Report on waterproofing of UN studies
Fuels with high uranium densities have been considered in the Nuclear Technology Research and Development program’s Advanced Fuels Campaign as potential replacements for uranium(IV) oxide in commercial light water reactors. One such candidate fuel is uranium mononitride, UN, which has been observed to readily oxidize in steam and simulated pressurized water reactor conditions. Thus, it is important to examine methods for waterproofing UN, especially for potential cladding breach scenarios. This can be achieved by controlling the microstructure so as to prevent contact between the UN fuel and coolant. Research highlighted in this L2 milestone has focused on screening potential candidate additive materials to control UN microstructure using steam oxidation TGA. From these candidates, silicon (Si), chromium (Cr), and silicon carbide (SiC) were selected based on corrosion resistance, which led to attempts to develop a method for compositing these materials with UN. Powders of these materials were mixed with UN, pressed, and sintered. UN-metal composite sintering was attempted through liquid-phase sintering at temperatures above the melting point of the respective metals, while the UN-SiC composite sintering was attempted using two-step sintering at 2100 and 2050 °C. Results of silicon and silicon carbide appeared to show chemical interaction with UN to form uranium silicides, while chromium was found to significantly volatilize near the melting point of chromium. No indication of densification was observed. These observations, along with those of the preceding, related L3 milestone (NTRD-M3FT-19LA020201024) were used to develop a better understanding of microstructure control to advance efforts for UN waterproofing.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1565797
- Report Number(s):
- LA-UR-19-28422-Rev.1
- Country of Publication:
- United States
- Language:
- English
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