Generalized formula for the dose-distance curve to inform emergency planning zone distances

Establishing emergency planning zones requires an understanding of the relationship between radiation dose and distance from the power plant, commonly represented as a dose-distance (D D) curve. Given the vast number of potential accident scenarios and meteorological conditions, simple equations that enable rapid computations while preserving the physical interpretation of D D correlations are highly desirable. Previous studies have generally relied either on “rule-of-thumb” formulas, which offer high interpretability but have limited or poorly defined ranges of applicability, or on detailed case-specific calculations using computer codes. Therefore, this study proposes a generalized formula for the D D curve that is applicable across a wide range of conditions, enables rapid calculation, and provides a clear physical interpretation of the dose-distance relationship. In the formulation, the effective dose is expressed as a combination of nuclide- and distance-dependent components. The proposed function was validated by analyzing nuclide and exposure pathway contributions to dose across a wide range of accident scenarios, thereby demonstrating the robustness of the underlying assumptions. Furthermore, the discrepancy between the proposed function and conventional calculations was quantitively shown to be negligible relative to the uncertainties associated with accident and meteorological scenarios. Model analysis further demonstrated that the generalized formula for the D D curve can be applied under various meteorological conditions and that previously proposed rule-of-thumb correlations represent special cases of the proposed function. The proposed generalized formula for the D D curve enables rapid estimation and mechanistic analysis, making it a valuable tool for emergency preparedness and response.