For a more dense read, see the whitepaper[1] from Oak Ridge National Laboratory about FCM fuels, which seems to be one of the key innovations of this reactor type. Instead of using pellets of Uranium oxide directly inside the reactor, this method encapsulates the fuel in a high temperature ceramic material which makes it very unlikely for the reactor to 'melt down' the way that mainstream reactors can.

[1] https://info.ornl.gov/sites/publications/Files/Pub42476.pdf