It is not based on radioactive decay but on fission, the usage of Sterling engines is correct. [1] [...] the core of the reactor will be of solid, cast uranium

It is not based on radioactive decay but on fission, the usage of Sterling engines is correct. [1] [...] the core of the reactor will be of solid, cast uranium-235 surrounded by a beryllium oxide reflector. This reflector focuses neutron emissions and returns their energy back into the core to minimize nuclear gamma radiation [...]. Nuclear reaction control is provided by a single rod of boron carbide which is a neutron moderator that is initially fully inserted, [...]. Once the moderator is extracted the nuclear chain reaction will start but can not be stopped completely, although the depth of insertion provides a mechanism to adjust the heat output [...]. Passive heat pipes filled with liquid sodium then transfer the reactor core heat to one or more Stirling engines, which converts heat into rotary motion that drives a conventional electric generator. [1] https://en.wikipedia.org/wiki/Kilopower https://en.wikipedia.org/wiki/Kilopower