Development of numerical simulation method for molten fuel falling behavior based on detailed two-phase analysis code TPFIT

詳細二相流解析コードTPFITを基にした溶融燃料落下挙動解析手法の開発

鈴木 貴行; 吉田 啓之  ; 成島 勇気*; 金子 暁子*; 阿部 豊*

Suzuki, Takayuki; Yoshida, Hiroyuki; Narushima, Yuki*; Kaneko, Akiko*; Abe, Yutaka*

In order to improve the safety of BWR, it is required to evaluate the behavior of the plant when a severe accident occurred as seen at Fukushima Daiichi NPPs. The behavior of molten core jet in the lower pressure vessel is one of the key phenomena affecting the progress of the severe accident. In the BWR lower plenum, the characteristics of molten core jet are affected by many complicated structures, such as CRGTs and so on. However, it is difficult to evaluate these effects on molten core jet experimentally. The objective of this study is to develop the evaluation method of the characteristics of molten core jet including the effects of the complicated structures in the BWR lower plenum. In this development, we are developing a simulation method to estimate the behavior of molten core jet falling down to the lower plenum of the BWR. The method has been developed based on interface tracking method code TPFIT. The TPFIT was applied to the numerical simulation of visualization jet breakup experiments performed at the University of Tsukuba. In the simulation, the center part of the experimental apparatus was modeled. In this paper, simulated results, including the effects of the complicated structures of jet breakup phenomena, are shown. In addition, the applicability of the modified TPFIT to the jet breakup phenomena is discussed by comparing numerical results with experimental results in detail.