A quantitative uncertainty analysis for the assessment of risk associated with radionuclide releases from the K-1435 incinerator at Oak Ridge, TN : human inhalation pathway analysis

The objective of this study is to perform a quantitative uncertainty and sensitivity analysis of the dose and risk to the maximally exposed individual from the inhalation of radionuclides emitted from the K-1435 TSCA incinerator located at the DOE K-25 facility in Oak Ridge, TN. Dose and risk estimates are computed from monthly stack emissions data beginning in 1990 when the incinerator went into operation and continuing through August, 1994. A gaussian plume dispersion model is used to obtain radionuclide concentrations from the emissions data, and an inhalation pathway analysis is performed. Probability density functions are assigned for each of the risk model parameters. Monte Carlo methods are applied to propagate the parameter distributions, and a confidence interval is determined for the computed dose and risk estimates. The results of the uncertainty analysis indicate that the estimated cancer risk varies about one and one-half orders of magnitude for the 90 percent confidence interval. More specifically, the chance of cancer incidence due to inhalation of radionuclides ranges from 2 in ten million at the 5 percent confidence level to 9 in a million at the 95 percent confidence level. The EPA deterministic method yielded an estimated risk in the lower quartile of the uncertainty analysis range, and the ICRP deterministic methods yielded an estimated risk in the upper quartile of the uncertainty range. The deterministic computations indicate that the revised EPA slope factors estimate more than a factor of 5 lower cancer risk due to inhalation of radionuclides as compared to the ICRP methodology which uses dose and risk factors.