A Probabilistic Risk Assessment for the K-65 silos at the Feed Materials Production Center (FMPC)

This study is intended to provide a general perspective of the overall risk assessment and to facilitate the understanding and relationship between the different phases of the study. The overall risk assessment embodied the potential for failure of the silos, the release and transport of contaminated material, the eventual exposure and dose, and finally the risk. The risk aspect of the study covers several different areas: (1) the probability of silo failure coupled the consequences of the failure (such as release), (2) the potential for wide spread contamination, and (3) the consequences of exposure and dose such as the possibility of latent cancer incidence. The accepted risk level from exposure to some quantity of radioactive material is not directly comparable to accepted risk levels for structural failure. In order to make a comparison the risks must be based on the same outcome. The results of this risk assessment clearly show that the total risks for the scenarios considered indicate the significance of the threat of release and exposure from the material in the K-65 silos. The chronic radon emission and the potential for the acute release of the radon contained in the head space are probably the more important since the likelihood of these events is either one or close to one. The acute release of residue material has a sufficiently small probability of occurrence that the risk can be considered to be the lesser of the three scenarios. The risks posed by the other radionuclides (radon daughters) were found to result in sufficiently low doses that the scenarios could be eliminated. 20 refs., 37 figs., 62 tabs