Experimental investigation of 150-kg-scale corium melt jet quenching in water Original Research Article

The paper compares and discusses the results of two large scale FARO quenching tests known as L-11 and L-14, which involved respectively, 151 kg of 76.7 wt.% UO2+19.2 ZrO2+4.1 Zr and 125 kg of 80 wt.% UO2+20 ZrO2 melts poured into 600-kg, 2-m deep water at saturation at 5.0 MPa. The results are further compared with those of two previous tests performed using a pure oxidic melt, respectively 18 and 44 kg of 80 wt.% UO2+20 ZrO2 melt quenched in 1-m deep water at saturation at 5.0 MPa. In all the tests, significant breakup and quenching took place during the melt fall through the water. No steam explosion occurred. In the tests performed with a pure oxide UO2–ZrO2 melt, part of the corium (from 1/6 to 1/3) did not break up and reached the bottom plate still molten, whatever the depth of the water. Test L-11 data suggest that full oxidation and complete breakup of the melt occurred during the melt fall through the water. A proportion of 64% of the total energy content of the melt was released to the water during this phase (∼1.5 s), against 44% for L-14. The maximum temperature increase of the bottom plate was 330 K (L-14). The mean particle size of the debris ranged between 3.5–4.8 mm.