The mechanical response of a nuclear-grade silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composite was investigated under mechanical loading conditions mimicking the pellet-cladding mechanical interaction (PCMI) phase of a reactivity-initiated accident (RIA). In a RIA, cladding deformation and failure can be induced by the rapid thermal expansion of the nuclear fuel. A pulse-controlled modified-burst test was used to investigate RIA-like PCMI scenarios on SiC/SiC composite samples at pulse widths from 12 to 100 ms.

The strain-driven nature of the cladding sample deformation was due to the rapid internal pressurization and subsequent expansion of a secondary tube. A digital-image correlation technique was used to measure strains from the speckle-painted outer surface of the tubes. The failure strains of samples tested at slower rates, such as RIA event durations of 52 and 100 ms, showed good agreement with the literature-reported values for similar composites tested at slow strain rates. Additionally, the failure strain showed good agreement with reference expansion-due-to-compression tests at slow strain rate. However, a decrease in the failure strain was determined for the fast-rate (12 ms) tests. This indicated that the failure strain of these composites might be influenced by the strain rate during RIA-like events. The failure strains observed in the tests corresponded to local energy depositions of approximately 50 cal/g UO₂ from hot zero power, with an initial condition of pellet–cladding gap closure prior to the event. In-pile transient testing of these concepts that would result in hoop strain due to PCMI in the range of 0.5–1.0% is recommended.

在模拟反应性事故（RIA）的颗粒-包覆机械相互作用（PCMI）相的机械负载条件下，研究了核级碳化硅纤维增强的碳化硅基复合材料（SiC / SiC）的机械响应。在RIA中，核燃料的快速热膨胀会引起包层变形和破坏。使用脉冲控制的修正突发测试来研究脉冲宽度为12到100 ms的SiC / SiC复合材料样品上类似RIA的PCMI方案。

包层样品变形的应变驱动性质是由于快速的内部增压和随后的二次管膨胀所致。使用数字图像相关技术来测量来自散布有斑点的管子外表面的应变。以较低速率（例如52和100 ms的RIA事件持续时间）测试的样品的破坏应变与以慢应变速率测试的类似复合材料的文献报道值显示出很好的一致性。此外，在缓慢应变速率下，破坏应变与参考膨胀压缩试验具有很好的一致性。但是，对于快速（12 ms）测试，确定了失效应变的降低。这表明这些复合材料的破坏应变可能会受到类似RIA的事件中的应变速率的影响。₂从热零功率开始，在事件发生之前初始条件是颗粒-包层间隙闭合。建议对这些概念进行桩内瞬态测试，由于PCMI在0.5–1.0％的范围内，这会导致箍紧应变。