Numerical quantification of dissolved gas behavior in primary coolant system of fast reactor; Suppression of gas entrainment using dipped plate

Eto, Kenichiro*; Yamaguchi, Akira*; Takata, Takashi*; Ohshima, Hiroyuki; Ito, Kei

When inert gas is present in the primary coolant of a sodium cooled fast reactor (SFR), it may cause a core power fluctuation or a reduction of heat transfer at an intermediate heat exchanger (IHX). Therefore, it is necessary to clarify an allowance level of the gas in the system design of SFR. In Japanese Sodium Fast Reactor (JSFR), a dipped plate (D/P) will be installed at the upper plenum so as to suppress a fluid fluctuation at the free surface and entrainment of argon (Ar) gas bubbles into the piping system. In the present study, an influence of the D/P on the gas behavior has been investigated using the VIBUL code. As a result, it is demonstrated that the entrainment of Ar gas is suppressed considerably by the D/P although the background void fraction, in which no Ar entrainment from the free surface is taken into account, increases comparing with that without D/P. The quantification of the allowance level of Ar entrainment is also investigated based on the computation result.