Lessons learnt from FARO/TERMOS corium melt quenching experiments Original Research Article

The influence of melt quantity and composition, water depth and initial pressure on quenching is assessed on the basis of seven tests performed under various conditions in the TERMOS vessel of the FARO facility at JRC-Ispra. Tests involved UO2-based melt quantities in the range 18–176 kg at a temperature of approximately 3000 K poured into saturated water. The results suggest that erosion of the melt jet column is an efficient contributor to the amount of breakup, and thus quenching, for large pours of corium melt. The presence of Zr metal in the melt induced much more efficient quenching than in a similar test with no Zr metal, which can be attributed to oxidation of the Zr. Significant amounts of H2 were also produced in tests using pure oxidic melts (e.g. about 300 g for 157 kg melt). In tests at 5.0 and 2.0 MPa, good mixing with significant melt breakup and quenching was obtained during the penetration in the water. At 0.5 MPa, good penetration of the melt into the water could still be achieved, but a jump in the vessel pressurisation occurred when the melt contacted the bottom and part of the debris (5 kg) was re-ejected from the water.