I exchanged email with Hyperion Power Generation (the maker of the new power generator. They indicate that the Sante Fe reporter made a mistake. The output is about 25-17 MW ELECTRIC [This statement was also consistent with the patent which talked about tens of MW in electricity. They also said that the containment vessel will be dense enough that no radiation will escape even if it is not buried in the ground.
Hyperion does not have a detailed diagram of the heat piping but there does not seem like there should be anything special about the heat piping system. In this presentation on slide 34 and 35 they have the density of heat pipes which seems appropriate About 1/9th of the volume taken up with heat pipes