The use of U<sub>3</sub>Si<sub>2</sub>/Al dispersion fuel for high power research reactors

In order to investigate the irradiation performance of U3Si2/Al dispersion fuel at relatively aggressive reactor conditions, compared to how this fuel is typically used in a research or test reactor, post irradiation examination was performed on two fuel plates that were irradiated at ∼270 W/cm2 average surface heat flux and to a maximum local burnup greater than 8 × 1021 fissions/cm3 in the Advanced Test Reactor as part of the RERTR-8 experiment. As part of the non-destructive examinations that were performed on both fuel plates, detailed thickness measurements using a high-fidelity measurement bench were performed on one fuel plate and a segment of the second fuel plate. This paper provides the first reported results of such high-resolution thickness measurements for U3Si2/Al dispersion fuel plates, containing primarily the U3Si2 fuel phase, irradiated at such power levels to high burnup. For destructive examination using optical metallography, samples were generated from both irradiated plates. Localized regions of high swelling (characteristic of internal blistering) were observed on the surface of both fuel plates, suggesting that the performance limits had been reached for each plate. Destructive examinations showed that the fuel particles that are primarily U3Si2, which become amorphous during irradiation, in both plates contained relatively large fission gas bubbles with evidence of fission gas bubble interconnection.

为了研究U₃Si₂/Al弥散燃料在相较于其在研究堆或试验堆中通常使用条件更为严苛的反应堆条件下的辐照性能，作为RERTR - 8实验的一部分，对在先进试验堆中以约270 W/cm²的平均表面热通量辐照且最大局部燃耗大于8×10²¹裂变/cm³的两块燃料板进行了辐照后检验。作为对两块燃料板进行的无损检测的一部分，使用高精度测量台对一块燃料板以及第二块燃料板的一部分进行了详细的厚度测量。本文首次报道了此类针对主要含U₃Si₂燃料相的U₃Si₂/Al弥散燃料板在如此功率水平下辐照至高燃耗的高分辨率厚度测量结果。对于使用光学金相学进行的破坏性检验，从两块辐照后的燃料板上都制备了样品。在两块燃料板的表面都观察到了局部高肿胀区域（内部起泡的特征），这表明每块板都已达到性能极限。破坏性检验表明，两块板中主要为U₃Si₂且在辐照过程中变为非晶态的燃料颗粒都含有相对较大的裂变气泡，且有裂变气泡相互连接的迹象。