Compatibility/Stability Issues in the Use of Nitride Kernels in LWR TRISO Fuel

Armstrong, Beth L¹  Besmann, Theodore M¹ 

[1] ORNL

关键词: DESIGN;    DIFFUSION;    FISSION PRODUCTS;    FUEL PARTICLES;    GAS COOLED REACTORS;    KERNELS;    KINETICS;    NITRIDATION;    NITRIDES;    NITROGEN;    PYROLYTIC CARBON;    SILICON;    STABILITY;    TRANSPORT;   

DOI  :  10.2172/1038807
RP-ID  :  ORNL/TM-2012/30
PID  :  OSTI ID: 1038807
Others  :  Other: AF5810000
Others  :  NEAF278
Others  :  TRN: US1202114

美国|英语

来源: SciTech Connect

【 摘 要 】

The stability of the SiC layer in the presence of free nitrogen will be dependent upon the operating temperatures and resulting nitrogen pressures whether it is at High Temperature Gas-Cooled Reactor (HTGR) temperatures of 1000-1400 C (coolant design dependent) or LWR temperatures that range from 500-700 C. Although nitrogen released in fissioning will form fission product nitrides, there will remain an overpressure of nitrogen of some magnitude. The nitrogen can be speculated to transport through the inner pyrolytic carbon layer and contact the SiC layer. The SiC layer may be envisioned to fail due to resulting nitridation at the elevated temperatures. However, it is believed that these issues are particularly avoided in the LWR application. Lower temperatures will result in significantly lower nitrogen pressures. Lower temperatures will also substantially reduce nitrogen diffusion rates through the layers and nitriding kinetics. Kinetics calculations were performed using an expression for nitriding silicon. In order to further address these concerns, experiments were run with surrogate fuel particles under simulated operating conditions to determine the resulting phase formation at 700 and 1400 C.