How soluble is uranium in molten iron?
According to Uranium partitioning between liquid iron and silicate melt at
high pressures: implications for uranium solubility in
planetary cores


  The solubility of U in
  liquid Fe is in the range of 0.6 to 800 ppm and increases with temperature (T) and
  pressure (P).


See also U solubility in Earth’s core which finds a solubility of 2 ppm at zero pressure (run number 198).