DCC-1/DCC-2 degraded core coolability analysis

The DCC-1 and DCC-2 experiments have provided the first data on dryout and quench behavior of internally heated UO/sub 2/ debris in water. The pressure range of this data extends from 1 to 170 atmospheres. Both of the experiments used the Annular Core Research Reactor (ACRR) at Sandia National Laboratories to simulate the effects of radioactive decay heating. The debris in DCC-1 ranged from 75 microns to in excess of 10 mm in diameter, with a mean diameter of 0.75 mm. The bed depth was 0.5 m and the porosity was 0.345. Dryout heat fluxes ranged from about 41 kW/m/sup 2/ (0.012 W/g) at a saturation temperature of 100/sup 0/C to about 69 kW/m/sup 2/ (0.021 W/g) at 340/sup 0/C. This measured pressure dependence is a factor of two to three lower than predicted by the analytical models. This is believed to be due to the breadth of the debris distribution, but the evidence is inconclusive. Quenches of dried debris took hours to complete. The debris distribution in DCC-2 was much narrower than in DCC 1, with the majority of particles having diameters between 0.5 and 8 mm. A small amount of ''fines'' with diameters down to 75 microns wasmore » added to the mixture. In DCC-2, thermally stable local dry zones were observed at bed powers below the conventional dryout point. Quenches of dry zones took about 10 minutes to complete. 25 refs., 39 figs., 16 tabs.« less