Advancements in the Nuclear Criticality Slide Rule: Phase 6 Highlights and Applications

ASNR (France), LLNL (USA), and ORNL (USA) initiated a long-term collaboration in 2015 to update the Nuclear Criticality Slide Rule, a key tool for emergency response during nuclear criticality accidents. The Slide Rule allows for estimating neutron and gamma dose rates and integrated doses, based on estimated fission yields, as a function of distance from the fission source and time after the criticality accident for different critical systems. This collaboration has led to extensive updates since its inception. This paper provides a comprehensive summary of previous efforts on the Slide Rule updates and focuses on recent advancements achieved during Phase 6 of the project. Key highlights include updated computational methodologies for plutonium systems, incorporating five configurations with varying hydrogen-to-plutonium ratios. Sensitivity studies have evaluated the impact of shielding materials, air humidity, ground composition, and skyshine effects on radiation dose estimations. Additionally, developing a modern, user-friendly application for handheld devices marks a significant milestone in the evolution of the Slide-Rule. Designed to replace the existing tool, this application facilitates real-time access to dose calculations, shielding effects, and the capability to calculate the number of fissions, leveraging interactive visualizations and enhanced data interpolation. By consolidating previous findings and presenting new insights from Phase 6, this paper aims to strengthen the Slide Rule’s utility for criticality safety professionals and emergency response teams worldwide. Moreover, this work has enabled the integration of all results into an updated report, offering a unified reference for assessing radiation impacts and guiding actions during criticality emergencies.