Abstract The in-box Loss of Coolant Accident (LOCA) scenario is considered as one of the most affecting safety concerns for the Water-Cooled Lead Lithium Breeding Blanket (WCLL-BB) modules of the DEMOnstration (DEMO) reactor, which is sequentially followed by a multi-phase multi-component physical and chemical interaction. Therefore, the transient behavior of such accidents has to be carefully investigated during the design phase of the plant, to evaluate the consequences and to adopt the necessary mitigating countermeasures. This also requires a numerical predictive tool, which is capable to model such transients and predict the relevant phenomena under an operational condition and the connected safety parameters i.e. system pressure, temperature, chemical products mass, and volume fractions of all the existing components. Consequently, the SIMMER-III code was firstly improved at the University of Pisa by implementing the chemical reaction between PbLi eutectic alloy and water. In addition to this, an experimental campaign and a test-matrix have been recently designed according to the LIFUS5/Mod3 facility to perform a series of experiments and code post-test analyses. In the present work, the experimental data of the first LIFUS5/Mod3 test is used for the validation of the chemical model implemented in SIMMER-III through a comprehensive sensitivity study. The applied methodology for the code validation is based on a three-step procedure including qualitative analysis, quantitative analysis and the results from sensitivity analyses. The qualitative accuracy evaluation is performed through a systematic comparison between experimental and calculated time trends based on the engineering analysis, the resulting sequence of main events and the identification of phenomenological windows and of relevant thermo-hydraulic aspects. Afterwards, the accuracy of the code prediction is evaluated from a quantitative point of view by means of selected, widely used, figures of merit. Finally, the results from the sensitivity cases are analysed and quantified, to determine the effects of the most influencing code input options and transient parameters. Furthermore, the analysis is followed by applying the Fast Fourier Transform Method (FFTM) to the experimental signals and all the sensitivity calculations. The comparison shows a very good agreement for pressure transient between the experimental and numerical data, while for the temperature and the hydrogen production the results fall into acceptable criteria, which means that the code is reliable in capturing and predicting the transient values but not perfectly match with the experimental signals.

中文翻译：

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LIFUS5/Mod3 工具的测试 D1.1 分析，用于 WCLL-BB 中的盒内 LOCA

摘要 箱内冷却剂损失事故 (LOCA) 情景被认为是对 DEMOnstration (DEMO) 反应堆水冷铅锂增殖毯 (WCLL-BB) 模块影响最大的安全问题之一。由多相多组分物理和化学相互作用。因此，必须在电厂设计阶段仔细调查此类事故的瞬态行为，评估后果并采取必要的缓解措施。这还需要一个数值预测工具，该工具能够对此类瞬变进行建模并预测操作条件下的相关现象以及相关的安全参数，即系统压力、温度、化学产品质量和所有现有组件的体积分数。最后，SIMMER-III 代码首先在比萨大学通过实现 PbLi 共晶合金与水之间的化学反应进行改进。除此之外，最近根据 LIFUS5/Mod3 设施设计了一个实验活动和一个测试矩阵，以执行一系列实验和代码后测试分析。在目前的工作中，第一个 LIFUS5/Mod3 测试的实验数据用于通过全面的敏感性研究验证 SIMMER-III 中实施的化学模型。代码验证的应用方法基于三步程序，包括定性分析、定量分析和敏感性分析的结果。定性精度评估是通过基于工程分析的实验和计算时间趋势之间的系统比较来进行的，主要事件的结果序列以及现象学窗口和相关热工水力方面的识别。然后，通过选择的、广泛使用的品质因数从定量的角度评估代码预测的准确性。最后，对敏感性情况的结果进行分析和量化，以确定影响最大的代码输入选项和瞬态参数的影响。此外，分析之后将快速傅立叶变换方法 (FFTM) 应用于实验信号和所有灵敏度计算。