should be included. In fashioning a rule, therefore, the question is not whether to generalize, but how much over- and underinclusiveness to tolerate as the cost of simplicity. Like all rules, an inherent part of the definitions of HLW and TRU waste is that they are under- and overinclusive with respect to particular waste streams.

For example, the definition of TRU and the consequent requirement of permanent geological disposal may be overinclusive with respect to some buried TRU waste in very arid and controlled environments where radionuclide migration is expected to be small as a result of the absence of water and intrusion not being expected because of institutional controls and minimal pressures from human activities. Conversely, it may be underinclusive, at least with respect to human health risk, as compared to high-activity, long-lived low-level wastes. An example might be the waste storage silos at Fernald, in which radon-226 levels exceed 100 nanocuries per gram (nCi/g). The so-called K-65 waste resulted from processing of exceptionally rich uranium ore that was obtained during and very shortly after the Second World War. Although radium is not transuranic, the K-65 wastes produce a substantial external dose due to gamma-ray emission and the risks they pose may even exceed those posed by some transuranic wastes and are at least similar based on the intrinsic toxicity of the isotopes involved.

Under- and overinclusiveness are in the nature of all rules of general applicability. The drafters of general rules are rarely able to anticipate all of the circumstances to which they will apply, and new circumstances often appear that make previous assumptions obsolete. Moreover, general rules often build in under- or overinclusiveness as a way of making a point of principle or as a means of simplifying administration of and compliance with the rule. The question, therefore, when over- or under-inclusiveness is found is not how to eliminate it, but how to manage it.

There are two decision points that create the inflexibility in management of HLW and TRU waste. The first is the classification decision, in which the waste products of certain processes and materials with certain atomic composition are automatically designated HLW and TRU waste, respectively, with little or no real opportunity for adjustment based on other factors, such as risk or hazard. The second is the disposal decision, about which the legal structure is extremely prescriptive: if the waste is classified as HLW or TRU waste, it must be disposed in a geologic repository unless, in the case of TRU waste,