Pyroprocessing of spent nuclear fuels is an electrochemical separation method where spent metallic fuel is dissolved in a molten salt bath to allow uranium (U) and plutonium (Pu) to be isolated from fission products (FPs) and other impurities. This allows the useful materials to be reused in mixed oxide fuel (MO_x) or further refined to new reactor fuel. Monitoring the changing concentrations of U, Pu, FPs and other species inside a molten salt vessel presents a unique challenge which laser-induced breakdown spectroscopy (LIBS) may be able to overcome, due to its ability to simultaneously analyse multiple elements using a single measurement with stand-off capability in situ. In this study, samples of praseodymium (Pr), holmium (Ho) and erbium (Er) chloride (LnCl₃) in LiCl + KCl eutectic (LKE) salt were analysed with LIBS. Multiple laser pulse energies were tested to maximise the signal to background ratio, the best results were obtained at the lowest pulse energy of 85 mJ per pulse. Forward interval Partial Least Squares (iPLS) regression was used to create predicted versus measured concentration models for each element. This method achieved Root Mean Squared Error of Cross Validation (RMSECV) values of between 3.20 × 10⁻³ and 16.3 × 10⁻³ mmol_Ln g_LKE⁻¹ for single lanthanide samples and 2.84 × 10⁻³ and 7.62 × 10⁻³ mmol_Ln g_LKE⁻¹ for mixed samples of all three lanthanide elements. Limits of quantification of between 1000 and 9000 ppm suggest LIBS should be a candidate for on-line analysis of elemental concentrations during pyroprocessing.

中文翻译：

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使用激光诱导击穿光谱技术定量预测盐基中稀土元素的浓度，用于熔融盐反应器和热解

乏核燃料的热解处理是一种电化学分离方法，其中，将废金属燃料溶解在熔融盐浴中，以使铀（U）和p（Pu）与裂变产物（FPs）和其他杂质分离。这允许将有用的材料重新用于混合氧化物燃料（MO _x），或进一步提炼为新的反应堆燃料。监测熔融盐容器中U，Pu，FPs和其他物质的浓度变化提出了一个独特的挑战，激光诱导击穿光谱法（LIBS）可以克服这一挑战，因为它能够通过一次测量同时分析多种元素具有原位防脱能力。在这项研究中，samples（Pr），（Ho）和氯化er（Er）（LnCl ₃用LIBS分析LiCl + KCl共晶（LKE）盐中的）。测试了多个激光脉冲能量以最大化信噪比，在最低脉冲能量（每个脉冲85 mJ）下获得了最佳结果。使用正向区间偏最小二乘（iPLS）回归来创建每个元素的预测浓度模型与测量浓度模型。此方法对单个镧系元素样品的交叉验证均方根误差（RMSECV）值在3.20×10 ^-3和16.3×10 ^-3 mmol _Ln g _LKE ^-1之间，而在2.84×10 ^-3和7.62×10 ^-3 mmol之间_Ln g _LKE ^-1用于所有三种镧系元素的混合样品。定量限在1000至9000 ppm之间表明LIBS应该是热加工过程中元素浓度在线分析的候选者。