Keeping Score: An Actuarial Approach to Zero-Infinity Dilemmas

Abstract

A "zero-infinity dilemma", where there is presumed to be a very low ("nearly zero") probability of a very high ("nearly infinite") cost, is the least tractible yet most important type of risk problem associated with evaluating prospective energy alternatives. The term has often been used to describe the nature of the risk associated with nuclear power and many of the best known examples have been drawn from this field, but this type of risk problem is associated with the other main energy alternatives as well. In the incomplete combustion of fossil fuels, for just one example, large scale release of aromatic hydrocarbons poses another zero-infinity dilemma, with the risk of cancer and mutation. The obvious difficulty in dealing with zero-infinity dilemmas is that there is little or no direct historical record to develop probability estimates based upon frequency. By way of illustration, in its summary the Rasmussen report predicts that there is a one in five billion chance, per reactor year, of a catastrophic core meltdown. But the direct historical record of so many hundred reactor years with no meltdown is not greatly reassuring. This negative information, however welcome, is compatible with a one in a thousand chance of catastrophic meltdown as well as the one-in-five-billion Rasmussen estimate. The actuarial record, taken in simple terms of meltdowns per reactor year, is far too short to discriminate between the two. Nor do we want to wait for a long record of history of reactor years in order to develop an estimate of the probability of meltdown. On the contrary, we need the estimate of probability before a large scale program is undertaken, in order to decide upon the safety features and the scale of the program.

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