Scar17s said:
After a reactor meltdown, what material (Non burn through) is best material suited to contain the after-effects?
Well, ideally, a molten core does not breach the reactor pressure vessel, as was the case in the accident at TMI-2. In the case of Chernobyl, molten fuel did escape the vessel, and at Fukushima, we do not know, but it is speculated that some melting of two or three cores took place, and some escape the RPVs.
The new Gen-III+ designs do consider 'core catchers' to varying degrees. Notably, AREVA's EPR has a 'core catcher' design, although the composition of the particular material is not published.
Argonne National Lab (ANL) has done an evaluation of a code used to simulate a core catcher.
https://www.nrc.gov/docs/ML0909/ML090960360.pdf Reference 20 and 21 refer to studies of materials.
20. M. Sappok and W. Steinwarz, “COMAS Experiments as Contribution to the Validation of the EPR Mitigation Concept for Core Melt Accidents,” 6th International Conference on Nuclear Engineering (ICONE-6), San Diego, California, May 10-15, 1998.
21. W. Steinwarz, A. Alemberti, W. Häfner, Z. Alkan, and M. Fischer, “Investigations on the Phenomenology of Ex-Vessel Core Melt Behavior (COMAS),” Nuclear Engineering and Design, Vol. 209, pp. 139-146, 2001. (requires purchase)
See also - Experimental results on concrete-melt-interaction within the large scale COMAS project
( M. Sappok, W. Steinwarz, E.P. Warnke and G. Langer)
https://www.iasmirt.org/transactions/14/P03-2
Ideally, the material has a high melting point and minimal chemical reactivity. Insulation materials used in foundries might be applicable. Also, to ensure subcriticality, some amount of borates may be incorporated. Graphite would work as a sub-base material. A geometry that separates the flow into smaller flows may be employed. There would be also the issue of how much water would accompany the core melt into the catch vault.