Reassessing the Origins and Contemporary Relevance of ck Acceptability Parameters Given Evolving Perspectives on Similarity

Sensitivity and uncertainty analyses applied to nuclear criticality safety validation introduce methods to address challenges in defining and extending the areas of applicability. These areas are traditionally defined by the bounds or limits on key parameters but establishing valid ranges and managing complex parameter variations remain challenging. The introduction of ck and other integral indices, along with concepts such as the completeness of benchmark coverage, could better quantify system similarities. This work investigates these foundational concepts to ensure that the bounds remain effective in guiding the assessment of similarity and applicability in modern applications. These concepts are examples of the initial ideas that have been established and are currently implemented in SCALE codes, although their effectiveness in practice may not be fully understood. Advancements in scripting tools, coupled with the speed and efficiency of modern computing and statistical models, now allow for faster and more thorough assessments than previously possible. These advancements also enable the identification of trends within the data, providing additional insight into system behavior and broadening the scope of previous benchmarks. This study revisits and expands the scope of these foundational methods to determine whether the necessary elements for robust similarity evaluation are already embedded, partially realized, or remain unused.