Uncertainty Analysis and Model Validation for a Retrospective Assessment of Thyroid Dose Resulting from Atomic Weapons’ Test Fallout

Abstract

Modeling internal dose resulting from environmental transport of atomic weapons’ test fallout from the Nevada Test Site (NTS) USA, during the period 1951–1962, requires estimates of many important parameters for which little data exists. A retrospective dose assessment study for which model reliability is of great importance is now nearing completion. The study’s objectives are to estimate thyroid dose from ingestion of radioiodine in milk and vegetables to a cohort of over 3000 persons. The cohort that had potentially been exposed to NTS fallout were examined for thyroid abnormalities during 1965 and 1985. Model sensitivity analysis and parameter uncertainties were used to help establish priorities for research and uncertainty analysis. Numerous parameters were shown to substantially affect radioiodine concentrations in milk and uncertainty estimates, the most significant being the fraction of fallout intercepted by vegetation and the relative timing of dairy management practices and deposition events. Both parameters were subsequently researched and the results are discussed. Verification of model reliability was attempted by comparing predictions with limited literature data.