Estimation of uranium resources by life-cycle or discovery-rate models: a critique

This report was motivated primarily by M. A. Lieberman's ''United States Uranium Resources: An Analysis of Historical Data'' (Science, April 30). His conclusion that only 87,000 tons of U/sub 3/O/sub 8/ resources recoverable at a forward cost of $8/lb remain to be discovered is criticized. It is shown that there is no theoretical basis for selecting the exponential or any other function for the discovery rate. Some of the economic (productivity, inflation) and data issues involved in the analysis of undiscovered, recoverable U/sub 3/O/sub 8/ resources on discovery rates of $8 reserves are discussed. The problem of the ratio of undiscovered $30 resources to undiscovered $8 resources is considered. It is concluded that: all methods for the estimation of unknown resources must employ a model of some form of the endowment-exploration-production complex, but every model is a simplification of the real world, and every estimate is intrinsically uncertain. The life-cycle model is useless for the appraisal of undiscovered, recoverable U/sub 3/O/sub 8/, and the discovery rate model underestimates these resources. (DLC)