Decay Heat Removal under Boiling Condition in a Pin-Bundle Geometry

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Haga, K.*; M.Uotan*; Yamaguchi, K.*; M.hori*

Haga, K.*; M.Uotan*; Yamaguchi, K.*; M.hori*

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Decay heat removal capability under boiling condition was investigated using an electrically heated 37-pin bundle test section. The flow was driven by natural circulation force of the out-of-pile sodium loop SIENA in O-arai Engineering Center, PNC. As the heater power was increased, the two-phase flow regime changed from bubbly flow to slug flow and then to annular or annular mist flow. In 15 runs, dry-out was not observed in the average exit quality region of less than 0.5. The results indicated the existance of a large "boiling window" for low flow rate and low power conditions.