Computer Code for Large Leak Sodium-Water Reaction Analysis-SWACS/REG3-(Program Description):Large Leak Sodium-Water Reaction Analysis(Repart No.3 Revision

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Miyake, Osamu*; Shindo, Yoshihisa*; Sato, Minoru*

Miyake, Osamu*; Shindo, Yoshihisa*; Sato, Minoru*

A computer code, SWACS, has been developed for analyzing a large-scale sodium-water reaction accident in a steam generator system of LMFBRs. The SWACS integrated code system is capable of predicting the principal events relevant to the large-scale water leak accident in the steam generator of LMFBRs: leaking flow of water/steam mixture from a ruptured heat-transfer tube into sodium in any one of the steam generators; propagation of pressure wave generated by sodium-water reaction both within the faulted steam generator and into the secondary cooling system ; and hydraulic transients induced in the secondary cooling circuit and reaction relief system. The water/steam leaks postulated in the SWACS code are, in principle, equivalent to those from the breach of one double-ended (guillotine) rupture of heat-transfer tube. This report summarizes the underlying models and numerical methods adopted in the SWACS code. It is to be noted that a companion volume (PNC SN952 79-20) may serve as an input manual for users. SWACS contains and controls the following three prenomenological modules SWAC-11, -5K/7 and -13: (1)SWAC-11 is the module for analyzing the water-side transients and the leaking flow of water/steam mixture into sodium of a faulted steam generator. Fundamental equations are one-dimensional mass, momentum and energy conservation for either subcooled or saturated water, or superheated steam. The two phase flow is assumed to be homogeneous (non-slip) flow in thermal equilibrium between the two phases. Compressibility of the fluid is considered for accounting the rapid transient of the water/steam flow in the very early stage of tube rupture. Boundary conditions are imposed at the inlet and outlet headers of water loop and the openings of the ruptured heat-transfer tube. The back pressure at the openings is taken as the pressure of reaction zone which is provided by the SWAC-5K/7 module. (2)SWAC-5K/7 analyzes the behavior of rapid pressure transient, called ...