A quantitative assessment of the 131 I activity in RBMK coolant as a function of the number of defective fuel pins and the distribution over a fuel run is presented. The 131 I yield fraction is determined using a model based on the solution of the diffusion equation with empirical coefficients. This investigation was performed for a core-average FA whose power is a function of the burnup. It is shown that in order to prevent the number of defective fuel pins from exceeding a limit it is not enough to take into account their uniform distribution over a run because the burnup strongly impacts the activity and egress of 131 I to beneath the fuel-pin cladding and into the coolant.

中文翻译：

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RBMK 冷却液中碘活度限值与缺陷燃料棒数量的相互关系

RBMK 冷却剂中 131 I 活性的定量评估作为有缺陷的燃料细棒数量和燃料运行中的分布的函数。使用基于具有经验系数的扩散方程的解的模型来确定 131 I 产率分数。这项研究是针对核心平均 FA 进行的，其功率是燃耗的函数。结果表明，为了防止有缺陷的燃料棒的数量超过限制，仅仅考虑它们在运行中的均匀分布是不够的，因为燃耗强烈影响 131 I 到燃料棒下方的活动和出口包层并进入冷却剂。