Investigation on natural circulation for decay heat removal in reactor vessel of sodium-cooled fast reactor

Aizawa, Kosuke ; Tsuji, Mitsuyo ; Kobayashi, Jun ; Kurihara, Akikazu ; Miyake, Yasuhiro*; Nakane, Shigeru*; Ishida, Katsuji*

In sodium-cooled fast reactors (SFRs), optimizing the design and operate decay heat removal systems (DHRSs) is important for safety enhancement against severe accidents that could lead to core melting. The natural circulation phenomena in a reactor vessel during operating a DHRS were clarified by conducting water experiments using a 1:10 scale experimental facility (PHEASANT) simulating the reactor vessel of loop-type SFRs. In this study, we investigated the natural circulation phenomena under conditions of operating the dipped-type DHX and RVACS using the results of temperature and particle image velocimetry (PIV) measurements, respectively. Furthermore, the effects of temperature fluctuation on the PIV measurement were quantitatively evaluated.