## 5 Conclusions  
The experimental results presented in this paper confirmed that the impact of water jets with velocities of a few meters per second (the highest velocity in the experiments was 11.4 m/s) is sufficient to produce melt splashes to heights of about 5 cm or more. The experiments also revealed the three-stage interaction sequence of cavity growth, which has not been reported in previous studies (see, e.g., [10] and literature quoted therein). It remains to be seen if these stages are specific to the interactions of fluids with high density ratio.  
Comparison of the experimental observations regarding the central jet formation in the melt pool indicates significant quantitative differences with the water-water interactions in terms of the regime boundaries characterized by the Weber and Froude numbers. In particular, it became clear that, due to high inertia of heavy melt, more intensive impact is  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Case** & **D, mm** & **\(u\), m/s** & \(\text{We}_{w}\) & \(\text{We}_{m}\) & \(\text{Fr}\) & \(\text{We}\)=\(63.1\cdot\text{Fr}^{0.257}\) & **Central Jet** \\ \hline J1 & 5.37 & 11 & 8925 & 15404 & 2297 & 461.1507 & + \\ J2 & 12.97 & 3 & 1603 & 2767 & 70.7 & 188.532 & - \\ J3 & 6.69 & 4 & 1470 & 2537 & 243.8 & 259.1163 & + \\ J4 & 7.5 & 3.6 & 1335 & 2304 & 176.1 & 238.3522 & + \\ J5 & 6.22 & 3.1 & 821 & 1417 & 157.5 & 231.5934 & + \\ \hline \hline \end{tabular}
\end{table}
Table 5: Non-dimensional parameters of the jet impact experiments.  
required in order to create noticeable melt splash. Further research should be devoted to the establishment of more general features of the interaction mechanism, including the scaling, which must take into account the density ratio of the pool and impacting liquids. To this end, studies must be carried out for different melt superheats, as well as a wider range of water mass and impact velocity, in order to derive relevant non-dimensional correlations.  
The results obtained in the current paper are of interest not only from the fundamental point of view, but also as an extension of the isothermal interaction of identical fluids to the \"thermal hydraulics\" dimension. The characteristics of melt splashes are also important for the evaluation of the thickness and phase concentrations in the zone above the melt layer spreading in a shallow water pool, where the melt jets and droplets can mix with water, which provides the conditions for stratified steam explosions, one of the major safety issues in the nuclear power industry and metallurgy.  
Conceptualization, S.E.Y. and Y.D.C.; methodology, S.E.Y. and Y.D.C.; experiments, A.Y.I. and V.A.U.; data analysis, S.E.Y. and V.A.U.; writing--original draft preparation, S.E.Y. and V.A.U.; writing--review and editing, Y.D.C. and S.E.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Russian Science Foundation (RSF), grant number 18-19-00289.  
Data Availability Statement: Data sharing not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.