Prismatic dislocation loops are the primary manifestation of radiation damage in crystals, and contribute to the phenomenon of radiation embrittlement. This undesirable effect, most serious for materials used in high-dose environments such as next-generation fission and future fusion reactors, results from the strong interaction between gliding dislocations, the carriers of plasticity, with the population of radiation-induced prismatic loops. Ferritic-martensitic steels, the most promising candidate materials for future high-dose applications, are based on iron, and are known to become highly elastically-anisotropic at the high temperatures (>500 degrees centigrade) at which they must operate.