This paper presents the verification and validation (V&V) of a calculation module for isotope inventory prediction to control the back-end cycle of spent nuclear fuel (SNF). The calculation method presented herein was implemented in a two-step code system of a lattice code STREAM and a nodal diffusion code RAST-K. STREAM generates a cross section and provides the number density information using branch/history depletion branch calculations, whereas RAST-K supplies the power history and three history indices (boron concentration, moderator temperature, and fuel temperature). As its primary feature, this method can directly consider three-dimensional core simulation conditions using history indices of the operating conditions. Therefore, this method reduces the computation time by avoiding a recalculation of the fuel depletion. The module for isotope inventory calculates the number densities using the Lagrange interpolation method and power history correction factors, which are applied to correct the effects of the decay and fission products generated at different power levels. To assess the reliability of the developed code system for back-end cycle analysis, validation study was performed with 58 measured samples of pressurized water reactor (PWR) SNF, and code-to-code comparison was conducted with STREAM-SNF, HELIOS-1.6 and SCALE 5.1. The V&V results presented that the developed code system can provide reasonable results with comparable confidence intervals. As a result, this paper successfully demonstrates that the isotope inventory prediction code system can be used for spent nuclear fuel analysis.

本文介绍了同位素库存预测计算模块的验证和验证 (V&V)，以控制乏核燃料 (SNF) 的后端循环。本文提出的计算方法是在格码 STREAM 和节点扩散码 RAST-K 的两步码系统中实现的。STREAM 生成横截面并使用分支/历史消耗分支计算提供数密度信息，而 RAST-K 提供功率历史和三个历史指数（硼浓度、慢化剂温度和燃料温度）。作为其主要特征，该方法可以使用操作条件的历史指数直接考虑三维岩心模拟条件。因此，该方法通过避免重新计算燃料消耗来减少计算时间。同位素清单模块使用拉格朗日插值法和功率历史校正因子计算数密度，用于校正在不同功率水平下产生的衰变和裂变产物的影响。为了评估用于后端循环分析的开发代码系统的可靠性，对 58 个压水反应堆 (PWR) SNF 测量样本进行了验证研究，并使用 STREAM-SNF、HELIOS-1.6 进行了代码到代码比较和规模 5.1。V&V 结果表明，开发的代码系统可以提供具有可比置信区间的合理结果。因此，本文成功地证明了同位素存量预测代码系统可用于乏核燃料分析。