Development of SiC encapsulation for thulium oxide targets as potential nuclear batteries

Abstract

The design, fabrication and properties of encapsulations for radioisotope fuel targets (¹⁶⁹Tm) were assessed. Elemental analysis and phase identification by X-ray Fluorescence and X-ray Diffraction showed a SiC encapsulation of a thulium oxide ceramic. Microhardness testing of the encapsulation showed a relatively consistent hardness of 32.2 ± 4.7 GPa across the vertices and walls, with a mid-plane join hardness of 30.1 ± 5.4 GPa. Manufacturing tolerances followed a normal distribution with a standard deviation (σ) of σ _OD = ± 0.014 mm and σ_ID = ± 0.037 mm for Tm₂O₃ and SiC. The design of the target emphasizes robust, radiation-tolerant, high-strength SiC, but heat transfer is likely axially asymmetric because contact between Tm₂O₃-SiC is limited. Tm₂O₃-SiC chemical compatibility testing was investigated, indicating a possible reaction-limited process below 1873 K, and a possible diffusion-limited process above 1873 K. At higher temperatures, thulium containment for this concept is limited by chemical compatibility.