The rate of radiation damage from radioactive species in nuclear waste ceramics and the long term stability of the crystalline phases may depend on the crystallographic site of the emitting species. It is therefore of importance to determine the site occupancy of the radioactive elements. Hitherto, no established crystallographic technique has been suitable for such studies due to the small grain size and the many different phases in nuclear waste ceramics, such as Synroc. By taking advantage of the fact that an electron beam can be focussed, and the electron intensity localized, to a particular crystal site by electron diffraction, a new technique capable of locating small concentrations of atoms in small crystal volumes >(10 nm)3 has recently been developed. The application of the technique to determining the site occupancy of solutes, including U, Sr, Th, in the perovskite and ulvo-spinel phases of a Synroc ceramic is described. In the perovskite phase, U, Th, Sr, Zr and Mn, are shown to substitute on the Ca site with Fe partitioning between the Ca and Ti sites.