The US NRC system code TRACE has been modified at PSI for application to liquid- metal-cooled reactor. An unprotected loss-of-flow-without-scram test performed at the Fast Flux Test Facility (FFTF) provides an opportunity to enhance the validation base of TRACE to transient analysis for sodium-cooled fast reactor (SFR). The FFTF primary system model was created with TRACE and initial core flow distribution and pressure drop in each segment of primary loop were reproduced using available data. In addition, a full-core model was built with the Serpent-2 Monte Carlo code to compute reactivity feedback parameters and delayed neutron information for point kinetics model in TRACE. Transient movement of sodium free level in Gas Expansion Modules (GEM) which was designed as a passive safety device of FFTF was simulated with TRACE using a level tracking model. A good agreement between measured and calculated total reactivity indicated a reasonable validity of modeling of feedback effects and of predicted sodium level in GEM. Multi-dimensional thermal-hydraulics effects in the FFTF vessel especially thermal stratification phenomenon which was directly related to natural circulation flow rate in primary loop were simulated with three three-dimensional VESSEL components in TRACE. Transient evolution of sodium temperatures at the Post-Irradiation Open Test Assembly (PIOTA) outlet was predicted in a good agreement with the measurements. The need of a more accurate thermal–hydraulic simulation of the inter-assembly gaps corresponding to the fuel region was discovered to obviously improve the estimation of inter-assembly heat transfer. This study represented an important step towards the validation of the TRACE code to SFR and some suggestions for further development work are proposed.

美国 NRC 系统代码 TRACE 已在 PSI 进行修改，以应用于液态金属冷却反应堆。在快通量测试设施 (FFTF) 进行的无保护流量损失测试提供了一个机会，可以增强 TRACE 对钠冷快堆 (SFR) 瞬态分析的验证基础。FFTF 主系统模型是使用 TRACE 创建的，初始核心流量分布和主回路每个段中的压降是使用可用数据再现的。此外，还使用 ​​Serpent-2 Monte Carlo 代码构建了一个全核模型，以计算 TRACE 中点动力学模型的反应性反馈参数和延迟中子信息。气体膨胀模块 (GEM) 中无钠水平的瞬态运动被设计为 FFTF 的被动安全装置，使用水平跟踪模型通过 TRACE 进行模拟。测量的和计算的总反应性之间的良好一致性表明 GEM 中反馈效应和预测的钠水平建模的合理有效性。利用TRACE中的三个三维VESSEL组件模拟FFTF容器中的多维热工水力效应，特别是与主回路自然循环流量直接相关的热分层现象。辐照后开放测试组件 (PIOTA) 出口处钠温度的瞬态演变与测量结果非常吻合。发现需要对对应于燃料区域的组件间间隙进行更准确的热-水力模拟，以显着改善组件间传热的估计。这项研究代表了向 SFR 验证 TRACE 代码迈出的重要一步，并提出了一些进一步开发工作的建议。