Effects of water in film boiling over liquid-metal melts

Speculation concerning the effects of an overlying pool of boiling water on a molten LWR core/concrete interaction varying widely and range from no effect other than a source of steam to complete quenching of the debris. In the effort to quantify the effects, the experimental investigation to be described was initiated. Liquid-liquid boiling experiments have been performed with H/sub 2/O and liquid-metal melts in the 100-series test matrix (runs 121, 126, 127) and the VE test matrix. Some of the pre-explosion unstable film boiling data as well as observations from the explosive series have been previously reported. It was observed that water boiling on liquid-metal melts was unstable with respect to disturbances, and that liquid-liquid contacts were occurring at the boiling interface well into the film boiling superheat regime. The presence of these liquid-liquid contacts in film boiling was substantiated by photographic observations in transparent test sections. Narrow liquid-metal jets were observed to spike upward into the boiling water pool above, smearing out the interface between the two fluids into a mixing zone of water and liquid metal. The thickness of this mixing zone appeared from visual observations to be in the range of 1 to 2 cm. It ismore » not presently clear what physical phenomena were responsible for this behavior; however, liquid-solid contacts as well as liquid-liquid contacts in the film boiling regime will be investigated in a future test series.« less