical study on the formation of macrolayer. And the second is the CHF experiments for the in-vessel retention strategy of severe accident. First, the non-heating experimental method was proposed and confirmed by the experiments and analytical study. The proposed non-heating experimental methodology is based on the macrolayer dryout model: by measuring the initial macrolayer thickness and bubble departure frequency from the non-heating experiments, the onset of CHF can be predicted based on the macrolayer thickness. Through the non-heating experiments, the void fraction, the macrolayer thickness and the bubble departure frequency were measured. The macrolayer thickness measured by the conduction probe was generally well agreed with the previous steam-water experiments in its trend and magnitude. And, the predicted CHF values by the proposed methodology were generally agreed well with the boiling CHF data for horizontal, flat plate. On the other hand of experimental works, an analytical study on formation of the macrolayer and its relation with the CHF was conducted. Through this analytical study, we found that the lateral coalescence of the growing bubble was the underlying mechanism of the macrolayer formation. Through this experimental and analytical study, the feasibility of the non-heating simulation was confirmed. Second, the CHF on the reactor vessel outer wall was measured using 2-dimensional slice test section. Because there is few CHF data for the mass flux less than 200 kg/㎡sec, in this experimental study, the mass flux effect on the CHF was mainly studied. The radius, the width of heater and the channel gap were 2.5 m, 10 cm and 15 cm relatively. The CHF data under the inlet subcooling of 2~14 K and the mass flux 6~210 kg/㎡sec had been acquired and a CHF corre...